JPH10143893A - Objective lens driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the sliding characteristic and dimensional accuracy of a bearing part and to suppress the inclination of an objective lens by using molded goods contg. specific wt.% of the whiskers of potassium titanate into an unsatd. polyester resin as an additive for the bearing part. SOLUTION: The central part of a lens holder 3 for holding the objective lens 2 is provided with a hole 3a for a bearing. The bearing part 12 of a hollow cylindrical shape is fixed by an adhesive into this hole 3a for the bearing and a supporting shaft 5 is inserted therein to hold support the lens holder 3. As a result, the lens holder 3 is made turnable around the supporting shaft 5 as a center and movable in the supporting shaft direction. At this time, the lens holder 3 is formed of a high-elasticity resin which is formed by reinforcing a polyphenylene sulfide with carbon fibers, etc. The bearing part 2 is formed by using the BMC(bulk molding compd.) molded goods contg. 5 to 30wt.% whiskers of the potassium titanate in the unsatd. polyester resin, by which the hysteresis thereof is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an objective lens driving device.

[0002]

2. Description of the Related Art Conventionally, in an optical disk apparatus or the like as an optical recording / reproducing apparatus, in order to write an information signal on a disk and read it, a laser beam is accurately focused on information pits of the disk. An objective lens driving device is provided. As this objective lens driving device, a so-called shaft sliding type in which a lens holder holding an objective lens is supported on a support shaft so as to be rotatable and movable along an axial direction to perform tracking and focusing on a disk. Are known.

[0003] In such a shaft-sliding type objective lens driving device, a high degree of followability to the disk surface is required, so that the slidability of the support shaft and the bearing portion into which the support shaft is inserted is extremely high. It is necessary to increase the height to obtain a desired sliding characteristic (hysteresis).

[0004] In order to satisfy such a demand, for example, in Japanese Patent Laid-Open No. 4-318335,
A proposal has been made in which the bearing portion is made of a synthetic resin material having slidability.

[0005]

In recent years, for example, in a device such as a CD-ROM, the lens holder tends to be shortened in the axial direction due to a demand for a thinner device. It has become to.

However, when the bearing portion is shortened in the axial direction, it is difficult to suppress the inclination of the bearing portion with respect to the support shaft. As a result, the objective lens is inclined with respect to the disk, and reading and writing are performed with high accuracy. It becomes impossible.

[0007] The above-mentioned problem becomes more remarkable especially in an apparatus such as a DVD, which requires a more strict inclination of an objective lens with respect to a disk with an increase in recording density.

Therefore, it is necessary to reduce the bearing gap (sliding gap) of the bearing portion with respect to the support shaft to form a minute gap to prevent the bearing portion from tilting. However, when the bearing portion is formed of a resin molded product in order to enhance the slidability as described above, it is difficult to secure the dimensional accuracy of the sliding surface, and as a result, it is difficult to suppress the inclination of the bearing portion. could not.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an objective lens driving device which satisfies both slidability and dimensional accuracy, can obtain desired sliding characteristics, and can suppress the inclination of the objective lens.

[0010]

In order to achieve the above object, the objective lens driving device according to the first aspect of the present invention is supported by the support shaft via a bearing that holds the objective lens and slides on the support shaft. In an objective lens driving device configured to rotate a lens holder around the support shaft and move the lens holder in the support shaft direction by a driving mechanism, the bearing portion may be formed by adding at least potassium titanate to an unsaturated polyester resin. It is characterized by comprising a resin molded product including

According to the objective lens driving device of the first aspect, the bearing portion is formed of a resin molded product containing at least potassium titanate as an additive in an unsaturated polyester resin. The resin molded product has a property of satisfying both slidability and dimensional accuracy.

At this time, when the addition amount of potassium titanate is set to 5% by weight to 30% by weight, both the slidability and the dimensional accuracy are more satisfied.

At this time, as the potassium titanate,
As in claim 3, potassium titanate whiskers may be employed.

Furthermore, when the lens holder is made of a highly elastic resin and the surface of the support shaft is made of a slidable resin, the elasticity of the lens holder is improved, The slidability is further improved.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 and 2 show an objective lens driving device according to an embodiment of the present invention. The objective lens driving device 1 according to the present embodiment generally includes a lens holder 3 for holding an objective lens 2 and a lens holder 3 3. A hollow cylindrical bearing 12 fixed to a bearing hole provided in 3
And a support shaft 5 inserted into the bearing 12 to support the lens holder 3.

The lens holder 3 is made of a highly elastic resin. In this embodiment, as the high elasticity resin, a resin obtained by reinforcing PPS (polyphenylene sulfide) with, for example, carbon fiber is used. For example, a liquid crystal resin, phenol, epoxy resin, or the like is reinforced with, for example, carbon fiber or the like. A resin reinforced with a filler other than carbon fiber may be used, and a resin having a high flexural modulus such as an epoxy resin or LCP may be used alone. Then, by using such a high elastic resin, the higher-order resonance frequency of the lens holder 3 can be increased to a desired level at which the speed can be increased.

A bearing hole 3a is formed substantially in the center of the lens holder 3 along the optical axis direction, and a hollow cylindrical bearing 12 is fixed to the bearing hole 3a by, for example, an adhesive. Have been. The bearing 12 is made of BMC (Bulk Molding Co., Ltd.) containing unsaturated polyester resin and at least whiskers of potassium titanate as an additive.
A molded product is used, and in this embodiment, Neurac OM-101 (addition amount of potassium titanate: 10% by weight) of Otsuka Chemical Co., Ltd. is used.

Here, the reason why a BMC molded product containing an unsaturated polyester resin containing at least whiskers of potassium titanate as an additive will be described as the bearing 12. FIG. 3 is a characteristic diagram showing the relationship between the cylindricity of the sliding surface of the bearing portion and hysteresis (sliding characteristics) for each of the typical materials constituting the bearing portion.

Hysteresis corresponding to the slidability is as follows.
The cylindricity corresponding to the dimensional accuracy is desirably 5 μm or less in order to keep the inclination of the objective lens 2 within the standard.

Here, resin moldings other than the BMC molded product (the above-mentioned Neurac OM-101) in which 10% by weight of potassium titanate whiskers are added as an additive to the unsaturated polyester resin shown on the leftmost side of the figure. No product satisfies both the hysteresis and cylindricity criteria described above.

In particular, when attention is paid to a BMC molded product which does not contain potassium titanate as an additive in the unsaturated polyester resin shown second from the left in the figure, the cylindricity is satisfied, but the hysteresis is extremely poor. The reason why the cylindricity is good is that hardening shrinkage hardly occurs due to the characteristics of the BMC, sink marks and the like do not occur at the time of molding, the undulation of the sliding surface is small, and high dimensional accuracy can be obtained. Hysteresis is poor because the sliding property of the BMC itself is low.

Therefore, in order to enhance the slidability, an appropriate amount of potassium titanate whisker was added to the unsaturated polyester resin shown on the leftmost side of the figure by using 10% by weight of potassium titanate whisker as an additive. BM containing
It is a C molded product. As is clear from the figure, both the above-mentioned criteria of hysteresis and cylindricity are satisfied. Therefore,
In the present embodiment, as the bearing 12, a BMC molded product containing an unsaturated polyester resin and at least whiskers of potassium titanate as an additive is used.

Although the addition amount of the potassium whisker of potassium titanate is set to 10% by weight, the amount is not limited to 10% by weight. If the whisker of potassium titanate is added, the hysteresis is reduced as described above. Can be improved. More preferable addition amount of potassium titanate whisker is 5
% By weight to 30% by weight.

Returning to the configuration shown in FIGS. 1 and 2 again, the support shaft 5 is inserted into the bearing 12 at the bottom of the outer yoke 9 and fixed substantially at the center. The support shaft 5 is made of SUS. In order to enhance the slidability with the bearing 12, the surface of the support shaft 5 is made of, for example, a slidable resin in which PTFE is dispersed in polyamideimide, or a weight of PTFE and acrylic. A slidable resin or the like in which molybdenum is dispersed is coated.

A balancer 6 is fixed to the lens holder 3 on the opposite side of the objective lens 2 about the support shaft 5. On the outer peripheral surface of the lens holder 3, a pair of focusing drive coils 8, 8 are symmetrically positioned with respect to the support shaft 5.
And a pair of tracking drive coils 7, 7 are fixed respectively.

The outer yoke 9 for fixing the support shaft 5 is raised so that the outer peripheral edge positioned symmetrically with respect to the support shaft 5 is bent at a right angle and faces the drive coils 7 and 8, respectively. , In each of the rising parts,
A pair of magnets 1 facing the drive coils 7 and 8
0 and 10 are respectively fixed. This magnet 1
0 is a focusing magnet 10b facing the focusing drive coil 8, a tracking magnet 10a facing the tracking drive coil 7,
Consists of The focusing magnet 10b is polarized and magnetized so that the N and S poles are arranged in the direction of the support axis, while the tracking magnet 10a is polarized and magnetized so that the N and S poles are arranged in the circumferential direction.

On the bottom of the outer yoke 9, the inner yoke 1
1 is attached to the outer yoke 9 so as to overlap with the outer yoke 9. An outer peripheral edge of the inner yoke 11, which is located symmetrically with respect to the support shaft 5, and which is located inside the drive coils 7, 8. The peripheral edges are each bent at a right angle so as to be inserted into an opening provided in the lens holder 3 and stand up. As described above, the inner yoke 11, the drive coils 7, 8, the magnet 10, and the outer yoke 9 are arranged at symmetrical positions around the support shaft 5 in order from the inside, and a substantially closed magnetic path passing through these is formed. Configuration.

The portion of the inner yoke 11 facing the tracking drive coil 7 may not be provided, and the inner yoke 11 itself may not be provided.

Then, the focusing driving coil 8,
8, a predetermined driving current is caused to flow, a thrust is generated by the driving current and the magnetic flux in the magnetic circuit, and the lens holder 3 moves in the optical axis direction (along the support shaft 5) to perform a focusing operation. When a predetermined drive current is supplied to the tracking drive coils 7 and 7, a thrust is generated by the drive current and the magnetic flux in the magnetic circuit, and the lens holder 3 swings about the support shaft 5. Movement, that is, a tracking operation is performed by moving in the tracking direction.

At this time, the lens holder 3 moves via the bearing 12 having improved slidability with respect to the support shaft 5 having improved slidability, so that the movement is quickly and smoothly performed. You. At this time, since the dimensional accuracy of the sliding surface of the bearing 12 is ensured as high as desired, the inclination of the objective lens 2 with respect to the disk surface is suppressed, and reading and writing are performed with high accuracy.

As described above, in the present embodiment, the bearing 12 is formed of a resin molded product containing at least potassium titanate as an additive in an unsaturated polyester resin. According to the characteristics of the product, both the slidability and the dimensional accuracy of the bearing 12 can be satisfied, and it is possible to obtain desired sliding characteristics and to suppress the inclination of the objective lens 2. I have.

Since the lens holder 3 is made of a highly elastic resin and the surface of the support shaft 5 is made of a slidable resin, the elasticity of the lens holder 3 can be improved, It is possible to increase the resonance frequency to a desired level at which high speed can be achieved, and it is possible to further improve the slidability and obtain more desired sliding characteristics.

When the axial length of the bearing 12 is about 3 mm, the difference between the bearing 12 and the outer periphery of the support shaft 5 is 7 mm.
The inclination of the objective lens 2 is set to 15
It can be controlled within minutes.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments and can be variously modified without departing from the gist thereof. Needless to say, for example, in the above embodiment, the bearing 12 is fixed to the bearing hole 3a of the lens holder 3 with an adhesive, but the fixing method is not limited to this. For example, press-fitting, insert molding, double molding, or the like may be used.

The sliding gap is not limited to the above-mentioned value, but needs to be changed depending on, for example, the allowable level of the inclination of the objective lens 2. In particular, when applied to a high recording density, for example, a DVD, the value needs to be smaller than the above value.

[0036]

As described above, in the objective lens driving device according to the first aspect, the bearing portion is constituted by a resin molded product containing at least potassium titanate as an additive in an unsaturated polyester resin. It is designed to satisfy both the sliding property and dimensional accuracy of the bearing part by the characteristics of the resin molded product, so that the desired sliding property can be obtained and the inclination of the objective lens is suppressed. It becomes possible.

At this time, in the objective lens driving device according to the second aspect, the addition amount of potassium titanate is 5% by weight to 30% by weight.
Therefore, both the slidability and the dimensional accuracy can be more satisfied, and the effect of the present invention can be further enhanced.

At this time, potassium titanate whiskers can be used as the potassium titanate.

Further, the objective lens driving device of claim 4 is:
Since the lens holder is made of a highly elastic resin and the surface of the support shaft is made of a slidable resin, the elasticity of the lens holder is improved, and the slidability is further improved. The higher resonance frequency of the lens holder can be increased to a desired level at which high speed can be achieved, and more desired sliding characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view illustrating an objective lens driving device according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA in FIG.

FIG. 3 is a characteristic diagram showing a relationship between cylindricity and hysteresis of a sliding surface of a bearing unit for each material constituting the bearing unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens drive device 2 Objective lens 3 Lens holder 5 Support shaft 12 Bearing part

Claims (4)

[Claims] 1. A lens holder, which holds an objective lens and is supported by a support shaft via a bearing that slides on the support shaft, is rotated about the support shaft by a drive mechanism and is moved in the support shaft direction. The objective lens driving device according to claim 1, wherein the bearing portion is formed of a resin molded product containing at least potassium titanate as an additive in an unsaturated polyester resin. 2. The objective lens driving device according to claim 1, wherein 5 to 30% by weight of potassium titanate is added. 3. The objective lens driving device according to claim 2, wherein the potassium titanate is a potassium titanate whisker. 4. The lens holder according to claim 1, wherein a bearing portion is fixed to the lens holder, and a surface of the support shaft is formed of a slidable resin. 2. The objective lens driving device according to 1.