JPS61216136A - Objective lens driver - Google Patents

Abstract

PURPOSE:To prevent the resonance tones of a cover as well as the deterioration of sensitivity of a drive part and to increase the upper limit value of the coil allowance current, by using a monolithic cover made of a porous material to minimize the compression and expansion of air inside the cover and therefore to increase the heat dissipating effect of the coil. CONSTITUTION:A monolithic cover 1 is made of a porous sintered material and the air can pass through the cover 1 since spaces (c) exist among particles (b). However most of the dust floating in the air cannot pass through the spaces (c) and therefore the mixture of dust is prevented to the inside of the cover 1. When a drive part including an objective lens 6 and a coil 7 is moving toward the driving direction (d), the drive part functions as a so-called engine piston. Thus the air is compressed and expanded inside the cover 1. Here the cover 1 functions to reduce the compression and expansion of air since the cover itself has the permeability since it is made of a porous material.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to an objective lens drive used in a readout device of an optical disc player, etc., which irradiates a disc with a condensed light beam and reproduces a signal using the reflected light or transmitted light. It is related to the device.

2. Description of the Related Art FIG. 2 shows an example of an objective lens driving device in a conventional reading device for an optical disc player.

In this structural example, the drive section is a part in which the objective lens 6 and the coil 7 are integrated, and a slide bearing 9 is used as a guide in the drive direction d. When a drive current flows through the coil 7, a magnetic field generated by the yoke 5, the magnet, the throat 4, and the plate 3 causes the drive section to slide in the drive direction d.

A cover 2 is provided to prevent foreign matter from coming into direct contact with these mechanical parts and optical parts from the outside 7, and to prevent dust floating in the air from entering. Conventional covers of this kind often cover the entire surface of the drive device as much as possible, except that they have holes that are large enough not to block the light beam.

Problems to be Solved by the Invention However, with the cover structure made to cover the entire surface of the drive device as described above, the escape route for air inside the cover is through holes for light flux transmission and holes for line processing. etc. is limited.

Therefore, when the device is driven, the two phenomena of compressing and expanding the air inside the cover and raising the temperature inside the cover due to the heat generated by the coil become significant.

This influence causes the following problems. To the Air 3 - 1 Compression and expansion of the air causes the cover to resonate in a high frequency range, and furthermore, the sensitivity of the drive unit deteriorates as the pressure inside the cover fluctuates. On the other hand, since the heat dissipation effect is small, the upper limit of the current that can be passed through the coil is naturally limited due to the need to suppress the amount of heat generated by the coil.

In view of the above problems, the present invention suppresses the resonance of the cover in the high frequency range by minimizing the compression and expansion of air and increasing the heat dissipation effect of the coil, without impairing the original role of the cover. An object of the present invention is to provide an objective lens driving device provided with a cover that can prevent sensitivity deterioration of a driving section and further increase the upper limit of allowable current of a coil.

Means for Solving the Problems In order to solve all of the above problems, the objective lens driving device of the present invention uses a force /<-f integrally molded with a porous material.

Operation The present invention minimizes the compression and expansion of the air inside the cover and enhances the heat dissipation effect of the coil without completely reducing the effect of preventing dust intrusion, which is the original role of the cover. be able to.

By reducing the compression and expansion of air, resonance of the cover in the high frequency range is suppressed. Therefore, resonance noise generated during operation of the objective lens driving device can be completely reduced. -! Since the pressure fluctuation inside the cover is reduced, deterioration of the sensitivity of the drive unit can be prevented.

On the other hand, by increasing the heat dissipation effect of the coil, the upper limit of the allowable current of the coil can be increased, and as a result, the sensitivity of the drive section can be increased.

Furthermore, when dew condensation occurs inside the cover, the dew condensation condition is quickly resolved because air circulation with the outside air is not sufficient.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to all the drawings. FIG. 1 shows a cover of an objective lens driving device in an embodiment of the present invention, and is shown in Fig. 25.

This corresponds to cover 2 in the figure. The cover 1 is integrally molded from a porous sintered material, and since gaps C exist between each particle of the sintered material, air can pass through the gaps. However, most of the dust floating in the air cannot pass through the gap, and the effect of preventing dust from entering the inside of the cover is not reduced.

The operation of the objective lens driving device provided with the cover having the filter structure as described above will be explained using the components shown in FIG.

When the driving section including the objective lens 6 and the coil 7 moves in the driving direction d, the driving section exhibits an effect similar to the piston of an engine, so that the air inside the cover 1 is compressed and expanded. However, since the cover is made of porous material, it has a tendency to move forward.
``Air'' acts as a moderator for the contraction and expansion of the air.As a result, the resonance of the bar in the high frequency region caused by the compression and expansion of the air is reduced to 1.
As a result, resonance noise generated during operation of the objective lens driving device can be reduced.

Furthermore, since pressure fluctuations inside the cover are reduced, deterioration in sensitivity of the drive unit can be prevented.

On the other hand, the breathability of the cover itself also contributes to enhancing the heat dissipation effect of the coil. Therefore, it is possible to increase the amount of heat generated by the coil by the amount that increases the heat dissipation effect, and it is possible to increase the upper limit of the allowable current of the coil. As a result, the sensitivity of the drive section can be increased.

Furthermore, the present invention also has the following effects.

That is, when dew condensation occurs inside the cover, the air permeability of the cover allows sufficient air circulation with the outside air, so that the dew condensation can be quickly eliminated.

In this example, the cover 1 is made of a porous sintered material, but it is not limited to the sintered material as long as it is a porous material. For example, it can be made of a porous material such as sponge rubber. A similar effect can be obtained even with a viscoelastic body. Moreover, in the case of a viscoelastic body, since it itself plays the role of a damping material, the effect of reducing the above-mentioned resonance sound becomes even more remarkable. According to the lens driving device, by using a cover integrally molded with porous material,
It is possible to minimize the compression and expansion of the air inside the cover and increase the heat dissipation effect of the coil. As a result, it is possible to suppress the resonance sound of the cover, prevent sensitivity deterioration of the drive unit, and increase the upper limit of the allowable current of the coil.

[Brief explanation of drawings]

FIGS. 1A and 1B are a perspective view and a detailed sectional view of a cover of an objective lens driving device according to an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional objective lens driving device. a, d... Cover cross section, 8... Bobbin, 10...
····base. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure (Haku (B)

Claims (1)

[Claims] A driving device for driving the objective lens is provided, and the outer periphery of the objective lens and the driving device is covered with a cover integrally formed of a porous material with a through hole through which light emitted from the objective lens passes. Characteristic objective lens drive device.