Optical pickup feeding device

An optical-pickup feeding apparatus includes a pickup base on which an optical pickup is mounted, which includes a sliding bearing with a lubricant agent; and a lead screw that is slidably fitted into the sliding bearing. A peripheral surface of a screw thread of the lead screw is formed in a shape of a circular arc.

TECHNICAL FIELD

The present invention relates to an optical-pickup feeding apparatus provided in an optical disk player and an optical disk recorder for performing a reproduction or a recording operation with respect to an optical recording medium such as a CD and a DVD.

BACKGROUND ART

Conventionally, an optical-pickup feeding apparatus is configured in such a manner that a plate spring is fixed on a pickup base, a rack biased by the plate spring is engaged with a lead screw, the pickup base shifts by a rotation of the lead screw. The plate spring is structured with a plate spring A that consistently works when the lead screw rotates and with a plate spring B having an edge adjacent to a position for attaching the rack. The plate spring B does not work by a usual rotation but works for a displacement in a direction of releasing the rack from the lead screw when the rack is released from the lead screw and an engagement failure occurs. Therefore, an increase of a resistance in feeding the optical pickup and the engagement failure are prevented (see, for example, Patent Document 1).

DISCLOSURE OF INVENTION

Problem to be Solved by the Invention

However, although the conventional optical-pickup feeding apparatus can suppress an increase of a resistance in conveying the optical pickup caused by a frictional force between the lead screw and the rack, there still is a problem that a countermeasure has not been taken against an increase of a resistance caused by a viscosity resistance of a lubricant agent between a shaft bearing arranged on the pickup base and the lead screw.

The above described is an example of a problem to be solved by the present invention and an object thereof is to provide an optical-pickup feeding apparatus that suppresses the increase of the resistance in feeding the optical pickup caused by the increase of the viscosity resistance of the lubricant agent between the shaft bearing arranged on the pickup base and the lead screw, in a low-temperature environment.

Means for Solving Problem

To solve the above problems and to achieve the object, an optical-pickup feeding apparatus according to one aspect of the present invention includes a pickup base on which an optical pickup is mounted, which includes a sliding bearing with a lubricant agent; and a lead screw that is slidably fitted into the sliding bearing. A peripheral surface of a screw thread of the lead screw is formed in a shape of a circular arc.

Effect of the Invention

The optical-pickup feeding apparatus according to the present invention is suitable for suppressing the increase of the resistance in feeding the optical pickup caused by the increase of the viscosity resistance of the lubricant agent between the shaft bearing arranged on the pickup base and the lead screw in a low-temperature environment and for working, even in the low-temperature environment, in the same way as in normal temperature.

EXPLANATIONS OF LETTERS OR NUMERALS

BEST MODE(S) FOR CARRYING OUT THE INVENTION

Exemplary embodiments of an optical-pickup feeding apparatus according to the present invention are explained below in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments explained below.

First Embodiment

FIG. 1is a top view of an optical-disk reproducing apparatus including the optical-pickup feeding apparatus according to the present invention.FIG. 2is a bottom view of the optical-disk reproducing apparatus.

According toFIGS. 1 and 2, an optical-disk reproducing apparatus200includes a disk table2rotatably driven by a spindle motor5and an optical-pickup feeding apparatus100, mounted on a chassis1.

The chassis1is formed into a substantially rectangular shape by punching and press molding a metal plate and installed in a body of an optical disk player (not shown) with flanges1darranged on three portions of a periphery of the chassis1. The spindle motor5is mounted on a support plate6and the support plate6is mounted on the chassis1. The disk table2is held on one side of a center opening portion1cof the chassis1.

The optical-pickup feeding apparatus100includes an objective lens7, a carriage3, as a pickup base, that carries an optical pick up including an optical system such as a semiconductor laser and an objective-lens drive mechanism, a lead screw9that is rotatably driven by a carriage conveying motor11, that supports one side of the carriage3, and that is used as a main shaft for driving and conveying the carriage3, and a sub shaft8that slidably supports the other side of the carriage3.

The sub shaft8is a shaft having a round cross section and end portions of the sub shaft8are attached to a left periphery of the chassis1with skew screws38,38. With the skew screws38,38, height for attaching the sub shaft8to the chassis1can be adjusted for a skew adjustment.

One end portion of the lead screw9as the main shaft is rotatably supported by a shaft bearing20arranged on a skew adjustment member15. The skew adjustment member15is rotatably supported by a bracket10mounted on the chassis1, via a rotary shaft24. With a skew screw22that engages the chassis1and the skew adjustment member15, a height for attaching the lead screw9to the chassis1can be adjusted for the skew adjustment.

The other end portion of the lead screw9is rotatably supported by a shaft bearing29arranged on a skew adjustment member31made of resin. The skew adjustment member31is mounted on the chassis1with a locking screw33. With the skew screw22that engages the chassis1and the skew adjustment member31, the skew adjustment member31is bent, and the height for attaching the lead screw9to the chassis1can be adjusted for the skew adjustment.

The lead screw9is rotatably driven by the carriage conveying motor11mounted on the bracket10. A driven gear14mounted on the lead screw9is engaged with a small gear of a two-tire middle gear13that engages with a drive gear12mounted on an output shaft11aof the carriage conveying motor11, and reduces a speed of a rotation of the carriage conveying motor11.

Two arms3b,3bare arranged on a right side of the carriage3. The lead screw9is inserted between the two arms3b,3band a lubricant-agent-impregnated sliding bearing3e,explained later, to be slidably fitted is attached to the two arms3b,3b.A rack3cis attached between the two arms3b,3b.The rack3cis pressed toward the lead screw9by a plate spring3dfixed to the carriage3and is engaged with the lead screw9for conveying the carriage3forward and backward by a rotation of the lead screw9to shift the optical pickup to a target position.

A fork-shaped sub shaft bearing3ais bulged from a left portion of the carriage3toward the sub shaft8. The sub shaft bearing3asandwiches the sub shaft8so that the left portion of the carriage3becomes slidably supported by the sub shaft8.

FIG. 3is a schematic for explaining a structure of the lead screw9in the optical-pickup feeding apparatus100according to the first embodiment.FIG. 4is a schematic of a lead screw59in a conventional optical-pickup feeding apparatus. As shown inFIG. 4, the lead screw59in the conventional optical-pickup feeding apparatus includes a spiral groove59aformed on a shaft having a diameter φd=3 mm to 4 mm and a peripheral portion59b,in a spiral band state, of a screw thread having a width S=2 mm to 3 mm, is slidably engaged with the lubricant-agent-impregnated sliding bearing3earranged on the arm3bfor bearing the main shaft of the carriage3.

A clearance between the lubricant-agent-impregnated sliding bearing3eand the peripheral portion59bof the screw thread of the lead screw59is configured to be small in consideration of an occurrence of distortion, mechanical decentration, a backlash, and the like. Although the clearance is lubricated with a lubricant agent run out of the lubricant-agent-impregnated sliding bearing3e,when in a low-temperature environment, a viscosity resistance of the lubricant agent becomes extremely high, causing a bad effect for a high-speed search of a disk.

As a measure for lowering the viscosity resistance in a low-temperature environment, if a viscosity of the lubricant agent is lowered, the lubricant agent gets spattered due to a high-speed rotation of the lead screw59. Therefore, the viscosity of the lubricant agent cannot be lowered. Further, it can be considered to make the clearance bigger between the lubricant-agent-impregnated sliding bearing3eand the peripheral portion59bof the screw thread of the lead screw59; however, it can hardly be adopted because of a larger distortion, mechanical decentration, and backlash it will cause.

FIG. 3is a schematic of an example of a suppression mechanism that suppresses the viscosity resistance of the lubricant agent. The suppression mechanism according to the present invention is a mechanism for reducing a size of a contact area between the lubricant-agent-impregnated sliding bearing3eand the lead screw9to, for example, suppress an increase of a torque constant of a viscosity resistance load of the lubricant agent in a low-temperature environment. It is enough to form the suppression mechanism on at least one of the lubricant-agent-impregnated sliding bearing3eand the lead screw9.

According to the optical-pickup feeding apparatus100shown in the first embodiment, the suppression mechanism is formed on the lead screw9. More specifically, a peripheral portion9bof the lead screw9having a diameter φd is made on a left side with a substantial width of “T” and the other portion of the lead screw9is notched in a layer so that a clearance H is formed between the lubricant-agent-impregnated sliding bearing3eand the lead screw9. Because the width “T” of the peripheral portion9bis narrow, referring to a cross section shown inFIG. 3, the lubricant-agent-impregnated sliding bearing3eand the lead screw9are substantially in a point-contact state. A point-contact area is spirally continued in a circumferential direction, so that the lubricant-agent-impregnated sliding bearing3eand the lead screw9linearly come into contact. According to the optical-pickup feeding apparatus100of the first embodiment, the size of the contact area between the lubricant-agent-impregnated sliding bearing3eand the lead screw9is reduced to a linear state and the increase of the torque constant of the viscosity resistance load of the lubricant agent in a low-temperature environment can be suppressed.

FIG. 5is a schematic of a modification of the optical-pickup feeding apparatus100according to the first embodiment. The peripheral portion9bof the lead screw9having a diameter φd is made not on the left side but on a center area of the lead screw9, which is a different point in a configuration from that shown inFIG. 3. Other sizes in the configuration are the same. An area for making the peripheral portion9bcan be on the left side, on a right side, or on the center area along an axial direction.

Second Embodiment

Next, a structure of the optical-pickup feeding apparatus100according to a second embodiment is explained with reference toFIG. 6.FIG. 6is an enlarged cross section along the line A-A shown inFIG. 2for explaining the optical-pickup feeding apparatus100of the second embodiment. According to the optical-pickup feeding apparatus100of the second embodiment, a peripheral portion69bof a thread of a lead screw69having a diameter φd is formed so that a longitudinal sectional view of the peripheral portion69bbecomes a circular arc. Other configurations are the same as those of the first embodiment.

In view of the cross section shown inFIG. 6, the lubricant-agent-impregnated sliding bearing3eand the lead screw69are substantially in a point-contact state and a point-contact area is spirally continued in a circumferential direction, resulting in making a linear contact between the lubricant-agent-impregnated sliding bearing3eand the lead screw69. According to the optical-pickup feeding apparatus100of the second embodiment, a size of a contact area between the lubricant-agent-impregnated sliding bearing3eand the lead screw69is reduced to a linear state and an increase of the torque constant of the viscosity resistance load of the lubricant agent in a low-temperature environment is suppressed. Accordingly, even with the second embodiment, an increase of a resistance in conveying the optical pickup caused by the increase of the viscosity resistance of the lubricant agent in a low-temperature environment can be suppressed.

Next, a structure of the optical-pickup feeding apparatus100according to a third embodiment is explained with reference toFIG. 7.FIG. 7is an enlarged cross section along a line B-B shown inFIG. 1for explaining the optical-pickup feeding apparatus100of the third embodiment. According to the optical-pickup feeding apparatus100of the third embodiment, a configuration of a lead screw is the same as that of the conventional lead screw59shown inFIG. 4. A lubricant-agent-impregnated sliding bearing73eis formed into a hexagon that circumscribes the peripheral portion59bof the lead screw59, at three points in a circumferential direction, in a linear state along an axial direction. A shape of a cross section of the lubricant-agent-impregnated sliding bearing73ecan be not only the hexagon but also other polygons with more than three sides.

According to the optical-pickup feeding apparatus100of the third embodiment, a size of a contact area between the lubricant-agent-impregnated sliding bearing73eand the lead screw59is reduced in linear state and an increase of the torque constant of the viscosity resistance load of the lubricant agent in a low-temperature environment is suppressed.

FIG. 8is a schematic of a modification of the optical-pickup feeding apparatus100according to the third embodiment. The lubricant-agent-impregnated sliding bearing73eis formed into a pentagon that circumscribes the peripheral portion59bof the lead screw59, at two points in a circumferential direction, in a linear state along an axial direction. As explained, contact points can be two. A shape of the cross section of the lubricant-agent-impregnated sliding bearing73ecan be not only the pentagon but also other polygons with more than three sides.

Although the embodiments according to the present invention are explained above, the lubricant-agent-impregnated sliding bearings3eand73ecan not only be the lubricant-agent-impregnated sliding bearings but also be a slide shaft, on which the lubricant agent is spread. Further, the suppression mechanism for (formed on) the lead screws explained in the first and the second embodiments and the suppression mechanism for the lubricant-agent-impregnated sliding bearings explained in the third embodiment can be combined. It is needles to say that an optical-disk reproducing apparatus and an optical-disk recording apparatus that incorporate the optical-pickup feeding apparatus shown in the embodiments according to the present invention can be effective with the optical-pickup feeding apparatus.

INDUSTRIAL APPLICABILITY

As described above, the optical-pickup feeding apparatus according to the present invention is suitable as the optical-pickup feeding apparatus for an optical disk player and an optical disk recorder for performing a reproduction and a recording with respect to an optical recording medium such as a CD and a DVD, and particularly, is suitable for an apparatus used outside.