JP3829938B2 - Manufacturing method of lens holder of optical pickup. - Google Patents

Description

The present invention relates to a method of manufacturing a lens holder for holding a lens of an optical pickup of a digital device that records and / or reproduces information using an optical pickup such as a digital versatile disc (DVD) player or a compact disc (CD) player. It is about.

Recently, digital versatile discs (as audio equipment and information recording and playback devices)
Digital equipment using an optical pickup, such as a DVD player and a compact disc (CD) player, has become mainstream.

The optical pickups of these apparatuses detect information by focusing the light beam that has passed through the lens on a track (information bit string) formed on the optical disk surface as described above and reading the reflected light.

The optical pickup includes a driving motor and a lens holder including a lens, and the lens holder is supported so as to be rotatable and slidable on a rotating shaft. The optical pickup also includes a semiconductor laser output device, and the laser beam output from the semiconductor laser irradiates the track on the track formed on the disk surface through the lens in a focused manner. Information is read by detecting the reflected light.

At this time, when the focal point of the laser beam is deviated from the track surface due to the surface vibration of the disc or when the focal position is deviated from the track in the radial direction due to external vibration or the like, the reflection from the optical disc is accurately performed. Therefore, the focal length correction (focusing) and the radial deviation are corrected using a focusing servo that polarizes the focal length to an optimal position and a tracking servo that corrects the deviation of the optical axis of the laser beam in the radial direction of the disk ( tracking)
What is used is used.

The rotating shaft is fitted into a through hole provided in a shaft boss of the lens holder, and the outer peripheral surface of the rotating shaft and the inner peripheral surface of the through hole are in contact with each other over the entire length of the through hole. Then, the focusing is performed by sliding the lens holder along the rotation axis, and the tracking is performed by rotating the lens holder around the rotation axis.

Since the rotating shaft and the through hole are in contact with each other over the entire length of the through hole, the frictional resistance between the outer peripheral surface of the rotating shaft and the inner peripheral surface of the through hole is increased. In order to reduce the frictional resistance, the surface roughness of the surface of the rotary shaft and the inner peripheral surface of the through hole may be reduced (that is, the surface is smooth)
Cost including time is required for processing. Further, even if the surface roughness of the outer peripheral surface of the rotating shaft and the inner peripheral surface of the through hole is reduced, fine articles such as dust and dirt are caught in the contact portion between the rotating shaft and the through hole. Thus, the lens holder does not slide smoothly along the rotation axis and rotates around the rotation axis, which hinders high-precision and high-speed focusing and tracking.

Therefore, an inner diameter of the through hole is formed larger than the diameter of the rotary shaft, and a bearing is attached to both end portions of the through hole, or an injection mold having a larger intermediate shaft diameter (middle A lens holder manufacturing method has been proposed in which the inner diameter of the intermediate portion excluding both end portions of the through hole is manufactured using a small diameter, and the rotating shaft is brought into contact with only the both end portions of the through hole.
Japanese Utility Model Publication No. 9-395

However, when the rotating shaft is attached to the through hole via a bearing as described above, a bearing adapted to the rotating shaft and the through hole is necessary, and manufacturing (manufacturing) costs high. In addition, it is necessary to attach the rotating shaft so that it can be rotated (centered) and centered on the through hole, and it takes much time and labor to assemble. Further, when the through hole and the rotating shaft are connected via the bearing, the lens holder having the through hole can be easily rotated around the rotating shaft. Sliding is very difficult.

Further, when manufacturing (manufacturing) a lens holder using an injection mold having different outer diameters at both ends and the center as described above, the inner diameter of both ends is smaller than the inner diameter of the center. There is no need to manufacture and assemble complicated bearings as in the case of using the above-mentioned bearings, and sliding in the axial direction is possible. However, the injection mold (core) has a special shape and is expensive to manufacture. And it takes time. In addition, when the material is poured into the mold for injection molding and cooled, and the core is taken out,
Since the core has a larger central portion than both ends, the core is taken out using elastic deformation of the through-hole. However, even if the material is difficult to elastically deform or is a material that is elastically deformed, the core is removed from the through-hole. Productivity is low because it may not be removed or the through hole may be destroyed.

Alternatively, it may be possible to take out the core from the final product while disassembling or destroying the core. However, in the case of disassembling the core, time and labor are required for disassembly and subsequent reassembly. Also, in the case of the one that breaks the core, if the core is destroyed by one injection molding, the production cost of the core is also included in the final product, and as a result, the lens of the optical pickup that is the final product The manufacturing cost of the holder becomes high.

Accordingly, the present invention provides a method for manufacturing a lens holder for an optical pickup capable of easily and inexpensively manufacturing a lens holder for an optical pickup capable of performing focusing and tracking with high accuracy without using a special method or apparatus. The purpose is to provide.

In addition, the present invention is affected by the biting of fine substances such as dust and dust between the shaft boss of the lens holder and the rotating shaft, and the surface roughness between the inner peripheral surface of the shaft boss and the outer peripheral surface of the rotating shaft. It is an object of the present invention to provide a method for manufacturing a lens holder for an optical pickup in which the focusing and tracking operations of the lens holder are smoothly performed.

In order to solve the above-mentioned problem, the invention shown in claim 1 includes a melting step of melting raw materials, a mold body is closed in an internal space by placing a core at a predetermined position, and an injection mold. A mold closing process, an injection process in which the material melted in the melting process is poured into an injection mold closed in the mold closing process, and a material poured into the injection mold A pressure holding process for continuing to apply pressure, a cooling process for cooling the material poured into the injection mold, and the material poured into the injection mold in the cooling process is cooled and solidified. Then, a mold opening process for disassembling the mold body, and taking out the final article released from the mold body in the mold opening process,
And a method of manufacturing a lens holder for an optical pickup having a step of taking out a core from the final product, wherein the core is formed of a material having a lower thermal conductivity than the mold body. The injection mold has an optical pick-up lens holder that is perpendicular to the top plate and the bottom of the top plate. A space for pouring the melted material is formed so as to have a rotating shaft and a shaft boss that is pivotably and slidably connected, and the thickness of the shaft boss is 0.8 times or more the thickness of the top plate. An optical pickup lens holder manufacturing method is provided.
According to this configuration, when the melted material is poured and cooled, the end portions of the through hole on the top plate side and the shaft boss side are in contact with the outer peripheral surface of the lens holder, An inner diameter that is the same as or substantially the same as the outer diameter can be obtained, but the core has a lower thermal conductivity than the mold, and the portion between the top plate side end and the shaft boss side end is Since the core is made of the same material as that of the mold, the cooling time between the outer peripheral portion and the inside can be further different from the contact with the core. As a result, the solidification shrinkage forms a portion of the through hole between the top plate side end and the shaft boss side end in a more reliable concave curved surface.

Further, the invention shown in claim 2 is a melting step for melting raw materials, a mold closing step in which a mold body is closed in an internal space by placing a core in a predetermined position to form a mold for injection molding, An injection process in which the material melted in the melting process is poured into the mold for injection molding closed in the mold closing process, and a pressure holding process in which pressure is continuously applied to the material poured into the mold for injection molding A cooling process for cooling the material poured into the injection mold, and after the material poured into the injection mold in the cooling process is cooled and solidified, the mold body is An optical pickup lens holder comprising: a mold opening step for disassembling; and an article removing step for taking out a final article released from the mold body in the mold opening process and further taking out a core from the final article. A manufacturing method for the injection molding The mold includes a top holder for the lens holder of the optical pickup as the final article, and a shaft boss that is vertically and slidably connected to the rotary shaft below the top board. There is provided a lens holder manufacturing method for an optical pickup, characterized in that a space for pouring the dissolved material is formed so that the thickness is 0.8 times or more the thickness of the top plate.

According to this configuration, the shaft boss can also form the non-contact portion of the through-hole without using a special injection molding method or injection mold, and the optical pickup can be easily and inexpensively provided. It is possible to manufacture a lens holder.

Further, since the shape of the core is a cylindrical shape with no step on the outer peripheral surface, it is easy to take out from the through hole of the lens holder after cooling, and accordingly, when taking out the core from the lens holder, the through hole There is little to break.

Further, the end portions of the through hole on the top plate side and the shaft boss side are in contact with the outer peripheral surface of the lens holder, and the material is cooled and solidified from the portion facing the mold. An inner diameter that is the same or substantially the same as the outer diameter of the child can be obtained. However, it is difficult for heat to escape between the top plate side and the shaft boss side end of the inner peripheral surface of the through hole, and cooling takes time.

Accordingly, the portion between the top plate side end portion and the shaft boss side end portion of the through hole takes longer to solidify than the outer peripheral portion, and solidification shrinkage occurs. A portion between the top plate side end portion and the shaft boss side end portion of the through hole is formed on a concave curved surface by the solidification shrinkage.

According to the present invention, a lens holder for an optical pickup capable of performing focusing and tracking with high accuracy can be easily and inexpensively manufactured without using a special method or apparatus. Can be provided.

In addition, according to the present invention, fine substances such as dust and dust are caught between the shaft boss of the lens holder and the rotating shaft, and the surface roughness between the inner peripheral surface of the shaft boss and the outer peripheral surface of the rotating shaft is affected. Accordingly, it is possible to provide a method for manufacturing a lens holder of an optical pickup in which the focusing and tracking operations of the lens holder are smoothly performed.

The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1A is a plan view of an example of a lens holder manufactured by the method for manufacturing a lens holder of an optical pickup according to the present invention, and FIG. 1B is a side view of the lens holder shown in FIG. Figure 1 (C
) Is an XX cross-sectional view of the shaft boss of the lens holder shown in FIG. 1 (A), and FIG.
It is an enlarged view of sectional drawing of C).

A lens holder A shown in FIG. 1 includes a top plate 1 and a shaft boss 2 extending vertically from below the top plate 1. The top plate 1 is provided with a lens mounting hole 3 for mounting a lens Le, and the top plate 1 and the shaft boss 2 are integrally formed by injection molding as will be described later. A through hole 4 penetrating both the top plate 1 and the shaft boss 2 is provided.

A rotation shaft 5 is inserted into the through hole 4, and the lens holder A rotates around the rotation shaft 5.
Further, it slides up and down along the rotation shaft 5. Top plate side end 41 and shaft boss side end 4 of the through hole 4
Bearing portions 43 and 44 are formed on the inner peripheral surface of 2 to be fitted so that the rotary shaft 5 can turn and slide. A portion 45 (a portion between both end portions 41, 42) other than the both end portions 41, 42 of the through hole 4 is a non-contact portion 46 having a loose concave curved surface shape (FIGS. 1B, 1 </ b> C), ( D)).

Here, the thickness t of the shaft boss 2 is 0.8 times the thickness T of the top plate 1, but is not limited thereto, and a thickness of 0.8 times or more can be widely used. Is possible.
Accordingly, a concave curved surface called “sink” can be formed between both end portions 41 and 42 of the through-hole 4 at the time of injection molding described later, and the concave curved surface can be used as the non-contact portion 46. Yes (see FIG. 1D).

FIG. 2 is a schematic layout view of an injection mold used for manufacturing a lens holder of an optical pickup according to the present invention and a device for pouring material into the mold.

A mold B for injection molding shown in FIG. 2 is for manufacturing the lens holder A by injection molding, and includes a mold body 6 and a core 7 for forming a hole in the manufactured member. Have. The pouring device 8 for pouring the material includes a nozzle 81 for pouring the dissolved material into the assembled mold body 6, and a material supply tank 82 for storing the dissolved material and supplying it to the mold B through the nozzle 81. And have.

The mold body 6 is formed as a four-part mold, although not limited thereto. By correctly assembling each mold, a cavity 61 having the outer shape of the lens holder A of the optical pickup is formed inside. The melted material is poured into the cavity 61 with the core 7 for forming the through hole 4 being attached. The mold main body 6 is formed with a cooling pipe 62 for flowing a cooling refrigerant (in this case, water).

The core 7 has a cylindrical shape whose cross section perpendicular to the axis has the same circular shape, and the length in the axial direction is substantially the same as the length in the axial direction of the through hole 4 here, but is not limited thereto. Die B
An article having a length slightly longer than the axial length of the through-hole 4 may be employed so that the article is taken out from the core and the core 7 is easily taken out from the article. Further, with the core 7 attached to the mold body 6, the thickness t of the shaft boss 2 in the mold body 6 is 0.8 times the thickness T of the top plate portion 1.

The material that is poured into the mold B is a material that melts when heated and hardens when cooled, and since the rotating shaft 5 and the bearing portions 43 and 44 can rotate and slide, there is little friction. The material can be widely adopted. For example, liquid crystal polymer (LCP), thermoplastic resin (PPS) and the like can be mentioned.

FIG. 3 is a flowchart showing an example of a method for manufacturing a lens holder for an optical pickup according to the present invention.

The raw material constituting the lens holder A is melted by applying heat and stored in the material supply tank 82 (step S1). At this time, the thermoplastic resin (P
PS) is used. Further, the material supply tank 82 itself may be provided with a function of melting the raw material.

Next, the mold body 6 for injection molding made according to the shape of the lens holder A after completion.
Is assembled (step S2). At this time, the core 7 for making the through hole 4 of the shaft boss 2 provided in the lens holder A is sandwiched in a predetermined place of the injection mold main body 6 and the nozzle 81 for pouring the molten material is provided. Connect to a predetermined position of the mold body 6. Then, the molten material stored in the material supply tank 82 is poured into the mold body 6 for injection molding through the nozzle 81 (step S3). After the material is poured into the injection mold in step S3, the material is held in the material supply tank 82 at a predetermined pressure (step S4). By holding the pressure, it is possible to suppress cracking and deformation.

And in the state hold | maintained, the thermoplastic resin poured into the inside is rapidly cooled by circulating a cooling water through the cooling pipe 62 provided in the die main body 6 for injection molding (step S5). When the resin inside the mold B for injection molding solidifies by cooling, the top plate side end 41 and the shaft boss side end 42 of the through hole 4 provided with the core 7 are in contact with the mold immediately. Cool down. That is, although it becomes a hole having an inner diameter equal to the outer diameter of the core 7, the central portion 45 takes longer to cool than the outside, and solidification shrinkage (so-called sink) is generated by the time difference required for the cooling. . Thereby, the non-contact part 36 of the through-hole 4 is formed.

Thereafter, the pressure applied from the material supply tank 82 is reduced (step S6). Then, after confirming that the material inside the mold B is sufficiently cooled and cured, the mold body 6 for injection molding is disassembled (step S7), and the lens holder A is taken out from the mold B. (Step S8). At this time, the core 7 attached inside to form the through hole 4 of the lens holder A is also removed. At this time, since the core 7 has a shape with no unevenness in the axial direction, it can be easily extracted from the completed lens holder A.

By attaching the lens to the lens attachment hole 3 of the lens holder A formed as described above and attaching the rotating shaft 5 to the shaft boss 2, it can be used as a lens holder of an optical pickup.

As described above, both ends 41 of the through hole 4 of the lens holder A when cooling the material,
If there is a difference in cooling time between 42 and the intermediate portion 45, solidification shrinkage is likely to occur. Therefore, the core 7 may be made of a material having a lower thermal conductivity than the mold body 6. By doing so, the non-contact part 46 can be formed more reliably.

The top view of an example of the lens holder manufactured with the manufacturing method of the lens holder of the optical pick-up concerning this invention, a side view, sectional drawing, and an expanded sectional view are each shown. It is a schematic layout of an example of an injection molding apparatus used in the method for manufacturing a lens holder of an optical pickup according to the present invention. It is a flowchart which shows an example of the manufacturing method of the lens holder of the optical pick-up lens concerning this invention.

Explanation of symbols

A Lens holder 1 Top plate 2 Axis boss 3 Lens mounting hole 4 Through hole 41 Top plate side end portion 42 Axis boss side end portion 43, 44 Bearing portion 45 Central portion 46 Non-contact portion 5 Rotating shaft B Mold 6 Mold body 61 Cavity 62 Cooling pipe 7 Core 8 Casting device 81 Nozzle 82 Material supply tank

Claims (2)

A melting process for melting raw materials,
A mold closing step in which the mold body is placed in an internal space and the core is placed in a predetermined position and closed, and a mold for injection molding is formed;
An injection process in which the material melted in the melting process is poured into a mold for injection molding closed in the mold closing process;
A pressure-holding step in which pressure is continuously applied to the material poured into the injection mold,
A cooling step for cooling the material poured into the mold for injection molding;
A mold opening process for disassembling the mold body after the material poured into the mold for injection molding in the cooling process is cooled and solidified;
A method for producing a lens holder for an optical pickup, comprising: taking out a final article released from the mold main body in the mold opening process; and taking out a core from the final article.
The core is formed of a material having a lower thermal conductivity than the mold body, and has a cylindrical shape whose cross-section is a circle with the same diameter over the entire length.
The mold for injection molding includes a top plate of a lens holder of the optical pickup which is the final article, and a shaft boss that is vertically and downwardly connected to the rotary shaft and pivotally and slidably connected to the rotary shaft. And a space for pouring the dissolved material so that the thickness of the shaft boss is 0.8 times or more the thickness of the top plate. A melting process for melting raw materials,
A mold closing step in which the mold body is placed in an internal space and the core is placed in a predetermined position and closed, and a mold for injection molding is formed;
An injection process in which the material melted in the melting process is poured into a mold for injection molding closed in the mold closing process;
A pressure-holding step in which pressure is continuously applied to the material poured into the injection mold,
A cooling step for cooling the material poured into the mold for injection molding;
A mold opening process for disassembling the mold body after the material poured into the mold for injection molding in the cooling process is cooled and solidified;
A method for producing a lens holder for an optical pickup, comprising: taking out a final article released from the mold main body in the mold opening process; and taking out a core from the final article.
The mold for injection molding includes a top plate of a lens holder of the optical pickup which is the final article, and a shaft boss that is vertically and downwardly connected to the rotary shaft and pivotally and slidably connected to the rotary shaft. And a space for pouring the dissolved material so that the thickness of the shaft boss is 0.8 times or more the thickness of the top plate.

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