JPH0815570A - Metal mold for molding plastic ferrule for optical connector - Google Patents

Abstract

PURPOSE:To provide a metal mold for molding a ferrule with which the plastic ferrule having high dimensional accuracy and excellent mechanical strength, connecting reliability, cost effectiveness, etc., is obtainable. CONSTITUTION:This metal mold consists of a metal mold body 30, a cavity part 31 forming the outside shape of the ferrule, a small-diameter pin 32 forming an optical fiber guide hole and a core part 33 forming a coated optical fiber guide hole. This small-diameter pin 32 is fixed into the front end 34 of a cavity and the front end of the small-diameter pin 32 is held by having a specified spacing in the core part 33. The cavity part 31 or the core part 33 is partly provided with a vent hole 35 for generating a vacuum state in the metal mold body 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for producing a ferrule for an optical connector used for connecting a single mode optical fiber by plastic molding, and more particularly, to a ferrule manufactured by an injection molding technique. It has been devised so that it can be manufactured in a standard manner.

[0002]

2. Description of the Related Art With the development of optical communication technology, it has become possible to introduce optical fibers to each home and provide various communication services. In order to realize such an optical subscriber communication network, an economical optical connector is necessary.

Conventionally, in order to connect an optical fiber used for optical communication, two ferrules 11A and 11B in which two optical fibers are inserted as shown in FIG.
It is performed by aligning and joining in 2. In addition,
Reference numerals 13A and 13B in the figure denote optical fiber cords. For ferrules used for such purposes, extremely high dimensional accuracy is required for optical fiber guide hole diameter, optical fiber guide hole diameter eccentricity, ferrule outer diameter, and roundness of outer diameter. ． Conventionally, a ferrule has been produced by cutting and polishing ceramics or metal with high precision. Therefore, there is a problem that manufacturing efficiency is low and manufacturing cost is high.

In order to solve these problems, attempts have been made to produce a ferrule by plastic molding. However, as the original optical fiber made of plastic-molded ferrule, the outer diameter of the core was 5
The so-called “multimode fiber”, which is as large as 0 μm, is mainly used, and although the plastic ferrule was applicable to the connection of these fibers,
There is a problem that it is not applicable to the so-called "single mode fiber" having an outer diameter of 8-10 µm which is currently used. Further, "transfer molding" as a molding method requires post-treatments such as deburring and post-molding heat treatment, and is not sufficient in terms of economy.

On the other hand, attempts have been made to produce a plastic ferrule by using an injection molding technique which is highly economical. It is known that PPS (polyphenylene sulfide) or the like, which has relatively high heat resistance and fluidity, has been studied as the resin used here. However, there has not been obtained one that can withstand the connection of a single mode fiber and that satisfies dimensional accuracy, mechanical strength, various types of reliability, and the like.

FIG. 5 is a structural cross-sectional view of the ferrule 11, in which an optical fiber core wire guide hole 14 and an optical fiber guide hole 15 are formed, and the dimensional accuracy of the ferrule required for connecting a single mode fiber is described below. It is shown in Table 1.

[Table 1] Among these, the eccentricity of the optical fiber guide hole 15 is a characteristic value directly related to the connection loss, and it has been particularly difficult to reduce this value.

FIG. 6 shows the structure of a conventional mold for ferrule injection molding. As shown in FIG.
A cavity portion 21 for forming the outer diameter of the ferrule 11 shown in FIG. 5, and an optical fiber guide hole (125 μm)
Core portion 23 for forming an optical fiber guide hole (about 2 mm) having a thin pin 22 for forming
The two parts are fitted together at the parting surface 24. The small-diameter pin 22 forming the optical fiber guide hole is guided to the receiving hole 26 provided in the cavity tip portion 25 forming the ferrule tip portion. Here, the gap between the small diameter pin 22 and the receiving hole 26 should be at least 2-3.
Clearance of μm is required. This is because if the clearance is too small, the small-diameter pin 22 collides with the insert and the small-diameter pin 22 is damaged. Further, when the molding resin flows in from the gate 27, a certain clearance or more is required in order to use this clearance to release the air inside the mold.

Because of such a die structure, when the resin flows in, it is unavoidable that the small diameter pin itself fluctuates within the clearance range due to the injection pressure. As a result, the eccentricity of the ferrule became a value of 2-3 μm, and a highly reliable connection that could be used for connecting a single mode fiber was not obtained.

In view of the above problems, the present invention provides a plastic ferrule for an optical connector used for connecting a single mode fiber, which has high dimensional accuracy, mechanical strength,
An object of the present invention is to provide a ferrule molding die capable of obtaining a plastic ferrule having excellent connection reliability and economy.

[0010]

The structure of a ferrule molding die according to the present invention for achieving the above object is a molding die for manufacturing a ferrule for an optical fiber connector having an insertion hole for fixing an optical fiber by plastic molding. The mold is characterized in that a small-diameter pin that forms an optical fiber guide hole is formed inside the tip of the cavity that does not move when the mold that forms the ferrule outer shape is clamped.

Further, another structure of the ferrule molding die according to the present invention is such that a ferrule outer shape is formed in a molding die for manufacturing a ferrule for an optical fiber connector having an insertion hole for fixing an optical fiber by plastic molding. Cavity, a small diameter pin that forms an optical fiber guide hole, and a core portion that forms an optical fiber core wire guide hole. The small diameter pin is fixed to the cavity tip and the tip of the small diameter pin is formed. Are held in the core with a certain space, and a vent hole is provided in a part of the cavity part or the core part to make the inside of the mold a vacuum state.

Furthermore, another plastic ferrule molding die for an optical connector according to the present invention is a molding die for manufacturing an optical fiber connector ferrule having an insertion hole for fixing an optical fiber by plastic molding.
The ferrule includes a cavity portion forming an outer shape, a small diameter pin forming an optical fiber guide hole, and a core portion forming an optical fiber core wire guide hole. The cavity part or the core is characterized in that the tip of the radial pin is held in the core with a constant space, and part of the cavity part or the core part is formed of a gas permeable metal. It is characterized in that a part of the portion is formed of a breathable metal.

The contents of the present invention will be described below. As a result of a detailed study of the problems of the prior art, the present invention does not move the thin pin itself forming the optical fiber guide hole, not the core part that moves with mold clamping of the mold, but the mold pin clamping. It is basically provided at the tip of the cavity. FIG.
The basic structure of the present invention is shown in FIG. As shown in the figure, a molding die for manufacturing the ferrule for an optical fiber connector according to the present invention by plastic molding includes a mold body 30 and
It is composed of a cavity portion 31 that forms the outer shape of the ferrule, a small diameter pin 32 that forms an optical fiber guide hole, and a core portion 33 that forms an optical fiber core wire guide hole. The tip of the small-diameter pin 32 is fixed and held in the core portion 33 with a constant space, and the inside of the mold body 30 is evacuated to a part of the cavity portion 31 or the core portion 33. The ventilation port 35 is provided. In the figure, reference numeral 36 is a small pin 32.
, 37 is a gate, and 38 is a parting surface. As described above, the small-diameter pin 32 itself forming the optical fiber guide hole is provided not on the core part 33 that moves with mold clamping of the mold but on the cavity tip 34 side that does not move during mold clamping. When the resin is molded by using a plastic resin, it is possible to avoid the small-diameter pin 32 itself from fluctuating due to the inflow of the resin, and the irregular eccentricity unlike the conventional case does not occur. However, the eccentricity of the ferrule is due to the cavity 31 of the thin pin 32.
Since it is caused only by the displacement of the mounting position on the small diameter pin / cavity side, extremely precise attention is required for the processing accuracy of the small diameter pin / cavity side and the mounting operation of the small diameter pin 32 on both the small diameter pin / cavity tip side.

Here, it is necessary to integrate the tip of the small diameter pin 32 and the core portion 33 when the die is clamped. FIG. 2 shows a detailed view at this time. Also in the mold of the present invention, a certain clearance is required between the tip of the small diameter pin 32 and the core portion 33, and the tips of the small diameter pin 32 and the core portion 33 as shown here are tapered. With this configuration, the mold can be smoothly clamped. Further, since this part of the ferrule is merely for guiding the optical fiber to the optical fiber guide hole, even if the eccentricity due to the clearance of several μm occurs, it does not adversely affect the connection characteristic itself of the optical fiber. Further, when the resin flows in, when the resin flows into the gap between the core pin and the core portion, a burr is generated, which causes a fatal problem as a ferrule that the optical fiber cannot be inserted. However, if this clearance is 5 μm or less, such a problem does not occur because the resin flows in the direction indicated by the X direction in the figure. However, since the flow characteristics of the resin differ depending on the resin used and the molding conditions, it is necessary to appropriately design the tapered shape of the core portion. Regarding this point, software for analyzing the flow of the resin has been developed in recent years, and thus these may be appropriately used.

On the other hand, the mold structure of the present invention has a problem that it is difficult to remove air from the mold. That is, it is extremely difficult to provide an air vent on the core pin mounting side.

In the present invention, the following method (1),
It is solved by (2).

(1) As shown in FIG. 1, when the inside of the die main body 30 is evacuated and a resin is made to flow in, a part of the die is provided with a ventilation port 35 for evacuation which is different from the gate 37. Is provided. At this time, as the resin to be used, it is necessary to select a resin that generates as little gas as possible during injection molding. In this respect, for example, PPS (polyphenylene sulfide) resin or the like is not a preferable choice.

(2) As shown in FIG. 2, for venting air,
A part of the mold is formed by using the breathable metal 39. This eliminates the need to provide the vent hole 35 for venting the air. Here, the air-permeable metal means an average pore diameter of 10 μm.
The fine communication holes of m or less are evenly distributed over the entire metal. For this reason, it cannot be applied to a mold part requiring surface smoothness, but it can be appropriately used in other places. In the case of a ferrule, the mold portion of the cavity tip portion 34 forming the ferrule tip portion and the core portion 33 are suitable. It is also possible to use the methods (1) and (2) together.

As a processing method of the molding die, milling or the like can be used. In addition, it is also effective to manufacture it by an electroforming method particularly in a portion such as the cavity portion 31 which requires precision inside the mold. Here, the electroforming method refers to a method in which a metal is attached to the outside of a master processed with high accuracy by electroplating and the master is removed to form a cavity. Conventionally, the mold by electroforming has a problem that the strength is weak and the number of shots in injection molding cannot be large, but with recent technology, it is possible to obtain the same strength as general mold steel materials. Also, it can be appropriately used in the present invention.

Further, particularly in the case of a high precision molded product such as a ferrule, it is necessary to pay attention to the surface precision of the die surface as well as the alignment precision on the parting surface. In order to improve the alignment accuracy, there are a structure having a spigot portion, a method of providing a taper pin or a cotter block, which can be appropriately selected.

Further, a gate 37 for introducing resin into the mold.
The shape of is, for example, a pinpoint gate, a ring gate, a film gate, or the like, and can be appropriately selected according to the position of the gate. As the injection conditions, "high-speed injection technology (injection pressure decreases)" that makes the injection speed faster, or conversely, decrease the injection speed as much as possible,
A "low-speed injection molding" technique or the like for reducing distortion after molding can be appropriately used.

As a molding machine to be used, a small injection molding machine having a relatively low mold clamping pressure (50 t or less) can be used. A generally known hydraulic injection molding machine, an electric injection molding machine using a servo motor as a drive source, or a hybrid type apparatus using a hydraulic / electric type on the injection side / form clamping side can be used. A particular point to note in the molding machine is the parallelism between the movable plate and the fixed plate, which move by mounting the mold. If this value is bad, the alignment accuracy of the mold is lowered and it becomes unsuitable for precision molding. The parallelism value is defined by the error in the distance between the plates and is at least 50
It is necessary to be within μm, more preferably within 30 μm.

A liquid crystal polymer or the like can be used as the molding resin.

[0024]

EXAMPLES Preferred examples will be described below.

[Embodiment 1] A mold part as shown in FIG. 1 was manufactured by using a cavity portion (inner diameter: 2.5 mm), a small diameter pin (core pin diameter; 125 μm) 32, a core portion (outer diameter 2 m).
m) 33 was manufactured by grinding SKD61 steel material (hardness: HRC58). In the present embodiment, the eccentricity is set to 0.4 μm, the small-diameter pin 32 and the cavity portion 32 are attached, and the eccentricity is set to 2 μm by aligning the core portion 33 with the taper pin. The clearance between the tip of the small diameter pin and the core was 2 μm. Gate 37
The structure is a both-side structure, and is provided with a vent hole 35 for vacuuming inside the mold body 30. Using the mold thus produced, injection molding of a ferrule was performed using a liquid crystal polymer containing 30% by weight of glass beads. The molding conditions of this example are shown in "Table 2" below. The dimensional characteristics of the obtained ferrule are shown in "Table 3" below. As shown in "Table 3", the dimensional characteristics of the ferrule of this example were extremely excellent.

[0026]

[Table 2]

[0027]

[Table 3]

[Embodiment 2] In Embodiment 1, as shown in FIG.
The four parts of the cavity tip 34 are made of breathable metal 39.
a to 39d. In this example, the vent for vacuuming of Example 1 was not provided. Using the mold thus manufactured, a plastic ferrule was manufactured in the same manner as in Example 1. The dimensional characteristics of the obtained ferrule are shown in "Table 3" above. As shown in the table, the ferrule of this example was also extremely excellent as in Example 1.

[Example 3] A mold was manufactured in the same manner as in Example 2, except that the cavity was manufactured by an electroforming method. The results are shown in "Table 3". As shown in the table,
The ferrule of this embodiment has improved dimensional accuracy such as eccentricity and accuracy of outer diameter.

[0030]

As described above, according to the plastic ferrule molding die for an optical connector of the present invention, the small-diameter pin itself forming the optical fiber guide hole moves along with the die clamping. When the ferrule is molded using plastic resin, it is possible to avoid the small diameter pin itself from fluctuating due to the inflow of resin when the ferrule is molded by using plastic resin, instead of the part Such an irregular eccentricity does not occur, and there is an advantage that a plastic ferrule for an optical connector that can be used for connecting a single mode fiber and has excellent connection characteristics, reliability, and economy can be obtained.

Further, when the resin is introduced after the inside of the mold body is evacuated, a part of the mold is provided with a vent hole for vacuuming different from the gate, so that the air inside the mold is evacuated. Will be easier.

Further, for venting air, the vent hole for venting is formed by using a die part at the tip of the cavity, which is a part of the die, and a core part made of a breathable metal having air permeability. Even if it is not provided, the air inside the mold can be vented.

[Brief description of drawings]

FIG. 1 is a view showing a mold structure of the present invention.

FIG. 2 is a diagram showing a part of the mold structure of the present invention in detail.

FIG. 3 is a view showing a cavity tip of a mold of the present invention.

FIG. 4 is a view showing a fitted state of a ferrule in a split sleeve.

FIG. 5 is a sectional view of a plastic ferrule.

FIG. 6 is a view showing a conventional plastic molding die.

[Explanation of symbols]

 11, 11A, 11B Ferrule 12 Split sleeve 13A, 13B Optical fiber cord 14 Optical fiber core wire guide hole 15 Optical fiber guide hole 20 Mold body 21 Cavity part 22 Small diameter pin 23 Core part 24 Batting surface 25 Cavity tip part 26 Receiving part 27 Gate 30 Mold body 31 Cavity part 32 Small diameter pin 33 Core part 34 Cavity tip part 35 Vent hole 36 Receiving part 37 Gate 38 Parting surface 39 Breathable metal X Resin flow line

Claims (3)

[Claims] 1. In a molding die for manufacturing an optical fiber connector ferrule having an insertion hole for fixing an optical fiber by plastic molding, the tip of a cavity portion that does not move when the die forming the ferrule outer shape is clamped. A plastic ferrule molding die for an optical connector, characterized in that a thin pin for forming an optical fiber guide hole is formed inside the portion. 2. A molding die for manufacturing a ferrule for an optical fiber connector having an insertion hole for fixing an optical fiber by plastic molding, wherein a cavity portion forming a ferrule outer shape and a small diameter pin forming an optical fiber guide hole. A core portion forming an optical fiber core wire guide hole, the thin pin is fixed to a cavity tip, and the tip of the thin pin is held in the core at a constant interval, Further, a mold for molding a plastic ferrule for an optical connector, characterized in that the mold is provided with a vent in a part of the cavity part or the core part to make a vacuum state in the mold. 3. A molding die for manufacturing an optical fiber connector ferrule having an insertion hole for fixing an optical fiber by plastic molding, wherein a cavity portion forming a ferrule outer shape and a small diameter pin forming an optical fiber guide hole. A core portion forming an optical fiber core wire guide hole, the thin pin is fixed to a cavity tip, and the tip of the thin pin is held in the core at a constant interval, Further, a mold for molding a plastic ferrule for an optical connector, characterized in that a part of the cavity portion or the core portion is formed of a breathable metal.