JP2006331710A - Method of manufacturing coaxial cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a coaxial cable excellent in softness and flexibility while squeezing the cable into an intended diameter. <P>SOLUTION: The manufacturing method of the coaxial cable comprises a process of forming a winding body 3b by winding a copper tape 3a serving as an outside conductor 3 in cylindrical shape, a process of inserting a core 5 formed by surrounding an inside conductor 1 by an insulator 2 into the winding body 3b of the copper tape 3a, a tube forming process forming the winding body 3b into which the core 5 is inserted into tube shape, a welding process forming a coaxial cable elemental body 6 by welding butted end edges of the copper tapes 3a formed into tube shape, a sinking process reducing the diameter of the coaxial cable elemental body 6 by drawing it, and an annealing process heating the coaxial cable elemental body 6 passed through the sinking process for a prescribed period. The insulator 2 is made of fluororesin having continuous usable temperature of 200°C to 250°C. The crosssection shrinking ratio of copper at sinking process is set to 30% or higher and less than breakage limit of the copper. The annealing temperature is set to 240°C to 250°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a small-diameter coaxial cable having an outer diameter of about 2 to 3 mm.

As a method of manufacturing a small-diameter coaxial cable, a metal tape is wound into a cylindrical shape to form a wound body, and a core formed by covering an inner conductor with an insulator is inserted into a wound body of copper tape, The wound body with the core inserted is formed into a tubular shape, the butt end of the copper tape is welded to form a coaxial cable body, and the coaxial cable body after the welding process is narrowed down (sinking) to a predetermined diameter There is known a method of reducing the diameter to a minimum (for example, see Patent Document 1).
JP-A-6-251648

  According to the above method, the outer conductor is hardened by the residual stress generated during the winding process of the copper tape in the manufacturing process, the thermal strain stress in the welding process, the residual stress generated in the sinking process, etc. , Flexibility decreases.

  The present invention has been made by paying attention to such a situation, and can produce a coaxial cable that can be made excellent in flexibility and flexibility while being reduced to a desired diameter by narrowing down. It aims to provide a method.

  In order to achieve the above object, the present invention comprises a step of forming a wound body by winding a copper tape as an outer conductor into a cylindrical shape, and a core formed by covering the inner conductor with an insulator. A step of forming the coiled body into which the core is inserted, and a welding step of forming a coaxial cable body by welding the butt edges of the copper tape formed into a tubular shape. And a sinking process for reducing the diameter of the coaxial cable body to a predetermined diameter, and an annealing process for heating the coaxial cable body after the sinking process for a predetermined time. Furthermore, a fluororesin material having a continuous use temperature of 200 ° C. to 260 ° C. is used for the insulator, and the cross-sectional reduction rate in the sinking process is set to 30% or more and less than the copper fracture limit, and the annealing temperature is set to about Set to 240 ° C to 250 ° C.

  According to this, the outer conductor of the coaxial cable that has undergone the sinking process is hardened by the residual stress, but the residual stress of the outer conductor is reduced or eliminated by annealing, so that the coaxial cable is flexible and flexible. Increases nature.

  In this case, the insulator is also heated to about 240 ° C. to 250 ° C. in the annealing step, but a fluororesin material is used as the insulator. Since the continuous use temperature of the fluororesin material is 200 ° C. to 260 ° C., the insulator is not unduly softened or melted by the heat treatment (240 ° C. to 250 ° C.).

Note that the cross-sectional reduction ratio is expressed by% (cross-sectional area of the external conductor after sinking process / cross-sectional area of the external conductor before sinking process). Here, the cross-sectional area refers to the cross-sectional area of only the copper portion not including the internal space.
For example, before the sinking process,
Outer conductor outer diameter: 3.782 mm
Outer conductor thickness: 0.259 mm
After the sinking process
Outer conductor outer diameter: 3.287 mm
Outer conductor thickness: 0.274mm
, The cross-sectional reduction ratio is the cross-sectional reduction ratio = {(3.782-0.259) × π− (3.287−0.274) × 0.274 × π} / {(3.782-0. 259) × 0.259 × π} = 0.0952≈9.5%.

  The annealing treatment is preferably performed in an inert gas atmosphere. If it does so, it will prevent that the copper tape (external conductor) heated to the annealing temperature (about 240 degreeC-250 degreeC) and the internal conductor of a core will be oxidized, and the fall of signal transmission efficiency will be prevented.

  As described above, according to the present invention, although the diameter is reduced to a desired diameter through a sinking process, flexibility and flexibility comparable to a coaxial cable manufactured using a copper tube as an outer conductor are provided. A small-diameter coaxial cable can be obtained without deteriorating the characteristics of the insulator.

  FIG. 1 shows a coaxial cable manufactured by the method of the present invention. The coaxial cable A has an outer diameter of about 2 to 3 mm, and includes an inner conductor 1 made of copper wire, an insulator 2 made of a resin material, and an outer conductor 3 made of copper tape.

  This coaxial cable manufacturing method includes a tape winding process, a core insertion process, a pipe making process, a welding process, a sinking process, an annealing process, and a jacket forming process, as shown in the process diagram of FIG. The procedure will be described below.

  As shown in FIG. 3, the copper tape 3a which becomes the outer conductor 3 is wound in a cylindrical shape, and a core 5 which encloses the inner conductor 1 with an insulator 2 in advance is inserted into the copper tape wound body 3b. Here, a fluororesin material is used for the insulator 2. The continuous use temperature of the fluororesin material is 200 ° C to 260 ° C. In the present invention, among fluororesin materials, in particular, a fluororesin material whose continuous use temperature is about the upper limit (250 ° C. to 260 ° C.) can be suitably used.

  Next, while inserting the wound body 3b into the core 5, the wound body 3b is further formed into a tubular shape, and both end edges of the copper tape 3a are attached.

  Thereafter, as shown in FIG. 4, the butted edges of the copper tape 3a are welded together by laser processing or the like to form a coaxial cable body 6 in which the core 5 is surrounded by the outer conductor 3 made of a welded tube.

  As shown in FIG. 5, the coaxial cable body 6 obtained in this way is inserted into a die 7 and subjected to sinking (squeezing) processing, and the diameter is reduced to a predetermined outer diameter.

  Next, the sinked coaxial cable body 6a is annealed at a temperature of about 240 ° C. to 250 ° C. for 2 hours in an inert gas atmosphere.

  Hereinafter, technical considerations of the present invention will be described. FIG. 6 shows the mechanical characteristics of a sample obtained by subjecting a welded pipe having an outer diameter of 3.8 mm and a thickness of 0.25 mm formed by pipe-forming and welding of copper tape to various diameters. The cross-sectional reduction rate test results are shown. As can be seen from this test result, it can be recognized that “elongation” is remarkably reduced by mild drawing and that “tensile strength” is increased as the degree of drawing is increased (the cross-sectional reduction ratio is increased). That is, when sinking is performed on the welded pipe, it becomes hard due to residual stress and the flexibility is reduced.

  Therefore, in the present invention, the flexibility of the welded pipe is recovered by reducing or eliminating the residual stress, which is the cause of the decrease in flexibility, by annealing, and FIG. 7 is based on the above process. 3 shows the results of preparing three samples of the manufactured coaxial cable body 6a of various sizes, annealing at various temperatures, and measuring the hardness of the outer conductor 3 of each sample. Moreover, the transition in which the average value of a measured value changes corresponding to the annealing temperature is graphed in FIG. The annealing time was 2 hours, and the hardness was measured using a micro Vickers hardness meter under the condition of 100 g / 5 sec.

  According to this measurement result, almost no change in the hardness of the outer conductor 3 is observed in the annealing process at 200 ° C. for 2 hours, but in the sample subjected to the sinking process, annealing is performed in the region of 200 ° C. or higher. By the treatment, a decrease in hardness appears remarkably, and a sample having a smaller outer diameter (larger cross-sectional reduction ratio) is softened at a lower temperature. This is because the strain energy based on the residual stress becomes the driving force for softening, so that the larger the processing, the more strain energy is accumulated and the more strain energy is released even at low temperatures, and the softening is promoted. Presumed to be.

  In the present invention, the cross-sectional reduction ratio is set to 30% or more and less than the fracture limit (about 40 to 50% for copper), and the annealing temperature is set to about 240 ° C. to 250 ° C. Thereby, the softness | flexibility in the coaxial cable which used the seamless copper pipe for the outer conductor, ie, the softness | flexibility equivalent to the hardness (80-70Hv) in an outer conductor, can be acquired. Furthermore, in such a manufacturing method, as the insulator 2, a fluororesin material having a continuous use temperature higher than the annealing temperature (about 240 ° C. to 250 ° C.) (that is, the continuous use temperature is near its upper limit (250 ° C. to 260 ° C. As a result, a coaxial cable having an outer conductor made of a copper tape wound body has the same flexibility as a coaxial cable using a seamless copper tube as the outer conductor ( The hardness (80 to 70 Hv) of the outer conductor can be obtained without deteriorating the characteristics of the insulator 2.

It is a perspective view of a coaxial cable. It is process drawing of the coaxial cable manufacturing method which concerns on this invention. It is a schematic perspective view which shows a copper tape winding process and a core insertion process. It is a schematic perspective view which shows a pipe making process and a welding process. It is a schematic perspective view which shows a sinking process. It is a graph which shows the mechanical characteristic and cross-sectional reduction rate of the welded pipe which passed through the sinking process. It is a graph which shows the measurement result of the annealing temperature and the hardness of an external conductor. It is a characteristic diagram which shows transition of the hardness of the outer conductor with respect to annealing temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner conductor 2 Insulator 3 Outer conductor 3a Copper tape 3b Winding body 5 Core 6 Coaxial cable body before sinking 6a Coaxial cable body after sinking

Claims (2)

A step of forming a wound body by winding a copper tape as an outer conductor into a cylindrical shape;
Inserting a core formed by coating an inner conductor with an insulator into the wound body;
A tube forming step of forming the wound body into which the core is inserted into a tubular shape;
A welding step of welding the butt end of the copper tape formed into a tubular shape to form a coaxial cable body; and
A sinking step of narrowing down the coaxial cable body to a predetermined diameter,
An annealing step of heating the coaxial cable body that has undergone the sinking step over a predetermined time,
Using a fluororesin material for the insulator, setting the cross-sectional reduction rate in the sinking step to 30% or more and less than the copper fracture limit, and setting the annealing temperature to about 240 ° C. to 250 ° C.,
A method for manufacturing a coaxial cable. Performing the annealing treatment in an inert gas atmosphere,
The method for manufacturing a coaxial cable according to claim 1.

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