JP2008293862A - Insulated electrical wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulated electrical wire capable of being thinned, reduced in change of the external form, and stabilized in electric property. <P>SOLUTION: The insulated electrical wire 10 is comprised of a center conductor 11; and an insulating coating layer 12 disposed on an outer circumference of the center conductor 11. The insulating coating layer 12 has air gaps 13 with part of the outer circumference of the center conductor 11 as one side. The air gaps are preferably provided by at least three, thereby reducing a relative permittivity of the insulating coating layer, which enables the insulated electrical wire to be thinned, reduced in change of the external form, and stabilized in electric property. The insulating coating layer is preferably made of a fluorine contained resin selected from PFA, FEP, and PTFE. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an insulated wire including a center conductor and an insulating coating layer provided on the outer periphery of the center conductor.

  Currently, there is a demand for thinner cables due to the smaller and thinner information terminals. As the cable diameter becomes smaller, it is necessary to reduce the dielectric constant of the insulating coating layer. Since high-frequency data signals flow on the surface layer of the cable, in order to obtain good electrical characteristics, it is important to reduce the dielectric constant of the insulating coating layer formed on the outer periphery of the center conductor as much as possible. Basically, nothing is ideally placed around the center conductor, but the center conductor cannot be protected without a coating layer. Dielectric constant resin is used. In addition, foaming technology is also used to lower the apparent dielectric constant.

However, foam extrusion technology is difficult to ensure extrusion stability, especially when extruding small-diameter products, because the outer diameter of the insulation coating layer slightly changes, which is also one of the factors that hinder electrical characteristics. It was. As a countermeasure, a method of forming an insulating coating layer having a continuous void in the longitudinal direction has been proposed (see, for example, Patent Document 1).
JP 2003-249129 A

  As in the above conventional example, the formation of an insulating coating layer having continuous voids in the longitudinal direction by extrusion molding is difficult to ensure a uniform void area as in the case of foaming extrusion technology. However, there was a problem that the external shape was changed.

  Therefore, in view of the above problems, an object of the present invention is to provide an insulated wire that can be further reduced in diameter, has little fluctuation in outer shape, and has stable electrical characteristics.

  A feature of the present invention is an insulated wire including a central conductor and an insulating coating layer provided on the outer periphery of the central conductor, and the insulating coating layer has a gap portion having a part of the outer periphery of the central conductor as one side. The gist is that the insulated wire is provided along the longitudinal direction.

  According to the insulated wire according to the feature of the present invention, the diameter can be further reduced, the external shape fluctuation is small, and the electrical characteristics can be stabilized.

  In the insulated wire according to the feature of the present invention, the insulating coating layer is preferably made of a fluororesin selected from PFA, FEP, and PTFE.

  According to this insulated wire, the dielectric constant of the insulating coating layer can be lowered.

In the insulated wire according to the feature of the present invention, it is preferable that at least three or more void portions are provided.

  According to this insulated wire, the dielectric constant of the insulating coating layer can be further reduced, and the electrical characteristics can be stabilized.

  In the insulated wire according to the feature of the present invention, the cross-sectional area of the gap is preferably 10% or more of the cross-sectional area of the insulating coating layer in the cross section crossing the insulating coating layer.

  According to this insulated wire, the dielectric constant of the insulating coating layer can be further reduced, and the electrical characteristics can be stabilized.

  According to the present invention, it is possible to provide an insulated wire that can be further reduced in diameter, has little fluctuation in outer shape, and has stable electrical characteristics.

  Next, embodiments of the present invention will be described with reference to the drawings. In the descriptions of the following aspects, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(Insulated wire structure)
As shown in FIG. 1, the insulated wire 10 according to the present embodiment includes a center conductor 11 and an insulating coating layer 12 provided on the outer periphery of the center conductor 11. The center conductor 11 is made of, for example, copper, and may be a conductive wire that is tin-plated or silver-plated. The center conductor 11 is preferably a stranded wire because it has flexibility, but may be a single wire.

  The insulating coating layer 12 is made of fluorine resin such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), PTFE (polytetrafluoroethylene), or PP. (Polypropylene), PE (polyethylene) and other olefin resins. The relative dielectric constant of such an insulating coating layer 12 is 2.5 or less.

  Further, the insulating coating layer 12 is provided with a gap 13 having a part of the outer periphery of the center conductor 11 as one side. The gap 13 has a rectangular shape in FIG. In addition, in FIG. 1, although the space | gap part 13 is made into the rectangular shape, another polygonal shape may be sufficient. For example, as shown in FIG. 2, the shape of the gap 13 may be a triangular shape that narrows from the side in contact with the center conductor 11 toward the outside of the insulated wire.

  Moreover, it is preferable that the space | gap part 13 is provided at least 3 or more places. The cross-sectional area of the gap 13 is preferably 10% or more of the cross-sectional area of the insulating coating layer 12, and more preferably 35 to 60%. Furthermore, it is preferable that the length from the central conductor 11 of the gap portion 13 toward the outside of the insulated wire is 1/3 or more of the outer diameter of the insulating coating layer.

  Further, in order to form the plurality of gaps 13 in the insulating coating layer 12, a die having a center hole for insertion of the center conductor 11 and a plurality of holes for gaps adjacent to the outer periphery of the center hole is used. The resin can be formed by extruding molten resin from the center hole and the gap hole while inserting the center conductor 11 into the center hole.

  As a similar technique for obtaining an extruded product having the gap 13 as described above, for example, there is a deformed hollow fiber, and a die having a similar structure is manufactured by using such a hollow fiber die processing technique. If it does, it can be used for manufacture of the insulated wire which concerns on this embodiment.

(Cable structure)
Next, a specific example of a cable using the above-described insulated wire will be described below.

  FIG. 3 shows a coaxial cable in which an outer conductor 14 is disposed on the outer periphery of an insulated wire having a triangular gap 13 shown in FIG. 2 and an outer insulating layer 15 is disposed on the outer periphery of the outer conductor 14. The outer conductor 14 is formed by winding a metal tape, a partial assembly, or a corrugated layer. The external insulating layer 15 is preferably made of a thermoplastic resin, a thermosetting resin, or the like and is made of a metal-platable material. 3 shows the coaxial cable using the insulated wire having the triangular gap 13 shown in FIG. 2, the insulated wire having the rectangular gap 13 shown in FIG. 1 may be used. Of course.

  FIG. 4 shows a cable (so-called Twinax) having a parallel two-core structure in which two insulated wires having the rectangular gap portion 13 shown in FIG. 1 are collected and a shielding layer 17 is arranged on the outer periphery thereof. The center conductor 11 may be a single wire or a stranded wire. In addition to the two central conductors 11 arranged in parallel at a predetermined interval, the signal line includes a drain line 16. The drain line 16 may be a conductive wire made of, for example, copper and subjected to tin plating or silver plating. The shielding layer 17 is a press-wound layer made of a laminate tape in which a metal such as aluminum is vapor-deposited on one side of a resin tape (PET tape or the like) or a metal tape is laminated. 4 shows the two-core cable using the insulated wire having the rectangular gap portion 13 shown in FIG. 1, the insulated wire having the triangular gap portion 13 shown in FIG. 2 may be used. Of course.

(Function and effect)
The insulating coating layer 12 of the insulated wire 10 according to the present embodiment is provided with a gap 13 having a part of the outer periphery of the center conductor 11 as one side. By providing such a gap portion 13, it is possible to reduce the diameter and reduce the variation in the outer shape. That is, since one side of the gap 13 according to the present embodiment is in contact with the center conductor 11, a closed gap that does not contact the center conductor 11 as in Patent Document 1 is manufactured by extrusion molding. Compared to the above, it is possible to reduce crushing after extrusion and to reduce fluctuations in the outer shape. Furthermore, in this embodiment, the insulated wire 10 having the gap 13 is manufactured by profile extrusion molding. According to this, since the shape does not change after passing through the die of the molding apparatus as in the foam extrusion molding, the variation of the outer shape is suppressed as compared with the foam extrusion molding. Moreover, the dielectric constant of the insulating coating layer 12 is lowered by providing the gap portion 13. Electrical characteristics can be stabilized.

  The insulating coating layer 12 is preferably made of a fluororesin selected from PFA, FEP, and PTFE. When an insulating coating layer having such a composition is used, the relative dielectric constant can be further reduced.

  Moreover, it is preferable that the space | gap part 13 is provided at least 3 or more places. According to such an insulated wire, the dielectric constant of the insulating coating layer can be further reduced, and the electrical characteristics can be stabilized.

  Further, in the cross section crossing the insulating coating layer 12, the cross sectional area of the gap 13 is preferably 10% or more of the cross sectional area of the insulating coating layer 12. According to such an insulated wire, the dielectric constant of the insulating coating layer can be further reduced, and the electrical characteristics can be stabilized.

  Moreover, the outer insulating layer 15 of a coaxial cable can be formed by metal plating by using a metal-platable material. According to such a coaxial cable, it is possible to reduce the diameter as compared with extrusion molding.

(Other embodiments)
Although specific examples of the present invention have been described according to the above-described embodiments, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, in FIG. 4, the cable structure in which the drain line 16 exists inside the shielding layer 17 has been described, but the drain line 16 may be disposed outside the shielding layer 17. The drain line 16 is a ground line and may have the same potential as the shielding layer 17.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

  Hereinafter, the insulated wire according to the present invention will be specifically described with reference to examples. However, the present invention is not limited to those shown in the following examples, and can be implemented with appropriate modifications within a range not changing the gist thereof.

(Example)
As the coaxial cable according to the example of the present invention, the coaxial cable shown in FIG. 3 was manufactured using the insulated wire having the triangular gap 13 shown in FIG. Specifically, a silver-plated annealed copper stranded wire was used as the central conductor 11, and a low density polyethylene of MFR 0.1 (g / 10 min) (measurement conditions: 190 ° C., 2.16 kg) was used as the insulating coating layer 12. . Further, a braided copper wire braid was used as the outer conductor 14, and polyethylene was used as the outer insulating layer 15. At this time, in the cross section crossing the insulating coating layer 12, the cross-sectional area of the gap 13 was 60% of the cross-sectional area of the insulating coating layer 12. The design values of other coaxial cables are as shown in Table 1.

(Comparative example)
As a coaxial cable according to a comparative example of the present invention, a coaxial cable using a conventional foam structure for an insulating coating layer was produced. Specifically, 0.3 wt% of boron nitride (BN) was added to the foam nucleating agent, and foaming was gas foaming with nitrogen gas. The foaming degree at this time was 60%. About the composition of the other coaxial cable, it was the same as that of an Example. The design values of other coaxial cables are as shown in Table 1.

(Evaluation)
About the coaxial cable which concerns on an Example and a comparative example, VSWR was measured. The VSWR (Voltage Standing Wave Ratio) is a voltage standing wave ratio, and is one of indexes indicating high-frequency characteristics of circuits and cables. Specifically, it is the degree that a part of the signal is reflected on the circuit when a high-frequency signal passes through the device. When this value is 1, it is an ideal state where there is no reflection at all, and the larger the reflection, the larger the value and the greater the signal loss. Devices that handle high-frequency signals are required to have this value as low as possible. One standard is that the VSWR value of an antenna or the like is 1.5 or less (the reflected power is 4% or less).

  The standing wave refers to a wave whose reflected wave interferes with the original wave and changes only the amplitude without changing the node or antinode, and the state of reflection (impedance: resistance value) depending on the magnitude of this amplitude Can know. For example, the degree of matching of impedance between the cable and the antenna is indicated by VSWR.

  Here, the VSWR value of the coaxial cable according to the example was 1.05, and the VSWR value of the coaxial cable according to the comparative example was 1.10 (not shown in Table 1).

  As described above, it was proved that the coaxial cable according to the example having the gap portion 13 has less variation in outer shape and stable electrical characteristics as compared with the comparative example.

It is sectional drawing of the insulated wire which concerns on embodiment (the 1). It is sectional drawing of the insulated wire which concerns on embodiment (the 2). It is sectional drawing of the coaxial cable which concerns on embodiment. It is sectional drawing of the two-core cable which concerns on embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Insulated electric wire 11 ... Center conductor 12 ... Insulation coating layer 13 ... Air gap part 14 ... External conductor 15 ... External insulating layer 16 ... Drain wire 17 ... Shielding layer

Claims (4)

An insulated wire comprising a center conductor and an insulating coating layer provided on the outer periphery of the center conductor,
The insulated wire is characterized in that a gap portion having a part of the outer periphery of the central conductor is provided along the longitudinal direction in the insulating coating layer.   The insulated wire according to claim 1, wherein the insulating coating layer is made of a fluororesin selected from PFA, FEP, and PTFE.   The insulated wire according to claim 1 or 2, wherein at least three or more gaps are provided.   The insulation according to any one of claims 1 to 3, wherein a cross-sectional area of the gap portion is 10% or more of a cross-sectional area of the insulating coating layer in a cross section traversing the insulating coating layer. Electrical wire.

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