JP6164844B2 - Insulated wire, coaxial cable and multi-core cable - Google Patents

Description

  The present invention relates to an insulated wire, a coaxial cable, and a multi-core cable used for telecommunication equipment, information equipment, industrial machinery, vehicle wiring, and the like.

  Insulated wires and coaxial cables are used for wiring within devices or between devices, within machines, and within vehicles. Insulated wires are those in which the center conductor is covered with an insulator, and coaxial cables are usually covered with an insulator in the center conductor, the outer periphery of the insulator is covered with an external conductor, and the outside is covered with a protective covering. Depending on the application, the cable has an outer diameter of 0.25 mm to several mm. In order to obtain good electrical characteristics with a small diameter, these electric wires and the like are required to make the dielectric constant of the insulator covering the outer periphery of the center conductor as small as possible.

  For this reason, the central conductor is covered with an insulator having 6-9 cross-sectional circular or elliptical voids continuous in the longitudinal direction, and an outer conductor is arranged on the outer periphery of the insulator to provide a low dielectric constant coaxial cable. Is known (see, for example, Patent Document 1). A coaxial cable having a fan-shaped cross section of the gap is also known (see, for example, Patent Document 2).

International Publication No. 2010/035762 Japanese Patent Publication: JP2009-110975A

As described above, when the gap is formed in the insulator, the dielectric constant of the insulator can be reduced and good electrical characteristics can be obtained.
However, when the void ratio of the void portion is too large, the withstand voltage between the center conductor and the outer conductor is lowered. In addition, if the porosity is large, the strength may be reduced. Especially, if the cross section of the air gap is fan-shaped, the air gap will be easily deformed by bending, and the cable will be crushed by external pressure to ensure stable transmission characteristics. May become difficult.

  An object of the present invention is to provide an insulated wire, a coaxial cable, and a multi-core cable capable of reducing the dielectric constant of an insulator and obtaining good electrical characteristics with a small diameter without causing a decrease in withstand voltage and a decrease in strength. It is to provide.

The insulated wire of the present invention that can solve the above-mentioned problem is an insulated wire in which the central conductor is covered with an insulator having a gap portion continuous in the longitudinal direction,
The gap is formed in a circular or elliptical cross section, 6 to 8 gaps are evenly arranged on the insulator, and the area and insulator of all the gaps in the cross section perpendicular to the cable length direction When the ratio of the area of the void portion to the sum of the areas is defined as the void ratio, the void ratio of all the void portions is 18% or more and 35% or less.
The coaxial cable of the present invention is a coaxial cable in which a center conductor is covered with an insulator having a continuous gap in the longitudinal direction, and an outer conductor is arranged on the outer periphery of the insulator,
The gap is formed in a circular or elliptical cross section, 6 to 8 gaps are evenly arranged on the insulator, and the area and insulator of all the gaps in the cross section perpendicular to the cable length direction When the ratio of the area of the void portion to the sum of the areas is defined as the void ratio, the void ratio of all the void portions is 18% or more and 35% or less.

  In the insulated wire or coaxial cable of the present invention, the insulator is preferably made of a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer.

  The multi-core cable of the present invention is characterized in that a plurality of the above insulated wires or coaxial cables are accommodated.

  According to the present invention, since 6 to 8 voids having a circular or oval cross section are evenly arranged in the insulator, the dielectric constant of the insulator can be reduced and good electrical characteristics can be obtained with a small diameter. it can. Further, by setting the porosity to 18% or more and 35% or less, it is possible to reliably ensure the withstand voltage between the center conductor and the outer conductor without causing a decrease in strength.

It is sectional drawing of the coaxial cable which shows one Embodiment of this invention. It is a fragmentary perspective view of the extruder used when manufacturing the coaxial cable which concerns on this invention.

Hereinafter, examples of embodiments of a coaxial cable and a multi-core cable according to the present invention will be described with reference to the drawings.
As shown in FIG. 1, the coaxial cable 11 according to this embodiment includes a central conductor 12 covered with an insulator 13, an outer conductor 15 arranged on the outer periphery of the insulator 13, and an outer cover 16 covered with the outer conductor 15 for protection. This is the configuration. The central conductor 12 and the insulator 13 of the coaxial cable 11 have the same configuration in the insulated wire of the present invention.

  The insulator 13 has eight voids 14 that are continuous in the longitudinal direction. These voids 14 are formed in a circular cross section with an outer diameter D3, and are uniformly arranged in the circumferential direction on the insulator 13. Further, the center conductor 12 and the insulator 13 and the outer conductor 15 and the insulator 13 are in close contact.

  The center conductor 12 is formed of a single wire or a stranded wire made of silver-plated or tin-plated annealed copper wire or copper alloy wire. In the case of a stranded wire, for example, an outer diameter D2 obtained by twisting seven strand conductor diameters of 0.030 mm is 0.090 mm (equivalent to AWG (American Wire Gauge) # 40), 7 having an outer diameter D2 of 0.075 mm (equivalent to AWG # 42) is used.

A fluororesin made of PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) is used for the insulator 13, and the insulator 13 is formed by extruding this fluororesin. PFA has a low dielectric constant among insulating resins (relative dielectric constant at 1 MHz is about 2.1), so that the insulator can be made thin while keeping the same capacitance as compared to the case of using other resins. .
The insulator 13 has an outer diameter D1 of about 0.2 mm, and has a relatively high capacitance of 90 to 120 pF / m.

  The external conductor 15 is a bare copper wire (an annealed copper wire or a copper alloy wire), a silver-plated or tin-plated anodized copper wire or a copper alloy wire having the same thickness as that of the wire conductor used for the center conductor 12. It is formed on the outer periphery with a horizontal winding or a braided structure. Further, in order to improve the shielding function, a metal foil tape may be provided in the layer immediately outside the outer conductor 15.

The jacket 16 is formed by extruding a resin material such as a fluororesin or winding a resin tape such as a polyester tape.
The outer diameter of the coaxial cable 11 that is the outer diameter of the jacket 16 is about 0.31 mm.

  The coaxial cable 11 is used for antenna wiring, wiring for connecting a liquid crystal display (LCD) and a central processing unit (CPU), or the like for a mobile phone or a notebook personal computer, or for connecting a sensor and a device. It is often used as a core cable, and the miniaturization and thinning of these terminal devices require a reduction in the diameter of the coaxial cable and a reduction in the diameter of the multi-core cable.

  The coaxial cable 11 needs to have a predetermined impedance (50Ω, 75Ω, or 80 to 90Ω), and has a diameter as small as possible as long as this is realized. For this purpose, it is necessary to reduce the dielectric constant of the insulating layer between the center conductor 12 and the outer conductor 15. In the present embodiment, by providing the gap portion 14 in the insulator 13, the dielectric constant of the insulator 13 can be reduced, and the coaxial cable 11 can have a small diameter and good electrical characteristics.

  However, if the void ratio of the gap portion 14 is too large, the withstand voltage between the center conductor 12 and the outer conductor 15 may be reduced. In addition, since the insulator 13 is thin with a small diameter, the strength is reduced, and it may not be able to withstand external pressure and bending applied to the cable.

  For this reason, in this embodiment, when the ratio of the void portion 14 to the sum of the area of all the void portions 14 and the area of the insulator 13 is defined as the void ratio, the void ratio of all the void portions 14 is 18%. By setting the ratio to 35% or less, the withstand voltage between the center conductor 12 and the outer conductor 15 is reliably ensured without causing a decrease in strength. In addition, since the eight gaps 14 formed in a circular cross section are uniformly arranged on the insulator 13 made of PFA, high strength can be maintained while reducing the diameter and reducing the dielectric constant of the insulator 13. Can do.

Thereby, in the case of a predetermined capacitance (for example, 100 pF / m) with the same outer diameter, the center conductor 12 can be thickened by thinning the insulator 13, and the transmission efficiency is improved by reducing the conductor resistance. Can be achieved. For example, even with AWG # 42, the center conductor 12 of AWG # 40 can be used.
If the outer diameter of the central conductor 12 is the same, the outer diameter of the coaxial cable 11 can be reduced by reducing the thickness of the insulator 13.
Even if the insulated wire does not have the external conductor 15, the same effect as that of the coaxial cable 11 can be obtained by configuring the insulator 13 as described above.

  In the coaxial cable 11 of the above embodiment, the eight gaps 14 are formed in the insulator 13, but the number of the gaps 14 is not limited to eight and may be six or seven. Moreover, although the case where the cross-sectional circle-shaped space | gap part 14 was formed was illustrated in the said embodiment, the space | gap part 14 may be cross-sectional elliptical shape. The same applies to insulated wires.

  Moreover, although the said coaxial cable 11 was demonstrated in the example of the single core wire, it is good also as a multi-core cable which bundled this coaxial cable 11 or several insulated wires. The multi-core cable may include only a coaxial cable, may include only an insulated wire, or may include both. Furthermore, it is good also as a multi-core coaxial cable which shielded the coaxial cable or the insulated wire with the common shield conductor.

As shown in FIG. 2, the coaxial cable 11 or the insulated wire can be manufactured using an extruder 30 in which a die 31 and a point 41 are combined.
A member 45 having a columnar outer shape is provided at the point 41 by the number of the gap portions 14 and is combined with the die 31 having the circular outlet 33 to push out the resin from between the point 41 and the die 31 (channels 51 and 52). The central conductor 12 is pulled out from the central hole 44 of the cylindrical portion 43 of the point 41. The extruded resin is coated on the central conductor 12. The resin may be coated by a pulling-down method in which the resin exiting the die 31 is stretched to reduce the diameter. Resin does not flow through the cylindrical member 45, and this portion becomes the gap portion 14. If a vent hole 46 is provided in the member 45, the void portion 14 through which the resin does not flow is secured in the resin extruded from the die 31, and the cross section thereof becomes circular or elliptical.

  In the extruder 30 described above, the porosity of the insulator 13 can be easily adjusted by the diameter of the columnar member 45 provided at the point 41. In addition, the thing with a low porosity has a high freedom degree of the combination of the die | dye 31 and the point 41, and a draw-down rate, when producing rather than the thing with a high porosity, and it is easy to obtain a good product.

  In order to evaluate the above-described coaxial cable according to the present invention, an example product and a comparative example product of the present invention were produced and tested. In the test products of Examples 1 and 2 and Comparative Example 1, a stranded wire having an outer diameter of 0.09 mm obtained by twisting seven tin-plated copper alloy wires having an outer diameter of 0.03 mm is used as the central conductor. A fluororesin (PFA) was extrusion coated to form an insulator having an outer diameter of 0.20 mm. When extruding the insulator, the cylindrical member 45 that forms the void as shown in FIG. 2 is used to uniformly form eight voids having a circular section in the longitudinal direction in the insulator. did. As the outer conductor, a tin-plated annealed copper wire having an outer diameter of 0.03 mm was horizontally wound, and a jacket made of polyester tape was formed thereon to form an AWG # 40 coaxial cable having an outer diameter of 0.31 mm. The overall porosity of the voids in the insulator is 18% (capacitance 110 pF / m) in Example 1, 35% (capacitance 100 pF / m) in Example 2, and 40% (static) in Comparative Example 1. The capacitance was 95 pF / m).

  Further, as Comparative Example 2, a coaxial cable having no void portion (void ratio 0%) was produced. In Comparative Example 2, a stranded wire having an outer diameter of 0.075 mm obtained by twisting seven silver-plated copper alloy wires having an outer diameter of 0.025 mm is used as the central conductor, and fluororesin (PFA) is extrusion coated thereon. Thus, an insulator having an outer diameter of 0.20 mm was obtained. As the outer conductor, a tin-plated annealed copper wire having an outer diameter of 0.03 mm was wound horizontally, and a jacket made of polyester tape was formed thereon to form an AWG # 42 coaxial cable having an outer diameter of 0.31 mm. The capacitance was 110 pF / m.

The coaxial cable of each test product was subjected to the following test three times, and each coaxial cable was evaluated.
(1) Withstand voltage test An AC voltage was applied between the center conductor and the outer conductor, and a voltage value was measured when the insulator was broken and the center conductor and the outer conductor were short-circuited.
(2) Dynamic cut-through From the top of the outer sheath of the coaxial cable, it is crushed by applying pressure with a round blade, and the load when the center conductor and the outer conductor are short-circuited is measured. The round blade was made of SUS and the tip diameter r was 1 mm.

  The test results are shown in Table 1. In addition, the numerical value of Table 1 is an average value of a test result of every 3 times.

  In the coaxial cable of Example 1 in which the void ratio of the void portion was 18%, the withstand voltage was 5.6 kV on average and the load of dynamic cut-through was 27.7 N on average. Thus, the coaxial cable of Example 1 was found to have sufficient withstand voltage and strength, and the reliability evaluation was good (◯).

  In the coaxial cable of Example 2 in which the void ratio of the void portion was 35%, the withstand voltage was an average value of 4.4 kV, and the dynamic cut-through load was an average value of 25.2 N. As described above, the coaxial cable of Example 2 was found to have sufficient withstand voltage and strength, and the evaluation of reliability was good (◯).

  In the coaxial cable of Comparative Example 1 in which the void ratio of the void portion was 40%, the withstand voltage was 2.5 kV on average and the load of dynamic cut-through was 19.3 N on average. Thus, in the coaxial cable of Comparative Example 1, it was recognized that both the withstand voltage and the strength were insufficient, and the reliability evaluation was poor (x).

The coaxial cable of Comparative Example 2 in which the void ratio of the void portion is 0% has the same capacitance as that of Example 1. The withstand voltage and the load of dynamic cut-through are the same as in Example 1. However, the coaxial cable of the comparative example 2 is AWG and is one size smaller than the coaxial cable of the first embodiment in terms of allowable current and conductor resistance.
When a coaxial cable without a gap is produced using a central conductor having the same dimensions as in Example 1, the outer diameter is 0.34 mm, the outer diameter is increased by about 10%, and does not satisfy the demand for reducing the diameter. .

  In the above embodiment, the coaxial cable of AWG # 40 was evaluated. As a result of conducting a withstand voltage test and a dynamic cut-through test on the coaxial cable of small diameter (AWG # 42), the void ratio of the entire void portion was 18%. In the case of 35%, the evaluation was good.

  Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application (Japanese Patent Application No. 2010-268036) filed on Dec. 1, 2010, the contents of which are incorporated herein by reference.

11: coaxial cable, 12: central conductor, 13: insulator, 14: gap, 15: outer conductor

Claims (3)

The central conductor is a coaxial cable covered with an insulator having a gap continuous in the longitudinal direction, and an outer conductor is disposed on the outer periphery of the insulator,
The center conductor has an outer diameter of 0.09 mm or less,
The insulator is a fluororesin;
The capacitance is 90-120 pF / m,
Withstand voltage is 4.4 kV or more,
The gap is formed in a circular or elliptical cross section, 6 to 8 gaps are evenly arranged on the insulator, and the area and insulator of all the gaps in the cross section perpendicular to the cable length direction A coaxial cable characterized in that when the ratio of the area of the void portion to the sum of the areas is defined as the void ratio, the void ratio of all the void portions is 18% or more and 35% or less. The coaxial cable according to claim 1,
The coaxial cable is characterized in that the insulator is made of a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer.   A multi-core cable comprising a plurality of the coaxial cables according to claim 1 or 2.

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