JP6009253B2 - Coaxial cable for high-frequency power transmission - Google Patents

Description

  The present invention relates to a coaxial cable for high frequency power transmission for transmitting high frequency power.

  As the coaxial cable 101, as shown in FIG. 4, an inner conductor 102, an insulator (dielectric) 105, an outer conductor 107, and a jacket layer 110 are coaxially arranged, and the inner conductor 102 is made of silver-plated copper. The thing made into the clad steel wire is proposed (for example, refer to patent documents 1).

JP 9-139122 A

  However, in the conventional coaxial cable 101 shown in Patent Document 1, since the inner conductor 102 is a silver-plated copper clad steel wire, increasing the diameter of the inner conductor 102 increases the weight and increases the hardness against bending. There is a problem that the handling property is extremely lowered.

  In addition, since silver plating is costly, the cost of the coaxial cable 101 is increased, and the use is limited. Therefore, there is a problem that versatility is reduced.

  Further, when transmitting high-frequency power, an alternating magnetic field in a direction perpendicular to the direction in which the alternating current flows is generated in the external conductor 107, and a so-called skin effect in which the alternating current flows through the surface of the external conductor 107, There is a problem that the conductor resistance of the outer conductor 107 increases and the transmission efficiency decreases.

  The present invention aims to solve such problems. That is, an object of the present invention is to provide a coaxial cable for high-frequency power transmission that can improve handleability, reduce costs, and improve transmission efficiency.

In order to solve the above problems and achieve the object, a coaxial cable for high-frequency power transmission according to the present invention includes an inner conductor, an insulator provided on the outer periphery of the inner conductor, and an external provided on the outer periphery of the insulator. A coaxial cable for high-frequency power transmission having a conductor and a jacket layer provided on the outer periphery of the outer conductor and used for transmitting high-frequency power of several tens to several hundreds of MHz, wherein the inner conductor is It is a copper clad aluminum wire provided with a copper coating on the outer periphery of an aluminum core wire, the outer conductor is a copper braided wire obtained by braiding a plurality of copper strands, the outer diameter of the inner conductor and the inner diameter of the outer conductor The ratio of the cross-sectional area of the plurality of copper strands to the cross-sectional area perpendicular to the axis is 1. 3 to 1.5 times It is characterized.

  According to the coaxial cable for high-frequency power transmission of the present invention, by using a copper clad aluminum wire as an inner conductor, the inner conductor can be made lighter than when a steel wire is used.

  Moreover, by using the copper clad aluminum wire as the inner conductor, the inner conductor can be made more flexible than when a steel wire is used.

  As described above, the inner conductor can be made lighter and more flexible than the case where a steel wire is used, so the coaxial cable for high-frequency power transmission can be made lighter and made flexible. .

  Further, by reducing the weight and flexibility of the high-frequency power transmission coaxial cable, flexibility, bending resistance and the like can be improved, and the high-frequency power transmission coaxial cable can be improved.

  Moreover, by using the copper clad aluminum wire as an internal conductor, the cost can be reduced as compared with the case of using a steel wire plated with silver. Therefore, the cost of the high-frequency power transmission coaxial cable can be reduced.

  Thus, since the cost of the coaxial cable for high-frequency power transmission can be reduced, it can be used for various purposes as compared with the case of using a relatively expensive silver-plated copper-clad steel wire. Therefore, the versatility of the coaxial cable for high frequency power transmission can be improved.

  In addition, when high-frequency power is transmitted, an alternating current flows only on the inner peripheral surface of the outer conductor due to the skin effect, but a copper braided wire in which a plurality of copper strands are braided is used as the outer conductor. And by making the total cross-sectional area of the cross-section perpendicular to the axis of the plurality of copper wires 1.3 to 1.5 times the cross-sectional area of the cross-section perpendicular to the axis of the internal conductor, An equivalent alternating current can be passed through the outer conductor.

  In this way, since an alternating current equivalent to the alternating current flowing through the internal conductor can be passed through the external conductor, it is possible to suppress a decrease in transmission efficiency of the coaxial cable for high-frequency power transmission.

It is sectional drawing which shows the axial cross section of the coaxial cable for high frequency electric power transmission concerning one Embodiment of this invention. It is a figure which shows each performance of the handleability in the Example and comparative example of a coaxial cable for high frequency electric power transmission of this invention, cost reduction, and transmission efficiency. It is explanatory drawing for demonstrating the method of a bending test. It is sectional drawing which shows the axial cross section of the coaxial cable of a prior art example.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. The embodiments of the present invention described below are merely representative embodiments of the present invention, and the present invention is not limited to the embodiments. Therefore, the present invention can be implemented with various modifications within the scope not departing from the gist of the present invention, that is, those that can be easily conceived by those skilled in the art, substantially the same, and so-called equivalent ranges.

  FIG. 1 is a cross-sectional view schematically showing a cross section perpendicular to the axis of a coaxial cable 1 for high-frequency power transmission according to an embodiment of the present invention.

  As shown in FIG. 1, the coaxial cable 1 for high-frequency power transmission according to an embodiment of the present invention includes an inner conductor 2, an insulator 5, an outer conductor 7, and a jacket layer 10 arranged on a concentric circle. ing.

  The coaxial cable 1 for high-frequency power transmission has an internal conductor so as to have a predetermined characteristic impedance at the frequency (for example, several tens to several hundreds MHz) of the high-frequency power transmitted by the coaxial cable 1 for high-frequency power transmission. The ratio between the outer diameter of 2 and the inner diameter of the outer conductor 7 is set.

  The ratio between the outer diameter of the inner conductor 2 and the inner diameter of the outer conductor 7 is set so that the characteristic impedance is 50Ω when the frequency is 10 MHz, for example.

  The inner conductor 2 has a circular cross section perpendicular to the axis. The inner conductor 2 is a so-called copper clad aluminum wire (also referred to as a copper clad aluminum wire). A wire diameter R1 of the inner conductor 2 is formed larger than a wire diameter R2 of a copper element wire 8 of the outer conductor 7 described later. In the illustrated example, the wire diameter R1 of the inner conductor 2 is set to about 4 times the wire diameter R2 of the copper wire 8.

  The copper clad aluminum wire includes one aluminum core wire 3 and a copper coating 4 coated on the outer periphery of the aluminum core wire 3. In the copper clad aluminum wire, the outer peripheral surface of the aluminum core wire 3 and the inner peripheral surface of the copper coating 4 are diffusion-bonded by heat and pressure.

  Moreover, the copper clad aluminum wire covers the surface of the aluminum core wire 3 with the copper coating 4 so that the tensile strength is improved and the weight is reduced as compared with the copper wire and the steel wire. Further, the copper clad aluminum wire is covered with the copper coating 4 so that the surface of the aluminum core wire 3 can be covered by conventional soldering, and the connectivity is improved. Moreover, the flexibility of the copper clad aluminum wire is improved more than the copper wire or the steel wire due to the flexibility of the aluminum core wire 3.

  Moreover, the handleability of the coaxial cable 1 for high frequency power transmission is improved by making the inner conductor 2 lighter and more flexible and stronger than the case of using a copper wire or a steel wire.

  In addition, since the inner conductor 2 is formed of a copper clad aluminum wire, the cost can be reduced as compared with the case where a silver-plated steel wire is used, so that the high-frequency power transmission coaxial cable 1 is reduced in cost. Versatility is improved.

  The aluminum core wire 3 is formed in a cylindrical shape. The aluminum core wire 3 is made of aluminum or an alloy thereof. As aluminum, for example, hard aluminum, semi-hard aluminum, or soft aluminum can be used, and as aluminum alloy, for example, No. I aluminum alloy, high strength aluminum alloy, heat resistant aluminum alloy, high strength heat resistant aluminum alloy, etc. Can be used.

  The copper coating 4 is formed in a cylindrical shape. The copper coating 4 is made of copper or an alloy thereof. As copper, for example, hard copper, semi-hard copper, or soft copper can be used. As the copper alloy, for example, heat-resistant hard copper (copper-silver alloy), copper-zinc alloy, copper-tin alloy An alloy, beryllium copper, titanium copper, zirconium copper, iron-containing copper, Corson alloy, or the like can be used, such as a copper alloy that has been increased in strength without significantly impairing electrical conductivity and thermal conductivity.

  Further, the thickness of the copper coating 4 allows a required current to flow even if it is affected by the skin effect generated in the internal conductor 2 when high-frequency power is transmitted by the coaxial cable 1 for high-frequency power transmission. It is set to a thickness that can be used.

  The insulator 5 is provided on a concentric circle on the outer periphery of the inner conductor 2. The insulator 5 is formed in a cylindrical shape. The insulator 5 is made of, for example, a rubber-like elastic body such as a thermoplastic elastomer or a synthetic resin such as a polyethylene resin.

  The insulator 5 has a thickness set so as to have a predetermined characteristic impedance at the frequency of the high frequency power transmitted by the coaxial cable 1 for high frequency power transmission (for example, several tens to several hundreds of MHz). Yes.

  That is, the thickness of the insulator 5 is set so that the ratio between the wire diameter R1 of the inner conductor 2 and the inner diameter of the outer conductor 7 is, for example, a characteristic impedance of 50Ω when the frequency is 10 MHz.

  The insulator 5 may be a foamed insulator obtained by foaming the rubber-like elastic body or the synthetic resin. By foaming the insulator 5 in this way, the dielectric constant of the insulator 5 may be kept low, and the impedance of the coaxial cable 1 for high-frequency power transmission may be easily matched.

  Further, by keeping the dielectric constant low, the thickness of the insulator 5 can be reduced and the outer diameter of the coaxial cable 1 for high-frequency power transmission can be reduced.

  The outer conductor 7 is provided on a concentric circle on the outer periphery of the insulator 5. The outer conductor 7 includes a plurality of (26 in the illustrated example) copper element wires 8 arranged on a concentric circle at equal intervals. The outer conductor 7 is a copper braided wire formed in a tubular shape by braiding a plurality of copper strands 8.

  The copper wire 8 is formed in a cylindrical shape. The copper wire 8 is, for example, hard copper wire, semi-hard copper wire, annealed copper wire, copper-silver alloy wire, copper-zinc alloy wire, copper-tin alloy wire, beryllium copper wire, titanium copper wire, zirconium. Copper wire, iron-containing copper wire, Corson alloy wire, etc. are used.

  Further, the wire diameter R2 of the copper element wire 8 is smaller than the wire diameter R1 of the inner conductor 2. The wire diameter R2 of the copper wire 8 is such that the total cross-sectional area of the cross-section perpendicular to the axis of the plurality of copper wires 8 is 1.3 to 1.5 times the cross-sectional area of the cross-section perpendicular to the axis of the internal conductor 2. It is set to be.

  Thus, by setting the total cross-sectional area of the plurality of copper strands 8 in the cross section perpendicular to the axis to be 1.3 to 1.5 times the cross-sectional area of the cross section perpendicular to the axis of the internal conductor 2, An alternating current equivalent to the alternating current flowing through the conductor 2 can be passed through the inner peripheral surface of the outer conductor 7.

  Moreover, since an alternating current equivalent to the alternating current flowing through the inner conductor 2 can be passed through the inner peripheral surface of the outer conductor 7, it is possible to suppress a decrease in transmission efficiency of the coaxial cable 1 for high-frequency power transmission.

  In addition, when the copper element wire 8 is formed of a soft copper element wire, the conductivity can be improved. When the copper element wire 8 is formed of a copper alloy element wire, the mechanical strength can be improved. A coaxial cable 1 for high-frequency power transmission suitable for a location, wiring form, or application can be manufactured.

  Further, the number of copper wires 8 is not limited to 26 in the illustrated example, and the total of the cross-sectional areas of the plurality of copper wires 8 in the cross section perpendicular to the axis is 1 of the cross-sectional area in the cross section perpendicular to the axis of the internal conductor 2. Since it is only necessary to set to be 3 to 1.5 times, the number and the wire diameter R2 can be changed within a range in which the shield characteristics are not deteriorated.

  The jacket layer 10 is provided on a concentric circle on the outer periphery of the outer conductor 7. The jacket layer 10 covers the outer peripheral surface of the outer conductor 7. The jacket layer 10 is an exterior insulating layer formed in a cylindrical shape.

  The jacket layer 10 is formed of, for example, a soft polyvinyl chloride resin (soft PVC resin) as a thermoplastic elastomer. The jacket layer 10 can be formed of a known synthetic resin that is optimal for various applications such as weather resistance, water resistance, or heat resistance.

  As described above, the coaxial cable 1 for high-frequency power transmission according to an embodiment of the present invention includes an inner conductor 2, an insulator 5 provided on the outer periphery of the inner conductor 2, and an outer periphery of the insulator 5. A copper clad aluminum wire having an outer conductor 7 provided on the outer conductor 7 and a jacket layer 10 provided on the outer periphery of the outer conductor 7, wherein the inner conductor 2 is provided with a copper coating 4 on the outer periphery of the aluminum core wire 3. The outer conductor 7 is a copper braided wire formed by braiding a plurality of copper strands 8, and the total cross-sectional area of the plurality of copper strands 8 in the cross section perpendicular to the axis is the inner conductor 2. The cross-sectional area of the cross section perpendicular to the axis is 1.3 to 1.5 times.

  Thus, by forming the inner conductor 2 with a copper clad aluminum wire that is lighter and more flexible than a copper wire or a steel wire, the inner conductor 2 can be made lighter and more flexible.

  Further, by reducing the weight of the inner conductor 2 and making it flexible, the coaxial cable 1 for high-frequency power transmission can be made lightweight and flexible.

  Further, by reducing the weight and flexibility of the coaxial cable 1 for high-frequency power transmission, the flexibility and bending resistance of the coaxial cable 1 for high-frequency power transmission are improved, and the handling property of the coaxial cable 1 for high-frequency power transmission is improved. Can be improved.

  Moreover, by forming the inner conductor 2 with a relatively inexpensive copper clad aluminum wire, the cost can be reduced as compared with the case where a steel wire subjected to silver plating is used. Accordingly, the cost of the high-frequency power transmission coaxial cable 1 can be reduced.

  In addition, by reducing the cost of the coaxial cable 1 for high-frequency power transmission, it is possible to perform wiring at a place to be constructed at a low cost, thereby reducing cost limitations. Therefore, the versatility of the coaxial cable 1 for high-frequency power transmission can be improved.

  In addition, when high-frequency power is transmitted, an alternating current flows only on the inner peripheral surface of the outer conductor 7 due to the skin effect, but a copper braided wire in which a plurality of copper strands 8 are braided is used. By making the outer conductor 7 and the total cross-sectional area of the plurality of copper wires 8 in the cross section perpendicular to the axis 1.3 to 1.5 times the cross-sectional area of the cross section perpendicular to the axis of the inner conductor 7, An alternating current equivalent to the alternating current flowing through the external conductor 7 can be passed through the external conductor 7.

  In addition, by flowing an AC current equivalent to the AC current flowing through the inner conductor 2 through the outer conductor 7, it is possible to suppress a decrease in transmission efficiency of the coaxial cable 1 for high-frequency power transmission.

  Next, an example of the coaxial cable 1 for high-frequency power transmission according to an embodiment of the present invention and a comparative example of the coaxial cable will be described.

  As shown in FIG. 2, the sum of the cross-sectional areas of the plurality of copper wires 8 in the cross-section perpendicular to the axis is in the range of 1.3 to 1.5 times the cross-sectional area of the cross-section perpendicular to the axis of the internal conductor 2. The coaxial cable 1 for electric power transmission was manufactured (Examples 1-3).

  Also, a coaxial cable was manufactured in which the total cross-sectional area of the plurality of copper wires 8 in the cross-sectional area perpendicular to the axis was outside the range of 1.3 to 1.5 times the cross-sectional area of the cross-sectional area perpendicular to the axis of the internal conductor 2 ( Comparative Examples 1-6).

  In addition, the coaxial cable concerning Comparative Examples 1-6 is similar to the coaxial cable 1 for high frequency electric power transmission concerning one Embodiment of this invention mentioned above, as shown in FIG. The outer conductor 7 and the jacket layer 10 are arranged concentrically.

  With respect to each of Examples 1 to 3 and Comparative Examples 1 to 6 manufactured as described above, a characteristic test as shown in FIG. 2 was performed to determine the characteristics (handleability, cost reduction, transmission efficiency).

(Bending test)
As shown in FIG. 3, the coaxial cable 1 for high-frequency power transmission is inserted between two cylindrical bending jigs 22, and one end (upper end) of the coaxial cable 1 for high-frequency power transmission is attached to the jig 20. At the same time, the weight 21 is attached to the other end (lower end), the jig 20 is moved to one bending jig 22 side (symbol B side), and one end of the coaxial cable 1 for high-frequency power transmission is After bending along the outer peripheral surface of the bending jig 22, the jig 20 is moved to the other bending jig 22 side (symbol C side), and one end of the coaxial cable 1 for high-frequency power transmission is bent to the other side. Bend along the outer peripheral surface of the jig 22.

  Specifically, a series of operations for moving the jig 20 from the symbol A side to the symbol B side, from the symbol B side to the symbol A side, from the symbol A side to the symbol C side, and from the symbol C side to the symbol A side is one cycle. Then, the coaxial cable 1 for high-frequency power transmission is alternately bent in opposite directions.

  When the number of bendings reaches 10,000 times or more, the conductors, that is, the inner conductor 2 and the outer conductor 7 are not completely broken, and thus have sufficient mechanical strength. Moreover, it has sufficient flexibility because energy required for bending is smaller than a predetermined energy.

(Weight test)
The weight per unit length of the coaxial cable 1 for high-frequency power transmission is measured and is lighter than a predetermined weight, so that the weight is reduced.

  Note that, in the bending test and the weight test, what has been described as having a sufficient mechanical strength and sufficient flexibility and being reduced in weight is improved in handleability.

(Cost test)
By calculating the cost per unit length of the coaxial cable 1 for high-frequency power transmission and falling below a predetermined cost, the cost is reduced.

(Transmission efficiency test)
The AC current flowing through the inner conductor 2 and the AC current flowing through the outer conductor 7 are measured, and an AC current equivalent to the AC current flowing through the inner conductor 2 flows through the outer conductor 7, thereby providing sufficient transmission efficiency. Will be.

(Test results)
As shown in FIG. 2, the coaxial cable 1 for high-frequency power transmission according to Examples 1 to 3 of the present invention has good handleability and has been reduced in cost. Moreover, the coaxial cable 1 for high frequency power transmission had good transmission efficiency.

  On the other hand, the coaxial cables according to Comparative Examples 1 to 6 did not reach the performance required for either handling or transmission efficiency.

  Thus, in the range where the total cross-sectional area of the plurality of copper wires 8 in the cross-sectional area perpendicular to the axis is 1.3 to 1.5 times the cross-sectional area in the cross-sectional area perpendicular to the axis of the internal conductor 2, An alternating current equivalent to the current can be allowed to flow on the inner peripheral surface of the outer conductor 7, and the coaxial cable 1 for high-frequency power transmission with good transmission efficiency is obtained.

  On the other hand, if the total cross-sectional area of the plurality of copper strands 8 is less than 1.3 times the cross-sectional area of the internal conductor 2, the cross-sectional area of the internal conductor 2 and the external cross-section Since the ratio of the cross-sectional area of the cross section perpendicular to the axis of the conductor 7 changes and the resistance value of the external conductor 7 increases due to the skin effect, an alternating current equivalent to the internal conductor 2 does not flow to the external conductor 7 and transmission efficiency is improved. Declined.

  Further, if the total cross-sectional area of the plurality of copper wires 8 in the cross section perpendicular to the axis exceeds 1.5 times the cross-sectional area in the cross section perpendicular to the axis of the inner conductor 2, the thickness of the outer conductor 7 increases. The cable diameter has increased and the flexibility of the coaxial cable has decreased.

  Therefore, the handleability can be improved when the sum of the cross-sectional areas of the plurality of copper wires 8 in the cross section perpendicular to the axis is 1.3 to 1.5 times the cross-sectional area of the cross section perpendicular to the axis of the inner conductor 2. Thus, the coaxial cable 1 for high-frequency power transmission that can reduce the cost and improve the transmission efficiency can be manufactured.

  The coaxial cable 1 for high-frequency power transmission according to the present invention can be used as a cable for transmitting high-frequency power. For example, it is used for wiring in vehicles, wiring between devices, wiring for devices, and the like. can do.

DESCRIPTION OF SYMBOLS 1 Coaxial cable for high frequency power transmission 2 Inner conductor 3 Aluminum core wire 4 Copper coating 5 Insulator 7 Outer conductor 8 Copper element wire 10 Jacket layer R1 Inner conductor wire diameter R2 Copper wire diameter

Claims (1)

An inner conductor, an insulator provided on the outer periphery of the inner conductor, an outer conductor provided on the outer periphery of the insulator, and a jacket layer provided on the outer periphery of the outer conductor, and several tens of MHz Or a coaxial cable for high-frequency power transmission used for transmission of high-frequency power of several hundred MHz,
The inner conductor is a copper clad aluminum wire provided with a copper coating on the outer periphery of an aluminum core wire,
The outer conductor is a copper braided wire obtained by braiding a plurality of copper strands,
The ratio between the outer diameter of the inner conductor and the inner diameter of the outer conductor is set to a ratio that provides a predetermined characteristic impedance,
A coaxial cable for high-frequency power transmission, wherein the total cross-sectional area of the plurality of copper strands in the cross section perpendicular to the axis is 1.3 to 1.5 times the cross-sectional area in the cross section perpendicular to the axis of the internal conductor .

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