JP2008192385A - Coaxial cable, and manufacturing method of inner conductor for coaxial cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coaxial cable having an inner conductor in which a tin plated layer is formed on the surface of a copper wire rod, and in which attenuation of a high frequency signal due to a skin effect is suppressed. <P>SOLUTION: This is the coaxial cable in which the inner conductor is covered by an insulator, an outer conductor, and a sheath in order, and the inner conductor has a tin plated layer of an average thickness of 0.5-0.6 μm on the surface of a copper wire rod 22. The tin plated layer is formed by a hot-dip plating method and the wire rod is immersed in molten tin 61 and then, is passed through a dice hole 63 of dice 62. Then, application quantity control and smoothing of the surface by the dice 62 are carried out and a tin plated layer with a smooth surface is formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is used, for example, for connecting a television receiver or radio to an antenna, or for connecting a measuring device, and in particular for signal transmission of audio signals and video signals in terrestrial, satellite broadcasting (BS / CS), CATV. More particularly, the present invention relates to a coaxial cable having good attenuation characteristics.

  A coaxial cable has a structure in which a circular inner conductor is covered with an insulator, an outer conductor is arranged around the insulator, and the outer conductor is covered with a sheath. The inner conductor transmits a signal (radio wave), and the outer conductor does not leak the signal transmitted through the inner conductor to the outside, and prevents intrusion of radio waves from the outside.

  As described above, the signal is devised so that it can be transmitted safely in consideration of the interference wave and leakage, but the coaxial cable has a problem of attenuation of the high frequency signal. That is, there is a problem that due to the skin effect, the amount of attenuation increases as the transmitted signal becomes higher in frequency. The skin effect is that when a high-frequency current flows through a conductor, the current concentrates on the surface of the conductor and the density increases and resistance increases. In recent years, since the transmission frequency has been increased in satellite broadcasting or the like, a coaxial cable with good attenuation characteristics is required.

  By the way, the inner conductor is manufactured by applying tin plating to a copper wire for the purpose of preventing oxidation. However, the high frequency signal is attenuated on the surface of the inner conductor due to the property of the surface portion of the inner conductor. It is thought that there is.

  That is, in a general coaxial cable, tin plating of an inner conductor is performed by a hot dipping method, and drawing (a basis weight control) after being immersed in molten tin is performed using a linear body made of asbestos. This is to improve the adhesion with the insulator covering the inner conductor.

  Since the inner conductor is manufactured in this way, as shown in FIG. 6, there are many micro irregularities 102 on the surface of the inner conductor 101 and there is no smoothness. For this reason, it is considered that the resistance is further increased and the amount of attenuation is increased at the time of transmission of the high-frequency signal flowing concentrated on the surface due to the skin effect.

  In addition, there exists invention which was disclosed by the following patent document 1 as what is going to eliminate the attenuation | damping problem by a skin effect. This is because the magnetic permeability and conductivity have a special conductive coating, and it is not intended to obtain good damping characteristics from the above viewpoint. In addition, there is no attempt to solve the high-frequency signal attenuation problem depending on the surface properties of the inner conductor.

JP 2006-49328 A

  The main object of the present invention is to obtain good attenuation characteristics depending on the surface state of the inner conductor.

  The means for this is a coaxial cable in which the inner conductor is covered with an insulator, an outer conductor and a sheath in order, and the inner conductor is a tin-plated layer having an average thickness of 0.5 to 0.6 μm on the surface of the copper wire. A coaxial cable in which the surface of the tin plating layer is smoothly formed by a die.

  Another means is a method of manufacturing an inner conductor for a coaxial cable, which is sequentially covered with an insulator, an outer conductor, and a sheath. After the copper wire is immersed in molten tin, the die is passed through a die hole. Is a method for producing an inner conductor for a coaxial cable in which a tin-plated layer having an average thickness of 0.5 to 0.6 μm and a smooth surface is formed by controlling the basis weight and smoothing the surface.

  That is, according to said structure, the tin plating formed in the surface of a wire is 0.5-0.6 micrometer, and is thinner than the general thing exceeding 1 micrometer. As a result, it is possible to increase the number of high-frequency signals transmitted through the copper wire having high conductivity. Moreover, the surface is smooth. “Smooth” means, for example, a state in which the thickness variation is within 0.1 μm and is less than a general one exceeding 1 μm.

  For this reason, an increase in resistance at the surface portion of the inner conductor can be prevented, and attenuation of the high-frequency signal can be suppressed.

  As described above, according to the present invention, attenuation of a high-frequency signal due to the skin effect can be suppressed.

An embodiment for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is a perspective view showing the structure of the coaxial cable 11. The coaxial cable 11 has an inner conductor 21 located at the center in the cross section, an insulator 31, an outer conductor 41, and a sheath 51 surrounding the inner conductor 21 in order. Have

  The inner conductor 21 is a portion through which a signal (radio wave) is transmitted. As shown in FIG. 2, the average thickness t is 0.5 to 0.6 μm on the surface of the wire 22 having a perfectly circular cross section made of soft copper. In this structure, a tin plating layer 23 is formed. The formation of the tin plating layer 23 is to prevent oxidation.

  The insulator 41 has an electrical insulation function and an internal conductor protection function, and is formed of, for example, foamed polyethylene.

  The outer conductor does not leak a signal (radio wave) transmitted through the inner conductor to the outside, and prevents intrusion of radio waves from the outside, and is composed of an aluminum foil tape 42 and a braided wire 43. As the aluminum foil tape 42, for example, a double-sided aluminum foil-attached PET tape can be used. As the braided wire 43, an aluminum alloy wire twisted in a net shape can be used.

  The sheath 51 is an outer skin that wraps and protects the coaxial cable 11 and is formed of, for example, weather-resistant vinyl chloride.

  The tin plating layer 23 of the inner conductor 21 is formed by a hot dipping method, and is formed smoothly with little variation in thickness as shown in FIG. Since the surface is smooth, it has a glossy appearance.

Such a tin plating layer 23 is formed as shown in FIG.
That is, after the long wire 22 is sequentially immersed in the molten tin 61 heated to a predetermined temperature, the wire 22 coming out of the molten tin 61 and having the molten tin 61 adhered thereto is squeezed. This throttling is performed through the die 62. A predetermined large die hole 63 is formed in the die 62 according to the diameter of the wire 22. Further, the mouth edge of the die hole 63 is formed smoothly so as not to be uneven. Thereby, a tin plating layer 23 having a predetermined thickness can be formed. In addition, since the rim of the die hole 63 is formed in a smooth shape without irregularities, the unevenness of the irregularities on the surface of the tin plating layer 23 can be suppressed. Specifically, it can be suppressed to within 0.1 μm, and can have smoothness and denseness.

  When the coaxial cable 11 having the inner conductor 21 formed as described above was tested for attenuation characteristics, the result shown in FIG. 5 was obtained.

  The coaxial cable 11 as a sample used for the test has an outer diameter of the inner conductor 21 of 1.05 mm, an outer diameter of the insulator 31 of 5.0 mm, and a thickness of the insulator 31 of 1.98 mm. A braided wire 43 made of PET tape (aluminum foil tape 42) with a double-sided aluminum foil having a thickness of 0.05 mm and an aluminum alloy wire is used for 41, and a weather-resistant vinyl chloride having a thickness of 0.95 mm is used for the sheath 51. Is.

  As a comparative example, the tin plating layer of the inner conductor was formed by controlling the basis weight with a linear body made of asbestos as in the past, and tests were also performed with coaxial cables having the same conditions as those described above for the other parts.

  In the test, the attenuation per 100 m was examined. In FIG. 5, the result of the sample is indicated by a solid line, and the result of the comparative example is indicated by a one-dot chain line.

  As shown in this figure, the attenuation amount increases as the frequency increases as a whole, but in the case of the sample, the attenuation amount is not large compared to the case of the comparative example.

  That is, in the case of a sample, 9.6 dB at 220 MHz, 14.5 dB at 470 MHz, 19 dB at 770 MHz, 23 dB at 1000 MHz, 27 dB at 1300 MHz, 30.2 dB at 1550 MHz, 32.8 dB at 1770 MHz, 34 dB at 1800 MHz, 37 dB at 2000 MHz. In contrast, in the case of the comparative example, the frequencies were 11.5 dB, 20.5 dB, 27.5 dB, 34 dB, 41.8 dB, 48 dB, 52 dB, and 56 dB, respectively, in the comparative example.

  As described above, as compared with the comparative example, it is possible to suppress the attenuation as a whole, and it is possible to suppress the amount of attenuation particularly in a high frequency region.

  In addition, it is conceivable that the plating layer on the surface of the inner conductor is formed by silver plating in order to improve the attenuation characteristics, but silver plating is effective and cannot be used for a coaxial cable for which the manufacturing cost is to be suppressed. In this regard, if tin plating is used as described above, it can be manufactured at a low cost, and good damping characteristics can be obtained as described above.

  In addition, when a silver plating layer is formed, it must be based on an electroplating method. However, if a tin plating layer is formed, it can be manufactured by a hot dipping method, so that there is an advantage that existing facilities can be used effectively. .

  The above is one form for implementing this invention, and is not limited to the above-mentioned structure, Other forms can be employ | adopted.

The perspective view which shows the structure of a coaxial cable. The enlarged view which shows the cross-section of an internal conductor. The partially broken side view of an internal conductor. Explanatory drawing which shows the manufacturing method of an internal conductor. The graph which shows a damping characteristic. The partially broken side view of the conventional internal conductor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Coaxial cable 21 ... Inner conductor 22 ... Wire material 23 ... Tin plating layer 31 ... Insulator 41 ... Outer conductor 51 ... Sheath 61 ... Molten tin 62 ... Die 63 ... Die hole

Claims (2)

A coaxial cable in which an inner conductor is covered with an insulator, an outer conductor, and a sheath in order,
A coaxial cable in which the inner conductor has a tin plating layer having an average thickness of 0.5 to 0.6 μm on the surface of a copper wire, and the surface of the tin plating layer is smoothly formed by a die. A method for producing an inner conductor for a coaxial cable, which is sequentially covered with an insulator, an outer conductor and a sheath,
After immersing the copper wire in molten tin, pass through the die hole of the die, perform basis weight control with the die and smooth the surface, the average thickness is 0.5-0.6μm and the surface is smooth A method for producing an inner conductor for a coaxial cable for forming a tin plating layer.

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