JPH06139836A - Coaxial cable for high temperature - Google Patents

Abstract

PURPOSE:To provide a coaxial cable capable of efficiently transmitting high frequencies in the temperature range of 1,000 deg.C or above so that it can be used for the measurement in the high-frequency range at a high temperature. CONSTITUTION:A platinum wire is used for the center conductor 1 of a coaxial cable, and a platinum pipe is used for the outer conductor 3. A heat-resistant ceramic tube made of alumina or zirconia or a heat-resistant glass tube made of Pyrex glass or quartz glass is used for an insulator 2 arranged between the center conductor 1 and the outer conductor 3. Heat-resistant ceramic powder is used for the insulator 2, and it is densely filled between the center conductor 1 and the outer conductor 3. Platinum has high heat resistance temperature and chemical stability and low electric resistance, and it can be used at a high temperature with no problem. Heat-resistant ceramic and glass can be used with no problem. No problem occurs on the transmission characteristic at a high temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high temperature coaxial cable for efficiently transmitting high frequency waves in a high temperature region.

[0002]

2. Description of the Related Art Commercially available coaxial cables that can be used at high temperatures are limited to approximately 150 ° C for semi-rigid cables that use Teflon as an insulator, and 500 ° C for those that use silicone resin as an insulator. Is. Thus, it can be said that the operating temperature of the conventional coaxial cable is regulated by the heat resistant temperature of the insulator.

[0003]

However, the conventional commercially available coaxial cable as described above cannot be used when a high frequency region is measured at a high temperature, for example, 1000 ° C. or higher. In order to make a coaxial cable that can be used at high temperatures, it is important to use an insulating material that can withstand high temperatures. Furthermore, depending on the operating temperature, it is necessary to use a material that is stable at high temperatures for the conductor.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a high-temperature coaxial cable that can be used at high temperatures by selecting an insulating material and a conductor that can withstand high temperatures. Especially.

[0005]

In order to achieve the above object, the present invention has the following constitution. That is, the center conductor of the coaxial cable is a platinum wire, the outer conductor is a platinum pipe, and heat-resistant ceramics such as alumina and zirconia or heat-resistant glass such as Pyrex glass and quartz glass are used as an insulator between them, and a rigid coaxial cable is used. Constitute. In addition, a heat-resistant ceramic powder is filled between the center conductor of the platinum wire and the outer conductor of the platinum pipe to form a semi-rigid coaxial cable.

[0006]

In the above structure, the platinum used for the central conductor and the outer conductor has a high heat resistance temperature, high chemical stability such as not being oxidized in high temperature atmosphere, low electric resistance, and high temperature coaxial It has all the characteristics of a conductor required for a cable. Heat-resistant ceramics can be used without problems up to about 2000 ° C, and there is no problem even at high temperatures of 1000 ° C or higher. The heat-resistant glass includes Pyrex glass, quartz glass, etc., and can be used up to 1150 ° C without any problem. The above heat-resistant ceramics and heat-resistant glasses cannot be bent freely, and only linear connections are allowed. However, by replacing the insulators with heat-resistant ceramic particles, the bending strength of the outer conductor platinum pipe is allowed. We can provide a semi-rigid coaxial cable that can be bent at. In either case, the increase in resistance at high temperature increases the amount of attenuation, but there is no problem with the transmission characteristics at high temperature. In the case of heat-resistant glass, the outer diameter of the central conductor can be made larger and the amount of attenuation can be reduced because the relative permittivity is smaller than that of heat-resistant ceramic.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to illustrated embodiments. FIG. 1 is a perspective view showing a high temperature coaxial cable of the present invention, which is composed of a central conductor 1, an insulator 2, and an outer conductor 3 in this order from the inside. The external insulator is omitted because it is not important in consideration of the usage environment of the high-temperature coaxial cable. The outer conductor 3, the insulator 2, and the center conductor 1 are fixed to each other by a high temperature ceramic adhesive at the end of the cable.

[Example 1] This is an example of a platinum coaxial cable using a heat-resistant ceramic insulating tube as an insulator. The heat-resistant ceramic insulating tubes that are usually available include those shown in Table 1.

In this example, alumina (99.5%)
A high temperature coaxial cable with the same outer diameter as the UT-85 semi-rigid cable manufactured by US Uniform Tube Co., Ltd. The outer conductor 3 has an outer diameter of 2.
A platinum pipe having a thickness of 2 mm and a thickness of 0.1 mm, an insulator 2 having an outer diameter of 1.6 mm and an inner diameter of 1.0 mm is used as the insulator 2, and a central conductor 1 is a platinum wire having a diameter of 0.4 mm and is coaxial. Configured the cable.

Characteristic impedance at room temperature is 52Ω
Thus, it was confirmed that impedance matching can be achieved by using it for 50Ω system wiring. The coaxial cable was passed through a tubular electric furnace having a core tube length of 600 mm, and the transmission characteristics of the coaxial cable at high temperature were measured.
At ° C, 800 ° C, 1000 ° C, and 1300 ° C, impedance matching was taken as at room temperature, and only an increase in attenuation due to an increase in core wire resistance was observed.

[0011]

[Table 1]

[Embodiment 2] This is an example of a high-temperature coaxial cable in which a quartz glass thin tube is used as an insulator 2 instead of the heat-resistant ceramic insulation tube in Embodiment 1. The relative permittivity of quartz glass is 3.5 to 4.7, which is about half that of heat-resistant ceramics. Therefore, when a cable having the same outer diameter and the same characteristic impedance is designed, the outer diameter of the center conductor 1 becomes large. As a result, it is possible to provide a high-temperature coaxial cable in which the amount of attenuation due to the increase in resistance of the center conductor 1 is small at high temperatures.

[Embodiment 3] This is a high temperature prepared by densely filling fine powder of the same heat resistant ceramic between the outer conductor 3 and the center conductor 1 instead of the heat resistant ceramic insulating tube in the first embodiment. It is an example of the coaxial cable for.
The electrical characteristics and high temperature characteristics are the same as those of the high temperature coaxial cable of the first embodiment. Since the insulator 2 is a powder, this cable can be bent to a minimum R25 mm. Even when it was bent, there was no change in its electrical property and high temperature property.

[0014]

As described above, according to the present invention, the central conductor of the coaxial cable is the platinum wire, the outer conductor is the platinum pipe, and the heat insulating ceramic, quartz glass, and heat resistant ceramic fine powder are used as the insulator between them. Therefore, the coaxial cable can be used at a high temperature without any problem, and the electrical measurement in the high frequency region at a high temperature, which has been difficult in the past, can be performed.

[Brief description of drawings]

FIG. 1 is a perspective view showing a high temperature coaxial cable of the present invention.

[Explanation of symbols]

 1 center conductor 2 insulator 3 outer conductor

Claims (3)

[Claims] 1. A high-temperature coaxial cable, characterized in that a rigid coaxial cable is constructed by interposing a heat-resistant ceramic insulator between a center conductor of a platinum wire and an outer conductor of a platinum pipe. 2. A high-temperature coaxial cable, characterized in that a rigid coaxial cable is formed by interposing a quartz glass insulator between a central conductor of a platinum wire and an outer conductor of a platinum pipe. 3. A high-temperature coaxial cable, characterized in that a semi-rigid coaxial cable is constituted by filling a heat-resistant ceramic powder between a center conductor of a platinum wire and an outer conductor of a platinum pipe.