JPH0760714B2 - Current introduction terminal - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current introduction terminal for supplying an electric current from the outside to the inside of a vacuum device, a pressure vessel or the like, or for extracting a minute electric signal for measurement from the inside to the outside. is there.

2. Description of the Related Art A conventional current terminal is shown in FIG. A metal flange 5 which holds copper or brass metal rods 1, 1'on a metal flange 3 via a ceramic insulator 2 and is welded to a vacuum container 4.
Insert a copper ring 6 for sealing between the metal flange 3 and the metal flange 4
The protrusions 8 and 8'of the respective metal flanges are made to fit into the copper ring 6 with ~ 8 tightening bolts 7 and 7'and vacuum-sealed. For the ceramic insulator 2, a material whose coefficient of thermal expansion is close to that of the metal flange 3 and the metal rods 1,1 'is selected, and when the ceramic insulator 2 is fired due to the good adhesiveness of the ceramic material, the interface between the metal flange 3 and the metal rods 1,1' is used. Vacuum sealed to prevent leaks.

Problems to be Solved by the Invention In the prior art, since the ceramic material is used as the sealing insulator, the insulating property is poor, and the leakage current between the metal rods 1, 1'and the grounded metal flange is large and is 10V. Since it is about 1 nA, it cannot be used for measuring very small currents. The current-introducing terminal with a high-voltage insulator improves the insulation by one to two digits, but it is still unusable for measuring minute currents of about 1 pA, and since it is one terminal, it requires multiple current-introducing terminals. In addition, the length of the metal rod is 4 cm to 8 cm, so it is easily affected by electromagnetic noise. It is desirable to have a total of four or more terminals, two terminals for introducing a thermocouple and two terminals for measuring a signal, as current introduction terminals for normal measurement.

Means for Solving the Problems The present invention uses a fluorine resin having a large volume resistivity and a large surface resistance in order to reduce a leak current, and a metal rod and a vacuum for solving the problem that the fluorine resin cannot be adhesively sealed. It is obtained by directly mechanically pressure-bonding the vacuum sealing portion with the flange of the container to the fluorine-based resin of the integrated insulator for vacuum sealing.

Action PTFE (tetrafluoroethylene resin), which is a representative of fluorocarbon resin
Has a volume resistivity of about 10 ¹⁹ Ωm and a surface resistance of about 10 ¹⁷ Ω, which is more insulating than the excellent volume resistivity of alumina porcelain 10 ¹² Ωm and a surface resistance of 10 ⁹ Ω. The leakage current can be reduced. Fluorine-based resin has a good thermal dimensional stability and low hardness compared to other resins, and it has a male body, so it can be used as a vacuum sealing material instead of a copper ring, so it has an integrated insulation function and sealing function. A structure as shown in the embodiment of FIG. 1 is possible.

Example A typical example according to the present invention is shown in FIG. A plurality of stainless steel metal rods 9 and 9'having a diameter of 2.6φ and a length of about 15 mm with screw parts at both ends are fixed to the through hole in the center of the disk-shaped insulator 10 made of fluorocarbon resin. Tighten with nuts 11 and 11 'to fit the brim portions 12 and 12' of the metal rod into the disk-shaped insulator 10 and mechanically vacuum seal. Further, a flange 14 made of stainless steel or the like welded to the vacuum container 13 and a flange 15 made of stainless steel or the like for the current introduction terminal sandwich the flange portion 16 on the outer periphery of the disk-shaped insulator 10, and the respective protrusions 18 along the circumference. , 19
4 ~ 8 bolts 17,17 '
And vacuum seal mechanically. The metal of the mechanical seal part is hard such as chrome plating or stainless steel and has a stable surface that is difficult to oxidize.

In the embodiment shown in FIG. 1, a metal cylindrical shield tube 20 or 2 which plays the role of a double shield for eliminating the charging current to the insulator.
The groove 0'is fitted into the disk-shaped insulator 10 by providing a groove.
Connect the inner shield wire of the double shielded wire of the micro current measurement system to the cylindrical shield tube 20, 20 ', and connect the measurement signal wire to 9,
When it is connected to 9 ', the cylindrical shield tube 20 is always given the same potential as the metal rod 9 even if the measurement signal voltage changes, so that the electric field is not applied to the insulating part 21 and the leak current to the shield tube 20 does not occur. Does not occur. The shielded wire outside the double shielded wire is connected to a flange 15 electrically connected to the vacuum vessel 13 to bring it to the ground potential. Fluororesin is PTFE as well as FEP (random copolymer of tetrafluoroethylene and hexafluoropropylene)
Polyvinyl fluoride, polyvinylidene fluoride, etc. are used.

When taking out the thermocouple, the wire of the thermocouple was inserted through the through hole of 1φ into the center of the stainless steel metal rod 9, 9'having a diameter of 2.6φ and sealed with epoxy resin. It is not possible to directly seal the thermocouple wire and the disc-shaped insulating plate 10 because the adhesiveness of the fluororesin is poor.

Effect of the Invention In the embodiment of FIG. 1 according to the present invention, the leak current was 0.05 pA or less even without the cylindrical shield tube. Then, the reverse current of the diode in the vacuum was measured. As a result, it was possible to measure an accurate current of 1 pA or less with an applied voltage of 10 V, and there was no change due to the humidity of the outside air. Among fluoropolymers
PTFE and FEP have small relative permittivity of about 2.1 and are good for high frequency measurement.

As described above, according to the present invention, it is possible to measure a minute current, which is impossible in the conventional example, with respect to a sample in a vacuum container or a pressure container. Therefore, it is possible to supply an excellent current introducing terminal which is not damaged by mechanical shock and is not affected by the humidity of the outside air.

[Brief description of drawings]

FIG. 1 is a structural sectional view of a current introducing terminal of an embodiment according to the present invention, and FIG. 2 is a structural sectional view of a conventional current introducing terminal. 1,1 '... metal rod, 2 ... ceramic insulator, 3,5 ... metal flange, 4 ... vacuum container, 6 ... copper ring, 7,7'
…… Bolts, 8,8 ′ …… Protrusions.

Claims (1)

[Claims] 1. A metal rod penetrating a central portion of an insulator made of a fluorine-based resin is held, and the flange of the metal rod is tightened so as to bite into the insulator to directly attach the metal rod to the insulator. A current characterized in that the outer periphery of the insulator is mechanically vacuum-sealed directly by mechanically vacuum-sealing and tightening the metal pressure vessel or the protrusion on the vacuum vessel side so as to bite into the insulator. Introducing terminal.