JP2007192770A - Vacuum feed through for thermocouple - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extract thermocouple lines from a vacuum space to the outside, even in a W-Re thermocouple or the like including a fine pore in its inside, under the condition where high airtightness is held, to measure a temperature under the condition where connection parts between the thermocouple lines and compensation conductors are held at the same temperature in the outside of the vacuum space, and to prevent thereby an error from being generated in electromotive force indicated by the thermocouple. <P>SOLUTION: Lead wire sides of the thermocouple lines 9a, 9b penetrated through an inorganic insulator 7 sealing a thermocouple port 3 are pulled out from the vacuum space to the outside, in this vacuum field through of the thermocouple, base parts of the thermocouple lines 9a, 9b including pulled-out portions of the thermocouple lines 9a, 9b are coated with a resin insulator 10 to be sealed airtightly, and the lead wire sides of the thermocouple lines 9a, 9b are connected to the compensation conductors 15a, 15b in the outside of the vacuum space. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thermocouple vacuum feedthrough in which a thermocouple wire having a temperature measuring contact installed in a vacuum space is drawn out from a sealed portion to the outside of the vacuum space, and in particular, W-Re made by wire processing by powder metallurgy. The present invention relates to a vacuum feedthrough of a thermocouple suitable for drawing out a thermocouple wire having fine pores from a sealing portion to the outside of a vacuum space, such as a system thermocouple.

  Because of its high melting point, W-Re thermocouples that are made by wire processing by powder metallurgy have fine through holes, so if they are pulled out of the vacuum space as they are through the thermocouple port, the sealing part is brazed. Is difficult. Even if such is the case, the airtightness is poor, and when a He leak test is performed, a He leak is often confirmed.

  Therefore, in the conventional vacuum feedthrough of the W-Re thermocouple, the thermocouple wire and the compensation lead wire are connected in a vacuum space, and the compensation lead wire is drawn out from the thermocouple port. A W-Re thermocouple is generally a thermocouple wire made of a 5% Re-W alloy and a 26% Re-W alloy, but the compensation wire connected to the former thermocouple wire is Alloy 426 is used for the compensating lead wire to which alloy 405 is connected to the latter thermocouple wire. Since these compensating lead wires can be processed by extrusion and drawing, the structure is dense, easy to seal by Ag brazing, high airtightness, and no leak is confirmed in the He leak test. Moreover, since these compensation conducting wires have high ductility, they have the advantage of excellent bending workability and high strength.

  FIG. 4 is a longitudinal sectional view showing an example of a vacuum feedthrough of a conventional general W-Re thermocouple. A flange 32 is provided in the thermocouple port 31 of the vacuum chamber, and a flange 33 of a feedthrough terminal is airtightly joined to the flange 32. The flanges 32 and 33 are joined by fastening with bolts and nuts 34 with a gasket 35 such as an O-ring interposed therebetween.

  One end of a metal sleeve 36 is air-tightly welded to the outer flange 33, and the other end of the metal sleeve 36 is sealed by fitting an inorganic insulator 37 such as alumina. The inorganic insulator 37 is penetrated by two thin metal sleeves 38. Compensation conductors 45a and 45b made of alloy 405 and alloy 426 are respectively passed through the metal sleeves 38 and 38, and the tips of the metal sleeves 38 and 38 passing through the compensation conductors 45a and 45b are brazed or welded. It is hermetically sealed. The tips of the compensating conductors 45a and 45b introduced to the vacuum chamber side through the metal sleeves 38 and 38 have a ring shape, and a thermoelectric consisting of 5% Re-W alloy and 26% Re-W alloy at the tip portion. The paired wires 39a and 39b are connected by screwing.

  As described above, the compensating lead wire 45a made of alloy 405 is connected to the thermocouple wire 39a of the 5% Re-W alloy on the positive electrode side of the W-Re thermocouple, and the 26% Re-W alloy on the negative electrode side. The thermocouple wire 39b is connected to a compensating lead wire 45b made of an alloy 426. Such a combination of a W-Re thermocouple and a compensating lead wire is defined by an American standard called ASTM. Alloy 405 and alloy 426 are Ni-based alloys, and a wire material having a fine structure can be obtained with extremely easy melting, stretching, and wire processing. Both welding and brazing are easy and airtightness is high.

  On the other hand, since a W-Re thermocouple has a high melting point, a melting apparatus using an electron beam in a vacuum is necessary for melting, but such an apparatus is extremely expensive, and the number of steps required for processing It takes time and is expensive. Therefore, wire processing of W-Re thermocouples is performed by powder metallurgy. In this case, W is easier to oxidize than Re and sublimates when oxidized, so it must be fired in a vacuum or in an inert gas atmosphere. The higher the firing temperature, the easier the sintering and densification. Of course, pores at the time of firing can be reduced by compacting with a hydrostatic pressure such as CIP and preliminarily forming a high-density rod-shaped molded body. In this respect, the pressure forming technique of the material before firing is also an important technique.

Thermocouple wires processed by powder metallurgy have low ductility and are easy to break. Therefore, the connection between the thermocouple wires and the compensating conductors is generally screwed. Since W-Re thermocouples are easily oxidized, they are suitable for measurement in a very high temperature region in a vacuum or in an inert gas.
As described above with reference to FIG. 1, the thermocouple wire and the compensation lead wire are connected on the vacuum space side, and a vacuum feed-through structure is adopted in which the compensation lead wire is drawn out through the ceramic terminal. A low thermal expansion coefficient alloy such as Kovar or Invar is used as the metal sleeve for passing the compensating conductor, and its end is hermetically sealed by brazing or welding to form a vacuum boundary. More specifically, hole into which the metal sleeve of the inorganic insulating material such as alumina is coated with a metal paste such as Mo-Mn, which in a vacuum, in a reducing atmosphere containing in or H ₂ inert gas atmosphere Pre-metallized by baking. The metal sleeve is fitted into the metallized hole and brazed. The metal sleeve is pulled out through a compensating conductor, and the end of the metal sleeve is hermetically sealed by brazing or welding to form a vacuum boundary.

  There is a temperature difference between the connecting portion between the thermocouple wire 39a of the 5% Re-W alloy and the compensating lead wire 45a of the alloy 405, and the connecting portion between the thermocouple wire 39b of the 26% Re-W alloy and the compensating lead wire 45b of the alloy 426. If it is small enough to be ignored, there is no problem. However, if the temperature difference between these connecting portions is large, an electromotive force proportional to 1.3 times that is generated between the connecting portions, resulting in a large error in the temperature indication value of the thermocouple. The temperature of the connecting portion between the 5% Re-W alloy thermocouple wire 39a on the positive pole side and the compensating lead wire 45a of the alloy 405 is 26% Re-W alloy thermocouple wire 39b on the negative pole side and the compensating lead wire of the alloy 426. If the temperature is higher than the temperature at the connection with 45b, the electromotive force indicated by the thermocouple shifts to the minus side, and vice versa.

  For example, the temperature of the connecting portion between the thermocouple wire 39a of the 5% Re-W alloy on the positive electrode side and the compensating lead wire 45a of the alloy 405 is between the thermocouple wire 39b of the 26% Re-W alloy on the negative electrode side and the alloy 426. When the temperature of the connecting portion with the compensating lead wire 45b is 100 ° C. higher, an electromotive force of −130 ° C. is generated in the thermocouple, and when the actual temperature at the temperature measuring junction of the thermocouple is 1500 ° C., the thermocouple The temperature indicated by the electromotive force is 1500−130 = 1370 ° C. On the other hand, if the temperature of the former positive electrode side connection portion is 100 ° C. lower than the temperature of the latter negative electrode side connection portion, the actual temperature at the thermocouple junction is 1500 ° C. The temperature indicated by the electromotive force of 1500 + 130 = 1630 ° C. In either case, an error of about ± 8.7% occurs.

  In order to avoid the temperature measurement error due to the temperature difference between the thermocouple wire and the compensation lead wire, the thermocouple wire should be airtight from the vacuum chamber rather than drawn out from the vacuum chamber. It is necessary to form a connection portion between the thermocouple wire and the compensation lead wire outside the vacuum chamber and keep the connection portion at the same temperature.

  However, as described above, since the W-Re thermocouple has a high melting point, the wire material is hardly processed from the melted material, and the wire material is generally processed by high-temperature firing by powder metallurgy. The disadvantage of the thermocouple wire processed by powder metallurgy is that a few pores remain inside, the airtightness is poor in the sealing by Ag brazing, and He leaks easily in the He leak test. .

In addition, W contained in the W-Re thermocouple is easily oxidized, and the oxide sublimates. Therefore, Ag brazing must be performed in a vacuum or in an inert gas atmosphere. In order to increase the air tightness of Ag brazing, it is necessary to penetrate the pores of the thermocouple wire into the Ag brazing brazing material and braze the Ag brazing to a length that does not cause He leakage. However, it is difficult to penetrate the brazing material of the Ag brazing into the pore portion of the thermocouple wire or to braze to a length of about 10 to 20 mm so that no He leak occurs. It is practically difficult to obtain perfect airtightness. Furthermore, the Ag brazed portion is easily broken, and the brazed portion forms a dissimilar metal connecting portion as an alloy containing an Ag brazing material. An error occurs in the power.
JP 7-273050 A Japanese Patent Laid-Open No. 2001-221692 JP 2001-343290 A

  In view of the problems in vacuum feedthrough of such conventional thermocouples, the present invention is high from the vacuum space to the outside even for thermocouple wires such as W-Re type thermocouples containing fine pores inside. It can be pulled out while maintaining airtightness, which enables temperature measurement with the connection between the thermocouple wire and compensation lead wire kept at the same temperature outside the vacuum space, and the electromotive force indicated by the thermocouple The purpose is to prevent errors from occurring.

  In order to achieve the above object, in the present invention, the thermocouple wires 9a and 9b are passed through the inorganic insulator 7 made of alumina or the like that seals the thermocouple port 1 of the vacuum space formed inside the vacuum chamber or the like. The base including the lead portions of the thermocouple wires 9a and 9b are covered with the resin insulator 10 so that the thermocouple wires 9a and 9b can be connected to the compensating conductor outside the vacuum space. is there. As a result, these connecting portions can be easily held at the same temperature. The resin insulator 10 can ensure airtightness by covering the bases of the thermocouple wires 9a and 9b over a length that does not cause He leakage in the He leakage test.

  That is, the vacuum feedthrough of the thermocouple according to the present invention penetrates the inorganic insulator 7 sealing the thermocouple port 3 and draws the lead wires of the thermocouple wires 9a and 9b from the vacuum space to the outside. Cover the bases of the thermocouple wires 9a and 9b including the lead-out portions of the pair wires 9a and 9b with the resin insulator 10 and hermetically seal them, and compensate the lead wires of the thermocouple wires 9a and 9b outside the vacuum space. It connects with conducting wire 15a, 15b.

  In such a thermocouple vacuum feedthrough, the resin insulator 10 covers the bases of the thermocouple wires 9a and 9b over a length that does not cause He leakage in the He leak test. Can be secured. In addition, since the thermocouple wires 9a and 9b are drawn out of the vacuum space and can be connected to the compensation lead wire outside the vacuum space, it is easy to make the temperature conditions of the connecting portions the same. . Therefore, it becomes easy to eliminate the measurement error of the thermocouple due to the temperature difference at the connection portion with the compensating lead wire.

  The resin insulator 10 can be easily provided by molding at the drawn portions of the thermocouple wires 9a and 9b of the inorganic insulator 7. Further, the resin insulator 10 may also serve as a housing for the connectors 12a and 12b that detachably connect the thermocouple wires 9a and 9b and the compensating lead wires 15a and 15b.

In the present invention, the base portions of the thermocouple wires 9a and 9b drawn out from the thermocouple ports of the vacuum chamber or the like are covered with the resin insulator 10, ensuring airtightness, and the thermocouple wires 9a and 9b outside the vacuum chamber or the like. And the compensating lead wires 15a and 15b can be connected.
Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

FIG. 1 is a partially longitudinal side view of a vacuum chamber showing a vacuum feedthrough of a thermocouple according to an embodiment of the present invention.
A flange 2 is provided in the thermocouple port 1 of the vacuum chamber, and a flange 3 of a feedthrough terminal is airtightly joined to the flange 2. The flanges 2 and 3 are joined by fastening bolts and nuts 4 with a gasket 5 such as an O-ring interposed therebetween.

One end of a metal sleeve 6 is air-tightly welded on the central axis of the outer flange 3, and the other end of the metal sleeve 6 is fitted with an inorganic insulator 7 such as alumina and hermetically sealed. Two thin metal sleeves 8, 8 pass through the inorganic insulator 7. The holes through which the metal sleeves 8 and 8 of the inorganic insulator 7 pass are coated with a metal paste such as Mo-Mn and baked in a vacuum, an inert gas atmosphere or a reducing atmosphere containing H ₂ in advance. Metalize. The metal sleeves 8 and 8 are fitted into the metallized holes and brazed. These metal sleeves 8 and 8 are respectively led through a 5% Re-W alloy thermocouple wire 9a on the positive electrode side and a 26% Re-W alloy thermocouple wire 9b on the negative electrode side.

  Further, a resin insulator 10 is provided on the lead bases of the thermocouple wires 9a and 9b, including the tips of the metal sleeves 8 and 8 through which the thermocouple wires 9a and 9b are passed, by means such as molding resin molding. The lead bases of the thermocouple wires 9a and 9b including the tips of the metal sleeves 8 and 8 through which the pair wires 9a and 9b are passed are covered. The length of the resin insulator 10 covering the base portions of the thermocouple wires 9a and 9b drawn from the tips of the metal sleeves 8 and 8 is set to a length b sufficient to prevent He leakage in the He leak test. Its length is usually 5 mm or more. Therefore, when the length of the tips of the metal sleeves 38, 38 protruding from the inorganic insulator 7 is a, the entire length of the resin insulator 10 covering the metal sleeves 8, 8 and the thermocouple wires 9a, 9b. L is L = a + b. This a + b is the total length of the seal and needs to be 30 mm or more. The reason why the inorganic insulating material 7 such as alumina is set to the vacuum side and the resin insulator 10 is set to the atmosphere side is that only the insulator surface on the vacuum side is heated by the radiant heat from the high temperature object in the vacuum chamber. This is because the insulating material must be an inorganic insulating material 7 such as alumina having high heat resistance.

  The W-Re thermocouple drawn out from the thermocouple port 1 to the outside of the vacuum chamber in this way has an alloy 405 in the 5% Re-W alloy thermocouple wire 9a on the positive electrode side on the air side that is easy to cool. The compensation lead wire 15a made of alloy 426 is connected to the thermocouple wire 9b of the 26% Re-W alloy on the negative pole side by a group of screws or the like. Connections between the thermocouple wires 9a and 9b and the compensating lead wires 15a and 15b are placed under the same temperature condition.

FIG. 2 is a partially longitudinal side view of a vacuum chamber showing a vacuum feedthrough of a thermocouple according to another embodiment of the present invention.
In the thermocouple vacuum feedthrough according to this embodiment, the resin insulator 10 constitutes male and female connectors 12a and 12b, and the male connector 12a and female connector 12b compensate for the thermocouple wires 9a and 9b. Conductive wires 15a and 15b are connected.

  First, an adapter 11 made of a cylindrical metal is fitted into the metal sleeve 6 welded to the outer flange 3, and a male connector 12 a is screwed to the tip of the adapter 11. A pair of connector pins 14a and 14b are projected from the distal end of the male connector 12a, and a thermocouple wire on the positive electrode side is disposed at the base end of the pair of connector pins 14a and 14b inside the resin housing of the male connector 12a. 9a and the thermocouple wire 9b on the negative electrode side are screwed. In the male connector 12a, the resin housing hermetically seals the tip portion from which the thermocouple wires 9a and 9b of the adapter 11 are drawn. The lengths of the thermocouple wires 9a and 9b inside the resin housing of the male connector 12a are short. Therefore, the resin housing of the male connector 12a covers the lead-out portions of the thermocouple wires 9a and 9b, so that the thermocouple wires 9a and 9b are covered. However, even if it has fine pores like a W-Re thermocouple, no He leak occurs. That is, the resin housing of the male connector 12a functions as an insulating resin that hermetically seals the lead portions of the thermocouple wires 9a and 9b.

  On the female connector 12b side, a pair of pin receiving metal fittings 16a and 16b are housed in the resin housing, and the compensating lead wire on the positive pole side is provided on the base end side of the pin receiving metal fittings 16a and 16b inside the resin housing. 15a and a negative lead side compensating lead wire 15b are screwed to each other. FIG. 2 shows a state in which the connector pins 14a and 14b of the male / female connector 12a are fitted to the pin receiving brackets 16a and 16b of the female connector 12b, whereby the thermocouple wires 9a and 9b are respectively connected to the compensating conductor 15a, 15b.

  FIG. 3 is an exploded perspective view showing an example of the adapter 11. The adapter 11 includes a pair of half members 16, 16 that are half of a cylindrical member. The half members 16, 16 are assembled into a cylindrical shape, and the bases of the half members 16, 16 are fitted into the metal sleeve 6. Include. Further, the tightening portions 17 and 17 projecting laterally from the base portions of the half members 16 and 16 are screwed and fixed to the metal sleeve 6. Further, the male connector 12a is molded as a resin insulator at the tip of the adapter 11, and the metal sleeves 8 and 8 and the thermal wires 9a and 9b are covered and screwed to prevent them from coming off. For example, the male connector 12a is manufactured by connecting the connector pins 14 and 14 to the thermocouple wires 9a and 9a at the tip of the adapter 11, and then molding the resin connector housing of the male connector 12a so as to cover them. Screw holes 18 and 18 for screwing the male connector 12a are provided at the tip of the adapter 11 there.

It is a partial longitudinal section side view of a vacuum chamber showing vacuum feedthrough of a thermocouple which is one embodiment of the present invention. It is a partial vertical side view of the vacuum chamber which shows the vacuum feedthrough of the thermocouple which is the other Example of this invention. It is a disassembled perspective view which shows the example of the adapter used for the Example shown in the said FIG. It is a partial longitudinal cross-sectional view of the vacuum chamber which shows the example of the vacuum feedthrough of the conventional general W-Re type thermocouple.

Explanation of symbols

3 thermocouple port 7 inorganic insulator 9a thermocouple wire 9b thermocouple wire 10 resin insulator 12a connector 12b connector 15a compensating lead wire 15b compensating lead wire

Claims (3)

A thermocouple vacuum feedthrough that draws the thermocouple wires (9a) and (9b) with temperature measuring contacts installed in the vacuum space to the outside of the vacuum space, and seals the thermocouple port (3). The lead wire side of the thermocouple wires (9a) and (9b) is drawn out from the vacuum space through the stopped inorganic insulator (7), and the lead portions of the thermocouple wires (9a) and (9b) are In addition, the base of the thermocouple wires (9a) and (9b) is covered with a resin insulator (10) and hermetically sealed, and the lead wires of the thermocouple wires (9a) and (9b) are outside the vacuum space. Thermocouple vacuum feedthrough, characterized in that it is connected to compensating conductors (15a), (15b). The thermocouple vacuum feedthrough according to claim 1, characterized in that the resin insulator (10) is molded in the lead portion of the thermocouple wire (9a), (9b) of the inorganic insulator (7). The resin insulator (10) also serves as a housing for the connectors (12a) and (12b) for detachably connecting the thermocouple wires (9a) and (9b) and the compensating lead wires (15a) and (15b). The thermocouple vacuum feedthrough according to claim 1.

Images