JP3627317B2 - Thermocouple structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure of a thermocouple with high temperature and high accuracy.
[0002]
[Prior art]
Conventional thermocouples have been developed to accurately measure the temperature of high-temperature liquids and gases. The thermocouple adapts various measuring materials in order to measure the temperature in the temperature range of 300 ° C to 1400 ° C. Thermocouple wires are often weak against oxidizing or reducing atmospheres, and are generally used by putting them in a protective pipe.
[0003]
In addition, as a protective tube for housing a conventional thermocouple, the following materials are used. That is, the conventional protective tube is BN (heat resistant temperature: 1000 ° C.), porcelain (heat resistant temperature: 1400 ° C.), alumina (heat resistant temperature: 1600 ° C.), high chromium steel (heat resistant temperature: 1050 ° C.), alundum (heat resistant temperature) Various protection tubes such as a temperature of 1400 ° C. are used. A thermocouple made of such a protective tube is damaged by a single measurement and cannot be used again if it is used up to a heat-resistant temperature. It is currently used in a temperature atmosphere of about ° C.
[0004]
Further, thermocouples in which Si ₃ N ₄ is formed as a protective pipe include those disclosed in, for example, Japanese Patent Laid-Open Nos. 55-121972, 61-246636, and 2-217361. .
[0005]
JP 55-121972 Patent airtight silicon nitride sintered body disclosed in the publication can be applied to the protective tube of the thermocouple, Si ₃ N ₄ sintered with bulk density of the generated limited amount of reaction sintering method The bonded body is humidified to a specific dew point in a humidified N ₂ atmosphere and heat-treated at 1250 to 1500 ° C. to make the surface airtight.
[0006]
Further, the molten steel continuous temperature measuring protective tube disclosed in Japanese Patent Application Laid-Open No. 61-246636 can be used as a protective tube for a thermocouple, and between the protective tube made of reaction sintered silicon nitride and the alumina inner tube, AlN A protective tube filled with powder and further filled with alumina wool on top of the AlN powder is made, and the erosion rate by the molten steel is reduced, and the molten steel temperature can be measured for a long time.
[0007]
Furthermore, the reaction sintered silicon nitride ceramics disclosed in JP-A-2-217361 can be used as a protective tube for a thermocouple, and a molded body obtained by molding Si powder can be used at about 1200 to 1600 ° C. in an N ₂ atmosphere. Reaction sintered.
[0008]
[Problems to be solved by the invention]
However, the protection tube for protecting a conventional thermocouple actually causes considerable damage to the protection tube at a temperature of 1000 ° C. or higher. For this reason, conventional thermocouples currently have difficulties in measuring the temperature of high-temperature furnaces and molten metal. For example, when the thermocouple is formed in a thin pipe shape, there are manufacturing problems in order to appropriately adjust the strength of the protective tube protecting the thermocouple and the density of the filler in the protective tube. Also, the thermocouple to prepare a protective tube with BN, to oxidize in the presence of O _2, that are used after exhausting the O ₂ in the furnace at present.
[0009]
In addition, for a structure in which a thermocouple is arranged in a protective tube, even when the protective tube is made of reaction-sintered silicon nitride, a pair of different types of wires extending in the longitudinal direction from one end to the other end are provided in the protective tube. However, if an appropriate material is not selected as the filling member to be filled in the protective tube, a gap will be generated between the inner surface of the protective tube and the filling member, and the wire will oxidize with O ₂ present in the protective tube and break. There is a problem of being damaged by heat shock.
[0010]
[Means for Solving the Problems]
An object of the present invention is to solve the above-mentioned problem, and a protective pipe is formed of a heat-resistant ceramic such as Si ₃ N ₄ or SiC, and tungsten (W) -rhenium (Re) alloy or platinum ( A thermocouple wire is made from Pt) -Rhodium (Rh), TiN, etc. is synthesized outside the thermocouple wire, and the thermocouple wire is enclosed in a protective pipe, resulting in excellent heat resistance and heat shock resistance. , To provide a thermocouple structure with high durability.
[0011]
The present invention, protective pipe made of heat-resistant ceramics, the above-spaced in a protective pipe extending longitudinally from one end to the other in different pair of conductive wire rod, is formed at one end of the protective pipe a thermoelectric characterized in that it consists filling member conductor temperature sensitive portion of connecting the two ends of the conductive wire rod,及 beauty mixed powder consisting of filled Si and Ti in the protective pipe is integrally sintered in a N ₂ atmosphere Concerning the structure of the pair.
[0012]
The protective pipe is made of Si ₃ N ₄ or SiC , the filling member in the protective pipe is made of Si ₃ N ₄ and TiN, and the conductor wire is made of W-5% Re and W-26% Re. It consists of .
[0013]
In addition, in this thermocouple structure, a number of holes are formed in the protective pipe so as to be spaced apart in the longitudinal direction, and the surface of the filling member exposed from the holes after sintering is coated with Si ₃ N _4. It is what .
[00 14 ]
In addition, in order to fix the mounting bracket to the end of the protective pipe, Ag-Cu-Ti powder is applied to the filling member exposed in the hole formed in the protective pipe, and the mounting bracket and the filling member are applied. Are fixed. That is, the mixed material of Si ₃ N ₄ and TiN diffuses well into Ag—Cu—Ti, and a good bonding state can be obtained.
[0015]
The conductor wire is bent in a spiral shape to absorb the difference in thermal expansion . [00 16 ]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a thermocouple structure according to the present invention will be described below with reference to the drawings. 1 is a cross-sectional view showing an embodiment of the thermocouple structure according to the present invention, FIG. 2 is an enlarged cross-sectional view showing an end of the thermocouple structure of FIG. 1, and FIG. 3 is taken along line AA in FIG. It is sectional drawing.
[00 17 ]
The structure of this thermocouple is mainly composed of a protective pipe 1 made of heat-resistant and corrosion-resistant ceramics 1 and a pair of conductor wires 2 of different types extending in the longitudinal direction from one end to the other end in a protective pipe 1. 3, a conductor temperature sensing part 4 connecting both ends of the wires 2 and 3 formed at one end of the protective pipe 1, a connector 11 provided on each of the wires 2 and 3 protruding from the other end of the protective pipe 1, and protection The filling member 9 is made of a mixed material of Si ₃ N ₄ and TiN filled in the pipe 1. A lid member 7 that closes the end portion is fixed to the distal end portion of the protective pipe 1, and the lid member 7 constitutes a temperature sensing portion 4. A mounting bracket 10 is fixed to the other end of the protective pipe 1 to attach a thermocouple to other components. A connector 11 is provided on the mounting portion 14 at the end of the protruding wire rods 2 and 3 on the mounting bracket 10 side. The connector 11 is configured to be connected to a terminal of the temperature measuring device. The attachment portions 14 of the wires 2 and 3 are insulated from each other by the insulating member 12.
[00 18 ]
In this thermocouple structure, the protective pipe 1 is made of Si ₃ N ₄ or SiC (silicon carbide) having excellent heat resistance, corrosion resistance, and heat shock resistance. When the protective pipe 1 is made of Si ₃ N ₄ , the protective pipe 1 is filled with a filling member 9 made of a mixed material made of Si ₃ N ₄ and TiN (titanium nitride). Si ₃ in the case of arranging the filler member 9 of the mixed material of Si ₃ N ₄ and TiN to N ₄ protective pipe 1, constituting the filling member 9 made of a non-shrink ceramics by mixing material is sintered In addition, it is possible to provide an extremely stable thermocouple structure without generating a gap or the like between the protective pipe 1 and the filling member 9.
[00 19 ]
In this thermocouple structure, for example, as the filling member 9, a mixed powder of Si powder 90 wt% and Ti powder 10 wt%, or in some cases, a mixed powder obtained by mixing some mixed silicon nitride powder with the mixed powder is silicon nitride. The protective pipe 1 is filled and sintered integrally in an N ₂ atmosphere. At this time, when powders of Si and Ti are accommodated in the protective pipe 1 and integrally sintered, if a large number of holes 15 are formed in the longitudinal direction of the protective pipe 1, Si and Ti react with each other to form Si. _A non-shrinkable ceramic composite material composed of ₃ N ₄ and TiN can be formed. That is, it is produced in a non-shrinkable ceramic composite material composed of Si ₃ N ₄ and TiN without sintering shrinkage. Next, the mounting bracket 10 and the glass layer 16 are attached to one end of the protective pipe 1 and the other end is attached to the lid member 7 to produce a thermocouple. After sintering, the hole 15 may be closed with a coating layer 17 of Si ₃ N ₄ , and the composite material constitutes a protective film for the wires 2 and 3. In this case, a pair of different types of wire rods 2 and 3 can be disposed on the mixed powder and integrally sintered in an N ₂ atmosphere. In some cases, after the filling member 9 is manufactured, a through hole is drilled from one end of the filling member 9 to the other end, and the through hole is inserted into a pair of different types of wires 2 and 3. Good.
[00 20 ]
One wire 2 is made of W-5% Re, the other wire 3 is made of W-26% Re, and the outer peripheral surface of either wire 2 or 3 is coated with an insulating layer made of ceramic powder. ing. The lead members of the wires 2 and ₃ are coated with an insulating layer 13 made of a paste obtained by dissolving Si ₃ N ₄ powder in a resin material or an oil and fat material. Further, tungsten (W) line is a high-melting material, its thermal expansion coefficient of 4.6 × 10 ^- is a ⁶ / K. The thermal expansion coefficient the Si ₃ N ₄ is 3.1 × 10 ^- since it is ⁶ / K, the Si ₃ N ₄ and W, the thermal expansion coefficient has approximate, therefore, the thermocouple by a combination of both Is preferable in consideration of the thermal expansion coefficient. However, since the thermal expansion coefficient is slightly different between the filling member 9 and the wires 2 and 3, the amount of thermal expansion changes due to the difference in thermal expansion at high temperatures, and the wires 2 and 3 may be disconnected. , 3 are preferably formed in a spiral shape so as to absorb the difference in thermal expansion.
[00 21 ]
The protective pipe 1 is made of Si ₃ N ₄ containing Y ₂ O ₃ , Al ₂ O ₃ , and SiO ₂ . In the longitudinal direction of the protective pipe 1, a large number of holes 15 are opened in a spaced state, and a coating layer 17 of Si ₃ N ₄ is coated on the surface of the filling member 9 that has entered the hole 15. Ventilation inside and outside the protective pipe 1 through the hole 15 is prevented, and O ₂ is prevented from entering the gap between the protective pipe 1 and the filling member 9 or the filling member 9.
[00 22 ]
In order to fix the fitting 10 to the end of the protective pipe 1, the filler 5 made of Ag—Cu—Ti powder is applied to the filling member 9 exposed in the hole 15 formed in the protective pipe 1. And the filling member 9 are fixed. In some cases, the filler 5 constituting the filler member 9 is embedded in the hole 15 of the protective pipe 1 on the fitting surface between the protective pipe 1 and the mounting bracket 10, and the filler 5 is formed by integral sintering. As a composite material, the protective pipe 1 and the mounting bracket 10 can be firmly adhered and fixed. A glass layer 16 containing Y ₂ O ₃ , Al ₂ O ₃ , SiO ₂ is applied to the end on the connector 11 side to seal the end of the protective pipe 1.
[00 23 ]
In addition to W-Re, the wires 2 and 3 can also be made from a combination of platinum and platinum rhodium, or a combination of W and WMo (Mo: 25%). The lid member 7 is made of silicon carbide SiC or Si ₃ N ₄ . When the lid member 7 is made of Si ₃ N ₄ , it is preferable that TiN powder is mixed in addition to Si ₃ N ₄ to form a non-shrinkable ceramic.
[00 24 ]
【The invention's effect】
The structure of the thermocouple according to the present invention is composed of a protective pipe made of ceramics as described above, and a conductor temperature sensing part sealed with a silicon nitride lid member is formed at the tip of the pipe. In particular, it has excellent heat shock resistance and is suitable for temperature control and temperature measurement in high-temperature furnaces such as molten metal furnaces, plasma melting furnaces, and electric furnaces. Since the mounting bracket fixed to the end of the protective pipe is firmly fixed to the insulator protective pipe, it is possible to provide a thermocouple with excellent heat resistance, heat shock resistance, and durability.
[00 25 ]
In particular, in this thermocouple structure, the filling member filled in the protective pipe is composed of a composite material of Si ₃ N ₄ and TiN formed by reaction sintering of Si and Ti, and the filling member is sintered. No shrinkage shrinkage is formed during sintering, non-shrinkable ceramics are formed, the wire is firmly held by the filling member in the protective pipe, and sealed in an atmosphere free from gases such as O _2. The structure does not form a gap between the protective pipe and the filling member, the gas such as O ₂ does not enter the protective pipe, and the wire does not oxidize and break. In addition, since the wire is firmly held by the filling member and protected by the protective pipe, it has excellent durability, high temperature measurement accuracy, and can provide a stable and reliable thermocouple. Suitable for measuring high temperature in the atmosphere.
[00 26 ]
This thermocouple structure is heat resistant and has excellent heat shock resistance, so it can be used repeatedly, reducing manufacturing costs, running costs, etc. compared to conventional NB or other materials. It can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a thermocouple structure according to the present invention.
2 is an enlarged cross-sectional view showing one embodiment of an end portion in the structure of the thermocouple of FIG. 1. FIG.
FIG. 3 is a cross-sectional view taken along line AA of FIG.
4 is an enlarged cross-sectional view showing a part of a wire rod in the structure of the thermocouple of FIG. 1. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Protective pipe 2, 3 Wire 4 Temperature sensing part 5 Filler 7 Lid member 9 Filling member 11 Connector 12 Insulating member 13 Covering layer 15 Hole 17 Coating layer

Claims (5)

Protection pipes, the above-spaced in a protective pipe extending longitudinally from one end to the other in different pair of conductive wire rod, both ends of the conductive wire rod formed at one end of the protective pipe made of heat-resistant ceramics thermocouple structure characterized in that it consists filling member is integrally sintered conductor temperature sensing unit that is connected, mixed powder consisting of filled Si and Ti in 及 beauty the protective pipe is in N ₂ atmosphere. The protective pipe is made of Si ₃ N ₄ or SiC , the filling member in the protective pipe is made of Si ₃ N ₄ and TiN, and the conductor wire is made of W-5% Re and W-26% Re. The thermocouple structure according to claim 1, wherein: Wherein the protective pipe numerous holes are spaced in the longitudinal direction is formed, claims on the surface of the filling member which is exposed from the hole after sintering, characterized in that Si ₃ N ₄ is coated The structure of the thermocouple as described in 1 or 2 . In order to fix the mounting bracket to the end of the protective pipe, Ag-Cu-Ti powder is applied to the filling member exposed in the hole formed in the protective pipe, and the mounting bracket and the filling member are attached. The thermocouple structure according to claim 3 , wherein the thermocouple structure is fixed. The conductor wire, the structure of the thermocouple as claimed in any one of claim 1 to 4, characterized in that bent spirally to absorb differential thermal expansion.

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