JPH0989683A - Structure of thermocouple - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize heat resistance, resistance against thermal shock and durability by placing a ceramic insulator in a protection pipe made of ceramic, placing thermocouple print bands made of tungsten-rhenium or platinum-rhodium extending separately in a lengthwise direction from an end to the other end on an outer face of the insulator and sealing the print bands in the pipe. SOLUTION: A column-like insulator 9 made of a composite material of TiN and Si3 N4 is filled in a protection pipe 1. A pair of conductor print bands 2, 3 separately extending from an end to the other end in a lengthwise direction provided on an outer face 16 of the insulator 9, a conductor print ring 8 for constituting a heat sensitive part 4 with both ends of the print bands 2, 3 formed at an end of the pipe 1, and a connection wire 5 for constituting a connector 11 are provided. The print band 2 is made of a W-5%Re material and the print band 3 is made of W-26%Re, while the print ring 8 is made of W-Re. Or a combination of platinum and rhodium may be used. The heat sensitive part 4 comprises a sintered thin film of Si3 N4 or SiC coated at an end of the pipe 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high temperature and high precision thermocouple structure.

[0002]

2. Description of the Related Art Conventional thermocouples have been developed for accurately measuring the temperature of high temperature liquids and gases. Thermocouple
Various measuring materials are adapted to measure the temperature in the temperature range of 300 ° C to 1400 ° C. The wires of the thermocouple are
In many cases, it is weak against an oxidizing or reducing atmosphere, and in general, wires are put in a protective pipe for use. In the conventional thermocouple, for example, a wire made of a W-Re material that constitutes the thermocouple is passed through one end from the other end in a protective pipe of Al ₂ O _{3 in} a separated state, the tip of the wire is joined, and the wire is Fill the extended protective pipe with insulating material such as MgO,
This protects the wire rods and prevents the wire rods from contacting each other to ensure heat resistance.

Further, as the protective tube for accommodating the thermocouple,
It is manufactured using the following materials. That is, the conventional protection tube is a heat-resistant sheath tube (heat-resistant temperature: 600 ° C), BN
(Heat-resistant temperature: 1000 ° C), porcelain (heat-resistant temperature: 1400)
℃), alumina (heat resistant temperature: 1600 ℃), high chrome steel (heat resistant temperature: 1050 ℃), alundum (heat resistant temperature: 1)
Various protective tubes such as 400 ° C.) are used. A thermocouple made of such a protective tube is damaged by one measurement and cannot be used again when used up to a heat resistant temperature. Therefore, it is usually about 600 ° C. to 800 ° C.
At present, it is used as a temperature measurement of about 000 ° C.

A thermocouple having a protective pipe made of Si ₃ N ₄ is disclosed, for example, in Japanese Patent Laid-Open No. 55-121972.
JP-A-61-246636, JP-A-2-2173
No. 61 has disclosed.

The airtight silicon nitride sintered body disclosed in JP-A-55-121972 can be applied to a protective tube of a thermocouple, and Si produced by the reaction sintering method has a limited bulk specific gravity.
_{A 3} N ₄ sintered body is humidified in a humidified N ₂ atmosphere to a specific dew point, and heat-treated at 1250 to 1500 ° C. to hermetically seal the surface.

Further, the protective tube for continuous temperature measurement of molten steel disclosed in Japanese Patent Laid-Open No. 61-246636 can be used as a protective tube for a thermocouple, and comprises a protective tube made of reaction-sintered silicon nitride and an alumina inner tube. This is a protective tube made by filling AlN powder between them, and further filling alumina wool on top of the AlN powder, which reduces the erosion rate by molten steel and enables measurement of molten steel temperature for a long time. .

Furthermore, the reaction-sintered silicon nitride ceramics disclosed in Japanese Patent Laid-Open No. 2-217361 can be used as a protective tube for a thermocouple, and a compact formed by molding Si powder can be used.
It is a product obtained by reaction sintering at about 1200 to 1600 ° C. in an N ₂ atmosphere.

[0008]

However, in the conventional protective tube for protecting the thermocouple, the protective tube is actually damaged considerably at an ambient temperature of 1000 ° C. or higher, or the conventional thermocouple is damaged. Then, some of them are discarded after one use. Therefore, the conventional thermocouples are currently high in cost and difficult to measure the temperature of the high temperature furnace or the molten metal. For example, when the thermocouple is formed in the shape of a pipe having a small diameter, there is a manufacturing problem in order to properly adjust the strength of the protective tube that protects the thermocouple and the density of the filler in the protective tube. In addition, if the protective tube is made of BN,
_Since it oxidizes in the presence of ₂ , O ₂ in the furnace is exhausted before use.

Regarding the conventional thermocouple, as described above, A
In the thermocouple in which the protective pipe was made of l ₂ O ₃ , Al ₂ O
The heat resistant temperature of ₃ is about 800 ° C. That is, Al ₂ O ₃
In the protective pipe of, the enclosed MgO is porous and
O ₂ easily penetrates inside the porous O, and W-5% Re and W-26% Re used as high temperature thermocouples are
There is a problem that the presence of ₂ easily oxidizes and breaks the wire. Therefore, in the thermocouple made of the Al ₂ O ₃ protective pipe as described above, the durability of the thermocouple must be sacrificed in the temperature measurement in the temperature atmosphere of 800 ° C. or higher, which is a special temperature measurement. There were many problems such as using technology.

Further, as a thermocouple structure, even when the protective tube is made of reaction-sintered silicon nitride, a pair of different kinds of wires extending in the longitudinal direction from one end to the other end are arranged in the protective tube. O ₂ but unless select an appropriate material as a filling member for filling the protective tube, a gap is generated between the protective tube inner surface and the filling member, the line material present in the protective tube
There is a problem that it will be oxidized and broken, or it will be damaged by heat shock.

[0011]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems. A protective pipe is formed of a heat-resistant ceramic such as Si ₃ N ₄ or SiC, and a space is formed in the protective pipe. A ceramic insulator that is densely embedded is arranged, and a tungsten (W) -rhenium (Re) alloy or platinum (Pt) -rhodium (R) is provided on the outer surface of the insulator.
By providing the thermocouple printed band from h) and enclosing the thermocouple printed band in the protective pipe, it is possible to provide a thermocouple structure having excellent heat resistance, heat shock resistance, and durability.

The present invention is a protective pipe made of heat-resistant ceramics, and TiN and S fitted in the protective pipe.
A columnar insulator made of a composite material with i ₃ N ₄ , a pair of different printed strips printed on the outer surface of the insulator so as to extend longitudinally from one end to the other end, the protection pipe The present invention relates to a thermocouple structure composed of a temperature-sensing part formed at one end of the printed strip and connected to both ends of the printed strip, and a connector provided at the other end of the protective pipe to be connected to the printed strip.

Alternatively, according to the present invention, a protective pipe made of heat-resistant ceramics, a columnar base body fitted in the protective pipe, and TiN and Si ₃ N ₄ coating the outer periphery of the base body.
And an insulating cover made of a composite material of a composite material, and a pair of printed bands of different types printed so as to extend longitudinally from one end to the other end on the outer surface of the insulator,
The present invention relates to a thermocouple structure including a temperature-sensing portion formed at one end of the protective pipe, the thermosensitive portion being connected to both ends of the printed strip, and a connector provided at the other end of the protective pipe to be connected to the printed strip.

One of the print bands is W-5% R.
e, and the other of the printed bands is W-26% Re. Further, the temperature sensing portion is formed by sintering a thin film of Si ₃ N ₄ or SiC coated on the end portion of the protection pipe. The protective pipe is made of Si ₃ N ₄ or SiC.

The connector provided at the end of the protective pipe is composed of lead wires which are metallized with Ag-Cu-Ti powder and connected to the printed strip. Further, the printed strip and the lead wire are joined together so as not to short-circuit with each other on the Al ₂ O ₃ cylinder arranged on the outer surface of the portion of the insulator protruding from the protection pipe.

Further, a portion where the surface of the insulator is exposed without printing the printed band is adhered to the inner surface of the protective pipe.

In this thermocouple structure, Si ₃ N ₄ is selected as the material of the protective tube for protecting the thermocouple to produce a protective pipe, while insulating with a composite material in which Si ₃ N ₄ and TiN are mixed. A body is prepared, W-Re is pulverized on the outer surface of the insulator, and the finely divided powder paste is printed from one end to the other on a surface of 1/2 or less of the circumference to print two strips. Since the entire circumference of the tip of the insulator was printed with the paste to connect the two printed strips and the printed strip was inserted into the protective pipe and sintered, it was durable in a high temperature atmosphere. It is possible to provide a thermocouple with extremely excellent reliability and reliability. Further, the composite material in which 10 to 15% of Si ₃ N ₄ is mixed with TiN does not cause shrinkage due to sintering, but rather expands slightly, and the insulator adheres to the protective pipe of Si ₃ N ₄ , and the above-mentioned protection is performed. O ₂ is prevented from entering the area of the printed strip located between the pipe and the insulator, so that the printed strip of the thermocouple is not broken by oxidation and the durability can be improved.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a thermocouple structure according to the present invention will be described below with reference to the drawings. 1 is a sectional view showing an embodiment of the structure of a thermocouple according to the present invention, FIG. 2 is an enlarged sectional view taken along the line AA of FIG. 1, and FIG. 3 is a printed band printed on the structure of the thermocouple of FIG. It is a perspective view which shows the insulated body.

The structure of this thermocouple is mainly composed of a protection pipe 1 made of heat-resistant and corrosion-resistant ceramics, and a columnar insulator made of a composite material of TiN and Si ₃ N ₄ fitted in the protection pipe 1. 9, a pair of different conductor printed strips 2 and 3 printed on the outer surface 16 of the insulator 9 so as to extend longitudinally from one end to the other end, and a print formed on one end of the protective pipe 1. From the conductor print ring 8 that constitutes the temperature-sensitive portion 4 in which both ends of the belts 2 and 3 are connected, and the connection line 5 that constitutes the connector 11 that is connected to the printed belts 2 and 3 provided at the other end of the protective pipe It is configured. One printed strip 2 is made of W-5% Re material,
The other print band 3 is made of W-26% Re, and the print ring 8 is made of W-Re. Further, as the print bands 2 and 3 and the print ring 8, in addition to W-Re, a combination of platinum and platinum rhodium, or W and W
It can also be produced from a combination with Mo (Mo: 25%). The temperature sensitive portion 4 is formed by sintering a thin film 7 of Si ₃ N ₄ or SiC coated on the end portion of the protective pipe 1.

Further, the connector 11 provided at the end of the protective pipe 1 has the printed bands 2 and 3 made of a silver brazing material and Ag-Cu-.
It is composed of connecting wires, that is, lead wires 5, which are metallized with Ti powder and connected to each other. Al ₂ O ₃ arranged on the outer surface 16 of the portion of the insulator 9 protruding from the protective pipe 1.
The printed bands 2 and 3 and the lead wire 5 are joined to the cylindrical body 14 so that the printed bands 2 and 3 do not short-circuit with each other. Further, printed strips 2, 3 are formed on the insulator 9.
The part 6 where the surface of the insulator 9, that is, the outer surface 16 is exposed without being printed, is adhered to the inner surface of the protective pipe 1.

A mounting bracket 10 is fixed to the other end of the protective pipe 1 for mounting a thermocouple on another component. The mounting portion at the end of the protruding lead wire 5 on the mounting bracket 10 side forms the connector 11. The connector 11 is
It is configured to be connected to a terminal of a temperature measuring device. The fitting 10 and the protective pipe 1 are joined together by converting the powder paste of Si and Ti filled in the hole 15 of the protective pipe 1 into a composite material by sintering, and both are firmly adhered by the composite material. It is fixed.

In this thermocouple structure, the protective pipe 1
Is Si ₃ with excellent heat resistance, corrosion resistance and heat shock resistance.
Made from N ₄ or Silicon Carbide SiC. When the protective pipe 1 is made of Si ₃ N ₄ , it is preferable that the insulator 9 fitted in the protective pipe 1 is made of a mixed material of Si ₃ N ₄ and titanium nitride TiN. Si ₃ N ₄
When the insulator 9 of the filling material of the mixed material of Si ₃ N ₄ and TiN is arranged in the protective pipe 1 of 1., the insulator 9 made of non-shrinkable ceramic is obtained by sintering the mixed material.
It is possible to provide an extremely stable structure of the thermocouple without forming a gap or the like between the protective pipe 1 and the insulator 9. Further, tungsten (W) line is a high-melting material, its thermal expansion coefficient of 4.6 × 10 ^- is a ⁶ / K. In addition, the coefficient of thermal expansion of Si ₃ N ₄ is 3.1 × 10
^-6 / K, Si ₃ N ₄ and W have similar thermal expansion coefficients. Therefore, when a thermocouple is formed by a combination of both, it is preferable in consideration of the thermal expansion coefficient. Is.

The protective pipe 1 is made of Si ₃ N ₄ ,
It can be manufactured from Si ₃ N ₄ containing Y ₂ O ₃ , Al ₂ O ₃ , and SiO ₂ . In the longitudinal direction of the protection pipe 1,
A large number of holes 15 are formed in a spaced state, and Si is filled in the holes 15.
The powder mixture containing Ti and Ti as the main components is filled and integrally sintered in an N ₂ atmosphere to be converted into non-shrinkable ceramics, and the protective pipe 1 and the insulator 9 are firmly bonded.
In this case, the surface of the filling member of the filled composite material is S
i ₃ N ₄ is coated, and the coating layer prevents ventilation inside and outside the protective pipe 1 through the holes 15.

In order to fix the mounting member 10 to the end portion of the protection pipe 1, Ag-Cu-Ti powder is applied to the insulator 9 exposed in the hole 15 formed in the protection pipe 1 to form the mounting member 10. The insulator 9 is fixed. A glass layer 13 containing Y ₂ O ₃ , Al ₂ O ₃ , and SiO ₂ is applied to the end portion on the connector 11 side to seal the end portion of the protective pipe 1.

In the structure of this thermocouple, for example, the insulator 9 forming the core is 90 wt% of Si powder and 1 wt of Ti powder.
When a mixed powder with 0 wt% or, in some cases, a mixed powder obtained by mixing a small amount of silicon nitride powder with the mixed powder is sintered in an N ₂ atmosphere, Si and Ti react with each other to form Si ₃ N ₄ and TiN. A non-shrinkable ceramic composite material composed of That is, it is formed into a non-shrinkable ceramic composite material composed of Si ₃ N ₄ and TiN without sintering shrinkage. Then
Different kinds of conductor print bands 2 and 3 are printed on the outer surface of the insulator 9, and the conductor print ring 8 is attached to the end of the insulator 9.
Print. Then, a paste of a mixed powder of 90 wt% of Si powder and 10 wt% of Ti powder is applied to the surface of the insulator 9 on which the conductor film is printed, and the paste is fitted into the protective pipe 1 made of silicon nitride, and N ₂ By integrally sintering in an atmosphere, the paste will not sinter and shrink Si ₃ N ₄ and T
Converted to a non-shrinkable ceramic composite composed of iN,
The insulator 9 is fixed to the protective pipe 1. At this time, when powder of Si and Ti is housed in the protective pipe 1 and integrally sintered, if a large number of holes 15 are opened in the longitudinal direction of the protective pipe 1, Si and Ti react with each other and Si _A non-shrinkable ceramic composite material composed of ₃ N ₄ and TiN is produced. After sintering, the holes 15 may be closed with the coating layer 17 of Si ₃ N ₄ , and the insulator 9 of the composite material in the protective pipe 1 may be the wire rod 2,
3 will constitute the protective film.

Next, another embodiment of the structure of the thermocouple according to the present invention will be described with reference to FIG. Since the structure of the thermocouple of this embodiment has the same structure as that of the above embodiment except that the structure of the insulator is different, the same parts are designated by the same reference numerals and the duplicate description will be omitted. To do. In the structure of the thermocouple of this embodiment, the insulator 19 corresponding to the insulator 9 is used.
Is composed of a columnar substrate 20 fitted in the protective pipe 1 and an insulating coating 18 made of a composite material of TiN and Si ₃ N ₄ coating the outer periphery of the substrate 20. On the outer surface of the insulating cover 18 of the insulator 19, a pair of different print bands 2 and 3 are printed so as to extend from one end to the other in the longitudinal direction at a distance. Print obi 2,3
By inserting the insulator 19 on which is printed into the protective pipe 1 and integrally sintering the same, the insulator 19 and the protective pipe 1 are fixed to each other.

[0027]

As described above, the structure of the thermocouple according to the present invention comprises the protective pipe made of ceramics,
Since the temperature sensitive part is formed at its tip, it is heat resistant and corrosion resistant, and in particular it has excellent heat shock resistance, temperature control of high temperature furnaces such as molten metal furnace, plasma melting furnace, electric furnace,
Suitable for temperature measurement. This thermocouple structure is particularly suitable for measuring high temperatures in an oxidizing / reducing atmosphere. Further, since the mounting metal fitting fixed to the end of the protection pipe is firmly fixed, it is possible to provide a thermocouple having excellent heat resistance, excellent heat shock resistance, and durability. In particular, the insulator filled in the protective pipe is composed of a composite material of Si ₃ N ₄ and TiN formed by reacting and sintering Si and Ti, and the insulator has no sintering shrinkage during sintering. Since non-shrinkable ceramics are formed, a dense structure can be formed inside the protective pipe, and the printed strip can be firmly held and protected by a structure that prevents O ₂ from entering, providing excellent durability and temperature measurement. The accuracy is high, and a stable and reliable thermocouple can be provided.

Since the structure of this thermocouple is heat resistant and excellent in heat shock resistance, it can be used repeatedly, and the manufacturing cost and running are higher than those of conventional ones made of materials such as NB. The cost etc. can be reduced significantly.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the structure of a thermocouple according to the present invention.

FIG. 2 is an enlarged cross-sectional view showing one embodiment taken along line AA in FIG.

3 is a perspective view showing an insulator having a printed band printed on its surface and a lead wire joined to the insulator in the structure of the thermocouple of FIG. 1. FIG.

FIG. 4 is an enlarged sectional view showing another embodiment taken along line AA in FIG.

[Explanation of symbols]

 1 Protective Pipe 2, 3 Printed Band 4 Temperature Sensitive Part 5 Lead Wire 6 Gap 7 Thin Film 8 Printed Ring 9, 19 Insulator 10 Mounting Bracket 11 Connector 15 Hole 17 Coating Layer 18 Insulation Cover 20 Base

Claims (8)

[Claims] 1. A protective pipe made of heat-resistant ceramics, a columnar insulator made of a composite material of TiN and Si ₃ N ₄ fitted in the protective pipe, and one end to the other end on the outer surface of the insulator. A pair of conductor printed strips of different types printed so as to be spaced apart in the longitudinal direction, a conductor temperature-sensing portion formed at one end of the protective pipe, the conductor temperature-sensing portion being connected to both ends, and the protective pipe. A structure of a thermocouple composed of connectors which are respectively connected to the printed strips provided at the other end. 2. A protective pipe made of heat-resistant ceramics, a columnar base body fitted in the protective pipe, and an insulating coating body made of a composite material of TiN and Si ₃ N ₄ coating the outer periphery of the base body. An insulating body, a pair of conductor printed strips of different types printed on the outer surface of the insulator so as to extend longitudinally from one end to the other end, and the printed strip formed on one end of the protective pipe A thermocouple structure composed of a conductor temperature-sensing portion having both ends thereof connected, and a connector provided at the other end of the protective pipe and connected to the printed strip respectively. 3. The thermocouple structure according to claim 1, wherein one of the printed bands is made of W-5% Re and the other printed band is made of W-26% Re. 4. The protective pipe is made of Si ₃ N ₄ or SiC.
The thermocouple structure according to any one of claims 1 to 3, which is manufactured from. 5. The temperature sensing part is formed by sintering a thin film of Si ₃ N ₄ or SiC coated on the end of the protective pipe. Thermocouple structure. 6. The connector according to claim 1, wherein the connector provided at the end of the protective pipe is composed of lead wires which are metalized with Ag—Cu—Ti powder and connected to the printed band. The structure of the thermocouple according to item 1. 7. The printed strip and the lead wire are joined together so as not to be short-circuited with each other on an Al ₂ O ₃ cylindrical body arranged on the outer surface of the portion of the insulator protruding from the protection pipe. The structure of the thermocouple according to claim 6. 8. The thermocouple according to claim 1, wherein a portion where the surface of the insulator is exposed without printing the printed band is adhered to an inner surface of the protective pipe. Structure.