JPH0989681A - Structure of thermocouple - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure of a thermocouple wherein a high temperature can be highly accurately measured. SOLUTION: A structure of a thermocouple comprises a protection pipe 1 made of heat-resistant ceramic, a pair of different kinds of wires 2, 3 separately placed in the protection pipe 1 and extending from an end to the other end, a thin film 4 forming a heat sensing part made of tungsten alloy placed at a tip of the protection pipe 1 and connected respectively to the wires 2, 3 and a coating layer 5 made of heat-resistant ceramic for coating the thin film 4 for preventing it from being exposed outside. The protection pipe 1 is made of Si3 N4 , while a filling member 9 made of mixed powder comprising Si3 N4 and TiN is filled in the protection pipe.

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 A conventional thermocouple was developed to accurately measure the temperature of a high-temperature liquid or gas, and it connects two ends of two different types of conductor wires and connects them. When placed in the temperature measurement region, the temperature is measured using the principle that an electromotive force is generated due to the temperature difference between two points. Since such a thermocouple measures the temperature in the temperature range of 300 ° C. to 1400 ° C., various measuring materials are adapted. The wires of the thermocouple are often weak against an oxidizing or reducing atmosphere, and generally, the wires are put in a protective tube and used.

The conventional protective tube for accommodating the thermocouple is made of the following materials. That is,
Conventional protective tubes are BN (heat-resistant temperature: 1000 ° C), porcelain (heat-resistant temperature: 1400 ° C), alumina (heat-resistant temperature: 16)
Various protection tubes such as high temperature steel (00 ° C), high chrome steel (heat resistant temperature: 1050 ° C), alundum (heat resistant temperature: 1400 ° C) are used. A thermocouple made of such a protective tube will be damaged by one measurement if used up to the heat resistant temperature,
Since it cannot be used again, it is usually 6 for temperature measurement.
At present, it is used in an atmosphere having a temperature of about 00 ° C to 800 ° C and a high temperature of about 1000 ° 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 protection tube for protecting the thermocouple, when the protection tube is used at a temperature of 1000 ° C. or higher, the protection tube is considerably damaged. Therefore, the conventional thermocouple has a difficulty in measuring the temperature of the high temperature furnace and the molten metal under the present circumstances. 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. Further, the thermocouple to prepare a protective tube BN, to oxidize in the presence of O _2, are using the exhaust the O ₂ in the furnace for temperature measurement at present.

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. However, unless a proper material is selected as a filling member to be filled in the protective tube, a gap is generated between the inner surface of the protective tube and the filling member, or O ₂ enters the filling member,
The wire rod oxidizes with O ₂ existing in the protection tube to break the wire,
Alternatively, there is a problem that it is damaged by heat shock.

[0010]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems by forming a protective pipe from a heat-resistant ceramic such as Si ₃ N ₄ and by using tungsten (W) -rhenium (Re). By making a thermocouple wire from alloy or platinum (Pt) -rhodium (Rh) and synthesizing TiN etc. on the outside of the thermocouple wire and enclosing the thermocouple wire in a protective pipe, heat resistance and heat resistance An object of the present invention is to provide a structure of a thermocouple which has excellent shock resistance and can measure temperature with high accuracy at high temperature and high sensitivity.

According to the present invention, a protective pipe made of heat-resistant ceramics, a pair of conductor wires of different kinds which are spaced apart from each other in the protective pipe and extend in the longitudinal direction from one end to the other end are arranged at the tip of the protective pipe. The present invention relates to a structure of a thermocouple comprising a conductive thin film which constitutes a temperature sensitive part made of a tungsten alloy and which is connected to each of the wires, and a coating layer made of heat resistant ceramics which covers the thin film so as not to be exposed to the outside.

The protective pipe is made of Si ₃ N ₄ , and a filling member made of Si ₃ N ₄ and TiN is filled in the protective pipe.

Further, a lid member having holes formed therein for inserting the tips of the wire rods is fixed to the tip end of the protective pipe, and the tip end of the wire rod fitted in the hole portions is fixed to the lid member. The thin film is attached to connect and the coating layer is coated to cover the thin film.

Further, the thin film is formed by applying a tungsten powder paste to the lid material and attaching the lid material to the protective pipe with the paste material interposed therebetween, and integrally sintering the thin film.

The coating layer facing the thin film is processed to have a thickness of 0.5 mm or less, and is structured to have high sensitivity.

One of the wires is made of W-5% Re, the other wire is made of W-26% Re, and the thin film is made of a powdery paste coating layer in which W is mixed with Mo or Ti. Become.

The lead member of the wire is made of Si ₃ N
₄ A paste prepared by dissolving powder in a resin material or oil material is coated.

Alternatively, the lead member of the wire is made of Si ₃ N
₄ is inserted into a pair of through holes punched in a calcined member containing TiN, and the calcined member having the wire rod inserted into the through hole is fitted into the protective pipe and integrally sintered.

Alternatively, in this thermocouple structure, the wire is formed into a spiral with a large pitch and is housed in a rod-shaped member made of TiN in Si ₃ N ₄ , and then the rod-shaped member is calcined. It is fitted in a protective pipe and integrally sintered.

In this thermocouple structure, the conductor thin film forming the temperature sensitive portion is arranged at the tip of the protective pipe, and the temperature sensitive portion is covered with a thin coating layer, so that the sensitivity is extremely high. High temperature can be measured with high accuracy. Moreover,
The structure of this thermocouple is that the conductor wire in the protective pipe is enclosed by the protective pipe and the thin film at its tip, and the coefficient of linear expansion in the protective pipe is almost the same as that of the wire. Since it is filled with non-shrinkable ceramics that fills the gap, the wire is stably held in the protective pipe, O ₂ does not enter, the wire does not oxidize and break, and it is heat resistant and heat shock resistant. It is possible to provide a thermocouple having excellent durability and excellent durability. Further, the structure of this thermocouple can be used, for example, for temperature measurement in a high temperature furnace, ceramics sintering, high pressure gas heat treatment, iron melting furnace, Al melting furnace, and the like.

[0021]

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 the thermocouple according to the present invention, FIG. 2 is an enlarged sectional view showing an end portion of the structure of the thermocouple of FIG. 1, and FIG. 3 is a view of the structure of the thermocouple of FIG. FIG. 4 is a side view showing the end face on the warm part side, and FIG. 4 is an enlarged sectional view showing a part of the wire rod in the structure of the thermocouple of FIG.

The structure of this thermocouple is mainly composed of heat resistance,
Protective pipe 1 made of ceramics having excellent corrosion resistance and heat shock resistance, a pair of conductor wires 2 and 3 of different kinds which are spaced apart from each other in the protective pipe 1 and extend longitudinally from one end to the other end Is arranged at one end of the wire rod 2,
3, a conductor thin film 4 constituting a temperature sensitive part made of a tungsten alloy, and a coating layer 5 made of heat-resistant and dense ceramics which covers the thin film 4 so as not to be exposed to the outside. At the other end of the protective pipe 1, there is a mounting bracket 10 for mounting a thermocouple to other parts.
Has been fixed. On the mounting metal fitting 10 side, the mounting portions 11 at the ends of the wires 2 and 3 are configured to project, and the mounting portions 11 are connected to the terminals of the temperature measuring device. Wires 2, 3
The mounting portions 11 of are insulated from each other by an insulating member 12.

In this thermocouple structure, the protective pipe 1
Is made of Si ₃ N ₄ or silicon carbide SiC, which is heat resistant and has excellent heat shock resistance, and has a large number of holes 15 spaced apart in the longitudinal direction. Protect pipe 1 with Si ₃ N ₄
In the case of the above manufacturing method, the protective pipe 1 is filled with the filling member 9 made of the composite material of the mixed powder of Si and Ti.
Si ₃ N ₄ , Si and T are placed in the protection pipe 1 of Si ₃ N ₄ .
When the mixed powder with i is filled, the mixed powder is sintered to form a filling member 9 made of a non-shrinkable ceramic composite material, and a gap or the like is formed between the protective pipe 1 and the filling member 9. It is possible to provide a very stable thermocouple structure without any generation.

In the structure of this thermocouple, for example, as the filling member 9, 90 wt% of Si powder and 10 wt% of Ti powder are used.
Mixed powder with, and in some cases, some S in the mixed powder.
A powder mixture of i ₃ N ₄ powder is filled in a silicon nitride protective pipe 1 and integrally sintered in an N ₂ atmosphere. At this time, when the powder of Si and Ti is housed in the protective pipe 1 and integrally sintered, a large number of holes 1 are formed in the longitudinal direction of the protective pipe 1.
If 5 is left open, Si reacts with Ti and Si ₃ N ₄
A composite material of non-shrinkable ceramics composed of TiN and TiN is obtained. That is, it is formed into a non-shrinkable ceramic composite material composed of Si ₃ N ₄ and TiN without sintering shrinkage. At this time, the fitting 10 and the glass layer 1 are attached to one end of the protective pipe 1.
6 can be attached and the other end can be attached to the lid member 7. The mounting bracket 10 has a hole 15 formed in the protective pipe 1.
Since the above-mentioned mixed powder is infiltrated and filled in, it is firmly fixed to the protective pipe 1 by integral sintering.

On the other hand, in the structure of this thermocouple, the wire rod has a large pitch, that is, a gentle spiral shape. The rod-shaped member is calcined and dried, and then the rod-shaped member is calcined, and the rod-shaped member is fitted into the protection pipe and integrally sintered, so that it can be formed.

Further, after the integral sintering, the composite material filled in the hole 15 exposed to the outside may be covered with the coating layer 17 of Si ₃ N ₄ , and the composite material in the protective pipe 1, that is, the filling member. 9 forms a protective film for the wires 2 and 3. In this case, a pair of different types of wire rods 2 and 3 may be arranged in the mixed powder and integrally sintered in an N ₂ atmosphere. In some cases, after forming the filling member 9, a through hole is formed from one end of the filling member 9 to the other end,
A pair of wire rods 2 and 3 of different types may be inserted through the through hole.

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 ^{- 6}
Since / K, Si ₃ N ₄ and W have similar thermal expansion coefficients. Therefore, when a thermocouple is formed by a combination of the two, it is preferable from the viewpoint of the thermal expansion coefficient. is there.

A lid member 7 having holes 8 into which the tips of the wire rods 2 and 3 are fitted is fixed to the tip of the protective pipe 1. The lid member 7 has a conductor thin film 6 interposed in the hole 8. The conductor thin film 4 is attached so as to connect the tips of the wire rods 2 and 3 that have been fitted in and the coating layer 5 is coated so as to cover the thin film 4. The thin film 4 is integrally sintered by applying a tungsten powder paste to the lid material 7, attaching the lid material 7 to the protective pipe 1 with the paste material interposed therebetween. Further, the coating layer 5 facing the thin film 4 is processed to have a thickness of 0.5 mm or less.

Further, one wire 2 is made of W-5% Re, and the other wire 3 is made of W-26% Re. As the wire rods 2 and 3, in addition to W-Re, a combination of platinum and platinum rhodium, or W and WMo (Mo: 25
%). Thin film 4,
6 is W (Mo), Mn (manganese), T
It is composed of a powdery paste-like coating layer in which i (titanium) is mixed, and the wires 2 and 3 are electrically connected by sintering. The lid member 7 is made of silicon carbide SiC or Si ₃ N ₄ . The cover material 7 is Si ₃ N ₄
In the case of fabricated is, Si ₃ the Ti powder is mixed in addition to the N _4, Si ₃ N ₄ and is preferably on the junction constituting a non-shrink ceramics as a composite material of TiN. Further, the lead members of the wires 2 and ₃ are coated with a coating layer 13 made of a paste obtained by dissolving Si ₃ N ₄ powder in a resin material or an oil / fat material.
Prevents short-circuiting of the wires 2 and 3 inside.

Alternatively, the structure of this thermocouple can be constructed as follows. First, the lead members of the conductor wires 2 and ₃ are inserted into a pair of through holes punched in a calcining member containing TiN in Si ₃ N ₄ , and the calcining members in which the wire rods 2 and 3 are inserted into the through holes are protected pipes. It can be manufactured by fitting into 1 and sintering integrally. At this time, if a paste of powder of Si and Ti is applied to the surface of the calcined member and inserted into the protective pipe 1 and integrally sintered in that state, the calcined member is converted into the filling member 9 and the filling member is 9 and protection pipe 1
And are firmly adhered and fixed. The calcined member can be fired without applying pressure, and is made of Si ₃ N ₄ —TiN ceramics, that is, non-shrinkable ceramics that slightly expands depending on the compounding ratio of the powder during firing.

[0031]

Since the structure of the thermocouple according to the present invention is constructed as described above, the thin film constituting the temperature sensing portion is arranged at the tip of the protective pipe made of heat resistant and heat shock resistant ceramics, Since the temperature sensing portion is coated with a thin coating layer, it is possible to measure the temperature of a gas or liquid object to be measured with high sensitivity and high accuracy even if the object is at a high temperature. It is possible to provide a thermocouple that is heat resistant, has excellent heat shock resistance, and is highly durable.
In addition, since the structure of this thermocouple is heat resistant and excellent in heat shock resistance, it can be used repeatedly, resulting in lower manufacturing costs, running costs, etc. than those manufactured using conventional materials such as NB. It can be greatly reduced.

In addition, the structure of this thermocouple is such that a protective pipe made of silicon nitride is filled with a calcined member containing Si ₃ N ₄ and TiN, and the calcined member is sintered to prevent shrinkage of the composite material. Since the ceramic filling member is filled, the protective pipe and the filling member are closely joined to each other, no gap is formed between the filling member and the protective pipe, and O ₂ does not enter.
Moreover, a pair of different wires can be firmly held in the protective pipe, and a highly durable thermocouple can be provided.

[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 an embodiment of an end portion in the thermocouple structure of FIG.

3 is a side view showing an end face of the structure of the thermocouple of FIG. 1. FIG.

FIG. 4 is an enlarged cross-sectional view showing a part of a wire rod in the thermocouple structure of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Protective pipe 2,3 Wire rod 4,6 Thin film 5 Covering layer 7 Lid material 8 Through hole 9 Filling member 11 Mounting part 13 Covering layer

Claims (9)

[Claims] 1. A protection pipe made of heat-resistant ceramics, a pair of conductor wires of different kinds which are spaced apart from each other in the protection pipe and extend in the longitudinal direction from one end to the other end, and which are arranged at the tip of the protection pipe. A thermocouple structure comprising: a conductor thin film, which is connected to each of the wires, and which constitutes a temperature-sensing portion made of a tungsten alloy; and a coating layer made of heat-resistant ceramics which covers the thin film so as not to be exposed to the outside. 2. The protection pipe is made of Si ₃ N ₄ ,
The structure of the thermocouple according to claim 1, wherein the protective pipe is filled with a filling member made of Si ₃ N ₄ and TiN. 3. A lid member having holes formed therein for inserting the tips of the wire rods is fixed to the tip end portion of the protection pipe, and the tip end of the wire rod fitted in the hole portions is fixed to the lid member. The thermocouple structure according to claim 1 or 2, wherein the thin film is attached so as to be connected, and the coating layer that coats and protects the thin film is coated. 4. The thin film is integrally sintered by applying a tungsten powder paste to the lid material and attaching the lid material to the protective pipe with a paste material interposed therebetween.
The structure of the thermocouple described in. 5. The thermocouple structure according to claim 1, wherein the coating layer facing the thin film is processed to have a thickness of 0.5 mm or less. 6. One of the wire rods is made of W-5% Re, the other wire rod is made of W-26% Re, and the thin film is made of a powdery paste-like coating layer in which W and Mo are mixed. The structure of the thermocouple according to any one of claims 1 to 5. 7. The structure of the thermocouple according to claim 1, wherein the lead member of the wire is coated with a paste obtained by dissolving Si ₃ N ₄ powder in a resin material or an oil and fat material. 8. The lead member of the wire is made of Si ₃ N ₄
The calcined member containing iN is inserted into a pair of through holes formed in the calcined member, and the wire rod is inserted into the through hole. The calcined member is fitted into the protective pipe and integrally sintered. The structure of the thermocouple according to any one of items. 9. The wire rod is formed into a spiral shape having a large pitch by being housed in a rod-shaped member made of TiN in Si ₃ N ₄ and then molded, and then the rod-shaped member is calcined and fitted into the protective pipe. The thermocouple structure according to claim 1, wherein the thermocouple is integrally sintered.