JPH0755586A - Sheathed thermocouple - Google Patents

Abstract

PURPOSE:To prevent insulation deterioration of a sheathed thermocouple in prolonged use or preservation by using non-oxide ceramic as an inorganic insulating matter of the sheathed thermocouple. CONSTITUTION:A sheath 1 is filled with a non-oxide ceramic 3a that does not allow moisture to react carbon dioxide or the like. The ceramic 3a herein used is a nitride compound such as NB or AIN, a carbide compound such as Sic or ZrC or a combination of the above compounds that do not react each other in a range of application temperature in a powder or a granule. Excellent in high conductivity, electric insulating property an heat resistance, the ceramic 3a has a high temperature upper limit near a high temperature limit and moreover is high in measuring accuracy when a temperature measurement is made using this thermocouple. With difficulty in reacting moisture, the ceramic 3a enables the prevention of insulation deterioration in the prolonged use of the sheathed thermocouple and in the preservation thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheath thermocouple so that insulation deterioration does not occur.

[0002]

2. Description of the Related Art A sheath thermocouple is used to measure the temperature of a high temperature portion. As shown in FIG. 2, the sheath thermocouple accommodates a thermocouple wire 2 inside a sheath 1 as an ultrafine tube made of stainless steel or heat-resistant steel, and an inorganic wire is placed between the wires 2 inside the sheath 1. It is filled with magnesium oxide (MgO) 3 as an insulator.

The outer diameter of the sheath 1 is 0.25 to 0.25.
It is about 3 mm, and the outer diameter dimension of the wire 2 is 0.05 to 1.
It is about 3 mm. 2A shows a single-element sheath, and FIG. 2B shows a double-element sheath thermocouple.

[0004]

However, magnesium oxide easily reacts with water and changes as follows.

MgO + H ₂ O → Mg (OH) ₂ Therefore, the sheath thermocouple is liable to become unusable due to insulation deterioration due to long-term use or during long-term storage.

Therefore, an object of the present invention is to provide a sheath thermocouple that solves the above problems.

[0007]

[Means for Solving the Problems] The structure of the present invention for attaining the above object is such that the wire constituting the thermocouple is housed inside the ultrafine tube and the inside of the ultrafine tube is filled with an inorganic insulator. In the sheath thermocouple, a non-oxide ceramic is used as the inorganic insulator.

[0008]

The non-oxide ceramic is filled inside the sheath, and the non-oxide ceramic is difficult to react with moisture. Therefore, even if the sheath thermocouple is used for a long period of time or stored for a long period of time, the sheath thermocouple does not cause insulation deterioration.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. Since the present embodiment is an improvement of a part of the conventional sheath thermocouple, the same parts as those of the prior art are designated by the same reference numerals, and the description thereof will be omitted. Only different parts will be described.

The construction of the sheath thermocouple according to the present invention is shown in FIG.
Shown in. FIG. 1 (a) is a single element, FIG. 1 (b)
Shows a double-element sheath thermocouple, and in each case, the sheath 1 is filled with a non-oxide ceramic 3a that does not react with moisture, carbon dioxide gas or the like instead of the conventional magnesium oxide.

As non-oxide ceramics, nitride type BN, AlN, Si ₃ N ₄ , ZrN, TiN, TaN, M are used.
o ₂ N, NbN or a combination of these which do not react with each other in the operating temperature range is used,
Of carbide Sic, ZrC, Wc, the combination of which do not react with one another in Cr ₃ C _2, TiC or operating temperature range of these is used. The non-oxide ceramic is used in the form of powder or in the form of granules obtained by sintering powder and pulverizing it.

Next, the operation of such a sheath thermocouple will be described. Non-oxide ceramic 3 filled in the sheath 1
a has excellent thermal conductivity, electrical insulation, and heat resistance. Therefore, when the temperature is measured using the sheath thermocouple, the temperature upper limit value near the high temperature limit is high and the measurement accuracy is high.

The sheath thermocouple is used in vacuum or in an inert atmosphere. When used in the atmosphere, it must be used at a temperature lower than the heat resistant temperature of the metal forming the sheath 1. When used at a temperature higher than the heat resistant temperature, a sheath thermocouple is housed inside the ceramic protection tube.
In this case, the sheath thermocouple cannot be bent and the flexibility is lost, but the temperature can be measured. For example, if the material of the sheath 1 is W and the material of the strand 2 is WRe, the temperature of 2000 ° C. or higher can be measured.

[0014]

As can be seen from the above description, according to the sheath thermocouple of the present invention, since the non-oxide ceramic is used as the inorganic insulator filling the inside of the microcapillary, it is difficult to react with moisture and it can be used for a long time. When the sheath thermocouple is used and the sheath thermocouple is stored for a long time, the sheath thermocouple does not deteriorate due to insulation. In addition, since it has excellent thermal conductivity, insulation and heat resistance, stable temperature measurement can be performed even at high temperatures.

[Brief description of drawings]

1 is a cross-sectional view of a sheath thermocouple according to the present invention.

FIG. 2 is a sectional view of a conventional sheath thermocouple.

[Explanation of symbols]

 1 ... Sheath 2 ... Strand 3a ... Non-oxide ceramic

Claims (1)

[Claims] 1. A sheath thermocouple in which a wire constituting a thermocouple is accommodated inside a microcapillary tube and an inorganic insulator is filled inside the microcapillary tube, wherein a non-oxide ceramic is used as the inorganic insulator. A sheathed thermocouple.