JP3014093U - Temperature sensor with thermocouple and protective tube integrated - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a structure of a temperature measuring sensor in which a thermocouple, an insulating tube, and a protective tube are integrated in a thermoelectric thermometer. [Constitution] In the conventional temperature measuring sensor consisting of a protective tube, an insulating tube and a thermocouple, which are separately manufactured, it is necessary to handle with care such as contamination of a bare thermocouple when assembling. The gap between them is likely to cause the inclusion of contaminants when measured at high temperature for a long time, and it is difficult to manufacture a small size and long size. In the present invention, the metal protective tube in the sheath thermocouple and the member corresponding to the insulating powder are the two-hole insulating ceramic protective tube. Therefore, it is possible to measure the temperature in a high temperature range, which is impossible with the conventional sheath thermocouple. [Effect] Since the deterioration of the thermocouple wire is small, it has a long service life, is easy to handle, and has good responsiveness. Especially, it is effective for high temperature measurement in a contaminated environment.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a structure of a temperature measuring sensor in which a thermocouple and a protection tube are integrated, and more specifically, a thermocouple is incorporated in a protection tube which has two holes and serves as an insulating tube. The present invention relates to the structure of a temperature measuring sensor integrated into one.

[0002]

[Prior art]

 Generally, the temperature sensor of a thermocouple is a thermocouple that detects temperature by the difference in thermoelectromotive force and an insulator that electrically insulates the wires of the thermocouple, and if necessary, accommodates them and protects them from the outside. It consists of a protective tube. Thermocouples include coated thermocouples that have been previously insulated with Teflon or glass braid, but these are generally limited to temperature measurements in the low temperature region of 500 ° C or less, and temperature measurements in the high temperature region are generally naked thermocouples. The pair is passed through a two-hole magnetic insulating tube, which is inserted into the above-mentioned protective tube. The material of thermocouple is divided into noble metal type using platinum or rhodium and base metal type using other metal or alloy. However, base metal type is inferior in heat resistance, so it is mainly used for high temperature measurement of 1000 ℃ or more. A precious metal thermocouple is used for. When this noble metal thermocouple is exposed to the environment of reducing gas, metallic gas and impurities, the thermoelectromotive force is lowered and the temperature error becomes large. For example, if CO gas is present when the platinum wire is in contact with a refractory containing silica at a high temperature, silica may be reduced and platinum may absorb silicon to form a very brittle alloy, resulting in a wire breakage. In addition, alloys or compounds with low melting points are made with most metals such as copper, iron, lead, zinc, cadmium, aluminum, tin, etc., and in all cases, the thermoelectromotive force decreases and temperature accuracy deteriorates, and melting due to lowering of melting point It becomes impossible to measure temperature due to brittle cracks. Protective tubes are used to protect the thermocouple and prevent deterioration from impurities such as these being attached or being exposed to polluted gas, but during temperature measurement, especially high temperature measurement is performed in a severe polluted environment. In many cases, contaminants enter the small gap between the protective tube and the insulating tube, and often invade the heat-sensitive part of the thermocouple and the joint part of the insulating tube. In the case of continuous temperature measurement of molten steel, a corrosion-resistant protective tube is used outside the above-mentioned protective tube for protecting the thermocouple. This is a highly corrosion-resistant non-oxide such as BN and ALN. It is made of ceramics, carbon-containing refractory materials such as Mo and Zr-based cermets, and alumina graphite. They generate reducing gas, metal vapor, glass, etc. at high temperatures, respectively, and create the polluted environment as described above. At the level of molten steel temperature measurement from 1500 ℃ to 1600 ℃, the protective tube that protects the thermocouple often breaks due to various factors such as deterioration of material strength, deformation, thermal shock, and difference in expansion between members. Thermocouples will be directly exposed to the polluted environment. From this point as well, the conventional method has many problems in continuous temperature measurement such as molten steel, and is not widely used except for spot temperature measurement.

Next, during handling, contamination of the inside of the thermocouple, the insulating tube and the protective tube during storage or assembly also leads to deterioration of the thermocouple at high temperatures. Therefore, inserting thermocouples into insulating tubes is done in a clean room with gloves that are not touched by hand and with great care. Furthermore, this insertion work does not require time and effort if the wire is not used, but it often causes deformation distortion and surface roughness when used once. It is a very difficult and catastrophic task to pass through.

From the viewpoint of performance as a thermometer, it is important that the temperature response is excellent in addition to the temperature accuracy. There is a protective tube, a gap, and an insulating tube between the temperature measurement target and the thermosensitive part of the thermocouple, through which heat is transferred, but in the case of a size, there is a thin wall with a small diameter and a small diameter tube. However, the response speed will be correspondingly faster. However, conventional temperature sensors have not been made to be very thin. The outer diameter of the thinnest insulating tube with two holes is about 3 mm, and even if the thickness of the protective tube is 1 mm and the gap is 0.5 mm, the outer diameter of the protective tube (outer diameter of the temperature sensor) is 6 mm. Become. The one with one hole has an outer diameter of up to φ1 mm, so if you cannot put one of the thermocouple wires in this and the other cannot, you can make a temperature sensor with an outer diameter of φ3 mm, but it is weak in strength. In high temperature long time measurement, the deterioration of thermocouple wire is significantly faster than that with two wires, and the long wire is difficult to manufacture and the manufacturing cost is high.

A sheath thermocouple is one in which a thermocouple, an insulator, and a protective tube are integrally structured. This is because magnesium oxide powder is mainly used as the insulator, and heat-resistant metal such as stainless steel or Inconel is used for the outer sheath (sheath) corresponding to the protective tube, which enables bending and stretching. Therefore, since the risk of breakage is low and the airtightness is good, there is no contamination from the outside and the handling is simple. The size is small and the length is very long, and the price is low. However, the operating temperature is up to about 1000 ° C, and long-time measurement on the high temperature side may cause thermocouple contamination by the outer metal.

As described above, the conventional temperature measuring sensor has no problem in the low temperature range, but in the high temperature range of 1000 ° C. or higher, the thermocouple is deteriorated mainly by pollutants, and the handling is troublesome. Causes are also likely to occur. From the viewpoint of performance and size, thinner and longer products are required. These are only possible with a thermocouple, an insulator, and a protective tube as a unit, like a sheath thermocouple, and there is a demand for an integrated temperature sensor for high temperatures at a use temperature of 1000 ° C or higher. In other words, there is a demand for a sheath thermocouple with a ceramic jacket.

[0007]

[Problems to be solved by the device]

 The present invention has been made in view of the above problems, and its purpose is to provide a temperature measuring sensor having a new structure that is easy to handle, has excellent temperature responsiveness, and can prevent deterioration due to atmospheric gas. Is.

[0008]

[Means for Solving the Problems]

 The present inventor has found that the above problems can be solved by the following means. That is,

1. An insulating ceramic protective tube having two holes and two dissimilar metal wires extending in each of the two holes and joined at the tip to form a temperature measuring contact. This can be solved by a temperature measuring sensor in which the thermocouple and the protective tube are integrated, which is composed of a thermocouple and has a structure in which the temperature measuring contact side of the insulating ceramic protective tube is closed. 2. This can be solved by the temperature measuring sensor described in the above 1, characterized in that a gap is provided between the thermocouple and the ceramic body in the temperature measuring contact portion.

[0010]

[Action]

 The structure and operation of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of a temperature measuring sensor having a structure in which a temperature measuring contact is embedded in a ceramics body, in which a thermocouple and a protective tube are integrated. The two thermocouple wires 2 extend through the two holes, and the thermocouple temperature-measuring contact 3 is confined in the body on the side where one end of the two-hole protective tube 1 is sealed, Protected from pollutants and reducing atmosphere. There are many ways to incorporate a thermocouple into a ceramic body, but any method that provides sufficient confidentiality can be used. Depending on this method, there is a method in which the temperature measuring junction part of the thermocouple is embedded in the base material and has no air gap between the thermocouple and the base material, but each method has advantages and disadvantages. In other words, if there are no voids, it is generally easy to manufacture, and direct heat transfer between the substrate and the temperature-measuring contact provides very excellent responsiveness. It is easily damaged by the difference in thermal expansion. On the other hand, those having voids do not cause damage because the thermocouple can expand and contract separately from the substrate, and are suitable for repeated use at high temperatures.

FIG. 2 and FIG. 3 explain this, and various shapes can be taken by means of forming the voids. That is, FIG. 2 is a cross-sectional view of a temperature measuring sensor in which a thermocouple and a protective tube are integrated, which has a structure in which a gap is provided between the temperature measuring contact and the substrate by a partition cover. This is one in which the gap 4 is formed by partitioning the thermocouple and the green body with a flat lid 5 before the temperature measuring junction of the bare thermocouple wire is embedded in the green body. The portion surrounded by the dotted line in FIG. 2 is the flat lid 5, which is made of a material having the same composition as the ceramic base material, and is integrated with the ceramic base material after the main firing. FIG. 3 is a cross-sectional view of a temperature measuring sensor in which a thermocouple and a protective tube are integrated, which has a structure in which a heat-dissipative coating is used to provide a gap. In this case, a heat-dissipative coating is applied to the temperature-measuring contact portion of the thermocouple wire in advance, and after this is embedded in the ceramic body, the coating part disappears during firing to form the void 4. Providing a gap means that the two holes are connected by the gap, and the thermocouple wire passes through the connecting hole without being fixed to the ceramic body. The larger the gap, the more the temperature measuring junction. Since the position of is likely to deviate from the position of the tip of the protection tube and cause an error in temperature measurement, it is preferable to make it as small as possible. In the case of FIG. 3, since a thin space is formed along the shape of the temperature measuring contact so that the temperature measuring contact can hardly move, there is no fear that the temperature measuring contact is displaced.

As the material of the two-hole protective tube, any ceramic can be used as long as it is a ceramic excellent in insulating property at high temperature without deteriorating the thermocouple. For example, in the case of a platinum-based R thermocouple that is weak in a reducing atmosphere, oxides such as Al ₂ O ₃ and MgO are suitable, and it is also possible to change them appropriately according to the purpose of use.

The position of the temperature measuring contact must be near the tip of the protective tube from the viewpoint of temperature measuring accuracy as described above, but from the viewpoint of responsiveness, the thickness between the temperature measuring contact and the leading edge of the protective tube must be determined. It is better to control as thinly as possible. Although this depends on the material of the ceramic and the purpose of use, it is preferably about 1 to 4 mm, and more than this is not preferable from the viewpoint of thermal shock resistance.

Hereinafter, effects of the present invention will be described with reference to embodiments.

[0016]

【Example】

 The outer diameter φ4 mm, hole diameter φ1 mm, and protective tube length for the structure in which the thermocouple temperature measuring contact is embedded in the substrate (Fig. 1) and the structure with a gap between them (Figs. 2 and 3) A sample (integrated temperature measuring sensor) having a length of 500 mm and incorporating an R type thermocouple was prepared. This was used for the temperature measurement of molten steel in steelmaking tundish, which is currently in practice. That is, this integrated temperature measuring sensor was inserted into an external protection tube (ALN-based protection tube for molten steel) set on the lateral wall of the tundish to continuously measure the temperature of molten steel. The temperature measurement time was set to 8 hours per one time, the same sensor was repeatedly used 10 times (80 hours), and then the thermocouple accuracy was tested by a simple method. This test examines the temperature error with respect to the standard thermocouple at 1200 ° C in the electric furnace, and passes the error within ± 3 ° C (including the error of the electric furnace itself ± 1 ° C).

All of the integrated temperature measuring sensors (four each having the structure shown in FIGS. 1, 2, and 3) used in the above test did not cause damage to the protective tube or breakage of the thermocouple, and the verification result was acceptable. there were.

It should be noted that the actual conditions regarding the service life of the conventional continuous temperature measuring sensor (assembled with a thermocouple, a protective tube, and an insulating tube) actually used in the above-mentioned tundish and the integrated temperature measuring sensor. Table 1 shows the comparison.

[0019]

[Table 1] (Note) ・ The number of samples is 144 conventional temperature sensors and 12 integrated temperature sensors. * If the protective tube is damaged, replace the damaged protective tube with a new one and continue the test until the thermocouple breaks or reaches 10 times (80 hours).

According to Table 1, in the case of the conventional temperature measuring sensor, the protective tube is easily damaged (cracked), and the pollutant gas enters the protective tube to rapidly deteriorate the thermocouple and cause a disconnection. Shows. Even if the protective tube was made small (outer diameter φ6 mm, inner diameter φ4 mm), there was no improvement (breakage time of protective tube; average 2.5 times (20 hours)). On the other hand, in the case of the integrated temperature measuring sensor, there is no problem under the above temperature measuring conditions, stable long-term service life is achieved, and it is also small in terms of responsiveness. It was found that steepness was obtained.

Needless to say, the present invention is not limited to this embodiment. For example, the R thermocouple of this example can be changed to other types of thermocouples, and the external shape can be a round shape, a square shape, or an elliptical shape. It may be rounded or flat.

[0022]

[Effect of device]

 According to the present invention, the following points are superior to the conventional thermocouple, the assembly type temperature sensor of the insulating tube and the protective tube.

1. Since it serves as both an insulating tube and a protective tube, it can measure temperature directly without the need for other protective tubes. 2. Since the outer diameter can be reduced without the need for a protective tube, it has excellent temperature responsiveness. 3. Since it has an integral structure like a sheath thermocouple, there is no risk of thermocouple contamination during assembly. 4. Unlike the sheath thermocouple, there is no exposed part of the thermocouple wire, so the thermocouple deterioration is small and the life is long due to temperature measurement in a contaminated environment. 5. Since it has an integral structure like a sheath thermocouple, it is easy to handle. 6. Since a thin product can be obtained, high-temperature measurement can be performed in places where measurement is difficult.

In a specific example, the difference is large especially in a contaminated environment where molten steel temperature is measured, and the conventional assembly-type temperature measuring sensor suffers from severe deterioration and wear of the expensive precious metal thermocouple, which results in a running cost. Although there are problems in terms of both temperature accuracy, the temperature sensor of the present invention can measure temperature with high accuracy for a long time, so its practical and economical effects are extremely large. In addition, it has a wide range of applications, such as safe operation because it can keep the temperature measuring holes to a minimum when measuring temperature in dangerous places such as pot bottoms and furnace bottoms, which was difficult in the past. That is, it can be said that it is a sheath thermocouple for high temperature.

[Submission date] January 19, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

FIG. 1 is a cross-sectional view of a temperature measuring sensor having a structure in which a temperature measuring contact is embedded in a ceramic body and in which a thermocouple and a protective tube are integrated. The two thermocouple wires 2 extend through the two holes, and the thermocouple temperature measuring contacts 3 are two holes. One end of the protective tube 1 is confined in the body on the sealed side, Protected from pollutants and reducing atmosphere. There are many methods for incorporating the thermocouple into the ceramic body, but any method can be used as long as it can provide sufficient airtightness . Depending on this method, there is a method in which the temperature measuring junction of the thermocouple is embedded in the substrate and there is a space between the thermocouple and the substrate, but there are advantages and disadvantages. In other words, if there are no voids, it is generally easy to manufacture, and a very excellent responsiveness can be obtained by direct heat transfer between the base material and the temperature measuring junction. It is easily damaged by the difference. On the other hand, those with voids do not cause damage because the thermocouple can expand and contract separately from the base material, and are suitable for repeated use many times at high temperatures.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

[0018] Incidentally, conventional continuous temperature measuring sensor actually used in the above tundish (thermocouple protective tube, that has been assembled by an insulating tube.) Circumstances regarding the service of the the integrated temperature measuring sensor Table 1 shows the comparison.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a temperature measuring sensor having a structure in which a temperature measuring contact is embedded in a ceramic body and a thermocouple and a protective tube are integrated.

FIG. 2 is a cross-sectional view of a temperature measuring sensor in which a thermocouple and a protective tube are integrated, which has a structure in which a gap is provided between the temperature measuring contact and the substrate by a partition cover.

FIG. 3 is a cross-sectional view of a temperature measuring sensor in which a thermocouple and a protection tube are integrated, which has a structure in which a heat-dissipative coating is used and a gap is provided.

[Explanation of symbols]

 1 Two-hole protective tube of insulating ceramics base 2 Thermocouple wire 3 Thermocouple temperature measuring junction 4 Gap between thermocouple and insulating ceramics base 5 Partition lid (flat lid)

Claims (2)

[Scope of utility model registration request] 1. A thermoelectric tube comprising an insulating ceramic protective tube having two holes, and two dissimilar metal wires extending in each of the two holes and joined at a tip to form a temperature measuring contact. A temperature measuring sensor comprising a thermocouple and a protective tube, which is composed of a pair and has a structure in which the temperature measuring contact side of the insulating ceramic protective tube is closed. 2. The temperature measuring sensor according to claim 1, wherein in the temperature measuring contact portion, a gap is provided between the thermocouple and the ceramic body.