JPS5826802B2 - Temperature sensing element for high temperature - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an unnecessary high-temperature sensing element such as an amplifier, which is used under severe conditions at temperatures above about 300°C, particularly above 800°C.

Conventionally, temperature sensing elements for use in exhaust gas purification catalysts for automobiles have been known as such temperature sensing elements, and their stability as temperature sensing materials has been evaluated to a certain extent.

However, the cost of the device is high, the conductive wires and their joints are prone to breakage due to the structure, the electrodes embedded in the sintered ceramic, which is a temperature-sensitive material, are often damaged, and the platinum electrodes used for the electrodes are expensive. However, there were some shortcomings, and improvements were desired.

The present invention provides a high-temperature sensing element that has been improved from such drawbacks, and is not limited to use in automobiles as described above, but can be widely applied in general.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

Basically, as shown in FIG. 1, the high-temperature sensing element according to the present invention includes at least two heat-resistant conductive wires, a heat-resistant metal body 11 that also serves as a grounding part between the electrode part and the temperature-sensitive material. It is constructed by embedding it in the physical insulator 12 and simultaneously connecting it in the → body direction, and thermally spraying the temperature-sensitive material 13 on the exposed part of one end.

As the heat-resistant metal body 11, for example, a heat-resistant alloy such as Hastelloy, Nichrome, or Kanthal, or an expensive metal body coated with platinum can be used.

As the heat-resistant oxide insulator 12, alumina, magnesia, mullite, etc. are used, and as the temperature-sensitive material, conventionally known materials such as spinel oxide, provskite oxide, zirconia oxide, etc. are used. do.

Even if the temperature-sensitive material has a resistance of 1010 Ωα or more at room temperature, i o
At a temperature of about 00° C., the resistance decreases to as low as 1 Ωα, so if the resistance is sufficiently higher than this, the heat-resistant oxide insulator can withstand use even if it does not have a particularly high resistance.

Moreover, since only one end of the temperature-sensitive material is thermally sprayed, it is expected that the somewhat lower resistance at low temperatures will be less of a problem.

The temperature-sensitive element according to the present invention has been found to have high reliability and long life, as evidenced by its integrated structure.

The failure observed in the temperature-sensitive element according to the present invention was in the grounding part of the temperature-sensitive material, but it was much smaller than the damage in the electrode part embedded in the conventional ceramic, and other defects were eliminated.

Furthermore, in the conventional example, there was a problem with the strength of the buried electrode, the yield was low, and there were many steps to assemble it into a high-temperature element, making it expensive. However, according to the present invention, the yield is almost negligible when bonding the grounding part of the temperature-sensitive material. 100%, and the process is simple and short, making it possible to significantly reduce costs.

FIG. 2 shows another embodiment of the temperature-sensitive element according to the invention.

In this structure, the temperature-sensitive material 23 is embedded in a heat-resistant oxide insulating body so as to be grounded to the two heat-resistant metal bodies 21 .

Also, although the thermal response is somewhat degraded, it is useful to provide a protective film 34 to protect the temperature-sensitive material from the harsh atmosphere, as shown in FIG.

This is especially necessary for materials that exhibit oxygen partial pressure dependence, such as zirconia-based materials.

FIG. 4 shows yet another embodiment of the temperature sensing element according to the present invention.

A heat-resistant metal body 41 constituting a conductive portion is passed through the holes of a heat-resistant oxide insulator 42 having at least two holes, and an electrode 45 is provided at one end of the heat-resistant metal body 41 and fixed to the insulator 42 .

The other end is thermally sprayed with a temperature-sensitive material, and the heat-resistant metal body 41 is grounded and fixed.

Furthermore, a protective film 44 is provided as necessary.

These modified structures have the same excellent characteristics as the high temperature elements of the basic structure shown in FIG.

Next, non-limiting examples of the present invention will be described.

Example 1 A nichrome wire with a diameter of 1.5 titφ and a length of 60 m was roughened by sandblasting with 200 meshes of fine alumina particles, and then alumina powder having an average size of 30 μm was plasma sprayed.

Ar N2 mixed gas was used as the plasma, the plasma current was set to 80OA, and the two nichrome wires were placed at a spraying distance of 70n, with the center axis of the two nichrome wires forming an elliptical cylinder with a diameter of 6. It was rotated around the center and sprayed for several minutes.

A temperature-sensitive material was plasma-sprayed to a thickness of about 250 μm onto the exposed end of the nichrome wire (13 mm), and an alumina film about 1 inch thick was further formed as a protective film.

Spinel type material A12038.6Mo#%, Mgo 5
0.7 mol%, Cr20327.1 mol%, Fe20
313.6 mole/l/%) and a Zr102-based material (a material containing 9 mole percent of Y2O2) were used.

After annealing at 800° C. for 2 hours to eliminate stress during thermal spraying, the material was cooled in a furnace and its properties were investigated.

The B constant of these elements is 1000 between 850 and 950°C.
0° or more, 1050°C in automobile exhaust gas, 60°
Changes in B constant and resistance after 0 hours of heat resistance test are ±3
% or less.

Furthermore, even after 100,000 cycles of seismic and heat resistance tests in which 10G was applied, almost no changes in characteristics were observed.

In seismic tests of conventional products, about 50% of them were damaged due to the structure of the joints, such as conductive parts and grounding parts, being susceptible to stress.

Example 2 An alumina pipe with a diameter of 1.5 ms and a length of 65 mm is placed in an alumina pipe with a diameter of 501 t and a diameter of 6 nm having two holes with a diameter of 1.6 m.
A Kanthal wire of mm was inserted, one end was fixed with alumina cement as an electrode part, and a temperature-sensitive material was sprayed on the other end.

The temperature-sensitive material is the same as in Example 1. At this time, the sprayed surface was somewhat roughened as in Example 1, and the tip of the Kanthal wire was plated with platinum.

Furthermore, alumina was thermally sprayed as a protective film to produce an element as shown in FIG.

When the same test as in Example 1 was conducted, almost the same characteristics were shown, and the reliability was similarly high.

Such high reliability, especially the improvement in the bonding strength of the terminals, is thought to be due to the fact that the physical bonding strength (fitting strength) due to thermal spraying has a synergistic effect with the chemical bonding force.

In addition, as in this example, there is a hole in the terminal portion, and it can be seen that the thermally sprayed material has penetrated into the hole, which is presumed to further improve the bonding strength.

In other words, the high-temperature sensing element integrated by thermal spraying has excellent stability and strong resistance to mechanical stress and thermal stress.
It is an excellent element with a simple structure and no problems with terminals as in conventional products.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the basic structure of a high-temperature sensing element according to the present invention, and FIGS. 2 to 4 are perspective views and sectional views of different embodiments showing modifications thereof. 11.21,41...Heat-resistant metal body, 12,22
゜42...Heat-resistant oxide insulator, 13,23,4
3...Temperature-sensitive material, 44...Protective film,
45... Electrode.

Claims (1)

[Scope of Claims] 1. The parts of at least two heat-resistant metal bodies excluding at least the electrode part and the grounding part of the temperature-sensitive material are sealed and integrated with a heat-resistant oxide insulator, and the grounding part is sensed to short-circuit. A high-temperature sensing element made by thermally spraying a hot material. 2. The high-temperature sensing element according to claim 1, wherein the temperature-sensitive material is protected by an insulating film sprayed thereon. 3. Insert a heat-resistant conductive wire into at least two holes provided in the insulating pine, connect an electrode terminal to one end of the heat-resistant conductive wire and fix it to the insulated pipe, and short-circuit the other end with a temperature-sensitive material. A high-temperature temperature sensing element formed by thermally spraying and adhering to the insulating pipe. 4. The high-temperature sensing element according to claim 3, wherein the temperature-sensitive material is protected by an insulating film sprayed thereon.