JPH0287032A - Thermistor for high temperature - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-temperature thermistor made of ceramic.

[Prior Art] Conventionally, as this type of high-temperature thermistor, for example, the one disclosed in Japanese Utility Model Application Laid-Open No. 54-49983 is known. In other words, high-temperature thermistors are made of heat-resistant metals (for example, JI
An ion conductive temperature sensing element made of stabilized zirconia is held in a bottomed protective cylinder made of S standard: 5US310.304) and whose inner wall surface is treated with an oxide film. It is fixed with an inorganic filler and a breathable filler, and the lead wire that takes out the output of the temperature detection element also has an air introduction passage. The temperature is measured by bringing the temperature sensing element into contact with the outside air through the filling material and through the air introduction passage.

[Problems to be Solved by the Invention] However, conventional high-temperature thermistors have the following problems.

■ Since the outside air is introduced to the surface of the temperature detection element through the protective tube, the filling material, and the air introduction passage of the lead wire, it takes a long time for the outside temperature to reach the element, and the response is not very good.

■ It is expensive because it uses 5US310 etc. for the bottomed protection tube and has an oxide film treatment on the inner wall, and also requires complicated processes such as positioning when assembling the lead wire that has an air introduction passage. There were various factors that led to high costs.

■Furthermore, in order to prevent characteristic deterioration due to progress of oxidation during high-temperature measurements, a film-forming treatment is performed, but it is still 95%
At temperatures above 0°C, oxidation progresses and stable output characteristics cannot be obtained.

The present invention was made in order to solve the problems of the above-mentioned conventional technology, and is capable of achieving excellent responsiveness and cost reduction, as well as being capable of stable temperature detection even at high temperatures of 950°C or higher. The purpose is to provide thermistors.

[Means for Solving the Problems] A high-temperature thermistor according to the present invention, which has been made to solve the above-mentioned problems, includes: a temperature detection element made of ceramic; a ceramic member that airtightly surrounds the temperature detection element from outside air; The ceramic member is characterized in that the ceramic member has a gap that allows oxygen gas to come into contact with the temperature detection element.

Here, it is preferable that the temperature detection element is an ionic conductive fully stabilized solid electrolyte from the viewpoint of high temperature characteristics;
For example, Zr02-Y2O2, ZrOZr02-Ca0
5ZrO2-, Th02-LaO (lanthanum genus), etc. can be applied.

The ceramic member is a dense insulator with oxidation resistance and high temperature resistance, such as Al2203, mullite,
Spinel etc. can be used.

It is desirable from the manufacturing point of view that the temperature sensing element and the ceramic member be laminated using a thick film printing method. However, in this structure, the method of forming voids containing oxygen gas within the ceramic member includes, for example, From here, a window can be formed in the spacer sandwiched between the amphoteric substrates, and this can be formed as an airtight space using a ceramic member.

[The temperature sensing element surrounded by the active co-ceramic member is in contact with and exits the void filled with oxygen gas. The oxygen gas in this gap acts as an ion conductor for the temperature detection element, and as a result, the temperature detection element outputs an electrical signal that depends on the outside temperature.

In addition, since the ceramic member surrounds the temperature detection element and makes it airtight from the outside air, it is possible to prevent the deterioration of high temperature characteristics due to oxidation of the heat-resistant metal on the protective cylinder wall surface as in the conventional case. It also prevents deterioration that occurs due to the influence of outside air.

Furthermore, high-temperature thermistors do not have a structure in which the outside temperature is conducted to the temperature detection element through a protective tube or filler made of heat-resistant metal, but the outside temperature is transmitted to the temperature detection element through a ceramic member. Since the temperature is measured based on the output of this temperature detection element, responsiveness is excellent.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an exploded perspective view of a high temperature thermistor S according to the first embodiment, and FIG. 2 is a partially assembled view of the same.

In these figures, 1 and 2 are substrates as ceramic members (thickness 0.5 mm, width 4.5 mm, length 6 mm).
0 mm), 3 is a spacer (
7 is a temperature detection element (thickness 20 to 50 mm).
gm, width 5 nuu, length 5-10...■), 8 and 9
10 is a porous electrode, 10 is an intervening particle placed on or around the temperature detection element 7, and 12 and 13 are porous electrodes 8.
This is a platinum lead wire connected to the end 8a59a of 9.

These parts are laminated and fired,
The high-temperature thermistor shown in FIG. 3 has been completed. Next, the composition and manufacturing method of each member will be explained in detail.

First, a green sheet that will become the substrate 1.2 is manufactured. The green sheet has a specific surface area of 6 to 10 vn'/g and an average particle size of 0. 81Lm of alumina powder, SiO2・C
It is manufactured by adding 2% by weight of aO--MgO-based lath, kneading the mixture with a known PVB binder, and forming it into a sheet using the dokuder blade method.

Next, porous electrodes 8.9 are formed by printing PT paste on this green sheet.

As a pt paste, the specific surface area is 3 tn'/g,
Using Pt￥93 powder with a density of 5 to 6 g/m3 per unit volume, it contains 16% by weight of ZrO2Y2O3 solid electrolyte as a common base material, and is kneaded with a cellulose binder (organic solvent) to form a paste. Use the converted one.

Next, the temperature detection element 7 is laminated by printing between the porous electrodes 8 and 9 on the green sheet. The temperature detection element 7 uses powder of a completely stabilized solid electrolyte of Zr() + 8 to 15 mol% Y2O3, and the average particle size of this powder is 3Bm.
The specific surface area is adjusted to 2 to 5 tn'/g, and this is made into a paste with a cellulose binder.

Subsequently, a spacer 3 having an element notch 4 and an electrode notch 5,6 is laminated on the green sheet. Spacer 3 is manufactured from A12203 paste.

Next, the intervening particles 10 made of AQ203 are transferred to the temperature detection element 7.
and print on the green sheet around it. This is because the green sheet and the like do not come into close contact with the element 7 during firing, thereby forming an inner chamber (void). The intervening particles 10 are prepared to have a specific surface area of 27 TI2/g and an average particle size of 4 Bm, and are used after being made into a paste with a cellulose binder.

Next, the ends 8a and 9a of the porous electrode 8.9 have a diameter of 0°25m.
m of platinum lead wires are bonded, and then the other substrate 2 (of the same material and shape as the substrate 1 (green sheet)) is bonded.
Crimp the green sheet).

Next, after cutting this, the resin is removed by heating.

Thereafter, an acing process is performed in which the process of firing in an atmosphere of 1520° C. to 1530° C. for 1 hour and further applying a voltage of 1.5 V for 60 seconds in an atmosphere of 680° C. is repeated 5 times.

As a result, the substrate 1.2 and the spacer 3 have a close contact structure after firing, and a high-temperature thermistor S is constructed in which the upper space in contact with the temperature detection element 7 is an inner chamber cut off from the outside air.

To explain the operation of the high temperature thermistor S, when a voltage is applied between the lead wires 12 and 13, oxygen gas in the inner chamber acts as an ion conductor via the temperature detection element 7, and the temperature detection element 7 changes to the temperature. It shows a dependent resistance value, which is output as an electrical signal between the leads 12 and 13. Based on this electrical signal, the temperature of the external atmosphere can be measured.

To glue the high-temperature thermistor S, as shown in FIG. is welded or brazed and fixed to the tapered metal fitting 23 with a heat-resistant fixing material (cement glass) 24 interposed therebetween.

At this time, the tip S1 of the high temperature thermistor S is exposed. Note that the high temperature thermistor S may be fixed to a metal fitting 23A having a flange 25 welded or brazed as shown in FIG. 5.

In this way, according to this embodiment, the temperature sensing element S itself can be exposed and assembled without covering the temperature sensing element with a metal protection tube as in conventional high temperature thermistors, which simplifies the structure. Moreover, it is not necessary to use expensive parts such as a metal protection tube, so it is possible to reduce costs.

Next, the following experiment was conducted to investigate the characteristics of the above example.

First, the resistance value at a temperature detection element temperature of 700°C to 1000°C was measured. The graph in FIG. 6 shows this example,
FIG. 7 shows a comparative example corresponding to the conventional technique. As is clear from these figures, in the comparative example, the resistance value varied and was unusable at temperatures of 950°C or higher, but according to the example, stable resistance-temperature characteristics were obtained up to 1000°C or higher. , it was found that it can be used at higher temperatures than conventional methods.

Next, the response when the high temperature thermistor was placed in an electric furnace at 1000°C was investigated. As a result, as shown in Fig. 8, the time it took to reach 1000°C was about 60 seconds in the comparative example (solid line), while it was as short as 40 seconds in the present example (broken line), and 30 seconds. The response has improved by 40% since then.

Therefore, this improved response can of course be applied to overheat warning devices for automobile exhaust gas purification catalysts, as well as exhaust gas recirculation devices, etc., which conventionally required oven loop control due to poor response. Feedback control has become possible for engine control.

In the first embodiment, the porous electrodes are formed on both sides of the temperature detection element, but the present invention is not limited to this, and as shown in FIG. Similar effects can be achieved with the configuration of the second embodiment. Regarding the second embodiment, only the differences from the first embodiment will be described. The porous electrode 31 is formed by printing a thick film of PT paste on a ceramic substrate (not shown). Next, after laminating the temperature sensing element 7 by thick film printing, a porous electrode 30 is formed by printing a thick film of PT paste thereon. Furthermore, on top of this ceramic substrate (
(not shown) is crimped, and the high temperature thermistor is manufactured through the same steps as in the first embodiment. In this case, intervening particles are not particularly necessary because a gap is established on the sides of the temperature detection element 70. Therefore, the gap can function as the sensor if it is not only formed as an inner chamber as in the first embodiment, but also has enough oxygen gas to bring about the oxygen conduction effect of the temperature detection element 7ζ. .

[Effects of the Invention] As explained above, according to the present invention, since the temperature detection element made of ceramic is surrounded airtight from the outside air by the ceramic member, a stable resistance temperature can be achieved regardless of the surrounding atmosphere. Specificity is obtained.

Further, since there is no need to introduce outside air to the temperature detection element, high responsiveness can be obtained, and therefore it can be applied to an overheat warning device for an automobile exhaust gas purification catalyst and engine control.

Furthermore, since the temperature detection element is surrounded by a ceramic member, it is durable, and unlike conventional protection tubes, corrosion resistance and heat resistance are not particularly problematic. Moreover,
Another advantage is that assembly and structure are simplified.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing a high temperature thermistor according to an embodiment of the present invention, FIG. 2 is a perspective view of the high temperature thermistor shown in FIG. A perspective view showing the thermistor, Fig. 4 is a sectional view showing the high temperature thermistor attached to a metal fitting, Fig. 5 is a sectional view showing another embodiment of Fig. 4, and Fig. 6 is the resistor of this embodiment. - A graph showing the temperature characteristics, Fig. 7 is a graph showing the resistance-temperature characteristics of a conventional thermistor, Fig. 8 is a graph showing the responsiveness to temperature, and Fig. 9 shows the surroundings of the temperature detection element of another example. FIG. S... High temperature thermistor 1.2... Board 3...
・Spacer 7...Temperature detection element 8.9...Porous electrode 10...Intervening particles 12.13...Lead wire Figure 1 Agent: Patent attorney Tsutomu Sadachi (and 2 others) Figure 4 Figure 9Figure 5

Claims (1)

[Scope of Claims] A temperature sensing element made of ceramic, and a ceramic member that airtightly surrounds the temperature sensing element with respect to outside air, and a gap is provided in the ceramic member to allow oxygen gas to come into contact with the temperature sensing element. A high temperature thermistor comprising: