JPS5826641B2 - Temperature/humidity detection element - Google Patents

Description

[Detailed description of the invention] The present invention provides a temperature/humidity detection element.

In general, a humidity-sensitive resistor is a resistor that is sensitive to humidity and whose resistance value changes depending on the humidity, and is used as a humidity measurement element or a humidity adjustment sensor.

As is well known, Fe2O3, Al2O3 tCr203
Metal oxides such as , Ni2O3, etc. have excellent water absorbing properties, and therefore, moisture-sensitive resistor elements have been manufactured using such properties.

Conventional humidity-sensitive resistors have deteriorated moisture-sensing characteristics due to adhesion of airborne pollutants such as oil components, but if the humidity-sensitive resistor is heated to burn off oil components, the original humidity characteristics can be restored. It is something to return to.

Therefore, if the moisture-sensitive resistor loses its moisture-sensitive characteristics, it can be used semi-permanently by heating and cleaning it.

However, in order to control the temperature of this heated cleaning, the temperature must be detected externally using a thermocouple or a thermistor, which has the disadvantage that the configuration is extremely complicated and expensive.

The present invention provides a temperature/humidity detection element that solves the above problems, and this temperature/humidity detection element has NTC characteristics such that its electrical resistance decreases as the temperature rises in the cleaning temperature range. .

Moreover, it is sensitive to humidity, and its electrical resistance changes.

In addition, in terms of sensitivity and humidity sensitivity characteristics, there is no thermistor characteristic in the atmospheric temperature range where humidity detection is possible, but there is a thermistor characteristic above that temperature.

This characteristic is not found in conventional temperature- and humidity-sensitive characteristics, and moreover, it does not exhibit thermistor characteristics in the ambient temperature range where humidity detection is possible, but exhibits thermistor characteristics above that temperature.

Since it is made of porcelain, it is extremely stable even at high temperatures.

For example, if oil components or the like adhere to the surface, it can be heated and cleaned, thereby restoring its original moisture sensitivity characteristics.

In other words, it is not only possible to control the temperature of heated cleaning, but also to control the humidity.

Next, we will discuss the porcelain composition.

This is ACr204 precept (A is Mg, Fe,
At least one type selected from Ni, Co, Mn, Cu) 1 to 99 moles, and Ti 02 precepts 9
It is characterized by containing 9 to 1 molar ratio.

When electrodes are applied to porcelain having the above-mentioned composition ratio or a component mainly composed of the same, the resistance between the electrodes is determined depending on the humidity.

By selecting the composition, it is possible to obtain an element that exhibits high sensitivity even in a low humidity region.

The humidity-resistance characteristic is approximately linear from low humidity to high humidity.

As for the temperature resistance characteristic, the resistance decreases almost linearly at an ambient temperature above which humidity detection is possible (150° C. or above).

At temperatures above 150°C, it is not affected by relative humidity.

More specifically, the temperature/humidity sensing element according to the present invention is a type of semiconductor, and by selecting its composition, it is possible to create a temperature/humidity sensing element that exhibits temperature- and humidity-sensitive characteristics with considerably low resistance. I can do it.

Moreover, ACr204 components (A is Mg, Fe
, Ni, Co, Mn+, and Cu) is a compound with a spinel type crystal structure, and because it is a two-phase type porcelain of spinel type and Ti02 type, humidity Detection becomes possible.

Its resistance temperature coefficient is small in the normal ambient temperature range,
It exhibits thermistor characteristics at higher temperatures.

This porcelain composition can be easily manufactured using ordinary porcelain manufacturing techniques, and can be easily mass-produced using current manufacturing equipment.

Furthermore, this is a so-called metal oxide high temperature sintered body,
Even if it is left in the atmosphere for a long time, its surface condition does not change.

ACr204 (k is Mg, Fe, Ni,
When the composition ratio of at least one component selected from Co, Mn and Cu and the TiO2 component is less than 1 mole and the latter more than 99 mole, there is almost no change in resistance against humidity changes. , the thermistor characteristics also disappear.

Furthermore, if the former becomes more than 99 molar and the latter becomes less than 1 molar, the effect of adding the Ti02 component becomes less significant (and high sensitivity in a low humidity region cannot be obtained).

Below, regarding specific examples of the ceramic composition according to the present invention, Mg
The Cr2O4-Ti02 system will be explained as a representative example.

First, 99.99% or more of MgO, Cr2O3, and T
iO2 was prepared and mixed in a composition ratio as shown in the table below, and wet-mixed in a pot containing an agate ball.

After drying the mixture, a 3-width polyvinyl alcohol aqueous solution was added at a ratio of 10 cc to 100 g of mixed powder, mixed in a mortar, and granulated.

And 750kg/CI? At a pressure of L, 10mm x 5
．． The bottom mold was made into a rectangular plate shape with dimensions of 5 mm x 0, 25 vtm.

This molded body was held in air at a temperature of 1300° C. for 2 hours and fired.

A paste containing Ru 02 was printed on the porcelain thus obtained in a comb shape using a screen mesh method, and then fired at a temperature of 800° C. to form a pair of electrodes.

Figure 1 shows its configuration. FIG. 1A is a side view, and FIG. 1A is a perspective view.

In FIG. 1, comb-shaped electrodes 3 were provided on sample surfaces 1 and 2, and conductive electrodes (Ru0z type) were provided on the side surfaces.

The conduction electrode is an electrode for electrically connecting a comb-shaped electrode baked on one side and a comb-shaped electrode baked on the other side in parallel.

4 is a lead wire for taking out an electrode terminal. Next, the relative humidity-resistance characteristics of Samples 1 to 6 thus obtained were investigated by varying the relative humidity of the measurement atmosphere and measuring the resistance between the electrodes of each sample.

In the latter case, the resistance between the electrodes was measured while varying the ambient temperature.

The results are shown in Figures 2a and b, respectively.

The symbols attached to the figures correspond to the sample numbers.

As is clear from the figure, TiO to MgCr2O4
As the amount of 2 increases, the overall resistance decreases and the sensitivity in the low humidity region increases, and at the same time, the temperature-resistance change rate becomes narrower in the thermistor characteristics, increasing the sensitivity.

And as the amount of Ti 02 increases, the relative humidity-resistance characteristic becomes linear.

Then, the temperature at which the thermistor characteristics deteriorate shifts to the lower temperature side.

Furthermore, it becomes highly sensitive at high humidity, especially at the dew point, and temperature -
Resistance characteristics change linearly.

Beyond that, little sensitivity to changes in humidity and temperature is obtained.

Moreover, since the thermistor characteristics appear within the temperature range where humidity detection is possible, it becomes impossible to detect humidity and temperature.

That is, when the 5KMgCrO,i component was 99% and the Ti02 component was 1% as in Sample 2, an increase in sensitivity and a decrease in resistance were obtained in the low humidity region.

In the thermistor characteristics, the resistance changes linearly, resulting in high sensitivity.

However, it was found that when the TiO2 component was less than 1 mole, the properties were almost the same as those of Sample 1.

It was clearly recognized that when the T i 02 component was 1 molar or higher, the porcelain became two-phase.

When the TiO2 component exceeds 99 moles, the effect of MgCr2O4K cannot be obtained, as is clear from sample 6.
Not practical.

Samples 2 to 5 at room temperature and humidity (temperature 20°C, relative humidity 54%)
The heat cleaning cycle was repeated 105 times.

As a result, it was confirmed that the changes in humidity-resistance and temperature-resistance characteristics were extremely stable, each within a large number.

Moreover, the MgCr204-TiO2 porcelain assembly is 130
It is stable and can withstand temperatures as high as 0°C.

An embodiment constructed using such porcelain is shown in FIG.

This is done by installing a nichrome resistance heating element 5 around the element 8, which is made up of the above-mentioned porcelain with electrodes, and passing a current through it to generate heat, thereby heating the element 8 and removing contaminants attached to it. It is designed so that it can be burned away.

6 is a lead terminal.

Reference numeral 7 denotes a child support stand, which supports the element 8 and the resistance heating element 5.

Then, the cleaning temperature (for example, 450° C.) is controlled to a predetermined value using the thermistor characteristics of this element 8.

Although the Mg Cr204-T i O2 system has been described above, the relative humidity-resistance characteristics and the temperature-resistance characteristics were almost the same for the other systems as well.

As described above, the temperature/humidity detection element according to the present invention has A
Cr2C4 component (A is Mg, Fe, Ni
.

A small amount selected from Co, Mn and Cu (both 1
Electrodes are provided on porcelain made of 1 to 99 moles of TiO2 and 1 mole of 9 components of TiO2, and at least a cleaning heating element is provided to heat the porcelain.

This temperature/humidity detection element exhibits high sensitivity in the relative humidity range of 0 to 100.

In addition, since it exhibits linear thermistor characteristics in a high temperature region, when contaminants are removed by a cleaning heating element, the thermistor characteristics can be used to control the current to the heating element, ensuring that the contaminants are removed repeatedly. By removing the humidity at a very low temperature, humidity can be detected for an extremely long period of time.

Products made of this porcelain material can be used at high temperatures, and exhibit very little characteristic deterioration even when used at high temperatures and high humidity.

Therefore, it is useful in the fields of food processing and cooking, humidity sensor air conditioning systems, and the like.

In the present invention, it is also possible to further introduce other components to improve properties.

For example, SiO2, Al2O3, V2O3, Bi2O
3 etc. can be added as a mineralizer to improve sinterability.

[Brief explanation of drawings]

FIGS. 1a and 1b are a side view and a perspective view of an element used in one embodiment of the present invention, and FIG. 2a is a diagram, respectively. b is its characteristic curve diagram, and FIG. 3 is a perspective view of this embodiment. 1.2...Sample surface, 3...Comb-shaped electrode, 4...Lead wire, 5...Heating element, 6
...Lead terminal, 7...Block stand, 8.
...Temperature/humidity detection element.

Claims (1)

[Claims] I ACr20J2: min (A is Mg, Fe
, Ni, C. At least one species selected from Mn and Cu)1
It is characterized by having an electrode containing 99 moles of TiO2 components and 9 moles of TiO2 components, and a cleaning heating element for heating the sintered body and removing contaminants adhering to the surface of the sintered body. Temperature/humidity detection element.