JPH0650935A - Electrochemical gas sensor - Google Patents

Abstract

PURPOSE:To obtain an electrochemical gas sensor, which reports the sensitivity for gas to be detected by detecting the dehydrated state of a solid electrolyte film. CONSTITUTION:An electrode group 5 includes an insulating substrate 1 and a working electrode 2 and a counter electrode 3, which are provided on the insulating substrate 1. A solid electrolyte film 6 covers the series of the electrode group 5; When water is infiltrated, the film 6 becomes the electrolyte. A detecting element 7 comprising the electrode group 5 and the solid electrolyte film 6 detects gas to be detected. An output circuit 10 of the detecting element 7, a humidity detecting element 8 provided on the insulating substrate 1 and an output circuit 9 of the humidity detecting element 8 are further provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochemical gas sensor, and more particularly, to an electric circuit provided with an insulating substrate provided with an electrode group including a working electrode and a counter electrode, and a solid electrolyte membrane covering the electrode group in series. The present invention relates to a chemical gas sensor that detects, for example, carbon monoxide gas contained in an atmosphere as a test gas by utilizing an electrochemical reaction of gas occurring on a working electrode and a counter electrode.

[0002]

2. Description of the Related Art As disclosed in, for example, JP-A-53-115293 or JP-A-64-88354, a plurality of electrodes are formed on an insulating substrate, and when these electrodes contain water, an electrolyte is formed. Connected with a solid electrolyte membrane
A gas sensor using an electrochemical reaction has the function of detecting the test gas in the atmosphere by causing the test gas to undergo an electrochemical reaction at the electrode.The detection sensitivity of this type of gas sensor is the humidity of the atmosphere. There is a problem in that it largely depends on. That is, when the humidity of the atmosphere rises, the water content of the solid electrolyte membrane increases, the electrolyte of the solid electrolyte membrane is strongly maintained, and when the test gas reaches the working electrode through the solid electrolyte membrane, the counter electrode An electric current flows between
As a result, it is sensitive to the test gas. However, if the humidity of the atmosphere decreases, the water content of the solid electrolyte membrane decreases,
When the electrolyte of the solid electrolyte membrane weakens, even if the test gas permeates this solid electrolyte membrane and reaches the working electrode, no current flows between it and the counter electrode, and as a result, the test gas is insensitive. , Reliance of false alarm or detection is lost.

[0003]

SUMMARY OF THE INVENTION Therefore, the problem to be solved by the present invention is to detect a dehydrated state in which a solid electrolyte membrane is a non-electrolyte and to notify the presence or absence of sensitivity to a test gas, which is highly reliable. A chemical gas sensor is provided.

[0004]

SUMMARY OF THE INVENTION An electrochemical gas sensor according to the present invention comprises an insulating substrate 1, a working electrode 2 provided on the insulating substrate 1, an electrode group 5 including a counter electrode 3, and a group of these electrodes 5. A detection element 7 for detecting a test gas, which is composed of a solid electrolyte membrane 6 which becomes an electrolyte when it contains water.
An output circuit 10 of the detection element 7, a humidity detection element 8 provided on the insulating substrate 1, and an output circuit 9 which outputs an output signal based on an input signal from the humidity detection element 8 when the humidity is lower than a certain level. It is characterized by having.

[0005]

According to the electrochemical gas sensor of the present invention, the electrode group 5 including the working electrode 2 and the counter electrode 3 provided on the insulating substrate 1, and the solid electrolyte membrane 6 that covers the electrode group 5 in series.
The test gas which has reached the working electrode 2 of the detection element 7 for detecting the test gas consisting of and causes an electrochemical reaction in the working electrode 2, and as a result, a solid electrolyte membrane is formed between the working electrode 2 and the counter electrode 3. A current corresponding to the amount of the test gas flows through 6.
In this case, the humidity detecting element 8 detects the humidity of the atmosphere having a deep correlation with the electrolyte of the solid electrolyte membrane 6 which depends on the water content of the solid electrolyte membrane 6 covering the electrode group 5 formed on the insulating substrate 1. Then, the presence / absence of sensitivity to the test gas is notified by the output circuit 9 using this detection output as an input signal.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings shown as embodiments.

FIG. 1 is a circuit diagram of an electrochemical gas sensor according to the present invention, FIG. 2 is a sectional view taken along line AA of FIG. 1, FIG. 3 is a sectional view taken along line BB of FIG. 1, and FIG. It is sectional drawing which shows the usage example of the electrochemical gas sensor which concerns on an Example.

The electrochemical gas sensor according to the present invention has an insulating substrate 1 as shown in FIGS. 1, 2 and 3. As the insulating substrate 1, for example, a ceramic substrate such as alumina or aluminum nitride or a resin substrate such as phenol resin or epoxy resin is used. The insulating substrate 1 is provided with a working electrode 2, a counter electrode 3 facing the working electrode 2, and an electrode group 5 including a reference electrode 4 facing the electrodes if necessary. The reference electrode 4 functions as a reference potential of the working electrode 2. The working electrode 2 and the counter electrode 3 are, for example, platinum that promotes the electrode reaction of the test gas, and the reference electrode 4 is, for example, gold that is stable against the test gas. The above-mentioned electrode group 5 is coated with a solid electrolyte membrane 6 in series to form a detection element 7 for detecting a test gas. As the solid electrolyte membrane 6, a polymer having a high polarity such as polystyrene sulfonate, polyvinyl sulfonate, perfluorosulfonate polymer (trademark Nafion manufactured by DuPont), and perfluorocarboxylate polymer is used, and these polymers are in a water-containing state. To provide an electrolyte membrane that produces ionic conductivity when held at. The test gas that has passed through the solid electrolyte membrane 6 of the detection element 7 and reached the working electrode 2 causes an electrochemical reaction in the working electrode 2 to which a voltage is applied between the counter electrode 3 and the reaction gas. A current determined by the ions flows through the solid electrolyte membrane 6 to the counter electrode 3. An output circuit 10 to which the output current of the detection element 7 is input is connected to the detection element 7.

The electrochemical gas sensor according to the present invention further has a humidity detecting element 8. The humidity detecting element 8 is provided on the insulating substrate 1 and exists in the same atmosphere as the detecting element 7 for the test gas. Therefore, the humidity of the atmosphere detected by the humidity detection element 8 is determined by the detection element 7 of the test gas.
The humidity of the atmosphere is the same. That is, the humidity detecting element 8 electrically changes the humidity of the atmosphere, which has a deep correlation with the electrolyte of the solid electrolyte membrane 6 depending on the water content of the solid electrolyte membrane 6 covering the electrode group 5 formed on the insulating substrate 1. The presence or absence of sensitivity to the test gas is notified by the output circuit 9 which detects the signal and uses this detection output as an input signal. As the humidity detecting element 8, for example, a pair of electrodes 8a and 8b are connected by a semiconductor 8c, and a humidity detecting element using a property that the resistance changes as the humidity of the semiconductor 8c rises and falls is used. The humidity detecting element 8 detects and outputs a correlative electrical characteristic as a signal, and the humidity detecting element 8 is connected to an output circuit 9 for processing an output current of the humidity detecting element 8 by a signal line 9a.

The electrochemical gas sensor described in detail is used by being built in the housing 11 as shown in FIG.
The housing 11 has a partition wall 14 which divides the water storage tank 12 and a humidity control space 13 having a vent hole 16 into two parts.
Reference numeral 4 is formed of an insulating substrate 1 of an electrochemical gas sensor built in a housing 11, and further, water vapor from a water storage tank 12 is introduced into a humidity control space 13 to increase the humidity of the solid electrolyte membrane 6 in the humidity control space 13. In order to regulate the humidity, a humidity control hole 15 is formed in the partition wall 14 between the detection gas detection element 7 and the humidity detection element 8.

[0011]

According to the electrochemical gas sensor of the present invention, the humidity detecting element 8 has the solid electrolyte membrane 6 which depends on the water content of the solid electrolyte membrane 6 covering the electrode group 5 formed on the insulating substrate 1. The humidity of the atmosphere having a deep correlation with the electrolyte is detected, and the output circuit 9 using this detection output as an input signal notifies the presence or absence of the sensitization to the gas to be detected, so that the solid electrolyte membrane 6 is dehydrated or drained. High reliability with no loss of information.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an electrochemical gas sensor according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG.

FIG. 4 is a cross-sectional view showing a usage example of the electrochemical gas sensor according to the embodiment of the present invention.

[Explanation of symbols]

 1 Insulating Substrate 2 Working Electrode 3 Counter Electrode 4 Reference Electrode 5 Electrode Group 6 Solid Electrolyte Membrane 7 Sensing Element 8 Temperature Sensing Element 9 Output Circuit 10 Output Circuit

Claims (1)

[Claims] 1. An insulating substrate 1, an electrode group 5 including a working electrode 2 and a counter electrode 3 provided on the insulating substrate 1, and a solid electrolyte membrane 6 which covers the electrode group 5 in series and becomes an electrolyte when it contains water. And a detection element 7 for detecting a test gas, an output circuit 10 of the detection element 7, a humidity detection element 8 provided on the insulating substrate 1, and a humidity detection element 8 from the humidity detection element 8 when the humidity falls below a certain humidity. An electrochemical gas sensor comprising an output circuit 9 which outputs an output signal based on an input signal.