JP2000235016A - Control circuit for carbon monoxide sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly determine the level of carbon monoxide from the output voltage of a carbon monoxide sensor using a solid electrolyte body having a temperature characteristic. SOLUTION: The waveform of the output of an amplifier 8 amplifying a voltage between electrodes 2, 3 installed on a solid electrolyte plate 1 of a carbon monoxide sensor element part 7 is analyzed by a voltage waveform monitoring means 11, and a control voltage corresponding to a sensor working temperature is selected according to the waveform by switching between comparative voltage generating means 13a, 13b by means of a selector switch 11, thereby enhancing the detection accuracy of a sensor control circuit using a solid electrolyte having a temperature characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for detecting carbon monoxide using a carbon monoxide sensor used for controlling an air-fuel ratio of a combustion device, warning of incomplete combustion of the combustion device, and the like. In particular, the present invention relates to a device using a solid electrolyte as a carbon monoxide sensing element.

[0002]

2. Description of the Related Art A conventional control circuit for a carbon monoxide sensor has a configuration as shown in FIG. 10 (Japanese Patent Application No. H10-266195).

In FIG. 10, reference numeral 1 denotes a solid electrolyte plate having oxygen ion conductivity, and a pair of electrodes 2, 3 on its surface.
These electrodes 2 and 3 are formed by electron beam evaporation, sputtering, or thick film printing. A platinum electrode is usually used as the electrode.

[0004] Reference numeral 4 denotes a ceramic paper impregnated and held with an oxidation catalyst for carbon monoxide (the drawing is partially cut away), and has air permeability and covers the electrode 2. Reference numeral 5 denotes a heater formed on the surface of the ceramic plate 6 by vapor deposition or printing, and heats the solid electrolyte plate 1 and the ceramic paper 4 to operate as a sensor. The solid electrolyte plate 1, the ceramic plate 6, and the ceramic paper 4 constitute a carbon monoxide sensor element section 7. Further, after the electrode output voltages of the electrodes 2 and 3 are amplified by the amplifier 8, the output voltage and the integration circuit 9 are differentiated by the voltage comparator 10, and the output of the sensor is determined based on the difference output voltage.

[0005]

However, the solid electrolyte has a temperature characteristic with respect to the detection of carbon monoxide. If the operating temperature is different, even if the concentration of carbon monoxide is the same, the output of the solid electrolyte becomes different. In addition, it has the characteristic that there is a difference in responsiveness. In order to eliminate this difference in characteristics, it is desirable to maintain a constant output and responsiveness by keeping the operating temperature constant. For example, the exhaust temperature of a gas water heater is about 250 ° C. The difference reached close to 200 ° C., and it was very difficult to completely compensate for the temperature difference by controlling the temperature of the surface heater and to keep the detection characteristics of solid electrolyte carbon monoxide constant. In the control circuit of the conventional carbon monoxide sensor shown in FIG. 10, the voltage between the electrodes of the sensor is simply measured and controlled, and the output and the response to the temperature of the solid electrolyte are reduced. No correction was made to it. Therefore, the detection of the sensor becomes uncertain due to the ambient temperature where the sensor is installed, and there is a problem that the carbon monoxide cannot be accurately detected at a constant concentration due to an early or late cut.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a solid electrolyte plate having oxygen ion conductivity and having a pair of electrodes on its surface and a heating means for the solid electrolyte plate. A carbon monoxide sensor element configured by providing a carbon monoxide oxidation catalyst layer on one side of a ceramic plate and an electrode; an amplifying means for amplifying a voltage between electrodes of the carbon monoxide sensor element; and an output voltage of the amplifying means. Voltage waveform monitoring means for monitoring;
A plurality of comparison voltage generation means for generating a voltage to be compared with the output voltage of the amplification means, a voltage comparison means for comparing the output voltage of the amplification means with the output voltage of the comparison voltage generation means, and a comparison based on the output from the voltage waveform monitoring means A comparison voltage changing means for switching a voltage generated by the voltage generating means is provided.

According to the present invention, a voltage waveform is analyzed by monitoring the amplified output of a carbon monoxide sensor using a solid electrolyte body by a voltage waveform monitoring means, and a voltage level controlled by a difference in the voltage waveform is analyzed. To make changes.

In this method, an appropriate control voltage according to the operating voltage can be set by estimating the sensitivity of the solid electrolyte to carbon monoxide which changes depending on the temperature from the voltage waveform, and even if the temperature condition of the atmosphere in which the sensor is installed changes. There is an advantage that the concentration of carbon monoxide can be correctly detected.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid electrolyte plate having oxygen ion conductivity and a surface provided with a pair of electrodes, a ceramic plate provided with a heating means for the solid electrolyte plate, and a mono-oxide on one side of the electrodes. A carbon monoxide sensor element configured to include a carbon oxidation catalyst layer, amplification means for amplifying a voltage between the electrodes of the carbon monoxide sensor element, voltage waveform monitoring means for monitoring the output voltage of the amplification means, and amplification means. A plurality of comparison voltage generation means for generating a voltage to be compared with the output voltage; a voltage comparison means for comparing the output voltage of the amplification means with the output voltage of the comparison voltage generation means; It has a comparison voltage changing means for switching the generated voltage of the means, and can set a control voltage according to the sensor operating temperature from the waveform of the output voltage, thereby improving the reliability of the sensor.

The voltage estimating means includes a voltage measuring means for measuring a voltage between the electrodes of the carbon monoxide sensor element unit at regular time intervals, a voltage fluctuation detecting means for detecting a time fluctuation of the measured voltage, and a voltage measuring means. It comprises peak voltage value estimating means for estimating the attained voltage of the output voltage of the amplifying means from the output of the voltage fluctuation detecting means.
You can know the output level.

A solid electrolyte plate having oxygen ion conductivity and having a pair of electrodes on its surface, a ceramic plate provided with a heating means for the solid electrolyte plate, and a carbon monoxide oxidation catalyst layer provided on one side of the electrode. A carbon monoxide sensor element configured
Amplifying means for amplifying the voltage between the electrodes of the carbon monoxide sensor element, voltage estimating means for obtaining the final attainment voltage of the output voltage of the amplifying means, alarm notifying means for issuing an alarm by the output of the voltage estimating means, and a gas flow path. It has a closing means for closing the solenoid valve and a remote notifying means for notifying an abnormality through a data line.Based on the estimated output level, it notifies the danger, shuts off gas, and notifies the central monitoring station etc. through the data line of an abnormality. It informs and prevents the recurrence of danger.

An embodiment of the present invention will be described below with reference to FIGS. The same components as those in the conventional example are denoted by the same reference numerals.

[0013]

(Embodiment 1) FIG. 1 is a configuration diagram of a control circuit of a carbon monoxide sensor according to Embodiment 1 of the present invention.

In FIG. 1, reference numeral 1 denotes a solid electrolyte plate having oxygen ion conductivity, and a pair of electrodes 2 and 3 are provided on the surface thereof. It is formed by a printing method. A platinum electrode is usually used as the electrode.

Reference numeral 4 denotes a ceramic paper impregnated and held with a carbon monoxide oxidation catalyst (the drawing is partially cut away), and has air permeability and covers the electrode 2. Reference numeral 5 denotes a heater formed on the surface of the ceramic plate 6 by vapor deposition or printing, and heats the solid electrolyte plate 1 and the ceramic paper 4 to operate as a sensor. The solid electrolyte plate 1, the ceramic plate 6, and the ceramic paper 4 constitute a carbon monoxide sensor element section 7. The outputs of the electrodes 2 and 3 are input to an amplifier 8, and the output of the amplifier 8 is input to a voltage comparator 10. The output of the amplifier 8 is constantly monitored by the voltage waveform monitoring means 11, and the voltage waveform is analyzed. The comparison voltage generators 13a and 13b having different output voltages are selected by the changeover switch 12 according to the analyzed waveform, and the comparison voltage generator 13a is selected.
Alternatively, the output voltage of 13b is supplied to the voltage comparator 10 by the amplifier 9
Is input for comparison with the output voltage of

First, the operation of the carbon monoxide sensor having the above configuration will be described. The carbon monoxide gas that has passed through the ceramic paper 4 is oxidized when passing through the ceramic paper 4 and does not reach the electrode 2. Therefore, oxygen is ionized on the electrode 2 by the reaction represented by the formula (1).

1/2 O 2 +2 e ⁻ → O ^2- (1) On the other hand, in addition to the reaction represented by the formula (1), the reaction represented by the formula (2) also occurs at the electrode 3 because carbon monoxide arrives. ing.

CO + O ²⁻ → CO 2 + 2e ⁻ (2) Then, a potential difference occurs between the electrodes 2 and 3 due to a difference in reaction between the surfaces of the electrodes 2 and 3. That is, the potential difference changes according to the concentration of carbon monoxide, and the device operates as a carbon monoxide sensor.

The heater 5 is a heat source for heating the solid electrolyte plate 1 and the ceramic paper 4 to a constant temperature so that the reactions of the formulas (1) and (2) occur stably.

The voltage waveform monitoring means 11 analyzes the waveform of the output voltage of the amplifier 8. When it is determined from the rising speed and the voltage level of the output voltage of the amplifier 8 that the output voltage is slowly rising, the output of the voltage waveform monitoring means 11 causes the changeover switch 12 to select the comparison voltage generating means 13a outputting a high voltage. When it is determined that the voltage rises early, the output of the voltage waveform monitoring means 11 causes the changeover switch 12 to output a low voltage.
Select FIG. 2 shows the inter-electrode output depending on the temperature of the sensor element, and FIG. 3 shows the time response of the inter-electrode output of the sensor element depending on the temperature. As can be seen from FIG. 2, when the output for the same carbon monoxide concentration is compared, the response is higher when the temperature is low, and as shown in FIG. 3, the response to the same carbon monoxide concentration is faster when the temperature is high. . Therefore, the comparison voltage corresponding to the operation temperature of the sensor is obtained by the waveform
By inputting it to 0, proper detection of carbon monoxide can be performed irrespective of fluctuations in the operating temperature.

[0021] Instead of the ceramic paper 4, a carbon monoxide oxidizing catalyst may be held and a material having air permeability may be used. For example, even if a fibrous metal is used, the effect is not changed. The same applies to the following embodiments.

(Embodiment 2) FIG. 4 is a block diagram of the voltage waveform monitoring means 11 according to Embodiment 2 of the present invention.

The voltage waveform monitoring means 11 includes a voltage measuring means 14
And a voltage fluctuation detecting means 15 and a waveform determining means 16.

The output voltage of the amplifier 8 is measured by the voltage measuring means 14, and the voltage fluctuation detecting means 15 detects a voltage fluctuation from the measured voltage value and the measuring time interval. The waveform judging means 16 analyzes the waveform from the detected voltage fluctuation, and switches the changeover switch 11 to the comparison voltage generating means 13a,
An instruction is issued to select any one of the optimum voltage values of 3b.

FIG. 5 is a schematic diagram of the waveform analysis.
5A shows the waveform of the output voltage of the amplifier 8 when the temperature of the sensor is low, and FIG. 5B shows the waveform of the output voltage of the amplifier 8 when the temperature of the sensor is high.

When the temperature of the sensor shown in the upper part is low, the voltage values measured in time series continue to increase and the output is large. On the other hand, when the temperature of the sensor shown in the lower part is high, the voltage values measured in time series are immediately saturated and the output is small. Therefore, by varying the carbon monoxide detection level from the output waveform according to the operating temperature of the sensor, the control accuracy can be improved.

(Embodiment 3) FIG. 6 is a configuration diagram of a control circuit of a carbon monoxide sensor according to Embodiment 3 of the present invention.

The output voltage of the amplifier 8 is measured and analyzed for a certain period of time by the voltage estimating means 17 to obtain a final attained voltage.
An alarm notification instruction is issued to the alarm notification means 18. Control is performed based on information corrected by calculation from the output voltage of the amplifier 8, and even if the operating temperature of the sensor changes, the control can be performed quickly and accurately because the peak value is estimated.

(Embodiment 4) FIG. 7 is a configuration diagram of a control circuit of a carbon monoxide sensor according to Embodiment 4 of the present invention. The output voltage of the amplifier 8 is measured and analyzed for a certain period of time by the voltage estimating means 17 to obtain the final attained voltage.
At 8, a warning notification instruction is issued. Voltage estimating means 17
Output also controls the closing means 20 of the electromagnetic valve that closes the gas flow path, issues an alarm notification and simultaneously shuts off the gas, thereby preventing danger such as poisoning due to incomplete combustion.

(Embodiment 5) FIG. 8 is a block diagram of the voltage estimating means in Embodiment 5 of the present invention.

The output voltage of the amplifier 8 is measured by the voltage measuring means 14, and the voltage fluctuation detecting means 15 detects the fluctuation of the voltage from the measured voltage value and the measuring time interval. The output that has passed through the voltage measuring means 14 and the voltage fluctuation detecting means 15 enters the peak voltage value estimating means 21 to estimate the attained voltage, which is used as an alarm notification or information on gas shutoff. Since the control is performed by estimating the peak value, quick control can be performed.

(Embodiment 6) FIG. 9 is a configuration diagram of a control circuit of a carbon monoxide sensor according to Embodiment 6 of the present invention.

The output voltage of the amplifier 8 is measured and analyzed for a certain period of time by the voltage estimating means 17 to determine the final attained voltage.
An alarm notification instruction is issued to the alarm notification means 18. The output of the voltage estimating means 17 also controls the closing means 20 of the electromagnetic valve which closes the gas flow path, issues an alarm notification and simultaneously shuts off the gas, thereby preventing danger such as poisoning due to incomplete combustion. I do. It is also possible to send information to the modem 22 and monitor the state of the device at the centralized monitoring station based on the information from the modem 22.

[0034]

The present invention is embodied in the form described above and has the following effects.

By analyzing the output voltage waveform after the amplification of the voltage between the electrodes of the sensor element and switching the control voltage, it becomes possible to perform control in consideration of the temperature characteristics of the sensor.

By analyzing the output voltage waveform after the amplification of the inter-electrode voltage of the sensor element, estimating the final attained voltage, and issuing an alarm, quick danger notification can be realized.

By analyzing the output voltage waveform after the amplification of the voltage between the electrodes of the sensor element, estimating the ultimate voltage, issuing an alarm and shutting off the combustion gas, the danger notification and accident prevention are realized. it can.

By analyzing the output voltage waveform after the amplification of the voltage between the electrodes of the sensor element, estimating the ultimate voltage, issuing an alarm and shutting off the combustion gas, danger notification and accidents are prevented. Further, by notifying the central monitoring station in a remote place, further security can be ensured.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a control circuit of a carbon monoxide sensor according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a temperature characteristic of an output of the same oxidation sensor element.

FIG. 3 is a diagram showing a temperature characteristic of an output response of the same carbon oxide sensor element.

FIG. 4 is a configuration diagram of a voltage waveform monitoring unit according to a second embodiment of the present invention.

5A is a schematic diagram of a waveform analysis when the sensor temperature is low in the embodiment of the present invention. FIG. 5B is a schematic diagram of a waveform analysis when the sensor temperature is high in the embodiment of the present invention.

FIG. 6 is a configuration diagram of a control circuit of a carbon monoxide sensor according to a third embodiment of the present invention.

FIG. 7 is a configuration diagram of a control circuit of a carbon monoxide sensor according to a fourth embodiment of the present invention.

FIG. 8 is a configuration diagram of a voltage estimating unit according to a fifth embodiment of the present invention.

FIG. 9 is a configuration diagram of a control circuit of a carbon monoxide sensor according to a sixth embodiment of the present invention.

FIG. 10 is a configuration diagram of a control circuit of a conventional carbon monoxide sensor.

[Explanation of symbols]

 Reference Signs List 1 solid electrolyte plate 2, 3 electrode 4 ceramic paper (carbon monoxide oxidation catalyst layer) 5 heater 6 ceramic plate 7 carbon monoxide sensor element 8 amplifier 10 voltage comparator (voltage comparing means) 11 voltage waveform monitoring means 12 changeover switch (Comparative voltage changing means) 13a, 13b Comparative voltage generating means 14 Voltage measuring means 15 Voltage fluctuation detecting means 16 Waveform judging means 17 Voltage estimating means 18 Alarm notifying means 20 Closing means 21 Peak voltage value estimating means 22 Modem (remote notifying means)

Continuing on the front page (72) Inventor Takahiro Umeda 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. ) 2G004 BB04 BF07 BL19 BL20 BM04

Claims (6)

[Claims] 1. A solid electrolyte plate having oxygen ion conductivity and having a pair of electrodes on its surface, a ceramic plate provided with a heating means for said solid electrolyte plate, and a carbon monoxide oxidation catalyst layer on one side of said electrode A carbon monoxide sensor element configured to include: amplifying means for amplifying a voltage between the electrodes of the carbon monoxide sensor element, a voltage waveform monitoring means for monitoring an output voltage of the amplifying means, and an output of the amplifying means. A plurality of comparison voltage generation means for generating a voltage to be compared with a voltage; a voltage comparison means for comparing an output voltage of the amplification means with an output voltage of the comparison voltage generation means; and an output from the voltage waveform monitoring means. A control circuit for a carbon monoxide sensor having comparison voltage changing means for switching a voltage generated by a comparison voltage generation means. 2. The voltage waveform monitoring means includes: a voltage measuring means for measuring an output voltage of the amplifying means at predetermined time intervals; a voltage fluctuation detecting means for detecting a time fluctuation of the measured voltage; 2. A control circuit for a carbon monoxide sensor according to claim 1, further comprising a waveform determining means for determining a waveform of an output voltage of said amplifying means from an output of said detecting means. 3. A solid electrolyte plate having oxygen ion conductivity and having a pair of electrodes on its surface, a ceramic plate provided with a heating means for said solid electrolyte plate, and a carbon monoxide oxidation catalyst layer on one side of said electrode. A carbon monoxide sensor element configured to include: an amplifying means for amplifying a voltage between the electrodes of the carbon monoxide sensor element; a voltage estimating means for estimating a final attained voltage from an output voltage of the amplifying means; A control circuit for a carbon monoxide sensor having an alarm notifying unit that issues an alarm based on the output of the estimating unit. 4. A solid electrolyte plate having oxygen ion conductivity and having a pair of electrodes on its surface, a ceramic plate provided with a heating means for said solid electrolyte plate, and a carbon monoxide oxidation catalyst layer on one side of said electrodes. A carbon monoxide sensor element configured to include: an amplifying means for amplifying a voltage between the electrodes of the carbon monoxide sensor element; a voltage estimating means for obtaining a final attained voltage from an output voltage of the amplifying means; A control circuit for a carbon monoxide sensor, comprising: an alarm notifying unit for issuing an alarm according to an output of the unit; and a closing unit for an electromagnetic valve for closing a gas flow path. 5. A voltage estimating means for measuring a voltage between the electrodes of the carbon monoxide sensor element unit at predetermined time intervals, a voltage fluctuation detecting means for detecting a time fluctuation of the measured voltage, and the voltage measuring means. 5. The control circuit for a carbon monoxide sensor according to claim 3, further comprising means and a peak voltage value estimating means for estimating an attained voltage of an output voltage of said amplifying means from an output of said voltage fluctuation detecting means. 6. A solid electrolyte plate having oxygen ion conductivity and having a pair of electrodes on its surface, a ceramic plate provided with a heating means for said solid electrolyte plate, and a carbon monoxide oxidation catalyst layer on one side of said electrode. A carbon monoxide sensor element configured to include: an amplifying means for amplifying a voltage between the electrodes of the carbon monoxide sensor element; a voltage estimating means for obtaining a final attained voltage from an output voltage of the amplifying means; A control circuit for a carbon monoxide sensor, comprising: an alarm notifying means for issuing an alarm according to the output of the means; a closing means for an electromagnetic valve for closing a gas flow path; and a remote notifying means for notifying an abnormality through a data line.