JP2003294688A - Gas detecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To materilize a highly reliable gas detecting apparatus with resistance to noise. <P>SOLUTION: A control means 9 switches between the ON and OFF of an FET 12 of an electric power supply means 8 by switching the output from a pulse output means 11, and controls electric power supply for a heater 5 as a result. The control means 9 comprises an amplifier 13 and a filter 14 for processing output signals of a gas detector 7 and a determining means 15 for determining the concentration of gas, and determines the concentration of the gas on the basis of the output Vs (t2) of the gas detecting part at a previously set time (at a timing t2 after a minute time Δt after the termination of power supply. By this constitution, it is possible to determine the concentration of the gas without receiving noise during power supply or noise which occurs at the rise and fall of the power. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas detector for detecting a gas such as carbon monoxide.

[0002]

2. Description of the Related Art As a conventional gas detecting device of this type, for example, a carbon monoxide detecting device is disclosed in Japanese Unexamined Patent Publication No.
There was a thing as described in 346825. FIG. 11 shows the conventional carbon monoxide gas detection device described in the above publication.

In FIG. 11, 1 is a solid electrolyte plate, 2, 3
Is an electrode, 4 is a carbon monoxide oxidation catalyst, and 5 is a heater as a heating element, which is formed on the ceramic plate 6.
By energizing the heater 5, the solid electrolyte plate 1 and the carbon monoxide oxidation catalyst 4 are raised to a predetermined temperature, and as a result,
A voltage corresponding to the carbon monoxide concentration is output between the electrodes 2 and 3, the carbon monoxide concentration is known from the output voltage, and an alarm is issued to prevent a carbon monoxide poisoning accident.

Further, Japanese Patent No. 2791473 discloses a method of controlling power supply to a heater, in which the heater temperature is raised by intermittently applying pulses, or carbon monoxide is added at any time before and after the end of the pulse. It is described that the concentration can be detected.

[0005]

It has been pointed out that in recent years, houses have become more airtight and highly insulated, and the risk of incomplete combustion of indoor combustion equipment and poisoning due to carbon monoxide gas accompanying a fire has increased more than ever before. . In addition, with the increase in the number of elderly households, the importance of promptly informing of danger in the event of a fire or gas leak is increasing.

However, in the above conventional configuration, FIG.
The impedance between the electrodes 2 and 3 of the
Since it is MΩ or more) and the output is small (about several tens of mV), the structure is easily affected by noise.

First, when the amount of power supplied to the heater is constant,
Since the temperature distribution of the heater is not completely uniform and the external temperature environment also changes, it is possible that the state of thermal expansion of each component changes or the level of thermal noise changes. Further, the ceramic plate 6 is electrically connected so that the heater and the electrode are not short-circuited although it is desired to short-circuit the heater in order to quickly transfer the heat of the heater to the solid electrolyte plate 1 and the carbon monoxide oxidation catalyst 4. They are designed for the conflicting purposes of insulating. Therefore, when importance is attached to a thermal short circuit, it is necessary to make the ceramic plate 6 thin and prepare for an electrical leak to some extent. In this case, the problem of leakage between the heater and the electrodes is considered to be a problem only when current is flowing through the heater, that is, when power is supplied.

Further, when power is supplied to the heater by intermittent pulses in order to suppress the power consumption, the state of heat radiation changes depending on the external temperature environment, so the speed of temperature rise changes, and further changes in thermal expansion and The level of thermal noise may change. Further, there is a problem that switching noise occurs at the rising and falling edges of the pulse.

The present invention solves the above-mentioned conventional problems, and reduces noise at the time of detection by controlling so as to determine the gas concentration based on a signal from the gas detection unit after the power supply to the heating element is stopped. The purpose of the present invention is to detect gas at an early stage with high accuracy and to minimize the damage of gas poisoning due to incomplete combustion.

[0010]

In order to solve the above-mentioned conventional problems, a gas detecting apparatus of the present invention is a gas detecting section for generating a signal according to a gas concentration in a predetermined temperature range, and the gas detecting section. A heating element that heats the heating element, an electric power supply unit that supplies electric power to the heating element, and a control unit that controls the electric power supply unit to determine the gas concentration based on a signal from the gas detection unit after the supply of electric power to the heating element is stopped. It is provided with a control means for controlling.

Thus, the gas concentration can be determined without receiving noise during power supply and noise generated at the rise and fall of power.

[0012]

DETAILED DESCRIPTION OF THE INVENTION A gas detecting device according to the invention of claim 1 is a gas detecting portion for generating a signal according to a gas concentration in a predetermined temperature range, and a heating element for heating the gas detecting portion. Power supply means for supplying electric power to the heating element, and control means for controlling the power supply means and for determining gas concentration based on a signal from the gas detection unit after the power supply to the heating element is stopped Is.

Further, in the gas detector of the invention described in claim 2, the control means determines the gas concentration after a lapse of a predetermined time from the stop of the electric power supply to the heating element.

Further, the gas detector of the invention according to claim 3 has a temperature detecting means for detecting the temperature of at least one of the gas detecting portion and the heating element, and the control means has a time for judging the gas concentration based on the temperature. Is to determine.

Further, the gas detector of the invention described in claim 4 judges the gas concentration when the temperature after the power supply to the heating element is stopped reaches a predetermined temperature.

Further, in the gas detector of the fifth aspect of the invention, the time for determining the gas concentration is changed according to the temperature when the power supply to the heating element is stopped. As a result, the gas concentration can be determined without receiving noise during power supply or noise generated at the rise or fall of power.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a configuration diagram of a gas detection apparatus according to Embodiment 1 of the present invention.

The gas detector has a gas detector 7, a heater 5 as a heating element, a power supply means 8 and a control means 9. The control means 9 performs control based on the timer 10, and switches the output (high / low) from the pulse output means 11 depending on time to switch the FET 12 of the power supply means 8 on / off, and as a result, The power supply to the heater 5 is controlled. Further, the control means 9
It has an amplifier 13 for processing the output signal of the gas detector 7, a filter 14, and a determination means 15 for determining the gas concentration, and is configured to determine the gas concentration according to a preset time.

FIG. 2 is a time chart showing the electric power Ph supplied to the heater and the output voltage Vs of the gas detector.
This is the case where the gas concentration is constant, (a) shows the passage of time of the electric power Ph supplied to the heater, and (b) shows the passage of time of the output voltage Vs of the gas detector.

By supplying electric power from time 0 to t1, the temperature of the heater is raised and, as a result, the temperature of the gas detecting portion is gradually raised, but the temperature is naturally lowered after t1. The output of the gas detector should originally generate a DC voltage proportional to the gas concentration if the temperature of the gas detector is within a predetermined temperature range. The output between t1 and t1 changes in a complicated manner. Therefore, in the present embodiment, when the electric power is not supplied to the heater, specifically, the small Δ
At the timing of t2 after t, the output Vs (t
The gas concentration is judged based on 2). Δt is set in advance as a fixed time.

FIG. 3 shows the gas concentration and the output Vs of the gas detector.
It is a characteristic diagram showing the correlation of (t2), and since there is a good correlation, the gas concentration can be determined based on Vs (t2).

Here, the electric power supplied to the heater, t1,
The time such as Δt should be optimized so that when the output of the gas detection unit is taken in, the temperature of the gas detection unit falls within a predetermined temperature range and noise such as leak from the heater and noise at the fall is reduced. Good.

As an example, the temperature of the gas detector is set to 350.degree.
Power supply 4W, t1 = 10 ms, Δt =
An example is 100 μs. With this configuration,
Since the gas concentration is detected when the temperature of the gas detection part is within the specified temperature range and the power supply to the heater is stopped, noise during power supply and noise that occurs at the rise and fall of power is eliminated. The gas concentration can be determined without receiving it. Therefore, noise during gas detection can be reduced, gas can be detected accurately at an early stage, and damage of gas poisoning due to incomplete combustion can be prevented or minimized.

FIG. 4 is a perspective view showing the structures of the gas detecting portion 7 and the heater 5. Specifically, it is a case where the detection gas is carbon monoxide gas. In FIG. 4, 1 is 300 ° C. to 500 ° C.
A solid electrolyte plate having oxygen ion conductivity under high temperature of
A pair of electrodes 2 and 3 is provided on the surface, and these electrodes 2 and 3 are formed by electron beam vapor deposition, sputtering or thick film printing. A platinum electrode is usually used as the electrode.

Reference numeral 4 denotes a carbon monoxide oxidation catalyst layer impregnated with a carbon monoxide oxidation catalyst (which is partially cut out in the drawing), which has air permeability and covers the electrode 2. A heater 5 formed on the surface of the ceramic plate 6 by vapor deposition or printing heats the solid electrolyte plate 1 and the carbon monoxide oxidation catalyst layer 4 to operate as a carbon monoxide detection element. A voltage corresponding to the carbon monoxide concentration is output between the electrodes 2 and 3. The carbon monoxide oxidation catalyst layer 4
The electrodes 2, 3 and the solid electrolyte plate 1 constitute a gas detection unit 7. The operation and action of the gas detector configured as above will be described below.

First, the operation of carbon monoxide detection with the above configuration will be described. When heated to a predetermined temperature, the carbon monoxide gas which is about to pass through the carbon monoxide oxidation catalyst layer 4 is oxidized when passing through the carbon monoxide oxidation catalyst layer 4 and does not reach the electrode 2. Therefore, in the vicinity of the electrode 2 in the solid electrolyte plate 1, the oxygen atom adsorbed on the electrode 2 is ionized by the reaction of O + 2e ⁻ → O ^{2 −} .

On the other hand, in the vicinity of the electrode 3, in addition to the above reaction, carbon monoxide gas arrives, so that CO + O ^2- → C
O2 + 2e ^- consisting of reaction it is also happening.

Then, the electrodes 2 and 3 of the solid electrolyte plate 1
A potential difference is generated between the electrodes 2 and 3 due to the difference in reaction in the vicinity of. That is, the potential difference changes according to the concentration of carbon monoxide, and the device operates as a carbon monoxide detection element.

The heater 5 is a heat source for heating the solid electrolyte plate 1 and the carbon monoxide oxidation catalyst layer 4 to a constant temperature so that the respective reactions occur stably.

Here, an example of carbon monoxide detection has been described as an example of a gas detection device, but the present invention is also effective for a gas detection device that detects a combustible gas such as methane gas or propane gas by heating the detection portion. Needless to say.

Although not shown, it is conceivable to output a warning command from the control means 9 to the notification means to notify the danger. It is also possible to combine with another device such as a fire alarm or a gas leak alarm or to perform communication to perform comprehensive hazard notification and display.

(Embodiment 2) FIG. 5 is a block diagram of a gas detector according to Embodiment 2 of the present invention. In this embodiment, a thermistor 16 as a temperature detecting means is provided near the gas detecting section 7. The reference voltage 18 is divided by the thermistor 16 and the fixed resistor 17, and the determination unit 15 detects the temperature of the thermistor 16 based on this voltage value and estimates the temperature of the gas detection unit 7.

FIG. 6 is a time chart showing the power Ph supplied to the heater, the temperature T of the gas detector 7, and the output voltage Vs of the gas detector. This is a case where the gas concentration is constant, (a) shows the time passage of the electric power Ph supplied to the heater, (b) shows the time passage of the temperature T of the gas detection unit 7,
(C) shows the passage of time of the output voltage Vs of the gas detector.

By supplying electric power from time 0 to t3, the temperature of the heater is raised and, as a result, the temperature of the gas detecting portion is gradually raised, but after t3, the temperature is naturally lowered. In the present embodiment, the temperature of the gas detection portion can be estimated by the thermistor, so it is possible to detect the output voltage Vs (t4) at the instant t4 when the temperature drops to T1. Therefore, the gas concentration at the predetermined temperature T1 can be accurately detected. When the gas detection unit has a temperature characteristic, the output signal at the same temperature is detected every time as compared with the method of the first embodiment in which the gas detection unit detects the gas after a certain period of time, so that the accuracy of gas concentration determination can be improved. (Embodiment 3) FIG. 7 shows Embodiment 3 of the present invention.
It is a block diagram of the gas detection apparatus of. In this embodiment, when the resistance value of the heater has a correlation with the temperature, the temperature detecting means 19 is composed of a circuit element. A resistor 20 is connected to the heater 5 in series, the voltages across the heater 5 are amplified by amplifiers 21 and 22, respectively, and the temperature is calculated by the calculation means 23.

FIG. 8 is a characteristic diagram of heater temperature and heater resistance. If the relationship between the heater temperature and the resistance value is obtained in advance, the temperature can be obtained by detecting the resistance value. Since the resistance value is the ratio of the voltage and current applied to the heater, it is possible to detect in real time when current is flowing. For example, assuming that the upper voltage of the heater 5 in FIG. 7 is Vh (+), the lower voltage is Vh (-), and the resistance value of the series resistor 20 is R1, the heater resistance value is (Vh
(+)-Vh (-)) / (Vh (-) / R1).
However, it should be noted that in this method, when the electric power is not supplied to the heater, the resistance value cannot be obtained because the current does not flow. Further, the voltage input to the calculation means 23 is the amplifier 21 or 2.
Since it is through 2, it must be calculated by the value divided by the amplifier gain.

FIG. 9 shows the electric power Ph supplied to the heater (or the voltage Vh (+) on the upper side of the heater 5, the voltage Vh (-) on the lower side of the heater, the temperature T obtained by the calculating means 23, and the gas detection unit. It is a time chart which shows output voltage Vs. This is the case where the gas concentration is constant, and the power supply is performed by the narrow pulse control of the time width. (A)
Is the electric power Ph supplied to the heater (or the voltage Vh (+) on the upper side of the heater 5), (b) is the voltage Vh (-) on the lower side of the heater, and (c) is the calculating means 2
3, the time T of the temperature T obtained in 3 is shown, and (d) shows the time passage of the output voltage Vs of the gas detection unit. Since Vh (+) and the resistance value of the series resistor 20 are constant, (b) Vh (-) may be considered to indicate a change in current. Initially, the heater temperature is low, so the resistance value is low, so the current value is large, but
As the heater temperature rises, the resistance value rises, so the current value gradually drops. The heater temperature at this time can be calculated as shown by the solid line in (c), and the power supply is stopped when the temperature exceeds the set temperature T2. In reality, if the temperature at stop t5 becomes T3 due to overshoot after exceeding T2, Δt2 is changed accordingly to determine t6, and Vs (t6) at the estimated temperature T4 is detected. To determine the gas concentration. As an example, in FIG. 10, T3 and Δ
The correlation of t2 is shown as a characteristic diagram. When the overshoot is large, T3 becomes large, so Δt2 is lengthened to decrease the temperature, and when the overshoot is small, Δt is increased.
By performing control such that 2 is shortened and the temperature is not lowered so much, correction is performed so that the gas concentration is always determined at the temperature T4.

In this embodiment, when the power supply is stopped, the power Ph is reduced to 0, but instead of this, there is a method of switching from the large power Ph to the minute power Plow. Since the resistance value can be calculated even if a small amount of current is applied, the estimated temperature shown by the broken line in FIG. 9C can be actually calculated, and control based on accurate temperature becomes possible. However, it is necessary to judge how much noise is generated by a small amount of electric power, and whether or not to adopt it by observing the size of the noise.

[0039]

As described above, the gas detecting device according to the first to fifth aspects includes a gas detecting section for generating a signal according to the gas concentration within a predetermined temperature range, and heat generation for heating the gas detecting section. A body, an electric power supply means for supplying electric power to the heating element, and a control means for controlling the electric power supply means and for determining a gas concentration by a signal from the gas detection unit after the electric power supply to the heating element is stopped. Be prepared.

As a result, the gas concentration can be determined without receiving noise during power supply and noise generated at the rise and fall of power. Therefore, noise during gas detection can be reduced, gas can be detected accurately at an early stage, and damage of gas poisoning due to incomplete combustion can be prevented or minimized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a gas detection device according to a first embodiment of the present invention.

FIG. 2 is a time chart showing the power supplied to the heater and the output voltage of the gas detection unit in the first embodiment of the present invention.

FIG. 3 is a gas concentration-output voltage characteristic diagram of the gas detection unit according to the first embodiment of the present invention.

FIG. 4 is a perspective view showing a configuration of a gas detection unit and a heater according to the first embodiment of the present invention.

FIG. 5 is a configuration diagram of a gas detection device according to a second embodiment of the present invention.

FIG. 6 is a time chart showing the power supplied to the heater, the temperature of the gas detection unit, and the output voltage of the gas detection unit according to the second embodiment of the present invention.

FIG. 7 is a configuration diagram of a gas detection device according to a third embodiment of the present invention.

FIG. 8 is a heater temperature-heater resistance characteristic diagram of the third embodiment of the present invention.

FIG. 9 is a time chart showing the electric power supplied to the heater (or the voltage on the upper side of the heater), the voltage on the lower side of the heater, the temperature obtained by the calculating means, and the output voltage of the gas detection unit according to the third embodiment of the present invention.

FIG. 10 is a temperature-judgment time characteristic diagram of the third embodiment of the present invention.

FIG. 11 is a configuration diagram of a conventional carbon monoxide gas detection device.

[Explanation of symbols]

5 Heater (heating element) 7 Gas detector 8 power supply means 9 Control means 16 Thermistor (temperature detection means) 19 Temperature detecting means

Continued front page    (72) Inventor Masao Maki             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Katsuhiko Uno             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Takashi Niwa             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Kunihiro Tsuruta             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Takahiro Umeda             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 2G004 BB04 BC02 BF07 BJ02 BK01                       BL06 BL10 BM04 BM09

Claims (5)

[Claims] 1. A gas detecting section for generating a signal according to a gas concentration within a predetermined temperature range, a heating element for heating the gas detecting section, and an electric power supply means for supplying electric power to the heating element.
A gas detection device comprising: a control unit that controls the power supply unit and determines a gas concentration based on a signal from the gas detection unit after the power supply to the heating element is stopped. 2. The gas detection device according to claim 1, wherein the control means determines the gas concentration after a lapse of a fixed time from the stop of the power supply to the heating element. 3. A temperature detecting means for detecting the temperature of at least one of the gas detecting portion and the heating element, wherein the control means comprises:
The time for determining the gas concentration is determined by the temperature.
The gas detector described. 4. The gas detection device according to claim 3, wherein the gas concentration is determined when the temperature after the power supply to the heating element is stopped reaches a predetermined temperature. 5. The gas detection device according to claim 3, wherein the time for determining the gas concentration is changed according to the temperature when the power supply to the heating element is stopped.