JP3715162B2 - Gas detection device and gas detection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention uses a single gas sensor to detect gas components generated during a fire and other gases such as carbon monoxide (CO) generated during incomplete combustion and methane (CH ₄ ) generated when a city gas leaks. The present invention relates to a gas detection device and a gas detection method that are identified.
[0002]
[Prior art]
As a gas sensor for distinguishing between carbon monoxide generated at the time of incomplete combustion and methane generated at the time of city gas leakage, for example, a semiconductor type gas sensor has been conventionally used, and the catalytic activity of this semiconductor gas sensor is utilized. Distinguish between carbon monoxide and methane. FIG. 11 shows gas sensitivity characteristics of a semiconductor gas sensor using a SnO ₂ catalyst.
[0003]
In FIG. 11, the horizontal axis represents the sensor element temperature, and the vertical axis represents the sensor resistance. As can be seen from FIG. 11, the SnO ₂ catalyst has a high activity for carbon monoxide at a low temperature range and a high activity for methane at a high temperature range. In other words, carbon monoxide has low sensor resistance at low temperatures and methane has low sensor resistance at high temperatures. Therefore, semiconductor gas sensors have the property of selecting carbon monoxide at low temperatures and methane at high temperatures. .
[0004]
For this reason, one gas sensor provided in the gas detection device is periodically and alternately driven in a low temperature region (for example, 100 ° C.) and a high temperature region (for example, 400 ° C.) by the pulse driving method as shown in FIG. By doing so, it is possible to detect the carbon monoxide gas concentration at the low temperature CO detection point (black circle in FIG. 12) and to detect the methane gas concentration at the high temperature methane detection point (black circle in FIG. 12). it can.
[0005]
As a conventional gas detector of this type, for example, a gas leak detector described in Japanese Patent Application Laid-Open No. 59-143948 is known.
[0006]
As shown in FIG. 13, the gas leak detection apparatus disclosed in Japanese Patent Laid-Open No. 59-143948 includes a metal oxide sensitive body 102 whose resistance value decreases when it is exposed to a combustible gas, and the sensitive body 102. , A heater 103 that maintains a predetermined temperature, a voltage discriminating circuit 106 that detects a change in the resistance value of the sensitive body 101, a heater voltage control circuit 105 that changes the heater voltage of the heater 103 based on the output of the voltage discriminating circuit 106, And an arithmetic circuit 108 that detects temperature dependence based on a change in the resistance value of the sensitive body 101 and discriminates the type of combustible gas.
[0007]
According to such a gas leak detection apparatus, when the combustible gas touches the sensitive body 102 and the resistance value decreases and the potential at the point A falls below the set reference potential, the voltage discrimination circuit 106 is activated. The timer circuit 107 is activated, and the voltage applied to the heater 103 is changed by the heater voltage control circuit 105.
[0008]
Then, the potential of the heater 103 before and after the voltage change is calculated by the calculation circuit 108, and the temperature dependence of the currently detected gas is calculated, whereby the type of characteristic gas can be detected.
[0009]
[Problems to be solved by the invention]
However, the conventional gas detector and the gas leak detector described in Japanese Patent Application Laid-Open No. 59-143948 distinguish between carbon monoxide generated during incomplete combustion and methane generated when city gas leaks. However, it was not possible to distinguish between the gas generated during a fire and the methane generated during leakage of carbon monoxide and city gas generated during incomplete combustion. In addition, even the gas components generated in the event of a fire are not clearly understood.
[0010]
Therefore, the present invention provides a gas detection device and gas that can easily distinguish between gas components generated during a fire and other gases such as carbon monoxide generated during incomplete combustion and methane generated when a city gas leaks. It is an object to provide a detection method.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has the following configuration. The gas detection device according to the first aspect of the present invention is a catalytic combustion type gas sensor provided with a heater and a sensor element for detecting gas, generates a pulse drive signal, and applies the pulse drive signal to the heater. Pulse driving means for driving the catalytic combustion type gas sensor on / off, and sampling means for sampling sensor output values detected by the sensor element at a plurality of gas detection points during the on driving period of the catalytic combustion type gas sensor The sampling means generates the gas at the time of a fire or a non-fire based on changes in the sensor output values sampled at a plurality of gas detection points during the on-drive period of the catalytic combustion gas sensor. Gas identifying means for identifying whether the gas is a gas, the gas identifying means is a first gas It exceeds the sensor output value sensor output value at the point out of the second gas detection point after the first gas detection point time, and the sensor output value in the second gas detection point third gas detection after the second gas detection point time When the sensor output value at the point is exceeded, the gas is determined as a gas generated at the time of a fire, and the sensor output value at the first gas detection point is a sensor at the second gas detection point after the first gas detection point time. If the sensor output value at the second gas detection point is less than the output value , and the sensor output value at the third gas detection point is less than the sensor output value at the third gas detection point , the gas is determined to be a gas generated at the time of non-fire.
[0012]
According to the gas detection apparatus of the first aspect of the invention, when the pulse driving means generates a pulse driving signal and applies the pulse driving signal to the heater to drive the catalytic combustion type gas sensor on / off, the sampling means Sample the sensor output value detected by the sensor element at a plurality of gas detection points during the on-drive period of the catalytic combustion type gas sensor, and the gas identification means uses the sampling means during the on-drive period of the catalytic combustion type gas sensor. Based on changes in sensor output values sampled at multiple gas detection points, the gas is identified as a gas generated during a fire or a non-fire gas. Easily identify gases such as carbon monoxide generated during combustion and methane generated when city gas leaks Rukoto can. Further, the sensor output value at the first gas detection point exceeds the sensor output value at the second gas detection point after the first gas detection point time , and the sensor output value at the second gas detection point is after the second gas detection point time. When the sensor output value at the third gas detection point is exceeded , the gas identification means can determine that the gas is a gas generated at the time of the fire, and the sensor output value at the first gas detection point is the first gas detection point time. If the sensor output value at the later second gas detection point is less than the sensor output value at the second gas detection point, and the sensor output value at the third gas detection point is less than the sensor output value at the third gas detection point , Can be judged.
[0017]
According to a second aspect of the present invention, the first gas detection point is set at a substantially middle point of the on-drive period, the third gas detection point is set at a substantially end point of the on-drive period , and the second gas detection point The point is set at a substantially middle point between the first gas detection point and the third gas detection point .
[0018]
According to the invention of claim 2, the first gas detection point is set at a substantially middle point of the on-drive period, the third gas detection point is set at a substantially end point of the on-drive period , and the second gas detection point is Since the first gas detection point and the third gas detection point are set at a substantially intermediate point, the sensor outputs of the second gas detection point and the third gas detection point with respect to the sensor output value of the first gas detection point . The change in value is easily understood.
[0019]
A gas detector according to a third aspect of the invention is characterized by comprising a notifying means for notifying the identification result of the type of gas identified by the gas identifying means.
[0020]
Since the notification means of the invention of claim 3 reports the identification result of the gas type identified by the gas identification means, the generated gas type can be easily identified, thereby improving safety. Can do.
[0021]
According to a fourth aspect of the present invention, there is provided a gas detecting method for generating a pulse driving signal and applying the pulse driving signal to a heater provided in the catalytic combustion type gas sensor to drive the catalytic combustion type gas sensor to be on / off driven. A sampling step of sampling a sensor output value detected by a sensor element provided in the catalytic combustion type gas sensor at a plurality of gas detection points during the on-driving period of the catalytic combustion type gas sensor; A gas identification step of identifying the type of gas based on a plurality of sensor output values sampled at a plurality of gas detection points during the on-drive period of the combustion gas sensor, wherein the gas identification step comprises a first gas detection step The sensor output value at the point is the second gas after the first gas detection point time. Exceeds the sensor output value at the detection point, and when the sensor output value in the second gas detection point exceeds the sensor output value in the third gas detection point after the second gas detection point time, the gas in a fire It is determined that the gas is generated, the sensor output value at the first gas detection point is less than the sensor output value at the second gas detection point after the first gas detection point time , and the sensor output value at the second gas detection point is third. When it is less than the sensor output value at the gas detection point, the gas is determined as a gas generated at the time of non-fire.
[0024]
According to a fifth aspect of the present invention, the first gas detection point is set at a substantially middle point of the on-drive period, the third gas detection point is set at a substantially end point of the on-drive period , and the second gas detection point The point is set at a substantially middle point between the first gas detection point and the third gas detection point .
[0025]
According to a sixth aspect of the present invention, the gas detection method includes a notification step of notifying the identification result of the gas type identified in the gas identification step.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a gas detection device and a gas detection method of the present invention will be described in detail with reference to the drawings.
[0027]
FIG. 1 is a circuit configuration diagram of a gas detection device according to an embodiment of the present invention. FIG. 2 is a detailed structural diagram of the gas sensor in the gas detection apparatus according to the embodiment. FIG. 3 is a timing chart of the temperature of the gas sensor in the gas detection device of the embodiment.
[0028]
The gas detection device and the gas detection method according to the embodiment include a gas component (acid-containing compound such as acetic acid or carbon monoxide) generated during a timber fire, and carbon monoxide or city gas leak generated during incomplete combustion. It is characterized by distinguishing methane generated.
[0029]
In the gas detection apparatus shown in FIG. 1, the gas sensor 1 is, for example, a catalytic combustion type gas sensor, and this catalytic combustion type gas sensor is a gas detection element having a heater (hereinafter referred to as a sensor element) and a comparison element having a heater. The combustion heat generated when the gas is burned is detected, and the gas is identified based on the obtained sensor output.
[0030]
The gas sensor 1 includes a heater 2 made of platinum (Pt) for heating a catalyst, a sensor element 3 for detecting various gases, and a comparison element 4. 2A is a sectional view of the gas sensor 1, and FIG. 2B is a top view of the gas sensor. The gas sensor 1 is composed of a microsensor, and has a sensor element 3 and a comparison element 4 as shown in FIG. 2, and the sensor element 3 and the comparison element 4 detect gas.
[0031]
A substrate 33 made of silicon single crystal is provided on the sensor base 31, and a diaphragm 35 is formed on the substrate 33. The diaphragm 35 is formed by anisotropically etching the substrate 33.
[0032]
Each of the sensor element 3 and the comparison element 4 is provided on the substrate 33 and is in contact with the diaphragm 35 on the oxide film 37 and the Si ₃ N ₄ film 39 made of the SiO ₂ film stacked on the diaphragm 35. Are stacked.
[0033]
Each of the sensor element 3 and the comparison element 4 has a heater 2, the heater 2 of the sensor element 3 is connected to the electrodes 41a and 41b, and the heater 2 of the comparison element 4 is connected to the electrodes 41c and 41d. The electrodes 41a to 41d are fixed by wire bonding of gold (gold wire 43).
[0034]
The sensor element 3 includes a heater 2 for urging gas combustion, and a catalyst layer 45 formed on the heater 2 and using γ-alumina supported by 5 to 15 wt% of palladium (Pd) as a catalyst. The comparison element 4 includes a heater 2 and a catalyst layer (not shown) laminated on the heater 2 and using γ-alumina or α-alumina as a catalyst. The heater 2 promotes gas combustion, and the catalyst layer 45 generates heat according to the amount of heat generated by the heater 2 and acts as a catalyst for gas combustion.
[0035]
According to the gas sensor 1 having the above configuration, the calorific value generated by the heater 2 can be efficiently conducted in a short time to the catalyst layer 45, so that the gas can be burned with high sensitivity and high speed. it can.
[0036]
1 includes a bridge circuit 6 having a sensor element 3 and a comparison element 4 connected in series. The bridge circuit 6 includes a sensor element 3 and a comparison element 4 connected in series, and resistors R10 to R12 connected in series, connected in parallel. The bridge circuit 6 is supplied with + 5V power via a transistor Tr2 and resistors R7 to R9 connected in parallel.
[0037]
The bridge circuit 6 detects changes in the resistance value of the sensor element 3 caused by combustion heat generated when the sensor element 3 and the comparison element 4 burn gas, and changes in the resistance value of the comparison element 4. It detects from the connection point of the element 3 and the comparison element 4, and outputs it to the central processing unit (CPU) 11 mentioned later as a sensor output.
[0038]
The integrated circuit (IC) 1 is supplied with +5 V power, and the IC 1 inputs the potentials of the resistors R7 to R9 to the non-inverting input terminal, inputs the reference voltage to the inverting input terminal, and outputs the calculation output to the resistor R5. And output to the transistor Tr2 via the resistor R6. The reference voltage is input from the variable resistor VR. A + 5V power supply is supplied to a circuit in which a variable resistor VR and a Zener diode ZD connected in parallel, and a resistor R1 and a capacitor C1 connected in parallel are connected in series.
[0039]
The emitter of the transistor Tr1 is supplied with + 5V power, the resistor R2 is connected to the base, the resistor R4 is connected between the emitter and the base, the collector is connected to the output of the IC1 through the resistor R5, and the resistor The transistor Tr2 is connected to the base via R6. A resistor R3 is connected between the + 5V power supply and the output of IC1.
[0040]
The emitter of the transistor Tr2 is supplied with + 5V power via resistors R7 to R9 connected in parallel, the base is connected to the resistor R6, and the collector is connected to the comparison element 4 and the resistor R10 of the bridge circuit 6.
[0041]
Further, as shown in FIG. 1, the CPU 11 includes a pulse generation unit 12, a data sampling unit 13 as a sampling unit, and a gas identification unit 15 as a gas identification unit. The pulse generator 12 generates a pulse drive signal for driving the heater 2, and outputs the generated pulse drive signal to the transistor Tr1 via the resistor R2.
[0042]
As shown in FIG. 3, the pulse drive signal is a signal that repeats on / off at a cycle of 1 second. The on period is 100 ms and the off period is 990 ms. This pulse drive signal is output to the transistor Tr1.
[0043]
The transistor Tr1 is turned on / off by a pulse drive signal. The transistor Tr2 is turned on when the transistor Tr1 is turned on to drive the heater 2 on, and is turned off when the transistor Tr1 is turned off to drive the heater 2 off.
[0044]
Therefore, as shown in FIG. 3, the CPU 11 turns the gas sensor 1 off by the pulse drive signal to lower the temperature (RT.degree. C. is maintained only for 990 ms), and turns the gas sensor 1 on to drive the high temperature ( 400 ° C. is maintained for 100 ms only).
[0045]
The transistor Tr2 and the resistors R7 to R9 constitute a heater driving unit that drives the heater 2 inside the gas sensor 1. The heater driving unit and the pulse generating unit 12 described above constitute a pulse driving unit.
[0046]
The data sampling unit 13 includes a first gas detection point DP1 (black circle in FIG. 3) when 50 ms has elapsed from when the sensor temperature reaches 400 ° C. (when the pulse drive signal is turned on), and a second gas when 75 ms has elapsed. The sensor output value is sampled from the sensor element 3 of the gas sensor 1 at each detection point of the third gas detection point DP3 when the gas detection point DP2, 100 ms has elapsed.
[0047]
The gas identification unit 15 detects that the sensor output value at the first gas detection point DP1 exceeds the sensor output value at the second gas detection point DP2, and the sensor output value at the second gas detection point DP2 is the sensor at the third gas detection point DP3. If the output value is exceeded, it is determined that the gas to be identified is a gas generated in the event of a fire.
[0048]
In addition, the gas identification unit 15 determines that the sensor output value at the first gas detection point DP1 is less than the sensor output value at the second gas detection point DP2, and the sensor output value at the second gas detection point DP2 is the third gas detection point DP3. If it is less than the sensor output value at, it is determined that the gas to be identified is a gas generated during a non-fire.
[0049]
The CPU 11 is connected to an LED 21a that is lit to identify a non-fire gas such as carbon monoxide and methane, and an LED 21b that is lit to identify a fire gas such as acetic acid generated in the event of a fire. . The speaker 19 informs by voice that the gas is a non-fire gas or a fire gas. The speaker 19, the LED 21a, and the LED 21b constitute notification means.
[0050]
Next, prior to the description of the operation of the gas detector of the embodiment configured as described above, the reason why the gas detector of the embodiment employs the pulse drive system as shown in FIG. This will be described with reference to FIG.
[0051]
First, gas generated when the timber was fired, that is, various gases generated in the event of a timber fire were analyzed. FIG. 4 shows the gas analysis results when the timber is fired. The inorganic gas was measured by a gas chromatography method, and the low boiling point compound and the high boiling point compound were measured by a gas chromatography method and a mass spectrometry method. Quantitative analysis of formaldehyde and acetaldehyde was measured by liquid chromatography, and quantitative analysis of acetic acid and formic acid was measured by ion chromatography.
[0052]
As can be seen from FIG. 4, carbon monoxide (gas concentration 1120 ppm) and acetic acid (gas concentration 840 ppm) were detected as the main components of various gases generated during the fire of timber.
[0053]
Next, various gas sensitivity response characteristics of the gas sensor 1 when the gas sensor 1 of the embodiment is operated by the pulse drive system as shown in FIG. 3 are shown in FIGS. FIG. 5 shows the acetic acid gas sensitivity response characteristic of the gas sensor 1. 5A shows sensor outputs (mV) at 0, 50 ms, 75 ms, and 100 ms at respective concentrations of 100 ppm, 500 ppm, and 1000 ppm in the high temperature region of the gas sensor 1, and FIG. The result of having plotted the sensor output of (a) is shown. As can be seen from FIG. 5, the sensor output at 50 ms shows the largest value, and the sensor output decreases in the order of 50 ms, 75 ms, and 100 ms.
[0054]
FIG. 6 shows the carbon monoxide gas sensitivity response characteristics of the gas sensor 1. As can be seen from FIG. 6, the sensor outputs at 50 ms, 75 ms, and 100 ms show almost the same value. FIG. 7 shows sensitivity response characteristics when acetic acid gas and carbon monoxide of the gas sensor 1 are combined. As can be seen from FIG. 7, the sensitivity response characteristic at this time is substantially the same as the acetic acid gas sensitivity response characteristic shown in FIG. 5, and the sensor output at 50 ms is the largest value.
[0055]
FIG. 8 shows the methane gas sensitivity response characteristic of the gas sensor 1. As can be seen from FIG. 8, the sensor output increases in the order of 50 ms, 75 ms, and 100 ms, and the sensor output at 100 ms shows the largest value. FIG. 9 shows the isobutane gas sensitivity response characteristic of the gas sensor 1. As can be seen from FIG. 9, the sensor outputs at 50 ms, 75 ms, and 100 ms show almost the same value.
[0056]
From the above, it was found that there is a great difference between the transient characteristics for carbon monoxide and methane and the transient characteristics for acetic acid and carbon monoxide + acetic acid. One possible reason for this difference is that acetic acid and the like have higher oxidation activity in the low temperature range.
[0057]
For this reason, the gas sensor 1 is driven by a pulse driving method as shown in FIG. 3, and the sensor output values are sampled at a plurality of detection points of 50 ms, 75 ms, and 100 ms from the time when the pulse driving signal is turned on (at the start of the high temperature region). Based on the sensor outputs at the plurality of detected points, it is possible to distinguish the gas generated in the event of a fire from other gases.
[0058]
Next, an operation of the gas detection device of the embodiment configured as described above, that is, a gas detection method will be described with reference to a timing chart shown in FIG. 3 and a flowchart shown in FIG.
[0059]
First, the pulse generator 12 generates a pulse drive signal as shown in FIG. 3 (step S101), and this pulse drive signal is applied to the transistor Tr1 via the resistor R2. The transistor Tr1 is turned off when the pulse drive signal is off. At this time, since the transistor Tr2 is also turned off, no current flows through the bridge circuit 6. For this reason, the heater 2 becomes low temperature.
[0060]
On the other hand, when the pulse drive signal is on, the transistor Tr1 is on. At this time, since the transistor Tr2 is also turned on, a current flows through the heater 2 of the bridge circuit 6 and the heater 2 is heated. For this reason, the heater 2 becomes high temperature.
[0061]
That is, the heater 2 is turned on / off by the pulse drive signal, and as shown in FIG. 3, the gas sensor 1 is cooled to a low temperature (RT.degree. C. is maintained for 990 ms) by the off drive and is heated to a high temperature (400.degree. Is maintained for 100 ms) (step S103).
[0062]
Next, the data sampling unit 13 outputs the sensor output value from the sensor element 3 of the gas sensor 1 at the first gas detection point DP1 (black circle in FIG. 3) when 50 ms has elapsed since the sensor temperature reached 400 ° C. And the sampled sensor output value is A / D converted by an analog / digital converter (A / D) (not shown) to obtain a voltage value V1 (step S105).
[0063]
Furthermore, the data sampling unit 13 samples the sensor output value from the sensor element 3 of the gas sensor 1 at the second gas detection point DP2 when 75 ms has elapsed since the sensor temperature reached 400 ° C., and the sampled sensor output value Is A / D converted by A / D to obtain a voltage value V2 (step S107).
[0064]
Finally, the data sampling unit 13 samples the sensor output value from the sensor element 3 of the gas sensor 1 at the third gas detection point DP3 when 100 ms has elapsed since the sensor temperature reached 400 ° C., and the sampled sensor output The voltage value V3 is obtained by A / D converting the value by A / D (step S109).
[0065]
Next, the gas identification unit 15 determines whether or not the voltage value V1 at the first gas detection point DP1 exceeds the voltage value V2 at the second gas detection point DP2 (step S111), and the voltage value V1 is a voltage value. If it exceeds V2, it is determined whether or not the voltage value V2 at the second gas detection point DP2 exceeds the voltage value V3 at the third gas detection point DP3 (step S113).
[0066]
When the voltage value V2 exceeds the voltage value V3, that is, when the expression (1) is satisfied, the identification target gas is determined to be a gas such as acetic acid generated at the time of a fire (step S115).
[0067]
V1>V2> V3 (1)
In this case, since the CPU 11 turns on the LED 21b, it can be easily identified that the gas to be identified is a gas such as acetic acid generated during a fire. The speaker 19 can also notify that the gas to be identified is a fire gas.
[0068]
On the other hand, in step S111, the voltage value V1 at the first gas detection point DP1 is less than the voltage value V2 at the second gas detection point DP2, and in step S113, the voltage value at the second gas detection point DP2 is the third gas detection. When the voltage is less than the voltage value V3 at the point DP3, that is, when the equation (2) is satisfied, the gas identification unit 15 determines that the identification target gas is a gas generated at the time of non-fire (step S117).
[0069]
V1 <V2 <V3 (2)
In this case, since the CPU 11 turns on the LED 21a, it can be easily identified that the gas to be identified is a gas such as carbon monoxide or methane generated during a non-fire. The speaker 19 can also notify that the identification target gas is a non-fire gas.
[0070]
As described above, according to the gas detection device of the embodiment, the gas sensor 1 is pulse-driven as shown in FIG. It is possible to easily distinguish the gas from other gases such as carbon monoxide gas and methane generated when the city gas leaks.
[0071]
In addition, since the fact is notified by the speaker 19 and the LEDs 21a and 21b, the type of gas can be easily identified, and the safety can be improved.
[0072]
In addition, it is necessary to provide a fire sensor or the like because one gas sensor 1 can easily distinguish between gases such as acetic acid gas generated during a fire of wood and other gases such as carbon monoxide gas and methane. Thus, an inexpensive gas detection device can be provided.
[0074]
【The invention's effect】
According to the gas detection device of the first aspect of the invention and the gas detection method of the fourth aspect of the invention, the pulse combustion signal is generated, and the pulse drive signal is applied to the heater to drive the catalytic combustion type gas sensor on / off. The sensor output values detected by the sensor elements are sampled at a plurality of gas detection points during the ON drive period of the catalytic combustion type gas sensor, and are sampled at the plurality of gas detection points during the ON drive period of the contact combustion type gas sensor. In addition, it distinguishes whether the gas is generated in the event of a fire or non-fire based on the changes in the sensor output values. Gas such as methane generated when city gas leaks can be easily identified. Further, the sensor output value at the first gas detection point exceeds the sensor output value at the second gas detection point after the first gas detection point time , and the sensor output value at the second gas detection point is after the second gas detection point time. When the sensor output value at the third gas detection point is exceeded , the gas identification means can determine that the gas is a gas generated at the time of the fire, and the sensor output value at the first gas detection point is the first gas detection point time. If the sensor output value at the later second gas detection point is less than the sensor output value at the second gas detection point, and the sensor output value at the third gas detection point is less than the sensor output value at the third gas detection point , Can be judged.
[0077]
According to the gas detection device of the second aspect of the invention and the gas detection method of the fifth aspect of the invention, the first gas detection point is set at a substantially middle point of the on-drive period, and the third gas detection point is on-drive. Since the second gas detection point is set at a substantially middle point between the first gas detection point and the third gas detection point, the sensor output value of the first gas detection point is set. A change in sensor output values at the second gas detection point and the third gas detection point can be easily understood.
[0078]
According to the gas detection device of the invention of claim 3 and the gas detection method of the invention of claim 6 , since the identification result of the type of gas is notified, the type of gas generated can be easily identified. Safety can be improved.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram of a gas detection device according to an embodiment of the present invention.
FIG. 2 is a detailed structural diagram of a gas sensor in the gas detection device of the embodiment.
FIG. 3 is a timing chart of the temperature of the gas sensor in the gas detection device of the embodiment.
FIG. 4 is a diagram showing a gas analysis result when timber is fired.
FIG. 5 is a diagram showing an acetic acid gas sensitivity response characteristic of a gas sensor.
FIG. 6 is a graph showing a carbon monoxide gas sensitivity response characteristic of a gas sensor.
FIG. 7 is a graph showing sensitivity response characteristics when acetic acid gas and carbon monoxide of a gas sensor are combined.
FIG. 8 is a diagram showing methane gas sensitivity response characteristics of a gas sensor.
FIG. 9 is a graph showing an isobutane gas sensitivity response characteristic of a gas sensor.
FIG. 10 is a flowchart for explaining a gas detection method realized by the gas detection device of the embodiment;
FIG. 11 is a diagram showing gas sensitivity characteristics of a semiconductor gas sensor using a conventional catalyst.
FIG. 12 is a timing chart of the temperature of the gas sensor in the conventional gas detection device.
FIG. 13 is a configuration block diagram of a conventional gas leak detection device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Gas sensor 2 Heater 3 Sensor element 4 Comparison element 5 Heater drive part 6 Bridge circuit 11 CPU
12 Pulse generation part 13 Data sampling part 15 Gas identification part 19 Speaker 21a, 21b LED
31 Sensor base 33 Substrate 35 Diaphragm 37 Oxide film 39 Si ₃ N ₄ film 41 Electrode 43 Gold wire 45 Catalyst layer Tr1 Transistor IC1 Integrated circuit DP1 First gas detection point DP2 Second gas detection point DP3 Third gas detection point

Claims (6)

A contact combustion type gas sensor provided with a heater and a sensor element for detecting gas;
Pulse driving means for generating a pulse driving signal and applying the pulse driving signal to the heater to drive the catalytic combustion gas sensor on / off;
Sampling means for sampling sensor output values detected by the sensor elements at a plurality of gas detection points during the on-drive period of the catalytic combustion gas sensor;
Whether the gas is generated at the time of a fire or a gas generated at the time of a non-fire based on a change in a plurality of sensor output values sampled at a plurality of gas detection points during the on-drive period of the catalytic combustion gas sensor by the sampling means Gas identifying means for identifying
With
The gas identification means has a sensor output value at a first gas detection point that exceeds a sensor output value at a second gas detection point after the first gas detection point time , and the sensor output value at the second gas detection point is a second gas. If the sensor output value at the third gas detection point after the detection point time is exceeded, the gas is determined to be a gas generated at the time of a fire, and the sensor output value at the first gas detection point is the first gas detection point time. If the sensor output value at the subsequent second gas detection point is less than the sensor output value at the second gas detection point and less than the sensor output value at the third gas detection point , the gas is generated during a non-fire. It is determined that the gas detection device. The first gas detection point is set to a substantially middle point of the on-drive period, the third gas detection point is set to a substantially end point of the on-drive period , and the second gas detection point is the first gas detection point. The gas detection device according to claim 1, wherein the gas detection device is set at a substantially middle point between the gas detection point and the third gas detection point .   The gas detection apparatus according to claim 1, further comprising an informing unit that informs the identification result of the type of gas identified by the gas identifying unit. A pulse driving step of generating a pulse driving signal and applying the pulse driving signal to a heater provided in the catalytic combustion gas sensor to drive the catalytic combustion gas sensor on / off;
A sampling step of sampling sensor output values detected by sensor elements provided in the catalytic combustion gas sensor at a plurality of gas detection points during the on-drive period of the catalytic combustion gas sensor;
A gas for identifying whether the gas is a gas generated at the time of a fire or a gas generated at the time of a non-fire based on changes in a plurality of sensor output values sampled at a plurality of gas detection points during the on-drive period of the catalytic combustion gas sensor An identification step;
Including
In the gas identification step, the sensor output value at the first gas detection point exceeds the sensor output value at the second gas detection point after the first gas detection point time , and the sensor output value at the second gas detection point is the second gas. If the sensor output value at the third gas detection point after the detection point time is exceeded, the gas is determined to be a gas generated at the time of a fire, and the sensor output value at the first gas detection point is the first gas detection point time. If the sensor output value at the subsequent second gas detection point is less than the sensor output value at the second gas detection point and less than the sensor output value at the third gas detection point , the gas is generated during a non-fire. The gas detection method characterized by determining. The first gas detection point is set to a substantially middle point of the on-drive period, the third gas detection point is set to a substantially end point of the on-drive period , and the second gas detection point is the first gas detection point. The gas detection method according to claim 4, wherein the gas detection method is set at a substantially intermediate point between the gas detection point and the third gas detection point .   6. The gas detection method according to claim 4, further comprising a notifying step for notifying a result of identifying the type of gas identified in the gas identifying step.

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