JP2009168463A - Gas detection method and gas detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas detection device for utilizing effectively a fuel gas sensor and an incomplete combustion gas sensor, in a gas detection technology for discriminating and detecting fuel gas and incomplete combustion gas by using a methane gas sensor and the incomplete combustion gas sensor. <P>SOLUTION: This gas detection device includes the first detection control part 43a for acquiring a methane gas detection value at a timing when the methane gas sensor 1 reaches a state suitable for methane gas detection, and allowing a fuel gas detection value acquisition part 44a to obtain a gas detection value as a CO gas detection value at a timing when reaching a state suitable for CO gas detection, when a CO gas sensor 2 is out of order; and the second detection control part 43b for acquiring a CO gas detection value at a timing when the CO gas sensor reaches a state suitable for CO gas detection, and allowing an incomplete combustion gas detection value acquisition part 42a to obtain a gas detection value as a methane gas detection value at a timing when reaching a state suitable for methane gas detection, when the methane gas sensor is out of order. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a gas detection method using a fuel gas sensor capable of detecting incomplete combustion gas in a specific temperature range, an incomplete combustion gas sensor capable of detecting fuel gas in a specific temperature range, and gas detection for implementing this method. Relates to the device.

  One of the conventional technologies related to this type of gas detection is a low heat capacity hot-wire semiconductor gas sensor having an oxide semiconductor mainly made of tin oxide as a sensor sensitive part. This sensor is provided with a sensor sensitive part carrying a valence-controlled tin oxide SnO2 as a main component and supporting a combustion-inactive, heat-resistant tetravalent metal oxide. Further, this sensor alternates the temperature of the sensor sensitive portion between a fuel gas detection temperature for detecting fuel gas and an incomplete combustion gas detection temperature for detecting incomplete combustion gas different from the fuel gas detection temperature. Switching means for switching to is provided. Thereby, the fuel gas which has methane as a main component, and the incomplete combustion gas which has carbon monoxide as a main component are discriminated and detected (for example, refer patent document 1).

Japanese Unexamined Patent Publication No. 7-174725 (paragraph numbers 0005-0007, 0018, FIG. 2)

  The gas detection device according to Patent Document 1 detects the incomplete combustion gas by detecting the fuel gas in a temperature range suitable for detecting the fuel gas by repeatedly changing the temperature of the sensor sensitive part between the low temperature and the high temperature. Incomplete combustion gas is detected in a temperature range suitable for As a result, it is possible to identify and detect the fuel gas and the incomplete combustion gas with one gas sensor. However, since one gas sensor, that is, one gas sensitive part is configured to distinguish and detect fuel gas and incomplete combustion gas, the detection ability of the gas sensitive part is optimized for each gas. It is difficult to do.

In order to solve this problem, it is conceivable to discriminate and detect the fuel gas and the incomplete combustion by a gas detection device including a fuel gas sensor and an incomplete combustion gas sensor. However, simply providing two gas sensors, that is, a fuel gas sensor and an incomplete combustion gas sensor, has an additional advantage other than the advantage that it can simply detect and detect the fuel gas and the incomplete combustion because of an economic problem. The practical application is difficult.
In view of the above situation, an object of the present invention is to effectively use a fuel gas sensor and an incomplete combustion gas sensor in a gas detection technique for identifying and detecting fuel gas and incomplete combustion gas using a fuel gas sensor and an incomplete combustion gas sensor. It is to provide gas detection technology that can be used in the future.

  In order to solve the above problem, a gas detection method according to the present invention using a fuel gas sensor capable of detecting incomplete combustion gas in a specific temperature range and an incomplete combustion gas sensor capable of detecting fuel gas in a specific temperature range, A first heating current applying step for applying a heating current for bringing the fuel gas sensor into a state suitable for detection of fuel gas; and a gas detection value by the fuel gas sensor at a timing when the fuel gas sensor reaches a state suitable for detection of the fuel gas. A step of obtaining a detected value of fuel gas; a second heating current applying step of applying a heating current for making the incomplete combustion gas sensor suitable for detection of incomplete combustion gas; and detection of the incomplete combustion gas Acquiring a gas detection value by the incomplete combustion gas sensor as an incomplete combustion gas detection value at a timing to reach a state suitable for Determining a failure of the fuel gas sensor and the incomplete combustion gas sensor, and if the fuel gas sensor is determined to be in failure, the failure is detected at a timing when the incomplete combustion gas sensor reaches a state suitable for detection of the fuel gas. A step of acquiring a gas detection value by a complete combustion gas sensor as a fuel gas detection value; and when the incomplete combustion gas sensor is determined to be in failure, the fuel gas sensor reaches a state suitable for detection of the incomplete combustion gas. And obtaining a gas detection value by the fuel gas sensor as an incomplete combustion gas detection value at a timing.

  In this characteristic configuration, even when one of the gas sensors fails, both the fuel gas and the incomplete combustion gas can be identified and detected. In other words, when the failure of one of the fuel gas sensor and the incomplete combustion gas sensor is determined, the gas sensor that is not in failure detects the type of gas that should be detected by the gas sensor that is determined to be defective. By doing so, the state which can detect both fuel gas and incomplete combustion gas is maintained. This is because the incomplete combustion gas sensor used here can be transformed into a state suitable for detection of fuel gas, and the gas detection value acquired at the timing of reaching that state is used as the fuel gas detection value. It is possible that the fuel gas sensor used here can be transformed into a state suitable for detection of incomplete combustion gas, and the gas detection value acquired at the timing of reaching that state is the incomplete combustion gas detection value. Based on being available as.

  In order to solve the above problems, a gas detection device according to the present invention using a fuel gas sensor capable of detecting incomplete combustion gas in a specific temperature range and an incomplete combustion gas sensor capable of detecting fuel gas in a specific temperature range, A first heating current applying unit that applies a heating current for making the fuel gas sensor suitable for detection of fuel gas; and a gas detection value by the fuel gas sensor at a timing when the fuel gas sensor reaches a state suitable for detection of the fuel gas. A fuel gas detection value acquisition unit configured to acquire a fuel gas detection value; a second heating current application unit configured to apply a heating current for making the incomplete combustion gas sensor suitable for detection of incomplete combustion gas; The incomplete combustion gas detection that acquires the gas detection value by the incomplete combustion gas sensor as the incomplete combustion gas detection value at a timing when it reaches a state suitable for detection of the complete combustion gas. A value acquisition unit, a sensor failure determination unit that determines failure of the fuel gas sensor and the incomplete combustion gas sensor, and a fuel failure sensor that determines the failure of the incomplete combustion gas when the incomplete combustion gas sensor is determined to have failed. A first detection control unit that causes the fuel gas detection value acquisition unit to acquire a gas detection value detected by the fuel gas sensor as an incomplete combustion gas detection value at a timing that reaches a state suitable for detection; In this case, at the timing when the incomplete combustion gas sensor reaches a state suitable for detection of the fuel gas, the incomplete combustion gas detection value acquisition unit acquires the gas detection value by the incomplete combustion gas sensor as the fuel gas detection value. It consists of a 2nd detection control part. Of course, this gas detection device can also obtain all the effects described in the gas detection method.

  A hot-wire semiconductor incomplete combustion gas sensor in which a heating current is applied for purge heating at about 500 ° C. prior to detection of incomplete combustion gas such as carbon monoxide is known. The timing at which the temperature is raised due to the purge heating is suitable for detecting a fuel gas such as methane in the incomplete combustion gas sensor. Accordingly, in one preferred embodiment of the present invention, the incomplete combustion gas sensor is a hot-wire semiconductor type, and the timing at which the incomplete combustion gas sensor reaches a state suitable for detection of the fuel gas is the first time. It is set at the end of application of the heating current in the heating current application unit (here, the concept of the vicinity of the end of application is also included at the end of application).

  In addition, a hot-wire semiconductor fuel gas sensor that raises the temperature of the gas sensitive part to a temperature range of about 500 ° C. in order to bring the gas sensitive part into an appropriate detection state of fuel gas such as methane gas through the application of a heating current is known. Since the temperature range of about 200 to 300 ° C. suitable for detecting incomplete combustion gas such as carbon monoxide has passed until the temperature of the gas sensitive part rises to about 500 ° C., this fuel gas sensor is incomplete. It can also be used for combustion gas detection. Therefore, in one preferred embodiment of the present invention, the fuel gas sensor is a hot-wire semiconductor type, and the timing at which the fuel gas sensor reaches a state suitable for detection of the incomplete combustion gas is determined by the second heating. Immediately after application of the heating current in the current application unit, for example, about 1 second after application.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, the gas detection device discriminates and detects the fuel gas mainly composed of methane and the incomplete combustion gas that is generated by incomplete combustion and is mainly carbon monoxide (which may include hydrogen gas). Is configured to do. FIG. 1 shows a functional block diagram of the gas detection device. In order to detect methane gas and carbon monoxide (hereinafter referred to as CO gas), the methane gas sensor 1, the CO gas sensor 2, the first measurement processing system for processing the signal value by the methane gas sensor 1, and the gas signal value by the CO gas sensor 2 And a second measurement processing system.

  The methane gas sensor 1 in this embodiment is a hot-wire semiconductor methane gas sensor. As shown in FIG. 2, the noble metal wire 11 is covered with a metal oxide semiconductor layer 12 in a spherical shape. It has a structure in which a coarse grain layer 13 is formed on the outer surface. A platinum wire coil is used as the noble metal wire 11. As a metal oxide semiconductor, tin oxide obtained by drying a colloidal white precipitate formed by hydrolyzing a tin salt is used. After this tin oxide is crushed and made into fine particles, it is made into a paste form with a dispersion medium of water or an organic solvent and applied to the platinum wire coil 1 in a spherical shape. A coarse particle layer 13 is formed by attaching coarse particles containing at least one of a metal and a metal oxide to the tin oxide (metal oxide semiconductor layer 12).

  The methane gas sensor 1 operates in a pattern that repeats between room temperature and high temperature (about 500 ° C.), and methane gas is appropriately detected at the high temperature. The methane gas sensor 1 is repeatedly subjected to a thermal load between room temperature and high temperature, but the coarse particle layer 13 covers the surface of the metal oxide semiconductor layer 12 in a uniform state, and is a metal oxide that is a gas sensitive part. Since the semiconductor layer 12 and the coarse particle layer 13 are respectively integrated, the coarse particle layer 3 is not easily cracked or peeled off due to repeated heat loads.

  The CO gas sensor 2 in this embodiment is a hot-wire semiconductor CO gas sensor, and as shown in FIG. 3, indium oxide is provided at a diameter of 0.5 mm so as to cover a platinum wire coil 21 having a diameter of about 30 μm as a noble metal wire. In addition, the gas-sensitive portion 22 is formed by baking the indium oxide at 600 ° C. for 1 hour, and 0.05 mol% of palladium is further added to the gas-sensitive portion 22. The CO gas sensor 2 is a room temperature operation type capable of optimally detecting CO gas at room temperature, but is heated to a high temperature (about 500 ° C.) every time gas detection is completed for purging.

  As described above, since the methane gas sensor 1 is configured to be extremely small and the thermal control of the sensor is easy, the temperature of the sensor can be easily raised to a high temperature range (around 500 ° C.) suitable for methane gas detection. Because of the fast methane adsorption and desorption, the methane gas can be detected immediately (within a few seconds) after the sensor temperature reaches the high temperature range. Similarly, the CO gas sensor 2 is also configured to be extremely small, and the thermal equilibrium at the time of temperature rise / fall is very fast and the adsorption / desorption equilibrium is also fast, so the detection of the CO gas is within 10 seconds after completion of the purge heating in the low temperature range (room temperature). The CO gas can be detected.

  The relationship between the sensor temperature and sensor sensitivity (change in resistance value) of the methane gas sensor 1 used here is shown in the graph of FIG. From FIG. 4, the methane gas sensor 1 can detect CO gas with a selectivity in the temperature range near 200 ° C., and can detect with methane gas selectivity in the temperature range of about 500 ° C. or higher. I understand that. Furthermore, the relationship between the sensor temperature and sensor sensitivity (resistance value change) of the CO gas sensor 2 used here is shown in the graph of FIG. From FIG. 5, this CO gas sensor 2 can detect CO gas selectivity in the temperature range near room temperature, and can detect methane gas selectivity in the temperature range near 400 ° C. Can understand.

  The graph of FIG. 6 shows a relationship in which the sensor sensitivity increases as the methane gas concentration increases in the methane gas detection temperature range of the methane gas sensor 1 (for CO gas, it is substantially regardless of the concentration increase). Sensor sensitivity does not change. From this figure, it can be understood that the methane gas sensor 1 can properly detect the methane gas concentration. Furthermore, the graph of FIG. 7 shows a relationship in which the sensor sensitivity increases as the CO gas concentration increases in the CO gas detection temperature range of the CO gas sensor 2 (the concentration increases for methane gas). Regardless, sensor sensitivity does not change substantially). From this figure, it can be understood that the CO gas sensor 2 can properly detect the CO gas concentration.

  Further, the graph of FIG. 8 shows a relationship in which the sensor sensitivity increases as the gas concentration of the CO gas in the CO gas detection temperature range of the methane gas sensor 1 increases (for methane gas, the concentration thereof). The sensor sensitivity does not change substantially regardless of the rise). From this figure, it can be understood that the methane gas sensor 1 can properly detect the CO gas concentration in a specific temperature range. Furthermore, the graph of FIG. 9 shows a relationship in which the sensor sensitivity increases as the methane gas concentration increases in the methane gas detection temperature range of the CO gas sensor 2 (the concentration increases for CO gas). Regardless of the sensor sensitivity does not change substantially). From this figure, it can be understood that the CO gas sensor 2 can properly detect the methane gas concentration in a specific temperature range.

  Further, a gas detection apparatus using the methane gas sensor 1 and the CO gas sensor 2 as described above will be described in detail with reference to FIG. The structures of the first detection circuit unit 31 connected to the methane gas sensor 1 and the second detection circuit unit 32 connected to the CO gas sensor 2 are substantially the same. That is, the platinum wire coil 11 or 21 is incorporated as one resistance in the Wheatstone bridge, and a change in the combined resistance value is detected as a gas detection value to detect methane gas or CO gas.

  A first heating current application unit that applies a pulsed heating current to the platinum wire coil 11 with respect to the methane gas sensor 1 to bring the methane gas sensor 1 into a high temperature range (about 500 ° C.) that is suitable for methane gas detection. 33 is provided. The first heating current application unit 33 is connected to the first detection circuit unit 31, and sends a heating current application pulse to the platinum wire coil 11 of the methane gas sensor 1 using the circuit of the first detection circuit unit 31. Similarly, a second heating current application unit 34 is provided to raise the temperature to a high temperature range (about 500 ° C.) suitable for purging by applying a pulsed heating current to the platinum wire coil 21 with respect to the CO gas sensor 2. It has been. The second heating current application unit 34 is connected to the second detection circuit unit 32, and sends a heating current application pulse to the platinum wire coil 11 of the methane gas sensor 1 using the circuit of the second detection circuit unit 32.

  In the controller 4 of this gas detector, a first measurement control system for processing a signal value from the methane gas sensor 1, a second measurement control system for processing a signal value from the CO gas sensor 2, and a common measurement evaluation system are incorporated. ing. When the controller 4 confirms detection of methane gas or CO gas exceeding the danger level, an alarm is notified through a device such as the buzzer 5 or the lamp 6.

  The first measurement control system of the controller 4 includes a heating control unit 41a that gives a control signal for sending a heating current application pulse to the methane gas sensor 1 at a predetermined repetition frequency to the first heating current application unit 33, and a methane gas A fuel gas detection value acquisition unit 42a that acquires a gas detection value from the methane gas sensor 1 in a state suitable for detection from the first detection circuit unit 31 as a methane gas detection value, and a methane gas sensor for the fuel gas detection value acquisition unit 42a A first detection control unit 43a for instructing the timing when 1 reaches a state suitable for detection of methane gas, and a fuel gas sensor for evaluating a gas detection value from the methane gas sensor 1 to determine a failure such as disconnection of the methane gas sensor 1 A failure determination unit 44a is included.

  In FIG. 10, the heating current application pulse that the first heating current application unit 33 sends to the methane gas sensor 1, the temperature change of the methane gas sensor 1 due to this heating current application pulse, the methane gas to the fuel gas detection value acquisition unit 42 a The timing chart which shows the relationship with the methane gas detection pulse which the 1st detection control part 43a sends out in order to instruct | indicate the timing which acquires the gas detection value by the sensor 1 as a methane gas detection value is shown.

  As is clear from this timing chart, the methane gas sensor 1 is heated from room temperature to about 500 ° C. each time by a heating current application pulse delivered at a predetermined time interval (for example, about 10 seconds), and the methane gas sensor 1 is about 500 ° C. The methane gas detection pulse is sent out at a timing when the temperature is raised to a short time, that is, between a short time before the falling point of the heating current application pulse and almost between the falling points, and a methane gas detection value is acquired.

  The second measurement control system of the controller 4 includes a heating control unit 41b that gives a control signal for sending a heating current application pulse for purging to the CO gas sensor 2 at a predetermined repetition frequency to the second heating current application unit 34; The incomplete combustion gas detection value acquisition unit 42b acquires the gas detection value from the methane gas sensor 1 in a state suitable for CO gas detection as the CO gas detection value from the second detection circuit unit 32, and the fuel gas detection value acquisition unit A second detection control unit 43b for instructing the timing when the CO gas sensor 2 has reached a state suitable for CO gas detection with respect to 42b, a gas detection value from the CO gas sensor 2, etc., and a disconnection of the CO gas sensor 2 etc. An incomplete combustion gas sensor failure determination unit 44b for determining the failure of the engine is included.

  FIG. 11 shows a heating current application pulse that the second heating current application unit 34 sends to the methane gas sensor 1 for the purpose of purging, a temperature change of the methane gas sensor 1 due to this heating current application pulse, and an incomplete combustion gas detection value acquisition unit. A timing chart showing the relationship with the CO gas detection pulse sent out by the second detection control unit 43b in order to instruct the timing of acquiring the gas detection value by the CO gas sensor 2 as the CO gas detection value for 42b is shown. .

  As is apparent from this timing chart, the CO gas sensor 2 is heated from normal temperature to about 500 ° C. each time by a heating current application pulse delivered at a predetermined time interval (for example, about 10 seconds) and purged. The CO gas detection pulse is sent out at the timing when 2 is returned to room temperature, that is, at the substantially rising point of the heating current application pulse, and the CO gas detection value is acquired.

  In the gas detection device according to the present invention, when a failure of one of the methane gas sensor 1 as a fuel gas sensor and the CO gas sensor 2 as an incomplete combustion gas sensor is determined, the gas sensor determined as a failure is detected. It can be set so that the type of gas to be detected is detected by the non-failing gas sensor. That is, if the incomplete combustion gas sensor failure determination unit 44b determines that the CO gas sensor 2 has failed, the first detection control unit 43a detects that the methane gas sensor 1 reaches a state suitable for CO gas detection. 1 is caused to be acquired by the fuel gas detection value acquisition unit 42a as a CO gas detection value. In this embodiment, the timing at which the methane gas sensor 1 reaches a state suitable for CO gas detection is about 1 second after the rising point of the heating current application pulse sent to the methane gas sensor 1, as shown in FIG. It is time of. At this time, the temperature of the methane gas sensor 1 is about 250 ° C., and the CO gas can be detected. As is apparent from FIG. 12, at each pulse repetition interval of the heating current application pulse, the first detection control unit 43a sends the CO gas detection pulse to the fuel gas detection value acquisition unit 42a to acquire the CO gas detection value, A methane gas detection value is acquired by sending a methane gas detection pulse to the fuel gas detection value acquisition unit 42a.

  When the fuel gas sensor failure determination unit 44a determines that the methane gas sensor 1 has failed, the second detection control unit 43b detects the gas using the CO gas sensor 2 at a timing when the CO gas sensor 2 reaches a state suitable for detection of methane gas. The value is acquired by the incomplete combustion gas detection value acquisition unit 42b as the methane gas detection value. In this embodiment, the timing at which the CO gas sensor 2 reaches a state suitable for detection of methane gas is when the temperature of the CO gas sensor 2 is around 400 ° C. as can be understood from FIG. As shown, the heating current application pulse sent to the CO gas sensor 2 is slightly before the falling point and almost between the falling points. At this time, the temperature of the CO gas sensor 2 is around 400 ° C., and the methane gas can be detected. As apparent from FIG. 13, at each pulse repetition interval of the heating current application pulse, the second detection control unit 43b sends the CO gas detection pulse to the incomplete combustion gas detection value acquisition unit 42b, thereby acquiring the CO gas detection value. The methane gas detection value is acquired by sending the methane gas detection pulse to the incomplete combustion gas detection value acquisition unit 42b.

  The measurement evaluation system of the controller 4 sequentially receives the methane gas detection value acquired by the fuel gas detection value acquisition unit 42a and the CO gas detection value acquired by the incomplete combustion gas detection value acquisition unit 42b at predetermined measurement intervals, A detection value evaluation unit 45 that determines the occurrence of dangerous levels of methane gas generation, CO gas generation, or fire by evaluating based on each determination condition, and methane gas generation alarm information or the like based on the determination result of the detection value evaluation unit 45 An alarm processing unit 46 that generates CO gas generation alarm information and fire occurrence alarm information and notifies the alarm through the buzzer 5 and the lamp 6 is included.

An example of gas detection control in the gas detection apparatus configured as described above will be described with reference to the flowcharts of FIGS. 14 and 15.
When the repeated detection intervals of methane gas detection and CO gas detection are different, first, it is checked which gas sensor is used for gas detection (# 01). This check can be determined based on an internal clock and a preset detection interval of each gas detection. When it is the timing of methane gas detection in the check of step # 01, the first heating current application pulse is applied to the methane gas sensor 1 (# 02). As can be understood from FIG. 12, the temperature of the methane gas sensor 1 is at a high temperature range suitable for methane gas detection (about about a time point between slightly before the falling point of the first heating current application pulse and almost between the falling points. 500 ° C.), it is checked whether it is slightly before the first heating current application pulse (# 03). When a time point just before the fall of the first heating current application pulse is detected (# 03 Yes branch), a methane gas detection pulse (signal) is sent to the fuel gas detection value acquisition unit 42a (# 04). Thereby, the fuel gas detection value acquisition part 42a acquires the gas detection value in the methane gas sensor 1 as a methane gas detection value via the 1st detection circuit part 31, and transfers it to the detection value evaluation part 45 (# 05). Further, the detection evaluation unit 45 evaluates the received methane gas detection value including the accumulated past detection values, if necessary (# 06).

  If it is the timing of CO gas detection in the check of step # 01, the second heating current application pulse is applied to the CO gas sensor 2 via the second heating current application unit 34 (# 07). At the same time or just before that, the CO gas detection pulse (signal) is sent to the incomplete combustion gas detection value acquisition unit 42a (# 08). Thereby, the incomplete combustion gas detection value acquisition part 42b acquires the gas detection value in the CO gas sensor 2 as a CO gas detection value via the 2nd detection circuit part 32, and transfers it to the detection value evaluation part 45 (# 09). . Furthermore, the detection evaluation unit 45 evaluates the received CO gas detection value, including the past detection values accumulated, if necessary (# 10).

  When the evaluation of the methane gas detection value (# 06) or the evaluation of the CO gas detection value (# 10) by the detection evaluation unit 45 is completed, it is determined whether or not the detection evaluation value of methane gas or CO gas is at the gas leak alarm level. (# 11). If it is the alarm level (# 11 Yes branch), after performing the alarm process (# 12), if it is not the alarm level (# 11 No branch), the process proceeds to the next failure determination process (# 14). In the failure determination processing, the fuel gas sensor failure determination unit 44a evaluates the gas detection value from the methane gas sensor 1 to determine failure such as disconnection of the methane gas sensor 1, and the incomplete combustion gas sensor failure determination unit 44b And a process of evaluating a gas detection value from the gas sensor 2 to determine a failure such as a disconnection of the CO gas sensor 2. In this failure determination process, if neither gas sensor failure is determined (# 14 No branch), the process returns to step # 01, and the steps so far are repeated. If a failure of one of the gas sensors is determined (# 14 Yes branch), the gas sensor determined to be defective is checked (# 13). When the CO gas sensor 2 is faulty, “1” is set in the fault flag, and when the methane gas sensor 1 is faulty, “2” is set in the fault flag, and the corresponding gas sensor is faulty. Informed (# 19). Thereafter, the process enters a recovery routine in which methane gas and CO gas are detected by a gas sensor that has not failed (# 20). If the methane gas sensor 1 and the CO gas sensor 2 are out of order, the operation of the gas detector is no longer possible, and a notification to that effect is given (# 18).

Next, the recovery routine will be described with reference to the flowchart of FIG.
Initially, a failure flag is checked to identify a malfunctioning gas sensor (# 21).
[In case of CO gas sensor failure]
When the failure flag is set to “1” and the CO gas sensor is considered to be in failure, the methane gas sensor 1 detects methane gas and CO gas.
First, the first heating current application pulse is applied to the methane gas sensor 1 (# 30). As can be understood from FIG. 12, immediately after the rise of the first heating current application pulse, about 1 second after the rise, the temperature of the methane gas sensor 1 reaches about 250 ° C., and is in a state suitable for detecting CO gas. For this reason, here, it waits until 1 second passes from the rise of the first heating current application pulse, and when 1 second passes (# 31 Yes branch), the CO gas detection pulse (signal) becomes the incomplete combustion gas detection value acquisition unit 42a. (# 32). Thereby, the fuel gas detection value acquisition part 42a acquires the gas detection value in the methane gas sensor 1 as a CO gas detection value via the 12th detection circuit part 31, and transfers it to the detection value evaluation part 45 (# 33). Subsequently, it is checked whether or not it is slightly before the fall of the first heating current application pulse (# 34). When a time point just before the fall of the first heating current application pulse is detected (# 34 Yes branch), a methane gas detection pulse (signal) is sent to the fuel gas detection value acquisition unit 42a (# 35). Thereby, the fuel gas detection value acquisition part 42a acquires the gas detection value in the methane gas sensor 1 as a methane gas detection value via the 1st detection circuit part 31, and transfers it to the detection value evaluation part 45 (# 36). The detection evaluation unit 45 evaluates the received methane gas detection value and the CO gas detection value, including the accumulated past detection values, if necessary (# 37), and whether or not the gas leakage alarm level is reached. Is determined (# 38). If it is the alarm level (# 38 Yes branch), after performing the alarm process (# 39), if it is not the alarm level (# 38 No branch), the failure determination process is entered (# 50). In this failure determination process, if failure of the methane gas sensor 1 is not determined (# 51 No branch), the process returns to step # 30 and the steps so far are repeated. However, if it is determined that the methane gas sensor 1 has failed (# 51 Yes branch), the methane gas sensor 1 and the CO gas sensor 2 have failed. Is performed (# 52).

[In case of failure of methane gas sensor]
When the failure flag is set to “2” and the methane gas sensor is considered to have failed, the CO gas sensor 2 detects methane gas and CO gas.
First, a second heating current application pulse is applied to the CO gas sensor 2 via the second heating current application unit 34 (# 40). Simultaneously or immediately before that, a CO gas detection pulse (signal) is sent to the incomplete combustion gas detection value acquisition unit 42a (# 42). Thereby, the incomplete combustion gas detection value acquisition part 42b acquires the gas detection value in the CO gas sensor 2 as a CO gas detection value via the 2nd detection circuit part 32, and transfers it to the detection value evaluation part 45 (# 43). . Subsequently, it is checked whether or not it is slightly before the fall of the second heating current application pulse (# 44). When a time point just before the fall of the second heating current application pulse is detected (# 44 Yes branch), a methane gas detection pulse (signal) is sent to the incomplete combustion gas detection value acquisition unit 42b (# 45). Thereby, the incomplete combustion gas detection value acquisition part 42b acquires the gas detection value in the CO gas sensor 2 as a methane gas detection value via the 2nd detection circuit part 32, and transfers it to the detection value evaluation part 45 (# 46). The detection evaluation unit 45 evaluates the received methane gas detection value and the CO gas detection value, including the accumulated past detection values, if necessary (# 37), and whether or not the gas leakage alarm level is reached. Is determined (# 48). If it is the alarm level (# 38 Yes branch), after performing the alarm process (# 39), if it is not the alarm level (# 38 No branch), the failure determination process is entered (# 60). In this failure determination process, if the failure of the CO gas sensor 2 is not determined (# 61 No branch), the process returns to step # 40 and the steps so far are repeated. However, if the failure of the CO gas sensor 2 is determined (# 61 Yes branch), it means that the methane gas sensor 1 and the CO gas sensor 2 are out of order. Is performed (# 62).

  In the description of the above-described embodiment, methane gas and CO gas are handled. However, since the methane gas sensor 1 and the CO gas sensor 2 described above show substantially the same behavior as the CO gas with respect to the hydrogen gas, it is possible to detect the hydrogen gas similarly to the CO gas. Such gas detection devices are also within the scope of the present invention.

  INDUSTRIAL APPLICABILITY The present invention can be used for a gas detection technique for detecting fuel gas and incomplete combustion gas using a fuel gas sensor and an incomplete combustion gas sensor.

Functional part lock figure which shows an example of the gas detection apparatus by this invention Schematic diagram showing an example of a methane gas sensor Schematic diagram showing an example of a CO gas sensor Graph showing the relationship between sensor temperature and sensor sensitivity of methane gas sensor Graph showing the relationship between sensor temperature and sensor sensitivity of CO gas sensor Graph showing the relationship between methane gas concentration and sensor sensitivity in the methane gas detection temperature range of the methane gas sensor Graph showing the relationship between CO gas concentration and sensor sensitivity in the CO gas detection temperature range of the CO gas sensor Graph showing the relationship between CO gas concentration and sensor sensitivity in the CO gas detection temperature range of a methane gas sensor Graph showing the relationship between methane gas concentration and sensor sensitivity in the methane gas detection temperature range of the CO gas sensor Timing chart explaining the relationship between the heating current application pulse sent to the methane gas sensor, the temperature change of the methane gas sensor at that time, and the methane gas detection pulse Timing chart explaining the relationship between the heating current application pulse to be sent to the CO gas sensor, the state of temperature change of the CO gas sensor at that time, and the CO gas detection pulse Timing chart explaining CO gas detection by methane gas sensor Timing chart explaining methane gas detection by CO gas sensor Flowchart showing an example of gas detection control in the gas detection device Flow chart showing recovery routine

Explanation of symbols

1: Methane gas sensor (fuel sensor)
2: CO gas sensor (fuel sensor)
31: 1st detection circuit part 32: 2nd detection circuit part 33: 1st heating current application part 34: 2nd heating current application part 41a: Heating control part 41b: Heating control part 42a: Fuel gas detection value acquisition part 42b: Incomplete combustion gas detection value acquisition unit 43a: first detection control unit 43b: second detection control unit 44a: fuel gas sensor failure determination unit 44b: incomplete combustion gas failure determination unit 45: detection value evaluation unit

Claims (4)

A gas detection method using a fuel gas sensor capable of detecting incomplete combustion gas in a specific temperature range and an incomplete combustion gas sensor capable of detecting fuel gas in a specific temperature range,
A first heating current applying step for applying a heating current for making the fuel gas sensor suitable for detection of fuel gas;
Acquiring a gas detection value by the fuel gas sensor as a fuel gas detection value at a timing when reaching a state suitable for detection of the fuel gas;
A second heating current applying step for applying a heating current for bringing the incomplete combustion gas sensor into a state suitable for detection of the incomplete combustion gas;
Obtaining a gas detection value by the incomplete combustion gas sensor as an incomplete combustion gas detection value at a timing when reaching a state suitable for detection of the incomplete combustion gas;
Determining a failure of the fuel gas sensor and the incomplete combustion gas sensor;
When it is determined that the fuel gas sensor has failed, a step of acquiring a gas detection value by the incomplete combustion gas sensor as a fuel gas detection value at a timing when the incomplete combustion gas sensor reaches a state suitable for detection of the fuel gas. When,
When it is determined that the incomplete combustion gas sensor has failed, the gas detection value obtained by the fuel gas sensor is acquired as the incomplete combustion gas detection value when the fuel gas sensor reaches a state suitable for detection of the incomplete combustion gas. And steps to
A gas detection method comprising: A gas detection device comprising a fuel gas sensor capable of detecting incomplete combustion gas in a specific temperature range and an incomplete combustion gas sensor capable of detecting fuel gas in a specific temperature range,
A first heating current application unit for applying a heating current for making the fuel gas sensor suitable for detection of fuel gas;
A fuel gas detection value acquisition unit that acquires a gas detection value obtained by the fuel gas sensor as a fuel gas detection value at a timing that reaches a state suitable for detection of the fuel gas;
A second heating current application unit for applying a heating current for making the incomplete combustion gas sensor suitable for detection of incomplete combustion gas;
An incomplete combustion gas detection value acquisition unit that acquires a gas detection value by the incomplete combustion gas sensor as an incomplete combustion gas detection value at a timing that reaches a state suitable for detection of the incomplete combustion gas;
A sensor failure determination unit for determining failure of the fuel gas sensor and the incomplete combustion gas sensor;
If it is determined that the incomplete combustion gas sensor has failed, the gas detection value detected by the fuel gas sensor is used as the incomplete combustion gas detection value at a timing when the fuel gas sensor reaches a state suitable for detection of the incomplete combustion gas. A first detection control unit that causes the fuel gas detection value acquisition unit to acquire;
When it is determined that the fuel gas sensor has failed, the incomplete combustion gas sensor is used as a fuel gas detection value as a gas detection value by the incomplete combustion gas sensor at a timing when the incomplete combustion gas sensor reaches a state suitable for detection of the fuel gas. A second detection control unit that causes the combustion gas detection value acquisition unit to acquire;
A gas detector comprising:   The incomplete combustion gas sensor is a hot-wire semiconductor type, and the timing at which the incomplete combustion gas sensor reaches a state suitable for detection of the fuel gas is the end of application of the heating current in the first heating current application unit. Item 3. The gas detection device according to Item 2.   The fuel gas sensor is a hot-wire semiconductor type, and the timing at which the fuel gas sensor reaches a state suitable for detection of the incomplete combustion gas is immediately after application of a heating current in the second heating current application unit. Or the gas detection apparatus of 3.

Images