JP2007066056A - Gas alarm - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-reliability gas alarm which prevents malfunctions due to gases not to be detected. <P>SOLUTION: The gas alarm 10 issues an alarm indicating that the concentrations gases to be detected (methane and carbon monoxide), detected by a sensor 1, become abnormal, when the concentrations of the gases reach a preliminarily fixed second-stage alarm-setting point ALP2, and raises a preliminary alarm for the concentrations of the gases, when detected concentrations reach a first-stage alarm-setting point ALP1 which is preliminarily set to correspond to a concentration lower than the second-stage alarm-setting point ALP2. In addition, the gas alarm 10 is provided with a release means (CPU) 164 which releases the first-stage alarm-setting point ALP1, when the concentration of a gas not to be detected (hydrogen), which is detected by the sensor 1, reaches a preliminarily set concentration. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gas alarm device, and more particularly to a gas alarm device that prevents malfunction due to a non-detection target gas.

  Semiconductor gas sensors are generally used as gas sensors for gas alarms. In the case of gas alarms for city gas, it is common to detect methane, which is the main component of natural gas, which is widely used nowadays. Currently, carbon monoxide gas generated during incomplete combustion of the combustor is detected. Gas alarms that have a function to detect are the mainstream.

As such a gas sensor for a gas alarm device, a semiconductor type gas sensor having a structure as shown in FIG. 1 that simultaneously detects methane (CH ₄ ) and carbon monoxide (CO) gas is used. The semiconductor gas sensor 1 is mainly formed of a metal oxide such as tin oxide (SnO ₂ ), and is formed of a gas sensitive body 1a that exhibits a resistance change when a gas is present, and a metal resistor such as platinum (Pt). A heater 1b for heating the gas sensitive body 1a, heater electrodes 1b1 and 1b2 led out of the sensor from the heater 1b, and a sensor electrode 1c for detecting a resistance change of the gas sensitive body 1a Have

  When methane is detected using such a semiconductor gas sensor, the element temperature is heated to about 400 ° C., and when carbon monoxide gas is detected, the temperature is heated to about 100 ° C. However, in the case of a semiconductor type gas sensor, when used for a long time, sensitization to hydrogen, which is a non-detection target gas, becomes a very bottleneck. Of course, there are gas sensors that take measures to sensitize hydrogen, but the current situation is that they cannot be easily handled.

For example, Japanese Patent Laid-Open No. 2002-82083 (Patent Document 1) discloses a method of performing correction in a circuit as a gas sensor taking measures against hydrogen sensitization. In this system, the relationship between the element temperature of the gas sensor and the detected gas has characteristics as shown in FIG. In FIG. 2, device temperature vs. air temperature (AIR), an atmosphere containing 500 ppm of carbon monoxide (CO), an atmosphere containing 500 ppm of methane (CH ₄ ), and an atmosphere containing 500 ppm of hydrogen (H ₂ ), respectively. The sensor resistance characteristic is shown. By utilizing such characteristics, it is possible to selectively detect methane on the high temperature side and carbon monoxide gas on the low temperature side, and in the intermediate temperature range, detect hydrogen that is a non-detection target gas. It is possible to detect selectively.

That is, as shown in FIG. 3, in the timing chart of the heater voltage and gas detection point of the semiconductor gas sensor, the A part of the methane detection point (immediately before switching from the high voltage heated to 400 ° C. to the low voltage) and carbon monoxide C section (temperature change region of constant voltage heated from high voltage heated to 400 ° C to 100 ° C) between B point of detection point (immediately before switching from low voltage heated to 100 ° C to high voltage) When the hydrogen gas is detected by using the hydrogen gas, the methane side alarm judgment point or the carbon monoxide gas side alarm judgment point is corrected in a direction in which it is difficult to alarm.
JP 2002-82083 A (Embodiment 2, FIG. 8)

  However, in the prior art, when the hydrogen gas that is a non-detection target gas and the detection target gas are mixed at the same time, or in the event of a malfunction in the event of a malfunction, it is not possible to make a significant correction. There was a problem.

  Therefore, in view of the above-described conventional problems, an object of the present invention is to provide a highly reliable gas alarm device by preventing malfunction caused by a non-detection target gas.

  The present invention as set forth in claim 1 issues a warning that the gas concentration has become abnormal when the concentration of the detection target gas detected by the gas sensor exceeds a preset second-stage alarm set point. In addition, when the detected concentration is equal to or higher than the first-stage alarm set point that is set in advance so as to correspond to a concentration lower than the second-stage alarm set point, a gas alarm device that notifies a gas concentration preliminary alarm And when the density | concentration of the non-detection object gas detected by the said gas sensor becomes more than the preset density | concentration, it has the cancellation | release means which cancels | releases the said 1st step | paragraph alarm set point, It is characterized by the above-mentioned.

  The present invention according to claim 2 issues a warning that the gas concentration has become abnormal when the concentration of the gas to be detected detected by the gas sensor exceeds a preset second stage alarm set point. In addition, when the detected concentration is equal to or higher than the first-stage alarm set point that is set in advance so as to correspond to a concentration lower than the second-stage alarm set point, a gas alarm device that notifies a gas concentration preliminary alarm When the concentration of the non-detection target gas detected by the gas sensor is equal to or higher than a preset concentration, a release means for canceling the first-stage alarm set point, and non-detection detected by the gas sensor And a resetting means for resetting the second-stage alarm set point in a direction in which it is difficult to alarm when the concentration of the target gas exceeds a preset concentration.

  According to a third aspect of the present invention, when the concentration of the detection target gas detected by the gas sensor becomes equal to or higher than a preset second-stage alarm set point, an alarm that the gas concentration has become abnormal is notified. In addition, when the detected concentration is equal to or higher than the first-stage alarm set point that is set in advance so as to correspond to a concentration lower than the second-stage alarm set point, a gas alarm device that notifies a gas concentration preliminary alarm When the concentration of the non-detection target gas detected by the gas sensor is equal to or higher than a preset concentration, the first stage alarm set point and the second stage alarm set point are alerted at a predetermined correction rate. Resetting means for resetting in a difficult direction, wherein the resetting means sets the correction rate of the first stage alarm set point to a ratio larger than the correction rate of the second stage alarm set point and the 1 after resetting. The second stage alarm set point after the second stage alarm set point is reset Characterized by re-set not to exceed.

  The present invention according to claim 4 issues a warning that the gas concentration has become abnormal when the concentration of the detection target gas detected by the gas sensor exceeds a preset second-stage alarm set point. In addition, when the detected concentration is equal to or higher than the first-stage alarm set point that is set in advance so as to correspond to a concentration lower than the second-stage alarm set point, a gas alarm device that notifies a gas concentration preliminary alarm When the concentration of the non-detection target gas detected by the gas sensor is equal to or higher than a preset concentration, the concentration of the detection target gas is equal to or higher than a preset second stage alarm set point. In addition, the alarm is notified after a predetermined delay time T2 'elapses, and when the concentration of the detection target gas exceeds a preset first-stage alarm set point, the elapse of the predetermined delay time T1' elapses. Delay to alert the preliminary alarm Characterized by comprising setting means for setting between.

  According to the fifth aspect of the present invention, when the concentration of the detection target gas detected by the gas sensor becomes equal to or higher than a preset second stage alarm set point, the gas is detected after a predetermined delay time T2 has elapsed. When notifying the alarm that the concentration has become abnormal, and when the detected concentration is equal to or higher than the first-stage alarm set point set in advance so as to correspond to a concentration lower than the second-stage alarm set point. , A gas alarm device for notifying a preliminary gas concentration warning after elapse of a predetermined delay time T1, when the concentration of the non-detection target gas detected by the gas sensor is equal to or higher than a predetermined concentration. Further, there is provided a resetting means for resetting the predetermined delay time T1 and / or T2 to a longer delay time T1 ′ and / or T2 ′.

  According to the first to sixth aspects of the present invention, it is possible to reduce the malfunction caused by the non-detection target gas and to perform a more reliable alarm operation.

  Hereinafter, embodiments of a gas alarm device according to the present invention will be described with reference to the drawings.

  (First Embodiment) FIG. 4 is a circuit diagram showing a gas alarm device according to an embodiment of the present invention. The gas alarm device 10 includes a semiconductor gas sensor 1, a heating drive circuit 14, an operation mode control circuit 16, and an alarm circuit 18.

  The semiconductor gas sensor 1 is a sensor that has the structure shown in FIG. 1 and detects methane and carbon monoxide as detection target gases and hydrogen as non-detection target gases. The heater 1b of the semiconductor gas sensor 1 has one end connected to the collector of the pnp transistor Q1 of the heating drive circuit 14 and the other end grounded. The sensor electrode 1c is connected to the input port P3 of the CPU 164. When the gas sensitive body 1a comes into contact with the gas, the sensor resistance value decreases in response to the concentration, and the detection voltage starts to decrease. Applied to input port P3.

  The heating drive circuit 14 includes a pnp transistor Q1 having an emitter connected to the power source Vcc and a collector connected to the heater 1b of the gas sensor 1, a resistor R1 connected between the emitter and base of the transistor Q1, and a base of the transistor Q1. And a resistor R2 connected between the output port P4 of the CPU 164.

  In response to the heating control signal from the output port P4 of the CPU 164, the heating drive circuit 14 supplies the heater 1b with a heater voltage whose level is alternately changed between a high voltage and a low voltage as shown in FIG. Thus, the temperature of the semiconductor gas sensor 1 becomes a low temperature range (preferably 100 ° C.) of about 80 to 120 ° C. for a predetermined period (for example, 10 to 20 seconds) and for a predetermined period (for example, 3 to 5 seconds). The heating is controlled so as to be in a high temperature range of about 350 to 450 ° C. (preferably 400 ° C.).

  The operation mode control circuit 16 is configured around a CPU 164 as a canceling means, a resetting means, and a setting means, and further, a first gas alarm concentration as a reference concentration for generating an alarm for methane gas as the first gas. A first reference voltage generation unit for setting a first gas alarm level (corresponding to a set voltage value for methane gas described later) as a reference voltage level corresponding to, and an alarm for carbon monoxide gas as the second gas A second reference voltage generation unit for setting a second gas alarm level (corresponding to a set voltage value for carbon monoxide gas described later) as a reference voltage level corresponding to the second gas alarm concentration as a generated reference concentration And have.

  The first reference voltage generation unit includes a resistor R7 connected in series between the power supply Vcc and the ground, and a volume VR1 that is variably controlled by a control signal from the output port P7 of the CPU 164. The first gas alarm level is determined by the voltage division ratio (ie, VR1 / (VR1 + R7) between the resistance value of VR1 and the resistance value of resistor R7 obtained by adjusting the volume VR1, and is output to the input port P1 of the CPU 164. The

  Similarly, the second reference voltage generation unit includes a resistor R9 connected in series between the power supply voltage Vcc and the ground, and a volume VR2 that is variably controlled by a control signal from the output port P7 of the CPU 164. The second gas alarm level is determined by the voltage division ratio (ie, VR2 / (VR2 + R9) between the resistance value of VR2 and the resistance value of resistor R9 obtained by adjusting the volume VR2, and is output to the input port P2 of the CPU 164. The

  The operation mode control circuit 16 detects the concentration of methane gas with the detection voltage of the semiconductor gas sensor 1 taken in the detection point A portion of the methane gas in the above-described high temperature range, and the detected concentration reaches the first gas alarm concentration. When it does, it has the function to alert | report the alarm to the effect that the density | concentration of methane gas became abnormal.

  Further, the operation mode control circuit 16 detects the concentration of the carbon monoxide gas with the detection voltage of the semiconductor gas sensor 1 taken in at the carbon monoxide gas detection point B in the low temperature range, and the detected concentration Has a function of notifying that the concentration of carbon monoxide gas has become abnormal when the second gas alarm concentration is reached.

  The sensor control unit 162 provided in the operation mode control circuit 16 includes a pnp transistor Q2 having an emitter connected to the power supply Vcc and a collector connected to the sensor electrode 1c as a load via a resistor R4, a power supply Vcc, A resistor R5 connected between the base of the transistor Q2, a resistor R6 connected between the base of the transistor Q2 and the output port P5 of the CPU 164, and between the power supply Vcc and the sensor electrode 1c for applying a bias current to the sensor electrode 1c. The resistor R3 is connected.

  The sensor control unit 162 generates a gas concentration detection voltage in the gas sensor 1 at the detection timing of the A part of the methane detection point, the B part of the carbon monoxide detection point, and the C part of the hydrogen detection point shown in FIG. Has a function of generating an enable signal for instructing.

  The CPU 164 outputs an enable control signal from the output port P5 and controls the transistor Q2, thereby taking in the gas concentration detection voltage from the sensor electrode 1c from the input terminal P3.

  The alarm circuit 18 includes an npn transistor Q3 whose base is connected to the output port P6 of the CPU 164, a buzzer (BZ) 182 connected between the collector and the power supply Vcc as a collector load of the transistor Q3, and an output port P9 of the CPU 164. An npn transistor Q4 having a base connected thereto and a light emitting diode (LED) 183 connected between a collector and a power source Vcc as a collector load of the transistor Q4.

  FIG. 5 is a diagram illustrating the alarm timing of the alarm circuit 18 in the normal operation state when the non-detection target gas (hydrogen gas) is not present. In FIG. 5, the second stage alarm set point ALP2 corresponds to the first gas alarm level or the second gas alarm level, and the first stage alarm set point ALP1 is based on the second stage alarm set point ALP2. The set point is set in the CPU 164 so as to correspond to a density lower by a predetermined value.

  City gas alarms usually require an alarm in the range of 1/200 to 1/4 of the LEL (lower explosion limit) when flammable gas is detected. It has ALP1 and second-stage alarm set point ALP2. Generally, the first-stage alarm set point ALP1 is set to 1/50 to 1/100 of LEL, 0.05 to 0.1% in the case of methane, and the second-stage alarm set point ALP2 is set to LEL. Is set to around 0.3%, which is about 1/20 of. For carbon monoxide gas, which is an incomplete combustion gas, the first-stage alarm set point is set to 50 to 200 ppm, and the second-stage alarm set point is set to 550 ppm or less (usually 300 ppm).

  The LED 183 of the alarm means 18 for notifying the alarm, when the detection voltage of the semiconductor gas sensor 1 reaches a detection value exceeding the first-stage alarm set point ALP1, for example, reaches the detection voltage value Vk at the methane detection point, Under the control of the CPU 164, it blinks after a predetermined delay time T1 has elapsed. This blinking of the LED 183 gives a preliminary warning that the concentration of methane has reached a level slightly before the dangerous concentration. This blinking is started when the detection value at the methane detection point after the first detection point continuously exceeds the first-stage alarm set point ALP1, and a predetermined delay time T1 has elapsed, and the detection value after the start Stops when it falls below the first stage alarm set point ALP1 or rises above the second stage alarm set point ALP2.

  Further, the LED 183 of the alarm means 18 for notifying the alarm reaches the detection voltage value Vk + 1 at the methane detection point, for example, when the detection voltage of the semiconductor gas sensor 1 reaches a detection value exceeding the second-stage alarm set point ALP2. In this case, the light is turned on after elapse of a predetermined delay time T2 under the control of the CPU 164. The lighting of this LED 183 warns that the concentration of methane has reached a dangerous concentration. This lighting is started when the detection value at the methane detection point after the first detection point continuously exceeds the second-stage alarm set point ALP2 and a predetermined delay time T2 has elapsed, and the detection value after the start Stops (extinguishes) when falls below the second stage alarm set point ALP2.

  When the detection voltage of the semiconductor gas sensor 1 reaches a detection value exceeding the second-stage alarm set point ALP2, for example, when the detection voltage value Vk + 1 at the methane detection point is reached, Under the control of the CPU 164, the ringing is started after a predetermined delay time T2 has elapsed and the alarm sound 18a is emitted. The alarm sound 18a of the BZ182 warns that the methane concentration has reached a dangerous concentration when the LED 183 is turned on. The alarm sound 18a is started when the detection value at the methane detection point after the first detection point continuously exceeds the second-stage alarm set point ALP2, and a predetermined delay time T2 has elapsed. Stops when the detected value falls below the second stage alarm set point ALP2.

  Specifically, the predetermined delay times T1 and T2 described above are set in accordance with the certification regulations established by the Japan Gas Appliances Inspection Association. In this test regulation, for methane, an alarm is given within 60 seconds upon detection of methane at an alarm concentration or higher, and for carbon monoxide, within 50 minutes from 50 ppm to less than 200 ppm, within 5 minutes at 550 ppm or less. For example, the delay time for methane is arbitrary for the delay time T1 that is not defined in the test regulations, and therefore, for example, T1 = 50 seconds, and for the delay time T2 that is defined in the test regulations, As an example, T2 = 10 seconds is set, and the delay times for carbon monoxide are set as T1 = 5 minutes and T2 = 0 minutes.

  In addition, although the above-mentioned alarm operation | movement demonstrated the case of detection of methane gas, since it becomes the same operation | movement also in the case of detection of carbon monoxide, description is abbreviate | omitted.

  In the present invention, in addition to the normal operation state when the non-detection target gas (hydrogen gas) is not present, malfunction due to the non-detection target gas (hydrogen gas) is reduced when the non-detection target gas (hydrogen gas) is present. Thus, the operating state is corrected. Hereinafter, the processing operation accompanied with the correction when the non-detection target gas (hydrogen) is present will be described.

  FIG. 6 is a flowchart showing a processing operation with correction performed when the non-detection target gas (hydrogen) is present, which is executed by the CPU 164.

  First, a standby operation is performed (step S1), and then it is determined whether or not hydrogen gas is determined (step S3). This determination is made by the CPU 164 detecting the concentration of hydrogen gas at the detection voltage of the semiconductor gas sensor 1 taken from the input port P3 at the hydrogen detection point C, and setting the detected hydrogen gas concentration to a predetermined hydrogen determination concentration. It is done by comparing with.

  If the detected hydrogen gas concentration does not exceed the hydrogen determination concentration (NO in step S3), then a standby operation is performed (step S5), and then the process returns to step S1. If the detected hydrogen gas concentration exceeds the hydrogen determination concentration (YES in step S3), then the first-stage alarm set point ALP1 is released (step S7), and then the second-stage set point ALP2 A voltage value obtained by multiplying the set voltage value by a coefficient (correction rate) B (<1) is reset as a new set voltage value for the second-stage alarm set point ALP2 (step S9). This resetting is calculated in the CPU 164.

  Next, it is determined whether or not there is a determination of hydrogen gas (step S11). If the answer is YES, then the process returns to step S7, and the processes of steps S7 and S9 are repeated. Therefore, since the first stage set point ALP1 is released while hydrogen gas is present, the LED 183 is not blinked, so that a preliminary alarm is not notified. In addition, since the set voltage value corresponding to the second stage set point ALP2 is reset in a direction that is difficult to alarm, it is possible to prevent erroneous detection of hydrogen gas and malfunction at the second alarm set point. .

  On the other hand, if the answer to step S11 is NO, the release of the first stage alarm set point ALP1 is canceled and the normal setting state is restored (step S13), and then the set voltage of the second stage alarm setting ALP2 The value returns to a normal value (step S15), and then returns to step S1. The return of the set voltage value of the second stage alarm setting ALP2 is calculated in the CPU 164. Accordingly, when the hydrogen gas no longer exists, the gas alarm device 10 returns to the normal sensor sensitivity state, and both the preliminary alarm by the LED 183 and the alarm by the LEDs 183 and BZ182 are notified.

  Thus, in the first embodiment, when hydrogen correction is performed on methane gas, the first-stage alarm set point that is normally used for the preliminary alarm is canceled, and the second-stage alarm that is used for the main alarm. When a gas concentration equal to or higher than the alarm concentration at the set point is detected, the second-stage set voltage value is reset in a direction that is difficult to alarm. The preliminary alarm based on the first-stage alarm set point is a preliminary function to notify the degree of danger in advance, and there is little possibility of giving danger to the user even if the worst notification is not given. What is necessary is just to alert | report reliably by an alarm. Therefore, when hydrogen is detected, that is, when a non-detection target gas is detected, it is possible to minimize the probability of malfunction for hydrogen by stopping the preliminary alarm based on the first-stage alarm set point. . In this way, it is possible to prevent malfunctions at the first and second alarm set points, which have been a major problem in the case where significant correction cannot be applied in consideration of actual fail-out. It is effective against.

  (Second Embodiment) Next, FIG. 7 is a flowchart showing a processing operation accompanied by hydrogen correction executed by the CPU 164 in the second embodiment of the present invention.

  First, a standby operation is performed (step S31), and then it is determined whether or not hydrogen gas is determined (step S33). This determination is performed by the CPU 164 detecting the hydrogen gas concentration at the detection voltage of the semiconductor gas sensor 1 at the hydrogen detection point C and comparing the detected hydrogen gas concentration with a preset hydrogen determination concentration. Is called.

  If the detected hydrogen gas concentration does not exceed the hydrogen determination concentration (NO in step S33), then a standby operation is performed (step S35), and then the process returns to step S31. If the detected hydrogen gas concentration exceeds the hydrogen determination concentration (YES in step S33), then a voltage value obtained by multiplying the set voltage value of the first stage alarm set point ALP1 by a coefficient (correction factor) A (<1). Is set as a new set voltage value for the first stage alarm set point ALP1 (step S37), and then the set voltage value for the second stage set point ALP2 is multiplied by a coefficient (correction factor) B (<1). The voltage value is set as a new set voltage value for the second stage alarm set point ALP2 (step S39). The coefficients A and B can be set to arbitrary values, for example, B = 0.5 or B = 0.3 with respect to A = 0.25, but the first stage alarm set point is 2 Consideration is made so as not to exceed the stage alarm set point and to make a correction of A <B.

  Next, it is determined whether or not there is a determination of hydrogen gas (step S41). If the answer is YES, then the process returns to step S37, and the processes of steps S37 and S39 are repeated. Therefore, while the hydrogen gas is present, the set voltage values corresponding to the first-stage set point ALP1 and the second-stage set point ALP2 are reset in directions that are difficult to alarm. It is possible to prevent erroneous operation at the first alarm set point and malfunction at the second alarm set point by erroneous detection.

  On the other hand, if the answer to step S41 is no, then the set voltage value of the first stage alarm set point ALP1 returns to a normal value (step S43), and then the set voltage value of the second stage alarm set point ALP2 is It returns to a normal value (step S45), and then returns to step S31. Therefore, when the hydrogen gas no longer exists, the gas alarm device 10 returns to the normal sensor sensitivity state.

  Thus, in the second embodiment, when hydrogen correction is performed on methane gas and carbon monoxide gas, the first-stage alarm set point that is normally used for the preliminary alarm and the second stage that is used for the main alarm. When a gas concentration higher than the alarm concentration at the first alarm set point is detected, the first-stage alarm set point and the second-stage set voltage value are reset in a direction that makes it difficult to alarm. In this way, it is possible to prevent malfunctions at the first and second alarm set points, which have been a major problem in the case where significant correction cannot be applied in consideration of actual fail-out. It is effective against.

  (Third Embodiment) FIG. 8 is a flowchart showing a processing operation with hydrogen correction executed by the CPU 164 in the third embodiment of the present invention.

  First, a standby operation is performed (step S51), and then it is determined whether or not hydrogen gas is determined (step S53). This determination is performed by the CPU 164 detecting the hydrogen gas concentration at the detection voltage of the semiconductor gas sensor 1 at the hydrogen detection point C and comparing the detected hydrogen gas concentration with a preset hydrogen determination concentration. Is called.

  If the detected hydrogen gas concentration does not exceed the hydrogen determination concentration (NO in step S53), then a standby operation is performed (step S55), and then the process returns to step S51. If the detected hydrogen gas concentration exceeds the hydrogen determination concentration (YES in step S53), then the delay time T1 of the first-stage alarm set point ALP1 is set as a longer delay time T1 ′ (> T1) ( Next, the delay time T2 of the second stage set point ALP2 is set as a longer delay time T2 ′ (> T2) (step S59).

  According to the test regulations, when methane is detected, it is normally required to detect within 60 seconds. Therefore, when the detection response capability of the semiconductor gas sensor 1 is 30 seconds, the delay time is set for the second-stage alarm set point ALP2. For example, T2 '= 20 to 30 seconds is reset for T2 = 10 seconds, and for the first stage alarm set point ALP1 that has no time limit, for example, T2' = for delay time T1 = 50 seconds. Reset to 100 seconds. Similarly, when detecting carbon monoxide gas, detection within 15 minutes is required at the first stage alarm set point, and detection within 5 minutes is required at the second stage alarm set point. Is reset to, for example, T2 ′ = 3 minutes for delay time T2 = 0 minutes, and is reset to, for example, T2 ′ = 10 minutes for delay time T1 = 5 minutes for first stage alarm set point ALP1. The

  Next, it is determined whether or not there is a determination of hydrogen gas (step S61). If the answer is YES, then the process returns to step S57, and the processes of steps S57 and S59 are repeated. Therefore, while the hydrogen gas is present, the set voltage values corresponding to the first-stage set point ALP1 and the second-stage set point ALP2 are reset in directions that are difficult to alarm. It is possible to prevent erroneous operation at the first alarm set point and malfunction at the second alarm set point by erroneous detection.

  On the other hand, if the answer to step S61 is no, then the set voltage value of the first stage alarm set point ALP1 returns to a normal value (step S63), and then the set voltage value of the second stage alarm set point ALP2 is It returns to the normal value (step S65), and then returns to step S51. Therefore, when the hydrogen gas no longer exists, the gas alarm device 10 returns to the normal sensor sensitivity state.

  Thus, in the third embodiment, when hydrogen correction is performed on methane gas and carbon monoxide gas, the first-stage alarm set point that is normally used for the preliminary alarm and the second stage that is used for the main alarm. When a gas concentration equal to or higher than the alarm concentration at the eye alarm set point is detected, the alarm notification is further delayed from the detection time. In particular, hydrogen gas, which has a high sensitization tendency, has a characteristic that it has a low molecular weight and is easy to diffuse. In other words, even if it occurs in ordinary households, it is considered that there are many transient occurrences, so a delay time longer than usual should be provided so as not to hinder the detection ability of the detection target gas and the response capability of the gas sensor. Can do. In this way, it is possible to prevent malfunctions at the first and second alarm set points, which have been a major problem in the case where significant correction cannot be applied in consideration of actual fail-out. It is effective against.

  As described above, according to the present invention, in relation to an alarm device that performs sensitization countermeasure correction for hydrogen gas in a gas alarm device using a semiconductor gas sensor, by adding a function that prevents malfunction from being achieved conventionally, It is possible to provide a more reliable alarm device.

  As described above, the best mode of the present invention has been described, but the present invention is not limited to this, and various modifications and applications are possible.

  For example, in the third embodiment described above, both of the delay times T1 and T2 are reset to longer delay times T1 ′ and T2 ′. However, the present invention is not limited to this, and only one of them, ie, the delay time T1. Alternatively, T2 may be reset to a longer delay time T1 ′ or T2 ′.

  Further, in the above-described third embodiment, the delay times T1 = 0 and T2 = 0 may be set. That is, in this case, the CPU 164 sets the delay time T1 (= 0) of the first-stage alarm set point ALP1 to a predetermined delay time (for example, T1 ′) in step S57, and in step S59, the second-stage alarm setting point ALP1. Each delay time is set so that the delay time T2 (= 0) of the set point ALP2 becomes a predetermined delay time (for example, T2 ′).

It is a schematic diagram showing a structural example of a semiconductor gas sensor. It is a characteristic view which shows the relationship between the element temperature of a gas sensor, and the sensor resistance value of detection gas. It is a timing chart of the heater voltage and gas detection point of a semiconductor type gas sensor. It is a circuit diagram which shows the gas alarm device which concerns on embodiment of this invention. (First embodiment) It is a figure explaining the alarm timing of the alarm circuit in the normal operation state at the time of non-detection object gas absence. (First embodiment) It is a flowchart which shows the processing operation accompanied by the correction | amendment at the time of non-detection object gas presence. (First embodiment) It is a flowchart which shows the processing operation accompanied by the correction | amendment at the time of non-detection object gas presence. (Second Embodiment) It is a flowchart which shows the processing operation accompanied by the correction | amendment at the time of non-detection object gas presence. (Third embodiment)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor type gas sensor 10 Gas alarm device 14 Heating drive circuit 16 Operation mode control circuit 18 Alarm circuit 164 CPU (release means, resetting means, setting means)
182 Buzzer (BZ)
183 Light Emitting Diode (LED)

Claims (5)

When the concentration of the detection target gas detected by the gas sensor becomes equal to or higher than a preset second-stage alarm set point, an alarm that the gas concentration has become abnormal is notified, and the detected concentration is 2 A gas alarm device for notifying a preliminary alarm of gas concentration when a preset first stage alarm set point corresponding to a concentration lower than the stage alarm set point is reached,
A gas alarm device comprising release means for canceling the first stage alarm set point when the concentration of the non-detection target gas detected by the gas sensor is equal to or higher than a predetermined concentration. When the concentration of the detection target gas detected by the gas sensor becomes equal to or higher than a preset second-stage alarm set point, an alarm that the gas concentration has become abnormal is notified, and the detected concentration is 2 A gas alarm device for notifying a preliminary alarm of gas concentration when a preset first stage alarm set point corresponding to a concentration lower than the stage alarm set point is reached,
When the concentration of the non-detection target gas detected by the gas sensor is equal to or higher than a preset concentration, release means for canceling the first stage alarm set point;
When the concentration of the non-detection target gas detected by the gas sensor is equal to or higher than a preset concentration, resetting means is provided for resetting the second-stage alarm set point in a direction that is difficult to alarm. And gas alarm. When the concentration of the detection target gas detected by the gas sensor becomes equal to or higher than a preset second-stage alarm set point, an alarm that the gas concentration has become abnormal is notified, and the detected concentration is 2 A gas alarm device for notifying a preliminary alarm of gas concentration when a preset first stage alarm set point corresponding to a concentration lower than the stage alarm set point is reached,
When the concentration of the non-detection target gas detected by the gas sensor is equal to or higher than a preset concentration, the first-stage alarm set point and the second-stage alarm set point are reset in a direction that makes it difficult to alarm at a predetermined correction rate. With resetting means to set,
The resetting means sets the correction rate of the first-stage alarm set point to a ratio larger than the correction rate of the second-stage alarm set point, and the second-stage alarm set point after the reset is the 2 A gas alarm that is reset so as not to exceed the stage alarm set point. When the concentration of the detection target gas detected by the gas sensor becomes equal to or higher than a preset second-stage alarm set point, an alarm that the gas concentration has become abnormal is notified, and the detected concentration is 2 A gas alarm device for notifying a preliminary alarm of gas concentration when a preset first stage alarm set point corresponding to a concentration lower than the stage alarm set point is reached,
When the concentration of the non-detection target gas detected by the gas sensor is equal to or higher than a predetermined concentration, when the concentration of the detection target gas is equal to or higher than a preset second-stage alarm set point, The alarm is notified after the delay time T2 'has elapsed, and the preliminary alarm is notified after the predetermined delay time T1' has elapsed when the concentration of the detection target gas exceeds a preset first-stage alarm set point. A gas alarm device comprising setting means for setting a delay time as described above. When the concentration of the detection target gas detected by the gas sensor becomes equal to or higher than a preset second-stage alarm set point, an alarm that the gas concentration has become abnormal after a predetermined delay time T2 has elapsed. And a predetermined delay time set in advance when the detected concentration becomes equal to or higher than the first-stage alarm set point set in advance so as to correspond to a density lower than the second-stage alarm set point. A gas alarm device for notifying a preliminary warning of gas concentration after T1 has elapsed,
When the concentration of the non-detection target gas detected by the gas sensor becomes equal to or higher than a predetermined concentration, the predetermined delay time T1 and / or T2 is reset to a longer delay time T1 ′ and / or T2 ′. A gas alarm device comprising a resetting means.

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