JP2001194330A - Gas alarm unit and gas alarming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas alarm unit and a gas alarming method capable of beforehand detecting/reporting deterioration of a gas sensor in sensitivity in the event that the gas sensor is driven by a battery with limited capacity. SOLUTION: In this gas alarm unit, the gas sensor 1 is on-off driven with a specified period by a pulse drive signal generated by a sensor drive circuit 13 receiving a power supply voltage of the battery 5, the concentration of carbon monoxide is detected during off-drive periods of the sensor 1, and an alarm is given to indicate an abnormal concentration of carbon monoxide when a detected concentration of carbon monoxide exceeds an alarm point. A sensor detection circuit 9 detects the value of sensor resistance of a sensor element 3 during an on-drive period in each of the periods. A sensor abnormality judging circuit 16 judges whether the sensor 1 is abnormal based on variations in a plurality of detected values of sensor resistance. An LED 21 gives an alarm indicating the abnormality of the sensor 1 when the sensor 1 is judged to be abnormal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting carbon monoxide (CO) gas during incomplete combustion with a gas sensor and issuing an alarm indicating that the gas concentration is abnormal when the gas concentration exceeds an alarm point. The present invention relates to a battery-operated gas alarm device and a gas alarm method for issuing an alarm sound, an alarm lamp, an external output, and the like, and particularly to a battery-operated gas alarm device and a gas alarm method for driving a gas sensor with a limited battery capacity.

[0002]

2. Description of the Related Art As a gas sensor for a carbon monoxide gas alarm, a semiconductor gas sensor is generally used. In order to selectively detect carbon monoxide with the semiconductor gas sensor, the temperature of a sensor element must be increased. Must be kept at a low temperature, for example, 100 ° C. or lower.

However, if the gas sensor is used at a low temperature for a long period of time, there is a problem that moisture adheres to the sensor element due to a change in the temperature in the atmosphere, and the sensor output in the air changes. Cannot be accurately detected. Therefore, as shown in FIG. 6, the gas sensor is set to a low temperature (for example, 100 ° C. for 15 seconds) and a high temperature (for example,
It is necessary to perform heat cleaning in which the gas sensor is driven alternately and periodically (at 00 ° C. for 5 seconds) to raise the temperature of the gas sensor and refresh the surface of the gas sensor.

There is also known a carbon monoxide gas alarm which uses a battery as a power supply and drives a gas sensor with the power supply voltage of the battery. The battery type carbon monoxide gas alarm device receives a power supply voltage of a battery, generates a pulse drive signal, and alternately turns on / off a gas sensor having a heater and a sensor element in a predetermined cycle by the pulse drive signal, During the off-drive period of the gas sensor, that is, at normal temperature, the concentration of carbon monoxide gas is detected. A conventional gas alarm of this type is disclosed in, for example, a gas detection method and apparatus disclosed in Japanese Patent Application Laid-Open No. 10-38832.

In this battery type carbon monoxide gas alarm,
Usually, the gas sensor is heat-cleaned by periodically heating up the gas sensor under a condition where the battery capacity is limited and the device can be used for three years, for example.

[0006]

However, in the case of a battery-type carbon monoxide gas alarm, in order to keep the battery for a long period of time, for example, three years, it is necessary to periodically heat the battery. The power used for cleaning is very limited.

For example, using two lithium batteries having a capacity of 2200 mAhr in parallel
Assuming that 130 mA of electric power is required for heating to ° C., considering the use safety factor of the battery, the circuit power consumption as an alarm device, and the power consumption at the time of an alarm in the event of an alarm, it takes about 1 second every 10 minutes. The degree of heating is the limit.

Further, under the above-described conditions and in a normal atmosphere, a stable sensor output can be obtained over time, as shown in the time-dependent characteristics of the battery-operated gas alarm shown in FIG. In the time characteristic shown in FIG. 7, the temperature is set to 20 ° C., the humidity is set to 65%, and as shown in FIG.
The graph shows the change over time of the alarm point of carbon monoxide when a pulse of 200 seconds in 0 seconds is applied to the gas sensor for a long time (sensor driving condition). In addition, the gas sensor
MAX and MIN in the upper right of FIG. 7 represent the variation of the alarm points among the ten gas sensors.

However, FIG. 8 shows a case where the gas sensor is continuously left in a high temperature and high humidity (for example, at a temperature of 50 ° C. and a humidity of 95%) and an acceleration test in which the gas sensor is driven under the above-described sensor driving conditions is performed. Thus, as the number of acceleration days increases, the CO alarm concentration increases. That is, the sensitivity of the gas sensor deteriorates in high humidity. In the example shown in FIG. 8, three gas sensors are tested, and a black circle, a black triangle, and a black square in FIG. 8 correspond to the three gas sensors.

The deterioration of the sensitivity of the gas sensor is largely affected by the drift of the sensor output in air (hereinafter referred to as air base). Usually, the air base on the low temperature side for detecting carbon monoxide has a very high resistance, and it is difficult to distinguish between a normal gas sensor and a sensitivity-deteriorated gas sensor.

Therefore, the present invention provides a gas alarm device and a gas alarm method capable of detecting and notifying in advance that the sensitivity of the gas sensor has deteriorated when the gas sensor is driven with a limited battery capacity. The task is to

[0012]

Means for Solving the Problems To solve the above problems, the present invention has the following arrangement. According to the first aspect of the present invention, the gas sensor having the heater and the sensor element is alternately turned on / off at a predetermined cycle by a pulse drive signal by operating with the power supply voltage of the battery, and the carbon monoxide gas concentration is reduced during the off drive period of the gas sensor. In the gas alarm device that detects and detects an alarm indicating an abnormality in the concentration of carbon monoxide gas when the detected concentration of carbon monoxide gas is equal to or higher than the alarm point, in the on-drive period of the gas sensor every predetermined cycle Detecting means for detecting a sensor resistance value of the sensor element; abnormality determining means for determining an abnormality of the gas sensor based on a change in a plurality of sensor resistance values detected by the detecting means; And notifying means for notifying an alarm indicating an abnormality of the gas sensor when it is determined that the gas sensor is abnormal.

According to the first aspect of the present invention, when the detecting means detects the sensor resistance value of the sensor element in the on-drive period at predetermined intervals, the abnormality determining means detects the plurality of sensor resistance values detected by the detecting means. The abnormality of the gas sensor is determined based on the change of the gas sensor, and the notification unit notifies the warning indicating the abnormality of the gas sensor when the abnormality determination unit determines that the gas sensor is abnormal, so that it is easily understood that the sensitivity of the gas sensor has deteriorated. .

According to a second aspect of the present invention, in the gas alarm device according to the first aspect, the abnormality determination means includes an initial sensor resistance value detected in a first on-drive period and a second and subsequent on-drive periods. When the ratio of the sensor resistance change to the sensor resistance value detected in (1) exceeds a predetermined determination value, it is determined that the sensitivity of the gas sensor has deteriorated.

According to the second aspect of the present invention, the abnormality determining means detects the sensor resistance between the initial sensor resistance detected during the first on-drive period and the sensor resistance detected during the second and subsequent on-drive periods. When the change ratio exceeds a predetermined determination value, it is determined that the sensitivity of the gas sensor has deteriorated, so that it is easily known that the sensitivity of the gas sensor has deteriorated.

According to a third aspect of the present invention, in the gas alarm according to the first or second aspect, the notifying means outputs an alarm indicating an abnormality in the concentration of carbon monoxide gas and an alarm indicating an abnormality in the gas sensor. It is characterized by identifying and reporting.

According to the third aspect of the present invention, the notifying means identifies and notifies an alarm indicating an abnormality in the concentration of carbon monoxide gas and an alarm indicating an abnormality in the gas sensor. It is possible to easily identify whether the gas sensor is abnormal.

According to a fourth aspect of the present invention, a gas sensor having a heater and a sensor element is alternately turned on / off at a predetermined cycle by a pulse drive signal by operating with a power supply voltage of a battery. In a gas alarm method for detecting a gas concentration and notifying an alarm indicating an abnormality of the carbon monoxide gas concentration when the detected carbon monoxide gas concentration is equal to or higher than an alarm point, the gas sensor is turned on every predetermined cycle. A detection step of detecting a sensor resistance value of the sensor element during a driving period; an abnormality determination step of determining abnormality of the gas sensor based on a change in the detected plurality of sensor resistance values; and when the gas sensor is determined to be abnormal. And a notifying step of notifying an alarm indicating an abnormality of the gas sensor.

According to a fifth aspect of the present invention, in the gas alarm method according to the fourth aspect, the abnormality determination step includes the step of determining the initial sensor resistance value detected in the first on-drive period and the second sensor on-drive period in the second and subsequent on-drive periods. When the sensor resistance change ratio with the detected sensor resistance value exceeds a predetermined determination value, it is determined that the sensitivity of the gas sensor has deteriorated.

According to a sixth aspect of the present invention, in the gas alarm method according to the fourth or fifth aspect, the notifying step includes:
An alarm indicating an abnormality in the concentration of carbon monoxide gas and an alarm indicating an abnormality in the gas sensor are identified and notified.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a gas alarm and a gas alarm method according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a basic circuit configuration diagram of a battery-operated gas alarm of the embodiment. FIG. 2 is a specific circuit configuration diagram of the battery-operated gas alarm of the embodiment. FIG. 3 is a timing chart of a pulse drive signal in the battery-operated gas alarm of the embodiment.

The gas alarm shown in FIG. 1 is a carbon monoxide gas alarm using a battery, and includes a gas sensor 1, a battery 5 such as a lithium battery having a DC voltage (for example, 5 V), a central processing unit (CPU) 11. , The power supply voltage of the battery 5 to the CPU 1
1 is provided with a power supply circuit 7 for supplying power to the power supply circuit 1.

The gas sensor 1 is, for example, a semiconductor gas sensor, and has a sensor element 3 for detecting gas and a heater 2 for heating the sensor element 3. CPU1
1 is a battery power detection circuit 12, a sensor drive circuit 13, an alarm determination circuit 14, a memory 15, a sensor abnormality determination circuit 16
Is configured.

The battery power detection circuit 12 detects the voltage of the battery power from the power supply circuit 7 and outputs a battery abnormality signal to, for example, an alarm circuit 18 when the detected battery voltage falls below a certain value. .

The sensor drive circuit 13 receives the voltage of the battery power supply from the power supply circuit 7, generates a pulse drive signal, and alternately turns on / off the heater 2 at a predetermined cycle according to the pulse drive signal. As shown in FIG. 3, this pulse drive signal has an ON drive period of a voltage of 0.9 V (for example, 0.8 V).
Second) and voltage 0. This is a signal in which a V off drive period (for example, 200 seconds) is periodically and alternately repeated. For this reason,
The temperature of the gas sensor 1 is normal temperature (for example, 20 ° C.) and high temperature 40
It alternately changes to 0 ° C. periodically. Further, the sensor drive circuit 13 is connected to the sensor element 3 via a load resistor RL.

The sensor detection circuit 9 detects the oxidation of monoxide by a gas sensor input from the sensor element 3 at a detection point (black circles Q1, Q2... In FIG. Detect the carbon gas concentration. Further, the sensor detection circuit 9 detects the sensor resistance value of the sensor element 3 at predetermined points P1, P2,... In the ON driving period of the gas sensor 1 at the predetermined cycle. The memory 15 stores the initial sensor resistance value detected at the first point P1.

The sensor abnormality determination circuit 16 calculates a sensor resistance change ratio between the initial sensor resistance read from the memory 15 and the sensor resistance detected at the second and subsequent points P2, P3,... It is determined whether or not the sensor resistance change ratio has exceeded a sensor abnormality determination value as a predetermined determination value. If the sensor resistance change ratio has exceeded the sensor abnormality determination value, it is determined that the sensitivity of the gas sensor 1 has deteriorated.

The alarm circuit 18 includes a sensor abnormality determination circuit 16
The light emitting diode (LED) 21 and the buzzer 19 are driven when it is determined that the gas sensor 1 is abnormal. The buzzer 19 reports an alarm indicating an abnormality of the gas sensor 1. L
The ED 21 notifies a warning indicating an abnormality of the gas sensor 1 by blinking.

The alarm determination circuit 14 determines whether the carbon monoxide gas concentration has exceeded a predetermined CO alarm point, and when the carbon monoxide gas concentration has exceeded a predetermined CO alarm point. Outputs an alarm signal to the alarm circuit 18. The LED 21 notifies the alarm indicating the abnormality of the gas concentration of the carbon monoxide gas by lighting. The buzzer 19 issues an alarm indicating an abnormal gas concentration of the carbon monoxide gas.

In the specific gas alarm shown in FIG.
The reference clock generator 33 has a crystal oscillator 32 that generates a reference clock, and outputs the generated reference clock to the CPU 1.
Output to 1. The sensor drive circuit 13 generates a pulse drive signal shown in FIG. 3 based on the reference clock, outputs the pulse drive signal to the transistor Tr5 via the output port O3 and the resistor R9, and turns on / off the transistor Tr5.
The heater 2 is turned off, and the heater 2 is pulse-driven.

The sensor element 3 is connected to a detection resistor R2, a detection resistor R3, and a detection resistor R20.
And the capacitor C12 constitute the sensor detection circuit 9.
Further, the CPU 11 outputs the detection resistance drive signal to the output port O.
1 to the transistor Tr1, a detection resistance drive signal is output from the output port O2 to the transistor Tr2, and the transistors Tr1 and Tr2 are turned on / off, respectively.

Transistor Tr1 and transistor Tr
2 are both off, the detection resistor connected to the gas sensor 1 is only R20. When both the transistor Tr1 and the transistor Tr2 are on, the detection resistor connected to the gas sensor 1 is R20, R2 and R3. It becomes a parallel resistance.

A resistor R10 and a thermistor TH for correcting the temperature of the gas sensor are provided in series between one end of the resistor R3 and the ground. The CPU 11 receives a thermistor input from the thermistor TH via the input port I1. Then, the temperature of the gas sensor 1 is corrected by the thermistor input.

A resistor R11, a volume VR1, and a resistor R12 connected in series are provided between one end of the resistor R3 and the ground.
The CO alarm point is input to the alarm determination circuit 14 via the control signal 2.

A resistor R13, a volume VR2 and a resistor R14 connected in series between one end of the resistor R3 and the ground.
Is provided, and a sensor abnormality determination voltage value is input from the volume VR2 to the sensor abnormality determination circuit 16a via the input port I3.

The sensor abnormality determination circuit 16a determines whether the sensor voltage value based on the sensor resistance value detected by the sensor detection circuit 9 exceeds the sensor abnormality determination voltage value, and determines whether the sensor voltage value is equal to the sensor abnormality determination voltage value. If exceeded,
It is determined that the gas sensor 1 is abnormal.

The alarm circuit 18 includes an LED 21 and a buzzer B
Z, an integrated circuit (IC4), and the buzzer BZ is driven by the IC4. The CPU drive circuit 31 has an IC 1
A drive signal for driving the CPU 11 at a constant cycle is generated, and this drive signal is output to the CPU 11.

FIG. 4 shows the sensor resistance change ratio and the CO alarm concentration after a high-temperature and high-humidity acceleration test in which the gas sensor in the battery-operated gas alarm of the embodiment is periodically heated up in high-temperature and high-humidity. FIG. As acceleration conditions at that time, the gas sensor 1 is continuously left at a temperature of 50 ° C. and a humidity of 95%, and as a sensor driving condition, the gas sensor 1 is driven at a timing as shown in FIG.

In FIG. 4, the horizontal axis represents the sensor resistance change ratio, and the vertical axis represents the CO alarm concentration after the 46-day acceleration test. Here, the sensor resistance change ratio is a ratio between the sensor resistance value at the time of heating up and the initial sensor resistance value, as described above.

A plurality of black circles in FIG. 4 indicate a plurality of gas sensors to be tested, and there is considerable variation between non-defective products and sensitivity-degraded products. As can be seen from FIG. 4, the CO alarm concentration increases as the sensor resistance change ratio increases.
Further, as can be seen from FIG. 4, the gas sensor having the deteriorated CO alarm concentration has a large sensor resistance (resistance in the air) at the time of heating up, and a positive correlation exists between the two. .

Therefore, in the gas alarm of the embodiment,
The gas sensor 1 is periodically heat-cleaned, and a sensor resistance value at the time of heat-up (on-driving period of the gas sensor) is detected.
It is determined that the sensitivity of the gas sensor 1 has deteriorated when it has changed by up to five times. In the example shown in FIG. 4, the sensor abnormality determination value is “5”, and the minimum density at this sensor abnormality determination value is 4
400 ppm, with a maximum concentration of 6300 ppm.

Next, the operation of the gas alarm device of the embodiment thus configured, that is, the gas alarm method will be described with reference to the circuit diagram shown in FIG. 1 and the flowchart shown in FIG. Here, it is assumed that the detection of the gas concentration and the detection of the sensor resistance value of the gas sensor are performed in a high temperature and high humidity environment such as a bathroom.

First, upon receiving the power supply voltage of the battery 5, the sensor drive circuit 13 generates a pulse drive signal as shown in FIG. 3, and the pulse drive signal turns on / off the gas sensor 1 alternately at a predetermined cycle. Then, heat cleaning of the gas sensor 1 is started (Step S11).

Next, the sensor detection circuit 9 sets the sensor resistance value of the sensor element 3 at the time of heating up to a point in the on-drive period (P1, P2 in FIG. 3) every predetermined cycle, that is, every heat cleaning. ..) (step S13).

The sensor abnormality determination circuit 16 stores the initial sensor resistance value at the point P1 at the time of the initial (first) cleaning detected by the sensor detection circuit 9 in the memory 1.
5 (step S15).

Further, the sensor abnormality determination circuit 16 calculates the sensor resistance change ratio between the sensor resistance value at the second cleaning point P2 detected by the sensor detection circuit 9 and the initial sensor resistance value read from the memory 15. (Step S17).

Then, the sensor abnormality determination circuit 16 determines whether the sensor resistance change ratio has exceeded the sensor abnormality determination value (step S19). If the sensor resistance change ratio does not exceed the sensor abnormality determination value, the process returns to step S17, and in step S17, the sensor abnormality determination circuit 16 determines the third cleaning point detected by the sensor detection circuit 9. After calculating the sensor resistance change ratio between the sensor resistance value and the initial sensor resistance value at P3, the process of step S19 is performed.

That is, until the sensor resistance change ratio exceeds the sensor abnormality determination value (for example, the sensor abnormality determination value is “5”), the processing of steps S17 and S19 is repeatedly performed.

If the sensor resistance change ratio exceeds the sensor abnormality determination value, the sensor abnormality determination circuit 16 determines that the sensor sensitivity has deteriorated and determines that the gas sensor 1 is abnormal (step S21).

The alarm circuit 18 drives the buzzer 19 and the LED 21 in response to the abnormality judgment signal from the alarm judgment circuit 14, and issues an alarm with the buzzer 19 and the LED 21 (step S23). At this time, the LED 21 blinks at a constant cycle.

On the other hand, the alarm determination circuit 14
It is determined whether or not the gas concentration of carbon monoxide based on the gas sensor input from the sensor exceeds a predetermined CO alarm point. If the gas concentration of carbon monoxide exceeds the CO alarm point, an alarm determination circuit 14 Outputs an alarm signal to the alarm circuit 18, and the alarm circuit 18 includes a buzzer 19 and the LED 2
An alarm is issued by 1.

As described above, according to the gas alarm device and the gas alarm method of the embodiment, the sensor resistance value at the time of cleaning the gas sensor 1 is detected, and the sensor resistance value becomes about 3 to 5 times the initial sensor resistance value. If deteriorated, the gas sensor 1
Is notified in advance that the sensitivity of the gas sensor 1 has deteriorated, so that it is easily known that the gas sensor 1 has deteriorated.

Further, since one LED 21 can be used to display an abnormal display of the gas sensor 1 and an abnormal display of the concentration of carbon monoxide, the number of LEDs can be reduced, and the gas alarm can be made more inexpensive. .

The sensor abnormality determination circuit 16a as shown in FIG. 2 determines whether the sensor voltage value based on the sensor resistance value detected by the sensor detection circuit 9 exceeds the sensor abnormality determination voltage value. When the value exceeds the sensor abnormality determination voltage value, it is easily determined that the gas sensor 1 has deteriorated by determining that the gas sensor 1 is abnormal.

The present invention is not limited to the gas alarm of the embodiment described above. In the embodiment,
The LED 21 blinks to warn of an abnormality of the gas sensor 1 and the LED 21 lights up to display an abnormality of the concentration of carbon monoxide. For example, by changing the blinking period of the LED 21, the abnormality of the gas sensor 1 may be reduced. An abnormality in the concentration of carbon oxide may be identified.

In the embodiment, the on-drive period is set to 0.8 seconds, and the off-drive period is set to 200 seconds. However, the present invention is not limited to this period. The off-drive period may be set to be sufficiently longer than the period. In addition, it goes without saying that various modifications can be made without departing from the technical idea of the present invention.

[0057]

According to the first aspect of the present invention, the detecting means comprises:
When the sensor resistance value of the sensor element is detected during the ON drive period of the gas sensor every predetermined cycle, the abnormality determination unit determines the abnormality of the gas sensor based on a change in the plurality of sensor resistance values detected by the detection unit, and the notification unit In addition, when the abnormality determination unit determines that the gas sensor is abnormal, an alarm indicating the abnormality of the gas sensor is notified, so that it is easily understood that the sensitivity of the gas sensor has deteriorated.

According to the second aspect of the present invention, the abnormality judging means detects the sensor resistance between the initial sensor resistance value detected in the first ON driving period and the sensor resistance value detected in the second and subsequent ON driving periods. When the change ratio exceeds a predetermined determination value, it is determined that the sensitivity of the gas sensor has deteriorated, so that it is easily known that the sensitivity of the gas sensor has deteriorated.

According to the third aspect of the present invention, the notifying means identifies and notifies an alarm indicating an abnormality in the concentration of carbon monoxide gas and an alarm indicating an abnormality in the gas sensor. It is possible to easily identify whether the gas sensor is abnormal.

According to the fourth aspect, the same effect as the effect of the first aspect is obtained, and according to the fifth aspect, the same effect as the second aspect is obtained. According to the sixth aspect of the invention, the same effect as that of the third aspect of the invention can be obtained.

[Brief description of the drawings]

FIG. 1 is a basic circuit configuration diagram of a battery-operated gas alarm of an embodiment.

FIG. 2 is a specific circuit configuration diagram of the battery-operated gas alarm of the embodiment.

FIG. 3 is a timing chart of a pulse drive signal in the battery-operated gas alarm of the embodiment.

FIG. 4 shows a relationship between a sensor resistance change ratio and a CO alarm concentration after a high-temperature and high-humidity acceleration test in which a gas sensor in a battery-operated gas alarm of the embodiment is periodically heated up in a high-temperature and high-humidity environment. FIG.

FIG. 5 is a flowchart showing a gas alarm method realized by the gas alarm device of the embodiment.

FIG. 6 is a timing chart of the temperature of a gas sensor driven by a pulse drive signal in a conventional gas alarm device.

FIG. 7 is a diagram showing the aging characteristics of a conventional battery-operated gas alarm.

FIG. 8 is a diagram showing the results of a high-temperature, high-humidity continuous leaving test of a conventional battery-operated gas alarm.

FIG. 9 is a timing chart showing sensor driving conditions in a conventional high temperature and high humidity continuous test of a battery-operated gas alarm.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gas sensor 2 Heater 3 Sensor element 5 Battery 7 Power supply circuit 9 Sensor detection circuit 11 CPU 12 Battery power detection circuit 13 Sensor drive circuit 14 Alarm judgment circuit 15 Memory 16 Sensor abnormality judgment circuit 18 Alarm circuit 19 Buzzer 21 LED Q1, Q2 Detection point

Continued on the front page (72) Inventor Hiromasa Takashima 23 Minamikashima, Futamata-machi, Tenryu-shi, Shizuoka Yazaki Keiki Co., Ltd. (72) Inventor Akira Omura 23 Minamikashima, Futamata-cho, Tenryu-shi, Shizuoka 23 Person Satoshi Nagata 23 Minamikashima, Futamata-machi, Tenryu-shi, Shizuoka Prefecture Inside Yazaki Keiki Co., Ltd. (72) Inventor Hiroshi Nakae 1-5-20 Kaigan, Minato-ku, Tokyo Inside Tokyo Gas Co., Ltd. (72) Inventor Taeko Honjo Minato Tokyo 1-5-20, Kaigan-ku, Tokyo Tokyo Gas Co., Ltd. (72) Inventor Shinichi Matsumoto 2-26, Hachizuka, Ikeda-shi, Osaka Prefecture Inside FFA Yes Co., Ltd. (72) Kazuo Onaga, 2-chome Hachizuka, Ikeda-shi, Osaka 5-26 FFA Yes Co., Ltd. F term (reference) 2G046 AA11 BE04 DA05 DB02 DB04 DC11 DC12 DC14 DC16 DC17 DC18 DD01 EB04 FB02 2G060 AA03 AB08 AE19 AE27 AF04 AF07 BA01 BB02 BB09 HA03 HA07 HB03 HB05 HC08 HC15 HC02 HD01 HD01 KA01 5C087 AA14 AA23 AA32 AA42 CC02 CC48 DD07 EE16 FF01 FF04 FF13 G G08 GG21 GG23 GG30 GG31 GG37 GG55 GG66

Claims (6)

[Claims] 1. A gas sensor having a heater and a sensor element is alternately turned on and off at a predetermined cycle by a pulse drive signal, and a carbon monoxide gas concentration is detected during an off drive period of the gas sensor. A gas alarm device for notifying an alarm indicating an abnormality in the concentration of carbon monoxide gas when the detected concentration of carbon monoxide gas is equal to or higher than an alarm point; Detecting means for detecting a sensor resistance value of the element; abnormality determining means for determining an abnormality of the gas sensor based on a change in a plurality of sensor resistance values detected by the detecting means; and determining that the gas sensor is abnormal by the abnormality determining means. Notification means for notifying an alarm indicating an abnormality of the gas sensor when the determination is made. 2. The abnormality determination means according to claim 1, wherein a sensor resistance change ratio between an initial sensor resistance value detected in a first on-drive period and a sensor resistance value detected in a second and subsequent on-drive periods. 2. The gas alarm according to claim 1, wherein it is determined that the sensitivity of the gas sensor has deteriorated when a predetermined determination value is exceeded. 3. The gas according to claim 1, wherein the notifying means identifies and notifies an alarm indicating an abnormality of the carbon monoxide gas concentration and an alarm indicating an abnormality of the gas sensor. Alarm. 4. A gas sensor having a heater and a sensor element is alternately turned on / off at a predetermined cycle by a pulse drive signal, operating on a power supply voltage of a battery, and detecting a carbon monoxide gas concentration during an off drive period of the gas sensor. A gas alarm method for notifying an alarm indicating an abnormal carbon monoxide gas concentration when the detected carbon monoxide gas concentration is equal to or higher than an alarm point, wherein the sensor is turned on during the on-drive period of the gas sensor at every predetermined cycle. A detecting step of detecting a sensor resistance value of the element; an abnormality determining step of determining an abnormality of the gas sensor based on a change in the plurality of detected sensor resistance values; and an abnormality of the gas sensor when the gas sensor is determined to be abnormal And a notifying step of notifying an alarm indicating the following. 5. The abnormality determination step according to claim 1, wherein the initial sensor resistance value detected during the first on-drive period and a value of 2
The sensitivity of the gas sensor is determined to be deteriorated when a sensor resistance change ratio with respect to the sensor resistance value detected in a subsequent ON drive period exceeds a predetermined determination value. Gas alarm method. 6. The gas according to claim 4, wherein the notification step identifies and notifies an alarm indicating an abnormality in the concentration of carbon monoxide gas and an alarm indicating an abnormality in the gas sensor. Alarm method.