JP6454978B2 - Battery-powered gas alarm and its control device - Google Patents

Description

  The present invention relates to a gas leak alarm device that issues a warning by detecting a combustible gas such as city gas or LP gas leaked from a gas appliance or gas pipe, and more particularly to a battery-type gas alarm device using a battery as a power source.

2. Description of the Related Art A gas alarm device that detects a gas leak from a gas appliance or a gas pipe and notifies the user of the gas leak by issuing an alarm with a voice or a buzzer is known.
The gas alarm device detects a detection target gas by a gas detection element such as a gas sensor, and issues a warning by an alarm sound or a warning display when the gas concentration of the detection target gas exceeds a predetermined value (threshold value).

  In the gas alarm device, a gas sensor is used to detect a detection target gas such as city gas or LP gas. The gas sensor has, for example, a heater resistance and a sensor resistance. The resistance value of the sensor resistance changes due to the reaction with the detection target gas. Gas detection is performed by measuring the resistance value of the sensor resistance while being heated by the heater resistance. For example, a voltage is applied to the heater resistance of the gas sensor and the temperature is heated to a predetermined temperature such as 400 ° C., and the resistance value of the sensor resistance is measured (actually, a voltage or the like indicating this resistance value is used). Gas is detected.

  There are two methods of driving the heater resistance of the gas sensor to a predetermined temperature: a method of applying a DC voltage or a method of applying a voltage in a pulsed manner. In order to reduce this, a method of applying a pulse current to the heater at a predetermined drive cycle is performed (Patent Document 1, Patent Document 2).

  In addition, a battery-operated gas alarm device is desired for reasons such as improved installation by cordlessness and downsizing of the device, but the heater temperature of the gas sensor must be about 400 ° C. when detecting the detection target gas. , Big power is needed. For this reason, it is a subject to drive the sensor with power saving so that the battery alarm can be driven for 5 years, which is the expiration date of the gas alarm device.

  The battery-type gas alarm device needs to be operable for 5 years or more without replacing the battery. For this reason, it is necessary to lengthen the sensor drive cycle to some extent, for example, as shown in FIG. 9, it is necessary to set the sensor drive cycle to 45 seconds or the like.

FIG. 9 shows an example of sensor driving by pulse energization.
In the illustrated example, pulse energization is performed on the gas sensor for 100 ms every 45 seconds of the sensor driving cycle, and gas detection (measurement of sensor resistance value) is performed at the final timing of pulse energization. In order to save power, the pulse energization time (voltage application time to the gas sensor; 100 ms in this example) is shortened and the drive cycle is lengthened (45 seconds).

  In a gas concentration test in a high-concentration (12500 ppm) gas, it is necessary to issue a warning by detecting a gas leak within 60 seconds from the occurrence (Patent Document 3). As described above, in the battery-driven gas alarm device, a method of applying a pulse with a predetermined drive cycle is performed for power saving. However, gas detection is performed only at a predetermined drive cycle timing, and gas is constantly generated. Since no detection is performed, when the sensor driving cycle is 45 seconds or the like, there is a case where a gas cannot be detected and an alarm cannot be issued within 60 seconds. However, in order to be able to operate for 5 years or more, the sensor driving cycle cannot be shortened (for example, always 20 seconds).

  The pulse energization to the gas sensor applies voltage to both the heater resistance and the sensor resistance.

JP 1999-248659 A Japanese Patent Laid-Open No. 2003-67867 JP 2010-86199 A

  As described above, in the battery-type gas alarm device, the gas detection operation is performed only at a predetermined drive cycle timing, and the gas detection at any time (always) is not performed. It has become difficult to detect gas early and issue an alarm without delay in detection time. In particular, when the sensor driving cycle is lengthened in order to drive the sensor with power saving, there is a case where it is not possible to “detect and issue an alarm within 60 seconds from the occurrence of gas leakage”. Note that this also has the effect that the battery life needs to be 5 years or longer as described above.

  Patent Documents 1 and 2 do not consider detection delay, and Patent Document 3 describes an example of pulse driving in a cycle of 20 seconds. However, battery consumption becomes very large. The above problem can be solved by shortening the drive period of pulse energization and increasing the gas detection timing. However, when the gas sensor is energized, a large amount of power is required to heat the heater to about 400 ° C. (For example, if the driving cycle of 45 seconds is changed to a 5-second cycle, the power consumed by the gas sensor will increase nine times).

  Therefore, in the battery-type gas alarm device, it is desired to make the drive period of pulse energization as long as possible, but if the drive period is too long, gas detection is delayed because gas detection is not performed except for the drive period timing, In spite of the fact that the alarm must be issued at an early stage, there is a problem that the alarm is delayed and the alarm cannot be performed in a safe state. For example, if the driving cycle of 45 seconds is changed to a 90-second cycle, the power consumed by the gas sensor is halved, but since the gas is detected only every 90 seconds, the gas concentration greatly increases during 90 seconds. In such a case, there is a possibility that the gas detection is performed after greatly exceeding the gas concentration that is originally desired to be detected, which causes a safety concern.

  In addition, the gas concentration inside the gas sensor for detecting the surrounding gas concentration is immediately affected by the structure of the alarm unit, the gas sensor structure, the filter configuration provided to remove miscellaneous gases, etc. It is not the same as the gas concentration, and gradually approaches the ambient gas concentration. Therefore, the sensor driving cycle must be determined in consideration of the detection delay of the gas concentration due to the structure of such an alarm device.

  An object of the present invention is to provide a battery-type gas alarm device that uses a battery as a power source, and is capable of generating a gas leak alarm early without delaying detection of a detection target gas while realizing power saving and suppressing battery consumption. High battery-powered gas alarm, its control device and the like.

The battery-type gas alarm device of the present invention is a battery-type gas alarm device using a battery as a power source, which detects gas leakage based on the output of a gas sensor whose electrical characteristics change according to the gas concentration of the detection target gas, Each of the following configurations is included.
Means for driving the gas sensor by energizing the pulse with an arbitrary driving cycle, and normally the sensor driving unit for driving the gas sensor with the first driving cycle;
A sensor resistance value calculating means for obtaining a resistance value of the gas sensor based on an output of the gas sensor when the sensor is driven;
A previous value storage means for storing the sensor resistance value obtained by the sensor resistance value calculation means at the time of the previous sensor drive as a previous value;
Determination means for determining whether or not the gas concentration has increased based on the current value, which is the sensor resistance value obtained by the sensor resistance value calculation means, and the previous value;
Drive period changing means for causing the sensor driving means to drive the gas sensor at a second drive cycle shorter than the first drive cycle when the determination means determines that the gas concentration has increased.

Then, the determining means, said current value and on the basis of the ratio of the previous value with a predetermined threshold value, determines whether the gas concentration increases.

  According to the battery-type gas alarm device of the present invention, its control device, etc., in the battery-type gas alarm device using a battery as a power source, it achieves power saving and suppresses battery consumption, while preventing a sudden increase in gas concentration. In addition, a gas leak warning can be issued early without any detection delay.

It is a block diagram of the gas alarm device of this example. It is a time chart figure of sensor drive in one embodiment. It is a process flowchart figure which determines the sensor drive period by one Embodiment. It is a figure which shows the relationship between gas concentration and elapsed time. It is a figure which shows the relationship between the gas concentration and elapsed time by one Embodiment. It is a figure which shows the relationship between a sensor resistance value and gas concentration. It is a time chart figure of sensor drive in a modification which does not perform S14 and S15. It is a functional block diagram of the gas alarm device of this example. It is a figure explaining the sensor drive timing of the conventional battery-type gas alarm device.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram of the gas alarm device of this example.
The illustrated gas alarm 10 is a gas leak alarm that emits an alarm by detecting a flammable gas such as city gas or LP gas leaked from a gas appliance or gas pipe, and is particularly a battery-operated gas powered by a battery. It is an alarm.

  The illustrated gas alarm device 10 includes a gas sensor 11, a control circuit unit 12, an alarm unit 13, an ambient temperature detection unit 14, a battery unit 15, and the like, and further includes a load resistor R, a transistor switch SW1, a transistor switch SW2, and the like. Circuit. Hereinafter, the transistor switch SW1 and the transistor switch SW2 are omitted, and are referred to as a switch SW1 and a switch SW2.

  The gas sensor 11 for detecting the detection target gas includes a sensor resistor 11a for detecting a gas concentration and a heater resistor 11b for heating the sensor resistor 11a. As already described in the related art, the sensor resistance 11a has a resistance value corresponding to the concentration of the surrounding gas, and the heater resistance 11b is set to, for example, 400 ° C. during the gas leak detection process performed in the predetermined driving cycle. In this state, the resistance value of the sensor resistor 11a (voltage value corresponding to the resistance value) is measured. The detection target gas may be city gas, LP gas, or other gas, but a gas sensor corresponding to the type of detection target gas is used.

  The battery unit 15 supplies a 3 volt power source in this example, and serves as a power supply source for the entire circuit shown in FIG. That is, the voltage from the battery unit 15 is supplied to a sensor system circuit which is a gas detection means including a heater resistor 11b and a sensor resistor 11a in the gas sensor 11, a load resistor R, switches SW1 and SW2, and the like. Further, power is also supplied from the battery unit 15 to the control circuit unit 12. Here, the power supply to the sensor system circuit and the control circuit unit 12 may be supplied from a configuration (such as a stabilized power source not shown) that boosts or lowers the voltage from the battery unit 15.

  Further, as shown, a series circuit (first series circuit) in which the switch SW2, the sensor resistor 11a, and the load resistor R are connected in series, and a series in which the switch SW1 and the heater resistor 11b are connected in series. A circuit (second series circuit) is provided in parallel. A power supply voltage (3 V) from the battery unit 15 is applied to each series circuit.

  The control circuit unit 12 is a microcomputer (CPU or the like) that controls the operation of the gas alarm device 10 as a whole. By executing a program stored in advance in a built-in memory (not shown), the control processing unit 12 will be described later. The process of the flowchart shown in FIG. 3 etc. are performed.

  The control circuit unit 12 has output terminals OUT1, OUT2, input terminals AD1, AD2, and the like. The output terminal OUT1 is connected to the base of the switch SW1, and the switch SW1 is ON / OFF controlled by the output from the output terminal OUT1. The output terminal OUT2 is connected to the base of the switch SW2, and the switch SW2 is ON / OFF controlled by the output from the output terminal OUT2.

  A voltage V1 between the sensor resistor 11a and the load resistor R is input to the input terminal AD1. When the switch SW2 is ON, the voltage V1 is obtained by dividing the voltage applied to the first series circuit by the battery unit 15 by the sensor resistor 11a and the load resistor R. The resistance value of the load resistor R may be arbitrary, but is fixed. When the resistance value of the sensor resistor 11a changes, the voltage value V1 changes. That is, the voltage value V1 indicates the resistance value of the sensor resistor 11a.

  The input terminal AD1 includes not only the input terminal but also a function (AD converter) for converting an analog signal (voltage value V1 or the like) input to the input terminal into a digital value. Therefore, the control circuit unit 12 inputs the digital value of the voltage value V1 through the input terminal AD1.

  In the gas leak detection process performed in the predetermined driving cycle, the control circuit unit 12 turns on the switch SW1 and the switch SW2 by the output from the output terminals OUT1 and OUT2, thereby causing the gas sensor 11 (the heater resistor 11b, The sensor system circuit including the sensor resistor 11a) and the load resistor R is operated by supplying power. That is, driving of the gas sensor 11 is started.

  By supplying power to the heater resistor 11b, the heater resistor 11b is brought into a high temperature state of about 400 ° C., for example. Although not particularly illustrated, the sensor resistor 11a is disposed near the heater resistor 11b, and the resistance value of the sensor resistor 11a is measured at a high temperature of about 400 ° C. Actually, as described above, the voltage V1 is input and converted to the resistance value of the sensor resistor 11a (referred to as the sensor resistance value). This is an existing technology and will not be described in particular.

In a situation where there is a gas such as city gas (methane gas), the sensor resistance value (in other words, the voltage V1) changes according to the gas concentration. That is, as the gas concentration increases, the sensor resistance value decreases, and thus the voltage V1 increases. For example, as shown in FIG. 6 described later, the sensor resistance value decreases as the gas concentration increases. For example, in the state where there is almost no methane gas (gas concentration = 10 [ppm] ) , the sensor resistance value exceeds “1.E + 05” (Ω), but the alarm level is high (gas concentration = 10000 [ppm] ). In this state, the sensor resistance value is lower than “1.E + 04” (Ω).

  The control circuit unit 12 measures the sensor output (voltage value V1; corresponding to the resistance value of the sensor resistor 11a) of the gas sensor 11 via the input terminal AD1, and for example, the sensor output (voltage V1) has a predetermined gas concentration (described later). If the value corresponding to the alarm reference concentration (alarm level) to be exceeded is exceeded, in other words, if the sensor resistance value is less than the value corresponding to the predetermined gas concentration, it is determined that a gas leak has occurred. In this way, gas leak detection is performed. Of course, the present invention is not limited to this example. For example, when the voltage V1 is converted into a resistance value of the sensor resistor 11a and this sensor resistance value becomes less than a value corresponding to the alarm reference concentration, it is determined that gas leakage has occurred. May be. Such a gas leak detection function itself is an existing function.

  In this way, if the gas concentration becomes a high concentration of the above alarm level, an alarm is issued by the existing function, but in this method, it is determined that there is a possibility of gas leakage at an earlier stage. Thus, the sensor drive cycle is temporarily switched to a short cycle (20 seconds) to prevent a gas leak detection delay. Note that the short cycle may basically be any cycle as long as it is shorter than the normal drive cycle (45 seconds in this example), and is 20 seconds as an example here, but is not limited to this example.

  The control circuit unit 12 stores the sensor resistance value measured last time in a storage unit (not shown) such as a RAM in the control circuit unit 12. Then, the sensor resistance value (current value) measured this time and the stored data (previous value) are used to perform processing such as determination of change in the sensor driving cycle. Details will be described later. A sensor output (voltage V1)) or the like may be used instead of the sensor resistance value. However, in this description, an example using a sensor resistance value is basically used.

  The alarm unit 13 includes an alarm sound output unit 13a, an alarm display unit 13b, and an external alarm output unit 13c. The alarm sound output unit 13a is a part that emits a sound such as an alarm sound, and includes, for example, a speaker or a buzzer. Based on the control from the control circuit unit 12, the alarm sound output unit 13a notifies the gas leak state by a voice message or an electronic sound. The alarm display unit 13b is configured by an LED (light emitting diode) or the like, and at the time of an alarm, the LED is blinked or turned on to display an alarm state with the LED to notify a gas leakage state. The external alarm output unit 13c outputs an alarm signal to an external device such as a gas meter or a central monitoring panel at the time of alarm.

  The ambient temperature detection unit 14 is not related to the present invention and will not be described in detail. However, the ambient temperature value is input to the control circuit unit 12 via the input terminal AD2, and the control circuit unit 12 sets the ambient temperature to the ambient temperature. This is a configuration for performing temperature correction calculation of the gas concentration based on it.

The circuit configuration itself shown in FIG. 1 may be regarded as the same as the conventional one. What is different from the prior art is the content of the control processing by the control circuit unit 12, which will be described in detail later.
Here, sensor driving according to this example will be described below with reference to the time chart of FIG.

  The control circuit unit 12 performs gas detection for each cycle Ta by driving the gas sensor 11 with the sensor drive cycle Ta and the sensor drive time Tb (corresponding to the pulse energization time). The sensor driving cycle Ta and the sensor driving time Tb basically use values set in advance, and here, as an example, Ta = 45 seconds and Tb = 100 ms (milliseconds). This value is determined and set arbitrarily by a developer, for example.

  However, in this method, the sensor driving cycle Ta and the sensor driving time Tb may be temporarily changed. Here, as an example, it may be temporarily changed to Ta = 20 seconds and Tb = 200 ms. As described above, in this description, as an example, sensor driving (gas detection) is performed at a period of 45 seconds under normal conditions. However, when the situation satisfies a predetermined condition, the period is temporarily short (20 seconds). In some cases, the sensor is driven. Details will be described later.

  In the present embodiment, as described above, the gas sensor 11 is driven at a normal time, for example, with a sensor driving cycle Ta = 45 seconds and a sensor driving time Tb = 100 ms (milliseconds). Specifically, the following operation is executed for each sensor driving cycle Ta based on control by an internal timer (not shown) of the control circuit unit 12.

  The control circuit unit 12 turns on the switch SW1 and the switch SW2 by the output from the output terminals OUT1 and OUT2 each time the sensor drive start timing according to the sensor drive cycle Ta is reached, so that the heater resistor 11b and the sensor in the gas sensor 11 are turned on. A power supply voltage is applied to the resistor 11a. The heater resistor 11b is heated to, for example, 400 ° C. by applying a power supply voltage.

  The control circuit unit 12 reads the gas sensor output (voltage V1) via the AD1 terminal when 100 ms has elapsed from the start of the sensor driving. Note that the elapse of 100 ms is determined by, for example, an internal timer (not shown). This operation itself is the same as in the prior art. In the past, the acquired voltage V1 was converted into a gas concentration. In this method, in addition to this, it is determined whether there is a possibility of gas leakage. To do. For example, the voltage V1 is converted into a sensor resistance value, and a process of determining whether or not (abrupt) gas concentration has risen is performed using this value and the previous value.

  That is, the control circuit unit 12 converts the gas sensor output (voltage V1) when 100 ms has elapsed into a sensor resistance value, which is used as the current sensor resistance value. The sensor resistance value obtained in the previous sensor drive is stored as the previous sensor resistance value. From this, based on these current sensor resistance values and the previous sensor resistance value, a process of determining whether or not (abrupt) gas concentration has risen is performed. As an example, an example of determination using the ratio of these two sensor resistance values will be described below.

  That is, as an example, when the ratio of the sensor resistance value (= previous sensor resistance value / current sensor resistance value) is equal to or greater than a predetermined threshold value (in this example, “2”), It is determined that there has been a (rapid) increase in gas concentration. This determination process is performed when “the ratio of the sensor resistance value is“ current sensor resistance value / previous sensor resistance value ”and is less than a predetermined threshold value (eg,“ 0, 5 ”) ( It is synonymous with “determining that there has been a sudden increase in gas concentration”. Further, the present invention is not limited to such an example of using “ratio”, and processing similar to this may be used. For example, “difference” may be used. Basically, anything can be used as long as it can be considered that there has been a (rapid) increase in gas concentration based on some previous value and this value.

  As described above, this description shows an example of the process, and the present invention is not limited to the example. At least the process that is synonymous with the example and may be regarded as substantially the same is the present invention. Is included. The same applies to the description of other processes.

  Further, the control circuit unit 12 converts the sensor output (voltage V1) when 100 ms elapses into a gas concentration, and if this gas concentration exceeds a predetermined threshold (alarm reference concentration; alarm level), an alarm is issued. It is determined that there is a gas leak condition to be performed.

  Note that the process itself for converting the sensor output (voltage V1) into the gas concentration and the sensor resistance value is an existing general one, and is not particularly described here. Further, since the process itself for comparing and determining the converted gas concentration (measured gas concentration) with a predetermined alarm level is an existing technology, it will not be described in detail.

In this method, the sensor resistance value obtained when the previous sensor is driven is stored in the storage unit such as a memory (not shown) of the control circuit unit 12 as the previous sensor resistance value (previous value). The sensor resistance value (current value) obtained when the sensor is driven is used to determine whether or not there has been a (sudden) change in gas concentration.

  In this description, as an example, if the “previous value / current value” (ratio of the previous and current sensor resistance values) is equal to or greater than a predetermined threshold (“2” in this example), the (rapid) gas concentration Assuming that there has been a change, as described above, the mode is temporarily shifted to a mode in which the sensor is driven with a short cycle (20-second cycle).

Note that pulse energization (application of a voltage of 100 ms or the like) is performed when the sensor is driven.
Here, the “gas concentration” column in FIG. 2 shows specific examples of the alarm reference concentration and the measured gas concentration. In the “sensor resistance value” column, “sensor drive” column, and “alarm display” column in FIG. 2, the sensor resistance value, sensor drive cycle and pulse energization time, notification / The notification timing is shown.

  In the example shown in FIG. 2, a (rapid) increase in gas concentration starts between N (-1) and N (0) shown in the figure, and here, at the time of N (0) shown here, the sensor It is assumed that the resistance value ratio is determined to be equal to or greater than a predetermined value (= 2). Thus, at the time of N (0), the sensor driving cycle Ta is changed to a short cycle (20 seconds) and the pulse energization time Tb is changed to 200 ms. Note that the pulse energization time Tb is not necessarily changed. Therefore, in this description, there is a case where there is no particular description about the change of the pulse energization time Tb. The sensor driving cycle Ta is changed so as to be shorter than the normal sensor driving cycle (= 45 seconds). In this example, for example, Ta = 20 seconds. However, the present invention is not limited to this example.

  Note that the method for detecting an increase in gas concentration is not limited to the above example. For example, a difference between sensor resistance values (previous sensor resistance value−current sensor resistance value) may be used. In this case, a threshold corresponding to the difference is set in advance, and when the calculated difference is less than the threshold, it is considered that the gas concentration has increased (the gas concentration has increased rapidly), and the sensor drive cycle May be changed to a short period (20 seconds).

  Further, determination of an increase in gas concentration or the like may be performed using a sensor output (voltage V1) or a converted gas concentration instead of the sensor resistance value. However, since the voltage V1 and the gas concentration may be considered to substantially correspond to the sensor resistance value, “use the sensor resistance value” is not limited to the case where the sensor resistance value is used, but the voltage V1 and the gas concentration. The case where is used is also included.

If the measured gas concentration exceeds the alarm reference concentration after detecting the gas concentration increase, the alarm unit 13 is controlled to perform a gas leak notification operation as in the conventional case.
Hereinafter, further description will be given using a specific example shown in FIG.

  In the following description, an example using the ratio of the sensor resistance value (previous value / current value) will be described. However, as described above, the present invention is not limited to this example. For example, the difference between the previous value and the current value is used. May be.

  In the example shown in FIG. 2, the sensor resistance is not detected in the gas detection in the state where there is no detection target gas such as methane gas, that is, the gas detection from the first time (N (-3)) to the third time (N (-1)). The value hardly changes. Therefore, the ratio of the sensor resistance value (= previous sensor resistance value / current sensor resistance value) is almost “1” in any of N (−3), N (−2), and N (−1). is there.

  Thus, for example, when N (−2), the sensor resistance value at N (−3) is the previous value, but since the previous value is almost the same as the current value, the ratio of these is almost “1”. . Therefore, the determination result as to whether or not the “previous value / current value” is equal to or greater than a predetermined threshold (= 2) is NO, and the 45-second cycle is continued.

  Similarly, when N (−1), the sensor resistance value at N (−2) is the previous value, but since the previous value is almost the same as the current value, the ratio thereof is almost “1”. . Accordingly, in this case as well, the determination result is NO, and the 45-second cycle is continued.

  Thus, if the current sensor resistance value has hardly changed compared to the previous sensor resistance value, it is considered that the possibility of gas leakage is low, and the sensor drive cycle Ta is also 45 seconds. Will continue.

  When the gas concentration rises slowly, the “previous value / present value” should be less than the predetermined threshold (= 2) even if the gas concentration itself increases to some extent. This is not limited to the example using the “ratio”, and the same applies to the example using the “difference”. However, when the gas concentration rises slowly, there is no particular problem even if the sensor driving cycle Ta remains 45 seconds.

  Here, at the time of the fourth gas detection process (N (0)) in FIG. 2, the gas concentration rapidly increases as shown in the figure, so that the sensor resistance value this time is compared with the previous value. It is assumed that the “previous value / current value” becomes equal to or greater than a predetermined threshold (= 2). From this, it is determined that there is a (rapid) increase in gas concentration, and therefore, the mode is temporarily switched to a mode that is driven for a short period (20 seconds). That is, the sensor driving cycle Ta and the sensor driving time Tb are changed (in this example, the sensor driving cycle Ta is changed from the 45-second cycle in the normal state to the 20-second cycle). In the example of FIG. 2, at the time of (N (0)), since the measured gas concentration does not exceed the alarm reference concentration that is the alarm level concentration, no gas leak alarm is performed.

Hereinafter, the fifth and subsequent times shown in FIG. 2 will be described.
In addition, the following description after the fifth time shall apply to the processing example of the flowchart figure mentioned later. That is, it is determined whether or not the measured gas concentration exceeds the alarm reference concentration, and if it exceeds, a gas leak alarm is issued and the sensor drive cycle Ta is returned to the normal cycle (45 seconds in this example). To do. In addition, the number of gas detection processes executed with the sensor driving cycle Ta set to a short cycle (20-second cycle in this example) while the measured gas concentration does not exceed the alarm reference concentration is a predetermined number (5 in this example). ), The sensor drive cycle Ta is returned to the normal cycle (45 seconds in this example). However, it is not restricted to these examples. For example, the elapsed time may be used instead of the “number of times”. That is, if the measured gas concentration does not exceed the alarm reference concentration even after a predetermined time has elapsed since the start of short cycle driving, the sensor driving cycle Ta may be returned to the normal cycle.

In the following description, the change of the sensor driving time Tb is not mentioned.
In the example of FIG. 2, the gas detection process (N (1)) for the fifth time has a short period (in this example, the sensor drive cycle Ta) in the gas detection process (N (0)) for the fourth time as described above. It is implemented 20 seconds after the fourth gas detection. In the example shown in FIG. 2, at this time, since the measured gas concentration is equal to or lower than the alarm reference concentration, no gas leak alarm is issued. Further, since the number of gas detection processes in the short cycle (= first time) is less than the predetermined number (5 times), the sensor driving cycle Ta = 20 seconds is continued.

  Subsequently, in the sixth gas detection process (N (2)), the measured gas concentration rises and exceeds the alarm reference concentration, which is the alarm level concentration. Display. Further, when the gas leakage alarm is performed, the intended early gas detection is satisfied, the sensor drive cycle Ta is returned to the normal 45-second cycle, and the gas detection process is continued in the normal cycle. Thus, as shown in the drawing, the seventh (N (3)) and subsequent gas detection processing returns to the normal cycle.

  As described above, the gas alarm device 10 of the present example is short-cycle when detecting a (rapid) gas concentration rise while realizing power saving by suppressing the battery consumption by periodically operating for 45 seconds. By changing to the (20-second cycle) sensor driving operation, gas leakage can be detected early without detection delay, and a highly reliable gas alarm can be provided.

  Further, although not shown in the time chart of FIG. 2, “measured gas concentration <alarm reference concentration” (in FIG. 3) is continuously performed a predetermined number of times (in this example, five times) after detecting a (rapid) increase in gas concentration. If NO in step S2, in other words, if the gas concentration does not exceed the alarm reference concentration even after a predetermined time has elapsed since the start of short cycle driving, the increase in gas concentration is gradual and the urgency is Therefore, it is possible to stop the sensor driving cycle at the 20-second cycle and return it to the 45-second cycle that is the normal sensor driving cycle to suppress wasteful power consumption.

It should be noted that the number of detections and the value of the short cycle may be determined by the developer or the like as appropriate values depending on the gas concentration change to be detected, and are not limited to the above values (5 times or 20 seconds). Absent.
FIG. 3 is a flowchart of the gas leak detection process of this example.

  The processing in the flowchart is repeatedly executed by the control circuit unit 12 (microcomputer or the like) in FIG. 1 every time the sensor driving is executed (in a Ta cycle). Of course, the sensor to be driven is the gas sensor 11.

  First, the control circuit unit 12 in FIG. 1 performs sensor driving for the sensor driving time Tb in the sensor driving cycle Ta based on control by an internal timer (not shown), and at the end of sensor driving (when 100 ms elapses), The sensor output (voltage V1) of the gas sensor 11 is read through the input terminal AD1 (step S1). However, when extending the sensor drive time (pulse energization time), the pulse energization time is extended to 200 ms from the start, and the sensor output (voltage V1) at the end, that is, when 200 ms elapses from the start is read. .

  Note that the timing of reading the sensor output (voltage V1) is not limited to the end of sensor driving (when 100 ms elapses or 200 ms elapses in the case of extension), but is an arbitrary timing during sensor driving. Good. However, since the sensor output is unstable immediately after the start of sensor driving, it is desirable to read the sensor output (voltage V1) in a state where the sensor output is stable. In other words, for example, the sensor output (voltage V1) may be read at an arbitrary timing after 60 ms has elapsed from the start of sensor driving. However, the present invention is not limited to this example.

In addition, as described above, in this example, Ta in the normal time is 45 seconds and Tb is 100 ms. However, this is an example, and the present invention is not limited to this example.
In step S1, the control circuit unit 12 further calculates a measured gas concentration and a sensor resistance value from the read voltage V1. Normally, the measurement gas concentration or the like is calculated using the sensor output (voltage V1) when the 100 ms has elapsed, but in the case of extension, the measurement gas concentration or the like is calculated using the sensor output (voltage V1) when the 200 ms has elapsed. Is calculated.

  Here, whether or not to extend the pulse energization time is determined with reference to an extension flag described later. That is, for example, when the extension flag described later is set to ON because the process of step S9 described later is executed in the previous or previous main process, the pulse energization time is extended.

  Even if the extension flag is OFF, the pulse energization time may be extended if a predetermined condition is met. The predetermined condition is, for example, a case where the sensor output (voltage V1) when 100 ms has elapsed is equal to or greater than a predetermined threshold. In other words, the gas concentration is higher than a certain level.

  Next, it is determined whether or not the current gas concentration (measured gas concentration) calculated in step S1 is equal to or higher than an alarm reference concentration which is an alarm level (measurement gas concentration ≧ alarm reference concentration) (step S2). The alarm reference concentration is set to an arbitrary value in advance.

  When the measured gas concentration value is equal to or higher than the alarm reference concentration (step S2, YES), a short cycle operation flag to be described later is cleared (step S14), and the sensor drive cycle Ta is set to a normal cycle (45 seconds in this example). ) (Step S15), a predetermined alarm process is performed (step S16), and this process is terminated. The process in step S16 is an alarm process by the alarm unit 13 described above.

  Basically, before the step S2 becomes YES, a “process for setting the sensor driving cycle Ta to a short cycle (20 seconds in this example)” to be described later is to be performed. The above-mentioned short-cycle operation flag indicating that there should be is supposed to be ON. That is, the processes in steps S14 and S15 can be said to be processes for returning from the short cycle operation mode to the normal mode as the alarm process is executed.

Note that step S2 also means that the short-cycle operation is not started when the gas concentration rapidly increases and the first measured gas concentration value becomes equal to or higher than the alarm reference concentration.
If the measured gas concentration is less than the alarm reference concentration (step S2, NO), it is determined whether or not the short-cycle operation is being performed (step S3). If the short cycle operation flag is ON, it is determined that the short cycle operation is in progress.

  If the short-cycle operation is being performed (step S3, YES), the determination of the gas concentration change (determination in step S4 to be described later) does not need to be performed again, and the process proceeds to step S6. During short cycle operation, the sensor drive cycle Ta is short (20 seconds) and the short cycle operation flag is ON. Thus, the determination in step S3 can be made by referring to the short cycle operating flag.

  When the short-cycle operation is not being performed (step S3, NO), the sensor resistance value (current value) calculated in step S1 and the sensor resistance value (previous value) calculated and stored in the previous main processing are stored. Based on the above, it is determined whether or not there is a (rapid) increase in gas concentration. As described above, an example in which “ratio” is used will be described here. Therefore, the above determination is performed using the ratio of the two resistance values (previous value / present value). That is, it is determined whether or not “previous value / current value” is equal to or greater than a predetermined threshold (= 2) (step S4).

  If “previous value / current value” is less than the predetermined threshold (= 2) (step S4, NO), it is determined that there is no (rapid) gas concentration increase, and the short-cycle operation flag is cleared (further, The counter value of a short cycle detection counter, which will be described later, may be initialized (= 0 or -1) (step S12), and the sensor drive cycle Ta is set to 45 seconds of normal drive (step S13). Further, the extension of the pulse energization time may be canceled and returned to the original 100 ms).

  And the process of step S10, S11 is performed and this process is complete | finished. That is, the sensor resistance value (current value) obtained this time is stored in a memory or the like as a new previous sensor resistance value (previous value) (step S10), and an alarm-free state (if an alarm is being issued, the alarm is canceled). ) (Step S11), the process is terminated.

  However, since the determination in step S4 is performed when the short cycle operation is not being performed (step S3, NO), the short cycle operation flag should be OFF and driven in a 45 second cycle. Therefore, the processing in steps S12 and S13 is not always necessary when step S4 is NO. Note that the processing in steps S12 and S13 is necessary when step S7 described later is YES.

  On the other hand, if the “previous value / current value” is equal to or greater than a predetermined threshold (= 2) (YES in step S4), it is assumed that there has been a (sudden) gas concentration increase, that is, gas leakage is possible. Assuming that there is a possibility, a process (step S8) for temporarily setting the sensor driving cycle Ta to a short cycle (20 seconds) and various processes (steps S5, S6, S9, etc.) related thereto are performed. Run.

That is, if the determination in step S4 is YES, a short cycle operation flag is set (step S5) to indicate that the short cycle operation is in progress.
Further, when the determination at step S3 is YES or when the determination at step S4 is YES, in other words, when the short cycle operation is being performed or when the short cycle operation is started, the short cycle detection counter is incremented by one. Up (step S6). Then, it is determined whether the count value of the short cycle detection counter is equal to or greater than a predetermined value (5 times in this example) (step S7).

  In step S6 when step S4 is YES, the short cycle detection counter counts up with the initial value (= 0 or -1), so the count value is '1' or '0'. It becomes. Thereafter, each time this process is executed, the determination in step S3 is YES (unless the determination in step S2 is YES), and the count is incremented by 1 in step S6. When the count value reaches a predetermined value (five times in this example) (step S7, YES), the processing of steps S12 and S13 is performed. However, if the determination in step S2 is YES before that, the processing in steps S14 to S16 is performed.

  If the count value of the short cycle detection counter becomes 5 or more without determining YES in step S2 (step S7, YES), the gas detection operation is already performed in the short cycle as much as necessary. Because of this (for the reasons already described), the processes of steps S12 and S13 are executed. That is, the short cycle operating flag is cleared (OFF) (step S12), and the sensor drive cycle Ta is returned to the 45 seconds cycle of normal drive (step S13). In the process of step S12, an extension flag described later may be further cleared (OFF).

  On the other hand, when the count value of the short cycle detection counter is less than 5 (step S7, NO), the sensor drive cycle is set to 20 seconds (if it is already 20 seconds, the detection in the short cycle is continued. (Step S8), the pulse energization time is extended (100 ms → 200 ms). For example, an extension flag (not shown) is turned ON (step S9). As a result, the pulse energization time is extended by the extension flag being ON in the processing of step S1 as described above in the main processing after the next time.

  Note that the extension of the pulse energization time is not limited to the above-described processing example. For example, processing that extends to 200 ms from the time when the short cycle operation start determination is performed as in the example shown in FIG. (Not shown / explained).

Then, the processes in steps S10 and S11 are performed, and this process is terminated.
Here, the reason why the pulse energization time is extended is to obtain the voltage V1 more stably, and in particular, in the case where the gas suddenly increases, if the pulse energization time is about 100 ms, the sensor This is because the consumption of negative charge adsorbed oxygen on the material surface is not sufficient and the sensor resistance value corresponding to the gas concentration may not decrease. Moreover, it is because the influence of miscellaneous gas other than detection object gas etc. can be excluded by extending to 200 ms.

  The period during which the pulse energization time is extended may be a short period (N (0), N (1), N (2) in FIG. 2), or the gas concentration is a predetermined value or more (alarm reference concentration or more or alarm) It may be the case of 1/2 or more of the reference density. Of course, both of them may be used.

  As described above, in this method, basically, when there is a suspicion of gas leakage, the sensor driving cycle Ta is temporarily set to a short cycle. As an example, whether or not there is a suspicion of gas leakage is determined based on whether or not “previous value / current value” is equal to or greater than a predetermined threshold (= 2).

  As described above, in this method, when there is a suspicion of gas leakage (in one example, “when the previous value / current value is equal to or greater than a predetermined value (= 2)), a normal sensor driving cycle (45 Switching to a sensor drive cycle (20 seconds) shorter than (second), gas detection is performed at a sensor drive interval shorter than normal.

  As a result, it is possible to detect a gas leak early and issue an alarm without causing a detection delay even when the gas concentration increases rapidly while realizing power saving in normal times and suppressing battery consumption. Become. In particular, in the high concentration (12,500 ppm) in-gas test, it is possible to realize the requirement that a gas leak is detected within 60 seconds and an alarm is issued while realizing power saving and suppressing battery consumption.

  Further, in the present embodiment, the number of times (time) of sensor driving in a short cycle (20 seconds) can be limited by the processing in steps S6 and S7, and wasteful power consumption can be suppressed.

  Furthermore, by extending the sensor drive time to, for example, 200 ms, the sensor output can be acquired in a more stable state while preventing the influence of miscellaneous gases, etc., and thus the gas concentration can be measured more accurately. it can.

  In the above-described process, basically, when it is determined in step S4 that there has been a (sudden) gas concentration increase, the sensor drive cycle is changed to a short cycle (20 seconds) in step S8. After that, unless step S2 or S7 becomes YES, that is, unless the gas concentration reaches an alarm level or the short cycle driving period ends, the short cycle driving is continued in step S8. .

Note that the threshold value, the predetermined value, the driving cycle, and the like for the above determination are merely examples, and the developer or the like may be appropriately set to an optimal value depending on the sensor characteristics, the structure of the alarm device body, and the like.
Next, an example when operating in the present embodiment will be described with reference to FIGS.

4 and 5 show the relationship between the gas concentration change in the gas sensor 11 and the alarm reference concentration when the gas alarm device of the conventional example and this example are exposed to a high concentration gas (12500 ppm).
The gas concentration in the gas sensor 11 is not immediately equal to the surrounding gas concentration due to the influence of the sensor chamber structure of the alarm device 10 body, the gas sensor structure, a filter for removing miscellaneous gases, etc. It will approach the gas concentration. When the gas alarm 10 is inserted into the high-concentration gas, as shown in the figure, the gas concentration in the gas sensor 11 gradually increases and approaches the surrounding gas concentration. It should be noted that the time when the gas alarm device 10 is put in the high-concentration gas can be regarded as a gas leak occurrence time. In this example, as shown in the figure, it is assumed that the gas concentration in the gas sensor 11 (that is, the measured gas concentration) exceeds the alarm reference concentration (alarm level) when 35 seconds have elapsed from the occurrence of the gas leak.

  When the gas concentration rapidly increases under the above conditions, it is necessary to issue a gas leak alarm within one minute. However, in the case of only sensor driving in a normal 45-second cycle, depending on the sensor driving timing, it may not be possible to issue a gas leak alarm within one minute from the time of gas leak occurrence. Specifically, when the sensor drive timing is reached in the section T2 in FIG. 4, a gas leak alarm cannot be issued within one minute. Details will be described below.

  First, considering the case where the sensor drive timing is reached within the T1 interval (0 to 15 seconds) in FIG. 4 in the normal sensor drive cycle (= 45 seconds), the alarm reference concentration is not exceeded in the T1 interval. Therefore, no gas leak warning is given. Since the sensor driving cycle is 45 seconds, the next sensor driving timing is 45 seconds later, and the next sensor driving timing is within the T4 section (45 to 60 seconds) in FIG. In T4 section, since the gas concentration exceeds the alarm reference concentration, a gas leak alarm is issued. Therefore, even in the normal sensor drive cycle (45 seconds), if there is a sensor drive timing within the T1 interval, the next drive timing is within 60 seconds from the point of occurrence of gas leakage, and the alarm reference concentration is exceeded at the next drive timing. Since the gas concentration can be detected, a gas leak alarm can be issued within one minute.

  Next, considering the case where the sensor drive timing is reached within the period T3 (35 to 45 seconds) in FIG. 4 in the normal sensor drive cycle (= 45 seconds), the gas sensor 11 is used for gas detection at this timing. The gas concentration in the gas already exceeds the alarm reference concentration, and a gas leak alarm can be issued immediately.

  Finally, considering the case where the sensor drive timing is reached within the interval T2 (15 to 35 seconds) in FIG. 4 in the normal sensor drive cycle (= 45 seconds), the gas concentration at that time is the alarm reference concentration. It does not exceed and therefore no gas leak alarm is given. If the sensor driving cycle is 45 seconds as it is, the next sensor driving timing is T5 (60 to 80 seconds), which exceeds about 6000 ppm in the illustrated example (naturally, the gas concentration has already exceeded the alarm reference concentration). In this case, a gas leak alarm is issued. However, this means that a gas leak alarm is issued 60 seconds after the gas leak occurs, and the request for issuing the alarm within one minute cannot be satisfied.

  On the other hand, when the gas alarm device 10 of this example is applied under the above conditions, a gas leak alarm can be performed within 1 minute in any case as shown in FIG. In the case of the gas alarm device 10 of this example as well, when the sensor drive timing is reached within the section of T1 or T3, naturally, a gas leak alarm can be issued within one minute as in the conventional case. In the case of the gas alarm device 10 of this example, a gas leak alarm can be issued within one minute even when the sensor drive timing is reached within the section T2.

In the example shown in FIG. 5, the measured gas concentration change is the same as in the example of FIG. 4, and the alarm level (alarm reference concentration) is also the same as in the example of FIG.
Hereinafter, the case where the sensor driving timing is reached in the section T2 will be described with reference to the example shown in FIG.

  First, when the sensor drive timing is reached in the T2 section in the normal sensor drive cycle (= 45 seconds) as in the conventional case, the measurement gas concentration is 500 ppm or more. Although the measured gas concentration at the time of the previous sensor driving is not shown in FIG. 4, it can be considered to be almost “0” (here, 10 ppm). Accordingly, the previous value is the sensor resistance value corresponding to the gas concentration of ‘10’ ppm, and the current value is the sensor resistance value corresponding to the gas concentration of ‘500’ ppm, for example. Thus, for example, if a developer or the like appropriately determines and sets the threshold value so that the “previous value / current value” in such a case is equal to or greater than the predetermined threshold value, the sensor drive timing is set to the above T2. The determination in step S4 can be made YES at any timing within the interval.

  In this manner, in the process of FIG. 4 when the sensor driving timing is reached within the T2 section, “measurement gas concentration <alarm reference concentration” (step S2, NO) and further “previous value / current time”. Since the value "is equal to or greater than the predetermined threshold (step S4, YES), the processing of steps S5 and S8 is executed, and the sensor driving cycle is changed from the normal cycle (45-second cycle) to the short cycle (20-second cycle). Is done.

  Since the detection cycle is 20 seconds, the next sensor drive timing is within the period T6 (35 to 55 seconds) in FIG. Therefore, at the next sensor driving timing, since the measured gas concentration exceeds the alarm reference concentration, it is possible to issue a gas leak alarm within one minute.

Hereinafter, the case where the sensor driving timing is reached within the section T2 will be described with reference to the relationship diagram between the sensor resistance value and the gas concentration shown in FIG. 6 and the example shown in FIG.
First, when the sensor drive timing is reached in the T2 section in the normal sensor drive cycle (= 45 seconds) as in the conventional case, the measurement gas concentration is 500 ppm or more. On the other hand, in FIG. 6, the sensor resistance value with a gas concentration of 500 ppm is about ½ of the sensor resistance value with almost no gas (10 ppm).

  That is, it can be seen that the sensor resistance value at the gas concentration in the section T2 in FIG. Therefore, the previous sensor resistance value is compared with the current sensor resistance value, and if the ratio (here, “current value / previous value” contrary to the above example) is ½ or less. Therefore, it can be determined that the gas concentration is increasing rapidly (step S4 in FIG. 3).

  Thereby, the sensor driving cycle is changed from the normal cycle (45-second cycle) to the short cycle (20-second cycle). Since the detection cycle is 20 seconds, the next sensor drive timing is within the period T6 (35 to 55 seconds) in FIG. Therefore, at the next sensor driving timing, since the measured gas concentration exceeds the alarm reference concentration, it is possible to issue a gas leak alarm within one minute.

  As described above, in the sensor driving method of the gas alarm device 10 of the present example, the cycle is normally 45 seconds, and the gas sensor can be driven without consuming extra power, so that the battery usage can be reduced. it can. Only when there is a possibility of gas leakage (when the gas concentration increases (suddenly)), temporarily switch to a drive cycle shorter than the normal drive cycle, and perform gas detection at a sensor drive interval faster than normal. To do. As a result, an alarm for gas leakage can be issued at an early stage while minimizing an increase in current consumption. In particular, in a state where it is required to issue a gas leak alarm within one minute, it is possible to reliably issue a gas leak alarm within one minute while suppressing power consumption, and to provide a highly reliable alarm device. It becomes possible.

  The relationship between the gas concentration and the elapsed time in FIGS. 4 and 5 is an example, and the relationship between the gas concentration and the elapsed time varies depending on the sensor chamber structure of the alarm device, the gas sensor structure, the filter type of the gas sensor, and the like. The threshold value, the short cycle time, and the upper limit number of short cycle driving used in the determination in step S4 are appropriately determined by the designer or the like based on these relationships. In particular, in what case it is assumed that “the gas concentration has increased (suddenly)” depends on the threshold value used in the determination in step S4.

Here, FIG. 7 shows a time chart of sensor driving in a modified example (example in which steps S14 and S15 are not executed).
That is, the processing example shown in FIG. 3 is an example, and is not limited to this example. For example, the processing of steps S14 and S15 may not be executed. In this case, the same processing as S7, S12, S13 is executed instead of S14, S15. That is, instead of immediately returning to the 45-second cycle when the alarm reference concentration is exceeded, it may be driven for a predetermined number of times (short cycle detection counter = 5) for a short cycle (20 seconds). In other words, when a sudden gas concentration change is detected, it is always a predetermined multiple times (short cycle detection counter = 5) and short cycle (20 seconds) regardless of whether or not the alarm reference concentration has been exceeded. You may make it drive.

As mentioned above, although an example was shown as a modification, other modifications may be sufficient. In any case, the present invention is not limited to the embodiment shown in FIGS.
FIG. 8 is a functional block diagram of the control unit 40 corresponding to the control circuit unit 12 of the gas alarm device 10 of this example.

  The control unit 40 is a microcomputer (CPU or the like) that controls the operation of the gas alarm device 10 as a whole, and by executing a program stored in advance in a built-in memory (not shown), the processing of FIG. The processing functions of the various functional units shown in FIG.

  The gas alarm device 10 of this example includes a gas sensor 31 having a sensor element 31a and a heater resistor 31b for heating the sensor element 31a, and a control unit 40. The control unit 40 has a function of measuring the resistance value of the sensor element 31a by controlling the heating of the heater resistor 31b. Conventionally, the gas resistance such as methane gas is measured based on the sensor resistance value (the voltage value V1 corresponding to the sensor resistance value) and the like, and it is determined whether or not a gas leak alarm is performed. Has each function. The gas sensor 31, the sensor element 31a, and the heater resistor 31b may be regarded as corresponding to the gas sensor 11, the sensor resistor 11a, and the heater resistor 11b of FIG.

The control unit 40 in the illustrated example includes a sensor drive unit 41, a sensor resistance value calculation unit 42, a previous value storage unit 43, a determination unit 44, a drive cycle change unit 45, a gas concentration calculation unit 46, an alarm unit 47, and the like.
The sensor drive unit 41 is a functional unit that drives the gas sensor 31 by energizing pulses with an arbitrary drive cycle, and normally drives the gas sensor 31 with a first drive cycle (for example, 45 seconds).

The sensor resistance value calculation unit 42 obtains the resistance value of the gas sensor (the sensor element 31a) based on the output (the voltage V1 and the like) of the gas sensor 31 when the sensor is driven.
The previous value storage unit 43 stores the sensor resistance value obtained by the sensor resistance value calculation unit 42 at the time of the previous sensor drive as the previous value.

  Based on the current value, which is the sensor resistance value obtained by the sensor resistance value calculation unit 42, and the previous value, the determination unit 44 determines whether or not the gas concentration has been increased (rapid increase). judge.

  When the determination unit 44 determines that the gas concentration has increased, the driving cycle changing unit 45 temporarily causes the sensor driving unit 41 to drive the gas sensor 31 at a second driving cycle shorter than the first driving cycle. .

The gas concentration calculation unit 46 calculates the gas concentration based on the output (voltage V1, etc.) of the gas sensor 31 when the sensor is driven.
The alarm unit 47 issues an alarm when the calculated gas concentration exceeds a predetermined first threshold value. Note that the gas concentration calculation unit 46 is not provided, and the alarm unit 47 can perform a predetermined alarm operation based on the determination of the determination unit 44 when the sensor resistance value exceeds a predetermined first threshold value.

  Here, the determination unit 44 determines whether or not the gas concentration is increased based on, for example, a ratio between the current value and the previous value and a predetermined threshold value set in advance. For example, if “previous value / current value”, which is a ratio between the current value and the previous value, is greater than or equal to a predetermined threshold value, it is determined that the gas concentration has increased. Alternatively, based on the difference between the current value and the previous value and another predetermined threshold value, it is determined whether or not the gas concentration is increased.

  For example, when the number of times the gas sensor 31 is driven in the second driving cycle reaches a predetermined number set in advance, the driving cycle changing unit 45 sets the driving cycle of the sensor driving unit 41 to the first driving cycle. You may make it return to.

  Alternatively, the driving cycle changing unit 45 may, for example, when the number of driving times of the gas sensor 31 in the second driving cycle reaches a predetermined number of times before the calculated gas concentration exceeds the first threshold value. The drive cycle of the sensor drive unit 41 may be returned to the first drive cycle.

Alternatively, the drive cycle changing unit 45 may return the drive cycle of the sensor drive unit 41 to the first drive cycle, for example, when the calculated gas concentration exceeds the first threshold value.
In addition, the sensor drive unit 41 performs pulse energization for a predetermined first energization time at an arbitrary drive cycle for a predetermined first energization time, and a second energization longer than the first energization time when a predetermined condition is met. You may make it perform pulse energization for time.

The sensor drive unit 41 may perform pulse energization during the second energization time when driven in the second drive cycle.
In the above-described gas alarm device of the present invention, the gas sensor is driven with a relatively long driving cycle (first driving cycle) to detect ambient gas, and the sensor resistance value during current driving and the previous driving time are detected. Based on the sensor resistance value, it is determined whether or not the short cycle driving is temporarily performed. For example, when the change in the sensor resistance value based on the current value and the previous value is larger than a predetermined value (that is, when the gas concentration rapidly increases), the sensor driving cycle is shortened (second driving cycle). Detect ambient gas. As a result, it is possible to issue a gas leak alarm early without delay in detection even when a sudden gas concentration rises, while realizing power saving and suppressing battery consumption.

DESCRIPTION OF SYMBOLS 10 Gas alarm device 11 Gas sensor 11a Sensor resistance 11b Heater resistance 12 Control circuit part 13 Alarm part 13a Alarm sound output part 13b Alarm display part 13c External alarm output part 14 Ambient temperature detection part 15 Battery part R Load resistance SW1 Transistor switch SW2 Transistor switch 31 Gas sensor 31a Sensor element 31b Heater resistance 40 Control unit 41 Sensor drive unit 42 Sensor resistance value calculation unit 43 Previous value storage unit 44 Determination unit 45 Drive cycle change unit 46 Gas concentration calculation unit 47 Alarm unit

Claims (9)

A battery-type gas alarm device using a battery as a power source, which detects gas leakage based on the output of a gas sensor whose electrical characteristics change according to the gas concentration of the detection target gas,
Sensor driving means for driving the gas sensor by energizing pulses at an arbitrary driving cycle, and sensor driving means for driving the gas sensor at a first driving cycle at a normal time;
Sensor resistance value calculating means for obtaining a resistance value of the gas sensor based on an output of the gas sensor when the sensor is driven;
Previous value storage means for storing the sensor resistance value obtained by the sensor resistance value calculation means at the time of the previous sensor drive as a previous value;
Determination means for determining whether or not the gas concentration is increased based on the current value which is the sensor resistance value obtained by the sensor resistance value calculating means and the previous value;
Drive period changing means for causing the sensor driving means to drive the gas sensor at a second drive cycle shorter than the first drive cycle when the determination means determines that the gas concentration has increased;
Have
The determination means, based on said ratio with a predetermined threshold value between the present value and the previous value, battery-powered gas detector, characterized in that to determine whether gas concentration or elevated.   The driving cycle changing unit returns the driving cycle of the sensor driving unit to the first driving cycle when the number of times the gas sensor is driven in the second driving cycle reaches a predetermined number of times set in advance. The battery-type gas alarm device according to claim 1. Gas concentration calculating means for calculating a gas concentration based on the output of the gas sensor during the driving;
Alarm means for issuing an alarm when the calculated gas concentration exceeds a predetermined first threshold;
The battery-type gas alarm device according to claim 1, further comprising:   2. The battery-type gas alarm device according to claim 1, further comprising alarm means for performing an alarm when the sensor resistance value during driving of the sensor exceeds a predetermined first threshold value. Gas concentration calculating means for calculating a gas concentration based on the output of the gas sensor during the driving;
Alarm means for issuing an alarm when the calculated gas concentration exceeds a predetermined first threshold;
The driving cycle changing means is configured to detect the sensor when the number of times the gas sensor is driven in the second driving cycle reaches a predetermined number of times before the calculated gas concentration exceeds the first threshold. The battery-operated gas alarm device according to claim 2, wherein the drive cycle of the drive means is returned to the first drive cycle.   4. The drive cycle changing means according to claim 3, wherein when the calculated gas concentration exceeds the first threshold, the drive cycle of the sensor drive means is returned to the first drive cycle. Battery-powered gas alarm.   The sensor driving means performs the pulse energization for a predetermined first energization time in the normal time for each arbitrary driving cycle, and a second energization longer than the first energization time when a predetermined condition is met. 2. The battery type gas alarm device according to claim 1, wherein the pulse energization is performed for an amount of time.   The battery-type gas alarm device according to claim 7, wherein the sensor driving means performs the pulse energization during the second energization time when the sensor driving means is driven in the second driving cycle. A control device in a battery-type gas alarm device using a battery as a power source, which detects gas leakage based on the output of a gas sensor whose electrical characteristics change according to the gas concentration of the detection target gas,
Sensor driving means for driving the gas sensor by energizing pulses at an arbitrary driving cycle, and sensor driving means for driving the gas sensor at a first driving cycle at a normal time;
Sensor resistance value calculating means for obtaining a resistance value of the gas sensor based on an output of the gas sensor when the sensor is driven;
Based on the previous value, which is the sensor resistance value obtained by the sensor resistance value calculating means during the previous sensor driving, and the current value, which is the sensor resistance value obtained by the sensor resistance value calculating means, this time. Determining means for determining whether or not the gas concentration is increased;
A drive period changing means for causing the sensor driving means to drive the gas sensor at a second drive cycle shorter than the first drive cycle when the determination means determines that the gas concentration has increased;
The determination means, the current value on the basis of the ratio between the previous value with a predetermined threshold value, the control unit of the battery-powered gas detector, characterized in that to determine whether gas concentration increase.