JPWO2012105423A1 - Battery-powered gas alarm and its control device - Google Patents

Abstract

When a second reference concentration that is a threshold lower than the first reference concentration that is an alarm level is provided and the gas concentration is equal to or lower than the second reference concentration (S3, NO), the sensor drive cycle is 45 seconds, but the second If the reference concentration is exceeded (S3, YES), the sensor driving cycle is set to a short cycle (20 seconds).

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.

  Gas alarms are known that detect gas leaks from gas appliances and gas pipes, issue alarms with sounds and buzzers, etc., and inform gas users of gas leaks.

  The gas alarm device detects a detection target gas by a gas detection element such as a gas sensor, and when the gas concentration of the detection target gas exceeds a predetermined gas concentration, an alarm is sounded by an alarm sound or an alarm display. .

  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 so that the heater temperature is heated to a predetermined temperature such as 400 ° C., and the resistance value of the sensor resistance (actually, a voltage or the like indicating this resistance value) is changed. Gas detection is performed by measuring.

  There are two methods of driving the gas sensor heater temperature to a predetermined temperature: a method of applying a DC voltage or a method of applying a voltage in a pulsed manner. Particularly in battery-operated gas alarms driven by batteries, power consumption is reduced. For this purpose, a method of applying a pulse current to the heater at a predetermined drive cycle is performed (Patent Document 1, Patent Document 2).

  FIG. 8 shows an example of sensor driving by pulse energization. The gas sensor is pulse-energized for 100 ms every 45 seconds of the sensor driving period, and gas detection 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; in this example, 100 ms) is shortened to enable gas detection in a short time, and the drive cycle is lengthened to drive the sensor with power saving. Can be done.

  In a high concentration (12,500 ppm) in-gas test, the gas alarm device needs to detect the gas leak occurrence and issue an alarm within 60 seconds after the gas leak occurrence (Patent Document 3).

  On the other hand, as described above, in the battery-driven gas alarm device, a method of applying a pulse with a predetermined driving cycle is performed to save power. However, this is gas detection only at a predetermined drive cycle timing, and gas detection is not performed at any time. Therefore, it is difficult to detect gas and issue an alarm within 60 seconds.

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.
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.

  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 pulse energization drive cycle and increasing the gas detection timing, but 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 a battery-type gas alarm device, it is desired to make the drive period of pulse energization as long as possible. 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. However, since gas detection is performed only every 90 seconds, the gas concentration increases during 90 seconds. If it rises, there is a possibility that the gas will be detected after greatly exceeding the gas concentration that you would like to detect, which will cause safety concerns.)
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 with a delay to the ambient gas concentration. Therefore, the driving cycle must be determined in consideration of not only the sensor driving cycle but also the gas concentration detection delay due to the structure of the 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 gas alarm device of the present invention is a battery-type gas alarm device using a battery as a power source for detecting gas leakage based on the output of a gas sensor whose electrical characteristics change according to the gas concentration of the detection target gas. It has a configuration.

  That is, based on the means for driving the gas sensor by energizing the pulse with an arbitrary driving cycle, which normally drives the gas sensor with the first driving cycle, and the output of the gas sensor during the driving. Gas concentration calculating means for calculating the gas concentration, and alarm means for issuing an alarm when the calculated gas concentration exceeds a predetermined first threshold value.

  Further, it is determined whether or not the gas concentration calculated by the gas concentration calculating means exceeds a second threshold that is a threshold lower than the first threshold, and if the gas concentration exceeds the second threshold, The sensor drive means has drive cycle changing means for driving the gas sensor at a second drive cycle shorter than the first drive cycle.

  In the above-described gas alarm device of the present invention, the gas sensor is driven at a relatively long driving cycle (first driving cycle) to detect ambient gas, and the gas concentration is a threshold value lower than the first threshold value. When the second threshold value is exceeded, the sensor driving cycle is shortened (second driving cycle) to detect ambient gas. For this reason, 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.

It is a block diagram of one Embodiment of the gas alarm device by this invention. 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 time chart figure of sensor drive in case gas concentration increases gently. It is a time chart figure of sensor drive in the modification which does not perform S10 and S11. It is a figure explaining the sensor drive timing of the conventional battery-type gas alarm device.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration diagram of an embodiment of a gas alarm device according to the present invention.

  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. The resistance value of the sensor resistor 11a (voltage value corresponding to the resistance value, etc.) is measured. The detection target gas may be city gas, LP gas, or other gas, but naturally, a gas sensor corresponding to the type of detection target gas is used. .

  The battery unit 15 supplies a power of 3 volts in this example, and supplies power 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.

  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 an application program stored in advance in a built-in memory (not shown), the control processing unit 12 and the control circuit unit 12 are described later. The processing of the flowchart shown in FIG.

  The control circuit unit 12 has terminals such as output terminals OUT1 and OUT2, input terminals AD1 and AD2. The output terminal OUT1 is connected to the base of the switch SW1, and the switch SW1 is ON / OFF controlled by an output signal 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 an output signal from the output terminal OUT2. The input terminals AD1 and AD2 may be particularly referred to as AD conversion input terminals AD1 and AD2, and the reason will be described later.

  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 according to the output signals from the output terminals OUT1 and OUT2, thereby causing the gas sensor 11 (its heater resistance 11b). , The sensor resistor 11a) and the load resistor R are operated by supplying electric power.

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

  A voltage value V1 between the sensor resistor 11a and the load resistor R is input to the control circuit unit 12 via an AD (analog-digital) conversion input terminal AD1. 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 corresponds to the resistance value of the sensor resistor 11a.

  In this way, the control circuit unit 12 detects the sensor output (voltage value V1; resistance value of the sensor resistor 11a) of the gas sensor 11 via the input terminal AD1, and for example, the sensor output has a predetermined gas concentration (first reference described later). Gas leak detection is performed by determining whether or not the value corresponding to the concentration (alarm level)) has been exceeded. Although this may be considered to be substantially the same as the conventional one, in this example, a second reference density, which is a threshold lower than the first reference density, is set, and this is used to change the sensor driving cycle. The process is also performed. Details will be described later.

  The AD conversion input terminals AD1 and AD2 include not only the input terminal but also a function (AD (analog-digital) converter) for converting an analog signal (voltage value V1 or the like) input to the input terminal into a digital value. It shall be assumed. Therefore, the control circuit unit 12 inputs the digital value of the voltage value V1 through the input terminal AD1.

  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 alarm, the control circuit unit 12 blinks or lights the LED to display the alarm state with the LED to notify the gas leakage state. Further, the control circuit unit 12 may output an alarm signal to an external device such as a gas meter or a centralized monitoring panel via the external alarm output unit 13c 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 AD conversion input terminal AD2, and the control circuit unit 12 is This is a configuration for performing a temperature correction calculation of the gas concentration based on the temperature.

  Here, the sensor driving according to the present embodiment will be described 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 a sensor drive cycle Ta and a sensor drive time (corresponding to the pulse energization time) Tb. In this method, the sensor driving cycle Ta may be temporarily changed. Details will be described later.

  In the present embodiment, 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 signals from the output terminals OUT1 and OUT2 each time the sensor drive timing according to the sensor drive cycle Ta is reached, and thus the heater resistor 11b in the gas sensor 11 and the sensor 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 from the AD1 terminal when 100 ms elapses from the sensor driving timing (for example, the internal timer determines that 100 ms elapses). The control circuit unit 12 converts the read sensor output voltage V1 into a gas concentration, and compares the gas concentration with a predetermined threshold (alarm level) to determine whether or not the predetermined gas concentration is exceeded. .

  Note that the process itself for converting the sensor output voltage V1 into the gas concentration is an existing general one, and is not particularly described here. Furthermore, the process itself of comparing the converted gas concentration (measured gas concentration) with a predetermined alarm level is an existing technique, but in this method, another threshold is added. That is, in the past, the threshold value was one type, but in this method, two types of threshold values are provided.

  That is, in this method, as shown in FIG. 2, two types of threshold values, ie, a first reference density (first threshold value) and a second reference density (second threshold value) are provided. For example, the first reference concentration may be considered to correspond to the alarm level, and if the converted gas concentration (measured gas concentration) exceeds the first reference concentration, a gas leak alarm is issued. become. On the other hand, the second reference density is a threshold value lower than the first reference density (first reference density> second reference density). When a gas leak occurs (especially when the gas concentration is high), the measured gas concentration basically exceeds the second threshold value and then exceeds the first threshold value.

  In this method, when the measured gas concentration exceeds the second threshold value (and the first threshold value is not exceeded), the sensor driving cycle Ta is changed. This is changed so as to be shorter than the normal sensor driving cycle (= 45 seconds). In this example, for example, Ta = 20 seconds, but this is not limited to this example. Thereafter, when the measured gas concentration exceeds the first threshold value, the alarm unit 13 is controlled to perform a gas leak notification operation as in the conventional case.

  Here, the “gas concentration” column in FIG. 2 shows specific examples of the first reference concentration, the second reference concentration, and the measurement gas concentration. The “sensor driving” column and the “alarm display” column show the sensor driving timing and the notification / reporting timing according to the example of the “gas concentration” column.

  In the example shown in FIG. 2, in the gas detection from the first time to the third time, the measured gas concentration does not exceed the second reference concentration (second threshold), so it is determined that there is no gas around and the alarm is Without being performed, the sensor driving cycle Ta is also continued for 45 seconds.

  In the fourth gas detection, since the measured gas concentration exceeds the second reference concentration, it is determined that there is a gas around and the sensor drive cycle Ta is shortened (in this example, from the normal 45-second cycle). Change to 20-second period). At this time, since the measured gas concentration does not exceed the first reference concentration which is the alarm level concentration, the gas leak alarm is not performed.

  Since the sensor driving cycle Ta is changed (short cycle), the fifth gas detection is performed 20 seconds after the fourth gas detection, but “the measured gas concentration exceeds the second reference concentration”. Is less than or equal to the first reference concentration and the number of detection times (= second time) is less than the predetermined number (5 times) ”, the sensor driving cycle Ta = 20 seconds is continued. The processing when the number of detections is equal to or greater than the predetermined number (5 times) will be described later.

  However, the condition “the number of detection times is less than the predetermined number” is not necessarily an essential condition. Therefore, for example, as long as the above condition “the measurement gas concentration exceeds the second reference concentration but is not more than the first reference concentration” is satisfied, the sensor driving cycle Ta = 20 seconds is continued regardless of the number of detections. You may do it.

  Furthermore, in the sixth gas detection, since the measured gas concentration increases and exceeds the first reference concentration which is the alarm level concentration, a gas leak alarm is generated by voice and an alarm is displayed by LED display. In addition, if the gas leak alarm is performed, the target early gas detection is satisfied, the sensor drive cycle Ta is returned to the normal 45-second cycle and the subsequent gas detection is continued (the seventh and subsequent gas detections). Detection). However, this is not necessarily an essential condition. Thus, for example, the sensor drive cycle Ta = 20 seconds may be continued without returning to the 45-second cycle even after the warning is issued or the alarm display is performed.

  As described above, the gas alarm device 10 of the present example achieves a rapid gas concentration rise while reducing power consumption by suppressing power consumption by detecting a relatively long cycle (for example, a 45-second cycle operation) during normal times. However, by changing the detection operation to a relatively short cycle detection operation (for example, a 20-second cycle operation), it becomes possible to detect a gas leak at an early stage without detection delay, and a highly reliable gas alarm device can be provided.

  Further, although not shown in the time chart of FIG. 2, the following operation may be performed.

  That is, basically, as described above, after the measurement gas concentration exceeds the second reference concentration, the main processing (gas leak determination) is executed in a cycle of 20 seconds, but it continues for a predetermined number of times (in this example, five times). When “second reference concentration <measured gas concentration <first reference concentration” (step S2 in FIG. 3 is NO and step S3 is YES), the sensor drive cycle Ta is returned to the normal 45-second cycle. It is desirable to make it. That is, in such a case, that is, when the first reference concentration does not exceed the first reference concentration even after a predetermined time has passed since the surrounding gas is present, it can be determined that the increase in gas concentration is gradual and not urgent. Therefore, the sensor driving cycle in the 20-second cycle is stopped and returned to the 45-second cycle that is the normal sensor driving cycle, thereby suppressing wasteful power consumption.

  The value of the predetermined number of times and the relatively short cycle of the sensor driving cycle is appropriately determined depending on the gas concentration change to be detected, and is limited to the above value (5 times or 20 seconds). It is not a thing.

  FIG. 3 is a flowchart of processing for determining a driving period of sensor driving according to an embodiment. The processing in the flowchart is repeatedly performed every time the sensor driving is executed in the Ta cycle by the control circuit unit 12 (microcomputer or the like) in FIG. 1. For example, the final timing of the sensor pulse driving (such as when 100 ms elapses) ). 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 each sensor driving time Tb in the sensor driving cycle Ta based on the control by an internal timer (not shown), and sets the AD conversion input terminal AD1 at the end of sensor driving. Then, the sensor output voltage V1 of the gas sensor 11 is read. The control circuit unit 12 calculates the gas concentration based on the read sensor output voltage V1 (step S1). As described above, in this example, the normal Ta is 45 seconds and Tb is always 100 ms.

  Next, it is determined whether or not the calculated current gas concentration (measured gas concentration) exceeds a first reference concentration (first threshold) that is an alarm level concentration (measured gas concentration> first reference concentration?). (Step S2).

  When the measured gas concentration exceeds the first reference concentration (step S2, YES), the short cycle detection counter value is forcibly set to “5” (step S10), and the sensor drive cycle Ta is set to a normal cycle ( In this example, 45 seconds) (step S11), a predetermined alarm process (step S12) is performed, and this process ends. Step S12 is an alarm process by the alarm unit 13 described above.

  Here, in this method, when “second reference concentration <measured gas concentration <first reference concentration”, the drive cycle (20 seconds in this example) is shorter than the normal drive cycle (45 seconds in this example). The short period detection counter is a counter that counts the number of times the sensor is driven with a period of 20 seconds. If this count value is equal to or greater than a predetermined value ('5' in this example), the sensor drive cycle Ta is returned from the short cycle (20 seconds) to the normal drive cycle (45 seconds) (step S4 described later). Is YES and S9).

  However, when the measured gas concentration exceeds the first reference concentration, the short cycle detection counter is forcibly set to “5” regardless of the current count value. As a result, when the measurement gas concentration exceeds the first reference concentration, the sensor driving in a short cycle is stopped. In the example of FIG. 3, after the measured gas concentration exceeds the first reference concentration, the state of “second reference concentration <measured gas concentration <first reference concentration” again occurs due to, for example, some fluctuation. However, since the determination in step S4, which will be described later, is YES, the normal driving cycle (45 seconds) is maintained. However, the present invention is not limited to this example.

  In this way, in this example, by reducing the number of times the sensor is driven in a short cycle as much as possible, an alarm for gas leakage can be issued early while minimizing an increase in current consumption. To do.

  On the other hand, when the measured gas concentration is equal to or lower than the first reference concentration (step S2, NO), the second reference concentration (second threshold value), in which the measured gas concentration is lower than the first reference concentration, is subsequently obtained. (Measured gas concentration> second reference concentration?) Is determined (step S3).

  If the measured gas concentration is less than or equal to the second reference concentration (step S3, NO), it is determined that there is no gas in the surroundings, and the short cycle detection counter is cleared (counter value is set to initial value = 1) (step S8). ), The sensor driving cycle Ta is set to 45 seconds of the normal driving (step S9), and further, the state is set to no alarm (the alarm is canceled if the alarm is in effect) (step S7), and this process is terminated.

  If the measured gas concentration is equal to or lower than the first reference concentration and exceeds the second reference concentration (S2 is NO and S3 is YES), first, the short cycle detection counter becomes 5 times or more. (Step S4).

  When the short cycle detection counter is 5 times or more (step S4, YES), that is, when the number of times of sensor driving in the short cycle (20 seconds) reaches a predetermined number, the sensor driving cycle Ta is set. It returns to the period of 45 seconds of normal driving (step S9). This is because the necessary number of detections in a short cycle has already been completed for the reasons already described.

  On the other hand, when the short cycle detection counter is less than 5 times (step S4, NO), the sensor drive cycle is set to 20 seconds (if it is already 20 seconds, it is left as it is; detection in the short cycle is continued). (Step S5), the short cycle detection counter is counted up (Step S6), the processing of Step S7 is performed, and this processing is terminated.

  As described above, in the present embodiment, when there is a suspicion of gas leakage (when measured gas concentration> second reference concentration), the sensor driving cycle shorter than the normal sensor driving cycle (45 seconds). Switch to (20 seconds) and perform gas detection at a sensor drive interval that is faster than normal, so power saving is achieved and battery consumption is reduced, and detection delays even when the gas concentration increases rapidly It becomes possible to detect a gas leak at an early stage without generating a warning and to issue an alarm.

  In particular, in a high concentration (12,500 ppm) in-gas test, a request to detect a gas leak within 60 seconds and issue an alarm can be realized while saving power and suppressing battery consumption (later This will be described with reference to FIGS.

  In the present embodiment, wasteful power consumption can be suppressed by restricting the number of times the sensor is driven in a short cycle (20 seconds) by the processes of S10 and S11 or S4 and S9. In other words, after the measured gas concentration exceeds the first reference concentration (after issuing an alarm), it is possible to suppress wasteful power consumption by returning the sensor driving cycle Ta to the 45-second cycle of normal driving. . Alternatively, if the number of times of driving (the number of times of detection) reaches the predetermined number of times while the sensor gas is driven in a short cycle (20 seconds) and the measured gas concentration does not exceed the first reference concentration, the sensor driving cycle By returning Ta to a normal driving cycle (45 seconds) from a short cycle (20 seconds), wasteful power consumption can be suppressed.

  Next, an example when operating in the present embodiment will be described with reference to FIGS.

  FIG. 4 shows the relationship between the gas concentration change in the gas sensor 11 and the reference concentration when a conventional gas alarm is exposed to a high concentration (12500 ppm) gas. FIG. 5 shows the relationship between the gas concentration change (same as FIG. 4) and two reference concentrations in the case of the gas alarm device 10 of this example.

  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 first reference concentration (alarm level) when 34 seconds elapse 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 comes within the T1 interval (0 to 15 seconds) in FIG. 4 in the normal sensor drive cycle (= 45 seconds), the first reference concentration is exceeded in the T1 interval. Because there is no gas leak warning. Since the sensor driving cycle is 45 seconds, the next sensor driving timing is 45 seconds after the current driving time, and the next sensor driving timing is within the T4 section (45 to 60 seconds) in FIG. In the T4 section, since the gas concentration exceeds the first 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 will be within 60 seconds from the point of occurrence of gas leakage and will exceed the first reference concentration 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 (34 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 first reference concentration, and a gas leak alarm can be issued immediately.

  Finally, considering the case where the sensor drive timing is reached within the period T2 (15 to 34 seconds) in FIG. 4 in the normal sensor drive cycle (= 45 seconds), the gas concentration at that time is the first reference concentration. And therefore no gas leak warning is provided. If the sensor driving period is 45 seconds as it is, the next sensor driving timing is T5 (60 to 79 seconds), which exceeds about 6000 ppm in the illustrated example (naturally, the gas concentration has already exceeded the first reference concentration). However, this will issue a gas leak alarm after 60 seconds from the occurrence of the gas leak, and cannot satisfy the requirement to issue an alarm within one minute.

  On the other hand, when the above condition is applied to the gas alarm device 10 of this example, a gas leak alarm can be performed within one 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 (first reference concentration) is also the same as in the example of FIG. In the gas alarm device 10 of the present method, a threshold value (second reference concentration) lower than the alarm level (first reference concentration) is also set. In the example shown in FIG. The measured gas concentration exceeds the second reference concentration at the beginning of the T2 interval).

  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, as in the conventional case, when the sensor driving timing is reached within the T2 interval in the normal sensor driving cycle (= 45 seconds), the measured gas concentration exceeds the second reference concentration, so the sensor driving cycle is the above-mentioned time. The normal cycle (45-second cycle) is changed to a short cycle (20-second cycle). Since the detection cycle (drive cycle) is 20 seconds, the next sensor drive timing is within the period T6 (35 to 54 seconds) in FIG. Therefore, at the next sensor driving timing, since the measured gas concentration exceeds the first reference concentration, a gas leak alarm can be performed 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 second reference concentration is exceeded), the normal driving cycle (45-second cycle) is switched to a short driving cycle (20-second cycle), and the sensor is faster than usual. Gas detection is performed at driving intervals. Therefore, 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 methane 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 differs depending on the sensor chamber structure of the alarm device body, the gas sensor structure, the filter type of the gas sensor, and the like. The designer or the like appropriately determines the time of the drive cycle shorter than usual and the number of times of short cycle drive based on these relationships.

  Here, FIG. 6 shows a time chart for driving the sensor when the gas concentration gradually increases.

  As shown in the figure, in this case, even if the measurement gas concentration exceeds the second reference concentration and is measured five times (even if the short cycle detection counter ≧ 5), the first reference concentration does not exceed 45. After returning to the second cycle, an alarm is issued when the first reference concentration is exceeded. As described above, detection of gas leakage within 60 seconds is a condition in a high concentration (12500 ppm) in-gas test, and is not relevant in the example as shown in FIG. 6 (the gas concentration gradually increases). Therefore, in the example of FIG. 6, the gas leak detection within 60 seconds cannot be performed, but there is no particular problem.

  FIG. 7 is a time chart of sensor driving in a modification in which S10 and S11 are not executed.

  That is, the processing example shown in FIG. 3 is an example, and is not limited to this example. For example, S10 and S11 may not be executed. In this case, the same processing as S4, S5, S6 and S9 is executed instead of S10 and S11. That is, when the first reference concentration is exceeded, the cycle does not immediately return to the 45 second cycle, but is driven for a predetermined number of times (short cycle detection counter = 5) for a short cycle (20 seconds) after the measurement gas concentration exceeds the second reference concentration. You may make it do. In other words, when the second reference concentration is exceeded, it is always a predetermined multiple times (short cycle detection counter = 5) and short cycle (20 seconds) regardless of whether or not the first reference concentration is 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.

  As described above, the alarm device of the present invention has a predetermined concentration at which the gas concentration of the detection target gas is less than the alarm level while reducing the battery usage by extending the drive period of pulse energization for gas detection in normal times. When (second reference concentration) is exceeded, the sensor drive cycle is shortened to realize early gas detection. The sensor driving cycle may be shortened up to a predetermined number of times. Further, when the gas concentration exceeds the alarm level, the sensor driving cycle may be immediately restored. By doing so, an alarm for gas leakage can be issued at an early stage while minimizing an increase in current consumption.

  An alarm can be issued at a predetermined gas concentration without delaying detection with respect to a rapid gas concentration change, and a highly reliable gas alarm device can be provided.

  Since the gas sensor can be driven without consuming extra power, the battery usage can be reduced, and the cost can be reduced by reducing the number of batteries, and the size and weight of the device can be reduced.

  In addition, it can also be said that the gas alarm device 10 of the present example includes various functional units described below when the control circuit unit 12 executes the application program and the like.

  That is, the gas alarm device 10 which is a battery-type gas alarm device using a battery as a power source for detecting a gas leak based on the output of a gas sensor whose electrical characteristics change according to the gas concentration of the detection target gas includes the following various types. A functional part is provided.

  That is, first, a functional unit that drives the gas sensor by energizing the pulse with an arbitrary driving cycle, and normally has a sensor driving functional unit that drives the gas sensor with the first driving cycle.

  A gas concentration calculation function unit that calculates a gas concentration based on an output of the gas sensor when the sensor is driven; and an alarm function unit that issues an alarm when the calculated gas concentration exceeds a predetermined first threshold value. .

  Further, it is determined whether or not the gas concentration (measurement gas concentration) calculated by the gas concentration calculation function unit exceeds a second threshold that is a threshold lower than the first threshold, and the measured gas concentration exceeds the second threshold. In this case, the sensor drive function unit has a drive cycle change function unit that drives the gas sensor at a second drive cycle shorter than the first drive cycle.

  Further, for example, the drive cycle changing function unit may perform the second operation when the number of times the gas sensor is driven in the second drive cycle reaches a predetermined number set in advance or before the measured gas concentration exceeds the first threshold. When the number of driving times of the gas sensor in the driving cycle reaches a predetermined number set in advance, the sensor driving cycle of the sensor driving function unit may be returned to the first driving cycle.

  For example, the drive cycle changing function unit may return the drive cycle of the sensor drive function unit to the first drive cycle when the measured gas concentration exceeds the first threshold.

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.

Claims (4)

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,
Means for driving the gas sensor by energizing a pulse at an arbitrary drive cycle, and normally a sensor drive unit for driving the gas sensor at a first drive cycle;
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;
It is determined whether or not the gas concentration calculated by the gas concentration calculating means exceeds a second threshold that is a threshold lower than the first threshold. If the gas concentration exceeds the second threshold, the sensor drive is performed. Drive period changing means for causing the means to drive the gas sensor at a second drive period shorter than the first drive period;
And a battery-type gas alarm device.   The driving cycle changing means is configured to change the second driving cycle when the number of times the gas sensor is driven in the second driving cycle reaches a predetermined number set in advance or before the calculated gas concentration exceeds the first threshold value. 2. The driving cycle of the sensor driving means is returned to the first driving cycle when the number of times of driving the gas sensor in the driving cycle reaches a predetermined number set in advance. Battery-powered gas alarm.   2. The drive cycle changing unit according to claim 1, wherein when the calculated gas concentration exceeds the first threshold value, the drive cycle of the sensor drive unit is returned to the first drive cycle. Battery-powered gas alarm. 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,
Means for driving the gas sensor by energizing a pulse at an arbitrary drive cycle, and normally a sensor drive unit for driving the gas sensor at a first drive cycle;
Gas concentration calculating means for calculating a gas concentration based on the output of the gas sensor during the driving;
Alarm control means for issuing an alarm when the calculated gas concentration exceeds a predetermined first threshold;
It is determined whether or not the gas concentration calculated by the gas concentration calculating means exceeds a second threshold that is a threshold lower than the first threshold. If the gas concentration exceeds the second threshold, the sensor drive is performed. Drive period changing means for causing the means to drive the gas sensor at a second drive period shorter than the first drive period;
And a control device for a battery type gas alarm.

Images