JP2009026110A - Fire alarm - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of error alarm due to moisture condensation in a fire alarm. <P>SOLUTION: A measurement means is composed of a microcomputer 11, a sample and hold circuit 13 and an A/D conversion circuit 14, and a smoke sensor 12 acquires a measurement value. Under the control of the microcomputer 11, smoke is measured in a smoke detecting sampling period of a four-second interval in a monitoring mode. When the measurement value exceeds only a first threshold (10%/m), a smoke judgment count is increased by "1". Sudden rise of a measurement value of the smoke sensor 12 due to irregular reflection on water drops caused by dew condensation is detected. When the measurement value exceeds a second threshold (20%/m) at first from a value less than the first threshold (safety range), the counting processing of the smoke judgment count is canceled and fire alarm processing is controlled to cancel an alarm mode. The number of cancels is counted, and when the number of cancels becomes a prescribed number of times, the counting processing of the smoke judgment count is restarted and the monitoring mode can be shifted to the alarm mode by delaying shift time only by the number of cancels. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fire alarm device that is installed in a house or the like and outputs a fire alarm signal to the outside when a fire occurs in the room or the like. In particular, the detection or detection of a fire by detecting smoke concentration with a smoke sensor. The present invention relates to a fire alarm that performs an alarm.

  2. Description of the Related Art Conventionally, there is a fire alarm that detects smoke caused by a fire or the like with a photoelectric smoke sensor. In such a photoelectric fire alarm device, the measurement light is irradiated to the atmosphere of the alarm device installation space taken into the sensor housing portion of the alarm device by a light emitting element such as an LED, and the fine particles present in the atmosphere are irradiated. The diffused diffused light is received by a light receiving element such as a photodiode, and the concentration of fine particles existing in the atmosphere, that is, the smoke concentration is measured as a photoelectric output signal.

However, this type of fire alarm needs to prevent false alarms. For example, in Japanese Patent Laid-Open No. 2006-146738 (Patent Document 1), there is an example in which a temperature sensor is provided, and when there is no increase in temperature, it is determined that there is a false alarm, or the smoke concentration is 2.5 to 5%. A method of discriminating between smoke and water vapor based on the elapsed time until reaching / m is disclosed.
JP 2006-146738 A

  For example, when the fire alarm is installed in a kitchen, a false alarm due to steam generated from cooking, an electric pot, a rice cooker or the like is assumed. However, in the case of Patent Document 1, it is assumed that a recognition error occurs depending on the flow of water vapor and the amount of water vapor generated.

  The present invention pays attention to the difference in characteristics between smoke and water vapor, and an object of the present invention is to reduce false alarms due to rising water vapor in a photoelectric fire alarm.

  The fire alarm device according to claim 1 includes a measuring means for measuring the output of the smoke sensor at a set sampling period for detecting smoke, and a safety value in which a measured value obtained by the measuring means is less than a preset threshold value. In the case of a fire alarm provided with alarm means for performing fire alarm processing when the measured value exceeds the safety range without performing fire alarm processing, the threshold value defining the upper limit of the safety range is set. A first threshold value and a second threshold value that is larger than the first threshold value by a predetermined width are set, the current measurement value and the immediately previous measurement value among the measurement values in the sampling period are determined, and the immediately preceding measurement value is It is characterized in that the fire alarm process is regulated when the current measured value is equal to or greater than the second threshold value within a safe range.

  The fire alarm device according to claim 2 is the fire alarm device according to claim 1, and when the fire alarm processing is regulated, the subsequent measurement value continuously exceeds the second threshold value a predetermined number of times. In this case, the restriction of the fire alarm processing is canceled.

  In addition, in the fire alarm device according to claim 1 or 2, the sampling period for smoke detection is about 4 seconds, and the measurement value in the measurement means is in units of [% / m] representing the smoke density in terms of light extinction rate. In this case, it is preferable that the first threshold value is 10% / m, the second threshold value is 20% / m, or a value approximate to the value.

  Usually, smoke generated by a fire is accompanied by heat, so it rises toward the ceiling surface and diffuses toward the wall surface. On the other hand, the water vapor generated by the electric pot or the like rises toward the ceiling surface, the temperature itself is lowered, the water vapor particles are reduced, and diffused into the atmosphere. Further, the generated water vapor is not stable, is visibly shaded, and the amount entering the smoke detector due to the surrounding convection is not constant.

  In particular, the inventor of the present invention has found that the influence of water vapor generated in a fire alarm device due to water vapor contributes to false alarms. For example, as shown in FIG. 8, water vapor may enter a sensor housing 2 called a labyrinth that incorporates a smoke sensor of a fire alarm, and water vapor may condense in the sensor housing 2. The smoke sensor 12 diffuses light from the light emitting unit 12a due to smoke or the like, and the diffused light is received by the light receiving unit 12b. It was found that the amount of light received by the light receiving portion 12b was changed by being scattered or reflected, and erroneously recognized that smoke was detected.

  Therefore, the inventor of the present invention has verified the difference between the characteristics when condensation occurs and the characteristics when smoke enters as follows regarding the change in the measured value by the smoke sensor of the fire alarm. Measured when the detection interval (sampling period) of the measured value of the smoke sensor of the fire alarm is 10 ms, 4 seconds, and 10 seconds, and when water vapor is generated from below the fire alarm and condensation occurs due to the water vapor. The results are shown in FIG. FIG. 6B is an enlarged view of a portion A surrounded by a wavy line in FIG.

  In FIG. 6, when the sensor output (measured value) at intervals of 10 milliseconds is observed, it rapidly rises within 1 second and exceeds 10% / m. This 10% / m is a fire determination threshold (first threshold). Normally, a fire alarm performs a detection operation at intervals of about 4 to 10 seconds. For example, if a detection is performed at intervals of 4 seconds and the first threshold is exceeded three times, it is determined that a fire has occurred and an alarm is issued. It becomes false information at the point of 16 seconds.

  Next, as an example of a normal fire, an example in which a futon is burned by an electric stove is shown in FIG. FIG. 7 (B) is an enlarged view of a portion A in FIG. 7 (A). As shown in this figure, in the case of smoke, no rapid movement was confirmed as described above. Therefore, it has been found that it is possible to discriminate between the case where condensation due to water vapor is generated and the case where smoke is detected by detecting that the measured value rises rapidly.

  Therefore, the present invention provides a first threshold value (for example, 10% / m) that defines the upper limit of the safety range in which no fire occurs, and a second threshold value (20%) that is larger than the first threshold value by a predetermined width (for example, 10% / m). % / M) is set, the previous measured value is within the safe range (less than the first threshold value), and the current measured value is greater than or equal to the second threshold value, a sudden rise is detected. Therefore, fire alarm processing was regulated to prevent false alarms. The fire alarm process is, for example, a process of issuing an alarm when an event exceeding the first threshold continues for a predetermined number of times. To restrict the fire alarm process, the condition for issuing this alarm is changed. This is a process such as delaying the alarm.

  According to the fire alarm device of the first aspect, it is possible to discriminate between the measurement value due to smoke and the measurement value at the time of dew condensation of water vapor, and to prevent false reports due to dew condensation of water vapor.

  According to the fire alarm device of claim 2, in addition to the effect of claim 1, the alarm can be regulated so as to delay the false alarm.

  Next, an embodiment of the fire alarm of the present invention will be described. FIG. 1 is a front view (FIG. 1 (A)) and a side view (FIG. 1 (B)) of a fire alarm device according to an embodiment of the present invention, and FIG. 2 is a block diagram of the main part of the fire alarm device. The fire alarm of this embodiment includes a main body case 1, a cylindrical sensor housing 2 formed to protrude from the front surface 1 a of the main body case 1, and the main body case 1 facing the main body case 1 so as to sandwich the sensor housing 2. It has the panel 3 as a provided baffle plate. This fire alarm is a wall-hanging type, and is installed with the back surface portion 1b of the main body case 1 in close contact with the wall of the room and the sensor housing 2 side up.

  A smoke sensor 12 similar to that shown in FIG. 8 is accommodated in the sensor housing 2. The sensor housing 2 has a plurality of blade plates 2 a, 2 a,... Erected over the entire circumference of the sensor housing 2, and the gap between the blade plates 2 a, 2 a is in one direction toward the inside of the sensor housing 2. A rotating passage is formed. Then, smoke and water vapor flow into the sensor housing 2 from the gap (passage) between the blades 2a, 2a,. The smoke sensor 12 is a photoelectric sensor capable of measuring the smoke density, and this smoke density corresponds to the light attenuation rate in a light-attenuating densitometer. Similarly to the above, the light attenuation rate is expressed in units of [% / m].

  As shown in FIG. 2, the fire alarm device includes a microcomputer (hereinafter referred to as a microcomputer) 11, a smoke sensor 12, a sample hold circuit 13, an A / D conversion circuit 14, a timer 15, an alarm unit 16, an EEPROM 17, and a battery 18. Etc. The alarm unit 16 includes a speaker or the like for issuing a fire alarm (ringing). The EEPROM 17 stores threshold values to be compared for various determinations, various setting values, and the like. The battery 18 is a driving power source for the entire fire alarm.

  The microcomputer 11 includes a CPU 11a that performs various processes according to a processing program, a ROM 11b that stores a program for processing performed by the CPU 11a, a work area that is used in various processes in the CPU 11a, and a data storage area that stores various data. These elements are connected by a bus line.

  The smoke sensor 12 includes a light emitting unit 12a including an LED and a light emission control circuit, and a light receiving unit 12b including a photodiode and an amplifier circuit. The light emitting unit 12a is controlled to emit light by the microcomputer 11. The light receiving unit 12b receives light from the light emitting unit 12a. The sample hold circuit 13 is connected to the light receiving unit 12b, samples the light reception output of the light receiving unit 12b and holds it until the next light emission, and the A / D conversion circuit 14 changes the output of the sample hold circuit 13 from an analog signal to a digital signal. And input to the microcomputer 11. The timer 15 is connected to the microcomputer 11, and the microcomputer 11 determines the sampling timing and the like based on the timer interrupt signal of the timer 15.

  That is, the microcomputer 11 controls light emission of the light emitting unit 12a of the smoke sensor 12 according to the sampling cycle, and takes in the output signal of the light receiving unit 12b as a measurement value at each measurement timing of the sampling cycle. The microcomputer 11, the sample hold circuit 13, and the A / D conversion circuit 14 correspond to “measuring means”.

  The outline of the processing of this embodiment is as follows. First, in the monitoring mode for monitoring the occurrence of a fire, the measured value by the smoke sensor 12 is acquired at the sampling frequency for smoke detection (at intervals of 4 seconds). The first threshold value, which is the determination criterion for the measurement value, is 10% / m, the second threshold value is 20% / m, and the area where the smoke sensor measurement value is less than the first threshold value is the safe range.

  In the monitoring mode, if the measured value exceeds the safe range (less than the first threshold), it is determined whether the second threshold is exceeded. If the measured value exceeds the safety range and is less than the second threshold, it is determined that smoke has been detected, and fire alarm processing is performed. In this fire alarm processing, the number of times of determination is counted by “smoke determination count” in order to allow a delay until the alarm mode is set. When the “smoke determination count” reaches a predetermined value (eg, “3”), an alarm is issued as an alarm mode.

  On the other hand, when the measurement value exceeds the second threshold value for the first time in the monitoring mode, it is determined whether the previous measurement value (the previous measurement value) was within the safe range. And if the last measured value is a safe range, a fire alarm process will be restrict | limited. That is, if the previous measurement value is in the safe range and the current measurement value exceeds the second threshold value, it is determined that a rapid increase in the measurement value due to condensation has been detected, and the fire alarm process is limited. This restriction on fire alarm processing cancels the counting of the “smoke judgment count” even if the measured value exceeds the safe range, and it is used for branch judgment to avoid the processing of counting this “smoke judgment count”. The count value of “Smoke judgment count cancellation” is used. Note that “smoke determination count cancellation” is initially “0”, and is incremented (increased by 1) every time the second threshold value is exceeded. Then, the fact that the event exceeding the second threshold is the first is determined by the count value of “smoke determination count cancellation” being “0”. This logic is referred to as “logic A”. Further, when the “smoke determination count cancellation” reaches a predetermined count value (for example, “3”), the restriction of the fire alarm process is canceled by counting the “smoke determination count”. This logic is referred to as “logic B”.

  3 and 4 are main part flowcharts of the control program of the microcomputer 11 of the fire alarm device in the embodiment, and the operation will be described based on the same figure. Note that registers for storing values used for processing, such as the count values of “smoke determination count” and “smoke count cancel”, are preset in the RAM 11c. Further, values such as a threshold value are stored in the EEPROM 17 (or the ROM 11b). The process of FIG. 3 is an example in which both “logic A” and “logic B” logic are implemented.

  In the process of FIG. 3, the elapse of 4 seconds is monitored as the “monitoring mode” in step S1. When 4 seconds elapse, the measurement value in the smoke sensor 12 is acquired in step S2, and it is determined in step S3 whether the measurement value is equal to or greater than the first threshold value. If the measured value is not equal to or greater than the first threshold value, no smoke or water vapor (condensation) has been detected, so the smoke determination count cancellation is set to “0” in step S4 and the monitoring mode is continued. If the measured value is greater than or equal to the first threshold, it is determined in step S5 whether the measured value is greater than or equal to the second threshold. If the measured value is not greater than or equal to the second threshold, the process proceeds to step S8, and if it is greater than or equal to the second threshold, the process proceeds to step S6.

  In step S6, it is determined whether or not the smoke determination count cancellation is "0". If the determination is Yes, the second threshold value is exceeded for the first time, so in step S7 whether the previous measured value was within the safe range. judge. If the previous measurement value is not in the safe range, the smoke determination count is incremented in step S8 as fire alarm processing, and the process proceeds to step S11. And if the last measured value is a safe range, it will progress to step S9 in order to regulate a fire alarm process. If the determination in step S6 is No, it is a case where the second threshold value has been exceeded, so the process proceeds directly to step S9.

  In step S9, as the process of logic B, it is determined whether the smoke determination count cancellation is “3”. If the determination is Yes, the process proceeds to step S8 to cancel the restriction of the fire alarm process. If so, the smoke determination count cancellation is incremented in step S10 to restrict the fire alarm process, and the process proceeds to step S11.

  In step S11, it is determined whether or not the smoke determination count has become "3". If the smoke determination count does not have to be "3", the process returns to step S1. If the smoke judgment count is “3”, the process proceeds to the alarm mode of FIG.

  In the process of FIG. 4, it is monitored in step S21 that 4 seconds have elapsed since the start of ringing in the “alarm mode”. When 4 seconds elapse, it is determined whether or not the alarm is continued in step S22. That is, it is determined whether or not the smoke determination count is “0”. If the smoke determination count is not “0”, the measurement value in the smoke sensor 12 is acquired in step S23. Next, in step S24, it is determined whether or not the measured value (smoke density) is greater than or equal to the first threshold value. If it is greater than or equal to the first threshold value, the process returns to step S21, and if not greater than the first threshold value, the smoke determination count is decremented in step S25. Return to step S21. When the smoke determination count becomes “0” in step S22, the smoke determination count cancellation is set to “0” in step S26, and the process returns to the “monitoring mode” in FIG.

  In the above processing, both logic “logic A” and “logic B” are executed, but logic B may be omitted.

  FIG. 5 is a diagram showing an example of the verification result of the logic of the embodiment. When the logic of the embodiment is applied to the measured value of water vapor in FIG. 6 (A), “logic A” and “ It is the result of comparing the case where “logic B” was not executed (equivalent to the prior art). FIG. As in FIG. 6 (A), the measured values for each sampling period of 10 milliseconds and 4 seconds are shown. B of FIG. Is a 4-second cycle in the monitoring mode, and “c. Is a 4-second period in the monitoring mode and only “logic A” is set, d. Indicates a case where “logic A and logic B” are present in a 4-second cycle in the monitoring mode.

  b. In this case, at the timing of the 8th second, the measured value becomes equal to or greater than the second threshold (20% / m) (and the first threshold), the smoke determination count becomes “1”, and the determination count further reaches the 12th second. "2", and "3" in the 16th second. As a result, the alarm mode is set at about 16 seconds and the sounding state (shaded portion) is obtained.

  c. In the case of, after the smoke concentration (sensor output) rises rapidly, the measured value becomes greater than or equal to the second threshold at the timing of the eighth second, and the previous measured value (fourth second) is within a safe range that is less than the first threshold. Therefore, the smoke determination count cancellation (number of cancellations) is “1”. After that, if the measured value continues to exceed the second threshold, the smoke determination count cancellation (number of cancellations) becomes “2, 3”, and the smoke determination count is not counted, so the alarm mode is not entered, and false alarms due to water vapor condensation are prevented. ing.

  d. In the case of c. As in the case of, the smoke judgment count cancellation (number of cancellations) is “1” at the 8th second, then “2, 3”, but the smoke judgment count cancellation (number of cancellations) is “3” at the 20th second. For this reason, the smoke determination count is “1”, the determination count is “2, 3”, and the alarm mode is entered and the ringing state is reached at 28 seconds. That is, b. Compared with, it is possible to delay until the ringing state. In the case of this 4-second interval, a delay of about 20 to 24 seconds can be applied before ringing. Further, even when the first threshold value is exceeded and then the first threshold value is stabilized due to overshoot or the like, a delay of 12 to 20 seconds can be applied before ringing.

It is the front view and side view of the fire alarm which concern on embodiment of this invention. It is a principal part block diagram of the fire alarm. It is a flowchart of the monitoring mode in embodiment. It is a flowchart of the alarm mode in an embodiment. It is a figure which shows an example of the verification result of the logic in embodiment. It is a figure which shows the example of the measured value of the smoke sensor with respect to water vapor | steam. It is a figure which shows the example of the measured value of the smoke sensor with respect to smoke. It is a figure which shows the state of the dew condensation in the housing of a smoke sensor.

Explanation of symbols

11 Microcomputer (measuring means, warning means)
12 Smoke sensor 13 Sample hold circuit (measuring means)
14 A / D conversion circuit (measuring means)

Claims (2)

If the measuring means for measuring the output of the smoke sensor at the set sampling period for smoke detection, and the measured value obtained by the measuring means is within a safety range below a preset threshold, fire alarm processing is not performed In addition, in a fire alarm device comprising alarm means for performing a fire alarm process when the measured value exceeds the safety range,
The threshold value that defines the upper limit of the safety range is set as a first threshold value, and a second threshold value that is larger by a predetermined width than the first threshold value is set,
When the current measurement value and the previous measurement value among the measurement values in the sampling period are determined, the previous measurement value is within the safety range, and the current measurement value is equal to or greater than the second threshold value. A fire alarm device characterized by regulating the fire alarm processing.   2. The control of the fire alarm processing is released when the fire alarm processing is regulated, and the subsequent measurement value continuously exceeds the second threshold a predetermined number of times. Fire alarm.

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