JP2007272439A - Fire detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fire detector capable of continuously reading sensor signals of a sensor even if the sensitivity of the sensor varies. <P>SOLUTION: The fire detector includes: a sensor 1 for sensing the infrared radiation of fire flames and outputting a sensor signal according to the amount of the infrared radiation; a plurality of amplifying parts 5, 6 for amplifying the sensor signal of the sensor 1 in steps and outputting a plurality of amplification signals with different degrees of amplification; and a control circuit part 10 for selecting one of the plurality of amplification signals from the plurality of amplifying parts 5, 6 and determining whether or not there is a fire. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to, for example, a fire detector that detects infrared rays by detecting a fire.

Some conventional fire detectors increase the sensitivity of a sensor (scattered light smoke detector) when the smoke concentration is low, and decrease the sensitivity when the smoke concentration is high. For example, if the smoke density changes within the range set for each sensitivity, and that sensitivity exceeds the dynamic range of the A / D converter on the rear stage side, etc., this is discriminated by a threshold value and switched to the next sensitivity setting data Therefore, the dynamic range is used again (for example, see Patent Document 1).
Japanese Patent Publication No. 5-10718 (page 3, FIGS. 1 to 3)

In the conventional technique described above, the situation must be confirmed after switching the sensitivity, and if there is a problem, a complicated determination such as returning the sensitivity to the original is required.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fire detector that can continuously read a sensor detection signal even if the sensitivity of the sensor changes. .

  A fire detector according to the present invention includes a sensor that outputs a signal based on a fire detection, a plurality of amplification units that amplify the output signal of the sensor in stages, and output a plurality of amplified signals having different amplification degrees. And a fire discriminating unit that discriminates whether or not there is a fire by selecting one of the plural amplified signals from the plural stages of amplifying units.

  In the fire detector according to the present invention, the fire discriminating unit selects an amplification signal having a high amplification degree from among a plurality of amplification signals and compares it with a predetermined switching level, and the amplification signal having the high amplification degree exceeds the switching level. At this time, a fire is discriminated using an amplified signal having a low amplification degree, and when an amplified signal having a high amplification degree does not exceed the switching level, the fire is discriminated using it.

  In the fire detector according to the present invention, when the amplification signal having a low amplification level exceeds the switching level, the fire determination unit switches the amplification level of the multiple-stage amplification units from high to low.

  In the fire detector according to the present invention, after the fire determination unit switches the amplification degree of the amplification units of the plurality of stages to low, one amplification signal among the plurality of amplification signals is lowered from a return level lower than the switching level. At this time, the amplification degree of the plural stages of amplification units is returned from low to high.

  In the fire detector according to the present invention, one of a plurality of amplification signals has the same amplification level before and after switching the amplification level of the plurality of amplification units from high to low, or before and after returning the amplification level from low to high. is there.

  In the fire detector according to the present invention, the plurality of amplification units include a first amplification unit and a second amplification unit provided on the output side of the first amplification unit. A predetermined amplified signal is output from the amplifying unit to the fire discriminating unit and the second amplifying unit, respectively, and an amplified signal further amplified to a power of 2 is output from the second amplifying unit to the fire discriminating unit. When the degree is high, an amplified signal obtained by amplifying a predetermined amplified signal from the first amplifying unit to the nth power of 2 is output to the fire discriminating unit and the second amplifying unit, respectively. The amplified signal amplified by multiplication is output to the fire discrimination unit.

  The fire detector according to the present invention switches in a hysteresis manner when the amplification degree is switched from high to low and when the amplification degree is restored.

  In the present invention, one amplification signal is selected from among a plurality of amplification signals from a plurality of amplification units. Therefore, since the amplified signal based on the change in the sensing signal of the sensor can be read continuously, the variation pattern of the sensing signal can be recognized and the fire can be accurately determined by a predetermined fire detection algorithm.

FIG. 1 is a block diagram of a fire detector showing an embodiment of the present invention, and FIG. 2 shows a transition of an output pattern of an amplified signal based on a comparison between an amplified signal of the fire detector and a signal switching level or an amplification switching level. FIG.
The sensor 1 shown in FIG. 1 is composed of, for example, a sensor in a carbon dioxide resonance band. When a fire breaks out in a preset alert area, the sensor 1 senses the infrared rays of the flame and outputs a sensing signal based on the amount of infrared rays. The infrared light has a frequency band of 1 Hz to 10 Hz due to flickering of flame. A BPF (band pass filter) 2 passes a sensing signal (1 Hz to 10 Hz) from the sensor 1 and attenuates signals in other frequency bands. The first-stage amplifier 3 amplifies the sense signal that has passed through the BPF 2 by, for example, 40 times. The BPF 4 passes the sense signal amplified by the amplifier 3.

  When the sense signal from the BPF 4 is input, the second-stage amplifier 5 that is the first amplification unit amplifies the amplifier with 320 times higher amplification together with the first-stage amplifier 3, for example. 6 and output to the control circuit unit 10 as an amplified signal HA. When the amplification switching signal is input, for example, the amplification is switched to a low amplification factor of 20 times together with the first-stage amplifier 3 and output to the third-stage amplifier 6, and the amplified signal LA is supplied to the control circuit unit 10. Output. Further, when the amplification level restoration signal is input, the amplification level is restored again to 320 times and output to the third stage amplifier 6 as described above, and also output to the control circuit unit 10 as the amplification signal HA. To do. The amount of change in amplification at the time of switching from low amplification to high amplification is 16 times (2 4 times).

  The third-stage amplifier 6 that is the second amplification unit amplifies the sense signal amplified by the second-stage amplifier 5 by 16 times (2 to the fourth power), for example. When the amplification degree of the first-stage amplifier 3 and the second-stage amplifier 5 is 320 times in total, it is amplified 5120 times in total for all the amplifier stages, and is output to the control circuit unit 10 as an amplified signal HB. When the amplification degree of the first-stage amplifier 3 and the second-stage amplifier 5 is 20 times in total, it is amplified 320 times in total for all the amplifier stages, and is output to the control circuit unit 10 as an amplified signal LB.

  The control circuit unit 10 includes an A / D converter 11 that takes in a plurality of amplified signals HA, HB or LA, LB having different amplification levels and converts them into a digital signal, and, for example, a microcomputer 12 having the function of a fire determination unit. For example, an amplification switching level of 2.25 V, an amplification return level of 0.75 V, and a signal switching level of 2.25 V are set in the microcomputer 12. The amplification level switching level (2.25V) is a threshold value for determining whether to switch from high amplification level to low amplification level, and the amplification level return level (0.75V) is low amplification level to high amplification level. This is a threshold value for determining whether or not to return at regular intervals. Therefore, there is a difference of 1.5 V between the amplification switching level and the amplification restoration level, and the amplification does not change frequently due to fluctuations in the amount of infrared rays at the time of fire, and can always be sampled at predetermined intervals. . The signal switching level (2.25V) is a threshold value for determining whether to switch from the amplified signal HB to HA.

  The fire discrimination by the microcomputer 12 will be described in detail when the operation is explained. As shown in FIG. 2, each amplified signal is read and selected and discriminated. First, the digital values (voltages) of the amplified signals HB (5120 times) and HA (320 times) are sampled at predetermined intervals (for example, 20 mS to 100 mS). When the digital value of HB does not exceed the signal switching level (2.25 V), the digital value of the amplified signal HB is selected, while when the digital value of HB exceeds the signal switching level (2.25 V), The digital value of the amplified signal HA is sampled. Further, when the digital value of HA exceeds the amplification level switching level (2.25V), the amplification level switching signal is output to the second stage amplifier 5, and the low amplification level amplification signals LB (320 times) and LA ( (20 times) digital values are sampled respectively. When the digital value of LB does not exceed the signal switching level, the digital value of the amplified signal LB is sampled. On the other hand, when the digital value of LB exceeds the signal switching level, the digital value of the amplified signal LA is selected. Further, when the digital value of LA decreases and becomes lower than the amplification level return level (0.75 V), the amplification level return signal is immediately output to the second-stage amplifier 5, and the amplified signals HB and HA are output. Each digital value is sampled. When the digital value of HB does not exceed the signal switching level, the digital value of the amplified signal HB is selected. On the other hand, when the digital value of HB exceeds the signal switching level, the digital value of HA is selected. As described above, HB and HA or LB and LA are always sampled at the same time, and which one of these two signals is left to be selected is determined using the signal switching level, and the selected amplified signal is used. Whether a fire is detected or not is determined by a predetermined fire detection algorithm.

  The amplification signal is switched to a signal with a low amplification degree, such as HB → HA → LB → LA, when the saturation state is caused by an increase in the amount of infrared rays of the flame, and conversely, LA → LB → HA → HB. The signal is switched to a signal with a high degree of amplification when it becomes difficult to distinguish it from flames due to a decrease in the amount of infrared rays, in order to continuously recognize the increase or decrease in the amount of infrared rays, that is, the intensity of infrared rays caused by flickering of flames is there.

Next, in the fire detector configured as described above, the amplification signal selection timing at the time of fire detection will be described with reference to FIG. FIG. 3 is a waveform diagram for explaining the selection timing of the amplified signal in the fire detector of the embodiment.
When a fire breaks out in a preset alert area, the sensor 1 senses the infrared rays of the flame and outputs a sensing signal based on the amount of infrared rays to the BPF 2. The BPF 2 passes an infrared sensing signal having a preset frequency band of 1 Hz to 10 Hz and outputs it to the first-stage amplifier 3. The amplifier 3 amplifies the sensing signal input through the BPF 2 by, for example, 40 times, and outputs the amplified signal to the second-stage amplifier 5 through the BPF 4. Since the amplification degree switching signal is not inputted to the amplifier 5, the inputted sensing signal is amplified to, for example, 320 times the high amplification degree, outputted to the third stage amplifier 6, and at the same time as A of the control circuit unit 10. / Output to the D converter 11 as an amplified signal HA. The third-stage amplifier 6 further amplifies the sense signal amplified by 320 times by 16 times (5120 times) and outputs the amplified signal to the A / D converter 11 as an amplified signal HB.

  When the amplified signals HA and HB are input to the A / D converter 11, the microcomputer 12 of the control circuit unit 10 samples the digital values (voltages) at predetermined intervals (20 ms to 100 ms) and also digital values of HB. And the signal switching level (2.25V). The digital value of the amplified signal HB is compared with the signal switching level, and if the digital value exceeds the signal switching level, it is determined that there is a possibility of exceeding the saturation level (3V), and the data of the amplified signal HB is discarded. The amplified signal HA is selected. This is a case where the amount of infrared rays increases due to flickering of the flame, and the digital value of the amplified signal HB increases accordingly.

  Similarly to the above, when the digital value of the amplified signal HA exceeds the amplification level switching level, the microcomputer 12 also determines that there is a possibility that the saturation level (3V) may be exceeded in this case, and the amplification level switching signal is set in two stages. Output to the amplifier 5 of the eye. Since the amplified signals LB and HA have the same amplification level, in the sampling after switching to a low amplification level, the LB exceeds the signal switching level due to an increase in the sensing signal, so the amplified signal LA is selected. Further, when the digital value of the amplified signal LB becomes lower than the amplification level return level when the amplification level is low, it is determined that it is difficult to discriminate the flame based on the amount of infrared rays when the amplification level is low. Is output and switched to high amplification. When sampling after switching to high amplification level, the amplified signal HB exceeds the signal switching level, the digital value of the amplified signal HA is selected, and when it does not exceed the signal switching level, the digital value of the amplified signal HB is selected. To do. Depending on whether the digital value of the selected amplified signal is sampled from LA, LB, HA, or HB, continuous data is obtained by multiplying the digital value by a correction coefficient proportional to the inverse of each amplification degree.

  As described above, according to the embodiment, when the sensor 1 senses the infrared rays of the flame, the sensor 1 monitors the amplified signal HB having the highest amplification degree, and when the amplified signal HB is saturated, the amplified signal HA that is one step lower in amplification degree is output. When the amplified signal HA is saturated, the amplification level is switched from high to low, and the amplification signal LA having the lowest amplification level is read and monitored. When it becomes difficult to discriminate, the amplification signal is selected in a stepwise manner, and the amplification is switched in a hysteresis manner. Even if the amount of infrared rays due to flickering changes, it can be read continuously, the fluctuation pattern of the sensing signal can be recognized, and the fire can be accurately determined by a predetermined fire detection algorithm.

  In the above-described embodiment, a single-wavelength fire detector including one infrared sensor is shown, but the present invention can also be applied to a multi-wavelength fire detector including a plurality of infrared sensors.

It is a block block diagram of the fire detector which shows embodiment of this invention. It is a figure which shows the transition of the output pattern of the amplification signal based on contrast with the amplification signal of a fire detector, and a signal switching level or an amplification degree switching level. It is a wave form chart for explaining selection timing of an amplification signal in a fire detector of an embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor, 2 BPF, 3rd stage amplifier, 4 BPF, 5 2nd stage amplifier, 6 3rd stage amplifier, 10 control circuit part, 11 A / D converter, 12 microcomputer

Claims (7)

A sensor that outputs a signal based on a fire detection;
Amplifying the output signal of the sensor in stages, and a plurality of amplification units that output a plurality of amplified signals having different amplification degrees;
A fire detector comprising: a fire discriminating unit that selects one of the plurality of amplified signals from the plurality of amplifying units and discriminates whether or not there is a fire.   The fire discriminating unit selects an amplified signal having a high amplification level from among a plurality of amplified signals and compares the amplified signal with a predetermined switching level. When the amplified signal having the high amplification level exceeds the switching level, the amplification having a low amplification level is performed. 2. The fire detector according to claim 1, wherein a fire is discriminated using a signal, and a fire is discriminated by using the signal when a high amplification signal does not exceed the switching level.   3. The fire detector according to claim 1, wherein when the amplification signal with a low amplification level exceeds the switching level, the fire determination unit switches the amplification level of the plurality of amplification units from high to low. .   The fire determination unit switches the amplification level of the amplification units of the plurality of stages to low, and then when one amplification signal among the amplification signals falls below a return level lower than the switching level, The fire detector according to claim 3, wherein the amplification degree of the amplification unit is returned from low to high.   The one or more of the plurality of amplified signals have the same amplification level before and after switching the amplification level of the plurality of amplification units from high to low, or before and after returning the amplification level from low to high. The fire detector according to any one of 2 to 4.   The amplifying units of the plurality of stages include a first amplifying unit and a second amplifying unit provided on the output side of the first amplifying unit, and when the amplification degree is low, predetermined amplification is performed from the first amplifying unit. A signal is output to each of the fire determining unit and the second amplifying unit, and an amplified signal further amplified to 2 n times is output from the second amplifying unit to the fire determining unit, and the amplification degree is high. The amplified signal obtained by amplifying a predetermined amplified signal from the first amplifying unit to a power of 2 is output to the fire discriminating unit and the second amplifying unit, respectively, and the second amplifying unit further outputs 2 n The fire detector according to any one of claims 2 to 5, wherein an amplified signal amplified by multiplication is output to the fire discrimination unit. The fire detector according to any one of claims 2 to 6, wherein when the amplification degree is switched from high to low and when it is restored, it is switched in a hysteresis manner.

Images