JPS6132195A - Fire sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fire detection device that detects not only ordinary flaming fires but also smoldering fires.

[Conventional technology]

Various fire detection devices have been proposed so far (for example,
Patent Application No. 183099/1982, Patent Application No. 14094/1983
No. 0, Japanese Patent Application No. 57-140'941). A major issue with such fire detection devices is how accurately they can detect flaming or combustion fires without malfunctioning due to sunlight or noise from low-temperature radiation sources such as stoves. Attention is being paid.

An example of such a conventional fire detection device will be described with reference to FIG.

In FIG. 2, numerals 61 and 62 are photoelectric converters, and 63.
64 is an amplifier, 65.66 is a frequency filter, 67.6
8 is a detection smoothing circuit, 69 is a comparator, 70 is an integrator, 71
is the output switching circuit.

As shown in Figure 3, the photoelectric converter in this device is shown as a curve C3 with a peak around 4 μm, where the horizontal axis is the wavelength (μm) and the vertical axis is the radiation intensity (relative level). In order to detect the carbon dioxide resonance radiation accompanying the flame, an extremely narrow band optical bandpass filter is used, for example, a center wavelength of 4 μm, 4.5 μm and a band width of 0.2 μm.

Further, as a photoelectric converter, a pyroelectric element that can be used in a wide wavelength range is usually used. Frequency filter 6
5.66 is a bandpass filter that passes flame flickering frequencies from several Hz to around 20 Hz.

The detection smoothing circuits 67 and 68 include bandpass filters 65.
The output signals of 66 and 66 are detected, smoothed, and converted into direct current. A comparator 69 compares the outputs of the detection smoothing circuit 67.6El.

For example, the photoelectric converter 61 is 4.5 μm, and the photoelectric converter 62 is 4 μm-t.
- If the flame is detected, the signal output level of the detection smoothing circuit 67 will change due to the difference in radiation intensity depending on the wavelength of the carbon dioxide resonance radiation as shown in Fig. 3.
The output level is higher than that of 8. Therefore, a signal output is generated in the comparator 69. When a signal is output from the comparator 69 for a certain period of time or more, the integrator 70 transmits the signal to the switching circuit 71 and determines whether the flame continues while preventing malfunction due to noise.

Therefore, by utilizing the saliency of the curve C8, as shown in FIG. 3, fire can be detected with high reliability based on the sunlight shown by the curve C8 and the signal from the incandescent light bulb shown by the curve C4. I can do it.

[Problem that the invention seeks to solve]

With conventional equipment, the radiation intensity of a smoldering fire, as shown by curve C2 in Fig. 3, does not have a remarkable peak of carbon dioxide gas resonance radiation, unlike that of a flaming fire, shown as curve CI. Smoldering fires cannot be detected accurately. If an attempt is made to detect a smoldering fire under such characteristics, a considerable amount of statistical processing must be carried out to make a judgment, and the implementation circuit becomes complex and expensive, and the problem arises that detection is delayed.

In addition, in conventional devices, the pyroelectric element has low sensitivity, and the response decreases at the frequency used (the higher the frequency, the lower the response), leading to a decrease in sensitivity.As mentioned above, expensive optical filters are required, resulting in high costs. There is a problem with becoming.

[Means for solving the invention]

In the present invention, the first radiation detection means detects radiation with a wavelength in the near-infrared region, the second radiation detection means detects radiation with a wavelength in the near-infrared region close to visible light, and the first radiation detection means detects radiation with a wavelength in the near-infrared region close to visible light. and a calculation means for receiving the output signals from the second radiation detection means and calculating a logical combination of the output signals based on the level difference and synchronization of these output signals, and a fire signal and a fire signal based on the combined output signal from the calculation means. A fire detection device is provided, comprising: detection means for discriminating and detecting a noise signal.

Further, in the present invention, the detector and the stage can distinguish and detect a flaming fire signal and a smoldering fire signal based on the combined output signal from the calculating means.

[Effect]

In the present invention, the first radiation detection means provides 2.3
Detects near-infrared radiation near μm, that is, radiation such as soot,
Both flaming fires and smoldering fires can be detected, and the second radiation detection means detects near-infrared rays close to visible light at around 0.9 μm (hereinafter referred to as photographic infrared rays) to detect flaming fires. and visible light noise have synchronicity in the correlation between 2.3 μm and 0.9 μm, smoldering fires do not show synchrony, and flaming fires and combustion fires have near-infrared intensity greater than photographic infrared intensity. The visible light noise utilizes the fact that the near-infrared intensity is lower than the photographic infrared intensity, and the above two types of radiation are compared to distinguish between fire and visible light noise, and between flaming fire and burning fire.

〔Example〕

The present invention will be described below with reference to the drawings.

A fire detection device of the present invention is shown in FIG. The fire detection device shown in FIG. 1 detects radiation based on the level difference and synchronization of the output signals from the first radiation detection section 1, the second radiation detection section 2, and the first and second radiation detection sections. Part 1.2
The fire detecting section 4 includes a calculation section 3 that combines and calculates the output signals of the calculation section, and a fire detection section 4 that accurately discriminates between a fire signal and noise based on the output signals of the calculation section and generates a fire detection signal.

The first radiation detection unit 1 is a lead sulfide (Pbs) photoelectric converter 1
1 and a logarithmic amplifier 12 are connected as shown. The second radiation detection section 2 has a silicon (Si) photodiode 21 and a logarithmic amplifier 22 connected as shown. FIG. 4 shows the spectral sensitivity characteristics of the Pbs photoelectric converter 11 and the St photodiode 21 as photoelectric converters, including the conventional pyroelectric element.

In Figure 4, the horizontal axis represents the wavelength (μm) and the vertical axis represents the relative sensitivity.
py indicates the characteristics of the Pbs photoelectric converter, St photodiode, and pyroelectric element, respectively. Referring to Figure 3, the radiation intensity at a wavelength of 0.9 μm in the photographic infrared region and a wavelength around 2.3 μm in the near-infrared region (the region emitted by heated carbon particles) is reversed between fire and visible light sources. It can be seen that Therefore, fire can be detected using this characteristic.

A detailed circuit of the logarithmic amplifiers 12 and 22 is shown in FIG. The logarithmic amplifier has a resistor R and a capacitor CI.

A low-pass filter section 1 in which C2 is connected as shown in the figure.
21, and a logarithmic amplification section 122 in which an amplifier Amp and diodes DI and D2 are connected in antiparallel as shown. The reason why such a logarithmic amplifier is used is that the difference in the intensity of flickering radiation between a flaming fire and a smoldering fire is extremely large, so in order to avoid saturation of the amplifier, logarithmic amplification is performed and the frequency response is adjusted to a high frequency range. This effectively reduces the amplification at the high flicker frequencies of a flaming fire. This eliminates the need for a complicated automatic gain control circuit or the like. That is, logarithmic amplifier 12.2
2 amplifies the output signal of the photoelectric converter 11.21 while logarithmically compressing it, and the gain decreases as the frequency increases.

FIG. 6 shows an example of the amplifier gain characteristic (curve G) and the infrared radiation characteristic due to a fire. The characteristic curve of the PBS photoelectric converter against ignition is shown as Fsi, the characteristic curve of the PBS photoelectric converter against smoldering is shown as 5pbs, and the characteristic curve of the Si photodiode is shown as Ssi. Therefore, a low-level combustion fire signal is amplified with a high gain in the low frequency range of the amplifier, and a high-level flaming fire signal is amplified with a low gain in a high frequency range while avoiding saturation by logarithmic compression.

The calculation unit 3 is a Schmitt trigger 31.3 for waveform shaping.
A comparator 32 having three hysteresis characteristics, and a decoder 34 which receives A, B, and C signals from these and generates an output signal as shown in FIG. 1 by a combination of the input signals.
are connected as shown. Schmitt trigger 31,
33 converts the output signal of amplifier 12.22 into a digital level. Comparator 32 also compares and converts the output signal of amplifier 12.22 into a digital level.

The decoder 34 takes in the output signals of the Schmitt triggers 31 and 33 and the comparator 32 as A, B, and C.
A logical operation is performed on the combination of logic "high" (hereinafter abbreviated as "H") and "low" (hereinafter abbreviated as "lower") of C, and a signal is output as shown in FIG. In Figure 1, ite, A, B, ChaH
L/heJL/, X, 100, ]tL level, * indicates AND.

As a result of various experiments conducted by the inventor regarding fire disasters, the vertical axis was 0.9 μm and 2.0 μm using a spectrum analyzer for flaming fires using alcohol lamps, smoldering fires using cotton thread, and visible light noise. When the coherence function COH obtained for a wavelength of 3 μm is plotted and the flicker frequency is plotted on the horizontal axis, Fig. 7 (A) to (
It was found that the flaming fire characteristic Cf and the visible light noise Cv are synchronized, but the smoldering fire characteristic Cs is not synchronized.

Therefore, based on the characteristics shown in Figure 3 and the above experimental results (Table -
I was able to analyze as shown in 1).

(Table 1) "Photo": Photographic infrared region (0.9 μm) "Near": Near infrared region (2.3 μm) According to this relationship, flaming fire, smoldering fire, and visible light noise can be distinguished. can be distinguished quite accurately.

That is, since the 0.9 μm and 2.3 μm signals of a flaming fire are synchronized, the decoder output has a high probability of occurrence of (A-B-C) or (A-B・te). In the case of a smoldering fire, there is no synchronization as described above, so (A - B・σ) or (A
-The probability of occurrence of B and C) increases.

Visible light noise is synchronous and the signal levels of 0.9μm and 2μm are inverted with fire, so (A-100・C) or (
The probability of occurrence of A −B −c> increases.

Accordingly, it is possible to discriminate between a flaming fire, a smoldering fire, and visible light noise based on the output signal from the decoder.

The details of the fire detection section 4 will be described. Differentiators 41-46
converts the output signal of the decoder 34 into sufficiently narrow pulses. This directly connects the output of the decoder 34 to the OR gate 47.
This is to avoid the possibility that if the inputs are inputted in 49, they will be continuous in time and it will be impossible to distinguish them. Pulse interval discriminator 50
．． 52 is a type of digital bandpass filter that passes only pulses at time intervals corresponding to a frequency range from several Hz to around 40 Hz. The ignition fire signal was originally 20
Although the frequency band is around Hz (Figure 7 (A))
Since the decoder 34 performs processing equivalent to full-wave detection, up to twice the frequency is allowed to pass, allowing for a margin. The pulse interval discriminator 51.53 passes only pulses with time intervals corresponding to approximately 0.1 Hz to 2 Hz in the frequency domain. These discriminators 51.5
3 is for smoldering fires, and is a kind of digital band pass filter like the above discriminator.

The UP/DOWN counter 54 receives a large UP input fire pulse and receives a visible light pulse, ie, a noise pulse, at its DOWN input, thereby performing addition/subtraction processing of the number of pulses. This is a type of digital differential integrator. When a flaming fire occurs, the probability of a fire pulse occurring is high, so the counter 54 performs a count amplification and eventually reaches a predetermined count number and outputs a pulse to the carry output C. When there is no fire, there are many visible light pulses, so the counter counts down and is cleared by borrow output.

Like the counter 54, the up/down counter 55 also processes smoking pulses and visible light pulses. If the combustion fire continues, a pulse is output to the carry output C similarly to the counter 54. In this way, by adding and subtracting the fire pulse and visible light pulse using the UP/DO1IN counter, the S/N
By improving the ratio and accumulating counts, only continuous fires can be detected.

OR gate 56 receives the output pulse from either counter 54 or 55 and drives switching circuit 57 . OR
It is also possible to separately drive the two switching circuits 57 with the pulse outputs of the counters 54 and 55 without using the gate 56, and output the flaming fire signal and the smoldering fire signal separately. The switching circuit 57 receives the pulse signal from the OR gate 56, extends the time interval to a predetermined time width, and outputs a contact to a fire receiver or the like. Swiss isotching circuit 5
The reference numeral 7 may not be a voltageless contact, but may be a transistor open collector output, a photocoupler output, or the like.

[Effects of the Invention] As described above, according to the present invention, as the photoelectric converters of the first and second radiation detection means, for example, Pbs photoelectric converters and PBS photoelectric converters each having selective spectral sensitivity characteristics for infrared wavelengths are used. By using Si photodiodes and eliminating expensive optical filters, we make effective use of their high sensitivity characteristics and detect near-infrared rays of soot radiation in the vicinity of 2.3 μm using PBS photoelectric converters. , detects both flame and smoldering, and detects photographic infrared radiation in the vicinity of 0.9 μm with a Si photodiode, and compares the intensity of these radiations to distinguish between flaming fires, smoldering fires, and visible light noise. The distinction can be made accurately. In particular, it becomes possible to accurately detect combustion fires that could not be detected with conventional devices that use radiation, and it also becomes possible to detect flaming fires with high reliability. In addition, by incorporating visible light noise into signal processing, fire detection without malfunction is possible. Further, the fire detection device of the present invention can detect a fire in a shorter time than conventional smoke detectors and heat detectors.

Further, according to the present invention, a relatively simple circuit configuration is required and an inexpensive detector can be used, so that a low-cost fire detection device can be provided.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a fire detection device as an embodiment of the present invention, Fig. 2 is a block diagram of a conventional fire detection device, Fig. 3 is a general characteristic diagram showing fire radiation intensity, and Fig. 4 is a block diagram of a conventional fire detection device. The figure shows the sensitivity characteristics of the photoelectric converter shown in Fig. 1, the detailed circuit diagram of the logarithmic amplifier shown in Fig. 1, and the detailed circuit diagram of the logarithmic amplifier shown in Fig. 1, and Fig. 6 show the frequency characteristics of the photoelectric converter shown in Fig. Diagram showing frequency characteristics, Figure 7 (A)
-(C) are characteristic diagrams showing experimental data related to the detection principle of the present invention. (Explanation of symbols) 1-first radiation detection section, 11-Pbs photoelectric converter, 12-.logarithmic amplifier, 2-.second radiation detection section, 21-.Sl photodiode, 22-.logarithmic amplifier , 3-Arithmetic unit, 3L33- Schmitt trigger, 32-Comparator, 34-Decoder, 4-Detection, 41-46-Differentiator, 47-49-OR gate, 50-53-Discriminator, 54.55- Up/down counter, 56-OR
gate, 57- switching circuit; Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Country

Claims (1)

[Claims] 1. A first radiation detection means for detecting radiation having a wavelength in the near-infrared region; a second radiation detecting means for detecting radiation having a wavelength in the photographic infrared region; a calculation means for receiving the output signals from the second radiation detection means and calculating a logical combination of the output signals based on the level difference and synchronization of these output signals; and a combination output signal from the calculation means for detecting a fire signal and noise. A fire detection device comprising: detection means for distinguishing and detecting a signal. 2. The fire detection device according to claim 1, wherein the detection means is capable of distinguishing and detecting a flaming fire signal and a smoldering fire signal based on a combined output signal from the calculating means. 3. The fire detection device according to claim 2, wherein the first radiation detection means has a lead sulfide photoelectric converter, and the second radiation detection means has a silicon photodiode. 4. A patent claim characterized in that the first and second radiation detection means have a logarithmic amplifier connected to a low-pass filter to avoid saturation of the amplifier and to reduce frequency characteristics at high frequencies. The fire detection device according to any one of items 1 to 3. 5. The detection means includes a pulse interval discriminator that discriminates the pulse width of the combined output signal from the calculation means, and a counter that receives the output of the pulse interval discriminator as input,
5. The fire detection device according to claim 4, wherein the fire detection device outputs a fire signal when a predetermined count is reached. 6. The fire detection device according to claim 5, wherein the counter is a reversible counter that uses the fire signal from the pulse interval discriminator as an addition input and a noise signal as a subtraction input. .