JPS6298224A - Flame detector - Google Patents

Abstract

PURPOSE:To accurately detect only in case an actual fire occurs by constituting the titled detector with photodetectors, integration means, a comparison means of phase with an integrated value, a flare detection part, a control part and a flame detection part. CONSTITUTION:It is integrated by the 1st integration circuit 15 when output of the 1st photodetector 2 having sensitivity to a wavelength area peculiar to a flame exceeds a prescribed value. Further, a deviation of phase between output of the 2nd photodetector 4 having the sensitivity to visible rays of light and the output of the element 2 is discriminated with a phase comparison circuit 10 and only the output for the deviated phase of the outputs of the element 2 is integrated with the 2nd integration circuit 16. Then, the values integrated with the circuits 15 and 16 are compared 18. Further, it is important to detect a flare of the flame for detecting the occurence of the flame and for this purpose, it is discriminated with a comparator 13 whether or not the output of the element 2 exceeds a prescribed reference and the number of times exceeding the reference by the flare of the flame is counted 23. Then, a flame detection means discriminates whether the flame exists or not from a counted result and a result of the comparator 18 and outputs an alarm when the flame exists.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flame detector that quickly detects the occurrence of a fire outdoors or indoors.

[Conventional technology]

It is conventionally known that the spectral emissivity of a flame has a peak due to 002 resonance radiation at a wavelength of 4.3 μm, as shown by a in FIG.

When the flame is detected by detecting this wavelength of infrared rays,
1) High sensitivity to flames, 2) Artificial light such as illumination light contains few components with a wavelength of 4.3 μm, so there is no malfunction, 3)
This has the advantage that there are no malfunctions caused by sparks from electrical discharge. Therefore, various flame detectors have already been proposed that detect the occurrence of flame by detecting fluctuations characteristic of flame in a wavelength range of around 4.3 μm.

However, even with this device, malfunctions may occur if sunlight or reflected light from sunlight or reflected light from materials with high reflectance such as metals directly enters the light receiving part, which is a problem especially when used outdoors. .

Here, sunlight reaches the ground after subtracting the absorbed energy in the atmosphere from the black body radiant energy of approximately 5700'. This vector is shown as b in Fig. 6. However, a and b in Fig. 6 are each normalized by the peak energy, so direct comparison cannot be made. In the spectrum of sunlight, CO
Due to the absorption of 2, the intensity near the wavelength of 4.3 μm is considerably smaller than the peak. Therefore, a device for detecting flames using two wavelengths, one wavelength in the visible range where the radiant energy from flames is small and the radiant energy from sunlight is large, and infrared rays at a wavelength of around 43 μm was proposed in Japanese Patent Laid-Open No. 49-128782. It is known in the publication no. However, under intense sunlight in summer, the radiation intensity may be comparable to that of a flame even at a wavelength of around 43 μm.

[Problem that the invention seeks to solve]

In the device described in JP-A-49-128782, the phase difference between the output signal of the first light-receiving element sensitive to visible light and the output signal of the second light-receiving element sensitive to infrared rays tends to be large. The system is configured to integrate the portion of the fire that occurs, and to detect a fire when this integrated value reaches a predetermined value.

However, if strong sunlight is incident and it is detected with a slight phase shift from the visible light component, it will be detected as a flame even if only interfering light is present. and,
Although this can be prevented by setting the judgment level of the integral value high, the accuracy of actual fire detection will deteriorate.

The object of the present invention is to provide a flame detector that can eliminate the drawbacks of the prior art and accurately detect only when an actual fire is occurring.

[Means for solving problems]

In order to achieve the above object, the flame detector according to the present invention includes a first light-receiving element that is sensitive to a wavelength range specific to flame, and a first light-receiving element that is sensitive to a specific wavelength range in the visible range. 2
a first integrating means for integrating the output of the first light receiving element, a phase comparison means for comparing the phases of the output of the first light receiving element and the output of the second light receiving element, and a first integrating means for integrating the output of the first light receiving element; a second integrating means that integrates only a portion out of phase with the output of the second light receiving element among the outputs of the light receiving elements; and a comparing means that compares the integral values of the first and second integrating means with each other; a fluctuation detection section that detects flame fluctuation based on the output of the first light receiving element; a counter that counts the output of the fluctuation detection section; a control unit that controls the operation of the integrating means and the counter; and a controller that determines whether or not a flame exists based on a comparison result between the output of the counter and the comparing means, and outputs an alarm when a flame exists; and a flame detection section including a judgment circuit that resets the control section when the control section is not activated. This will be explained with reference to FIG. The output of the first sensitive light receiving element 2 is integrated by the first integrating circuit 15 when it exceeds a predetermined value. Still, the phase comparison circuit 10 determines the phase difference between the output of the second light-receiving element 4 that is sensitive to visible light and the output of the first light-receiving element. Only the shifted portion is integrated by the second integrating circuit 16.

Then, the values integrated by the integrating circuits 15 and 16 are compared by the comparing circuit 18. In addition, detection of flame fluctuation is important for detecting the occurrence of flame, and for this purpose, the consulator 13 detects whether the output of the first light receiving element exceeds a predetermined reference level.
The counter 23 counts the number of times the output exceeds the reference level caused by the fluctuation of the flame. Then, based on the result of this counting and the comparison result of the comparison circuit, occurrence of flame is detected and an alarm is issued. That is, when fluctuation is detected from the count value of the counter and the integrated value of the output of the first light receiving element 2 exceeds a predetermined reference value when the two light receiving elements are out of phase, it is determined that flame has occurred. .

A control flip-flop 29 is provided for controlling the integrating circuits 15 and 16 and the counter. , I6 and the counter 23 start operating. When only the counter 23 outputs, the comparison circuit 18
．． If either of the flip-flops 20 has no output, or if the flip-flop 29 is reset after a predetermined period of time has elapsed, the output signal will reset the integrating circuit and the counter.

[Effect]

If only interfering light such as sunlight is present and no flame is present, the output of the first light receiving element will also be produced slightly, which may be slightly out of phase with the output of the second light receiving element. Therefore,
Although the integral values of the first and second integrating means both increase, it is determined whether the light is a flame or not based on the ratio of both integral values, so that it is clearly determined that the light is interference light. In the conventional example, if the integral value of the second integrating means increases, there is a possibility that it will be detected as a flame, but in the present invention, such erroneous detection does not occur.

Furthermore, when flame and interfering light coexist, the phase shift between the outputs of both light receiving elements is larger than when only interfering light is present. The integral value of the second integrating means becomes relatively large compared to when only the interfering light is present, and the occurrence of flame can be detected accurately. Furthermore,
When only flame exists, there is almost no output from the second light receiving element, so the ratio of both integral values is approximately 1, and therefore it is clearly detected as a flame.

Furthermore, erroneous detection of short-time infrared light noise incident on the first light receiving element is prevented by counting the number of flame fluctuations.

In addition, due to the reset function of the detection means, when it is determined that there is no flame, the detection means is immediately reset so that a response can be taken to the next phenomenon, such as the occurrence of a fire, without any delay in detection.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the flame detector of the present invention, and 2 is an infrared sensor sensitive to infrared rays at a wavelength of around 43 μm, which has, for example, spectral transmittance characteristics as shown in FIG. It consists of a thermosil, thermistor, or pyroelectric element arranged to receive the light that has passed through the infrared bandpass filter. 4 is a visible light sensor that is sensitive to visible light, and both sensors 2.4 are placed close to each other or at positions conjugate to each other with respect to the object to be detected. .8 is an amplifier that amplifies the output signal of each sensor 2.4, and a part that matches the time constant of each sensor 2.4;
It consists of a part that selectively amplifies only the frequency component of 3 to 30 Hz, which is characteristic of flame, of the output signals of both sensors 2.4. 1
Reference numeral 0 denotes a phase comparator circuit to which the outputs of both amplifiers 6.8 are inputted, and which compares the phases of both output waveforms, and is configured as shown in FIG. 3, for example. In Fig. 3, CPl is a comparator that outputs "H" when the output a of the amplifier 6 is positive and "L" when it is negative, and CF2 is a comparator that outputs "H" when the output a of the amplifier 6 is positive or when the output a of the amplifier 8 is positive or O. C20 is a comparator that outputs "L" when the absolute value is smaller than a predetermined value and "H" when it is negative, and "H" when the output of the amplifier 8 is positive, and "H" when it is negative. Or, it is a comparator that outputs L'''' when the absolute value is O (when the absolute value is smaller than a predetermined value).The outputs of the comparator/S regulators CP1 and CF2 are input to the OR circuit via the AND circuit section. On the other hand, the output of the comparator CP1 is input to the AND circuit AN2 via the inverter IV, and the output of the connominator CP3 is input as is to the AND circuit AN2.
The output of is input to the OR circuit OR.

With this configuration, the output C' of the phase comparison circuit 10
(In other words, the output cI of the OR circuit OR) is "H" when the absolute value of the output is smaller than the output when only flame exists.
”, and if the output a is larger than when only the flame exists but the signs of the output a and output are opposite, the output becomes “H”; otherwise, the output becomes “L”. That is, the judgment levels of the connominators CP2 and C20 are slightly offset to the positive side or the negative side depending on the magnitude of the output when only the flame is present as described above.

Returning to FIG. 1, 12 is a full-wave rectifier circuit that performs full-wave rectification of the output a of the amplifier 6, and 13 is a condenser that combines the output of the full-wave rectifier circuit with a predetermined reference level value v1. Compare with and output if it exceeds this. The amount of infrared radiation of the flame to be detected is determined by this predetermined reference level value.

Reference numeral 15 denotes an integrating circuit, which inputs the output C of the full-wave rectifier circuit 12 via a switch sw1 that is opened when the output of the connominator 13 is "H" and integrates it. 14 is an AND gate whose inputs are the output of the comparator S 13 and the output of the phase comparison circuit 10. 16 is an integrating circuit which inputs the output of the full-wave rectifier circuit 12 via a switch SW2 which is opened when the output of the AND gate 14 is "H" and integrates it. 18 is the output d of the integrating circuit 15 and the output e of the integrating circuit 16.
A comparator circuit that compares the two outputs outputs "H" if the output e is equal to or higher than a predetermined ratio of the output d. The circuit configuration is as shown in FIG. 5, where the input voltage d is divided by resistors R0 and R2 at a predetermined ratio, and the divided voltage and the input voltage e are compared by a comparator CP4. A comparison circuit 20 compares the output e of the integrating circuit 16 with a predetermined set value, and outputs "H" when the output e exceeds the predetermined set value v2. 22 is an AND gate that outputs "H" only when the output f of the comparison circuit 18 and the output f' of the comparison circuit 20 are both "H". 23
is a counter that counts the number of rising signals of the output of the converter ξ regulator 13, and outputs "H" when the number exceeds a predetermined number. 24 is an AND gate which outputs an alarm output when both the output f of the AND gate 22 and the output g of the counter 23 are "H". 26 is also an and gate,
As inputs, the output g of the counter 23 and the output of the AND gate 22 are inputted via an inverter 25. 27 is a timer, which is set by the rising signal when the output of the comparator 13 becomes 1H, and then becomes "H" after a predetermined period of time has elapsed.
Dolphin, comparator 13 configured to output
It may be configured to be set by the falling signal of , and then output H" after a predetermined time. 28 is an OR gate, and the output of the AND gate 26 or the timer 2
When the output of 7 becomes H'', the flip-flop 29 is reset. 29 is a flip-flop f for integrating circuit and counter control, which is set by the comparator 13 and reset by the output of the OR gate 28. Its output is output from the integrating circuit. 15, 16 and the counter 23, when the output is "H", the integrating circuit and the counter are operated, and when the output is "L", these circuits are reset.

Next, the operation of this embodiment will be explained.

Figures 4a and 4b show the output signals of the infrared sensor 2 and the visible light sensor 4 in the case of a continuously burning flame, interference light (B), and interference light and flame (C), respectively, using an amplifier 6.8. The output waveform C obtained by rectifying the output of the infrared sensor by the full-wave rectifier circuit 12 shows the case where the same waveform is output in each of the three cases mentioned above. .

The signal C after the full-wave rectification is compared with a predetermined reference level value v1 by a comparator 13, and the number of rising signals sent out when exceeding Vl is counted by a counter 23. At this time, a rising signal "H" is sent to the AND gate 24. The waveform is shown in FIG. 4g.

When only flame exists and there is almost no interfering light, the output a of the amplifier 6 changes according to the fluctuation of the flame, as shown in Figure 4, whereas the visible light component contained in the flame changes. is very small, so the output of the amplifier 8 is very small, as shown in FIG. 4 (8). Therefore, the output C' of the phase comparison circuit 10 remains at "H" as shown by C' in FIG. 4 (5).

The output of the amplifier 12 integrated by the integrating circuit 15 is
Among the full-wave rectifier outputs C shown in Figure 4, the ones corresponding to the areas filled in black are those corresponding to the areas filled in black.
The output of the amplifier 12 integrated by 6 also corresponds to the black area of the full-wave rectifier output C shown in FIG.

Therefore, the outputs d and e of both species dividing circuits 15 and 16 are almost the same as shown at 6% e in FIG. 4, so the output f of the comparator circuit 18 becomes °H''.

On the other hand, the case where only interference light exists will be explained with reference to FIG. 4 [F]). For example, when reflected sunlight directly enters the sensor 2.4 and fluctuates with a frequency component similar to that of a flame, the output a of the amplifier 6 will be at a wavelength of 43 μm included in the sunlight. Depending on the infrared light component, the waveform becomes similar to that in the presence of flame. On the other hand, the output of the amplifier 8 is
It has a waveform similar to a that corresponds to the visible light component contained in sunlight. Here, the amplitude ratio of both waveforms is the ratio between the visible light component of sunlight and the component with a wavelength of 43 μm, and changes depending on the weather and the characteristics of the reflecting object.

Therefore, the output C' of the phase comparison circuit 10 is as shown in FIG. 4(B).
, the waveform becomes as shown in C', and the switch SW2 is opened only when this output C' is "H", so the output a of the amplifier 6 integrated by the integrating circuit 16 is as shown in FIG. Of the waveform of the full-wave rectifier output C shown in B), only the area of the blacked out portion is included.

Therefore, since the output e of the integrating circuit 16 is significantly smaller than the output d of the integrating circuit 15, the output of the comparing circuit 18 remains at "L". Here, even when only interference light exists, the difference in the output a%b of both amplifiers 6.8 occurs due to subtle differences in the time constants of both sensors 2.4 and This is caused by a time lag in the incident interference light.

Next, referring to FIG. 4(C), we will explain the case where both flame and interference light exist.
Each output has an independent waveform. Therefore, the output C' of the phase comparison circuit 1° is shown in FIG. 4(C).
Since the output a of the amplifier 6 integrated by the integrating circuit 16 corresponds to the area filled in black at C in FIG. 4(C), this area is [
F]) is thicker than in the case of only the interference light.

Therefore, the output e of the integrating circuit 16 increases at a faster rate than in the case shown in FIG.
5, and the output of the comparison circuit 18 also becomes "H".

When the output e of the integrating circuit 16 exceeds the preset value V2 in the comparator circuit 20, the output f' of the comparator circuit 20 becomes "H".
” becomes.

The alarm output shown in FIG. 4 becomes "H" by the AND gates 22 and 24 when fl_f' and g are both "H". In other words, when the output g of the counter 23 becomes °H'' and the output f of the comparator circuit 18 and the output f' of the comparator circuit 20, which compare the integral values, are both "H", the alarm output is sent out. Ru.

Also, when the output g of the counter 23 becomes H",
If either the output f of the comparison circuit 18 or the output f' of the comparison circuit 20 is "L", the output of the AND gate 26 is "H".
'', and the flip-flop 29 passes through the or gate 28.
Reset. When the flip-flop 29 is reset, its output signal resets the integrating circuits 15, 16 and the counter 23, returning to the initial state.

In this way, when interference light is incident, the integrating circuits 15 and 16 and counter 23 are reset immediately after determining that it is interference light, so even if a fire occurs immediately after interference light enters, it will not be detected accurately. Can detect flames.

〔Effect of the invention〕

As explained above, the flame detector according to the present invention can eliminate the possibility of erroneously detecting infrared light with a wavelength of 43 μm included in strong interference light such as sunlight as a flame. In addition, when interference light is incident, the flame detection circuit section is set one time after the value that determines that it is interference light, so even if a fire breaks out immediately after interference light enters, It is possible to provide a highly reliable flame detector that can immediately detect a fire and issue an alarm without delay.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram showing one embodiment of the flame detector of the present invention. FIG. 2 is a diagram showing the spectral transmittance of an infrared pantonomy filter. Figure 3 is a diagram showing the vector distribution of phase flame and sunlight. 2: First light receiving element, 4: Second light receiving element, 13: Comparator, 15.16' integration circuit, 18, comparison circuit, 2
3: Counter, 27: Timer, 29: Control flip-flop

Claims (1)

[Claims] a first light receiving element that is sensitive to a wavelength range specific to flame; a second light receiving element that is sensitive to a specific wavelength range in the visible range; and a first light receiving element that integrates the output of the first light receiving element. an integrating means for comparing the phases of the output of the first light receiving element and the output of the second light receiving element; a second integrating means for integrating only the shifted portion; a comparing means for comparing the integral values of the first and second integrating means; and detecting flame fluctuation based on the output of the first light receiving element. a fluctuation detection section; a counter that counts the output of the fluctuation detection section; a control section that starts operation based on the output of the fluctuation detection section and controls the operations of the first and second integrating means and the counter; and the counter. A flame determining circuit that determines whether a flame exists or not according to a comparison result of an output and the phase comparison means, outputs an alarm when a flame exists, and resets the control unit when a flame does not exist. A flame detector comprising a detection means.