JPH0462326B2 - - Google Patents

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.

BACKGROUND ART Conventionally, it has been known that the spectral emissivity of a flame has a peak due to CO ₂ resonance radiation at a wavelength of 4.3μ, as shown by a in FIG. and,
When a flame is detected by detecting this wavelength of infrared rays,
It has good sensitivity to flames, and artificial light such as proof light has a small amount of components with a wavelength of 4.3μ, so there is no malfunction.
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 around 4.3μ.

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

Here, sunlight reaches the ground after subtracting what is absorbed in the atmosphere from the blackbody radiation energy of approximately 5700K. This spectrum is shown in Figure 8b.
It will be shown as However, a and b in Figure 8 are each normalized by the peak energy,
A direct comparison is not possible. As is clear from Fig. 8b, in the spectrum of sunlight, the intensity near the wavelength of 4.3μ is considerably smaller than the peak due to absorption of CO ₂ . Therefore, a device that detects 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 the infrared rays at a wavelength of around 4.3μ was developed in JP-A-49- It is known from Publication No. 128782. However, under intense summer sunlight, the radiation intensity may be comparable to that of a flame even at a wavelength of around 4.3μ.

Problems to be Solved by the Invention In the device described in JP-A-49-128782, the output signal of a first light-receiving element sensitive to visible light and the second light-receiving element sensitive to infrared rays are The system is configured to integrate a portion having a phase difference with the output signal of the controller, and to detect a fire when this integrated value reaches a predetermined value. However, if there is strong sunlight and it is detected with a slight phase shift from the visible light component, it will be detected as a flame even if only interference light is present. Although this can be prevented by setting a high judgment level for the integral value, this will deteriorate the accuracy of actual fire detection.

The present invention eliminates the drawbacks of such conventional examples,
To provide a flame detection period that can accurately detect only when a fire is actually occurring.

Means for Solving the Problems In order to achieve the above object, 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 of visible light. a second light receiving element having a second light receiving element, a first integrating means that integrates an output of the first light receiving element, and a phase comparison that compares 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 a portion of the output of the first light receiving element that is out of phase with the output of the second light receiving element;
and a determination time defining means for determining the time to determine whether or not a flame exists based on the integral value of the second integrating means, and when the determination time is determined by the determination time defining means, The present invention is characterized by comprising a determining means for determining that a flame has occurred when the integral value of the second integrating means is equal to or greater than a predetermined ratio of the integral value of the first integrating means.

The determination timing is determined by comparing the integral value of the first integrating means or the integral value of the second integrating means with a predetermined value, and when the integral value exceeds the predetermined value, it is determined whether there is a flame or not. Alternatively, the timing may be determined as the timing for determining whether the
The time when the frequency component is detected may be determined as the determination timing.

Effect According to the present invention, when only interference light such as sunlight exists and no flame exists, the output of the first light receiving element also exists, and it is slightly out of phase with the output of the second light receiving element. may deviate, and therefore the integral values of the first and second integrating means both increase, but
Since it is determined whether the light is a flame or not based on the ratio of both integral values, 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. Further, according to the present invention, when flame and interfering light coexist, the phase difference 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 is relatively large compared to the above value, and the occurrence of flame can be detected accurately.
Further, when only flame exists, since there is almost no output from the second light receiving element, both integrals have approximately the same value, and therefore it is clearly detected as a flame.

Embodiments Hereinafter, various embodiments of the present invention will be described in detail based on the drawings.

Fig. 1 is a block diagram showing a flame detector according to an embodiment of the present invention. In the same figure, 2 is an infrared sensor sensitive to infrared rays with a wavelength of around 4.3μ, and for example, the spectral transmittance as shown in Fig. 2 is It consists of a pyroelectric element such as a thermopile or a thermistor arranged to receive light transmitted through an infrared bandpass filter having specific characteristics. Reference numeral 4 denotes a visible light sensor sensitive to visible light, and both sensors 2 and 4 are arranged close to each other or at positions conjugate to each other with respect to the object to be detected.

Reference numerals 6 and 8 are amplifiers that amplify the output signals of sensors 2 and 4, respectively, and a part that adjusts the time constants of each sensor 2 and 4, and a 3 to 30 Hz part that amplifies the output signals of both sensors 2 and 4, which is unique to the flame. It consists of a part that selectively amplifies only the frequency components of. 10 is both amplifiers 6,
This is a phase discrimination circuit which receives both the outputs of 8 and discriminates the phase of both output waveforms, and is configured as shown in FIG. 3, for example. In Figure 3, CP ₁ is a comparator that outputs "H" when the output a of amplifier 6 is positive and "L" when it is negative, and CP ₂ is a comparator that outputs "L" when the output a of amplifier 6 is positive.
CP3 is a comparator that outputs "L" when the output b of the amplifier 8 is positive and "H" when it is negative or O. _CP3 outputs "H" when the output b of the amplifier 8 is positive or O, and "H" when it is negative. This is a comparator that outputs "L".
The outputs of the comparators CP ₁ and CP ₂ are input to the OR circuit OR via the AND circuit AN ₁ . On the other hand, the output of comparator CP ₁ is
It is input to the AND circuit AN ₂ via IV, and the output of the comparator CP ₃ is input to the AND circuit AN ₂ as is. The output of AND circuit AN ₂ is OR circuit
is input.

With this configuration, the output c of the phase discrimination circuit 10 (that is, the output c of the OR circuit OR) becomes "H" when the output b is smaller than the output when only the flame exists, and the output b becomes "H". The signal becomes "H" when the output a and the output b have opposite signs, although the signal is larger than when only the flame exists, and the signal becomes "L" in other cases. That is, comparators CP ₂ , CP ₃
The discrimination level is such that the output b when only a flame exists, as shown in the upper part, is slightly offset to the positive or negative side depending on the size.

Returning to FIG. 1, 12 is a full-wave rectifier circuit that also performs full-wave rectification of the output a of the amplifier 6, and is configured to perform full-wave rectification only on the output a that is higher than a predetermined level. This predetermined level determines the amount of flame infrared radiation to be detected. 14 is an integrating circuit that integrates the output of the full-wave rectifier circuit 12. The output of the full-wave rectifier circuit 12 is also input to the integration circuit 16 via a switch SW that is opened when the output c of the phase discrimination circuit 10 is "H", and is integrated. 18
is a comparison circuit that compares the output d of the integration circuit 14 and the output e of the integration circuit 16, and outputs "H" if the output e is equal to or higher than a predetermined ratio of the output d. 20 is
This is a comparison circuit that compares the output e of the integrating circuit 16 with a predetermined set value, and outputs "H" when the output e exceeds the set value. 22 is a control circuit that issues an alarm only when the outputs of both comparison circuits 18 and 20 are both "H". Furthermore, the control circuit 22 controls the comparison circuit 18 when the output of the comparison circuit 20 becomes "H".
If the output is "L", both integrating circuits 14 and 16 are reset. Here, the integrating circuits 14, 16
The integration operation is started simultaneously when the output a of the amplifier 6 exceeds a certain level, and if the integration result does not exceed a predetermined level even after a predetermined time has elapsed, both integration circuits 14 and 16 are automatically reset. It may be configured as follows.

Next, the operation of this embodiment will be explained. First, the changes in each output a, b, c, d, and e when only flame exists and almost no interfering light is present are shown in the fourth section.
This is shown in Figure A and the time chart. In this case, the output a of the amplifier 6 changes according to the fluctuation of the flame, as shown in a, whereas the visible light component contained in the flame is very small, so the output b of the amplifier 8 is
As shown, it is very small. Therefore, the output c of the phase discrimination circuit 10 is as shown in c.
It remains “H”. Therefore, since the switch SW remains open, the output of the amplifier 6 integrated by the integrating circuit 14 corresponds to the black area of the output a shown at 14 in FIG. 4A. On the other hand, the output of the amplifier 6 integrated by the integrating circuit 16 corresponds to the black area of the output a shown at 16 in FIG. 4A, and the area integral values are mutually be equal.

Therefore, the outputs d and e of both integrating circuits 14 and 16
are almost the same, as shown by d and e in FIG. 4A. Therefore, the output of the comparison circuit 18 becomes "H". When the output e of the integrating circuit 16 exceeds the preset value of the comparator circuit 20, the output of the comparator circuit 20 also becomes "H", and both inputs to the control circuit 22 become "H". The circuit 22 generates an alarm and the occurrence of a fire is detected.

On the other hand, each output a~ when only interference light exists
Figure 4B shows the change in e. For example, when reflected sunlight directly enters the sensors 2 and 4 and fluctuates with a frequency component similar to that of a flame,
The output a of the amplifier 6 has a waveform similar to that in the case where there is a flame, depending on the component of wavelength 4.3 μ included in the solar energy. On the other hand, the amplifier 8 and the output b have 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 4.3μ, and changes depending on the weather and the characteristics of the reflective object. Therefore, the output c of the phase discrimination circuit 10 becomes as shown by c in FIG. 4B, and since the switch SW is opened only when this output c is "H", The integrated output a of the amplifier 6 is shown in Fig. 4B.
Only the area of the blacked-out part of the waveform of the output a shown by 16 is shown in FIG.

Therefore, the output e of the integrating circuit 16 is the output e of the integrating circuit 1
This is significantly smaller than the output d of No. 4. Therefore, when the output of the comparison circuit 20 becomes "H", the output d is significantly larger than the output e, so the output of the comparison circuit 18 is "L", and the control circuit 22 does not issue an alarm. do not have. Here, even when only interference light exists, the output a of both amplifiers 6 and 8,
The difference in b is caused by a slight difference in the time constants of the two sensors 2 and 4, and a time difference between the interference light incident on the two sensors 2 and 4.

Next, FIG. 4C shows changes in each of the outputs a to e when both flame and interference light are present. In this case, the output a of the amplifier 6 and the output b of the amplifier 8 have independent waveforms. Therefore, the output c of the phase discrimination circuit 10 changes as shown by c in FIG. 4C, and therefore the output a of the amplifier 6 integrated by the integrating circuit 16 changes as Corresponding to the area filled in black, this area is the fourth
This is larger than the case of only interference light shown in Figure B. Therefore, the output e of the integrating circuit 16 is
This output e exceeds the set value of the comparator circuit 20 and the output becomes "H".
At the time when the output e is equal to or higher than the predetermined ratio of the output d, and the output of the comparison circuit 18 is also "H", the control circuit 22 issues an alarm.

As described above, according to this embodiment, flame can be detected accurately both when only flame exists and when flame and interference light coexist, and when only interference light exists, flame can be detected accurately. The accuracy is significantly better as it never makes false positives. However, in this example,
As is clear from looking at d and e in Figure 4A and Figure 4C, when there is a mixture of flame and interference light, e increases with respect to d compared to when there is only flame. Since it is slow, it takes time to detect it as a flame. FIG. 5 shows an embodiment that improves this drawback and defines the timing of flame detection using another method, and this embodiment will be described below.

FIG. 5 is a block diagram showing another embodiment of the present invention. Components that operate in the same manner as in FIG. 1 are given the same reference numerals, and a description thereof will be omitted.
In FIG. 5, a comparison circuit 1 compares the outputs d and e of the two integrating circuits 14 and 16 with each other and outputs "H" when the output e is equal to or higher than a predetermined ratio with respect to the output d.
8 is the same as in FIG. However, in this embodiment, instead of the comparison circuit 20 that compares the output e and a predetermined set value, the output d is compared with a predetermined set value, and when the output d exceeds the set value, the output becomes "H". A comparator circuit 24 is provided to output the . Then, the control circuit 26 detects flame and issues an alarm when the outputs of the comparison circuits 18 and 24 both become "H".

In this embodiment, when the output d of the integrating circuit 14 exceeds a predetermined set value, the output of the comparing circuit 24 becomes "H", and at this time, the output e of the integrating circuit 16 becomes a predetermined proportion of the output d. If it is above, comparison circuit 1
Since the output of 8 is also "H", the control circuit 26 issues an alarm. Therefore, according to the embodiment shown in FIG. 1, as is clear from FIGS. 4A and 4C,
Compared to the case of FIG. 4A, where only flame exists, in the case of FIG. According to this embodiment, it is determined whether or not flame is detected when the output d reaches a predetermined set value.
There is no delay in flame detection even in the presence of interfering light.

FIG. 6 is a block diagram showing yet another embodiment. In the figure, 28 is a timer circuit, and the integration circuits 14 and 16 are both reset every predetermined time _tsec set in the timer circuit 28. Therefore,
Both outputs d and e input to the comparator circuit 19 are reset every predetermined time t _sec . Comparison circuit 19 is d
The ratio between e and e is calculated, and if this ratio exceeds a predetermined value, it is detected as a fire and an alarm is issued. Also in this embodiment, detection is not delayed when flames and interfering light coexist compared to when only flames are present.

FIG. 7 is a block diagram showing yet another embodiment of the present invention. Components that operate in the same manner as in FIG. 1 are designated by the same reference numerals, and a description thereof will be omitted. In FIG. 7, 30 is the infrared sensor 2
This is a fluctuation detection circuit that detects fluctuations in the frequency (3 to 30Hz) that is unique to flames among the infrared light components incident on the flame. This fluctuation detection circuit 30
has the configuration proposed in, for example, Japanese Patent Application No. 59-107915, and outputs an "H" signal to the control circuit 32 when it detects fluctuations peculiar to a flame. The control circuit 32 causes the output of the comparison circuit 18 to also go to "H" when the output of the fluctuation detection circuit 30 goes to "H".
If so, issue an alert. In this example,
After detecting the fluctuation of the flame, the flame is detected by comparing the surface integral values, which enables more reliable flame detection.

Effects of the Invention As detailed above, the flame detector according to the present invention has a first flame detector that is sensitive to a wavelength range specific to flame.
a second light receiving element having sensitivity to a specific wavelength range of visible light; a first integrating means for integrating the output of the first light receiving element;
phase comparison means for comparing the phases of the output of the light receiving element and the output of the second light receiving element; a second integrating means for integrating; a determination time defining means for determining when to determine whether or not a flame exists based on the integral values of the first and second integrating means; Therefore, when the determination timing is specified, the apparatus further comprises determining means for determining that a flame has occurred when the integral value of the second integrating means is equal to or greater than a predetermined ratio of the integral value of the first integrating means. With this configuration, the possibility of false detection due to interfering light can be further reduced, and more accurate flame detection can be performed.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of a flame detector according to an embodiment of the present invention, Fig. 2 is a block diagram showing the spectral transmittance of its infrared bandpass filter, and Fig. 3 is a block diagram showing the configuration of its phase discrimination circuit. 4A, B, and C are time charts showing each output change, FIG. 5 is a block diagram showing another embodiment, FIG. 6 is a block diagram showing a modification thereof, and FIG. 8 is a block diagram showing yet another embodiment, and FIG. 8 is a graph showing spectra of flame and sunlight. 2; first light receiving element, 4; second light receiving element, 1
0; phase comparison means, 14; first integration means, 1
6; second integration means, 18, 19; comparison means, 2
0, 22, 24, 26, 28, 19, 30, 3
2; Detection means.

Claims (1)

[Claims] 1. A first device that is sensitive to a wavelength range specific to flame.
a second light receiving element having sensitivity to a specific wavelength range of visible light; a first integrating means for integrating the output of the first light receiving element; a phase comparing means that compares the phase of the output with the output of the second light receiving element; and a second comparing means that integrates only a portion of the output of the first light receiving element that is out of phase with the output of the second light receiving element. an integrating means for determining whether or not a flame exists based on the integral values of the first and second integrating means; and determining a determination time by the determination time determining means. and determining means for determining that a flame has occurred when the integral value of the second integrating means is greater than or equal to a predetermined ratio of the integral value of the first integrating means when Detector. 2. The determination timing determining means includes means for comparing the integral value of the first integrating means with a predetermined value, and as a result of the comparison by the comparing means, the integral value of the first integrating means exceeds the predetermined value. 2. The flame detector according to claim 1, wherein the time is defined as the time for determining whether or not a flame exists. 3. The determination timing determining means includes means for comparing the integral value of the second integrating means with a predetermined value, and as a result of the comparison by the comparing means, the integral value of the second integrating means exceeds the predetermined value. 2. The flame detector according to claim 1, wherein the time is defined as the time for determining whether or not a flame exists. 4. The determination timing determining means includes means for detecting a frequency component peculiar to a flame in the output of the first light receiving element, and determines when the frequency component peculiar to a flame is detected by the detecting means. 2. The flame detector according to claim 1, wherein the timing is defined as the timing for determining whether or not the flame detector exists.