JP2021144737A - Flame detection device - Google Patents

Abstract

To make it possible to surely determine presence/absence of a combustion flame based on simultaneity of temporal changes in light receiving outputs by a plurality of light receiving units relative to a plurality of wavelength bands of radiation energy radiated from the combustion flame.SOLUTION: A plurality of light receiving units 12a, 12b are provided, and the light receiving units 12a, 12b output light receiving signals E1, E2 obtained by observing different wavelength bands among radiation energy. A determination unit 15 sets a mutual correlation of signal amplitudes of the respective light receiving signals for a predetermined period of time observed and output at substantially the same time by the light receiving units 12a, 12b as one element for judging whether or not combustion flame is present, and determines that the flame is present when the correlation is high, and determine that no flame is present when the correlation is low.SELECTED DRAWING: Figure 1

Description

The present invention relates to a flame detection device that detects the emission of light accompanying flame combustion and determines the presence or absence of a flame.

Conventionally, in a flame detection device that detects the presence or absence of a flame by detecting the radiation energy generated by flame combustion, it is generated at the time of flame combustion in order to distinguish between the flame and an infrared radiator other than the flame. A flame of a two-wave type, a three-wave type, etc. that detects the radiation intensity in a plurality of wavelength bands including the wavelength band due to the resonance radiation of _{CO 2 and detects the presence or absence of a flame by the relative ratio of the detected values in the multiple wavelength bands.} Detection devices and flame detection methods are well known.

Here, the two-wavelength type and three-wavelength type flame detection devices in the prior art will be briefly described.

FIG. 14 is a conceptual diagram showing radiation spectra of a combustion flame and other typical radiators in the infrared wavelength region. The horizontal axis shows the wavelength of radiation, and the vertical axis shows the relative intensity of radiation.

As shown in FIG. 14, in the spectral characteristic 100 of the combustion flame, there is a peak of radiation relative intensity in the wavelength band near 4.5 μm due to the resonance radiation of _{CO 2, and it is characteristic that it exists in the vicinity of this peak wavelength.} As a wavelength, for example, a wavelength band having a low relative radiation intensity exists in the vicinity of 5.1 μm on the long wavelength side.

Theoretically, it is known that there is a peak of radiation intensity due to resonance radiation of _{CO 2 in} the 4.3 μm band. However, it has been empirically shown that when a combustion flame is actually observed, a peak of radiant intensity appears in the vicinity of 4.4 to 4.5 μm. Therefore, in the following, unless otherwise specified, the CO ₂ resonance radiation band refers to the 4.4 to 4.5 μm band.

Then, in the case of the two-wavelength type flame detection device, for example, the radiation energies in the wavelength band near 4.4 to 4.5 μm and the wavelength band near 5.1 μm are obtained by a narrow-band optical wavelength band path filter. Selective transmission (passage) is performed, the radiation energy is detected by a light receiving sensor, this is photoelectrically converted, and then subjected to predetermined processing such as amplification to obtain an electric signal corresponding to the amount of energy (hereinafter referred to as "light receiving signal"). , The presence or absence of a flame is determined by taking a relative ratio of the received signal levels in each of the above wavelength bands and comparing them with a predetermined threshold value.

As a result, infrared radiators other than flames, for example, high-temperature radiators such as sunlight (6000 ° C) shown in spectral characteristics 102, relatively low-temperature radiators of about 300 ° C shown in spectral characteristics 104, and spectral characteristics. It is possible to distinguish between a low-temperature radiator such as the human body shown in 106 and a flame.

Further, for example, in addition to the above-mentioned two wavelengths, the radiation energy in the short wavelength side of the 4.4 to 4.5 μm band, which is the resonance radiation band of _{CO 2, for example, in the wavelength band near 3.8 μm is divided into two wavelengths.} A three-wavelength flame detector that detects the presence or absence of a flame based on the relative ratio of each received signal in these three wavelength bands is also known, and distinguishes between a flame and an infrared radiator other than the flame. The performance is further improved.

When such a flame detection device is installed in a tunnel to monitor vehicle flames in a road tunnel, the flame detection device has detection areas in both the left and right directions and is arranged adjacent to each other along the longitudinal direction of the tunnel. For example, they are continuously arranged at intervals of 25 m or 50 m so that the detection areas of the flame detection device and the flame detection device overlap each other in a complementary manner. Further, as the light receiving element, for example, a pyroelectric body is used.

Special Publication No. 55-33119 Special Publication No. 59-34252 Japanese Patent No. 3357330 Japanese Unexamined Patent Publication No. 3-78899 Japanese Unexamined Patent Publication No. 2001-356047 JP-A-2010-249769 Japanese Unexamined Patent Publication No. 2003-217047 Japanese Unexamined Patent Publication No. 2001-249047

By the way, in the conventional flame detection device, each light reception by the radiation energy in the wavelength band of about 4.5 μm due to the resonance radiation _{of CO 2 from the combustion flame and the wavelength band of, for example, about 5.1 μm which does not include this wavelength band.} The presence or absence of flame is determined by taking a relative ratio of signal levels and comparing it with a predetermined threshold, but depending on the setting of the threshold, it is assumed that the presence or absence of flame cannot be accurately determined, and the presence or absence of flame is determined. In order to determine the presence or absence more accurately, it is desirable to determine the presence or absence of flame by incorporating factors other than the relative ratio of the received signal levels in different wavelength bands.

The present invention provides a flame detection device that can reliably determine the presence or absence of a combustion flame based on the simultaneity of temporal changes in the light receiving output by a plurality of light receiving units for a plurality of wavelength bands of radiation energy radiated from the combustion flame. The purpose is to provide.

Here, the light receiving unit is a light receiving sensor including an optical wavelength filter and a photoelectric conversion unit including a light receiving element, and a light receiving signal that is processed by appropriately amplifying, for example, the photoelectric conversion signal from the light receiving sensor as necessary. It shall refer to a signal detection circuit unit including an electric circuit that outputs as.

(Flame detector)
The present invention is a flame detection device.
A plurality of light receiving units that output light receiving signals that observe radiation energy in different predetermined wavelength bands in the monitoring area, and
The cross-correlation between the light-receiving signals of each signal amplitude obtained from each light-receiving signal for a predetermined period of time observed and output by each light-receiving unit at approximately the same time is used as the first element for determining the presence or absence of combustion flame. Judgment department and
With
As the first element, the determination unit divides each received signal for the predetermined period into a plurality of divided sections corresponding to a plurality of time sections, and among the plurality of divided sections within the predetermined period. The presence or absence of a combustion flame is determined based on the ratio of the integrated value of the signal amplitude for the reference divided section to the mutual ratio between the received signals to the integrated value of the signal amplitude for the other divided sections. It is characterized by that.

As the second element of determining the presence or absence of the combustion flame, the determination unit determines the presence or absence of the combustion flame based on the level of at least one received light signal of each light receiving signal for a predetermined period, and determines the presence or absence of the combustion flame as the judgment result of the first element. The flame is detected based on the judgment result of the second factor.

As a second element, the determination unit determines the presence or absence of a combustion flame based on the presence or absence of a combustion flame when the signal amplitude of at least one received signal is equal to or greater than a predetermined threshold value.

(Basic effect)
The present invention is a flame detection device that observes the radiation energy radiated from a combustion flame to determine and detect the presence or absence of a combustion flame, and receives received signals radiated from the combustion flame by observing different predetermined wavelength bands. It is provided with a plurality of light receiving units to be output and a judgment unit in which mutual correlation of each light receiving signal for a predetermined period observed and output by each light receiving unit at substantially the same time is one element of determining the presence or absence of a combustion flame. Therefore, if the correlation is high, the temporal changes in the radiation energy emitted from the combustion flame are almost the same, so the light input to the light receiving unit may be due to the radiation from the flame. By making it one element of determining the presence or absence of flame, the presence or absence of combustion flame can be more reliably determined and detected.

(Effect of light receiving unit)
Further, the light receiving unit 1 receives _{an optical wavelength filter that selectively transmits light in a predetermined frequency band including a CO 2} resonance radiation band emitted from a combustion flame and a light receiving element that receives light transmitted through the optical wavelength filter. A light receiving sensor having one or a plurality of light receiving elements that output a light receiving signal based on a photoelectrically converted electric signal is provided, and the other light receiving unit is a predetermined frequency band that is emitted from a combustion flame and does not include _{a CO 2 resonance radiation band.} It is provided with a light receiving sensor having an optical wavelength filter that selectively transmits the light of Further, each of the light receiving units further includes a frequency selection unit that selectively extracts a signal component in a predetermined frequency band from the electric signal from the light receiving sensor, and an amplification unit that amplifies the signal component output from the frequency selection unit. Then, each of the photoelectric units reliably photoelectrically convert the radiation energy of the band wavelength having a central frequency of about 4.5 μm and the radiation energy of the band wavelength different from this emitted from the combustion flame and output the received signal. It is possible to do.

Further, by providing a plurality of light receiving elements in the light receiving sensor, for example, it is possible to suppress and align the variation due to the difference in the light receiving characteristics of the plurality of light receiving elements by adding the light receiving outputs obtained by photoelectric conversion by the plurality of light receiving elements. And.

(Two light receiving units)
In addition, by providing at least two light receiving units, the judgment unit can correlate the light receiving signals for a predetermined period in different wavelength bands observed and output by the two light receiving units at substantially the same time. It is possible to make it another element of flame judgment.

(Effect of flame judgment by correlation of signal amplitude)
In addition, the judgment unit divides the cross-correlation of each received light signal into a plurality of time sections for each received light signal for a predetermined period, and all the ratios of the signal integral values between the divided sections are within the predetermined flame judgment threshold range. If it is inside, it is possible that the light input to the light receiving unit may be due to radiation from the flame, and by using it as one element of determining the presence of flame, it is possible to more reliably determine and detect the presence of combustion flame. do.

(Effect of detailed flame judgment by correlation of signal amplitude)
Further, when the determination unit divides each light receiving signal E1 to Em for a predetermined period output from a plurality of light receiving units into time intervals of 1 or more integers n, 1 light receiving 1 is received for each of these n divided sections. The ratio R1 to Rn of the signal integral values ΣE11 to ΣE1n of the signal E1 and the integral values ΣEm1 to ΣEmn of other received light signals Em corresponding to the same time interval are set.
R1 to Rn = ΣE11 / ΣEm1 to ΣE1n / ΣEmn
When all of the ratios R2 to Rn of the signal integrated values in the remaining time interval to the ratio R1 of the signal integrated values in the first time interval are within the predetermined flame determination threshold range, they are input to the light receiving unit. Since there is a possibility that the light is emitted from the flame and it is one of the factors for determining the presence of flame, the correlation is based on the correlation that the amplitude changes of the two received signals E1 and E2 in the first time interval are almost the same. It is possible to compare the deviation of the correlation in the remaining time interval, and if the deviation of the correlation is small, determine and detect the presence or absence of the combustion flame.

(Effect of flame judgment by correlation of frequency distribution)
In addition, the determination unit obtains the relative level distribution of the frequencies in a predetermined range obtained by dividing each received signal for a predetermined period into a plurality of time sections for the correlation between the received signals, and the frequency relative level distribution between the divided sections. When all the ratios of the integral values of are within the predetermined flame judgment threshold range, it is considered that the light input to the light receiving unit may be due to the radiation from the flame, and it is considered as one element of the judgment of the presence of the flame. It is possible to more reliably determine and detect the presence or absence of.

Block diagram showing an embodiment of a flame detection device Explanatory drawing which showed the schematic structure of the light receiving unit applied to the flame detection apparatus of FIG. A circuit diagram showing an equivalent circuit of the light receiving sensor shown in FIG. Characteristic diagram showing the radiation spectrum of the combustion flame A characteristic diagram showing the transmittance of the optical wavelength filter and the translucent window applied to the embodiment of FIG. 1 at each wavelength. Signal waveform diagram showing the light-receiving signals output from each of the light-receiving units in FIG. 1 when the radiation energy radiated from the combustion flame is observed. A flowchart showing the procedure of the processing operation of the determination unit of FIG. 1 for determining the correlation between the amplitude changes of the two received signals. Explanatory drawing showing the frequency distribution of the light receiving signal output from each of the light receiving units of FIG. 1 when the radiation energy radiated from the combustion flame is observed. A flowchart showing the procedure of the processing operation of the determination unit of FIG. 1 for determining the correlation of the frequency distributions of the two received signals. A block diagram showing an embodiment of a flame detection device that adds light-receiving signals from a plurality of light-receiving elements provided in a light-receiving unit. A circuit diagram showing an equivalent circuit of the light receiving sensor of FIG. Block diagram showing other embodiments of a flame detector installed in a tunnel to monitor a fire A characteristic diagram showing the transmittance of the optical wavelength filter and the translucent window applied to the embodiment of FIG. 12 at each wavelength. Characteristic diagram showing radiation spectra of combustion flames and other typical radiators

[Overview of flame detector]
FIG. 1 is a block diagram showing an embodiment of a flame detection device according to the present invention by a functional configuration, FIG. 2 is an explanatory view showing a schematic configuration of a light receiving unit applied to the flame detection device of FIG. 1, and FIG. 3 is a diagram. A circuit diagram showing an equivalent circuit of the light receiving sensor of No. 2, FIG. 4 is a characteristic diagram showing a radiation spectrum of a combustion flame, and FIG. 5 is a wavelength of each wavelength of the optical wavelength filter and the translucent window applied to the embodiment of FIG. It is a characteristic diagram which showed the transmittance in.

As shown in FIG. 1, the flame detection device 10 of the present embodiment observes the radiation energy having the spectral characteristic 50 shown in FIG. 4 emitted from the combustion flame existing in the monitoring region, and is roughly classified into combustion. The light receiving unit 12a that observes the radiation energy in the narrow band wavelength band centered at approximately 4.5 μm emitted from the flame by CO _{2 resonance and outputs the light receiving signal E1 by photoelectric conversion, and the CO 2} resonance from the combustion flame. A light receiving unit 12b that observes radiation energy in a narrow band wavelength band having a central wavelength of, for example, approximately 2.3 μm and outputs a light receiving signal E2 by photoelectric conversion, and a light receiving unit 12a, which does not include approximately 4.5 μm emitted by the light receiving unit 12a. It is provided with a determination unit 15 in which the mutual correlation of the received light signals E1 and E2 for a predetermined period observed and output at substantially the same time in 12b is one element of determining the presence or absence of a combustion flame.

(Light receiving unit configuration)
The light receiving unit 12a is a light receiving sensor 16a and a light receiving sensor 16a that convert radiation energy having a narrow band wavelength band having a central frequency of about 4.5 μm, which is emitted _{from a combustion flame by CO 2 resonance, into an electric signal and output it.} The preamplifier 24a that passes only the signal component of a predetermined frequency band from the received signal output from the preamplifier 26a, the preamplifier 26a that first-stage amplifies the signal component that has passed through the preamplifier 24a, and the output from the preamplifier 26a will be described later. It is composed of a main amplifier 28a that amplifies the signal level suitable for the flame determination process and outputs the received signal E1.

Further, the light receiving unit 12b is obtained from a light receiving sensor 16b and a light receiving sensor 16b that convert radiation energy emitted from a combustion flame and having a narrow band frequency band having a central frequency of about 2.3 μm into an electric signal and output the signal. The preamplifier 24b that passes only the signal component of a predetermined frequency band from the output received signal, the preamplifier 26b that first-stage amplifies the signal component that has passed through the preamplifier 24b, and the output from the preamplifier 26b will be described later. It is composed of a main amplifier 28b that amplifies to a signal level suitable for flame determination processing and outputs a received signal E2.

Here, the light receiving sensors 16a and 16b include a translucent window 18 shared by using an infrared translucent member such as sapphire glass, optical wavelength filters 20a and 20a, and pyroelectric light receiving elements 22a and 22b. ing.

The light-receiving signals E1 and E2 output from the light-receiving units 12a and 12b via the amplifiers 28a and 28b are converted into digital light-receiving signals by the A / D conversion ports 30a and 30b provided in the determination unit 15 and read. The flame judgment described later is executed. Hereinafter, each configuration will be specifically described.

(Light receiving sensors 16a, 16b)
The light receiving sensor 16a provided in the light receiving unit 12a includes an optical wavelength filter 20a, a light receiving element 22a, and a shared translucent window 18. As shown in FIG. 5, the optical wavelength filter 20a has a transmission characteristic 54 that transmits only light in a predetermined band including a wavelength band of approximately 4.5 μm emitted by _{CO 2 resonance generated during flame combustion with high transmittance.} It is an optical bandpass filter having, for example, selectively transmits light in a predetermined band containing 4.5 μm and not including other wavelength bands described later. The light receiving element 22a has a photoelectric conversion function by a pyroelectric body and an FET, receives light transmitted through the optical wavelength filter 20a, converts it into an electric signal, and outputs the light.

Specifically, as shown in FIG. 2, the light receiving sensor 16a includes a light receiving element 22a having a plurality of pyroelectric bodies 25a arranged on the front surface of the substrate 36a and an FET 27a arranged on the back surface of the substrate 36a, and a substrate. A substrate mounting portion 40a for supporting the 36a on the base portion 38a, a base portion 38a provided with terminals 42a extending from the back side on the substrate mounting portion 40a side, and a narrow band bandpass filter in front of the light receiving element 22a. It has a packaged configuration including a cover member 44a provided with an optical wavelength filter 20a.

Further, as shown in FIG. 3, the equivalent circuit of the light receiving element 22a is connected to the gate terminal G from the gate of the FET 27a via, for example, a parallel circuit of the pyroelectric body 25 and the high resistance 29, and also connects the drain and the source of the FET 27. They are connected to the drain terminal D and the source terminal S, respectively.

On the other hand, the light receiving sensor 16b includes an optical wavelength filter 20b, a light receiving element 22b, and a shared translucent window 18. As shown in FIG. 5, the optical wavelength filter 20b is an optical band path having a transmission characteristic 58 that transmits only light in a predetermined band including a wavelength band of approximately 2.3 μm emitted from a combustion flame with a high transmittance. A filter that selectively transmits light in a predetermined band, for example, containing 2.3 μm and not including a wavelength band of approximately 4.5 μm emitted by _{CO 2 resonance.} The light receiving element 22b has a photoelectric conversion function by a pyroelectric body and an FET, receives light transmitted through the optical wavelength filter 20b, converts it into an electric signal, and outputs the light.

Specifically, as shown in FIG. 2, the light receiving sensor 16b includes a light receiving element 22b having a plurality of pyroelectric bodies 25b arranged on the front surface of the substrate 36b and an FET 27b arranged on the back surface of the substrate 36b, and a substrate. A substrate mounting portion 40b for supporting the 36b on the base portion 38b, a base portion 38b provided with terminals 42b extending from the back side on the substrate mounting portion 40b side, and a narrow band bandpass filter in front of the light receiving element 22b. It has a packaged configuration including a cover member 44b provided with an optical wavelength filter 20b. The equivalent circuit of the light receiving element 22b is the same as that of the light receiving element 22a shown in FIG.

Further, the light receiving sensors 16a and 16b are arranged in a predetermined arrangement in close proximity to each other on a common mounting member 48 provided in the main body cover 46.

Here, the optical wavelength filters 20a and 20b can be formed, for example, on a substrate such as silicon, germanium, or sapphire by a known method.

(Translucent window 18)
The translucent window 18 is located on the upper surface side corresponding to the monitoring area side of the main body cover 46 in which the light receiving sensors 16a and 16b are housed, and is arranged in a predetermined opening provided on the front side of the light receiving sensors 16a and 16b. For example, it is formed of an infrared translucent member such as sapphire glass. Therefore, the light receiving elements 22a and 22b are set with detection areas having substantially the same spreading angle by restricting the light receiving limit field of view at the edge portion of the translucent window 18.

Here, as shown in FIG. 5, the sapphire glass constituting the translucent window 48 has a short wave path characteristic 52 that satisfactorily transmits radiation in a wavelength band of approximately 7.0 μm or less, in other words, approximately 7. It functions as a filter member having a long wave cut characteristic that blocks radiation with a long wavelength from around 0.0 μm. Further, in the present embodiment, the translucent window 18 will be described as being included in the light receiving sensors 16a and 16b as a common member.

(Light receiving sensors 16a, 16 This wavelength transmission characteristic)
FIG. 5 is a characteristic diagram showing the transmittance of the optical wavelength filter and the translucent window applied to the embodiment of FIG. 1 at each wavelength.

The sapphire glass, which is the translucent window 18 of FIG. 1, has a short wave path characteristic 52 that allows radiation of about 7.0 μm or less to be transmitted well, and a center wavelength of about 4.5 μm that constitutes the optical wavelength filter 20a. In combination with the transmittance characteristic 54 of the bandpass filter, which transmits the radiation energy in the wavelength band near the center wavelength with high transmittance, the radiation energy in the wavelength band of approximately 4.5 μm is transmitted with high transmittance. A narrowband band path filter having a transmission characteristic 56 is configured.

Further, the sapphire glass which is the translucent window 18 has a short wave path characteristic 52 which allows radiation of about 7.0 μm or less to be transmitted well, and a center wavelength of about 2.3 μm which constitutes the optical wavelength filter 20a. In combination with the transmittance characteristic 58 of the bandpass filter that transmits the radiation energy in the wavelength band near the center wavelength with high transmittance, the transmission that transmits the radiation energy in the wavelength band of approximately 2.3 μm with high transmittance. A narrowband band path filter having the characteristic 60 is configured.

(Prefix filters 24a, 24b)
The preamplifier filters 24a and 24b function as frequency selection units, and from the light receiving signals output from the light receiving elements 22a and 22b of the light receiving sensors 16a and 16b, only the signal components of the specific frequency band used for the flame determination process are used. For example, it is an active filter, and outputs a light receiving signal including a signal component of a specific frequency band to the preamplifiers 26a and 26b in the subsequent stage.

(Preamplifiers 26a and 26b and main amplifiers 28a and 28b)
The preamplifiers 26a and 26b first-stage amplify the received light signals input via the preamplifiers 24a and 24b at a predetermined amplification factor, and the main amplifiers 28a and 28b describe the received light signals from the preamplifiers 26a and 26b as described later. It is amplified to a signal level suitable for flame judgment processing and output as received light signals E1 and E2.

(A / D conversion ports 30a, 30b)
The A / D conversion ports 30a and 30b are A / D converters provided as input ports of the judgment unit 15, and convert the light receiving signals (analog light receiving signals) E1 and E2 into digital signals suitable for digital processing of the judgment unit 15. And read.

(Judgment unit 15)
The determination unit 15 is composed of a CPU, a memory, a microprocessor unit (MPU) or the like having various input / output ports including A / D conversion ports 30a and 30b as hardware. Further, the determination unit 15 realizes a flame determination control function by executing a program by the CPU.

The determination unit 15 controls that the mutual correlation of the light receiving signals E1 and E2 for a predetermined period observed and output by the light receiving units 12a and 12b at substantially the same time is one element of determining the presence or absence of the combustion flame.

That is, the determination unit 15 obtains the mutual correlation of the light receiving signals E1 and E2 for a predetermined period observed and output by the light receiving units 12a and 12b at substantially the same time, and when the mutual correlation satisfies the predetermined standard. It is assumed that the light input to the light receiving units 12a and 12b may be due to radiation from the flame, and control is performed to determine and detect the presence or absence of the flame as one element of the presence of the flame.

(Flame judgment by mutual correlation of received signals E1 and E2)
The details of the flame determination performed by obtaining the cross-correlation of the light-receiving signals E1 and E2 for a predetermined period observed and output by the light-receiving units 12a and 12b by the judgment unit 15 at substantially the same time will be as follows.

FIG. 6 shows a light receiving signal E1 due to radiation energy in a narrow band wavelength band having 4.5 μm as a central wavelength output from the light receiving unit 12a of FIG. 1 when observing the radiation energy radiated from the combustion flame, and the light receiving unit 12b. The light receiving signal E2 due to the radiation energy in the narrow band wavelength band having 2.3 μm as the central wavelength is shown, and the light receiving signal E2 has a similar waveform with a low level with respect to the light receiving signal E1.

Further, the signal waveforms of the received signals E1 and E2 shown in FIG. 6 are converted into digital received signals by sampling the received light signals E1 and E2 at, for example, 64 Hz at the A / D conversion ports 30a and 30b provided in the determination unit 15. The state in which the received light signals E1 and E2 for a predetermined period T = 2 seconds are temporarily stored in the buffer memory as the target of one correlation calculation is shown as an analog waveform.

The determination unit 15 divides the predetermined period T = 2 seconds into four time intervals T1, T2, T3, and T4 of, for example, 500 milliseconds, and plus and minus from the reference potential which is the midpoint of the received light signals E1 and E2. As the integrated value that is the absolute value of the difference from the amplitude on the side, the integrated values ΣE11, ΣE12, ΣE13, and ΣE14 of each time interval T1 to T4 are obtained for the received light signal E1, and each time interval T1 is obtained for the received signal E2. Obtain the integral values ΣE21, ΣE22, ΣE23, and ΣE24 of ~ T4.

Next, the determination unit 15 determines the ratio R1 and R2 of the signal integral values ΣE11, ΣE12, ΣE13, ΣE14 of the received signal E1 and the integrated values ΣE21 ΣE22, ΣE23, ΣE24 of the received signal E2 for each of the same time intervals T1 to T4. , R3, R4,
R1 = ΣE11 / ΣE21 equation (1)
R2 = ΣE12 / ΣE22 equation (2)
R3 = ΣE13 / ΣE23 equation (3)
R4 = ΣE14 / ΣE24 equation (4)
This is used as the cross-correlation of the received light signals E1 and E2.

In order to determine the mutual correlation between the received light signals E1 and E2, the determination unit 15 sets a flame determination threshold range having a lower limit threshold value TH1 and an upper limit threshold value TH2 based on the ratio R1 of the integrated values of the first time interval T1.

The determination unit 15 sets the lower limit threshold value TH1 and the upper limit threshold value TH2 to, for example, ± 10% of the upper and lower threshold values TH1 and TH2 with respect to the ratio R1 of the first time interval T1, TH1 = 0.9 · R1, TH2 = 1. .1 ・ Set the flame judgment threshold range as R1. Expressing this generally, the lower limit threshold TH1 (= α · R1) is set by multiplying the ratio R1 of the signal integral values of the first interval T1 by a predetermined constant α less than 1, and a predetermined value exceeding 1 is set. It means that the upper limit threshold value TH2 (= β · R1) is set by multiplying the constant β, and the values of the coefficients α and β can be set as appropriate as needed.

When the flame determination threshold range having the lower limit threshold value TH1 and the upper limit threshold value TH2 is set in this way, the determination unit 15 determines whether or not the following conditions are satisfied.
0.9R1 ≤ R2 ≤ 1.1 R1 equation (5)
0.9R1 ≤ R3 ≤ 1.1 R1 equation (6)
0.9R1 ≤ R4 ≤ 1.1 R1 equation (7)

When the determination unit 15 determines that all the conditions of the above equations (5) to (7) are satisfied, that is, the ratio R1 of the signal integration value of the first time interval T1 is equal to that of the remaining time intervals T2 to T4. When the ratios R2 to R4 of all the signal integration values are within the predetermined flame judgment threshold range, the amplitude waveforms of the light receiving signals E1 and E2 are substantially similar, and the light receiving units 12a and 12b both receive the radiation energy from the combustion flame, respectively. because it can estimated to be observed at different wavelength bands, in this case, the one element of the determination there flames, 4.5 [mu] m of narrow wavelength band centered wavelength emitted by CO ₂ resonance, for example, from the combustion flame Allows flame judgment based on the received signal E1 with a sufficient amplitude level due to radiation energy.

In this case, as a flame determination based on the received light signal E1, the determination unit 15 obtains a frequency distribution from the received light signal E1 by a calculation method such as a fast Fourier transform (FFT), and includes a fluctuation frequency peculiar to the flame, for example, a frequency distribution of 8 Hz or less. If the integrated value is equal to or greater than a predetermined threshold value, it is determined that there is a possibility of flame, and further, a process of determining that it is a flame is performed in consideration of other elements of flame determination.

Further, when the determination unit 15 determines that at least one of the conditions of the above equations (5) to (7) is not satisfied, that is, the remaining time interval with respect to the ratio R1 of the signal integral value of the first time interval T1. When at least one of the ratios R2 to R4 of the signal integral values of T2 to T4 deviates from the predetermined flame judgment threshold range, it can be estimated that the received signals E1 and E2 are due to the radiation energy from other than the combustion flame. It is not an element and suppresses flame judgment based on the received signal E1.

(Generalized cross-correlation judgment)
Here, when the number of sections i for dividing the predetermined period T is generalized to i = 1 to n and the received signal is generalized to E1 to Em, the determination unit 15 divides the predetermined period T into the sections T1 to Tn. Then, the integrated values ΣE11 to ΣE1n of each time interval T1 to Tn are obtained for the received light signal E1 as a value (integral amplitude value) obtained by integrating the absolute value of the difference with respect to the reference potential which is the midpoint of the received light signals E1 and Em. Further, for the received signal Em, the integrated values ΣEm1 to ΣEmn of each time interval T1 to Tn are obtained, and the ratio R1 to Rn of the two is further determined.
R1 to Rn = ΣE11 / ΣEm1 to ΣE1n / ΣEmn
This is used as the cross-correlation of the received light signals E1 and Em.

Next, when the lower limit threshold value TH1 and the upper limit threshold value TH2 are set in the same manner as described above, the determination unit 15 determines whether or not the condition within the next flame determination threshold range is satisfied.
0.9R1 ≤ R2 ≤ 1.1R1 to 0.9R1 ≤ Rn ≤ 1.1R1
When it is determined that the condition within the flame determination threshold range is satisfied, the amplitude waveforms of the light receiving signals E1 and E2 are generally similar, and it can be estimated that the light receiving units 12a and 12b are observing the radiation energy from the combustion flame. , As one element of the judgment of the presence of flame, the flame judgment based on the received light signal E1 is allowed.

On the other hand, when the determination unit 15 determines that at least one of the conditions outside the flame determination threshold range is not satisfied, it can be estimated that the light receiving signals E1 and E2 are due to the radiation energy from other than the combustion flame. It is not an element and suppresses flame judgment based on the received signal E1.

(Flame judgment processing operation)
FIG. 7 is a flowchart showing a procedure of the processing operation of the determination unit of FIG. 1 for determining the correlation between the amplitude changes of the two received signals.

(Step S1)
First, the determination unit 15 captures the light receiving signals E1 and E2 output from the light receiving units 12a and 12b via the A / D conversion ports 30a and 30b at a predetermined sampling cycle for a predetermined time T, for example, T = 2 seconds. Temporarily store in buffer memory.

(Step S2)
Next, the determination unit 15 divides the light receiving signals E1 and E2 of the predetermined period T captured in step S1 into four time sections T1, T2, T3, and T4, and the signal amplitude of the light receiving signals E1 in each of the divided sections T1 to T4. The integrated values ΣE11, ΣE12, ΣE13, ΣE14 and the integrated values ΣE21, ΣE22, ΣE23, ΣE24 of the received signal E2 are calculated.

It is desirable that the processes after step S2 be executed when the signal level of the light receiving signal E1 taken in from the A / D conversion port 30a by the determination unit 15 becomes equal to or higher than a predetermined threshold value.

(Step S3)
Next, the determination unit 15 calculates the ratio R1, R2, R3, R4 of the integrated values of the divided sections T1 to T4 of the received light signals E1 and E2 calculated in step S2 by the above equations (1) to (4).

(Step S4)
Next, the determination unit 15 sets the lower limit threshold value TH1 and the upper limit threshold value TH2 to, for example, TH1 = 0.9 · R1 and TH2 = 1.1 · R1 based on the ratio R1 of the integrated values of the first time interval T1. Set the threshold range.

(Step S5)
Next, in the determination unit 15, the ratios R2, R3, and R4 of the integrated values of the remaining time intervals T2 to T4 following the first time interval T1 of the received light signals E1 and E2 calculated in step S3 are the above equations (5) to (5). According to 7), it is determined whether or not it is within the flame determination threshold range having the lower limit threshold value TH1 and the upper limit threshold value TH2.

(Steps S6 and S7)
Next, the determination unit 15 satisfies all the conditions of the above equations (5) to (7) in step S6, so that the ratio R2, R3, and R4 of the integrated values of the time intervals T2 to T4 are all within the flame determination threshold range. When it is determined that the signal is inside, it is estimated that the amplitude waveforms of the received light signals E1 and E2 are substantially similar to each other and the received signal is due to the radiation energy from the combustion flame, and it is determined to be one element of the flame judgment. To allow the flame judgment based on the received light signal E1.

(Steps S6 and S8)
On the other hand, when the determination unit 15 determines in step S6 that at least one of the conditions of the above equations (5) to (7) is not satisfied, that is, TH1 = 0.9 · R1 and TH2 = 1.1 · R1. When it is determined that the flame is out of the flame determination threshold range, it is estimated that the light receiving signals E1 and E2 from the light receiving units 12a and 12b are not due to the radiation energy from the combustion flame, and the process proceeds to step S8 to proceed to the light receiving signal. Suppress flame judgment based on E1.

[Judgment of frequency distribution of received signals E1 and E2 by cross-correlation]
(Outline of Judgment Unit 15)
As another embodiment of the determination unit 15 shown in FIG. 1, flame determination can be performed by obtaining a cross-correlation from the frequency distributions of the received light signals E1 and E2.

In this case, the determination unit 15 divides the mutual correlation of the light receiving signals E1 and E2 output from the light receiving units 12a and 12b into a plurality of time sections for each light receiving signal for a predetermined period, and receives light in each divided section. When the relative level distribution (frequency distribution) of the frequency in a predetermined range is obtained from the signal and the ratio of the integrated values of the relative level distribution of the frequencies between the divided sections is all within the predetermined flame determination threshold range, the light receiving units 12a and 12b It is assumed that the light input to is likely to be emitted from the flame, and control is performed to determine and detect the presence or absence of the flame as one element of determining the presence or absence of the flame.

(Flame judgment based on the cross-correlation of the frequency distribution of the judgment part)
FIG. 8 is an explanatory diagram showing the frequency distribution of the light receiving signals E1 and E2 output from each of the light receiving units 12a and 12b of FIG. 1 when the radiation energy radiated from the combustion flame is observed.

As shown in FIG. 8, when the radiation energy radiated from the combustion flame is observed on the frequency axis, a frequency characteristic showing a higher output level on the frequency side lower than 8 Hz can be obtained, so that the actual flame flicker frequency is obtained. Exists in the frequency band up to 8 Hz, and the high frequency side above 8 Hz, for example up to 16 Hz, shows a low level. Therefore, for the mutual correlation of the frequency distributions of the received light signals E1 and E2, for example, the correlation of the frequency distribution on the low frequency side in the range up to 8 Hz may be determined.

First, the determination unit 15 A / D-converts the light-receiving signals E1 and E2 of the predetermined period T = 2 seconds output from the light-receiving units 12a and 12b and stores them in the buffer memory. It is divided into T1, T2, T3, and T4, and the received signals E1 and E2 in each time interval T1 to T4 are subjected to fast Fourier transform (FFT) to obtain the relative level distribution of the frequency in each time interval.

Subsequently, the determination unit 15 obtains the integrated values Σf11, Σf12, Σf13, Σf14 of the relative level distribution of the frequencies of the respective sections T1 to T4 of the received light signal E1, and also the light receiving signal E2 of each section T1 to T4. The integrated values Σf21, Σf22, Σf23, and Σf24 of the relative level distribution of frequencies are obtained.

Next, the determination unit 15 sets the integrated values Σf11, Σf12, Σf13, Σf14 of the frequency distribution of the received light signal E1 and the integrated values Σf21 Σf22, Σf23, Σf24 of the frequency distribution of the received signal E2 for each of the same time intervals T1 to T4. Ratio of Rf1, Rf2, Rf3, Rf4,
Rf1 = Σf11 / Σf21 equation (8)
Rf2 = Σf12 / Σf22 equation (9)
Rf3 = Σf13 / Σf23 equation (10)
Rf4 = Σf14 / Σf24 equation (11)
This is used as the cross-correlation of the frequency distributions of the received light signals E1 and E2.

In order to determine the cross-correlation of the relative level distributions of the frequencies of the received light signals E1 and E2, the determination unit 15 determines the flame having the lower limit threshold value TH1 and the upper limit threshold value TH2 based on the ratio Rf1 of the integrated values of the first time interval T1. Set the threshold range.

The determination unit 15 sets the lower limit threshold value THf1 and the upper limit threshold value THf2 to a flame determination threshold range of, for example, ± 10% with respect to the ratio Rf1 of the first time interval T1, THf1 = 0.9 · Rf1, THf2 = 1.1 · Rf1. Set to.

When the flame determination threshold range having the lower limit threshold value TH1 and the upper limit threshold value TH2 is set in this way, the determination unit 15 determines whether or not the following conditions are satisfied.
0.9Rf1 ≤ Rf2 ≤ 1.1 Rf1 equation (12)
0.9Rf1 ≤ Rf3 ≤ 1.1 Rf1 equation (13)
0.9Rf1 ≤ Rf4 ≤ 1.1 Rf1 equation (14)

When the determination unit 15 determines that all the conditions of the above equations (12) to (14) are satisfied, that is, the remaining time with respect to the ratio Rf1 of the integrated values of the relative level distributions of the frequencies in the first time interval T1. When the ratio Rf2 to Rf4 of the integrated values of the relative level distributions of all the frequencies in the sections T2 to T4 is within the predetermined flame determination threshold range, the frequency distributions of the light receiving signals E1 and E2 are substantially similar, and the light receiving units 12a and 12b Can be presumed to output the light receiving signals E1 and E2 due to the radiation energy from the combustion flame, and can be used as one element of the judgment of the presence or absence of the flame, and for example, the flame judgment based on the light receiving signal E1 is allowed.

Further, when the determination unit 15 determines that at least one of the conditions of the above equations (12) to (14) is not satisfied, that is, the remaining ratio Rf1 of the integrated value of the frequency distribution in the first time interval T1. When at least one of Rf2 to Rf4, which is the ratio of the integrated values of the relative level distributions of the frequencies in the time intervals T2 to T4, is out of the predetermined flame determination threshold range, the light receiving units 12a and 12b receive light from radiation energy from other than the combustion flame. It can be estimated that the signals E1 and E2 are being output, and the flame judgment based on the received light signal E1 is suppressed without considering it as one element with flame.

(Processing operation of flame judgment based on frequency distribution correlation)
FIG. 9 is a flowchart showing a procedure of the processing operation of the determination unit of FIG. 1 for determining the correlation of the frequency distributions of the two received signals.

(Step S11)
First, the determination unit 15 captures the light receiving signals E1 and E2 output from the light receiving units 12a and 12b via the A / D conversion ports 30a and 30b at a predetermined sampling cycle for a predetermined time T, for example, T = 2 seconds. Temporarily store in buffer memory.

(Step S12)
Next, the determination unit 15 divides the light receiving signals E1 and E2 of the predetermined period T captured in step S11 into four sections T1, T2, T3, and T4, and fast Fourier transforms the light receiving signals E1 in each section T1 to T4. The integral values of the relative level distribution in the frequency range of 8 Hz or less Σf11, Σf12, Σf13, Σf14 and the received signal E2 are fast Fourier transformed and the product integral values of the relative levels in the frequency range of 8 Hz or less Σf21, Σf22, Σf23, Σf24. Is calculated.

It is desirable that the processes after step S12 be executed when the signal level of the light receiving signal E1 taken in from the A / D conversion port 30a by the determination unit 15 becomes equal to or higher than a predetermined threshold value.

(Step S13)
Next, the determination unit 15 sets the ratio Rf1, Rf2, Rf3, Rf4 of the integrated values of the relative level distributions of the frequencies of the respective sections T1 to T4 of the received light signals E1 and E2 calculated in step S12 to the above equations (8) to (11). ).

(Step S14)
Next, the determination unit 15 sets the lower limit threshold value THf1 and the upper limit threshold value THf2, for example, THf1 = 0.9 · Rf1, THf2 = 1.1 ·. Set to Rf1.

(Step S15)
Next, the determination unit 15 sets the ratio Rf2, Rf3, Rf4 of the integrated values of the frequencies of the remaining sections T2 to T4 following the first section T1 of the received light signals E1 and E2 calculated in step S13 to the above equation (12). )-(14), it is determined whether or not the flame is within the flame determination threshold range having the lower limit threshold value TH1 and the upper limit threshold value TH2.

(Steps S16, S17)
Next, when the determination unit 15 determines in step S16 that all the conditions of the above equations (12) to (14) are satisfied and is within the flame determination threshold range, is it the frequency distribution of the received light signals E1 and E2? It is estimated that the light receiving units 12a and 12b are outputting the light receiving signals E1 and E2 due to the radiation energy from the combustion flame, and it is determined that the light receiving units 12a and 12b are one element of the flame judgment. Allow flame judgment.

(Steps S16, S18)
On the other hand, when the determination unit 15 determines in step S16 that at least one of the conditions of the above equations (12) to (14) is not satisfied, that is, THf1 = 0.9 · Rf1, THf2 = 1.1 · Rf1. When it is determined that the flame is out of the flame determination threshold range, it is estimated that the light receiving units 12a and 12b are outputting the light receiving signals E1 and E2 due to the radiation energy other than the combustion flame, and the process proceeds to step S18 to proceed to the light receiving signal. E1 Suppresses flame judgment.

[Embodiment of a light receiving unit including a plurality of light receiving elements]
FIG. 10 is a block diagram showing a functional configuration according to another embodiment of a flame detection device that adds light receiving signals from a plurality of light receiving elements provided in the light receiving unit.

As shown in FIG. 10, the light receiving sensors 16a and 16b provided in the light receiving units 12a and 12b of the present embodiment include four light receiving elements 22a and 22b, respectively. In the light receiving elements 22a and 22b, for example, four pyroelectric bodies 25a and 25b are arranged on the front side of the substrates 36a and 36b arranged inside the cover members 44a and 44b shown in FIG. As shown in the equivalent circuit, four light receiving elements 22a composed of a pyroelectric body 25a, a high resistance 29 and a FET 27a are provided, and the drain and the gate of each FET 27a are commonly connected to the drain terminal D and the gate terminal G, respectively, and each FET 27a Sources are individually connected to source terminals S1 to S4.

With reference to FIG. 10 again, the outputs of the four light receiving elements 22a and 22b pass through the four pre-filters 24a and 24b, and then the four light receiving signals that become the current outputs are added (current addition) to the preamplifier 26a, It is input to 26b.

Here, since the light-receiving outputs from the four light-receiving elements 22a are input to the preamplifier 26a by adding the light-receiving current after passing through the four pre-filters 24a, the random noise component is increased by the current addition. It is a current addition of the signal component obtained by photoelectric conversion of the radiation energy in the narrow band wavelength band centered at about 4.5 μm, which is emitted from the combustion flame by CO _{2 resonance, and lowers the S / N ratio.} Instead, it is possible to generate a light-receiving signal as a light-receiving current that corresponds to approximately four times the light-receiving output of one light-receiving element.

This point is the same for the outputs from the four light receiving elements 22b, and since the light receiving current is added and input to the preamplifier 26b after passing through the four pre-filters 24b, the random noise component is not included. There is almost no increase due to current addition, and the current is added to the signal component that is obtained by photoelectrically converting the radiation energy in the narrow band wavelength band with a central wavelength of approximately 2.3 μm emitted from the combustion flame, and the S / N ratio is lowered. Instead, it is possible to generate a light-receiving signal as a light-receiving current that corresponds to approximately four times the light-receiving output of one light-receiving element.

In this way, even if the radiation energy radiated from the light-receiving combustion flame is weak, the optical units 12a and 12b add the light-receiving signals converted by photoelectrics by the four light-receiving elements 22a and 22b, thereby causing the light-receiving units 12a and 12b. No. 12 can output light receiving signals E1 and E2 having a sufficient level without lowering the S / N ratio, and can greatly expand the flame detection area.

Since the configurations and functions of the preamplifiers 26a and 26b to the determination unit 15 are the same as those of the embodiment of FIG. 1, the description thereof will be omitted.

Further, the number of the light receiving elements 22a and 22b provided in the light receiving sensors 16a and 16b can be appropriately determined as needed. Further, the number of the light receiving elements 22a and 22b provided in the light receiving sensors 16a and 16b may be the same, or the numbers may be different.

[Tunnel flame detector]
Next, an embodiment when the configuration of the flame detection device shown in the embodiment of FIG. 1 is applied to the flame detection device for a tunnel will be described.

FIG. 12 is a block diagram showing another embodiment of a flame detection device installed in a tunnel to monitor flames.

(Light receiving units 12a, 12b)
As shown in FIG. 12, the light receiving units 12a and 12b are the same as those in the embodiment of FIG. 1, and are _{emitted from a combustion flame by CO 2} resonance in a narrow band wavelength band having a central wavelength of approximately 4.5 μm. The light receiving signal E1 that observes the energy and the light receiving signal E2 that observes the radiation energy in the narrow band wavelength band centered at about 2.3 μm are output, and the A / D conversion ports 30a and 30b provided in the determination unit 15 respectively. Each is converted into a digital received signal and captured.

(Light receiving unit 12c)
The light receiving unit 12c includes a light receiving sensor 16c that converts radiation energy having a predetermined wavelength band different from that of the light receiving sensors 16a and 16b into an electric signal and outputs it. That is, the light receiving unit 12c outputs the light receiving signal E3 obtained by converting the radiation energy in the wavelength band of approximately 5.0 μm to 7.0 μm into an electric signal.

Further, the light receiving unit 12c is a signal that has passed through the preamplifier filter 24c that allows only the signal component of a predetermined frequency band to pass from the light receiving signal output from the light receiving sensor 16c and the signal that has passed through the preamplifier filter 24c, following the light receiving sensor 16c. It is composed of a preamplifier 26c that amplifies the components in the first stage and a main amplifier 28c that amplifies the output from the preamplifier 26c. The light receiving signal E3 output from the main amplifier 28c of the light receiving unit 12c is converted into a digital light receiving signal by the A / D conversion port 30c of the determination unit 15 and read, and is used for the flame determination process.

(Structure of light receiving sensor 16c)
The light receiving sensor 16c receives the optical wavelength filter 20c, which is a long-pass filter composed of a cut-on filter that satisfactorily transmits radiation in a predetermined wavelength band exceeding about 5.0 μm, and the light transmitted through the optical wavelength filter 20c. It is provided with a light receiving element 22c which is an equivalent circuit of FIG. 3 and is converted into an electric signal and output, and has a packaged configuration having a structure similar to that shown in FIG. , 16b and 16b are arranged in a predetermined arrangement in close proximity to each other on a common mounting member 48 provided in the main body cover 46.

(Translucent window 18)
The translucent window 18 is arranged in a predetermined opening provided on the front side of the main body cover 46, which houses the light receiving sensors 16a and 16b together with the light receiving sensors 16a and 16b shown in FIG. 2, on the monitoring area side. The light receiving elements 22a, 22b, 22c of the light receiving sensors 16a, 16b, 16c, which are formed of an infrared translucent member such as sapphire glass, have their respective light receiving limit fields of view regulated by the edge of the translucent window 18. Therefore, a detection area having substantially the same spread angle is set.

(Wavelength transmission characteristics of light receiving sensors 16a to 16c)
FIG. 13 is a characteristic diagram showing the transmittance of the optical wavelength filter and the translucent window applied to the embodiment of FIG. 12 at each wavelength.

As shown in FIG. 13, the transmission characteristic 56 of the light receiving sensor 16a and the transmission characteristic 60 of the light receiving sensor 16b are the same as those in FIG.

On the other hand, the light receiving sensor 16c has a short wave path characteristic 52 in which radiation energy of about 7.0 μm or less is satisfactorily transmitted by sapphire glass which is a translucent window 18, and a long pass filter constituting an optical wavelength filter 20c. By combining with the transmittance characteristic 62, which has a cut-on filter characteristic that satisfactorily transmits the radiation energy in a predetermined wavelength band exceeding about 5.0 μm, the radiation energy in the wavelength band of approximately 5.0 μm to 7.0 μm is increased. It constitutes a wideband bandpass filter having a transmission characteristic 64 that transmits with a transmittance.

(Flame judgment)
When the determination unit 15 determines one element with flame from the mutual correlation of the light receiving signals E1 and E2 output from the light receiving units 12a and 12b for a predetermined period, the light receiving signal E1 and the light receiving signal output from the light receiving unit 12c are output. E3 is taken in via the A / D conversion ports 30a and 30c for a predetermined time, and the signal amplitude is time-integrated for each received signal E1 and E3 to calculate the integrated values ΣE1 and ΣE3. Here, the integrated values ΣE1 and ΣE3 are distinguished as the flame integrated value ΣE1 and the non-flame integrated value ΣE3 for convenience.

Next, the determination unit 15 determines that the light receiving output corresponding to the flame has not been detected when the flame integral value ΣE1 is equal to or lower than the preset reference level, while the flame integral value ΣE1 is the reference level. If it exceeds, the relative ratio (ΣE1 / ΣE3) with the non-flame integral value ΣE3 is calculated, and if the relative ratio (ΣE1 / ΣE3) exceeds the preset threshold, it is determined as a flame. It is one element of the flame judgment, and if it is below the threshold value, for example, it is assumed that there is a light receiving output from a relatively low temperature radiation source other than the flame of a human body or a vehicle, and the flame judgment is not suppressed.

When the determination unit 15 determines one element with flame from the mutual correlation of the light receiving signals E1 and E2 output from the light receiving units 12a and 12b for a predetermined period, as shown in the embodiment of FIG. , The frequency distribution of the frequency band of 8 Hz or less by the fast Fourier transform of the received signal E1 captured for a predetermined time via the A / D conversion port 30a is set as another element, and the complex flame judgment based on a plurality of elements is performed. It may be.

[Modification of the present invention]
In the above embodiment, the cross-correlation of each received signal is obtained by dividing each received signal for a predetermined period into a plurality of time sections, and determining the presence or absence of a combustion flame from the ratio of the signal integral values of the divided sections. However, the presence or absence of the combustion flame may be determined from the cross-correlation of appropriate values such as the correlation coefficient of each received signal, without being limited to the ratio of the signal integral values.

Further, in the above embodiment, as a flame detection device for a tunnel, there is a correlation between observation of radiation energy in a wavelength band of around 4.5 μm, which is _{the CO 2 resonance radiation band of a combustion flame, and a wavelength band of around 2.3 μm.} And the radiation energy in the wavelength band around 5.0 μm is observed to judge the flame, but the correlation by the observation of the radiation energy in the wavelength band around 4.5 μm and the wavelength band of 2.3 μm and around 3.8 μm The presence or absence of a flame may be determined by observing the radiation energy in the wavelength band of.

In addition to the correlation by observing the radiation energy in the wavelength band around 4.5 μm and the wavelength band of 2.3 μm, the radiation energy in the wavelength band around 3.8 μm and the wavelength band around 5.0 μm was observed to observe the flame. The presence or absence may be determined.

In addition, the present invention includes appropriate modifications that do not impair its purpose and advantages, and is not limited by the numerical values shown in the above embodiments.

10: Flame detection device 12a, 12b, 12c: Light receiving unit 15: Judgment unit 16a, 16b, 16c: Light receiving sensor 18: Translucent window 20a, 20b, 20c: Optical wavelength filter 22a, 22b, 22c: Light receiving element 24a, 24b, 24c: Pre-filter 25a, 25b: Pyroelectric body 26a, 26b, 26c: Preamplifier 27a, 27b: FET
28a, 28b, 28c: Main amplifier 30a, 30b, 30c: A / D conversion port

Claims (3)

A plurality of light receiving units that output light receiving signals that observe radiation energy in different predetermined wavelength bands in the monitoring area, and
The first element of determining the presence or absence of a combustion flame is the cross-correlation between the light-receiving signals of each signal amplitude obtained from each light-receiving signal for a predetermined period observed and output by each light-receiving unit at substantially the same time. Judgment department and
With
As the first element, the determination unit divides each received signal for the predetermined period into a plurality of divided sections corresponding to a plurality of time sections, and among the plurality of divided sections within the predetermined period. The presence or absence of a combustion flame is determined based on the ratio of the integrated value of the signal amplitude for the reference divided section to the mutual ratio between the received signals to the integrated value of the signal amplitude for the other divided sections. A flame detection device characterized by the fact that.
In the flame detection device according to claim 1, the determination unit determines the presence or absence of a combustion flame as a second element of determining the presence or absence of a combustion flame based on at least one of the received signals for the predetermined period. A flame detection device characterized in that the presence or absence is determined and a flame is detected based on the determination result of the first element and the determination result of the second element.
In the flame detection device according to claim 2, the determination unit determines, as the second element, that there is a combustion flame when the signal amplitude of at least one received signal is equal to or greater than a predetermined threshold value. Flame detection device.

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