JP2016128796A - Flame detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To certainly determine the presence/absence of combustion flame on the basis of the simultaneity of time variation of a light receiving output from a plurality of light receiving units for a plurality of wavelength bands of radiation energy radiated from combustion flame.SOLUTION: A plurality of light receiving units 12a and 12b are disposed. The light receiving units 12a and 12b output light receiving signals E1 and E2 for which different wavelength bands are observed, of the radiation energy. A determination unit 15 sets, as one element for determining the presence/absence of combustion flame, the mutual correlation between the light receiving signals corresponding a predetermined period that are observed and output by the light receiving units 12a and 12b at a substantially same time. When the correlation is high, the determination unit allows flame determination based on the added light receiving signal E1, for example. When the correlation is low, the determination unit suppresses the flame determination.SELECTED DRAWING: Figure 1

Description

The present invention relates to a flame detection device that detects infrared radiation generated by CO ₂ resonance during flammable combustion to determine 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 the flammable combustion, it is generated at the time of flammable combustion in order to distinguish between a flame and an infrared radiator other than the flame. Flames of two-wavelength type, three-wavelength type, etc. that detect radiation intensity in a plurality of wavelength bands including a wavelength band by resonance emission of CO ₂ and detect the presence or absence of flames by a relative ratio of detection values in the plurality of wavelength bands Detection devices and flame detection methods are well known.

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

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

As shown in FIG. 14, in the spectral characteristic 100 of the combustion flame, there is a peak of the radiation relative intensity in the wavelength band near 4.5 μm due to the resonance emission of CO ₂ , and there is a characteristic that exists in the vicinity of this peak wavelength. For example, a wavelength band having a low radiation relative 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 emission of CO _{2 in} the 4.3 μm band. However, when the combustion flame is actually observed, it has been empirically shown that a peak of radiation intensity appears in the vicinity of 4.4 to 4.5 μm. Therefore, hereinafter, unless otherwise specified, the CO ₂ resonance radiation band refers to the 4.4 to 4.5 μm band.

  In the two-wavelength flame detection device, for example, each radiation energy in the wavelength band near 4.4 to 4.5 μm and the wavelength band near 5.1 μm is converted by a narrow band optical wavelength bandpass filter. Selectively transmit (pass), detect the radiation energy by the light receiving sensor, photoelectrically convert it, and apply predetermined processing such as amplification to obtain an electrical signal corresponding to the amount of energy (hereinafter referred to as “light receiving signal”). The presence / absence of flame is determined by taking the relative ratio of the received light signal levels of the respective wavelength bands and comparing it with a predetermined threshold value.

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

Further, for example, in addition to the above-described two wavelengths, the radiation energy in the wavelength band near the wavelength of 3.8 μm, for example, near the wavelength of 4.4 to 4.5 μm which is the resonance radiation band of CO ₂ is a two-wavelength type. There is also known a three-wavelength flame detection device that detects the presence or absence of a flame based on the relative ratio of each received light signal in these three wavelength bands, and discriminates between the 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 a vehicle flame in a road tunnel, the flame detection device has a detection area in both the left and right directions and is arranged adjacent to the longitudinal direction of the tunnel. For example, the detection areas are continuously arranged at intervals of 25 m or 50 m so that the detection areas overlap with each other. For example, a pyroelectric material is used as the light receiving element.

Kosho 55-33119 Koho 59-34252 Japanese Patent No. 3357330

By the way, in the conventional flame detection device, each light reception by radiation energy in a wavelength band near 4.5 μm due to CO ₂ resonance radiation from the combustion flame and in a wavelength band not including this wavelength band, for example, near 5.1 μm. The relative ratio of the signal levels is taken and compared with a predetermined threshold value to determine the presence or absence of flame. However, depending on the setting of the threshold value, it may be impossible to accurately determine the presence or absence of flame. In order to determine the presence / absence more accurately, it is desired to determine the presence / absence of flame by incorporating elements other than the relative ratio of the received light signal levels in different wavelength bands.

  The present invention provides a flame detection apparatus that can reliably determine the presence or absence of a combustion flame based on the simultaneity of temporal changes in light reception 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, a photoelectric conversion unit including a light receiving element, and a photoelectric conversion signal from the light receiving sensor as necessary, for example, amplifying and processing the light receiving signal. A signal detection circuit unit including an electric circuit to be output as.

(Flame detection device)
The present invention is a flame detection device that detects and detects the presence or absence of a combustion flame by observing the radiation energy emitted from the combustion flame,
A plurality of light-receiving units that emit light-receiving signals observing different predetermined wavelength bands emitted from the combustion flame,
A determination unit that uses the correlation between the light reception signals for a predetermined period of time observed and output at each light receiving unit at approximately the same time as one element for determining whether or not there is a combustion flame;
It is provided with.

(Details of light receiving unit)
1 light receiving unit is
An optical wavelength filter that selectively transmits light of a predetermined wavelength band including a CO ₂ resonance radiation band emitted from the combustion flame;
One or a plurality of light receiving elements that output light reception signals based on electrical signals obtained by photoelectrically converting light that has passed through the optical wavelength filter;
A light receiving sensor having
Other light receiving units
An optical wavelength filter that selectively transmits light of a predetermined wavelength band that does not include a CO ₂ resonance radiation band, emitted from a combustion flame;
One or a plurality of light receiving elements that output light reception signals based on electrical signals obtained by photoelectrically converting light that has passed through the optical wavelength filter;
A light receiving sensor.

(Details of light receiving unit)
Each of the light receiving units further includes a frequency selection unit that selectively extracts a signal component of a predetermined frequency band from an electrical signal from the light receiving sensor,
An amplification unit that amplifies the signal component output from the frequency selection unit;
Is provided.

(Two light receiving units)
At least two light receiving units are provided.

(Signal amplitude correlation)
The determination unit determines the presence / absence of a combustion flame based on the ratio of the signal integration values of the divided sections obtained by dividing the correlation between the received light signals into a plurality of time sections.

(Flame judgment by correlation of signal amplitude)
The determination unit determines that the light input to the light receiving unit may be due to radiation from the flame when all the ratios of the signal integration values of the respective divided sections are within a predetermined flame determination threshold range. One element.

(Details of flame judgment by correlation of signal amplitude)
The decision part
When the light reception signals E1 to Em output from the plurality of light reception units for a predetermined period are divided into time intervals of an integer n of 1 or more, the signal integration value of one light reception signal E1 for each of these n division intervals. The ratios R1 to Rn of ΣE11 to ΣE1n and the integrated values ΣE11 to ΣEmn of other received light signals Em corresponding to the same time interval are
R1 to Rn = ΣE11 / ΣEm1 to ΣE1n / ΣEmn
As sought
When all of the signal integral value ratios R2 to Rn in the remaining time interval with respect to the signal integral value ratio R1 in the first time interval are within the predetermined flame determination threshold range, the light input to the light receiving unit is flame. There is a possibility of radiation from, and it is one element of the judgment of the presence of flame.

(Correlation of frequency distribution)
The determination unit determines the correlation between the received light signals by comparing the frequency distributions obtained from the received light signals for a predetermined period.

(Flame judgment by correlation of frequency distribution)
The decision part
The correlation between each received light signal is obtained by dividing each received light signal for a predetermined period into a plurality of time intervals, and obtaining a relative level distribution of a predetermined range of frequencies,
If all the ratios of the integrated values of the frequency relative level distribution of each divided section are within the predetermined flame judgment threshold range, the light input to the light receiving unit may be due to radiation from the flame, One element.

(Basic effect)
The present invention is a flame detection device that detects and detects the presence or absence of a combustion flame by observing the radiation energy emitted from the combustion flame, and receives received light signals emitted from the combustion flame and observing different predetermined wavelength bands. A plurality of light receiving units to be output, and a determination unit that uses a correlation between the respective light reception signals for a predetermined period of time observed and output at each light receiving unit as one element for determining whether or not there is a combustion flame. Therefore, if the correlation is high, the temporal changes in the radiation energy radiated from the combustion flame are approximately the same, and therefore the light input to the light receiving unit may be due to the radiation from the flame. By using one element for determining whether there is a flame, the presence or absence of a combustion flame can be more reliably determined and detected.

(Effects of the light receiving unit)
Further, the one light receiving unit receives an optical wavelength filter that selectively emits light in a predetermined wavelength band including a CO ₂ resonance radiation band emitted from the combustion flame, and receives light transmitted through the optical wavelength filter with a light receiving element. A light receiving sensor having one or a plurality of light receiving elements for outputting a light receiving signal based on the photoelectrically converted electrical signal, and the other light receiving unit emits from the combustion flame and has a predetermined wavelength band not including a CO ₂ resonance radiation band A light receiving sensor having an optical wavelength filter for selectively transmitting the light of the light, and one or a plurality of light receiving elements for outputting a light reception signal based on an electric signal obtained by photoelectrically converting the light transmitted through the optical wavelength filter. In addition, each of the light receiving units further includes a frequency selection unit that selectively extracts a signal component in a predetermined frequency band from an electrical signal from the light reception sensor, and a frequency selection unit. Each of the photoelectric units is radiated from the combustion flame and has a band wavelength radiation energy having a central wavelength of approximately 4.5 μm and a radiation having a band wavelength different from the radiation energy. It is possible to photoelectrically convert energy and output a light reception signal.

  In addition, by providing multiple light receiving elements in the light receiving sensor, for example, variations due to differences in the light receiving characteristics of the multiple light receiving elements can be suppressed and aligned by adding the light receiving outputs photoelectrically converted by the multiple light receiving elements. And

(Two light receiving units)
In addition, by providing at least two light receiving units, the determination unit can correlate the light reception signals for a predetermined period in different wavelength bands, which are observed and output by the two light receiving units at substantially the same time period. It can be used as another element of flame judgment.

(Effect of flame judgment by correlation of signal amplitude)
Further, the determination unit divides the correlation between the light reception signals into a plurality of time intervals for each of the light reception signals for a predetermined period, and all of the ratios of the signal integration values between the division intervals are within a predetermined flame determination threshold range. If it is within, the light input to the light receiving unit may be caused by radiation from the flame, and by making it one element of the presence of flame, it is possible to more reliably determine and detect the presence of a combustion flame To do.

(Effect of flame judgment details by correlation of signal amplitude)
Further, when the determination unit divides the light reception signals E1 to Em for a predetermined period output from the plurality of light reception units into time intervals of an integer n of 1 or more, one light reception is performed for each of these n division intervals. The ratios R1 to Rn of the signal integration values ΣE11 to ΣE1n of the signal E1 and the integration values ΣE11 to ΣEmn of the other received light signals Em corresponding to the same time interval,
R1 to Rn = ΣE11 / ΣEm1 to ΣE1n / ΣEmn
When all of the signal integration value ratios R2 to Rn of the remaining time interval with respect to the signal integration value ratio R1 of the first time interval are within the predetermined flame determination threshold range, the signal is input to the light receiving unit. Since there is a possibility that the light is emitted from the flame and it is set as one element of the judgment of the presence of the flame, based on the correlation in which the amplitude changes of the two light reception signals E1 and E2 in the first time interval are approximately the same, The correlation deviations in the remaining time intervals are compared, and if the correlation deviation is small, it is possible to determine and detect the presence of the combustion flame.

(Effect of flame judgment by correlation of frequency distribution)
In addition, the determination unit obtains a relative level distribution of a predetermined range of frequencies obtained by dividing the correlation between the respective received light signals into a plurality of time sections for each predetermined period, and the frequency relative level distribution between the divided sections. If all of the integrated value ratios are within the predetermined flame judgment threshold range, the light input to the light receiving unit may be caused by radiation from the flame, and the flame is determined as one element of the judgment of the presence of flame. It is possible to more reliably determine and detect the existence of

Block diagram showing an embodiment of a flame detection device Explanatory drawing which showed schematic structure of the light reception unit applied to the flame detection apparatus of FIG. Circuit diagram showing an equivalent circuit of the light receiving sensor of FIG. Characteristic diagram showing the radiation spectrum of a combustion flame The characteristic view which showed the transmittance | permeability in each wavelength of the optical wavelength filter and translucent window applied to embodiment of FIG. A signal waveform diagram showing a light reception signal output from each of the light reception 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 two light reception signals. Explanatory diagram showing the frequency distribution of the received light signal 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 frequency distributions of two received light signals. The block diagram which showed embodiment of the flame detection apparatus which adds the light reception signal from the several light receiving element provided in the light reception unit Circuit diagram showing an equivalent circuit of the light receiving sensor of FIG. The block diagram which showed other embodiment of the flame detection apparatus which installs in a tunnel and monitors a fire The characteristic view which showed the transmittance | permeability in each wavelength of the optical wavelength filter and translucent window applied to embodiment of FIG. Characteristic diagram showing the radiation spectrum of combustion flame and other typical radiators

[Outline of flame detector]
FIG. 1 is a block diagram showing an embodiment of a flame detection apparatus according to the present invention in functional configuration, FIG. 2 is an explanatory diagram showing a schematic configuration of a light receiving unit applied to the flame detection apparatus of FIG. 1, and FIG. 4 is a circuit diagram showing an equivalent circuit of the light receiving sensor of FIG. 2, FIG. 4 is a characteristic diagram showing the radiation spectrum of the combustion flame, and FIG. 5 is each wavelength of the optical wavelength filter and translucent window applied to the embodiment of FIG. It is the characteristic view which showed the transmittance | permeability in.

As shown in FIG. 1, the flame detection apparatus 10 of the present embodiment observes radiation energy having a spectral characteristic 50 shown in FIG. 4 radiated from a combustion flame existing in a monitoring region. A light receiving unit 12a for observing radiation energy in a narrow band wavelength band having a central wavelength of approximately 4.5 μm emitted from the flame by CO ₂ resonance and outputting a light reception signal E1 by photoelectric conversion, and CO ₂ resonance from the combustion flame A light receiving unit 12b that outputs a light reception signal E2 by photoelectric conversion by observing radiation energy in a narrow band wavelength band having a center wavelength of approximately 2.3 μm, for example, which does not include approximately 4.5 μm emitted by A determination unit 1 that uses the correlation between the received light signals E1 and E2 for a predetermined period of time observed and output at approximately the same time in 12b as one element for determining whether or not there is a combustion flame. It comprises a door.

(Light receiving unit configuration)
The light receiving unit 12a includes a light receiving sensor 16a that converts radiation energy, which is emitted from the combustion flame by CO ₂ resonance and has a narrow band wavelength band having a central wavelength of approximately 4.5 μm, into an electric signal, and outputs the electric signal. The pre-filter 24a that passes only the signal component of a predetermined frequency band from the light reception signal output from the pre-amplifier 26a, the preamplifier 26a that amplifies the signal component that has passed the pre-filter 24a, and the output from the pre-amplifier 26a are described later. And a main amplifier 28a that amplifies the signal level suitable for the flame determination process and outputs the light reception signal E1.

  In addition, the light receiving unit 12b includes a light receiving sensor 16b for converting radiation energy having a narrow band wavelength band having a center wavelength of approximately 2.3 μm, which is radiated from the combustion flame, into an electric signal, and a light receiving sensor 16b. A pre-filter 24b that passes only a signal component in a predetermined frequency band from the output light reception signal, a preamplifier 26b that amplifies the signal component that has passed through the pre-filter 24b, and an output from the preamplifier 26b will be described later. The main amplifier 28b is configured to amplify the signal level suitable for flame determination processing and output the light reception signal E2.

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

  The light reception signals E1 and E2 output from the light reception units 12a and 12b through the amplifiers 28a and 28b are converted into digital light reception signals by the A / D conversion ports 30a and 30b provided in the determination unit 15 and read. The flame determination described later is executed. Each configuration will be specifically described below.

(Light receiving sensors 16a and 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 light-transmitting window 18 shared. As shown in FIG. 5, the optical wavelength filter 20a transmits only light in a predetermined band including a wavelength band of approximately 4.5 μm radiated by CO ₂ resonance generated during flammable combustion with a high transmittance. An optical bandpass filter having a wavelength of, for example, selectively transmits light in a predetermined band including 4.5 μm and not including other wavelength bands described later. The light receiving element 22a has a photoelectric conversion function using a pyroelectric material and an FET, receives the light transmitted through the optical wavelength filter 20a, converts it into an electrical signal, and outputs it.

  Specifically, as shown in FIG. 2, the light receiving sensor 16a includes a plurality of pyroelectric bodies 25a disposed on the front surface of the substrate 36a and a light receiving element 22a including FETs 27a disposed on the back surface of the substrate 36a. A substrate mounting portion 40a for supporting 36a on the base portion 38a, a base portion 38a provided with a terminal 42a extending from the back side on the substrate mounting portion 40a side, and a narrow band-pass filter in front of the light receiving element 22a. And a cover member 44a provided with the 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 through, for example, a parallel circuit of the pyroelectric body 25 and the high resistance 29, and the drain and source of the FET 27 are connected. The drain terminal D and the source terminal S are connected to each other.

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

  Specifically, as shown in FIG. 2, the light receiving sensor 16b includes a plurality of pyroelectric bodies 25b disposed on the surface of the substrate 36b and a light receiving element 22b including FETs 27b disposed on the back surface of the substrate 36b. A substrate mounting portion 40b for supporting 36b on the base portion 38b, a base portion 38b provided with a terminal 42b extending from the back side on the substrate mounting portion 40b side, and a narrow band-pass filter in front of the light receiving element 22b. And a cover member 44b provided with the 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 on the common attachment member 48 provided in the main body cover 46, close to each other.

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

(Translucent window 18)
The translucent window 18 is arranged on a predetermined opening provided on the front side of the light receiving sensors 16a and 16b 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 accommodated. For example, it is formed of an infrared translucent member such as sapphire glass. For this reason, in the light receiving elements 22a and 22b, detection areas having substantially the same spread angle are set by restricting the respective light receiving limit fields of view at the edge portions of the translucent windows 20a and 20b.

  Here, the sapphire glass constituting the translucent window 48 is, as shown in FIG. 5, a short wave path characteristic 52 that transmits light in a wavelength band of approximately 7.0 μm or less, in other words, approximately 7 in general. Functions as a filter member having a long wave cut characteristic that blocks radiation having a wavelength longer than about 0.0 μm. Moreover, in this embodiment, the translucent window 18 is demonstrated as what is contained in the light reception sensors 16a and 16b as a shared member.

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

  The sapphire glass, which is the translucent window 18 in FIG. 1, has a short wave path characteristic 52 that allows good transmission of radiation of about 7.0 μm or less, and an optical wavelength filter 20a, and has a central wavelength of about 4.5 μm. The band pass filter transmits a radiation energy in a wavelength band of approximately 4.5 μm with a high transmittance by combining with a transmittance characteristic 54 that transmits a radiation energy in a wavelength band near the center wavelength with a high transmittance. The transmission characteristic 56 constitutes a narrow band-pass filter.

  Further, the sapphire glass that is the light-transmitting window 18 has a short wave path characteristic 52 that allows good transmission of radiation of approximately 7.0 μm or less and a wavelength around 2.3 μm that constitutes the optical wavelength filter 20a. In combination with the transmission characteristic 58 that transmits the radiation energy in the wavelength band near the center wavelength of the band-pass filter with a high transmittance, the transmission that transmits the radiation energy in the wavelength band of approximately 2.3 μm with a high transmittance. A narrow-band bandpass filter having the characteristic 60 is constructed.

(Pre-filters 24a and 24b)
The pre-filters 24a and 24b function as a frequency selection unit, and only the signal components in a specific frequency band used for the flame determination process from the light-receiving signals output from the light-receiving elements 22a and 22b of the light-receiving sensors 16a and 16b. For example, an active filter that outputs a light receiving signal including a signal component in 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 amplify the light reception signals input via the pre-filters 24a and 24b at a first stage with a predetermined amplification factor, and the main amplifiers 28a and 28b describe the light reception signals from the preamplifiers 26a and 26b, which will be described later. Amplified to a signal level suitable for flame determination processing and output as light reception signals E1 and E2.

(A / D conversion ports 30a, 30b)
The A / D conversion ports 30 a and 30 b are A / D converters provided as input ports of the determination unit 15, and convert the light reception signals (analog light reception signals) E 1 and E 2 into digital signals suitable for the digital processing of the determination unit 15. And read.

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

  The determination unit 15 performs control using the correlation between the light reception signals E1 and E2 for a predetermined period of time observed and output by the light reception units 12a and 12b as one element for determining the presence or absence of the combustion flame.

  That is, the determination unit 15 obtains a mutual correlation between the light reception signals E1 and E2 for a predetermined period observed and output by the light reception units 12a and 12b at approximately the same period, and when the mutual correlation satisfies a predetermined standard, The light input to the light receiving units 12a and 12b is assumed to have a possibility of radiation from the flame, and as one element with the flame, control is performed to determine and detect the presence or absence of the flame.

(Flame judgment based on the correlation between the received light signals E1 and E2)
The details of the flame determination performed by obtaining the correlation between the light reception signals E1 and E2 for a predetermined period of time observed and output by the light reception units 12a and 12b by the determination unit 15 are described as follows.

  FIG. 6 shows a light reception signal E1 based on radiation energy in a narrow band wavelength band having a center wavelength of 4.5 μm, which is output from the light receiving unit 12a of FIG. 1 when the radiation energy radiated from the combustion flame is observed, and the light receiving unit 12b. 2 shows a light reception signal E2 by radiation energy in a narrow band wavelength band having a center wavelength of 2.3 μm output from the light reception signal E2, and the light reception signal E2 has a similar waveform with a low level with respect to the light reception signal E1.

  In addition, the signal waveforms of the received signals E1 and E2 shown in FIG. 6 are converted into digital received light 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. A 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 a target of one correlation calculation is shown as an analog waveform.

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

Next, for each of the same time intervals T1 to T4, the determination unit 15 compares the ratio R1, R2 of the signal integration values ΣE11, ΣE12, ΣE13, ΣE14 of the light reception signal E1 and the integration values ΣE21ΣE22, ΣE23, ΣE24 of the light reception signal E2. , R3, R4,
R1 = ΣE11 / ΣE21 Formula (1)
R2 = ΣE12 / ΣE22 Formula (2)
R3 = ΣE13 / ΣE23 Formula (3)
R4 = ΣE14 / ΣE24 Formula (4)
And this is taken as the correlation between the received light signals E1 and E2.

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

  The determination unit 15 sets the lower limit threshold TH1 and the upper limit threshold Th2 to the upper and lower thresholds TH1 and TH2 of, for example, ± 10% with respect to the ratio R1 of the first time interval T1, and TH1 = 0.9 · R1, TH2 = 1. Set the flame judgment threshold range as .1 · R1. Generally expressing this, the lower limit threshold TH1 (= α · R1) is set by multiplying the ratio R1 of the signal integral value in the first interval T1 by a predetermined constant α less than 1, and a predetermined value exceeding 1 This means that the upper limit threshold TH2 (= β · R1) is set by multiplying by a constant β, and the values of the coefficients α and β can be set as appropriate.

When the flame determination threshold range having the lower limit threshold TH1 and the upper limit threshold TH2 is set as described above, the determination unit 15 determines whether or not the following condition is satisfied.
0.9R1 ≦ R2 ≦ 1.1R1 Formula (5)
0.9R1 ≦ R3 ≦ 1.1R1 Formula (6)
0.9R1 ≦ R4 ≦ 1.1R1 Formula (7)
When the determination unit 15 determines that all the conditions of the expressions (5) to (7) are satisfied, that is, the signal integration value ratio R1 of the first time interval T1 is the remaining time intervals T2 to T4. When the ratios R2 to R4 of all the signal integration values are within a predetermined flame determination threshold range, the amplitude waveforms of the light reception signals E1 and E2 are substantially similar, and the light reception units 12a and 12b both receive radiation energy from the combustion flame. Since it can be estimated that the observation is performed in a different wavelength band, in this case, as one element of the determination of the presence of a flame, for example, a narrow band wavelength band having a central wavelength of 4.5 μm radiated from the combustion flame by CO ₂ resonance. The flame determination based on the light reception signal E1 having a sufficient amplitude level due to the radiation energy is allowed.

  In this case, as a flame determination based on the light reception signal E1, the determination unit 15 obtains a frequency distribution from the light reception signal E1 by a calculation method such as fast Fourier transform (FFT), for example, and includes a fluctuation frequency unique to the flame, for example, a frequency distribution of 8 Hz or less. When the integral 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 for determining the flame is performed in consideration of other elements of flame determination.

  In addition, when the determination unit 15 determines that at least one of the conditions (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 signal integration value ratios R2 to R4 of T2 to T4 is out of a predetermined flame determination threshold range, it can be estimated that the received light signals E1 and E2 are from radiation energy other than the combustion flame. It is not an element, and flame judgment based on the light reception signal E1 is suppressed.

(Generalized judgment of mutual correlation)
Here, when the number of sections i dividing the predetermined period T is generalized as i = 1 to n and the received light signals are generalized as E1 to Em, the determination unit 15 divides the predetermined period T into the sections T1 to Tn. The integrated values ΣE11 to ΣE1n of the time intervals T1 to Tn are obtained for the light reception signal E1 as a value (amplitude integral value) obtained by integrating the absolute values of the differences with respect to the reference potential which is the middle point of the light reception signals E1 and Em. Further, for the received light signal Em, the integral values ΣEm1 to ΣEm2n of the time intervals T1 to T4 are obtained, and the ratios R1 to R4 of both are obtained as follows:
R1 to Rn = ΣE11 / ΣEm1 to ΣE1n / ΣEmn
This is determined as the correlation between the received light signals E1 and Em.

Next, when the lower limit threshold TH1 and the upper limit threshold TH2 are set in the same manner as described above, the determination unit 15 determines whether or not a condition that falls 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 reception signals E1 and E2 are substantially similar, and it can be estimated that the light reception units 12a and 12b are observing radiation energy from the combustion flame. The flame determination based on the light reception signal E1 is allowed as one element of the determination of the presence of flame.

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

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

(Step S1)
First, the determination unit 15 captures the light reception signals E1 and E2 output from the light reception units 12a and 12b through the A / D conversion ports 30a and 30b at a predetermined sampling period 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 reception signals E1 and E2 of the predetermined period T captured in step S1 into four time intervals T1, T2, T3, and T4, and the signal amplitude of the light reception signal E1 of each division interval T1 to T4. Integral values ΣE11, ΣE12, ΣE13, ΣE14 and integral values ΣE21, ΣE22, ΣE23, ΣE24 of the received light signal E2.

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

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

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

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

(Steps S6 and S7)
Next, the determination unit 15 determines that the ratios R2, R3, and R4 of the integral values of the time intervals T2 to T4 are all in the flame determination threshold range when all the conditions of the expressions (5) to (7) are satisfied in step S6. If it is determined that the received light signal is within the range, the amplitude waveforms of the light reception signals E1 and E2 are approximately similar and are estimated to be a light reception signal based on the radiation energy from the combustion flame. Proceeding to allow flame judgment based on the light reception signal E1.

(Steps S6 and S8)
On the other hand, the determination unit 15 determines that at least one of the conditions (5) to (7) is not satisfied in step S6, that is, TH1 = 0.9 · R1, TH2 = 1.1 · R1. If it is determined that it is outside the flame determination threshold range, it is estimated that the light reception 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 receive the light reception signal. The flame judgment based on E1 is suppressed.

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

  In this case, the determination unit 15 divides the correlation between the light reception signals E1 and E2 output from the light reception units 12a and 12b into a plurality of time intervals for each light reception signal for a predetermined period, and receives light in each division interval. When a relative level distribution (frequency distribution) of a predetermined range of frequencies is obtained from the signal and the ratios of the integrated values of the relative level distributions of the frequencies of the respective divided sections are all within the predetermined flame determination threshold range, the light receiving units 12a and 12b. Assuming that there is a possibility that the light input to is due to radiation from the flame, a control for judging and detecting the presence or absence of flame is performed as one element of the judgment of the presence of flame.

(Flame judgment based on cross-correlation of frequency distribution of judgment part)
FIG. 8 is an explanatory diagram showing the frequency distribution of the light reception signals E1 and E2 output from each of the light reception 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 high output level on the lower frequency side than about 8 Hz is obtained, so that the substantial flicker frequency of the flame is obtained. Exists in the frequency band up to 8 Hz, and the high frequency side exceeding 8 Hz, for example, up to 16 Hz shows a low level. For this reason, the correlation between the frequency distributions of the light reception signals E1 and E2 may be determined, for example, by determining the correlation of the frequency distribution on the low frequency side in a range up to 8 Hz.

  First, the determination unit 15 A / D converts the light reception signals E1 and E2 output from the light receiving units 12a and 12b for a predetermined period T = 2 seconds and stores them in the buffer memory, for example, four time intervals of 500 milliseconds. The signals are divided into T1, T2, T3, and T4, and the received light signals E1 and E2 in each time interval T1 to T4 are subjected to fast Fourier transform (FFT), and the relative level distribution of the frequency in each time interval is obtained.

  Subsequently, the determination unit 15 obtains integral values Σf11, Σf12, Σf13, and Σf14 of the relative level distribution of the frequency in each section T1 to T4 of the light reception signal E1, and also the light reception signal E2 in each section T1 to T4. The integral values Σf21, Σf22, Σf23, and Σf24 of the frequency relative level distribution are obtained.

Next, for each of the same time interval T1 to T4, the determination unit 15 integrates the frequency distribution integral values Σf11, Σf12, Σf13, Σf14 of the light reception signal E1, and the integration values Σf21Σf22, Σf23, Σf24 of the frequency distribution of the light reception signal E2. Ratio Rf1, Rf2, Rf3, Rf4,
Rf1 = Σf11 / Σf21 Formula (8)
Rf2 = Σf12 / Σf22 Formula (9)
Rf3 = Σf13 / Σf23 Formula (10)
Rf4 = Σf14 / Σf24 Formula (11)
This is taken as the correlation between the frequency distributions of the received light signals E1 and E2.

  In order to determine the correlation between 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 TH1 and the upper limit threshold TH2 based on the ratio Rf1 of the integral values of the first time interval T1. Set the threshold range.

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

When the flame determination threshold range having the lower limit threshold TH1 and the upper limit threshold TH2 is set as described above, the determination unit 15 determines whether or not the following condition is satisfied.
0.9Rf1 ≦ Rf2 ≦ 1.1Rf1 Formula (12)
0.9Rf1 ≦ Rf3 ≦ 1.1Rf1 Formula (13)
0.9Rf1 ≦ Rf4 ≦ 1.1Rf1 Formula (14)
When the determination unit 15 determines that all the conditions of the expressions (12) to (14) are satisfied, that is, the remaining time with respect to the ratio Rf1 of the integral value of the relative level distribution of the frequency in the first time interval T1. When the ratios Rf2 to Rf4 of the integrated values of the relative level distributions of all the frequencies in the sections T2 to T4 are within a predetermined flame determination threshold range, the frequency distributions of the light reception signals E1 and E2 are substantially similar, and the light reception units 12a and 12b. Can be estimated to output the light reception signals E1 and E2 based on the radiation energy from the combustion flame, and is used as one element of the determination of the presence of the flame, for example, allows the flame determination based on the light reception signal E1.

  In addition, when the determination unit 15 determines that at least one of the conditions of the expressions (12) to (14) is not satisfied, that is, the remaining ratio with respect to the ratio Rf1 of the integrated value of the frequency distribution in the first time interval T1. When at least one of the ratios Rf2 to Rf4 of the integral value of the relative level distribution of the frequency in the time interval T2 to T4 is outside the predetermined flame determination threshold range, the light receiving units 12a and 12b receive light by radiation energy from other than the combustion flame. It can be estimated that the signals E1 and E2 are being output, and the flame determination based on the light reception signal E1 is suppressed instead of being one element with a flame.

(Flame judgment processing operation based on correlation of frequency distribution)
FIG. 9 is a flowchart showing the procedure of the processing operation of the determination unit of FIG. 1 for determining the correlation between the frequency distributions of two received light signals.
(Step S11)
First, the determination unit 15 captures the light reception signals E1 and E2 output from the light reception units 12a and 12b through the A / D conversion ports 30a and 30b at a predetermined sampling period 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 reception signals E1 and E2 of the predetermined period T captured in step S11 into four sections T1, T2, T3, and T4, and performs fast Fourier transform on the light reception signals E1 of the sections T1 to T4. The integral values Σf11, Σf12, Σf13, Σf14 of the relative level distribution in the frequency range of 8 Hz or less and the light reception signal E2 are subjected to fast Fourier transform to product integration values Σf21, Σf22, Σf23, Σf24 of the relative level in the frequency range of 8 Hz or less. Is calculated.

  It should be noted that the processing after step S12 is desirably executed when the signal level of the received light signal E1 captured by the determination unit 15 from the A / D conversion port 30a is equal to or higher than a predetermined threshold value.

(Step S13)
Next, the determination unit 15 calculates the ratios Rf1, Rf2, Rf3, and Rf4 of the relative value distributions of the relative level distribution of the frequencies T1 to T4 of the received light signals E1 and E2 calculated in step S12 from the above equations (8) to (11). ).

(Step S14)
Next, the determination unit 15 determines the lower limit threshold THf1 and the upper limit threshold THf2, for example, THf1 = 0.9 · Rf1, THf2 = 1.1 · based on the ratio Rf1 of the integral value of the relative level distribution of the frequency in the first section T1. Set to Rf1.

(Step S15)
Next, the determination unit 15 calculates the ratios Rf2, Rf3, and Rf4 of the relative values of the relative level distributions of the frequencies in the remaining sections T2 to T4 following the first section T1 of the received light signals E1 and E2 calculated in step S13. ) To (14), it is determined whether or not it is within a flame determination threshold range having a lower limit threshold TH1 and an upper limit threshold TH2.

(Steps S16 and S17)
Next, when the determination unit 15 determines in step S16 that all the conditions of the expressions (12) to (14) are satisfied and is within the flame determination threshold range, the frequency distribution of the light reception signals E1 and E2 is determined. The light receiving units 12a and 12b are estimated to be outputting light reception signals E1 and E2 based on the radiation energy from the combustion flame, are determined as one element of flame determination, proceed to step S17, and are based on the light reception signal E1. Allow flame judgment.

(Steps S16 and S18)
On the other hand, the determination unit 15 determines that at least one of the conditions (12) to (14) is not satisfied in step S16, that is, THf1 = 0.9 · Rf1, THf2 = 1.1 · Rf1. If it is determined that the light receiving unit 12a, 12b is outside the flame determination threshold range, it is estimated that the light receiving signals E1, E2 are output by radiation energy other than the combustion flame, and the process proceeds to step S18 to receive the light receiving signal. E1 flame judgment is suppressed.

[Embodiment of 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 apparatus that adds light reception 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 this 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. 2, and the light receiving sensor 16a in FIG. As shown in the equivalent circuit, four light receiving elements 22a composed of a pyroelectric body 25a, a high resistance 29, and an FET 27a are provided, and the drain and gate of each FET 27a are connected in common to the drain terminal D and gate terminal G, respectively. Are individually connected to the source terminals S1 to S4.

  Referring 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 add (receive current) four received light signals as current outputs to add the preamplifier 26a, 26b.

Here, the light receiving outputs from the four light receiving elements 22a are added to the preamplifier 26a after adding the light receiving current after passing through the four pre-filters 24a. There is almost no, and it becomes the current addition of the signal component photoelectrically converted from the radiation energy of a narrow band wavelength band with a central wavelength of about 4.5 μm radiated from the combustion flame by CO ₂ resonance, and lowers the S / N ratio. Rather, it is possible to generate a light reception signal as a light reception current corresponding to approximately four times the light reception output by one light receiving element.

  This also applies to the outputs from the four light receiving elements 22b. Since the light receiving current is added after passing through the four pre-filters 24b and inputted to the preamplifier 26b, random noise components are There is almost no increase due to current addition, and current addition of signal components obtained by photoelectric conversion of radiation energy in a narrow band wavelength band with a center wavelength of approximately 2.3 μm, emitted from the combustion flame, reduces the S / N ratio. Rather, it is possible to generate a light reception signal as a light reception current corresponding to approximately four times the light reception output by one light receiving element.

  As described above, the optical units 12a and 12b add the light reception signals photoelectrically converted by the four light receiving elements 22a and 22b even if the radiation energy radiated from the combustion flame to receive light is weak. No. 12 can output light reception signals E1 and E2 having a sufficient level without lowering the S / N ratio, and can greatly expand the flame detection area.

  The configuration and functions from the preamplifiers 26a and 26b to the determination unit 15 are the same as those in the embodiment shown in FIG.

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

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

  FIG. 12 is a block diagram showing another embodiment of a flame detection apparatus that is installed in a tunnel and monitors a flame.

(Light receiving unit 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 radiate 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 reception signal E1 in which the energy is observed and the light reception signal E2 in which the radiation energy in a narrow band wavelength band having a central wavelength of about 2.3 μm are output, and the A / D conversion ports 30a and 30b provided in the determination unit 15 are output. Each is converted into a digital received light 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 the electric signal. That is, the light receiving unit 12c outputs a light receiving signal E3 obtained by converting radiation energy in a wavelength band of approximately 5.0 μm to 7.0 μm into an electric signal.

  Further, the light receiving unit 12c, following the light receiving sensor 16c, from the light receiving signal output from the light receiving sensor 16c, a pre-filter 24c that passes only a signal component of a predetermined frequency band, and a signal that has passed through the pre-filter 24c. 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 reception signal E3 output from the main amplifier 28c of the light reception unit 12c is converted into a digital light reception signal by the A / D conversion port 30c of the determination unit 15 and is read and used for flame determination processing.

(Configuration of the light receiving sensor 16c)
The light receiving sensor 16c receives an optical wavelength filter 20c that is a long-pass filter composed of a cut-on filter that satisfactorily transmits radiation in a predetermined wavelength band exceeding approximately 5.0 μm, and light transmitted through the optical wavelength filter 20c. The light receiving element 22c having the equivalent circuit of FIG. 3 that is converted into an electrical signal and output, and has a packaged configuration with the same structure as shown in FIG. 2, and the light receiving sensor 16a of the optical units 12a and 12b. , 16b and a common mounting member 48 provided in the main body cover 46, are arranged in a predetermined arrangement close to each other.

(Translucent window 18)
The translucent window 18 is disposed in a predetermined opening provided on the front side which is the monitoring area side of the body cover 46 in which the light receiving sensor 16c is housed together with the light receiving sensors 16a and 16b shown in FIG. The light-receiving elements 22a, 22b, and 22c of the light-receiving sensors 16a, 16b, and 16c are formed of an infrared light-transmitting member such as sapphire glass, and the respective light-receiving limit visual fields are restricted by the edge of the light-transmitting window 18. Thus, detection areas having substantially the same spread angle are set.

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

  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 is composed of a sapphire glass that is a translucent window 18 and a short wave path characteristic 52 that allows good transmission of radiation energy of about 7.0 μm or less, and a long-pass filter that constitutes the optical wavelength filter 20c. High radiation energy in the wavelength band of approximately 5.0 μm to 7.0 μm due to the combination with the transmittance characteristic 62 having the cut-on filter characteristic that transmits the radiation energy in the predetermined wavelength band exceeding approximately 5.0 μm. A wideband bandpass filter having a transmission characteristic 64 that transmits with transmittance is formed.

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

  Next, when the flame integral value ΣE1 is equal to or lower than a preset reference level, the determination unit 15 determines that the received light output corresponding to the flame has not been detected, while the flame integral value ΣE1 is the reference level. If the relative ratio (ΣE1 / ΣE3) exceeds the preset threshold value, the flame is determined to be flame. If it is one element of the flame determination and is below the threshold value, the flame determination is not suppressed by assuming that there is a light reception output from a relatively low temperature radiation source other than a flame such as a human body or a vehicle.

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

[Modification of the present invention]
In the above embodiment, the correlation between the light reception signals is determined by determining the presence or absence of the combustion flame from the ratio of the signal integration values of the divided sections obtained by dividing the light reception signals for a predetermined period into a plurality of time sections. However, the present invention is not limited to the ratio of the signal integral values, and the presence or absence of the combustion flame may be determined from the mutual correlation based on an appropriate value such as the correlation coefficient of each received light signal.

In the above embodiment, as a flame detection device for a tunnel, a correlation by observation of radiation energy in a wavelength band near 4.5 μm and a wavelength band near 2.3 μm, which is a CO ₂ resonance radiation band of a combustion flame, The flame is judged by observing radiation energy in the wavelength band near 5.0 μm and the correlation between the observation of radiation energy in the wavelength band near 4.5 μm and the wavelength band of 2.3 μm, and near 3.8 μm. The presence or absence of flame may be determined by observing radiation energy in the wavelength band.

  Moreover, in addition to the correlation by observation of radiation energy in the wavelength band near 4.5 μm and 2.3 μm, the radiation energy in the wavelength band near 3.8 μm and the wavelength band near 5.0 μm is observed to detect the flame The presence / absence may be determined.

  Further, the present invention includes appropriate modifications that do not impair the object and advantages thereof, and is not limited by the numerical values shown in the above embodiments.

10: Flame detectors 12a, 12b, 12c: Light receiving unit 15: Determination units 16a, 16b, 16c: Light receiving sensor 18: Translucent windows 20a, 20b, 20c: Optical wavelength filters 22a, 22b, 22c: Light receiving element 24a, 24b, 24c: Prefilters 25a, 25b: Pyroelectric bodies 26a, 26b, 26c: Preamplifiers 27a, 27b: FETs
28a, 28b, 28c: main amplifiers 30a, 30b, 30c: A / D conversion ports

Claims (9)

A flame detection device that detects and detects the presence of a combustion flame by observing radiation energy emitted from the combustion flame,
A plurality of light-receiving units that emit light-receiving signals observing different predetermined wavelength bands emitted from the combustion flame,
A determination unit that uses a correlation between the respective light reception signals for a predetermined period of time observed and output by each of the light reception units as one element for determining whether or not there is a combustion flame;
A flame detection apparatus comprising:
In the flame detection device according to claim 1 or 2,
The one light receiving unit is:
An optical wavelength filter that selectively transmits light of a predetermined wavelength band including a CO ₂ resonance radiation band emitted from the combustion flame;
One or a plurality of light receiving elements that output light reception signals based on electrical signals obtained by photoelectrically converting light that has passed through the optical wavelength filter;
A light receiving sensor having
The other light receiving unit is:
An optical wavelength filter that selectively transmits light of a predetermined wavelength band that does not include a CO ₂ resonance radiation band, emitted from a combustion flame;
One or a plurality of light receiving elements that output light reception signals based on electrical signals obtained by photoelectrically converting light that has passed through the optical wavelength filter;
A light receiving sensor having
A flame detection device characterized by that.
In the flame detection apparatus according to claim 2,
Each of the light receiving units further includes a frequency selecting unit that selectively extracts a signal component of a predetermined frequency band from an electrical signal from the light receiving sensor;
An amplification unit that amplifies the signal component output from the frequency selection unit;
A flame detection apparatus comprising:
The flame detection apparatus according to any one of claims 1 to 3, wherein at least two light receiving units are provided.
2. The flame detection apparatus according to claim 1, wherein the determination unit divides the correlation between the light reception signals into a plurality of time intervals and divides the light reception signals for a predetermined period into a plurality of time intervals. A flame detection device that determines the presence or absence of a combustion flame based on a ratio of values.
6. The flame detection apparatus according to claim 5, wherein when the ratio of the signal integral values of the respective divided sections is within a predetermined flame determination threshold range, the determination unit receives light input to the light receiving unit. There is a possibility of radiation from the flame, and it is one element of the judgment of the presence of flame.
The flame detection device according to claim 1, wherein the determination unit includes:
When the light reception signals E1 to Em for a predetermined period output from the plurality of light reception units are divided into time intervals of an integer n of 1 or more, the signal integration of one light reception signal E1 for each of the n division intervals. The ratios R1 to Rn of the values ΣE11 to ΣE1n and the integrated values ΣE11 to ΣEmn of the other received light signals Em corresponding to the same time interval,
R1 to Rn = ΣE11 / ΣEm1 to ΣE1n / ΣEmn
As sought
When all of the signal integral value ratios R2 to Rn in the remaining time interval with respect to the signal integral value ratio R1 in the first time interval are within a predetermined flame determination threshold range, the light input to the light receiving unit is A flame detection device characterized by the possibility of radiation from a flame and being used as one element for determining the presence of a flame.
The flame detection apparatus according to claim 1, wherein the determination unit determines a correlation between the light reception signals by comparing respective frequency distributions obtained from the light reception signals for a predetermined period. Flame detection device.
The flame detection device according to claim 8, wherein the determination unit includes:
The correlation between each received light signal is obtained by dividing each received light signal for a predetermined period into a plurality of time intervals, and obtaining a relative level distribution of a predetermined range of frequencies,
When all the ratios of the integrated values of the frequency relative level distribution between the divided sections are within a predetermined flame determination threshold range, it is determined that the light input to the light receiving unit may be emitted from the flame, and the presence of the flame is determined. A flame detection device characterized by comprising one element.

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