JP7177598B2 - flame detector - Google Patents

Description

The present invention relates to a flame detector that detects the presence or absence of flame by detecting infrared radiation generated by CO2 resonance during flame combustion.

Conventionally, in a flame detection device that detects the presence or absence of flame by detecting the radiation energy generated by flaming combustion, in order to distinguish between a flame and an infrared radiator other than a flame, 2-wavelength type, 3-wavelength type flame detection that detects the presence or absence of a flame by detecting the radiation intensity in a plurality of wavelength bands including the wavelength band due to the resonance radiation of CO2 and detecting the presence or absence of a flame based on the relative ratio of the detected values in the plurality of wavelength bands. Devices and flame detection methods are well known.

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

FIG. 10 is a conceptual diagram showing radiation spectra in the infrared wavelength region of combustion flames 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. 10, in the spectral characteristic 100 of the combustion flame, there is a peak of radiation relative intensity in a wavelength band around 4.5 μm due to CO2 resonance radiation, and a characteristic As for the wavelength, for example, there is a wavelength band in which the radiation relative intensity is low near 5.0 μm on the long wavelength side.

In a two-wavelength type flame detector, for example, radiant energies in a wavelength band near 4.5 μm and a wavelength band near 5.0 μm are selectively transmitted (passed) by narrow-band optical wavelength bandpass filters. Then, the radiation energy is detected by a light receiving sensor, photoelectrically converted, and 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"), and each wavelength band The presence or absence of flame is determined by taking the relative ratio of the received light signal levels and comparing it 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 (about 300° C.) shown in spectral characteristics 104, and spectral It is possible to distinguish between low-temperature radiators such as the human body shown in characteristic 106 and flames.

Further, for example, in addition to the two wavelengths described above, radiation energy in a wavelength band near 2.3 μm, which is on the short wavelength side with respect to the 4.5 μm band, which is the resonant radiation band of CO2, is obtained by the same method as in the two-wavelength method. A three-wavelength type flame detector is also known, which detects flames and determines the presence or absence of flames based on the relative ratios of the received light signals in these three wavelength bands. ing.

In recent years, in order to expand the flame detection area, the number of light receiving units for receiving radiation energy of around 4.5 μm emitted from the flame has been increased, for example, by a multiple of the conventional number, and photoelectric conversion is performed by each light receiving sensor. By adding each received light signal that has been appropriately amplified and processed as necessary, sufficient detection sensitivity can be obtained without impairing the S/N (signal-to-noise ratio) even if the detection area is expanded. I'm trying

JP 2016-128796 A Japanese Patent No. 3357330

However, in a flame detection device in which a plurality of light-receiving units for receiving radiation energy of around 4.5 μm emitted from a flame are provided and the respective light-receiving signals are added to increase the detection sensitivity, a plurality of light-receiving units are conventionally used. Since the field of view of the light receiving sensor provided in is different due to the difference in the arrangement position, there is a single field of view where only a single light receiving sensor is visible, and the radiation energy from the flame existing in the single field of view exists. However, there is a problem that the S/N cannot be improved.

With such a single field of view, for example, there is a risk of malfunction under the influence of relatively nearby disturbing light sources, while distant flames cannot be detected.

The present invention relates to a flame detection device in which a plurality of light receiving units for receiving radiation energy emitted from a flame are provided in order to reliably determine failure of the light receiving unit, and the respective light receiving signals are added to increase the detection sensitivity. To provide a flame detection device that excludes a low S/N visual field area by making a range in which only a single light receiving unit is visible substantially out of the visual field range.

The present invention is a flame detection device that observes radiation energy radiated from a combustion flame to determine and detect the presence or absence of a combustion flame,
a plurality of light-receiving units that output light-receiving signals obtained by observing the same wavelength band of radiation energy;
a judgment unit that judges the presence or absence of flame based on a plurality of light receiving signals output from a plurality of light receiving units;
detecting the difference between the light receiving signals output from the plurality of light receiving units, and if the difference is equal to or less than a predetermined value or less than the predetermined value, permitting the determination of the presence or absence of flame by the determination unit or adoption of the determination result; is a predetermined value or more or exceeds a predetermined value, or if any of the added light receiving signals output from the plurality of light receiving units and each of the light receiving signals substantially match, the judgment unit judges the presence or absence of flames or adopts the judgment result. a judgment control unit that prohibits
characterized by comprising

Further, the determination control unit detects a difference between amplitude integrated values of a plurality of received light signals for a predetermined period, and if the difference of the amplitude integrated values is equal to or less than a predetermined value or falls below a predetermined value, the determination unit determines whether or not there is a flame. Adoption of the determination result is allowed, and determination of the presence or absence of flame by the determination unit or adoption of the determination result is prohibited when the difference between the amplitude integral values is equal to or greater than a predetermined value.

(basic effect)
The present invention is a flame detection device that observes radiation energy radiated from combustion flames to determine the presence or absence of combustion flames and detects the presence of the flames. a light receiving unit, a judging unit that determines the presence or absence of a flame based on a plurality of light receiving signals output from the plurality of light receiving units, and a difference between each light receiving signal output from the plurality of light receiving units. If the difference is equal to or less than the predetermined value or is less than the predetermined value, the judging unit is permitted to judge whether there is flame or adopt the judgment result. and a judgment control section for prohibiting judgment of presence or absence of flame by the judging section or adoption of the judgment result when any of the added light receiving signal and each of the light receiving signals substantially matches,
When a plurality of light-receiving units are provided, by substantially eliminating a single visual field range in which only a single light-receiving unit is visible due to differences in light-receiving positions, unnecessary widening of the field of view with a low S/N ratio is suppressed. For example, it is possible to avoid malfunction due to a disturbance light source existing in such an unnecessary visual field range. That is, the effective field of view can be narrowed down to a high S/N range.

Further , the plurality of light receiving units are arranged so as to have an effective visual field range in which the respective visual field ranges overlap and a single visual field range in which the respective visual field ranges do not overlap. Or, by allowing the adoption of the judgment result in the effective visual field range and prohibiting it in the single visual field range, it is possible to judge the radiation energy from the single visual field range where the detection sensitivity cannot be improved by improving the S/N. By prohibiting the judgment of the presence or absence of flame by the judging section by the control section, it is possible to substantially detect the flame with the single visual field range outside the effective visual field range.

(Effect of judgment control based on difference in integrated value of multiple received light signals)
Further, the determination control section detects a difference in the amplitude integrated values of a plurality of received light signals for a predetermined period, and if the difference in the amplitude integrated values is equal to or less than a predetermined value or falls below a predetermined value, the determination section determines whether or not there is a flame. However, if the difference in the integrated amplitude value is equal to or greater than a predetermined value, the judgment unit is prohibited from judging the presence or absence of flame or adopting the judgment result. It is possible to control whether to permit or prohibit the determination of the presence or absence of flame or the adoption of the determination result.

1 is a block diagram illustrating an embodiment of a flame detection device; FIG. Explanatory diagram showing the external appearance of the flame detection device Explanatory drawing showing the structure of the light receiving sensor A circuit diagram showing an equivalent circuit of the light receiving sensor in FIG. Explanatory diagram showing the arrangement of light receiving sensors and the visual field range A signal waveform diagram showing a received light signal output from the light receiving unit of FIG. 1 when radiation energy radiated from a combustion flame is observed. Explanatory diagram showing the frequency distribution of the added received light signal obtained from the light receiving unit of FIG. 1 when the radiation energy radiated from the combustion flame is observed. 1 is a block diagram showing an embodiment of a two-wavelength flame detection device; FIG. FIG. 9 is a characteristic diagram showing the transmittance at each wavelength of the optical wavelength filter and translucent window applied to the embodiment of FIG. Characteristic diagram showing the radiation spectrum of a combustion flame and other typical radiators

[Flame detector]
(Equipment overview)
FIG. 1 is a block diagram showing an embodiment of a flame detection device. As shown in FIG. 1, the flame detection device 10 of this embodiment comprises two sets of light receiving units 12a and 12b, and a determination control section 36 and a determination section 38 provided in an MPU (microcomputer unit) 15. As shown in FIG.

The light-receiving units 12a and 12b are for observing the radiation energy emitted from the combustion flame existing in the monitoring area. It observes and photoelectrically converts the radiation energy in the wavelength band to output received light signals E1 and E2.

The light receiving units 12a and 12b are provided with light receiving sensors 22a and 22b, front filters 24a and 24b, preamplifiers 26a and 26b, and main amplifiers 28a and 28b. The signal is further amplified by the final stage amplifiers 30a and 30b, converted into a digital received light signal by the A/D conversion ports 35a and 35b of the MPU 15, and taken in.

The light receiving signals E1 and E2 from the light receiving units 12a and 12b are added and amplified by the adder 32 and output to the MPU 15 as an added light receiving signal E3. be The determination control unit 36 detects the difference ΔE between the light receiving signals E1 and E2 output from the light receiving units 12a and 12b, and when the difference ΔE is less than or equal to a predetermined value, the determination unit 38 determines the presence or absence of flame. Judgment is permitted, and the judging unit 38 is prohibited from judging the presence or absence of flame when the difference ΔE exceeds a predetermined value, or the judgment result is not adopted (for example, the judgment result indicating the presence of flame is not output to the outside). can be

The difference .DELTA.E is calculated, for example, as the difference between the digital light receiving signal based on the light receiving signal E1 and the digital light receiving signals E1' and E2' based on the light receiving signal E2, each of which is integrated over a predetermined period.

The judging section 38 judges and detects the presence or absence of the combustion flame based on the added received light signal E3 output from the adder 32 .

(Appearance and sensor unit)
FIG. 2 is an explanatory diagram showing the appearance of the flame detection device. As shown in FIG. 2, the flame detection device 10 is provided with a translucent window 18 on the lower surface of a cover 52 provided at the bottom of a main body 50 attached to a detector base on the ceiling surface. The light receiving sensors 16a and 16b of the optical units 12a and 12b shown in FIG. Also, a test light source transmissive window 25 containing an individual test lamp as an external test light source is provided at a position where the light receiving element inside can be seen in the vicinity of the translucent window 18 .

(Configuration of Light Receiving Units 12a and 12b)
In the light-receiving units 12a and 12b shown in FIG. 1, the light-receiving sensors 16a and 16b convert radiation energy having an infrared wavelength band with a center wavelength of approximately 4.5 μm, which is emitted from the combustion flame accompanying CO2 resonance, into electrical signals. The pre-filters 24a and 24b selectively pass signal components in a predetermined frequency band corresponding to the fluctuation frequency of the flame from the received light signals output from the light receiving sensors 16a and 16b, and the preamplifier 26a. , 26b amplifies the signal components passed through the pre-filters 24a, 24b in the first stage, and the main amplifiers 28a, 28b and the final stage amplifiers 30a, 30b amplify them to a signal level suitable for flame determination processing, and output the received light signals E1, E2. Output.

Here, the light-receiving sensors 16a and 16b are provided with a light-transmitting window 18, optical wavelength filters 20a and 20b, and light-receiving elements 22a and 22b, which are shared by infrared light-transmitting members such as sapphire glass.

The received light signals E1 and E2 output through the final stage amplifiers 30a and 30b are converted into digital received light signals by A/D conversion ports 35a and 35b provided in the MPU 15 and read. Judgment permission or prohibition is determined, and if permitted, permission is instructed to the determination unit 38, and the presence or absence of a fire is determined.

The light receiving signals E1 and E2 output from the light receiving units 12a and 12b are added by the adder 32, and the added light receiving signal E3 from the adder 32 is converted into a digital light receiving signal by the A/D conversion port 35c provided in the MPU 15. , and the judging unit 38, which has received an instruction to allow the judgment of the presence or absence of flame from the judgment control unit 36, executes the judgment of the presence or absence of flame. Each configuration will be specifically described below.

(Light receiving sensors 16a, 16b)
FIG. 3 is an explanatory diagram showing a schematic configuration of the light receiving sensor, and FIG. 4 is a circuit diagram showing an equivalent circuit of the light receiving sensor of FIG.

As shown in FIG. 3, the light receiving sensors 16a and 16b are provided with pyroelectric bodies 45a and 45b supported and arranged on the surfaces of the substrates 40a and 40b, and provided with light receiving electrodes 25a and 25b. light receiving element portions 22a and 22b provided with FETs 27 disposed on the sides; terminals 42a and 42b provided through the base portions 38a and 38b for supporting the substrates 40a and 40b on the base portions 38a and 38b; It has a packaged structure comprising cover members 44a and 44b provided with optical wavelength filters 20a and 20b for selectively transmitting infrared rays centered at 4.5 μm in front of the light receiving element portions 22a and 22b.

The equivalent circuit of the light receiving element portions 22a and 22b is, as shown in FIG. , and the drain and source of FET 27 are connected to drain terminal D and source terminal S, respectively. Each terminal is led out to the outside of the package as a terminal 42a in FIG. 4 (although only two terminals are shown in FIG. 4, there are corresponding terminals).

Here, the optical wavelength filter 20a can be formed, for example, on a substrate of silicon, germanium, sapphire, or the like by a known method.

(translucent window 18)
As shown in FIGS. 2 and 3, the translucent window 18 is located on the upper side corresponding to the monitoring area side of the sensor unit of FIG. 4 housing the light receiving sensors 16a and 16b. It is arranged in a predetermined opening provided on the front side of the device, and is made of, for example, an infrared transmissive member such as sapphire glass, as described above. For this reason, in the light receiving element portions 22a and 22b, a detection area having a predetermined spread angle is set by restricting the light receiving limit visual field by the edge portion of the translucent window 18. FIG. In this embodiment, the translucent window 18 will be described as being included in the light-receiving sensors 16a and 16b as a shared member.

(Field of view range of light receiving sensors 16a and 16b)
FIG. 5 is an explanatory diagram showing the arrangement of the light receiving sensors and the visual field range. As shown in FIG. 5, the light-receiving sensors 16a and 16b, which are adjacently arranged on the circuit board 48, are arranged inside the translucent window 18, and are spaced apart by a predetermined distance d indicated by the distance between the axes. placed in different locations.

For this reason, the detection area of the light receiving sensors 16a and 16b is a visual field range having a predetermined spread angle θ. The area 64 between the limit line 62 of the is a single field of view visible only from the light receiving sensor 16a.

A region 66 between the lower visual field limit line 60 of the light receiving sensor 16a and the lower visual field limit line 62 of the light receiving sensor 16b is a single visual field view visible only from the light receiving sensor 16b.

Therefore, the radiation energy from the flame existing in the single visual field range 64 is received only by the light receiving sensor 16a, and the light receiving signal E1 from the light receiving unit 12a in FIG. becomes zero level, the added light receiving signal E3 from the adder 32 is the same as the light receiving signal E1, and the detection sensitivity cannot be increased by improving the S/N.

Radiation energy from flames present in the single visual field range 66 is received only by the light receiving sensor 16b, and the light receiving signal E2 from the light receiving unit 12b in FIG. becomes zero level, the added light receiving signal E3 from the adder 32 is the same as the light receiving signal E2, and the detection sensitivity cannot be increased by improving the S/N.

For the radiation energy from the single visual field ranges 64 and 66 for which the detection sensitivity cannot be improved by improving the S/N, in the present embodiment, the determination control unit 36 determines whether or not the flame exists by the determination unit 38. By prohibiting , it is possible to detect flames in a substantially single field of view 64, 66 outside the effective field of view.

(Pre-filter 24a)
The pre-filter 24a functions as a frequency selection section, and is, for example, an active filter that passes only signal components in a specific frequency band used for flame determination processing from the light receiving signal output from the light receiving element section 22a of the light receiving sensor 16a. It outputs a received light signal containing a signal component of a specific frequency band to the subsequent preamplifier 26a. Such a frequency selection filter is not only used as a pre-filter, but is also appropriately arranged from the preamplifier to the final stage amplifier so that the signal is amplified while selecting (extracting) the frequency.

(Preamplifiers 26a, 26b and main amplifiers 28a, 28b)
The preamplifiers 26a and 26b amplify the received light signals input via the pre-filters 24a and 24b at a predetermined amplification factor in the first stage, and the main amplifiers 28a and 28b convert the received light signals from the preamplifiers 26a and 26b into the received light signals. Output as E1 and E2. Final-stage amplifiers 30a and 30b adjust and amplify the received light signals E1 and E2 to signal levels suitable for flame determination processing, and output them to A/D conversion ports 35a and 35b of MPU 15 as E1' and E2'.

(summing amplifier 32)
The summing amplifier 32 inputs and adds the received light signals E1 and E2 from the main amplifiers 28a and 28b of the light receiving units 12a and 12b, and then adds a voltage level suitable for the input of the AD conversion port 35c provided in the subsequent MPU 15. It is converted into a signal E3 and output.

(A/D conversion ports 35a, 35b, 35c)
A/D conversion ports 35a, 35b, and 35c are A/D converters provided as input ports of the MPU 15, and light reception signals (analog light reception signals) E1 and E2 are processed by the final stage amplifiers 30a and 30b. and the addition signal E3 are converted into digital signals and read.

(Determination control unit 36)
FIG. 6 is a signal waveform diagram showing the received light signal output from the light receiving unit of FIG. 1 when the radiation energy radiated from the combustion flame is observed. FIG. , E1′-derived digital signal waveforms, and FIG. 6B shows a digital signal waveform derived from E2′ from the A/D conversion port 35b.

In this embodiment, the A/D conversion is performed by sampling the received light signal at 64 Hz, that is, 64 points of digital data are obtained per second for each signal. For the sake of simplicity, the signals after A/D conversion are hereinafter referred to as light reception signals E1', E2', and E3 as before conversion.

The judgment control section 36 detects the difference between the light receiving signals E1' and E2' shown in FIG. 6 output from the light receiving units 12a and 12b of FIG. Detection of the difference by the judgment control unit 36 is performed by taking the light reception signals E1′ and E2′ shown in FIG. Integral values ΣE1′ and ΣE2′, which are the absolute values of the difference from the amplitude of the
ΔE=ΣE1′−ΣE2′
Calculate as

Subsequently, the judgment control unit 36 allows the judging unit 38 to judge the presence or absence of flame when the absolute value of the difference ΔE of the integral values is less than or equal to a predetermined value. If the absolute value is greater than or equal to the predetermined value, control is performed to prohibit the judgment unit 38 from judging the presence or absence of flame.

Therefore, when the light-receiving units 12a and 12b are operating normally, the absolute value of the difference ΔE between the integrated values of the light-receiving signals E1′ and E2′ is equal to or less than a predetermined value or less than a predetermined value. Judgment of the presence or absence of flame by the judging section 38 is permitted.

On the other hand, if one of the light receiving units 12a and 12b fails, the difference between the light receiving signals E1' and E2' increases, and the absolute value of the difference ΔE between the integrated values of the light receiving signals E1' and E2' is is greater than or equal to the predetermined value, the judgment control section 36 prohibits the judgment section 38 from judging the presence or absence of flame. Alternatively, if the absolute value of ΔE, which is the difference between the integral values, is equal to or greater than a predetermined value, the judgment unit 38 does not adopt the judgment result (for example, even if the judgment result indicates that there is flame, it is not output to the outside). You can do it.

Further, the judgment control unit 36 inhibits judgment of the presence or absence of flame by the judging unit 38 when the absolute value of the difference ΔE between the integrated values of the light reception signals E1′ and E2′ is equal to or greater than a predetermined value or exceeds a prescribed value. 12a and 12b is highly likely to be caused by the failure, the judgment control unit 36 drives the internal test light source provided in the device to perform a test in which the light receiving sensors 16a and 16b are irradiated with the test light. At this time, the fault is detected from the light receiving signals E1 and E2 output from the light receiving units 12a and 12b, and control is performed to determine the failure.

Furthermore, when radiation energy is received from either of the single visual field ranges 64 and 66 shown in FIG. Since the absolute value of the difference ΔE is greater than or equal to the predetermined value, the judgment control section 36 prohibits the judgment section 38 from judging the presence or absence of flame, thereby substantially detecting flame detection in the single visual field ranges 64 and 66. outside the field of view of the device 10.

(Determination unit 38)
The determination unit 38 generates an added light receiving signal E3 obtained by adding the light receiving signals E1' and E2' shown in FIG. An integral value ΣE3, which is the absolute value of the difference from the amplitude on the negative side, is obtained.

Next, when the integral value ΣE3 is equal to or lower than the preset reference level, the judgment section 38 judges that the received light output corresponding to flame is not detected, while the integral value ΣE3 exceeds the reference level. If it is, it is regarded as the first element of flame presence determination.

Further, the judging section 38 fast-Fourier-transforms the added received light signal E3 every two seconds (128 data) and analyzes the result. , a composite flame presence/absence determination based on the first element and the second element.

FIG. 7 is an explanatory diagram showing the frequency distribution of the added received light signal E3 obtained from the light receiving unit of FIG. 1 when the radiation energy radiated from the combustion flame is observed. The determination unit 38 performs a fast Fourier transform on the added received light signal E3 obtained by adding the received light signals E1' and E2' shown in FIG. 6 every T=2 seconds (128 data) to obtain the frequency distribution shown in FIG.

As shown in FIG. 7, when the radiation energy radiated from the combustion flame is observed on the frequency axis, a frequency characteristic FL showing a higher output level on the lower frequency side than about 8 Hz is obtained. A main component exists in the frequency band FL up to 8 Hz, and a high frequency band FH exceeding 8 Hz, for example up to 16 Hz, exhibits a low level. Such distribution characteristics are characteristic of the signal when observing a flame.

For this reason, flame determination based on the frequency distribution of the added light receiving signal E3 can be performed by, for example, the integrated value ΣFL of the frequency distribution FL on the low frequency side in the range up to 8 Hz and the integrated value ΣFH on the high frequency side in the range of over 8 Hz to 16 Hz. is obtained, and when the ratio ΣFL/ΣFH of both integrated values is equal to or less than a preset threshold value, it is determined that the received light output corresponding to flame has not been detected, while ΣFL/ΣFH exceeds the threshold value. In case of fire, it is the second factor for determination of presence of flame.

Then, when both the first element and the second element of the flame presence determination are established and, for example, this is repeated a predetermined number of times, the determination unit 38 determines that the flame presence is present and outputs a fire detection signal to the outside. .

[Dual Wavelength Flame Detector]
(Light receiving units 12a and 12b)
FIG. 8 is a block diagram showing an embodiment of a flame detection device as a two-wavelength system. As shown in FIG. 8, the two-wavelength flame detector 10 according to the present embodiment observes radiation energy in a narrow wavelength band with a central wavelength of approximately 4.5 μm, which is emitted from a combustion flame by CO2 resonance. In addition to two sets of light receiving units 12a and 12b that output light receiving signals E1 and E2 by photoelectric conversion, a light receiving signal E4 newly converted from radiation energy in a wavelength band of approximately 5.0 μm to 7.0 μm into an electric signal is output. A light receiving unit 12c is provided.

The light receiving units 12a and 12b are the same as those in the embodiment of FIG. E2 is output.

E1′, E2′, E4′ based on the light receiving signals from the light receiving units 12a, 12b, 12c and the added light receiving signal E3 from the adder 32 are supplied to the A/D conversion ports 35a, 35b, 35d, 35c provided in the MPU 15, respectively. are converted into digital received light signals and taken in.

A judgment control unit 36 provided in the MPU 15 is the same as that in the embodiment of FIG. is below a predetermined value or below a predetermined value, the determination unit 38 is allowed to determine whether there is a flame, and when the absolute value of the difference ΔE is a predetermined value or more or exceeds a predetermined value, the determination unit 38 is allowed to determine whether there is a flame. restrict. Here, as in the single-wavelength embodiment of FIG. 1, if the absolute value of the difference ΔE of the integrated values is equal to or greater than a predetermined value, the determination result is not adopted by the determination unit 38. Also good.

(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 units 12a and 12b output light receiving signals E1 and E2 obtained by converting radiation energy in a narrow band of wavelengths with a center wavelength of about 4.5 μm, which is radiated from the combustion flame by CO2 resonance, into electrical signals. On the other hand, the light-receiving unit 12c in this embodiment outputs a light-receiving signal E4 obtained by converting radiation energy in an infrared wavelength band of approximately 5.0 μm to 7.0 μm into an electric signal.

Further, the light-receiving unit 12c is connected to the light-receiving sensor 16c, and from the light-receiving signal output from the light-receiving sensor 16c, the pre-filter 24c that passes only the signal component of a predetermined frequency band, and the signal that has passed through the pre-filter 24c. It is composed of a preamplifier 26c that amplifies the component in the first stage and a main amplifier 28c that amplifies the output from the preamplifier 26c. A light receiving signal E4 output from the main amplifier 28c of the light receiving unit 12c is input to the A/D conversion port 35d of the MPU 15 via the final stage amplifier 30c, converted into a digital light receiving signal, read, and subjected to flame determination processing. used for

(Configuration of light receiving sensor 16c)
The light receiving sensor 16c receives light transmitted through 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 approximately 5.0 μm, and the optical wavelength filter 20c. A light receiving element portion 22c having an equivalent circuit similar to that of the light receiving element portion 22a shown in FIG. do.

(Wavelength transmission characteristics of light receiving sensors 16a to 16c)
FIG. 9 is a characteristic diagram showing the transmittance at each wavelength of the optical wavelength filter and translucent window applied to the embodiment of FIG.

As shown in FIG. 9, the sapphire glass, which is the translucent window 18 in FIG. A characteristic 70 is obtained. A band-pass filter having a center wavelength around 4.5 μm, which constitutes the optical wavelength filters 20a and 20b, provides a transmittance characteristic 72 that transmits radiation energy in a wavelength band around the center wavelength. These combinations form a narrowband bandpass filter with composite characteristic 74 .

On the other hand, the combination of the transmittance characteristic 70 of the sapphire glass that is the translucent window 18 and the transmittance characteristic 76 of the long-pass filter that constitutes the optical wavelength filter 20c allows the radiation energy in the wavelength band of approximately 5.0 μm to 7.0 μm. A wideband bandpass filter is constructed with a synthesis characteristic 78 that transmits the .

Here, the field of view of the light-receiving sensor 16c, which detects a band of 5.0 to 7.0 μm, is designed to substantially include the effective field of view.

(Flame judgment by two-wavelength method)
When receiving a control instruction to allow the determination of the presence or absence of flame by the determination control unit 36, the determination unit 38 provided in the MPU 15 receives light during the period corresponding to the received light signals E1′ and E2′ that are the basis of the determination of permission. The signal amplitude (the absolute value of the difference from the reference potential) is time-integrated for each of the signals E3 and E4' to calculate integral values ΣE3 and ΣE4'. Here, the integral values ΣE3 and ΣE4′ are distinguished as a flame integral value ΣE3 and a non-flame integral value ΣE4′ for convenience.

Next, when the integrated flame value ΣE3 is equal to or lower than the preset reference level, the determination unit 15 determines that the received light output corresponding to the flame is not detected. is calculated, the relative ratio ΣE3/ΣE4' to the non-flame integrated value ΣE4' is calculated, and if the relative ratio (ΣE3/ΣE4') exceeds a preset threshold, it is determined as a flame. If it is less than the threshold value, it is assumed that there is a received light output from a relatively low-temperature radiation source other than a flame, such as a human body, and flame judgment is suppressed and not performed.

In the embodiment of FIG. 1, the first factor for flame determination is established when ΣE3 exceeds the reference level (threshold value). ) and the relative ratio ΣE3/ΣE4′ exceeds another threshold.

Further, when the determination unit 38 receives a control instruction to allow the determination of the presence or absence of flame by the determination control unit 36, as shown in the embodiment of FIG. When ΣFH exceeds the reference level, it is taken as the second factor for flame judgment.

Then, when both the first element and the second element for judging the existence of flame are satisfied and, for example, the judgment continues a predetermined number of times, the judging section 38 confirms the judgment that there is flame and outputs a fire detection signal to the outside. .

[Modification of the present invention]
In the above embodiment, the light receiving signals E1 and E2 from the light receiving units 12a and 12b are added by the adder 32, and the added light receiving signal E3 is obtained by the judging section 38 as to whether or not there is a flame. However, the present invention is not limited to this. For example, the light receiving signals E1' and E2' from the light receiving units 12a and 12b may be averaged, and the judging section 38 may judge the presence or absence of flame based on the average light receiving signal.

In the above-described embodiment, as a two-wavelength flame detector, radiation energies are observed in a wavelength band near 4.5 μm and a wavelength band near 5.0 μm, which are resonance radiation bands of CO2 of a combustion flame. A flame is determined, but the flame may be determined by observing each radiation energy in a wavelength band near 4.5 μm and a wavelength band near 2.3 μm.

Detecting radiation energy in a wavelength band near 2.3 μm, for example, in a wavelength band near 5.0 μm on the short wavelength side of the 4.5 μm band, which is the resonance radiation band of CO2 of the combustion flame, A three-wavelength type flame detection device may be used in which the presence of flame is judged based on the fact that the relative ratios of the received light signals in these three wavelength bands follow the characteristics of the radiation from the flame.

Moreover, 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 detectors 12a, 12b, 12c: Light receiving unit 15: MPU
16a, 16b, 16c: light receiving sensor 18: translucent windows 20a, 20b, 20d: optical wavelength filters 22a, 22b, 22c: light receiving element portions 24a, 24b, 24c: front filters 26a, 26b, 26c: preamplifier 27: FETs
28a, 28b, 28c: Main amplifiers 30a, 30b, 30c: Final amplifier 32: Adders 35a, 35b, 35c, 35d: A/D conversion port 36: Judgment control section 38: Judgment section
45a, 45b: pyroelectric bodies

Claims (1)

A flame detection device that detects the presence or absence of a combustion flame by observing radiation energy emitted from the combustion flame,
a plurality of light-receiving units that output light-receiving signals obtained by observing the same wavelength band of radiation energy;
a determination unit that determines the presence or absence of flame based on the plurality of light receiving signals output from the plurality of light receiving units;
detecting the difference between the light receiving signals output from the plurality of light receiving units, and if the difference is equal to or less than a predetermined value or less than the predetermined value, the determination unit determines whether or not the flame exists or adopts the determination result; If the difference is greater than or equal to the predetermined value or exceeds the predetermined value, or if any of the added light receiving signals output from the plurality of light receiving units substantially matches the respective light receiving signals, the determination unit A judgment control unit that prohibits the judgment of the presence or absence of flames or the adoption of judgment results by
A flame detection device comprising:

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