JP5797992B2 - Flame detector and flame judgment method - Google Patents

Description

The present invention relates to a flame detector and a flame determination method for detecting and reporting a flame associated with a fire.

Conventionally, in a flame detector that detects the presence or absence of flame by detecting infrared radiation generated by flaming combustion, it is generated at the time of flaming combustion in order to distinguish between flames and infrared radiators other than flame. Two-wavelength, three-wavelength, etc. flames that detect radiation intensities in a plurality of wavelength bands including a wavelength band due to 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.

The detection principle of the conventional two-wavelength or three-wavelength flame detector is as follows. In the combustion flame, there is a peak of radiation intensity in the wavelength band near 4.5 μm due to the resonance radiation of CO ₂ , and the characteristic wavelength existing in the vicinity of this peak wavelength is, for example, 3 on the short wavelength side. A wavelength band with low radiation intensity exists in the vicinity of .8 μm and 5.1 μm on the long wavelength side.

It is known that a flame as a radiation source has a peak of infrared radiation intensity in the 4.3 μm band due to CO ₂ resonance radiation. However, the flame detector detects the radiant energy from the flame at a position away from the radiation source. For this reason, when actually measured at the place where the flame detector is installed, the radiation intensity is around 4.5 μm. It has been empirically shown that the peak appears. Therefore, hereinafter, unless otherwise specified, the CO ₂ resonance radiation band refers to the 4.5 μm band.

  For this reason, in a two-wavelength flame detector, each radiant energy in a wavelength band near 4.5 μm and a wavelength band near 3.8 μm, for example, is selectively transmitted (passed) by a narrow-band optical wavelength bandpass filter. And detecting the radiant energy by the light receiving element and converting it into a corresponding electric signal, taking the relative ratio of the respective detection outputs, and comparing with a predetermined threshold value to determine a flame. This makes it possible to distinguish from infrared radiators other than flames, for example, high-temperature radiators such as sunlight, relatively low-temperature radiators of about 300 ° C., low-temperature radiators such as human bodies, and the like.

In addition, in the case of a three-wavelength flame detector, in addition to the two wavelengths described above, the radiation energy in the long wavelength side of the 4.5 μm band, which is the resonance radiation band of CO ₂ , for example, in the wavelength band near 5.1 μm. Is detected by the same method as the above-mentioned two-wavelength type, and the presence or absence of flame is determined by the relative ratio of the detection outputs in these three wavelength bands. With such a flame detection method, infrared radiation other than flame and flame is emitted. The identification performance with the body can be further improved.

Japanese Patent Publication No.55-33119 Japanese Patent Publication No.59-34252

  However, when such a conventional flame detector is installed in a factory or the like, there is a problem that the flame detector malfunctions due to arc welding work.

This is because the arc welding light includes infrared rays in the vicinity of 4.5 μm due to resonance emission of CO ₂ generated during flammable combustion. For example, the covering of the welding rod used for arc welding contains organic substances such as starch as an ingredient, and in addition to burning the organic substances, infrared rays in the vicinity of 4.5 μm are emitted by resonance radiation of CO ₂ , It is also emitted by black body radiation from the welded part that is at a high temperature, and it is difficult to distinguish with conventional flame detectors, and there is a problem that malfunction occurs due to arc welding light.

In order to solve this problem, the applicant of the present application detects the first received light signal by light having a narrow band wavelength centered around 4.5 μm, which is radiated by CO ₂ resonance generated during flammable combustion. In addition, a second received light signal is detected by near infrared light in the wavelength band near 0.7 to 1.0 μm radiated by arc welding light, and based on the relative ratio of the first received light signal and the second received light signal. A flame detector that distinguishes between a flame and a radiation source of arc welding light is proposed.

  However, even in such a flame detector, there is a possibility that the arc welding light may be mistakenly recognized as a flame due to a fire depending on the timing, and further improvement by investigating the cause is required.

The present invention relates to a flame detector and a flame determination method capable of improving the distinguishability between a flame and arc welding light and reliably determining the presence of a flame without causing malfunction due to the arc welding light and issuing a fire. The purpose is to provide.

(Flame detector)
The present invention provides a flame detector,
Narrowband wavelength light centered around 4.5 μm emitted by CO ₂ resonance generated during flammable combustion is selectively transmitted and converted into an electrical signal, and a signal component of a predetermined frequency is converted from the electrical signal. A first detector for selectively extracting and outputting a first light receiving signal;
A second detector that selectively transmits near-infrared light in a predetermined wavelength band, converts the light into an electrical signal, selectively extracts a signal component of a predetermined frequency from the electrical signal, and outputs a second received light signal;
A correction unit that corrects a temporal timing shift between the first light reception signal from the first detection unit and the second light reception signal from the second detection unit that are detected when the arc welding operation is performed ;
A flame determination unit that discriminates the presence of the flame and the radiation source of the arc welding light based on the first light reception signal and the second light reception signal in which the temporal timing shift is corrected by the correction unit;
An alarm circuit that outputs a fire signal when the flame determination unit determines the presence of a flame,
It is provided with.

  Here, the correction unit delays the second light reception signal from the second detection unit by a predetermined time and suppresses a time shift from the first light reception signal.

The first detector is
A first optical filter that selectively transmits light having a narrow band wavelength centered around 4.5 μm, which is emitted by CO 2 resonance generated during flammable combustion;
A first light receiving element that receives light transmitted through the first optical filter, converts the light into an electrical signal, and outputs the electrical signal;
A first frequency extracting unit that selectively extracts a signal component of a predetermined frequency from the output of the first light receiving element and outputs a first light receiving signal;
With
The second detector
A second optical filter that transmits near-infrared light in a predetermined wavelength band;
A second light receiving element that receives light transmitted through the second optical filter, converts the light into an electrical signal, and outputs the electrical signal;
A second frequency extracting section for selectively extracting a signal component of a predetermined frequency from the output of the second light receiving element and outputting a second light receiving signal;
Is provided.

  The second optical filter transmits near-infrared light having a wavelength band in the vicinity of 0.7 μm to 1.0 μm (near 700 nm to 1000 nm).

  The second optical filter and the second light receiving element are a phototransistor or a photodiode that includes a transmission window that transmits light in the near infrared band and has a peak wavelength at a predetermined wavelength in the near infrared band.

  The flame determination unit obtains a ratio K = e1 / e2 between the first light reception signal e1 and the second light reception signal e2, and determines the presence of flame when the ratio is equal to or greater than a predetermined determination threshold value Kth.

The flame judgment part
When the second light reception signal e2 is less than the predetermined light reception threshold eth, the ratio K = e1 / e2 between the first light reception signal e1 and the second light reception signal e2 is obtained.
When the second light reception signal e2 is equal to or greater than a predetermined light reception threshold eth, a ratio K = e1 / c between the first light reception signal e1 and a predetermined constant c is obtained.
The presence of a flame is determined when the ratio is equal to or greater than a predetermined determination threshold Kth.

The flame detector of the present invention further includes:
Only light of a narrow band wavelength centered on a predetermined wavelength adjacent to a wavelength band centered on 4.5 μm emitted by CO ₂ resonance generated during flammable combustion is selectively transmitted and converted into an electrical signal. A third detector for selectively extracting a signal component of a predetermined frequency from the electrical signal;
Provided,
The flame determination unit determines the presence of the flame and the radiation source of the arc welding light based on the first light reception signal, the second light reception signal, and the third light reception signal from the first detection unit, the second detection unit, and the third detection unit. Identify and judge.

The third detector
A third optical filter that selectively transmits light having a narrowband wavelength centered on a predetermined wavelength adjacent to a wavelength band centered around 4.5 μm;
A third light receiving element that receives the light transmitted through the third optical filter, converts the light into an electrical signal, and outputs the electrical signal;
A third frequency extracting section for selectively extracting a signal component of a predetermined frequency from the output of the third light receiving element and outputting a third light receiving signal;
Is provided.

  The third optical filter selectively transmits only light having a narrow band wavelength centered around 3.8 μm or 5.1 μm adjacent to the transmission wavelength band near 4.5 μm of the first optical filter.

The flame judgment part
A first ratio K1 = e1 / e2 between the first light reception signal e1 and the second light reception signal e2 is obtained, and a second ratio K2 = e1 / e3 between the first light reception signal e1 and the third light reception signal e3 is obtained,
The presence of flame is determined when the first ratio K1 is equal to or greater than a predetermined first determination threshold value Kth1 and the second ratio K2 is equal to or greater than a predetermined second determination threshold value Kth2.

The flame judgment part
When the second light reception signal e2 is less than the predetermined light reception threshold eth, a first ratio K1 = e1 / e2 between the first light reception signal e1 and the second light reception signal e2 is obtained and the first light reception signal e1 and the third light reception signal are obtained. A second ratio K2 = e1 / e3 with e3 is obtained,
When the second light reception signal e2 is equal to or greater than the predetermined light reception threshold eth, a first ratio K1 = e1 / c between the first light reception signal e1 and the predetermined constant c is obtained and the first light reception signal e1 and the third light reception signal e3. The second ratio K2 = e1 / e3 is determined, and the presence of flame is determined when the first ratio K1 is equal to or greater than a predetermined first determination threshold value Kth1 and the second ratio K2 is equal to or greater than a predetermined second determination threshold value Kth2. .

  The flame determination unit determines the presence of a flame based on an integrated signal obtained by integrating the first signal to the third light reception signal.

(Flame judgment method)
The present invention provides a flame determination method,
The first detector selectively transmits light having a narrow band wavelength centered around 4.5 μm, which is radiated by CO 2 resonance generated during flammable combustion, and converts the light into an electrical signal. Select and extract the frequency signal component and output the first received light signal,
The second detector selectively transmits near-infrared light in a predetermined wavelength band and converts it into an electrical signal, selectively extracts a signal component of a predetermined frequency from the electrical signal, and outputs a second received light signal.
The correction unit corrects a temporal timing shift between the first light reception signal from the first detection unit and the second light reception signal from the second detection unit detected when the arc welding operation is performed ,
The flame determination unit discriminates and determines the presence of the flame and the radiation source of the arc welding light based on the first light reception signal and the second light reception signal in which the temporal timing shift is corrected by the correction unit. .

Other features of the flame determination method according to the present invention are basically the same as those of the flame detector described above.

According to the flame detector of the present invention, the first light reception signal (4.5 μm light reception signal) is emitted by light having a narrow band wavelength centered around 4.5 μm, which is radiated by CO ₂ resonance generated during flammable combustion. And detecting a second light reception signal (near infrared light reception signal) by near infrared light in a wavelength band near 0.7 to 1.0 μm radiated by arc welding light (two-wavelength method), Since the presence of the flame and the radiation source of the arc welding light are identified and determined based on the first light receiving signal and the second light receiving signal, when installed in a factory or the like where arc welding work is performed, the arc welding light does not malfunction. Also, it does not malfunction even with sunlight, incandescent light bulbs, halogen lamps, etc., and it can reliably detect and notify the fire flames.

  In this case, depending on the timing, the arc welding light may be misjudged as a flame due to fire, and when the cause was investigated, a narrow band centered around 4.5 μm detected when arc welding work was performed. A first light reception signal (4.5 μm light reception signal) based on light of a wavelength and a second light reception signal (near infrared light) emitted by arc welding light and near infrared light in a wavelength band near 0.7 to 1.0 μm. When there is a temporal timing difference between the light reception signal) and the presence of the flame by determining the relative ratio between the two, for example, the relative ratio increases due to the temporal peak timing deviation between the two, It turned out that it might be misjudged as a flame.

The time difference between the peak timings of the first light receiving signal (4.5 μm light receiving signal) and the second light receiving signal (near infrared light receiving signal) is caused by the first light generated by the spark of the welding rod in the arc welding operation. Visible light including near-infrared radiation is emitted, followed by burning of the coating of the welding rod, and emission of light having a peak in the vicinity of 4.5 μm due to combustion of organic substances such as starch and CO ₂ resonance radiation due to high-temperature black body radiation. It is estimated that

  Therefore, in the present invention, the first light receiving signal (detected at a later timing) is delayed by delaying the second light receiving signal (near-infrared received signal) detected at an earlier time in a predetermined time. It is possible to reliably prevent the arc welding light from being erroneously determined as a flame by suppressing the temporal deviation from the 4.5 μm light reception signal) and obtaining the relative ratio between the two.

  In addition, by installing the flame detector according to the present invention in a factory where arc welding is performed, fire detection in the factory can be accelerated. Conventionally, in a factory where arc welding work is performed, a flame detector cannot be used, so a heat detector is used. The smoke detector cannot be used because smoke is generated in the factory under normal conditions. When using a heat sensor in a factory, the heat sensor is installed on the high ceiling, and it takes time until the thermal airflow accompanying the fire reaches the high ceiling and the fire is detected by the heat sensor. There is a high possibility that the fire will spread. However, by using the flame detector of the present invention that does not malfunction with respect to arc welding light, it is possible to detect fire flames early even if installed on a high ceiling in a factory or the like where arc welding is performed. It is possible to notify the fire before it becomes large.

In addition, a first light reception signal by light near 4.5 μm radiated by CO ₂ resonance due to flammable combustion and a second light reception signal by near infrared light near 0.7 to 1.0 μm by arc welding light. The ratio obtained in the case of flame can be made sufficiently large with respect to the ratio obtained in the case of arc welding light, and by increasing the difference between the two, It is possible to more accurately discriminate the presence and the radiation source of the arc welding light.

In addition, if the second received light signal of near infrared light in the vicinity of 0.7 to 1.0 μm due to arc welding light (disturbance light), illumination, or sunlight becomes too large, it is emitted by CO ₂ resonance due to flammable combustion. The ratio with the first received light signal due to light in the vicinity of 4.5 μm is lowered, and the sensitivity is extremely lowered. Therefore, in the present invention, when the second light receiving signal exceeds a predetermined level, disturbance light is obtained by obtaining a ratio with the first light receiving signal by using a predetermined constant instead of the second light receiving signal. Sensitivity deterioration due to arc welding light can be suppressed.

Further, the first received light signal by the light having a narrow band wavelength centered around 4.5 μm, which is emitted by CO ₂ resonance, and the near infrared light having a wavelength of 0.7 to 1.0 μm inherent to the arc welding light. In addition to the detection of the second received light signal by, the third received light signal is detected by light having a narrow band wavelength centered around 3.8 μm or 5.1 μm adjacent to the vicinity of 4.5 μm due to CO ₂ resonance (( When a flame detector is installed in a factory or the like by identifying and determining the presence of a flame and the radiation source of arc welding light based on the three-wavelength method), the first light-receiving signal, the second light-receiving signal, and the third light-receiving signal Even if arc welding work is performed, malfunction does not occur, nor does it malfunction even in sunlight, incandescent light bulbs, halogen lamps, etc., and it is possible to more reliably detect and report a fire flame.

The block diagram which showed embodiment of the flame detector by this invention used as a 2 wavelength system The block diagram which showed the function structure of the flame determination part of FIG. Time chart showing temporal changes in the relative ratio between near-infrared light reception signal and 4.5 μm light reception signal with temporal timing shift Time chart showing temporal changes in the relative ratio between near-infrared light receiving signal and 4.5 μm light receiving signal compensated for temporal timing deviation Time chart showing measured data of near-infrared light reception signal and 4.5μm light reception signal when intermittent welding work is performed Explanatory drawing which showed the integration process which correct | amended the time shift of the near-infrared light reception signal and 4.5 micrometer light reception signal in the flame determination part of FIG. The flowchart which showed the flame determination process in the case of implement | achieving the flame determination part of FIG. 2 by the program control of a processor Radiation spectrum diagram showing spectral characteristics of flame and arc welding light Time chart showing time change of ratio K calculated from 4.5 μm integral value and near infrared integral value for arc welding light Time chart showing time change of ratio K calculated from 4.5μm integral value and near infrared integral value for heptane flame The block diagram which showed the function structure by other embodiment of the flame determination part of FIG. The flowchart which showed the flame determination process in the case of implement | achieving the flame determination part of FIG. 11 by the program control of a processor The block diagram which showed embodiment of the flame detector by this invention used as a 3 wavelength system The block diagram which showed the function structure of the flame determination part of FIG. The flowchart which showed the flame determination process in the case of implement | achieving the flame determination part of FIG. 14 by the program control of a processor The block diagram which showed the function structure by other embodiment of the flame determination part of FIG. The flowchart which showed the flame determination process in the case of implement | achieving the flame determination part of FIG. 16 by the program control of a processor

FIG. 1 is a block diagram showing an embodiment of a flame detector according to the present invention, taking a two-wavelength system as an example. In FIG. 1, the flame detector 10 is a wavelength generated by the resonance radiation of CO ₂ generated by the first detection unit 11 a during the flammable combustion (the source that emits infrared light in the wavelength band near 4.5 μm is not necessarily flame). Two wavelength bands detected by the first detection unit 11a and the second detection unit 11b by the flame determination unit 26, detecting the radiation intensity in the near infrared wavelength band by the arc welding light by the second detection unit 11b. Flame detection is performed by a two-wavelength method in which the presence of a flame is determined based on the relative ratio of the detection values at.

The first detector 11a includes a first optical filter 14a that transmits infrared energy having a wavelength band of about 4.5 μm through resonance radiation of CO ₂ and converts the infrared energy into an electrical signal, and outputs the first optical filter 14a. A sensor module 12a having an element 16a, and a prefilter that passes only signal components in a predetermined frequency band known as a flame fluctuation frequency, for example, a frequency band centered on 2 Hz, from a signal output from the sensor module 12a A first frequency extraction unit 18a using a preamplifier, a preamplifier 20a that amplifies the signal component that has passed through the first frequency extraction unit 18a, and a main amplifier that amplifies the output from the preamplifier 20a to a signal level suitable for flame determination processing The 4.5 μm light reception signal e1 that becomes a digital signal from the amplified output (analog signal) output from the main amplifier 22a and 22a. It is provided an A / D converter 24a for converting. Here, the 4.5 μm light reception signal corresponds to the first light reception signal in the claims.

  In addition, the second optical unit 11b transmits near-infrared energy having a near-infrared wavelength band in the vicinity of 700 to 1000 nm (near 0.7 to 1.0 μm) to be converted into an electrical signal and output to the second detection unit 11b. A sensor module 12b having a filter 14b and a second light receiving element 16b using a phototransistor or a photodiode, and a predetermined frequency band known as a flame fluctuation frequency from the signal output from the sensor module 12b, for example, 2 Hz. The second frequency extraction unit 18b using a pre-filter that passes only the signal component of the frequency band defined as above, the preamplifier 20b that amplifies the signal component that has passed through the second frequency extraction unit 18b, and the output from the preamplifier 20b The main amplifier 22b that amplifies the signal level suitable for the flame determination process and the main amplifier 22b Amplifying output outputted are provided an A / D converter 24b for converting the (analog signal) to the near-infrared light reception signal e2 as a digital signal.

  In general, the wavelength of near-infrared light is around 700 to 2500 nm (near 0.7 to 2.5 μm), but this embodiment is based on the peak sensitivity wavelength of the phototransistor or photodiode used as the second light receiving element 16b. Thus, the radiation intensity in the near-infrared wavelength band near 700 to 1000 nm is detected. The near-infrared light reception signal corresponds to the second light reception signal in the claims.

When a phototransistor is used as the second light receiving element 16b, the transmission window provided in the case of the phototransistor has a near infrared energy having a wavelength band near 700 to 1000 nm (near 0.7 to 1.0 μm) of the near infrared. The phototransistor that functions as it is as the second optical filter 14b that transmits and converts it into an electrical signal and outputs it, and a commercially available product having a peak sensitivity wavelength in the vicinity of, for example, 800 to 900 nm can be used as it is.

  Further, as the phototransistor used as the second light receiving element 16b, a phototransistor without a filter in the transmission window can be used. In this case, not a transmission window characteristic but a spectral characteristic of a semiconductor element having a sensitivity near 700 to 1000 nm is used.

  This is the same when a photodiode is used as the second light receiving element 16b. For example, a photo PIN diode having a peak sensitivity wavelength near 1050 nm can be used.

  The 4.5 μm light reception signal e 1 and the near infrared light reception signal e 2 from the A / D converters 24 a and 24 b are input to the flame determination unit 26. The flame determination unit 26 performs discrimination determination between the presence of the flame and the radiation source of the arc welding light based on the 4.5 μm light reception signal e1 and the near infrared light reception signal e2.

  In the present invention, the time discrepancy between the 4.5 μm light reception signal e1 from the first detection unit 11a and the near infrared light reception signal e2 from the second detection unit 11b is corrected in the flame determination unit 26. A function as a correction unit is provided. This correction unit delays the near-infrared light reception signal e2 from the second detection unit 11b by a predetermined time Td and suppresses a time shift from the 4.5 μm light reception signal e1.

  For this reason, the flame determination unit 26 discriminates and determines the presence of the flame and the radiation source of the arc welding light based on the 4.5 μm light reception signal e1 and the near-infrared light reception signal e2 whose time shift is corrected by the correction unit. It will be. By delaying the near-infrared light reception signal e2 detected at a timing earlier in this way by a predetermined time Td, a time lag with respect to the 4.5 μm light reception signal e1 detected at a timing later in time is obtained. And reliably prevent the arc welding light from being misjudged as a flame.

  When the presence of the flame is determined by the flame determination unit 26, a flame determination signal is output to the alarm circuit 28, and the switching elements and the like are turned on, so that the receivers connected to the sensor terminals 30a and 30b An alarm current is passed between the sensor lines L and C, and a fire alarm signal is sent to the receiver.

The flame determination unit 26 sets K = e1 / e2 as a ratio K between the 4.5 μm light reception signal e1 and the near infrared light reception signal e2 delayed by Td time.
And the presence of flame is determined when the ratio K is equal to or greater than a predetermined threshold value Kth.

  FIG. 2 is a block diagram showing an embodiment of the functional configuration of the flame determination unit provided in FIG. In FIG. 2, the flame determination unit 26 is provided with an integrator 32a, which integrates the 4.5 μm light reception signal e1 from the A / D converter 24a of FIG. 1 in units of a predetermined time, and outputs a 4.5 μm integration signal E1. To do. This integration suppresses a rapid fluctuation caused by noise of the received light signal.

  The flame determination unit 26 is provided with a delay unit 31 and an integrator 32b that function as a correction unit. The delay unit 31 delays the near-infrared light reception signal e2 from the A / D converter 24b of FIG. 1 by a predetermined Td time, inputs it to the integrator 24b, and inputs the 4.5 μm light reception signal e1 input to the integrator 32a. Correct the time lag. The near-infrared light reception signal e2 delayed by the time Td by the delay unit 31 is input to the integrator 32b, and similarly to the integrator 32a, the near-infrared integration signal E2 is output by integration in a predetermined time unit, and suddenly due to noise or the like. Suppresses fluctuations.

  A shift register or the like can be used as the delay device 31, and the number of shift stages is set so that the time from when the near-infrared light receiving signal e2 is input to when it is output by the shift operation by clock input becomes a predetermined delay time Td. doing. In addition to the digital delay operation by the delay unit 31, for example, an analog delay unit may be provided before the A / D converter 24b to delay the operation.

  In the integrating operation by the integrators 32a and 32b, the sum of received light signals (digital signals) obtained in a fixed unit time by sampling of the A / D converters 24a and 24b is obtained. In addition, for each sampling of the A / D converters 24a and 24b, a sum by moving addition that is a sum of light reception signals (digital signals) obtained from a current time to a certain unit time before may be obtained.

The 4.5 μm integrated signal E1 from the integrator 32a is supplied to the ratio calculator 42, and the near-infrared integrated signal E2 from the integrator 32a is supplied to the ratio calculator 42 via the switching terminal a of the switch 40. ,
K = E1 / E2
The ratio K is calculated as follows. The ratio K is K = e1 / e2 based on the 4.5 μm light reception signal e1 and the near infrared light reception signal e2.
And substantially the same value.

  The ratio K calculated by the ratio calculator 42 is given to the comparator 44 and compared with a predetermined determination threshold value Kth set by the reference voltage source 45. When the ratio K is equal to or greater than the determination threshold value Kth, the comparator 44 determines the flame. An H level output is generated as a signal.

  FIG. 3 is a time chart (graph) showing the time variation of the 4.5 μm light reception signal, the near-infrared light reception signal having a temporal timing shift, and the ratio of both when the arc welding is intermittently performed.

  FIG. 3A is a time chart of the light reception signal. When arc welding is performed, the peak of the near infrared light reception signal e2 appears first, and the peak of the 4.5 μm light reception signal e1 appears after a predetermined time Td. Yes.

  FIG. 3B is a time change of the ratio K = e1 / e2 calculated from the 4.5 μm light reception signal e1 and the near infrared light reception signal e2 in FIG. 3A, and the time of two light reception signals by arc welding light. Due to the deviation, a peak portion having a ratio K = 2 or more is generated at two locations. For example, when Kth = 2 is set as the determination threshold value Kth for the comparator 44 in FIG. A misjudgment will be made.

  FIG. 4 is a time chart (graph) showing a time variation of a 4.5 μm light reception signal, a near-infrared light reception signal in which a temporal timing shift is corrected, and a ratio between the two when the arc welding is intermittently performed. .

  FIG. 4A is a time chart of the light reception signal. By delaying the near-infrared light reception signal e2 shown in FIG. 3A by a predetermined time Td, a near-infrared light reception signal e2 indicated by a broken line is obtained. Correction is made so that the time lag with respect to the .5 μm light reception signal e1 is reduced and the peaks of both coincide.

  FIG. 4B is a time change of the ratio K calculated from the 4.5 μm light reception signal e1 of FIG. 4A and the near infrared light reception signal e2 delayed by Td time, and the time of two light reception signals by arc welding light. Since the deviation is reduced, the peak value of the ratio K is, for example, less than Kth = 2, which is the determination threshold value Kth, and it is possible to reliably prevent the arc welding light from being erroneously determined as flame.

  FIG. 5 is a time chart (graph) showing actual measurement data of the 4.5 μm light reception signal e1 and the near infrared light reception signal e2 when intermittent welding work is performed, for example, the peak of the near infrared light reception signal e2 The delay time Td1 of the peak P2 of the 4.5 μm light reception signal e1 with respect to P1 is about 0.4 seconds, and the delay time Td2 of the peak P4 of the 4.5 μm light reception signal e1 with respect to the peak P3 of the near infrared light reception signal e2 Based on this, Td = 0.4 seconds may be set as the delay time of the delay device 31 of FIG.

  FIG. 6 is an explanatory diagram showing an integration process in which the time difference between the 4.5 μm light reception signal and the near-infrared light reception signal in the flame determination unit 26 of FIG. 2 is corrected.

  6 (A) and 6 (C) show time directions of discrete near-infrared light reception signal e2 and 4.5 μm light reception signal e1 converted into digital signals having a predetermined number of bits by A / D converters 24b and 24a. The near-infrared light reception signal e2 is obtained from time t1, whereas the 4.5 μm light reception signal e1 is obtained from time t2 delayed in time, with a time delay of Td time. Yes.

  The near-infrared light reception signal e2 from the A / D converter 24b in FIG. 6A is delayed by Td time by the delay unit 31 to become a delayed near-infrared light reception signal e2 shown in FIG. Is resolved.

  The integrator 32a performs a discrete integration operation of adding the 4.5 μm light reception signal e1 during the unit time Ti, and outputs a 4.5 μm integration signal E1. The integrator 32b performs a discrete integration operation of adding the near-infrared light reception signal e2 for the unit time Ti at the same timing, and outputs a near-infrared integration signal E2.

The integration of the integrators 32a and 32b is performed by moving addition that is the sum of the received light signals (digital signals) obtained from the present time until a certain unit time before the sampling of the A / D converters 24a and 24b. An integral value may be obtained.

  FIG. 7 is a flowchart showing a flame determination process when the function of the flame determination unit in FIG. 2 is realized by executing a program by a processor. In FIG. 7, the flame determination process reads a 4.5 μm integrated value E1 obtained by integrating the 4.5 μm light reception signal e1 from the A / D converter 24a in step S1, and then in step S2 from the A / D converter 24b. A near-infrared integrated value E2 obtained by integrating the near-infrared light receiving signal e2 with a predetermined time Td is read.

In step S3, the ratio K is set to K = E1 / E2.
Calculate as

  Subsequently, in step S4, it is determined whether or not the ratio K is equal to or greater than a predetermined determination threshold value Kth. If it is determined that the ratio K is equal to or greater than the determination threshold value Kth, the process proceeds to step S5. By outputting to the circuit 28 and operating it, a fire alarm signal is output to the receiver.

Next, the principle of discrimination determination between the flame and the arc welding light in the present invention will be described. FIG. 8 is a radiation spectrum characteristic diagram showing the spectral characteristics of the flame and arc welding light. The flame spectrum 46 and the arc welding light spectrum 48 are around 4.5 μm due to the resonance radiation resonance emission of CO ₂ generated during flame combustion. The result of having measured the radiant intensity of the substantially the same state is shown.

In FIG. 8, the flame spectrum 46 has a peak value of a large radiation intensity in the vicinity of 4.5 μm due to the resonance radiation of CO ₂ . The arc welding light spectrum 48 has a peak value of radiant intensity around 4.5 μm due to resonance emission of CO ₂ due to combustion of organic substances such as starch contained in the coating of the welding rod, and around 700 to 1000 nm (0.7 to 1). The radiation intensity is distributed in the near-infrared wavelength band, which is a wavelength band of around 0.0 μm), and in the shorter wavelength band.

Here, in the sensor module 12b provided in the embodiment of FIG. 1, the second optical filter 14b and the second light receiving element 16b using a phototransistor or a photodiode are used in the vicinity of 700 to 1000 nm in FIG. Near-infrared energy having a radiant intensity in the near-infrared wavelength band 50 of about 1.0 μm is detected.

The reason why the arc welding light spectrum 48 is distributed in the near-infrared wavelength band 50 is that, for example, feldspar is included in the coating of the welding rod used for arc welding, and the potassium contained in the feldspar burns around 760 nm. This is considered to be due to the characteristic emission of near-infrared light having a peak at. According to TIG welding (abbreviation of tungsten inert gas welding) using argon gas as a protective gas, near infrared light near 811 nm is characteristically emitted from the argon gas plasma accompanying arc welding. Conceivable. Due to the combustion of the covering component of the welding rod used for such arc welding, the arc welding light spectrum 48 has a peak value of the radiation intensity in the vicinity of 4.5 μm due to the resonance radiation of CO ₂ and the sensor module 12b. The radiant intensity is distributed in the near-infrared wavelength band 50 in the vicinity of 700 to 1000 nm (near 0.7 to 1.0 μm) as the detection wavelength band.

As is apparent from the spectral characteristics of the flame spectrum 46 and the arc welding light spectrum 48, in the conventional two-wavelength method, for example, a narrow wavelength band centered around 4.5 μm, which is the CO ₂ resonance radiation band, For example, it is understood that the radiant energy in a narrow wavelength band near 5.1 μm on the long wavelength side is detected, and the flame and the arc welding light cannot be discriminated and determined depending on the relative ratio of the detected output in these two wavelength bands. .

FIG. 9 is a time chart showing the time change of the ratio K calculated from the 4.5 μm integrated signal and the near-infrared integrated signal with respect to the arc welding light when the arc welding is intermittently performed. FIG. 9 shows a case where the timing deviation of light in the vicinity of 4.5 μm due to CO ₂ resonance radiation with respect to near infrared light in arc welding light is small.

In FIG. 9, the 4.5 μm integrated signal obtained by detecting the radiation intensity in the vicinity of 4.5 μm due to the resonance radiation of CO ₂ has a peak value every time the arc welding is intermittently performed as shown in the measurement characteristic 52. Yes.

  The ratio K = E1 / E2 calculated based on the near-infrared integrated signal (not shown) corresponding to the radiation intensity in the near-infrared wavelength band detected together with the 4.5 μm integrated signal that becomes the measurement characteristic 52 is the ratio It changes as shown by the characteristic 54. That is, when the 4.5 μm integrated signal increases in the measurement characteristic 52, the ratio K decreases as in the ratio characteristic 54. In this case, the ratio K is approximately within K = 2.

  FIG. 10 is a time chart showing the time change of the ratio K calculated from the 4.5 μm integrated signal and the near-infrared integrated signal for the heptane flame.

In FIG. 10, the 4.5 μm integrated signal obtained by detecting the radiation intensity in the vicinity of 4.5 μm due to the resonance radiation of CO ₂ fluctuates in accordance with the change in the size of the flame as indicated by the measurement characteristic 56. .

  The ratio K = E1 / E2 calculated based on the near-infrared integrated signal (not shown) corresponding to the radiation intensity in the near-infrared wavelength band detected together with the 4.5 μm integrated signal that becomes the measurement characteristic 56 is the ratio It changes as shown by the characteristic 58. That is, in the measurement characteristic 58, when the 4.5 μm integral signal becomes large, the value of the ratio K also becomes large like the ratio characteristic 54. In this case, the ratio K generally shows a large value such as K = 50 to 200. ing.

  As a result, the ratio K in the arc welding shown in FIG. 9 is approximately K = 2 or less, whereas the ratio K in the heptane flame in FIG. 10 is very large, approximately K = 50 to 200. Thus, by comparing and determining the changing ratio K, it is possible to reliably identify and determine the presence of the flame and the arc welding light.

  FIG. 11 is a block diagram illustrating a functional configuration according to another embodiment of the flame determination unit provided in FIG. 1. In the flame determination unit 26 of the present embodiment, the near-infrared light reception signal e2 is extremely large. In order to suppress a decrease in sensitivity due to arc welding light that becomes disturbance light in the case where the near-infrared light reception signal e2 exceeds a predetermined level, a predetermined constant c is used instead of the near-infrared light reception signal e2. It is characterized in that a decrease in sensitivity due to arc welding light is suppressed by obtaining a ratio K to a 4.5 μm light reception signal.

That is, when the near-infrared light reception signal e2 delayed by the predetermined time Td is less than the predetermined light reception threshold eth, the flame determination unit 26 sets K = the ratio K between the 4.5 μm light reception signal e1 and the near-infrared light reception signal e2. e1 / e2
On the other hand, if the near-infrared light reception signal e2 delayed by a predetermined time Td is equal to or greater than a predetermined light reception threshold eth, the ratio K of 4.5 μm light reception signal e1 and a predetermined constant c is K = e1 / c
And determining the presence of flame when the ratio is equal to or greater than a predetermined determination threshold value Kth.

  In the flame determination unit 26 of FIG. 11, a constant setter 34, a comparator 36, and a switcher 40 are newly provided, and other configurations are the same as those of the embodiment of FIG. That is, the flame determination unit 26 is provided with integrators 32a and 32b. The 4.5 μm light reception signal e1 from the A / D converters 24a and 24b in FIG. 1 and the near infrared light reception signal delayed by Td by the delay unit 31 are provided. e2 is integrated in a predetermined time unit, and a 4.5 μm integrated signal E1 and a near-infrared integrated signal E2 are output.

  The 4.5 μm integrated signal E1 from the integrator 32a is supplied to the ratio calculator 42, and the near-infrared integrated signal E2 from the integrator 32a is supplied to the ratio calculator 42 via the switching terminal a of the switch 40. . A constant setting device 34 that outputs a predetermined constant c is connected to the other switching terminal b of the switching device 40.

The switch 40 is controlled to be switched by the comparator 36. The comparator 36 compares the near-infrared integrated signal e2 from the integrator 32b with a predetermined light receiving threshold Eth set by the reference voltage source 38, and the L when the near-infrared integrated signal E2 is less than the light receiving threshold Eth. At the level output, as shown in the figure, the switch 40 is switched to the switch terminal a, the near-infrared integrated signal E2 from the integrator 32b is given to the ratio calculator 42, and the ratio calculator 42 is K = E1 / E2.
The ratio K is calculated as follows. The ratio K is K = e1 / e2 based on the 4.5 μm light reception signal e1 and the near infrared light reception signal e2 delayed by a predetermined time Td.
And substantially the same value.

On the other hand, the comparator 36 generates an H level output when the near-infrared integrated signal E2 becomes equal to or greater than the light reception threshold Eth, switches the switch 40 to the switch terminal b side, and calculates the ratio c of the constant c from the constant setter 34. The rate calculator 42 is K = E1 / c.
The ratio K is calculated as follows. This ratio K is K = e1 / c based on the 4.5 μm light reception signal e1 and the constant c.
And substantially the same value.

  The ratio K calculated by the ratio calculator 42 is given to the comparator 44 and compared with a predetermined determination threshold value Kth set by the reference voltage source 45. When the ratio K is equal to or greater than the determination threshold value Kth, the comparator 44 determines the flame. An H level output is generated as a signal.

  FIG. 12 is a flowchart showing a flame determination process when the function of the flame determination unit in FIG. 11 is realized by executing a program by a processor. In FIG. 12, in the flame determination process, the 4.5 μm integrated value E1 obtained by integrating the 4.5 μm light reception signal e1 from the A / D converter 24a is read in step S11, and then in step S12, the A / D converter 24b reads. A near-infrared integrated value E2 obtained by integrating the near-infrared light receiving signal e2 obtained by delaying by a predetermined time Td is read.

Subsequently, in step S13, it is determined whether or not the near-infrared integrated value E2 is less than a predetermined light reception threshold Eth, and if it is less than the light reception threshold Eth, the process proceeds to step S14, and the ratio K is set to K = E1 / E2.
Calculate as

On the other hand, if it is detected in step S13 that the near-infrared integrated value E2 is equal to or greater than the predetermined light receiving threshold Eth, the process proceeds to step S15, the near-infrared integrated value E2 is changed to a constant c, and the ratio K is set to K = E1. / C
Calculate as

  Subsequently, in step S17, it is determined whether or not the ratio K is equal to or greater than a predetermined determination threshold value Kth. If it is determined that the ratio K is equal to or greater than the determination threshold value Kth, the process proceeds to step S18 to determine the presence of flame and issue a flame determination signal. By outputting to the circuit 28 and operating it, a fire alarm signal is output to the receiver.

FIG. 13 is a block diagram showing another embodiment of the flame detector according to the present invention, taking a three-wavelength system as an example. In FIG. 13, the flame detector 10 has a wavelength band of about 4.5 μm due to resonance emission of CO ₂ generated during flammable combustion and 5.1 μm adjacent to a wavelength band of about 4.5 μm due to resonance emission of CO _2. Three wavelengths that detect the intensity of radiation in the nearby wavelength band and the near-infrared wavelength band of 0.7 to 1.0 μm of arc welding light, and detect the presence or absence of flames by the relative ratio of the detected values in the three wavelength bands The flame is determined by the formula.

  The flame detector 10 includes a sensor module 12a including a first optical filter 14a and a first light receiving element 16a, a first frequency extraction unit 18a, a preamplifier 20a, a main amplifier 22a, and an A / D converter 24a. The unit 11a detects a 4.5 μm light reception signal e1, and also includes a sensor module 12b including a second optical filter 14b and a second light receiving element 16b, a second frequency extraction unit 18b, a preamplifier 20b, a main amplifier 22b, and an A / D. The near-infrared light reception signal e2 is detected by the second detection unit 11b including the converter 24b, and this is the same as the embodiment in FIG.

In addition to this, in the present embodiment, the third detector 11c that detects the radiation intensity in the wavelength band near 5.1 μm adjacent to the wavelength band near 4.5 μm due to the resonance radiation of CO ₂ is provided. The third detector 11c includes a third optical filter 14c that transmits infrared energy having a narrow wavelength band that rubs around 5.1 μm with the center wavelength, converts the energy into an electrical signal, and outputs the electrical signal, and a pyroelectric third light receiving element. A pre-filter that passes only signal components in a predetermined frequency band known as a flame fluctuation frequency, for example, a frequency band centered on 2 Hz, from the signal output from the sensor module 12c. The third frequency extraction unit 18c used, the preamplifier 20c that amplifies the signal component that has passed through the third frequency extraction unit 18c, and the output from the preamplifier 20c A main amplifier 22c that amplifies the signal level suitable for constant processing, and an A / D converter 24c that converts the amplified output (analog signal) output from the main amplifier 22c into a 5.1 μm light reception signal e3 that is a digital signal. Provided. The 5.1 μm light reception signal corresponds to the third light reception signal in the claims.

  The flame determination unit 260 receives the 4.5 μm light reception signal e1, the near infrared light reception signal e2, and the 5.1 μm light reception signal e3 from the A / converters 24a, 24b, and 24c, and the near infrared light reception signal e2 is predetermined. When the time Td is delayed and the presence of the flame is discriminated from the radiation source of the arc welding light based on the three received light signals e1, e2, e3, and the presence of the flame is determined, By outputting a flame judgment signal and turning on the switching element, etc., an alarm current is sent to the sensor line from the receiver connected to the sensor terminals 30a and 30b, and a fire alarm signal is sent to the receiver. To do.

The flame determination unit 260 sets K1 = e1 / e2 as the first ratio K1 between the 4.5 μm light reception signal e1 and the near-infrared light reception signal e2 delayed by Td time.
Further, the flame determination unit 260 sets K2 = e1 / e3 as the second ratio K of the 4.5 μm light reception signal e1 and the 5.1 μm light reception signal e3.
And the presence of flame is determined when the first ratio K1 is equal to or greater than a predetermined first determination threshold value Kth1 and the second ratio K2 is equal to or greater than a predetermined second determination threshold value Kth2. Note that the second ratio K2 is a comparison between the signal e1 due to the output characteristically generated only by the flame and the signal e3 due to the characteristic output from other light sources.

  The first and second ratios K1 and K2 calculated by the ratio calculator 420 are given to the comparison determination unit 440. The comparison determination unit 440 determines the presence of a flame when the first ratio K1 is equal to or greater than a predetermined first determination threshold value Kth1 and the second ratio K2 is equal to or greater than a predetermined second determination threshold value Kth2.

In this way, by detecting the radiation intensity in the wavelength band near 5.1 μm adjacent to the wavelength band near 4.5 μm due to the resonance radiation of CO ₂ as the third wavelength, infrared determination other than flame is performed. It is possible to more reliably discriminate and discriminate from a body, for example, a high-temperature radiator such as sunlight, a relatively low-temperature radiator of about 300 ° C., a low-temperature radiator such as a human body, and the like.

  FIG. 14 is a block diagram showing a functional configuration as an embodiment of the flame determination unit provided in FIG. In FIG. 14, the delay unit 31 and the integrators 32a and 32b provided in the flame determination unit 260 are the same as those in the embodiment of the two-wavelength system in FIG. In addition, in the present embodiment, an integrator 32c is provided, which integrates the 5.1 μm light reception signal e3 from the A / D converter 24c in a predetermined time unit and outputs a 5.1 μm integration signal E3.

The ratio calculator 420 receives the 4.5 μm integrated signal E1 from the integrator 32a, the near-infrared integrated signal E2 from the integrator 32b, and the 5.1 μm integrated signal E3 from the integrator 32c, and receives the first ratio K1 and As the second ratio K2, K1 = E1 / E2
K2 = E1 / E3
Ask for.

  The first and second ratios K1 and K2 calculated by the ratio calculator 420 are given to the comparison determination unit 440. The comparison determination unit 440 determines the presence of a flame when the first ratio K1 is equal to or greater than a predetermined first determination threshold value Kth1 and the second ratio K2 is equal to or greater than a predetermined second determination threshold value Kth2.

Thus, by detecting the radiation intensity of the 5.1 μm wavelength band adjacent to the 4.5 μm wavelength band due to the resonance radiation of CO ₂ as the third wavelength and performing flame determination, an infrared radiator other than the flame, for example, It is possible to more reliably discriminate and discriminate from a high-temperature radiator such as sunlight, a relatively low-temperature radiator of about 300 ° C., a low-temperature radiator such as a human body, and the like.

  FIG. 15 is a flowchart showing a flame determination process when the function of the flame determination unit in FIG. 14 is realized by executing a program by a processor. In FIG. 15, the flame determination process reads the 4.5 μm integrated value E1 obtained by integrating the 4.5 μm light reception signal e1 from the A / D converter 24a in step S21, and in step S22, the near value from the A / D converter 24b. A near-infrared integrated value E2 obtained by integrating the near-infrared light receiving signal e3 from the A / D converter 24c in step S23 is read after the infrared receiving signal e2 is delayed and integrated by a predetermined time Td. Read E3.

Then, it progresses to step S24, and 1st and 2nd ratio K1, K2 is set to K1 = E1 / E2.
K2 = E1 / E3
Calculate as Subsequently, in step S25, it is determined whether or not the first ratio K1 is equal to or greater than a predetermined first determination threshold value Kth1, and if it is determined that the first ratio K1 is equal to or greater than the first determination threshold value Kth1, the process proceeds to step S26, It is determined whether or not the second determination threshold value Kth2 or more. If it is determined in step S26 that the second ratio K2 is equal to or greater than the predetermined second determination threshold value Kth2, the process proceeds to step S27, and the alarm circuit 28 is operated by determining the presence of flame, and the fire alarm signal is transmitted. Output to the receiver.

  FIG. 16 is a block diagram showing a functional configuration according to another embodiment of the flame determination unit provided in FIG. In the flame determination unit 26 of the present embodiment, the near-infrared light reception signal e2 is predetermined in order to suppress a decrease in sensitivity due to arc welding light that becomes disturbance light when the near-infrared light reception signal e2 becomes extremely large. When the level is exceeded, a predetermined constant c is used in place of the near-infrared light receiving signal e2, and the ratio K to the 4.5 μm light receiving signal is obtained to suppress the decrease in sensitivity due to arc welding light. Features.

  In the flame determination unit 260 of FIG. 16, a constant setter 34, a comparator 36, and a switcher 40 are newly provided, and other configurations are the same as those of the embodiment of FIG.

The ratio calculator 420 is an L level output of the comparator 36 when the near-infrared integrated signal E2 from the integrator 32b is less than the light reception threshold Eth set by the reference voltage source 38, and the switch 40 is switched as shown in the figure. Switching to the switching terminal a and inputting the near infrared integration signal E2 from the integrator 32b, the first ratio K1 and the second ratio from the 4.5 μm integration signal E1, the near infrared integration signal E2, and the 5.1 μm integration signal E3. As K2, K1 = E1 / E2
K2 = E1 / E3
Ask for.

The ratio calculator 420 is an H level output of the comparator 36 when the near-infrared integrated signal E2 from the integrator 32b is equal to or higher than the light reception threshold Eth set by the reference voltage source 38, and the switch 40 is switched to the switch terminal b. The constant c from the constant setter 34 is switched and the 4.5 μm integration signal E1, the constant c in place of the near-infrared integration signal E2, and the 5.1 μm integration signal E3 are used as the first ratio K1 and the second ratio K2. K1 = E1 / c
K2 = E1 / E3
Ask for.

  The first and second ratios K1 and K2 calculated by the ratio calculator 420 are given to the comparison determination unit 440. The comparison determination unit 440 determines the presence of a flame when the first ratio K1 is equal to or greater than a predetermined first determination threshold value Kth1 and the second ratio K2 is equal to or greater than a predetermined second determination threshold value Kth2.

  FIG. 17 is a flowchart showing a flame determination process when the function of the flame determination unit in FIG. 16 is realized by executing a program by a processor. In FIG. 17, the flame determination process reads the 4.5 μm integrated value E1 obtained by integrating the 4.5 μm light reception signal e1 from the A / D converter 24a in step S31, and in step S32, the near-in process from the A / D converter 24b. The near-infrared integrated value E2 obtained by integrating the near-infrared light receiving signal e3 from the A / D converter 24c in step S13 is read after the infrared receiving signal e2 is delayed and integrated by a predetermined time Td. Read E3.

Subsequently, in step S34, it is determined whether or not the near-infrared integrated value E2 is less than a predetermined light reception threshold Eth. If the light reception threshold Eth is detected, the process proceeds to step S35, and the first and first ratios K1 and K2 are set to K1 = E1. / E2
K2 = E1 / E3
Calculate as

On the other hand, if it is detected in step S34 that the near-infrared integrated value E2 is equal to or greater than the predetermined light receiving threshold Eth, the process proceeds to step S36, where the near-infrared integrated value E2 is changed to a constant c, and the first and first ratios K1. , K2 with K1 = E1 / c
K2 = E1 / E3
Calculate as

  Subsequently, in step S38, it is determined whether or not the first ratio K1 is equal to or greater than a predetermined first determination threshold value Kth1, and when it is determined that the first ratio K1 is equal to or greater than the first determination threshold value Kth1, the process proceeds to step S39, It is determined whether or not the second determination threshold value Kth2 or more. If it is determined in step S39 that the second ratio K2 is equal to or greater than the predetermined second determination threshold value Kth2, the process proceeds to step S40, and the alarm circuit 28 is operated by determining the presence of the flame, and the fire alarm is generated. The signal is output to the receiver.

  In the above embodiment, the near-infrared light reception signal is delayed by a predetermined time Td in real time to reduce the time shift from the 4.5 μm light reception signal. The time shift may be corrected by temporarily storing the received light signal in the memory and shifting the read position by an address corresponding to the delay time.

  Further, when the difference in the rise timing of the near-infrared light reception signal e2 and the 4.5 μm light reception signal e1 is shorter than the predetermined time Td due to variations in the delay time Td at the start of welding, in particular, the welding start time, the ratio K1 is large. However, Kth1 may be exceeded. For example, the read end position of the near-infrared light reception signal e2 is extended to the same extent as the read end position of the 4.5 μm light reception signal e1 to take measures against this problem. May be.

  Also, in the above embodiment, when the presence of a flame is determined, a fire alarm signal is sent by causing the alarm current of the sensing line from the receiver to flow by the operation of the alarm circuit. An appropriate transmission circuit may be provided instead of the information circuit, and the fire signal may be transmitted to the receiving side based on the flame determination.

In the three-wavelength system of the above embodiment, the radiation intensity in the wavelength band near 5.1 μm on the long wavelength side adjacent to the wavelength band near 4.5 μm due to the resonance radiation of CO ₂ is detected. The radiation intensity in the wavelength band near 3.8 μm on the short wavelength side adjacent to the wavelength band near 4.5 μm may be detected.

The present invention is not limited to the above-described embodiments, includes appropriate modifications that do not impair the objects and advantages thereof, and is not limited by the numerical values shown in the above-described embodiments.

10: Flame detectors 11a, 11b, 11c: First to third detectors 12a, 12b, 12c: Sensor modules 14a, 14b, 14c: First to third optical filters 16a, 16b, 16c: First to third Light receiving elements 18a, 18b, 18c: first to third frequency extraction units 20a, 20b, 20c: preamplifiers 22a, 22b, 22c: main amplifiers 24a, 24b, 24c: A / D converters 26, 260: flame determination unit 28 : Alarm circuit 31: delay units 32a, 32b, 32c: integrator 34: constant setting unit 36, 44: comparator 38, 45: reference voltage source 40: switching unit 42, 420: ratio calculator 440: comparison determination unit

Claims (15)

Narrowband wavelength light centered around 4.5 μm emitted by CO ₂ resonance generated during flammable combustion is selectively transmitted and converted into an electrical signal, and a signal component of a predetermined frequency is converted from the electrical signal. A first detector for selectively extracting and outputting a first light receiving signal;
A second detector that selectively transmits near-infrared light in a predetermined wavelength band, converts the light into an electrical signal, selectively extracts a signal component of a predetermined frequency from the electrical signal, and outputs a second received light signal;
A correction unit that corrects a temporal timing shift between the first light reception signal from the first detection unit and the second light reception signal from the second detection unit, which is detected when an arc welding operation is performed ;
A flame determination unit that discriminates the presence of the flame and the radiation source of the arc welding light based on the first light reception signal and the second light reception signal in which the temporal timing shift is corrected by the correction unit;
An alarm circuit that outputs a fire signal when the flame determination unit determines the presence of flame,
A flame detector characterized by comprising:
The flame detector according to claim 1,
The flame detector is characterized in that the correction unit delays the second light reception signal from the second detection unit for a predetermined time and suppresses a time lag from the first light reception signal.
The flame detector according to claim 1,
The first detector is
A first optical filter that selectively transmits light having a narrow band wavelength centered around 4.5 μm, which is emitted by CO ₂ resonance generated during flammable combustion;
A first light receiving element that receives the light transmitted through the first optical filter, converts the light into an electrical signal, and outputs the electrical signal;
A first frequency extraction unit that selectively extracts a signal component of a predetermined frequency from the output of the first light receiving element and outputs a first light receiving signal;
With
The second detector is
A second optical filter that transmits near-infrared light in a predetermined wavelength band;
A second light receiving element that receives light transmitted through the second optical filter, converts the light into an electrical signal, and outputs the electrical signal;
A second frequency extracting section for selectively extracting a signal component of a predetermined frequency from the output of the second light receiving element and outputting a second light receiving signal;
A flame detector characterized by comprising:
4. The flame sensor according to claim 3, wherein the second optical filter transmits near-infrared light having a wavelength band in the vicinity of 0.7 μm to 1.0 μm.
4. The flame detector according to claim 3, wherein the second optical filter and the second light receiving element include a transmission window that transmits light in the near infrared band, and has a peak wavelength at a predetermined wavelength in the near infrared band. A flame detector, which is a phototransistor or a photodiode.
The flame detector according to claim 1, wherein the flame determination unit includes:
A flame detector characterized in that a ratio K = e1 / e2 between the first light receiving signal e1 and the second light receiving signal e2 is obtained, and the presence of a flame is determined when the ratio K is equal to or greater than a predetermined threshold value Kth.
The flame detector according to claim 1, wherein the flame determination unit includes:
When the second light reception signal e2 is less than a predetermined light reception threshold eth, a ratio K = e1 / e2 between the first light reception signal e1 and the second light reception signal e2 is obtained.
When the second light reception signal e2 is equal to or greater than the light reception threshold eth, a ratio K = e1 / c between the first light reception signal e1 and a predetermined constant c is obtained.
The flame detector, wherein the presence of flame is determined when the ratio K is equal to or greater than a predetermined determination threshold value Kth.
The flame detector of claim 1, further comprising:
Only light of a narrow band wavelength centered on a predetermined wavelength adjacent to a wavelength band centered on 4.5 μm emitted by CO ₂ resonance generated during flammable combustion is selectively transmitted and converted into an electrical signal. A third detector for selectively extracting a signal component of a predetermined frequency from the electrical signal;
Provided,
The flame determination unit includes the presence of flame and radiation of arc welding light based on the first light reception signal, the second light reception signal, and the third light reception signal from the first detection unit, the second detection unit, and the third detection unit. A flame sensor characterized by distinguishing and determining a source.
The flame detector according to claim 8, wherein the third detector is
A third optical filter that selectively transmits light having a narrowband wavelength centered on a predetermined wavelength adjacent to a wavelength band centered around 4.5 μm;
A third light receiving element that receives the light transmitted through the third optical filter, converts the light into an electrical signal, and outputs the electrical signal;
A third frequency extracting section for selectively extracting a signal component of a predetermined frequency from the output of the third light receiving element and outputting a third light receiving signal;
A flame detector comprising:
10. The flame sensor according to claim 9, wherein the third optical filter is adjacent to a transmission narrow wavelength band having a central wavelength around 4.5 μm of the first optical filter, near 5.1 μm or near 3.8 μm. A flame detector characterized by selectively transmitting only light having a narrow band wavelength centered at the center wavelength.
The flame detector according to claim 8, wherein the flame determination unit includes:
A first ratio K1 = e1 / e2 between the first light reception signal e1 and the second light reception signal e2 is obtained, and a second ratio K2 = e3 / e2 between the third light reception signal e3 and the second light reception signal e2 is obtained. Seeking
The flame detector, wherein the presence of flame is determined when the first ratio K1 is equal to or greater than a predetermined first determination threshold value Kth1 and the second ratio K2 is equal to or greater than a predetermined second determination threshold value Kth2.
The flame detector according to claim 8, wherein the flame determination unit includes:
When the second light receiving signal e2 is equal to or greater than a predetermined light receiving threshold eth, a first ratio K1 = e1 / e2 between the first light receiving signal e1 and the second light receiving signal e2 is obtained and the third light receiving signal e3 is obtained. A second ratio K2 = e3 / e2 with respect to the second received light signal e2 is obtained,
When the second light receiving signal is less than the light receiving threshold eth, a first ratio K1 = e1 / c between the first light receiving signal e1 and a predetermined constant c is obtained and the third light receiving signal e3 and the constant c are obtained. Second ratio K2 = e3 / c is determined, and the presence of flame is determined when the first ratio K1 is equal to or greater than a predetermined first determination threshold value Kth1 and the second ratio K2 is equal to or greater than a predetermined second determination threshold value Kth2. A flame detector characterized by
9. The flame detector according to claim 8 , wherein the flame determination unit determines the presence of a flame based on an integrated signal obtained by integrating the first signal to the third light reception signal.
The first detector selectively transmits light having a narrow band wavelength centered around 4.5 μm, which is radiated by CO ₂ resonance generated during flammable combustion, and converts it into an electrical signal. The first light receiving signal is output by selectively extracting the signal component of the frequency of
The second detector selectively transmits near-infrared light in a predetermined wavelength band and converts it into an electrical signal, selectively extracts a signal component of a predetermined frequency from the electrical signal, and outputs a second received light signal.
The correction unit corrects a temporal timing shift between the first light reception signal from the first detection unit and the second light reception signal from the second detection unit, which is detected when the arc welding operation is performed ,
The flame determination unit discriminates and determines the presence of the flame and the radiation source of the arc welding light based on the first light reception signal and the second light reception signal in which the timing difference is corrected by the correction unit. A flame judgment method.
In the flame judgment method according to claim 14,
The first detector is
The first optical filter selectively transmits light having a narrow band wavelength centered around 4.5 μm, which is emitted by CO ₂ resonance generated during flammable combustion,
The first light receiving element receives the light transmitted through the first optical filter, converts it into an electrical signal, and outputs it.
A first frequency extraction unit selectively extracts a signal component of a predetermined frequency from the output of the first light receiving element and outputs a first light receiving signal;
The second detector is
The second optical filter transmits near infrared light of a predetermined wavelength band,
The second light receiving element receives the light transmitted through the second optical filter, converts it into an electrical signal, and outputs it.
A second frequency extraction unit that selectively extracts a signal component of a predetermined frequency from the output of the second light receiving element and outputs a second light receiving signal;
A flame determination method characterized by the above.

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