JP5848082B2 - 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 in the vicinity of 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 emitted from the welded part that is at a high temperature due to black body radiation, and it is difficult to distinguish with a conventional flame detector, and there is a problem that malfunction occurs due to arc welding light.

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 by 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 flame determination unit that identifies the presence of a flame and the radiation source of the arc welding light based on the first light reception signal and the second light reception signal from the first detection unit and the second detection unit;
An alarm circuit that outputs a fire signal when the flame determination unit determines the presence of a flame,
The flame determination unit
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 flame is determined when the ratio K is equal to or greater than a predetermined determination threshold value Kth .

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 present invention, in the 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;
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 ;
A flame determination unit for discriminating between a flame and a radiation source 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; ,
An alarm circuit that outputs a fire signal when the flame determination unit determines the presence of a flame,
The flame determination unit
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 with
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 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 having a central wavelength in the vicinity of 3.8 μm or 5.1 μm adjacent to the transmission wavelength band in the vicinity of 4.5 μm of the first optical filter.

  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 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 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 from the first detection unit and the second detection unit,
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.
A flame determination method characterized by determining the presence of a flame when the ratio K is equal to or greater than a predetermined determination threshold value Kth .

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 received light signal by the light of the narrow band wavelength centered around 4.5 μm, which is radiated by CO ₂ resonance generated at the time of flammable combustion, is detected, and arc welding is performed. A second received light signal is detected by near infrared light in a wavelength band near 0.7 to 1.0 μm radiated by light (two-wavelength method), and the flame is detected based on the first received light signal and the second received light signal. Since the existence and the radiation source of the arc welding light are discriminated and determined, when installed in a factory where arc welding work is performed, the arc welding light does not malfunction, and the sunlight, incandescent bulb, halogen lamp, etc. do not malfunction. It is possible to reliably detect and notify the presence of a flame due to a fire.

  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, the presence of flame due to fire can be detected at an early stage even if installed on a high ceiling in a factory or the like that performs arc welding. 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 CO ₂ resonance, the third received light signal by the light having a narrow band wavelength centered at 3.8 μm or 5.1 μm adjacent to the vicinity of 4.5 μm by the CO ₂ resonance is detected (three-wavelength method). ), Arc welding when a flame detector is installed in a factory or the like by discriminating and determining the presence of the flame and the radiation source of the arc welding light based on the first light receiving signal, the second light receiving signal and the third light receiving signal Even if the work is performed, it does not malfunction, and it does not malfunction even in sunlight, incandescent bulbs, halogen lamps, etc., and the presence of a flame due to a fire can be detected and notified more reliably.

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. The flowchart which showed the flame determination process in the case of implement | achieving the flame determination part of FIG. 1 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 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. 7 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 detects the wavelength band by the resonance radiation of CO ₂ (the source that emits infrared rays in the 4.5 μm wavelength band is not necessarily flame) by the first detection unit 11a, and performs the second detection. The radiation intensity in the near-infrared wavelength band by the arc welding light is detected by the part 11b, and the flame is determined by the relative ratio of the detection values in the two wavelength bands detected by the flame detection part 26 by the first detection part 11a and the second detection part 11b. The flame detection is performed by the two-wavelength method for determining the presence of the.

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 detection unit 11b transmits a near-infrared energy having a near-infrared wavelength band in the vicinity of 700 to 1000 nm (0.7 to 1.0 μm), converts it into an electrical signal, and outputs the electrical signal. 14b and a sensor module 12b having 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, centering on 2 Hz. The second frequency extraction unit 18b using a pre-filter that passes only the signal component of the frequency band that has been transmitted, 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, A main amplifier 22b that amplifies to a signal level suitable for flame determination processing, and a main amplifier 22b Amplified output is provided to 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 (filter) provided in the phototransistor case has a wavelength band in the vicinity of 700 to 1000 nm (near 0.7 to 1.0 μm) of near infrared light. It functions as it is as the second optical filter 14b that transmits the near-infrared energy it has, converts it into an electrical signal and outputs it, and the phototransistor as the second light receiving element is a commercially available product with a peak sensitivity wavelength of, for example, around 800 to 900 nm. Can be used as 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. 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 the ratio K between the 4.5 μm light reception signal e1 and the near-infrared light reception signal e2.
And the presence of flame is determined when the ratio K is equal to or greater than a predetermined threshold value Kth.

  In contrast to such basic flame determination, the flame determination unit 26 of the present embodiment suppresses a decrease in sensitivity due to arc welding light that becomes disturbance light when the near-infrared light reception signal e2 becomes extremely large. Therefore, when the near-infrared light reception signal e2 exceeds a predetermined level, the arc welding light is obtained by using the predetermined constant c instead of the near-infrared light reception signal e2 to obtain the ratio K to the 4.5 μm light reception signal. It is possible to suppress a decrease in sensitivity due to.

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

  FIG. 2 is a block diagram illustrating an example of a functional configuration of the flame determination unit provided in FIG. In FIG. 2, the flame determination unit 26 is provided with integrators 32a and 32b. The 4.5 μm light reception signal e1 and the near infrared light reception signal e2 from the A / D converters 24a and 24b in FIG. Integration is performed, and a 4.5 μm integration signal E1 and a near-infrared integration signal E2 are output. This integration suppresses a rapid fluctuation caused by noise of the received light signal.

  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. . 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 the 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.
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. 3 is a flowchart showing a flame determination process when the function of the flame determination unit in FIG. 1 is realized by executing a program by a processor. In FIG. 3, 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. The near-infrared integrated value E2 obtained by integrating the near-infrared light receiving signal e2 is read.

Subsequently, in step S3, it is determined whether or not the near-infrared integrated value E2 is less than a predetermined light reception threshold Eth. If it is detected that the light reception threshold Eth is less than, the process proceeds to step S4, and the ratio K is set to K = E1 / E2
Calculate as

On the other hand, if it is detected in step S3 that the near-infrared integrated value E2 is equal to or greater than the predetermined light receiving threshold Eth, the process proceeds to step S5, 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 S7, 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 S8 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.

Next, the principle of discrimination determination between the flame and the arc welding light in the present invention will be described. FIG. 4 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. 4, the flame spectrum 46 has a peak value of the 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 large radiation intensity in the vicinity of 4.5 μm, and radiates in the near-infrared wavelength band, which is a wavelength band in the vicinity of 700 to 1000 nm (near 0.7 to 1.0 μm), and a band on the shorter wavelength side. The intensity is distributed.

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. 5 is a time chart showing the change with time 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.

In FIG. 5, the 4.5 μm integrated signal obtained by detecting the radiation intensity in the vicinity of 4.5 μm due to the resonant radiation of CO ₂ has a peak value every time the arc welding is intermittently performed, as indicated by 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. 6 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. 6, 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. 5 is approximately K = 2 or less, whereas the ratio K in the heptane flame of FIG. 6 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.

  For this reason, by setting, for example, Kth = 50 as the determination threshold value Kth shown in FIGS. 2 and 3, the presence of the flame and the arc welding light can be reliably identified and determined by comparison with the calculated ratio K.

FIG. 7 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. 7, the flame detector 10 has a wavelength band of about 4.5 μm due to the resonance emission of CO ₂ generated during flammable combustion and a 5.1 μm adjacent to the wavelength band of about 4.5 μm due to the 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 inputs 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 receives the three light reception signals e1, e2, and e2. Based on e3, the determination of the presence of the flame and the radiation source of the arc welding light is performed. When the presence of the flame is determined, a flame determination signal is output to the alarm circuit 28, and the switching element or the like is turned on. An alarm current is supplied 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.

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.
Further, the flame determination unit 260 sets K2 = e1 / e3 as the second ratio K2 of the 4.5 μm light reception signal e1 and the 5.1 μm light reception signal e3.
And the presence of flame is basically determined when the first ratio K1 is equal to or greater than a predetermined first determination threshold Kth1 and equal to or greater than the second ratio K2 or the predetermined second determination threshold 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.

In contrast to this basic flame determination, in the flame determination unit 260 of the present embodiment, when the near-infrared light reception signal e2 is less than a predetermined light reception threshold eth, the 4.5 μm light reception signal e1 and the near-infrared light reception signal From e2 and 5.1 μm light reception signal e3, K1 = e1 / e2 as first ratio K1 and second ratio K2.
K2 = e1 / e3
On the other hand, if the near-infrared light reception signal e2 is equal to or greater than the predetermined light-receiving threshold value eth, the 4.5 μm light-receiving signal e1, the predetermined constant c in place of the near-infrared light-receiving signal e2, and the 5.1 μm light-receiving signal e3 As the first ratio K1 and the second ratio K2, K1 = e1 / c
K2 = e1 / e3
In any case, the presence of flame is determined when the first ratio K1 is equal to or greater than the predetermined first determination threshold Kth1 and the second ratio K2 is equal to or greater than the predetermined second determination threshold Kth2.

  Thus, when the near-infrared light receiving signal e2 exceeds a predetermined level, arc welding light that becomes disturbance light is obtained by using the predetermined constant c instead of the near-infrared light receiving signal e2 to obtain the ratios K1 and K2. It is possible to suppress a decrease in sensitivity due to.

  FIG. 8 is a block diagram illustrating an example of a functional configuration of the flame determination unit provided in FIG. In FIG. 8, the integrators 32a and 32b, the constant setting unit 34, the comparator 36, and the switching unit 40 provided in the flame determination unit 260 are the same as those in the two-wavelength embodiment of FIG.

  In addition, in this embodiment, an integrator 32c is provided, which integrates the 5.1 μm light reception signal e3 from the A / D converter 24c of FIG. 7 in a predetermined time unit and outputs a 5.1 μm integration signal E3.

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 inputted and the 4.5 μm integration signal E1, the predetermined constant c in place of the near-infrared received light integration signal E2, and the first ratio K1 and the second from the 5.1 μm integration signal E3. The ratio K2 is 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.

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, the presence of the flame is determined. It is possible to more reliably discriminate and distinguish from an infrared radiator, 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. 9 is a flowchart showing a flame determination process when the function of the flame determination unit in FIG. 7 is realized by executing a program by a processor. In FIG. 9, 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 S11, and in step S12, the flame determination process from the A / D converter 24b. A near-infrared integrated value E2 obtained by integrating the infrared received light signal e2 is read, and further, a near-infrared integrated value E3 obtained by integrating the near-infrared received signal e3 from the A / D converter 24c is read in step S13.

Subsequently, in step S14, 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 S15, and the first and second 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 S14 that the near-infrared integral value E2 is equal to or greater than the predetermined light reception threshold Eth, the process proceeds to step S16, the near-infrared integral value E2 is changed to a constant c, and the first and second ratios K1 and K2 are K1 = E1 / c
K2 = E1 / E3
Calculate as

  Subsequently, in step S18, 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 S19. It is determined whether or not the second determination threshold value Kth2 or more. If it is determined in step S19 that the second ratio K2 is greater than or equal to a predetermined second determination threshold value Kth2, the process proceeds to step S20, where the presence of a fire is determined and the alarm circuit 28 is operated, thereby causing a fire alarm signal. Is output to the receiver.

  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 32a, 32b, 32c: integrator 34: constant setter 36, 44: comparator 38, 45: reference voltage source 40: switch 42, 420: ratio calculator 440: comparison determination unit

Claims (10)

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 flame determination unit for determining the presence of a flame and a radiation source of arc welding light based on the first light reception signal and the second light reception signal from the first detection unit and the second detection unit;
An alarm circuit that outputs a fire signal when the flame determination unit determines the presence of flame,
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.
If the second light receiving signal e2 is greater than or equal to the light receiving threshold eth obtains the ratio K = e1 / c of the first light receiving signal e1 and a predetermined constant c,
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 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:
3. The flame sensor according to claim 2 , wherein the second optical filter transmits near-infrared light having a wavelength band of about 0.7 μm to 1.0 μm.
3. The flame detector according to claim 2 , wherein the second optical filter and the second light receiving element include a transmission window that transmits light in a 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.
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;
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;
Based on the first light receiving signal, the second light receiving signal, and the third light receiving signal from the first detection unit, the second detection unit, and the third detection unit, the presence of the flame and the radiation source of the arc welding light are discriminated and determined. A flame determination unit;
An alarm circuit that outputs a fire signal when the flame determination unit determines the presence of flame,
The flame determination unit includes
When the second light reception signal e2 is less than a 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 is obtained. A second ratio K2 = e1 / e3 with the third light receiving signal e3 is obtained,
When the second light reception signal e2 is equal to or greater than the light reception threshold eth, a first ratio K1 = e1 / c between the first light reception signal e1 and a predetermined constant c is obtained and the first light reception signal e1 and the third light reception signal e1 are calculated. A second ratio K2 = e1 / e3 with the light reception signal e3 is obtained,
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 5 , 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:
7. The flame sensor according to claim 6 , 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.
6. The flame detector according to claim 5 , 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 flame determination unit discriminates and determines the presence of a flame and the radiation source of the arc welding light based on the first light reception signal and the second light reception signal from the first detection unit and the second detection unit, and the flame determination unit Is
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.
If the second light receiving signal e2 is greater than or equal to the light receiving threshold eth obtains the ratio K = e1 / c of the first light receiving signal e1 and a predetermined constant c,
A flame determination method characterized by determining the presence of a flame when the ratio K is equal to or greater than a predetermined determination threshold value Kth .
In the flame judgment method according to claim 9 ,
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 flame determination method, wherein a second frequency extraction unit selectively extracts a signal component having a predetermined frequency from the output of the second light receiving element and outputs a second light reception signal.

Images