JP2673135B2 - Fire detection method and fire detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fire detection method for detecting a fire by detecting infrared rays emitted from a fire source, and particularly to detect infrared rays of multiple wavelengths simultaneously to distinguish between fire and non-fire. It applies to the fire detection method that clarifies. The present invention eliminates false alarms due to non-fire sources such as electric heaters and cooking, issues a warning according to the risk of fire from a relatively small fire (smoked state), and can promptly take an initial response. To provide a fire detection method.

[0002]

2. Description of the Related Art With conventional fire detection methods that detect smoke, heat, etc., it is difficult to detect smoke and heat in a building with a large space because it does not affect the upper part of the detector. Need to use a vessel. Conventionally, a flame detector that detects infrared rays emitted from a flame has been put into practical use. Most of these flame detectors detect the characteristic spectral line emitted from the flame (4.4 μm band; CO ₂ resonance radiation band), but there are several methods to reduce malfunctions due to infrared sources other than flames. Some attempts have been proposed. For example, Japanese Laid-Open Patent Publication No. 50-2497 detects the radiation doses at 4.3 μm and two wavelengths before and after it, and judges as a flame when the radiation doses at 4.3 μm and other two wavelengths exceed a certain value. doing. JP-A-57-96492 discloses 2
It proposes to detect the presence of a flame by determining whether or not a valley exists between two convex portions.

In addition, Japanese Patent Application Laid-Open No. 61-32195 discloses a first radiation detecting means for detecting radiation having a wavelength in the near infrared region, and a second radiation detecting means for detecting radiation having a wavelength in the photographic infrared region. Receiving means for receiving output signals from the first and second radiation detecting means, and calculating a logical combination of the output signals based on a level difference between these output signals and synchronism; and a combined output signal from the calculating means. Discloses a fire detecting device provided with a detecting means for distinguishing between a fire signal and a noise signal. This is because the flaming fire and the visible light noise have a synchronism in the correlation between the infrared rays of 2.3 μm and 0.9 μm, the smoldering fire does not show the synchronization, and the flaming fire and the smoldering fire are close. The infrared light intensity is higher than the photographic infrared light intensity, and the visible light noise is based on the fact that the near infrared light intensity is smaller than the photographic infrared light intensity. It distinguishes burning fire.

[0004] However, in the method of determining that there is no fire when the radiation intensity in the visible or near-infrared region is higher than the radiation intensity in the infrared region such as electric lamps, false alarms due to ordinary electric lamps are reduced. If the heating element does not emit visible or near-infrared rays or is weak, it is determined to be a fire and a false alarm is issued. That is, an electric heater or the like generates a false alarm, and its application is greatly restricted. Also, 4.3
μm and the radiation dose at two wavelengths before and after
In the method of judging as a flame when the radiation dose at 4.3 μm and the other two wavelengths exceeds a certain value, the flame can be detected but the flame is derived from a fire or a useful heat source. Origin cannot be detected. That is, there is a defect that a false alarm is generated by a flame of a gas range, a gas stove, or the like. Further, in the case of comparing the level difference between two types of radiation of 2.3 μm and 0.9 μm and the synchronicity to distinguish between fire and visible light noise, and to distinguish between flaming fire and smoldering fire, the type of fire However, there is no guarantee that the synchronicity mentioned here is observed depending on the way of burning, and the reliability is lacking.

Further, the inventors of the present invention have detected the wavelength bands of two or more wavelengths of the infrared rays radiated from the monitoring area in Japanese Patent Application No. Hei 2-0611951 to cope with such a situation, and detect the infrared intensity of each wavelength band. Calculate the temperature of the infrared source based on the ratio of
Judgment of the fire situation by calculating the infrared radiation intensity in any of the above wavelength bands from this temperature and calculating the heating area as follows based on this infrared radiation intensity and the output of the infrared detector that detects that wavelength band We devised a fire detection method to perform.

Let λ1, λ2, ... λn (n = integer of 2 or more) be detection wavelength bands, and let V1, V2, ... Vn be detection outputs of the respective wavelength bands detected by the infrared detector DT.
It is assumed that these detection outputs accurately reflect the infrared intensity of each wavelength band incident on the infrared detector DT. By the way, according to Planck's radiation law, the radiation intensity per unit area of the infrared radiation emitted from an object at a certain temperature T into a half space at a wavelength λ is expressed by the following equation.

(Equation 1) Here, C1 and C2 are constants determined by C1 = 2πhc ² and C2 = hc / k. Here, h is Planck's constant, c is light speed, and k is Boltzmann's constant. Substituting the two detection wavelength bands λ1 and λ2 and the infrared radiation intensities P1 and P2 in the wavelength bands into the above formula (1) to derive an approximate formula for obtaining the temperature T,

(Equation 2) If there is no absorption between λ1 and λ2 between the infrared source F and the infrared detector DT, P1 in the above equation (2),
P2 can be replaced with V1 and V2. That is,

(Equation 3) Becomes From the equation (3), the temperature of the infrared source is obtained by detecting the infrared rays having two different wavelengths.

Next, the blackbody radiation intensity per unit area at λ1 or λ2 from the temperature T determined by the above equation (3) (this is referred to as P1 'or P2') is Planck's radiation law, that is, (1) ) Is obtained from the formula. On the other hand, the infrared detector DT
The intensity of the infrared light incident on is 1 / (2πL ² ) depending on the distance L from the infrared source F. Therefore, the infrared ray intensity P1 ″ or P2 ″ to be incident on the infrared detector DT from the infrared ray source having an area having the above-obtained temperature T (s times the unit area) is 1 / P1 ′ or P2 ′. (2πL ² ) and s
Multiplied by. Actually, since s is unknown, for convenience, the intensity of infrared light incident on the infrared detector DT from the infrared source is used as the calculated value of P1 ″ and P2 ″. Since it is assumed that the output of the infrared detection unit accurately reflects the intensity of the incident infrared light, P1 or P2 can be obtained from V1 or V2. Therefore, if the distance L is known, the radiated infrared intensity P1 or P2 and the incident infrared intensity P calculated.
The ratio with 1'or P2 'represents the area s of the infrared source F.

Further, an infrared detector for detecting the resonance radiation band of CO ₂ is provided, and the infrared intensity of the black body radiation in the resonance radiation band of CO ₂ is calculated by the formula (1) from the temperature and the heating area of the infrared source obtained here. Pco2 'is calculated, and the infrared intensity Pco to be incident on the infrared detector is calculated in the same manner as P1 above.
2 "is calculated, and the ratio of this to Pco2 actually observed is calculated. Here, if Pco2">> Pco2, the infrared ray source is accompanied by a flame. In this way, it is possible to grasp the situation of the fire.

However, for an actual fire, it is necessary to grasp the situation and to issue an appropriate alarm based on it.
It is important how to judge the fire situation grasped here. In the above fire detection method, the situation is grasped from the temperature and area of the fire source. However, in this method where the heat source whose temperature is a certain value or more is vigilant and the heat source whose area is a certain value or more is judged as a fire, when there is a danger of fire because the temperature is low but the heat of a large area is generated, for example, heating equipment In case of overheating, it is not possible to understand the risk of fire.

[0010]

The inventors of the present invention have focused on the scale of a fire and the amount of heat given to the surroundings in such a situation,
With this, we devised a fire detection method and a fire detector that perform accurate fire detection and alarm issuing. That is, (1) In a fire detection method in which infrared rays radiated from a heat source are separated and detected in a plurality of wavelength bands, and whether or not there is a fire is determined by the ratio of the infrared intensity between each wavelength band and the absolute value of the infrared intensity. , The center wavelength is 3 μm, the half-value width is 0.4 μm (λ1), the center wavelength is 4.4 μm, the half-value width is 0.4 μm (λ2), and the center wavelength is 5.5 μm.
8 μm (λ3), center wavelength 8.5 μm, half width 1.0 μ
m (λ4), each of which is a wavelength band (λ1, λ3) and a detection output (V1, V3) or (λ3,
λ4) and the detection output (V3, V4) in that wavelength band, Tij = C2 × (λi−λj) / (λi × λj × 1n
((Vj / Vi) × (λj / λi) ⁵ )) (where C2 = hc / k (h; blank constant, k; Boltzmann constant, c; speed of light)) and the temperature Tij, and P (λi , Tij) = C1 / (λi ⁵ × (exp (C2
/ (Λi × Tij))-1)) (where C1 = 2πhc ² (h; blank constant, k;
Boltzmann constant, c; speed of light)) and the black body radiation intensity P (λi, per unit area) calculated from
Tij) and the heat generation area S calculated from the ratio of the detection output Vi of the wavelength band λi, W = Tij ⁴ σ × s (where σ = 5.673 × 10)
^-12 (W / cm ² · deg ⁴ )) to calculate the radiant energy amount W of the heat source and determine whether or not there is a fire based on the radiant energy amount W of the heat source and the rate of increase of the radiant energy amount W. Fire detection method characterized by. (2) The infrared ray radiated from the heat source is separated into a plurality of wavelength bands to be detected, and a judgment means for judging whether or not there is a fire based on the ratio of the infrared intensity between the wavelength bands and the absolute value of the infrared intensity is provided. In the fire detector, the plurality of wavelength bands have a center wavelength of 3 μm, a half value width of 0.4 μm (λ1), and a center wavelength of 4.
4 μm half-value width 0.4 μm (λ2), center wavelength 5.5 μ
m half-value width 0.8 μm (λ3), center wavelength 8.5 μm half-value width 1.0 μm (λ4), and the determination means detects the wavelength band (λ1, λ3) and its detection output. Using (V1, V3) or (λ3, λ4) and (V3, V4) in that wavelength band, Tij = C2 × (λi−λj) / (λi × λj × 1n
((Vj / Vi) × (λj / λi) ⁵ )) (where C2 = hc / k (h; blank constant, k; Boltzmann constant, c; light velocity)) means for calculating the temperature TiJ, and P (Λi, Tij) = C1 / (λi ⁵ × (exp (C2
/ (Λi × Tij))-1)) (where C1 = 2πhc ² (h; blank constant, k;
Boltzmann constant, c; speed of light)) and the black body radiation intensity P (λi, per unit area) calculated from
Tij) and a means for calculating the heat generation area s from the ratio of the detection output Vi of the wavelength band λi, and W = Tij ⁴ σ × s (where σ = 5.673 × 10).
^-12 (W / cm ² · deg ⁴ )) A means for calculating the radiant energy amount W of the heat source and the radiant energy amount W of the heat source and the rate of increase of the radiant energy amount W are used to judge whether or not there is a fire. (3) A means for calculating the temperature Tij is a wavelength band (λ
1, λ3) and detection output (V1, V3) in that wavelength band or (λ3, λ4) and (V3, V4) in that wavelength band are used. Tij = C2 × (λi−λj) / (λi × λj × 1n
The value of the temperature T13 or T34 calculated by ((Vj / Vi) × (λj / λi) ⁵ )) is 300 ° C.
When the temperature exceeds 300 ° C, T13
The fire detector according to the above (2), further comprising means for setting 34 as the temperature of the heat source. (4) The determining means determines the wavelength band λ2, the temperature Tij, and P (λ2, Tij) = C1 / (λ2 ⁵ × (exp (C2
/ (Λ2 × Tij))-1)) The black body radiation intensity P (λ2, per unit area) calculated from
Tij) and a detection output V2 in the wavelength band λ2 have a ratio of 2 or more, and a means for issuing an alarm of the presence of a flame is provided, and the fire detector according to the above (2) or (3). .. It is.

The specific method will be described below.
FIG. 1 is a conceptual diagram of a fire detector to which the present invention is applied. Infrared rays emitted from the infrared ray source F enter the infrared detecting section DT. In the infrared detector DT, the incident infrared light is separated and detected into a resonance radiation band of CO ₂ and two or more detection wavelength bands. The infrared intensity detected by the infrared detection unit DT is processed by the signal processing unit SP, and the temperature of the infrared source, the heat generation area, the amount of radiant energy, the presence or absence of flame, and the rate of change of these are calculated. The result of this calculation is judged by the judgment unit J and an alarm is issued.

The contents of processing in the signal processing unit SP will be specifically described. Of the wavelength bands separated by the infrared detector DT, the resonance radiation band of CO ₂ is λc, and the other detection wavelength bands are λ1, λ2, ... λn (n = integer of 2 or more). Of the detection outputs of the respective wavelength bands detected by the infrared detector DT, the detection output of the CO ₂ resonance radiation band is Vc, and the detection outputs of the other wavelength bands are V1 and V
2, ... Vn. It is assumed that these detection outputs accurately reflect the infrared intensity of each wavelength band incident on the infrared detection unit D. By the way, according to Planck's radiation law,
The radiant intensity per unit area of infrared rays emitted from an object at a certain temperature T into the half space at the wavelength λ is expressed by the following equation.

(Equation 4) Here, C1 and C2 are constants determined by C1 = 2πhc ² and C2 = hc / k. Here, h is Planck's constant, c is light speed, and k is Boltzmann's constant. Substituting the two detection wavelength bands λ1 and λ2 and the infrared radiation intensities P1 and P2 in the wavelength bands into the above formula (4) to derive an approximate formula for obtaining the temperature T,

(Equation 5) If there is no absorption between the infrared source F and the infrared detector DT for both λ1 and λ2, P1 of the above equation (5),
P2 can be replaced with V1 and V2. That is,

(Equation 6) Becomes From the equation (6), the temperature of the infrared source can be obtained by detecting infrared rays of two different wavelengths. The wavelength band for which the temperature is required can be a single combination, but if desired, it is desirable to use a combination of two or more wavelength bands and switch the temperature depending on the temperature of the infrared source.
For example, when detecting from a temperature of about 100 ° C, a wavelength band of about 10 μm is used, and when detecting a temperature of 1000 ° C. or more, a wavelength band of about 3 μm is used. It is possible to grasp the exact situation of the fire from the very early stages.

Next, the blackbody radiation intensity per unit area at λ1 or λ2 from the temperature T obtained by the above equation (6) (this is designated as P1 'or P2') is Planck's radiation law, that is, the equation ( Obtained from 4). On the other hand, the intensity of the infrared light incident on the infrared detector DT becomes 1 / (2πL ² ) depending on the distance L from the infrared source F. Therefore, the infrared ray intensity P1 ″ or P2 ″ to be incident on the infrared detector DT from the infrared ray source having an area having the above-obtained temperature T (s times the unit area) is 1 / P1 ′ or P2 ′. (2πL ² ) and s
Multiplied by. That is, P1 ″ = P1 ′ × 1 / (2πL ² ) × s (7) P2 ″ = P2 ′ × 1 / (2πL ² ) × s (8). Since it is assumed that the output of the infrared detector accurately reflects the intensity of the incident infrared light, P1 from V1 or V2
1 or P2 is known. Actually, since s is unknown, for convenience, the intensity of infrared light incident on the infrared detector DT from the infrared source is used as the calculated value of P1 ″ and P2 ″. Therefore, if the distance L is known, the radiant infrared intensity P1 or P
2 and incident infrared intensity P1 'or P obtained by calculation
The ratio with 2'represents the area s of the infrared source F as can be seen from the equations (7) and (8).

Further, the infrared intensity Pco2 'of the black body radiation in the resonance radiation band of CO ₂ is calculated from the temperature and heat generation area of the infrared source obtained here by the equation (4), and the above P
The infrared intensity Pco2 ″ to be incident on the infrared detector is obtained in the same manner as 1 ″ and the ratio of this to the actually observed Pco2 is calculated. Here, if Pco2 >> Pco2 ″, the infrared source is accompanied by a flame.

The temperature and area of the infrared source are obtained by the means described above. By the way, even if the temperature of the infrared source is high, if the size, that is, the area is small, it is not a fire, and conversely, if the temperature is low and the area is large, there is a high possibility of fire. What is important in considering such a heat source in all states is the amount of heat that the heat source gives to the surroundings. That is, if the amount of heat given to the surroundings is large, the risk of fire spread increases, and the expansion speed also increases. The amount of heat the fire source gives to the surroundings is determined by the amount of radiant energy of the fire source. Therefore, the amount of radiant energy can be considered as the scale of the fire source. The radiant energy W of the heat source at a certain temperature T and area s is expressed as W = T ⁴ σ · s (9) from the Stefan-Boltzmann law. Here, σ is a Stefan-Boltzmann constant, and σ = 5.673 × 10 ⁻¹² (W / cm ² · deg ⁴ ). Therefore, the scale of the fire source is determined from the temperature and area of the infrared source.

In the judgment unit J shown in FIG. 1, the signal processing unit SP
When the amount of radiant energy obtained by the above-mentioned means exceeds the amount of heat generated in a dangerous state in the target space, an alarm is issued. It is said that a general fire is in a dangerous state when the calorific value of the fire source is 5 kW to 20 kW, that is, a state in which a person present in the space feels dangerous. Of course, this value has a characteristic that can be changed depending on the size of the target space, the use, and the like. In addition, by providing one or more subdivisions for the value smaller than the heat generation amount in the dangerous state, and categorizing the danger stepwise and issuing an alarm each time the radiant energy amount exceeds each division, an early warning It is possible to issue a warning warning from the state, and it is possible to detect a fire with higher accuracy. FIG. 2 shows an example in which there are 6 stages of alarms as an example of the gradual division of the radiant energy amount from the smoldering of the initial fire to the flaming fire and the staged classification of the alarm. As shown in Fig. 2, a warning alert is issued due to the presence of a heating element at the very early stage of the fire, which makes it easier to detect the initial fire, and an alarm is issued according to the degree of danger. Correspondence becomes easy. Here, the gradual division is not limited to 6 steps, but is usually about 2 to 9 steps.

Furthermore, by paying attention to the increase in the amount of radiant energy, it is possible to grasp the change in the state of the fire more accurately. That is, when the amount of radiant energy is large and the amount of radiant energy is increasing, the possibility of a fire is very high. If the amount of radiant energy is large but there is no change over time, it is not a fire but a useful flame such as heating in many cases. Therefore, for example, as shown in FIG. 2, by issuing an alarm in accordance with the rate of increase in the amount of radiant energy in addition to issuing an alarm in six stages, it is possible to detect a fire more reliably from an earlier stage. .

The rate of increase in radiant energy is determined from the rate of change in the calculated amount of radiant energy over a fixed period of time. As this method, a method of storing calculated values of radiant energy in a time series for a predetermined time, performing high-frequency cutoff filter processing such as a moving average on the time series values, and comparing two radiant energy values separated by a certain time, Based on the time series values stored for a certain period of time, a method of obtaining a tendency of change from these values by the least square method is used. The storage time when calculating the increase rate is desirably 10 seconds or more, but desirably 3 minutes or less to avoid a delay in the alarm.

The criterion for fire judgment is that if the rate of increase in the amount of radiant energy exceeds a predetermined constant value, or if the rate of increase in radiant energy is divided into one or more predetermined stages, the rate of increase in radiant energy is the heat source. There is a case where the amount of radiant energy of the heat source shows an increase of a certain rate or more, and the rate of increase is divided into one or more predetermined stepwise division ratios of the radiant energy of the heat source. These are appropriately selected according to the requirements determined by the usage of the space. Usually, this division is appropriately about 1 to 5. The warning is when the heat source is judged to be a fire when the rate of increase in the amount of radiant energy exceeds the above criteria or when it falls within the above categories, and depending on each step of the rate of increase, for example, the amount of radiant energy described above. There are cases where the alarms of the six stages determined by are shifted to higher alarms, which are also appropriately selected according to the specifications of the target space.

Further, as in the example shown in FIG. 3, the fire possibility index is defined by the amount of radiant energy and the rate of increase thereof. When the fire possibility index exceeds one or more predetermined stepwise classifications, a more accurate fire detection can be performed by issuing an alarm corresponding to the case. It is usually desirable that this stepwise classification is about 2 to 9 steps.

In addition to the temperature, the area radiant energy, and the rate of increase of the radiant energy, from the ratio of Pco2 "and Pco2 calculated by the signal processing unit SP, when Pco2 >>Pco2", the infrared source emits a flame. The accuracy of fire detection is further improved by issuing a warning that it is accompanied.

The changes in temperature, heat generation area, and amount of radiant energy in various cases can be schematically shown in FIGS. 4, 5, and 6.
It becomes like. Here, FIG. 4 shows a case of cooking a fried food or the like. This is when the oil overheats and ignites while cooking. FIG. 5 shows the case of heating a panel heater or the like. This is due to overheating due to equipment failure during use.
FIG. 6 shows a case where a smoky fire leads to a fire in a state where electric appliances and the like are covered with a combustible material.

In the case of cooking, the temperature reaches a steady state within a few minutes from the start of cooking, but the heat generation area is determined by the cooking utensil and is substantially constant from the start of cooking. From point a1,
For example, it is assumed that the oil of oil cooking or the like is overheated and burned up at a point f1. The temperature rises gradually from the point a1, but the temperature rises sharply at the point f1, and the heat generation area also increases by the size of the flame. In such a case, the amount of radiant energy increases as the temperature rises from the start of cooking, and reaches a steady state within a few minutes. Further, the radiant energy increases from the point a1 due to overheating of the oil, and a sharp increase occurs at the point f1. In the case of the conventional fire detection method in which a heating element having an area equal to or higher than a certain temperature is judged to be a fire, the alarm shown in FIG. That is, the temperature exceeds the alarm reference value Ta after the oil has overheated and ignited, and the heat generation area exceeds the alarm reference value Sa almost at the same time, and a fire alarm is issued. On the other hand, in the method according to the present invention in which the radiant energy amount is divided into 6 stages and the alarm is issued stepwise, the alarm shown in FIG. 4 is obtained. That is, shortly after the start of cooking, the amount of radiant energy exceeds the first alarm criterion E1 and the presence of a heating element is reported. When the temperature exceeds the second alarm standard E2, the presence of a high-temperature object is reported, but in the case of cooking, the steady state is reached thereafter. This state continues during cooking, but in such a case, it is possible to go out and check the situation. Further, when the point a1 is passed and the state of overheating is reached, the amount of radiant energy exceeds the third alarm standard E3, and a high temperature danger alarm is issued. Further, as the overheating continues, the radiant energy exceeds the alarm standards E4 and E5 at the moment when the ignition is reached beyond the point f1 and a fire alarm is issued.

In the case of heating, a panel heater such as a panel heater having a relatively low temperature and a large area is often used in terms of safety. In this case, as shown in FIG. 5, the temperature gradually rises to about 50 ° C. from the start of heating, and thereafter it is kept constant. Also, the heat generation area is almost constant from the start of heating. Point a2
It shows the case where the temperature control of the heater fails and the temperature rises. The amount of radiant energy in the case of heating increases as the temperature rises from the start of heating. In the case of heating, the temperature is relatively low, but the amount of radiant energy is large due to the large area. From point a2, the amount of radiant energy increases with overheating of the device. The alarm in this case is as shown in FIG. Here is the case of a fire detection method in which a heating element having an area equal to or larger than a certain temperature is judged to be a fire as in the conventional case. In this case, however, the temperature rise is slow, so the temperature exceeds the temperature reference Ta. No warning is given at all. On the other hand, it is clear that the amount of radiant energy shows a large value because the heating area is large even if the heating temperature is low. The alarm in this case indicates the presence of a heating element shortly after the start of heating and then the presence of a high-temperature object, as shown in. Even when the temperature rises after the point a2, the increase in radiant energy is large even if the temperature rise is moderate,
Shortly after transitioning to the overheated state, it became an alarm of high temperature danger, and the amount of radiant energy exceeded E4, reaching the stage of indicating the possibility of fire. By checking at this stage, it is possible to prevent a fire from occurring.

When a combustible material covers an electric appliance or the like and a fire occurs from a smoldering state, the area of heat generation increases as the temperature rises. In FIG. 6, a point f3 indicates a time point when the smoldered state is ignited. The temperature rises sharply from the point f3 and the heat generation area also expands rapidly. The amount of radiant energy increases at an accelerated rate with the passage of time, and sharply increases after the point f3. In this case, the temperature exceeds the alarm reference value Ta before ignition, but the heat generation area exceeds the alarm reference value Sa after ignition. Therefore, when a fire is determined from the conventional temperature and area, a fire alarm is issued after ignition as shown in FIG. On the other hand, when a fire is judged based on the amount of radiant energy, the amount of radiant energy sharply increases with the passage of time, and the alarms are sequentially issued, such as the presence of a heating element, the presence of a high temperature object, and high temperature danger. Prior to ignition, the alarm reference value E4 is exceeded and a warning is issued indicating the possibility of fire. Then, at about the same time as the ignition, a fire alarm is issued. Therefore, when the possibility of fire is reported, appropriate measures can be taken.

Furthermore, when the rate of increase in the amount of radiant energy is included in the fire determination, the result is as follows. FIG. 7, FIG. 8 and FIG. 9 show an increase rate of the amount of radiant energy and an alarm based on a fire determination including the increase rate in the various cases described above. In this example, the values of D1 and D2 are set as the determination categories of the radiant energy increase rate. When the rate of increase of radiant energy is D1 or more, the heating element is expanding, and when it is D2 or more, it is expanding rapidly. In the example shown here, the final warning is issued by combining the determination based on the amount of radiant energy and the determination based on the rate of increase in radiant energy.

When the increase in radiant energy is less than D1, the final alarm is not issued when the radiant energy amount is less than E3, that is, up to the presence of a high temperature object, and the radiant energy amount is
Only when the judgment is E3 or higher, that is, high temperature danger or higher, judgment based on the amount of radiant energy is issued as a final warning. If the rate of increase in radiant energy becomes D1 or more, if the amount of radiant energy at that time is less than E3, that is, if there is a high-temperature object, the judgment by the amount of radiant energy is issued as a final warning, The amount of radiant energy
When it is judged to be E3 or higher, that is, high temperature danger or higher, an alarm is issued which advances the judgment by the amount of radiant energy one step further. That is, when the judgment based on the amount of radiant energy is a high temperature danger, a fire is issued, and when the judgment based on the amount of radiant energy is a fire or a fire, a fire alarm is issued.

When the rate of increase of radiant energy is D2 or more, an alarm is not issued when the amount of radiant energy at that time is less than E1, and when the amount of radiant energy is more than E1 and less than E3. An alarm is issued that advances the judgment based on the amount of radiant energy by one step. That is, when the determination based on the amount of radiant energy indicates the presence of a heating element, it is reported as the presence of a high temperature object, and when the determination based on the amount of radiant energy is the presence of a high temperature object, it is reported as a high temperature danger. If the amount of radiant energy is E3 or more, the judgment based on the amount of radiant energy is advanced in two stages and a final warning is issued. That is, in this case, a fire alarm is issued.

The rate of increase in radiant energy during cooking is
As shown in FIG. 7, the value becomes large at the start of cooking and becomes smaller as the state becomes steady. Furthermore, the rate of increase increases again in the overheated state, showing that there is a very large increase in radiant energy at the time of ignition. In this case, the alarm according to the above procedure is shown in FIG. Here, is a determination result based on the amount of radiant energy, and is equivalent to that of FIG. At the start of cooking, the rate of increase in radiant energy is high, so an alarm is issued to indicate the presence of a heating element or a high temperature object. However, no alarm is issued in the steady state. Shortly after overheating starts, the judgment by the amount of radiant energy becomes a high temperature danger state, and therefore a high temperature danger alarm is issued here. After that, the rate of increase in radiant energy also rises, and when D1 is exceeded, a warning of the possibility of fire is given. Furthermore, a fire alarm will be issued at the time of ignition.

Also in the case of heating, the rate of increase of radiant energy is
As shown in FIG. 8, it becomes large at the start and becomes smaller as the steady state is reached. Furthermore, the rate of increase increases again in the overheated state. The alarm in this case is shown in FIG. Here, is the determination result based on the amount of radiant energy and is equivalent to that of FIG. Even when heating is started, the rate of increase in radiant energy is high, and an alarm is issued to indicate the presence of a heating element. However, in the subsequent steady state, no alarm was issued. Shortly after overheating starts, the judgment by the amount of radiant energy becomes a high temperature danger state, and therefore a high temperature danger alarm is issued here. After that, the rate of increase in radiant energy also rises, and when D1 is exceeded, a warning of the possibility of fire is given. Furthermore, when the judgment of the amount of radiant energy shows the possibility of fire, a fire alarm is issued.

When smoldering and igniting in a state in which an electric appliance or the like is covered with a combustible material, as shown in FIG. 9, the rate of increase in radiant energy also increases with the passage of time. Here, is the determination result based on the amount of radiant energy and is equivalent to that of FIG. When the rate of increase of radiant energy becomes D1 or more, the final warning is high temperature danger because the judgment based on the amount of radiant energy indicates the presence of a high temperature object. After that, a warning of the possibility of fire is issued when the judgment based on the amount of radiant energy becomes high temperature danger, and a fire alarm is issued when the rate of increase in radiant energy reaches D2 or higher. As discussed above, by including the rate of increase in radiant energy in the determination of a fire, a fire detector can be issued that does not notify a useful heating element in a steady state and that it can be triggered before ignition or the like. Will be realized.

Further, as shown in FIG. 3, the fire possibility index is defined as a function of the amount of radiant energy and the rate of increase of radiant energy, and if a final alarm is issued from this value, more accurate fire detection can be performed. It will be possible.

Although the above discussion assumes that the output of the infrared detector accurately reflects the intensity of the incident infrared light in each wavelength band, in practice, a filter for separating the wavelength bands and an infrared detector are used. There is a possibility that the infrared detection sensitivity, that is, the output of the infrared detection unit with respect to the incident infrared intensity, may be different between wavelength bands depending on the wavelength band. In, it is sufficient to multiply by the output value of each wavelength band. In addition, although it is handled as if there is no absorption of infrared rays by the atmosphere, it is sufficient to select a wavelength band that does not absorb atmospheric air as the detection wavelength band. If such a wavelength band cannot be selected, the It is sufficient to multiply by the absorption correction value. However, since the wavelength band absorbed by the atmosphere is affected by the atmospheric conditions (humidity, CO ₂ , contained trace gas, etc.), the error becomes large and is not appropriate.

[0034]

[Embodiment] In the present embodiment, the wavelength band of infrared rays being detected has a center wavelength of 3 μm, a half value width of 0.4 μm, and a center wavelength of 4.
4μm half width 0.4μm, center wavelength 5.5μm half width 0.8μm,
The center wavelength is 8.5 μm and the half-value width is 1.0 μm. FIG. 10 shows an example of the configuration of a fire detector having the above detection wavelength band. In this embodiment, infrared rays radiated from a fire source or a similar heat source are periodically divided by a chopper, and four pyroelectric infrared sensors detect four different wavelength bands. These sensors have a built-in bandpass filter that transmits a predetermined wavelength band. Moreover, even if there are only 4 or less pyroelectric infrared sensors,
A method of detecting four types of wavelength bands by using a switching unit may be used. The signal detected by each sensor is amplified by an amplifier circuit and then converted into a digital signal by an A / D converter. The microprocessor performs synchronous detection and filtering on the digital signal based on the chopper dividing cycle, and returns the signal divided by the chopper to a continuous signal sequence. Further, the signal sequence obtained here is converted into a signal sequence for communication and digitally transmitted to a host computer. The host computer includes the signal processing unit SP and the judgment unit J in FIG.

In the process from a smoldering state to a fire, a low-temperature heating element expands while gradually increasing in temperature. Therefore, it is necessary to monitor the temperature of the heat source in a wide temperature range from a low temperature to a high temperature. Of the above wavelength bands, it is and to monitor low temperature heat generation. By the combination of these two wavelengths, the temperature of the heat source from 100 ℃ to 400 ℃,
Monitor the fever area. Also, it is the wavelength bands of and that monitor high temperature heat generation.
The temperature of the above heat source and the heat generation area are monitored. Also, the wavelength band for monitoring the presence or absence of flame is.

In this embodiment, the infrared rays from the heat source are separated by the chopper C and then the infrared sensor S.
The detection wavelength band of each infrared sensor incident on 1 to S2 is S
1 is, and the number of each sensor and the number of the detection wavelength band are the same. The output signal of the infrared sensor is
A is amplified by amplifier A for each sensor system
It is input to the / D converter AD. The A / D converter has a built-in multiplexer and converts signals of each sensor system into digital signals while switching them. As a matter of course, one A / D converter may be provided for each sensor system. The signals of the respective sensors converted into digital signals are synchronously detected by the microcomputer MC, and only signals having a frequency equal to the chopping period of the chopper, that is, signals corresponding to infrared rays chopped by the chopper are selectively taken out. Further, the microcomputer MC converts the signal extracted as described above into a communication digital code string and outputs it to the host computer. Of course, the analog signal may be transmitted as it is to the host computer without passing through the A / D converter, and the host computer may perform A / D conversion to perform the above processing, but this is not appropriate. Further, although synchronous detection may be performed with an analog signal as it is, it is difficult to obtain a dynamic range required for a fire detector.

The host computer calculates the temperature, the area, the amount of radiant energy and the rate of increase of the heat source from the detection signal of each wavelength band. The detection signal of each wavelength band does not directly reflect the intensity ratio between the respective wavelength bands. That is, the sensitivity of the system of each sensor is different due to the transmittance of the infrared band-pass filter installed in the sensors S1 to S4, the variation in the sensitivity between the sensors, the variation in the amplification rate between the amplifiers, and the like. . The host computer stores correction values for correcting these variations. Therefore, the calculation is accurately performed in the host computer.

An example of the processing procedure of the host computer is shown in the flowchart of FIG. The detection signal sent as a digital signal from the detection part is first subjected to a filtering process for noise reduction. The filtering process is performed by a digital filter such as a moving average. Next, the temperature is calculated by combining the wavelength bands of and. If the calculated temperature exceeds approximately 300 ° C to 400 ° C, the temperature calculated by combining the wavelength bands of and is more accurate, so use this to calculate the heat generation area in the wavelength band of To do. On the other hand, when the temperature is low, the combination of the and wavelength bands is more accurate, so this is used to calculate the heat generation area in the or wavelength band. The next step of calculating the heat generation area is to calculate whether the heat generating object is accompanied by a flame using the wavelength band of. The value obtained here is the ratio of the infrared intensity that should be detected in the wavelength band when the heating object is a black body to the actually detected infrared intensity (hereinafter CO ₂
Ratio). Further, the amount of radiant energy is obtained from the temperature and the heat generation area.

The temperature, the heat generation area, and the
The CO ₂ ratio and the amount of radiant energy are stored in the storage area of the host computer in chronological order within a time range of 1 to 10 minutes.
In addition, a time-series graph is displayed on the display screen of the host computer so that the guard can visually check the status. It is also printed out as needed.
The rate of increase in the amount of radiant energy is calculated from the time-series data of the amount of radiant energy stored here. In this embodiment, the rate of increase in the amount of radiant energy is derived from the coefficient obtained by the least square method. In addition, it is also possible to obtain the temperature and the rate of increase of the heat generation area as needed.

The judgment of fire is divided into six levels as shown in Table 1 by the absolute amount of radiant energy. further
When the CO ₂ ratio is 2 or more, an alarm indicating that there is a flame is issued. Also, if the radiant energy amount increases by about 2 W per second, it is determined that it is expanding, and if the radiant energy amount increases by about 20 W for another second, it is determined that it is rapidly increasing and an alarm is issued. .

The alarm is displayed on the display screen of the host computer and is also broadcast to the security room and the entire building by voice synthesis. Further, all records are recorded in an external storage device such as a magnetic disk device or a magnetic tape device of the host computer.

[0042]

[Table 1]

[0043]

By using the fire detector of the present invention,
By detecting the fire from the initial state, which was difficult to detect with the conventional fire detector, and by continuously monitoring the state, it is possible to effectively identify non-fire that is difficult to identify with the conventional fire detector, and Sensitivity makes it possible to detect fires with few false alarms.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a fire detection method of the present invention.

FIG. 2 is a diagram showing an example of a change in the amount of radiant energy and a fire determination category in the case of shifting from a smoky fire to a flaming fire.

FIG. 3 is a conceptual diagram that defines the possibility of fire from the amount of radiant energy and the rate of increase in radiant energy.

FIG. 4 is a diagram showing changes in temperature, area, and radiant energy in the case of cooking, and a diagram showing an example of a corresponding fire alarm.

FIG. 5 is a diagram showing changes in temperature, area, and radiant energy in the case of heating, and a diagram showing an example of a corresponding fire alarm.

6A and 6B are diagrams showing changes in temperature, area, and amount of radiant energy when a combustible material is covered with an electric appliance or the like and ignited from smoldering, and a diagram showing an example of a corresponding fire alarm.

FIG. 7 is a diagram showing a rate of increase in radiant energy and a state of an alarm during cooking.

FIG. 8 is a diagram showing an increase rate of radiant energy and a state of an alarm in the case of heating.

FIG. 9 is a diagram showing an increase rate of radiant energy when a combustible substance is covered with an electric appliance or the like from a smoldering state to an ignition state and an alarm state.

FIG. 10 is a diagram showing a detection configuration used in an example of the present invention.

FIG. 11 is an operation conceptual diagram of the host computer in the embodiment of the present invention.

[Explanation of symbols]

F Infrared source DT Infrared detector SP signal processor J Judgment unit S1-S4 Infrared sensor A Amplifier AD A / D converter MP Microcomputer Fire alarm judged from temperature and heat generation area Fire alarm judged from radiant energy amount of radiant energy Fire alarm determined by combining increase rate with

Claims (4)

(57) [Claims] 1. A fire detection method for detecting infrared rays radiated from a heat source by separating them into a plurality of wavelength bands, and judging whether or not there is a fire based on the ratio of the infrared intensity between the wavelength bands and the absolute value of the infrared intensity. In the above, the plurality of wavelength bands have a center wavelength of 3 μm and a half value width of 0.4 μm.
m (λ1), central wavelength 4.4 μm, half width 0.4 μm
(Λ2), center wavelength 5.5 μm half-value width 0.8 μm (λ
3), center wavelength 8.5 μm, half width 1.0 μm (λ4)
Of each wavelength band, and the detection output (V
1, V3) or (λ3, λ4) and the detection output (V3, V4) in the wavelength band, Tij = C2 × (λi−λj) / (λi × λj × 1n
((Vj / Vi) × (λj / λi) ⁵ )) (where C
2 = hc / k (h; blank constant, k; Boltzmann constant, c; speed of light)), and P (λi, Tij) = C1 / (λi ⁵ × (exp (C2
/ (Λi × Tij))-1)) (where C1 = 2πhc ² (h; blank constant, k;
Boltzmann constant, c; speed of light)) and the black body radiation intensity P (λi, per unit area) calculated from
Tij) and the heat generation area s calculated from the ratio of the detection output Vi of the wavelength band λi, W = Tij ⁴ σ × s (where σ = 5.673 × 10)
^-12 (W / cm ² · deg ⁴ )) to calculate the radiant energy amount W of the heat source and determine whether or not there is a fire based on the radiant energy amount W of the heat source and the rate of increase of the radiant energy amount W. Fire detection method characterized by. 2. A determination means for detecting infrared rays radiated from a heat source by separating the infrared rays into a plurality of wavelength bands and detecting the infrared rays intensity ratio between the respective wavelength bands and an absolute value of the infrared rays intensity to determine whether or not there is a fire. In a fire detector provided, the plurality of wavelength bands have a center wavelength of 3 μm and a half value width of 0.4 μ.
m (λ1), central wavelength 4.4 μm, half width 0.4 μm
(Λ2), center wavelength 5.5 μm half-value width 0.8 μm (λ
3), center wavelength 8.5 μm, half width 1.0 μm (λ4)
Of the wavelength bands (λ1, λ3) and the detection output (V
1, V3) or (λ3, λ4) and (V
3, V4), Tij = C2 × (λi−λj) / (λi × λj × 1n
((Vj / Vi) × (λj / λi) ⁵ )) (where C2 = hc / k (h; blank constant, k; Boltzmann constant, c; speed of light)), and means for calculating the temperature T; (Λi, Tij) = C1 / (λi ⁵ × (exp (C2
/ (Λi × Tij))-1)) (where C1 = 2πhc ² (h; blank constant, k;
Boltzmann constant, c; speed of light)) and the black body radiation intensity P (λi, per unit area) calculated from
Tij) and means for calculating the heat generation area S from the ratio of the detection output Vi of the wavelength band λi, and W = Tij ⁴ σ × s (where σ = 5.673 × 10)
^-12 (W / cm ² · deg ⁴ )) is used to calculate the radiant energy amount W of the heat source, and whether or not there is a fire is determined from the radiant energy amount W of the heat source and the rate of increase of the radiant energy amount W. A fire detector, characterized by comprising: 3. The means for calculating the temperature T comprises a wavelength band (λ1, λ3) and a detection output (V
1, V3) or (λ3, λ4) and (V
3, V4), Tij = C2 × (λi−λj) / (λi × λj × 1n
The value of the temperature T13 or T34 calculated from ((Vj / Vi) × (λj / λi) ⁵ )) is 300
The fire detector according to claim 2, further comprising means for setting T13 when the temperature exceeds 300C and T34 when the temperature is 300C or less. 4. The determining means sets the wavelength band λ2, the temperature T, and P (λ2, Tij) = C1 / (λ2 ⁵ × (exp (C2
/ (Λ2 × Tij))-1)) (where C1 = 2πhc ² (h; blank constant, k;
Boltzmann constant, c; light velocity)), and the black body radiation intensity P (λ2,
4. A fire detector according to claim 2 or 3, characterized in that it comprises means for issuing an alarm of the presence of a flame when the ratio of Tij) to the detection output V2 in the wavelength band λ2 is 2 or more.