JPS6367238B2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Technical Field of the Invention The present invention relates to a flame detection device that detects a flame regardless of whether it is outdoors or indoors by detecting characteristic radiation emitted from a flame. relates to a flame detection device that can prevent malfunctions due to the influence of low-temperature radiating objects.

(2) Background of the technology The radiation from the flame generated when combustible materials oxidize and burn in the air contains radiation with specific wavelengths determined by the type of combustible material. Among them, the horizontal axis is the wavelength λ and the vertical axis is the intensity I. As shown in curve A shown in Figure 1, the spectrum characteristic of all oxidative combustion is 4.4 μm emitted from carbon dioxide gas generated during oxidation. An example of this is infrared rays, which have a peak in the vicinity.

Such flame detection devices that detect flames by detecting infrared rays around 4.4 μm already exist, but there are various problems as described below, and it is desirable to improve the sensing ability and reliability. It is rare.

(3) Conventional technology and problems As mentioned above, flame detectors that simply detect infrared rays around 4.4 μm also detect infrared rays around 4.4 μm emitted from low-temperature radiating objects as shown by curve B in Figure 1. This poses a problem in that flame detection may malfunction.

To solve the above problem, in the example shown in Fig. 1, a band pass filter that passes radiation around 4.4 μm and a band pass filter that lets radiation around 4.0 μm pass are provided, and the intensity of the radiation that has passed through both filters is There are flame detectors that detect the difference between the wavelengths of the flame and detect a flame when the spectrum of wavelengths characteristic of a flame becomes a line spectrum (for example, the
Publication No. 9336). There is also a flame detector that detects flame by using the above-described fluctuation in the spectrum.

However, such flame detectors have the following problems. As an example, as shown in Fig. 1, in the case of a low-temperature radiating object that does not emit a flame of about 100°C, such as a tin roof in summer, the difference ΔI ₃ in the radiation intensity near 4.4 μm and near 4.0 μm is the There is not a sufficiently significant difference compared to the difference △I ₁ . That is, if the intensity difference is set small to increase sensitivity to flames, it will malfunction with respect to low-temperature radiating objects, and if the intensity difference is set large to prevent malfunctions, flames will not be detected.

Other problems include the fluctuation of sunlight reflecting off roads after rain, or the flickering of rotating lights on patrol cars, which can cause differences in radiation intensity and attract false alarms.

(4) Purpose of the invention The present invention provides a flame detection device that removes the influence of radiation emitting objects other than flames existing indoors or outdoors, improves the reliability of flame detection, and improves the sensitivity of flame detection. With the goal.

(5) Structure of the Invention The present invention uses an adaptive control method that statistically processes the intensity of infrared rays at wavelengths specific to flames and the time course of infrared rays at wavelengths near the wavelengths, to reduce the number of wavelengths that can cause malfunctions. This was done based on the idea of increasing the ability to detect flames by removing the influence of infrared rays other than flames, and the present invention accepts radiation with a unique wavelength emitted by flames and converts it into a corresponding electrical signal. a first radiation detection means for receiving radiation other than the characteristic wavelength emitted by the flame and converting it into a corresponding electrical signal; an average value of the output signal of the first radiation detection means over a predetermined period; a first arithmetic comparison means for determining whether the deviation from the instantaneous value is greater than or equal to a predetermined value; and the average value of the output signal of the second radiation detection means over a predetermined period and the instantaneous value thereof. a second arithmetic comparison means for determining whether the ratio with the deviation of A flame detection device is provided.

(6) Embodiment of the invention FIG. 2 shows a circuit diagram of a flame detection device as an embodiment of the invention.

Referring to FIG. 2, the flame detection device of the present invention includes a detection unit 1 that detects radiation from radiation 6 that detects a flame, a logic operation unit 2 that operates a signal from the detection unit, and a logic operation unit 2 that operates on a signal from the detection unit. It is composed of a judgment section 4 that compares and judges signals from the terminal, and an alarm section 5 that issues an alarm.

The detection unit 1 detects a wavelength λ ₁ specific to the flame of the radiator 6,
In the example shown in FIG. 1, the first bandpass filter 1 passes radiation around 4.4 μm.
1. A first photoelectric converter 12 that converts the signal from the bandpass filter into an electrical signal, and converts the analog signal from the photoelectric converter into a digital signal.
a first radiation detection system consisting of an AD converter 13; a wavelength λ ₂ which is different from the wavelength λ 1 described above and is close to the wavelength λ ₁ and has radiation distinguishability for flame detection _;
In the example shown in FIG. 1, a second bandpass filter 14 that passes radiation around 40 μm;
It is composed of a second radiation detection system consisting of a second photoelectric converter 15 and a second AD converter 16.

The photoelectric converter 15 and the second AD converter 16 in FIG. 2 are the first photoelectric converter 12 and the first AD converter 16, respectively.
This is similar to the AD converter 13.

Therefore, the output of the first radiation detection system is the radiation with the wavelength λ ₁ as the digital signal S13, and the output of the second radiation detection system is the radiation with the wavelength λ ₂ as the digital signal S16. Each is applied to a logic operation section.

The logic operation section is composed of the following. Buffer memories 21 and 25 receive and store the signals S13 and S16, respectively. Signals S13 and S16 are sent to the buffer memories 21 and 25, respectively.
A first clock oscillator 24 generates a clock signal for transmitting the stored signal to a subsequent circuit after a predetermined period of time has elapsed. Average value of signals sent from buffer memories 21 and 25
First and second average value calculation circuits 22 and 26 for determining _AVC and _AVR . The current radiation values for wavelengths λ ₁ , λ ₂ obtained as described above, i.e.
A step of calculating the deviations σ _C , σ R of the instantaneous V C , V _R (signals S13, S16) and the average values A V _C , A V _R of the radiation of wavelengths λ ₁ , λ ₂ obtained in the average value calculation circuits ₂₂ and ₂₆ . 1 and a second difference circuit 23, 27. Division circuit 2 that calculates the ratio R of the first deviation σ _C and the second deviation σ _R
8.

The signals σ _C and R obtained as described above are applied to the determining section 4 .

If the deviation σ _C is a certain value σ, for example 3 or more, preferably 7 or more, the judgment unit 4 determines that logic = “1”
a first comparator circuit 41 that outputs a logic value of "1" when the ratio R is a certain value β, for example 0.7 or more, preferably 2 or more;
It consists of an AND gate 43 that ANDs the logical output signals of the first and second comparison circuits 41 and 42.

When the output logic of AND gate 45 is “1”,
The alarm unit 5 is activated to notify that flame has been detected. The alarm section 5 is the same as the conventional one, for example, which provides notification by a buzzer or lamp, or outputs a flame signal to the outside.

In other words, the flame detection logic determines that a flame exists and issues an alarm when the following formula and conditions are simultaneously satisfied.

V _C −AV _C ≧α ... (1) σ _C /σ _R ≧ β ... (2) The first equation is a normalized one.

In the initial state, the clock oscillator 24 sends a certain number of signals S13 and S16 to the buffer memory 21,
Clock pulses are not emitted until the clock pulses are stored in S13 and S1.
6 is stored, a clock pulse is oscillated and the data stored in the buffer memories 21 and 25 is
Every time new data is input from the AD converters 13, 16 to the buffer memories 21, 25, it is sent to the subsequent circuit.

The buffer memories 21, 25 store a certain number of data, and store the latest data (signals S13, S1
6), the oldest data is sent out, and the average values in the average value calculation circuits 22 and 26 are updated accordingly.

The clock oscillator 24 also outputs a certain number of signals S1.
3. A clock pulse may be generated each time S16 is stored in the buffer memories 21 and 25, and the clock pulse may be sent to the subsequent circuit every cycle of the clock pulse. In that case, after receiving the clock pulse, the signals S13 and S of the buffer memories 21 and 25 are
16 is cleared and a certain number of signals S13 and S16 are sent again.
is stored in the buffer memories 21 and 25.

The basic principle of the above flame detection will be described below by giving an example.

In Figure 3, the horizontal axis is time t, the vertical axis is radiation intensity I, and the value V _C of radiation near wavelength λ ₁ , for example 4.4 μm.
and a curve plotting the value V _R of radiation at wavelength λ ₂ , for example, around 4.0 μm, and curves A V _C and A V _R plotting the average of V _C and V _R by the average value calculation circuits 22 and 26 in FIG. , which illustrates the values V _C ′ and V _R ′ of radiation with wavelengths λ ₁ and λ ₂ when a flame is generated.

Note that FIG. 3 exemplifies a case where a tin roof on a summer day as a low-temperature radiating object is around, and shows a case where the radiation intensity changes with the passage of time.

In the case of a normal flame _, as is clear from the characteristic diagram shown in _{FIG .} 0.7) is satisfied. Therefore, it is assumed that flame exists if the above conditions are met. This is considerably more accurate than conventional detection and can improve detection sensitivity.

Next, we will discuss low-temperature radiating objects. Although the radiation intensity from the low-temperature radiating object fluctuates as shown in FIG. 3, the deviation σ C between the average value A _C calculated by the average value calculation circuit 22 in FIG. 2 and the _{instantaneous} value V _C
is small. Therefore, the above equation (1) does not hold, and it is not considered that flame exists. Therefore, malfunctions due to radiation from low-temperature radiating objects can be prevented.

Furthermore, for example, even if radiation from a low-temperature radiating object temporarily satisfies the first equation due to transient noise, the second equation will not simultaneously hold; Malfunctions due to noise can be prevented.

Furthermore, we will discuss cases in which fluctuations caused by sunlight reflecting off roads after rain, or revolving lights from patrol cars, cause differences in radiation intensity. The average value calculation circuits 22 and 26 shown in FIG.
For example, calculate the average value after about 10 minutes. Therefore, the difference between the average value and the instantaneous value of fluctuations and changes in radiation intensity is within a certain value range, and the first equation does not hold as in the case of a low-temperature radiating object. Even if there is a temporary difference, the second equation will not hold true at the same time. From the above, even in this case, no malfunction occurs.

In carrying out the present invention, various modifications may be made in addition to those described above. For example, the logic operation section 2 and judgment section 4 in FIG. 2 can be replaced with a microprocessor. Also,
In the above example, a case was described in which digital signal processing is used as the main component, but analog signal processing or hybrid type signal processing can be used. Furthermore, although the average value calculation circuit calculates a simple moving average, a weighted average or the like may be used.

The clock oscillator 24 is connected to the AD converters 13 and 16.
The signals S13 and S16 from the buffer memory 2
1 and 25 can be given a timing pulse when taking in the data.

(6) Effects of the Invention As is clear from the above, according to the present invention, the influence of radiation emitting objects other than flames existing indoors or outdoors is removed, the reliability of flame detection is improved, and the reliability of flame detection is improved. A flame detection device with improved sensitivity is provided.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram of radiation intensity, Fig. 2 is a circuit diagram of a flame detection device as an embodiment of the present invention, and Fig. 3 is a characteristic diagram used to explain flame detection by the flame detection device of the present invention. . (Explanation of symbols), 1... detection unit, 11, 14...
... Band pass filter, 12, 15 ... Photoelectric converter, 13, 16 ... AD converter, 2 ... Logical operation section, 21, 25 ... Buffer memory, 22, 26
...Average value calculation circuit, 23, 27...Difference circuit, 2
8...Divider circuit, 24...Clock oscillator, 4...
... Judgment section, 41, 42 ... Comparison circuit, 43 ... AND gate, 5 ... Alarm section, 6 ... Flame.

Claims (1)

[Claims] 1. A first radiation detection means that receives radiation of a specific wavelength emitted by the flame and converts it into a corresponding electrical signal; A first radiation detection means that receives radiation of a wavelength other than the specific wavelength emitted by the flame and converts it into a corresponding electrical signal. a second radiation detection means; a first arithmetic comparison means for determining whether the deviation between the average value of the output signal of the first radiation detection means over a predetermined period and its instantaneous value is greater than or equal to a predetermined value; and , a second determining whether or not a ratio between the deviation and the deviation between the average value of the output signal of the second radiation detection means over a predetermined period and the instantaneous value thereof is greater than or equal to a predetermined value;
A flame detection device, comprising: arithmetic and comparing means, and outputting a flame detection signal based on the results of determination by the first and second arithmetic and comparing means.