JPS5853725B2 - flame detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flame detector, and more particularly, to one that detects a flame by detecting the optical waveform of radiant light from a flame.

Conventional flame detectors employ various detection methods, focusing on the characteristic that the radiant light from a flame becomes large and bright, which is characteristic of a flame, and also flickers due to fluctuations in the flame.

For example, the brightness of a flame and the presence of flickering are detected by dividing the light into DC and AC components after photoelectric conversion.
A method has been considered in which it is detected as a flame when both exist at the same time, but this method detects when the DC component of the light exceeds a set level, so the judgment is based on the absolute value of the light. For example, when setting it to a level slightly higher than the level of lighting etc., for example, when setting it on a road, the presence or absence of DC light from passing car headlights can be determined without distinguishing it from DC light as a flame. <<, and at the same time, there was a risk that a light source having a frequency component similar to a flickering component, such as a rotating lamp, would be detected as a flame and malfunction.

The present invention has been made in view of the above-mentioned drawbacks, and provides a predetermined magnitude relationship between the peak value, average value, and predetermined value of the photoelectric conversion output waveform of light radiated from a flame, and a predetermined value that is proportional to the peak value and is less than or equal to the peak value. To provide a flame detector which can detect flames reliably and is free from malfunction due to instantaneous irradiation of illumination or instantaneous changes in illumination, for example.

To explain the present invention in detail, changes in the radiant light from the flame are taken as the degree of modulation of the flickering component unique to the flame, and the flame radiation waveform is determined by the brightness of the light relative to the average value corresponding to the electrical DC component. , the amplitude is modulated by a unique flickering component corresponding to the electric current, and in the case of a small flame, the frequency components have a large proportion of higher frequencies, and the degree of modulation is deep.
Although the change is large, the average modulation degree is about 30 to 60%, except when it becomes suddenly large or small.

However, A is the peak value of the waveform B is the trough value of the waveform shall be.

Further, for a large flame, for example, the distribution of frequency components has more low frequencies than a small flame, and the degree of modulation is also relatively shallow.

Therefore, a large flame with a low frequency component and a low degree of modulation is suitable as a detection target, but a small flame can also be detected by appropriately determining a predetermined value below the peak value of the output waveform.

Next, the configuration of an embodiment of the present invention will be explained with reference to FIG. 1 of the drawings.

Reference numeral 1 denotes a photoelectric conversion device, which includes a light receiving element such as a silicon photodiode and an infrared transmission filter disposed in front of the light receiving element, and receives only infrared light and performs photoelectric conversion.

Reference numeral 2 denotes an automatic gain control amplifier that amplifies the electric signal from the photoelectric conversion device 1 and outputs it as a constant output waveform that is the same as the input waveform regardless of the thickness of the input signal.

Next, 3 is a first detection device that detects the peak value of the photoelectric conversion output waveform of the photoelectric conversion device 1.

This first detection device 3 is composed of a charging/discharging circuit including a resistor and a capacitor, and has a charging time constant τ.

(The discharge time constant is τ6.

A second detection device 4 detects the average value of the photoelectric conversion output waveform of the photoelectric conversion device 1.

This second detection device 4 is constituted by a charging/discharging circuit including a resistor and a capacitor, and has a charging time constant τ - (discharging time constant τ).

Furthermore, 5 is a third detection device, which detects a predetermined value, for example, a peak value, which is proportional to the peak value of the photoelectric conversion output waveform of the photoelectric conversion device 1 and proportional to the peak value below this peak value. The detection device is constituted by a resistive divider circuit for the output of the first detection device 3.

Next, 6 is a first differential amplifier circuit, which is connected to the second detection device 4.
The average value of the output waveform output from the third detection device 5 is compared with a predetermined value less than the peak value of the output waveform output from the third detection device 5, and the difference between the two outputs is amplified and output.

7 is a second differential amplifier circuit, which compares the peak value of the output waveform output from the first detection device 3 and the average value of the output waveform output from the second detection device 4; , the difference between both outputs is amplified and output.

Further, 8 and 9 are the first and second differential amplifier circuits 6 and 7.
The first detection circuit 8 detects the output level of the photoelectric conversion output waveform from the first differential amplifier circuit 6 at a predetermined value below the peak value. The second detection circuit 89 receives an input from the second differential amplifier circuit 7 when the peak value of the photoelectric conversion output waveform is larger than the average value. Output at times.

Next, 10 and 11 are first and second level detection circuits,
The first and second level detection circuits 10 and 11 detect the levels of the outputs of the first and second detection circuits 8 and 9, respectively, and output a differential output that is higher than a set value. Output if there is.

Further, 12 is an AND circuit which outputs an output when the outputs of the first and second level detection times 10 and 11 are simultaneously present.

Furthermore, 13 is an integrating circuit which integrates the output of the AND circuit 12, and is composed of a charging/discharging circuit using a resistor and a capacitor, and the time constant is set so that the charging value > the discharging value, thereby preventing malfunction. It has become so.

Further, 14 is a level detection circuit which detects the integral level of the integrating circuit 13 and determines it as a flame.
It is composed of a J circuit, and as a circuit with a large hysteresis due to its detection characteristics, it is easy to turn ON and stabilizes the detection operation by turning OFF.

Reference numeral 15 denotes an alarm output circuit, which is activated by the signal from the level detection circuit 14 to activate the alarm device.

Next, the operation of this embodiment will be explained.

The radiant light from the flame is converted by the photoelectric conversion device 1 into an electrical signal a with a waveform as shown in Fig. 2, and this electrical signal a is amplified by the automatic gain control amplifier 2, regardless of the magnitude of the input signal. Output as an output waveform of approximately constant size.

The received light waveform is deformed by the frequency characteristics of the automatic gain control amplifier 2, but in the case of a flame, there is almost no deformation, but the light from a rotating lamp has a frequency characteristic to the flame, as shown in Figure 3. The signal outputs only the components.

The average peak value and predetermined value of the output waveform of the automatic gain control amplifier 2 are detected by each of the detection devices 3, 4, and 5, and the first detection device 3 detects the signal waveform c1 of the peak value.
The detection device 4 outputs a signal waveform d of the average value, and the third detection device 5 outputs a signal waveform e of a predetermined value below the peak value, for example, a peak value.

In the case of flame, the modulation degree is 5 to 60%, so
Peak value〉Average value〉German peak value (predetermined value)...
In cases related to (a), it is detected as a flame.

That is, the first differential amplifier 6 compares the average value waveform d and the shame peak value waveform e, and only when the average value waveform d is large, the differential amplification output f is input to the first detection circuit 8. .

Also, the second differential amplifier 7 compares the peak value waveform C and the average value waveform d, and only when the peak value waveform C is large,
The differential amplification output g is input to the second detection circuit 9.

Therefore, when the above relationship (a) is established, it is detected as a flame, and the output signal ftg from the detection circuits 8, 9 and level detection circuits jG10, 11 is input to the AND circuit 12, and the output signal i from the AND circuit 12 is input to the integration circuit 13. When the output i from the AND circuit 12 continues for a certain period of time, the level detection circuit 14 detects the integral output signal i, and when the integral amount reaches the set value, the integral circuit 13 detects the integral output signal i. The alarm output circuit 1 is activated, and the receiver, alarm device, warning light, etc. are activated.

In addition, in the case of a rotating lamp, as shown in FIG. 3, the relationship between the average value waveform d and the peak value waveform e detected by the second detection device 4 and the third detection device 5 is the same as in the case of flame detection. Conversely, the differential output of the first differential amplifier 6 is transmitted to the first detection circuit 8.
There is no output to the first level detection circuit 10, there is no output from the AND circuit 12, and the alarm output circuit 15 is not activated.

In addition, in the case of light that does not change (DC light), the peak value and the average value are the same and have no relationship in magnitude, and the second level detection circuit 1
1, there is no output, and the alarm output circuit 15 does not operate.

Also, 100Hz, like a light bulb that is lit by a commercial AC power source.
Alternatively, in the case of shallowly modulated light of 120 Hz, the flickering component characteristic of flame is distributed between 1 and 30 Hz, so the photoelectric conversion device 1 and automatic gain control amplifier 2 pass only the low frequency component and amplify it, thereby preventing malfunction. prevent.

Note that when unchanging light and light that changes slightly exist at the same time, the detection conditions for a flame may be met as is, but if the change is large, that is, the frequency is low, the change is absorbed by the time constant that the automatic gain control amplifier responds to. Do not malfunction.

In addition, in level detection times 1M10 and 11, the difference between the peak value and the average value, and the difference between the average value and a predetermined value below the peak value, for example, the peak value, is detected because the level of the differential output is detected. It is possible to set the range in which a difference is detected, and since the magnitude of this difference is seen in absolute value, the absolute value of the difference will also be small in the case of small light that is not subject to automatic gain control. It becomes difficult to detect, and unless it is clearly detected as a flame, it is difficult to detect and will not malfunction.

Further, the predetermined value detected by the third detection device 5 is not limited to the shame peak value proportional to the peak value, but may be set appropriately depending on the conditions of the setting location.

Furthermore, by photoelectrically converting only infrared light in the photoelectric conversion device 1, the influence of illumination light containing a large amount of visible light can be reduced, and since the flame emits a large amount of infrared light, detection can be ensured. Can be done.

According to the present invention, the peak value, average value, and predetermined value below the peak value of the photoelectric conversion output waveform of the photoelectric conversion device are detected by the first, second, and third detection devices, respectively, and the first,
Since the flame is detected based on the predetermined size relationship between the second and third detection devices, there is no risk of erroneously detecting illumination light, etc. because the change in light from the flame is captured as the degree of modulation of the flicker component unique to the flame. It is particularly suitable for flame detectors installed along roadsides of automobiles.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of a flame detector showing an embodiment of the present invention, FIG. 2 is a timing chart for detecting the same flame, and FIG. 3 is a timing chart for detecting light from a rotating lamp. 1...Photoelectric conversion device, 3...First detection device, 4...Second detection device, 5...
-Third detection device.

Claims (1)

[Claims] 1. A photoelectric conversion device that photoelectrically exchanges light emitted from a flame, a first detection device that detects the peak value of the photoelectric conversion output waveform of the photoelectric conversion device, and a second detection device that detects the average value of the output waveform. a detection device; a third detecting device for detecting a predetermined value proportional to the peak value of the output waveform and less than or equal to the peak value;
What is claimed is: 1. A flame sensor comprising: a detection device; the flame detector is configured to detect a flame based on a predetermined size relationship of each of the first, second and third detection devices.