JPS60250219A - Flame detector - Google Patents

Abstract

PURPOSE:To obtain a fire alarm of simple construction, compactness and detection precision, by detecting not only flickering characteristic to a flame, but also ignition. CONSTITUTION:An output signal B is obtained in the full-wave rectifying circuit 6 by an output A concerning a range of 3-20Hz characteristic to flickering of flame from intrared-ray detecting unit 2 and selective amplifier 4. Further, the signal B is introduced into No.1 and No.2 comparators 8, 10 to compare threshold values X, Y of flickering and ignition detections respectively and signals C, D are issued in such a way that when the signal B is smaller than the threshold values X, Y, the H level is selected and when larger the L level is selected. Further, when the signal rises from L to H, a signal C is integrated by setting of an integrating circuit 12 by a controlling circuit 14 and after the specified time (t) a resetting signal is issued to stop the integration action. Further, an output signal E is compared with a threshold value Z and when the signal E exceeds the threshold valve Z, a output signal F is reversed from L level to H level to issue a flame detection signal.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a flame detector used to detect fire outbreaks at gas stations and the like.

Prior Art Conventionally, there are two known flame detection devices: one that detects the radiant heat from the flame and the other that photoelectrically detects the radiant light from the flame.The latter is preferred in terms of responsiveness and reliability. Are better. For example, Japanese Patent Publication No. 38-3727 and No. 3
Publication No. 9-364 proposes a photoelectric flame detector that converts radiant light from a flame into an electrical signal using a photoelectric conversion element, and detects flickering characteristic of the flame from the signal. .

However, such a device has the drawback that even if it receives light from a light source whose light intensity changes periodically, such as a fluorescent lamp, it will be detected as a flame. Therefore, JP-A-53-6
In Publication No. 6776, the output signal from the photoelectric conversion element is divided into an alternating current component and a direct current component, and a flame is detected only when the direct current component is present and does not change, and the alternating current component changes continuously. A device has been proposed. According to this device, when the direct current component of the output signal of the photoelectric conversion element changes, such as the light of a rotating lamp, it is no longer falsely detected as a flame, and the detection accuracy is improved. However, this device requires a circuit that separates the output signal of the photoelectric conversion element into an alternating current component and a direct current component, resulting in a complicated configuration. In particular, if a pyroelectric detector is used as a photoelectric conversion element, which is inexpensive and has sufficient sensitivity for the flame-specific wavelength (for example, 43 μm), the incident light is A chopper is required to periodically change the amount of water, which complicates the configuration and increases the size of the device.

Purpose The present invention has been made in view of the above-mentioned points, and its purpose is to provide a flame detector that is simple and compact in structure and has good detection accuracy.

Embodiment FIG. 1 is a block diagram showing an outline of an embodiment of the present invention. In the figure, (2) is an infrared detection section, which outputs an electric signal corresponding to infrared rays having a wavelength (for example, 43 μm) unique to flames among the light from the range to be measured. Therefore, the infrared detection section (2) has a photoelectric conversion element that is sensitive in the infrared region. In this embodiment, this photoelectric conversion element is a pyroelectric infrared sensor that outputs an electrical signal according to the amount of change in the intensity of infrared rays. However, before this sensor,
An optical system that collects light from the range to be measured and makes it perpendicularly enter a band-pass filter that transmits a wavelength unique to the flame, and makes only the light emitted perpendicularly from the filter enter the sensor. The placement is sagging.

This optical system was first applied for in the patent application filed in 1988-8 by the applicant.
This was proposed in No. 1978. Note that instead of the pyroelectric infrared sensor of this embodiment, a photovoltaic element or a light-receiving element having sensitivity at the above wavelength may be used, but in that case, a filter that cuts the DC component is required.

The output signal from the infrared detection section (2) is sent to the selective amplification circuit (
4). Here, the frequency characteristics of the pyroelectric infrared sensor are as shown by b in Fig. 2 at 1 Hz Jl, while the frequency characteristics of the selection tank l] circuit (4) are as shown by a in Fig. 2. is set to . Therefore, the output frequency characteristic of the selective amplification circuit (4) with respect to the infrared intensity detected by the infrared detection section (2) is as shown in C in FIG.

5- That is, the selective amplification circuit (4) outputs an output that is selectively amplified only in the frequency band of 3 to 20 Hz that is specific to flame fluctuations. In other words, the frequency characteristics of the pyroelectric infrared sensor and the increase 1] frequency characteristics of the selective amplification circuit (4) create a frequency range (3 to 20
Only the signals of Hz) are selectively amplified. Output A of selection tank 11 circuit (4) is full wave rectifier circuit (6)
The aftermath is rectified at , and becomes the output signal B.

This aftereffect rectifier circuit (6) is provided in a subsequent circuit for easy signal processing.

The output signal B of the aftermath rectifier circuit (6) is sent to the first comparator (8).
and the second comparator (10), respectively. 1st
The comparator (8) compares this output signal B with a predetermined first threshold value X for fluctuation detection, and when B is smaller than X, it becomes "H" level, and B is larger than X. At times, it outputs a signal C that is at the "L" level. on the other hand,
A second comparator (10) compares the output signal B of the aftermath rectifier circuit (6) with a second threshold value Y for firing detection, and
When B is smaller than Y, it outputs a signal that is at the "H" level, and when B is larger than Y, it outputs a signal that is at the "L" level.Here, the second threshold Y is lower than the first threshold X. It is set high.

The output signal C of the first comparator (8) is:
2). When the integration circuit (12) receives a set signal from the control circuit (14) described later, it performs a certain amount of integration every time the signal C becomes "L" level, and performs a reset from the control circuit (14). The signal resets the integral. The control circuit (14) sends a set signal to the integral quantity 1# (12) when the output signal of the second comparator (10) rises to the "H" level after reaching the "L" level. The control circuit (14) sends a reset signal to stop the integration operation of the integration circuit (12) when a predetermined period of time has elapsed since the generation of this set signal. The output signal E of 12) is
After the set signal is input, the level is increased by a certain amount in accordance with the fall of signal C, and the integrated amount is determined by the control circuit (
It is cleared by the reset signal from 14).

The third comparator (16) compares the output signal E of the integrating circuit (12) with a predetermined third threshold value Z, and when E exceeds 2, the output signal ゛F becomes ``L''. ``level'' is reversed to ``H'' level. This output signal F is used as a flame detection signal to activate an alarm signal generation circuit.

That is, in this embodiment, the first comparator (8) acts as a fluctuation detection means for detecting flame fluctuation;
The comparator (10) acts as an ignition detection means for detecting ignition. Furthermore, an integrating circuit (12) and a control circuit (14)
) acts as a counting means for counting the number of flame fluctuations within a predetermined time period after ignition is detected, and the third comparator (J6) determines whether there is a flame or not according to the count value. It acts as a determining means.

FIG. 3 shows the detailed configuration of this embodiment. In FIG. 3, (18) is a pyroelectric infrared sensor in the infrared detection section (2). The radiant energy from the flame at the time of ignition is the fourth
As shown in the figure, it has a shape in which the fluctuation energy consisting of an AC component with a frequency of 3 to 20I (z) is superimposed on the average energy of the DC component. The output signal of the pyroelectric infrared sensor (18) that receives radiant energy from such a flame is as shown in Figure 5. That is, as is clear from comparing Figures 4 and 5, the pyroelectric infrared sensor (18) The output of the sensor (18) fluctuates greatly when igniting, and when the flame is burning steadily, it becomes an AC signal that fluctuates at the same frequency as the fluctuation of the flame.For example, when gasoline ignites, it is constantly burning. In the case of alcohol, the output is about three times that of the previous one, and about twice as much in the case of alcohol.In this embodiment, only when this large output fluctuation at the time of ignition and the following flame fluctuations are detected a predetermined number of times, It is detected as a flame.Therefore, in this embodiment, malfunctions due to single large noises or continuous noises do not occur.

Returning to FIG. 3, the output signal of the infrared detection section (2) is transmitted through a selective amplification circuit (4) having operational amplifiers (20) (22).
The signal A is selectively amplified by . Here, the signal A is obtained by selectively amplifying only the frequency range of 3 to 20 Hz of the infrared rays incident on the pyroelectric infrared sensor (18). This situation is shown in FIG.

In Figure 6, (a) is the output signal when a flame occurs.
9- is a time chart showing changes in No. 9-F. Figure 6 (
1)) is the output signal A when a single large noise occurs
-F, and FIG. 6(C) shows the change in the output signal A-F when continuous noise having a frequency approximately equal to the flame fluctuation occurs. The output signal A of the selective amplification circuit (4) is subjected to aftereffect rectification by the aftereffect rectification circuit (6) and becomes a signal B. This signal B is input to the comparator (24) in the first comparison circuit (8) and the comparator (26) in the second comparison circuit (10), respectively. A predetermined voltage determined according to the set resistance value of the resistor (Rxr) and the variable resistor (RX2) is applied to the other input terminal of the comparator (24).

This voltage corresponds to the first threshold value X.

The comparator (24) compares the signal B with the first threshold value X, and becomes "H" level when B)X.
When this happens, a signal C that changes to "L"" level is output. Here, the first threshold value X is determined according to the amplitude of the output signal B due to flame fluctuation. Furthermore, the capacitor (
CI) makes the first threshold value X10- higher during the time from power-on to stabilization of the selective amplification circuit (4) to prevent an erroneous signal from being output from the comparator (24). belongs to.

On the other hand, a predetermined voltage determined by the resistor 1y ] ) and the set resistance value of the variable resistor (RV2) is applied to the other input terminal of the comparator (26). This voltage corresponds to a second threshold Y, which is higher than the first threshold X, as shown in FIG. The comparator (26) is
The signal B is compared with the second threshold Y, and when B(Y)
It outputs a signal that becomes 'H''' level and becomes 'L' level when B>Y.Here, the second threshold value Y
is determined according to the amplitude of the output signal B caused by firing. Further, the capacitor (C2), like the capacitor (C1) mentioned above, is used to prevent malfunction during the time from power-on to stabilization of the selective amplification circuit (4). Note that the first and second threshold values X and Y are each
It can be adjusted by changing the set resistance value of the variable resistance (Rx2) (Ryz).

As shown in FIG. 6(C), in the case of continuous noise, the signal B does not exceed the second threshold Y, so the comparator (
The output signal of 26) remains at "H" level.
The L″ level is not reversed. Therefore, it is distinguished from the case in which flames occur at the temple in Figure 6 (a). Figure 6 (a)
(1))+7) Then, when the output signal of the comparator (26) is inverted to the "L" level, the transistor (Tr) in the control circuit (14) becomes conductive in response to its fall.

As a result, the capacitor (C4) starts to be charged with -Vω, and the FET (28) is made non-conductive.
The integrating circuit (12) is activated.

The integrating circuit (12) is an FET in the control circuit (14).
When (2B) becomes non-conductive, the capacitor (C3) is charged by a predetermined amount each time the output signal C from the comparator (24) falls. Therefore, the output signal E of the integrating circuit (12) rises in a stepwise manner every time the signal C from the comparator (24) falls, as shown in FIG. here,
Although the output signal of the comparator (26) once goes to the "L" level, it immediately inverts back to the "H" level, but the charge accumulated in the capacitor (C4) keeps the FET (28) in a non-conducting state. Ru. While the transistor (Tr) is conducting, the capacitor (C4) is recommended to be charged, but when the time 4 determined by the resistor (R4) and the capacitor (C4) has elapsed since the signal rose. The charge stored in the capacitor (C4) is discharged and F ET (2B) becomes conductive. Then, the charge stored in the integrating capacitor (C3) is discharged through the FET (28), and the integrating circuit (12) is reset.

Output signal E according to the charging voltage of the integrating capacitor (C3)
is input to the comparator (30) in the third comparison circuit (16). A signal related to the third threshold value Z determined by the resistor (RZI) (RZ2) is input to the other input terminal of the comparator (30). A comparator (30) compares both human power signals E and Z with each other,
E) Outputs a signal F which inverts to "H" level when it reaches Z. Here, the third threshold Z is determined according to the frequency of fluctuations specific to the flame. Therefore, Fig. 6(b)
When a large single-shot noise occurs, the second comparator circuit (10) outputs a signal similar to that at the time of firing, but the output signal E of the integrator circuit (12) exceeds the third threshold value. 2
not exceed.

13- Therefore, it will not be mistakenly detected as a flame. The output signal F of the third comparator circuit (16) is used for warning and display when flame is detected.

In this embodiment, the count time of the control circuit (14) ÷ is l sec, and the third threshold value 2 is the output signal C.
If the amount of increase in the output signal E of the integrating circuit (12) due to one fall of is increased by about six times, the flame fluctuation component of 3 Hz a J: can be detected.

According to this embodiment, there is no malfunction caused by a single large noise as shown in FIG. 6(b) or continuous noise as shown in FIG. 6(C), so the accuracy is good.

Here, conventionally, in Japanese Patent Publication No. 43-28917, outputs exceeding a predetermined threshold value are counted among the alternating current components of the photoelectric conversion element that receives light from the range to be measured, and this count value is There is a known device that detects flame when it reaches a predetermined value.

However, in this conventional device, unless the threshold value (corresponding to the first threshold value X of this embodiment) is set high, it is not possible to distinguish between (a) and (c) in FIG. . However, if this threshold value is not set high, the flame detection sensitivity will decrease. According to this embodiment, even if the first threshold value X is set lower than that of the conventional device, if the second threshold value Y is set high for detecting firing, the sensitivity is reduced. Accuracy can be improved without

As described in ``Effects'', the flame detector of the present invention includes a photoelectric conversion means that is sensitive to wavelengths specific to flame, and an ignition detection means that outputs an ignition detection signal when ignition is detected from the output of the photoelectric conversion means. , characterized by comprising a fluctuation detection means for detecting flame fluctuation from the output of the photoelectric conversion means, and a flame detection means for detecting a flame according to an ignition detection signal and a fluctuation detection signal and outputting a flame detection signal. By configuring it in this way, flame detection is performed by detecting not only the fluctuations characteristic of flames, but also ignition.
It is possible to obtain a flame detector with a simple configuration, less false detection, and high detection accuracy. Further, since fluctuations and firing can be detected using only the AC component without having to separate the output signal of the photoelectric conversion element into DC and AC components as in the conventional example, the configuration becomes compact.

In particular, an inexpensive pyroelectric detector can be used as the photoelectric conversion means that detects only the alternating current component, and by using this, the device can be made inexpensive.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an outline of an embodiment of the present invention, Fig. 2 is a graph showing the pyroelectric infrared sensor and the 11 selective amplifier circuits, and frequency characteristics due to their connections.
The figure is a circuit diagram showing its configuration, Figure 4 is a graph showing the temporal change in radiant energy during ignition, Figure 5 is a graph showing the output change of the pyroelectric infrared sensor at that time, and Figure 6 is the book. It is a graph showing the output change at each point in the example. (2); Photoelectric conversion means, (8); Fluctuation detection means, (1
0); Ignition detection means, (12) (14) (16)
: Flame detection means. - Applicant Minolta Camera Co., Ltd. (b) (C) Z
−−−−−−−−−−−L L Procedural amendment July 25, 1980 Manabu Shiga, Director General of the Patent Office, Patent Application No. 107915 of 1989 2, Title of invention Flame detector 3, Make amendments Applicant Address 2-30 Azuchi-cho, Higashi-ku, Osaka Name of Osaka Kokusai Building (607) Minolta Camera Co., Ltd. Voluntary Amendment 6, Contents of Amendment (1) Second line from the bottom of page 2 of the specification, [ 1 at gas stations etc. will be corrected to ``outdoors''. (2) In the bottom 6th line of page 2 of the specification, the phrase "It is arranged." is amended to "It is arranged." (3) Page 6, line 10 of the specification, [provided]. ]
It is designed to make certain things happen. ] and correct it. Applicant: Minolta Camera Co., Ltd.

Claims (1)

[Claims] 1. A photoelectric conversion means that is sensitive to wavelengths specific to flame; an ignition detection means that outputs an ignition detection signal when detecting ignition from the output of the photoelectric conversion means; a fluctuation detection means for detecting fluctuation of the flame; detecting the flame according to the ignition detection signal and the fluctuation detection signal;
1. A flame detector comprising: flame detection means for issuing a flame detection signal. 2. The fluctuation detection means is a band offshore means that transmits only signals in a frequency range specific to flame fluctuations out of the output of the photoelectric conversion means, and compares the output with a preset first level and determines the comparison result. 2. The flame detector according to claim 1, further comprising first comparison means for outputting a corresponding first comparison signal. 3. The ignition detection means includes a second comparison means that compares the output of the band offshore wave means with a second level set in advance to be higher than the first level, and outputs a second comparison signal according to the comparison result. A flame detector according to claim 2, characterized in that the flame detector comprises: 4. A patent characterized in that the flame detection means starts counting the number of fluctuations by the fluctuation detection signal in response to the ignition detection signal, and outputs the flame detection signal when the fluctuation is detected a predetermined number of times within a predetermined time. A flame detector according to claim 1. 5. The flame detector according to any one of claims 1 to 4, wherein the photoelectric conversion means includes a pyroelectric detector.