JPS59112118A - Flame detecting circuit - Google Patents

Abstract

PURPOSE:To provide a flame detecting circuit which prevents the occurrence of malfunction due to pulsation and has a rapid response time, by a method wherein flame detection is effected by cutting a pulse, the pulse width thereof is smaller than a predetermined value, out of pulses detected by a flame detecting means. CONSTITUTION:A pulse at a point B from a flame detecting part A is inputted to an input part CL1 of a first one-shot multi-vibrator 16 through an AND circuit 18, and similarily, the pulse at the point B is connected to one input terminal of an AND circuit 21 through a delay circuit consisting of a resistor 19 and a capacitor 20, and the output of the first one-shot multi-vibrator 16 is introduced to other input terminal of the AND circuit 21 through a NOT circuit 22. A resistor 23 and a capacitor 24 determine the width of a pulse generated by the first one-shot multi-vibrator 16, and similarily, a resistor 25 and a capacitor 26 determine the width of a pulse generated by a second one-shot multi-vibrator 17. This permits stable and reliable detection of the flame.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flame detection circuit that prevents erroneous outputs caused by the above and obtains accurate flame detection signals.

A flame detection circuit is required for the starter flame of gas appliances as a safety measure to prevent gas explosion accidents. This flame detection means is called the flame rod method. According to this method, a pair of electrodes is provided at the position where they come into contact with the flame, and they are placed facing each other. The device is configured to detect the presence or absence of flame by detecting the direct current from the power source.

The principle of operation of this type of detection circuit is to detect a weak conductive current by utilizing the rectification effect caused by the presence of a flame, and to detect the flame through an amplifying means. Moreover, since the flame is a conductive effect, the detection signal is not a pulsating flow, and it is necessary to distinguish the detection signal that accurately indicates the presence of a flame from within this pulsating flow.

In other words, there are changes in the physical properties of the flame detection electrode due to long-term combustion, carbon deposits on the detection electrode as a result of combustion, changes in insulation resistance depending on the type of combustion gas, and furthermore, there are changes in the flame detection electrode. This is because false flame signals exist within the detected pulsating flow due to various causes such as the influence of fluctuations.

Therefore, in the past, a method of inserting a capacitor with a large capacity was used to remove the above-mentioned false flame signals, but this method reduces the delay time (2 to 3 seconds) when flame is detected and when flame disappears. Furthermore, if the voltage accuracy of the power supply voltage is not sufficient or if the insulation resistance of the flame rod part is low, there is a risk that ripples will be superimposed when the flame disappears and malfunction will occur.The present invention solves the above problems. The purpose of this invention is to provide a flame detection circuit that does not malfunction due to pulsating currents caused by flames and has a fast response time.

In the present invention, changes in the physical properties of the detection electrode, fluctuations in the flame,
Based on the knowledge that pulsating currents (hereinafter referred to as pulses) generated under the above-mentioned conditions have a narrow response width, a waveform processing circuit is used to detect the pulsating currents (hereinafter referred to as pulses) by the flame detection means and select a predetermined number from among the pulses. Force a pulse of less than O217 width,
The present invention is intended to enable flame detection without erroneous output. Examples will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of a flame detection circuit according to the present invention. The flame detection circuit shown in FIG. 1 consists of a flame detection section A and a waveform processing section B. Note that the flame detection section shown as A can be applied to any detection means, even if flame detection is performed by flame. Based on the drawing attached to the application for utility model registration.

Therefore, regarding the flame detection section A, only the generation of pulses due to flame detection will be functionally explained.

Now, if there is no flame at the fuel discharge port 1, the circuit between the flame detection electrode 2 and the fuel discharge port 1 is in an OFF state, and the deer) is also in the secondary side of the transformer 4 in combination with the OFF state of the surge absorption element 3. No circuit is formed. The force (due to the power supply) is applied to the base of the range star,
PNP) The Darlington circuit by Lannostars 6 and 7 is off. Therefore, the potential of the positive terminal of the operational amplifier 8 due to the 0 point becomes lower than the reference voltage of the negative terminal 1j via the power supply Vc and the variable resistor 9, and the output of the operational amplifier 8 becomes "L" level.

On the other hand, when there is a flame at the fuel discharge port 1, two circuits of the transformer 4 are formed due to the conductive action of the flame, and a rectified half-wave current flows through the secondary winding of the transformer. Moreover, at this time,
Due to the current flowing through the resistor 12 and the relay 913, the base potential of the transformer soster 6 is lowered.
The Darlington circuit is turned on, and an amplified current flows through the resistors 14 and 15, raising the potential at point 2. As a result, the input voltage of the operational amplifier 8 rises above the reference voltage, and the output of the operational amplifier 8 is inverted to the rHJ level.

Thus, the output of the operational amplifier 8 becomes a pulse output waveform shown at the zero point. Note that the above explanation only concerns the generation of pulse output, and other details are omitted. That is, in the present application, the problem is waveform processing regarding the waveform.

Next, the configuration and operation of the waveform processing section B will be explained. First, the waveform processing section B is composed of a first one-shot multi 16 and a second one-shot multi 17. Then, the 0-point signal from the flame detection section A is inputted to the input section CL1 of the first one-shot multi 16 via the AND circuit 18. Similarly, the pulse at the 0 point is connected to one input terminal of an AND circuit 21 via a delay circuit consisting of a resistor 19 and a capacitor 20, and is further connected to the other input terminal of the AND circuit 21 via a NOT circuit 22. The output of one-shot multi 16 is introduced. A resistor 23 and a capacitor 24 determine the pulse width generated by the first one-shot multi 16, and a resistor 25 and a capacitor 2
6 is generated by the second one-shot multi 17.
and rus width.

FIG. 2 is a waveform diagram for explaining the operation. In Fig. 2, the arrow t is the time axis and indicates the direction of time, and the line up to the dotted line (A) indicates the ignition state, and the line between (A) and (B) indicates the steady combustion state, and the dotted line (R) indicates the ignition state. ) From here on, the extinguishing state is shown in detail9, and for convenience, these are written in series along the time axis. Therefore, to explain the operation with reference to a waveform diagram, the 0 point waveform from the flame detection section A becomes the input to the first one-shot multi 16 in its "IT" state, and the pulse width T1 determined by the resistor 23 and capacitor 24. A pulse train having the following values is output (Fig. 2). This output is NO
It is inverted by the T circuit 22 and becomes the other input of the AND circuit 21 (FIG. 2). Further, the 0-point guru waveform is delayed through a delay circuit including a resistor 19 and a capacitor 20, and is input to one side of an AND circuit 21. This is because the phase is matched to the pulse width generated by the first one-shot multi 16 (FIG. 2). AND circuit 21
The second figure is shown ■.

The waveform of ■ is input, and the second
Since it becomes the input of the one-shot multi 17, its input waveform is shown as 9 in FIG. 2, and its output is as shown in 2 in FIG. Therefore, the pulse within the pulse width T1 determined by the first one-shot multi 16 can be removed, and the
Only pulses with R pulse width (and only if it is certain that a flame is present) will generate an output. Furthermore, if there is flame fluctuation, a missing portion of the pulse will occur, but malfunction can be prevented by the presence of the time width of the pulse generated from the one-shot multi-shot.

As a result, the response time is now 20m5e, compared to the conventional 3sec.
It was confirmed that there was no malfunction when the insulation deterioration of the frame rod reached 300 MΩ, and furthermore, there was no malfunction until the ripple amount reached 10 m5ec.

As stated at the beginning, the configuration of the flame detection section is not limited to that shown in this embodiment, and can be applied to any configuration as long as flame detection is performed using pulsating flow. .

As explained above, according to the present invention, flame detection is detected as a pulsating flow, and then waveform processing is performed, and pulses with a predetermined pulse width or less are
Since the flame detection circuit is configured so as to detect flames stably and reliably, it is also possible to provide a flame detection circuit with extremely high responsiveness.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of one embodiment of the flame detection circuit according to the present invention, and FIG. 2 is a waveform diagram for explaining the operation. 1. Fuel discharge port, 2 Flame detection electrode, 3. Surge absorption element, 4. Transformer, 5.20, 24.2
6 ・Condenser 9 6.7-... Transistor, 8 Operational amplifier, 9.12, 14, 15, 19, 23.25 ・
...Resistance, 10...Neon tube circuit, 11.Secondary winding, 13.Diode, 16.17...-One-shot multi, 18.21...
AND circuit, 22-knot circuit. Patent applicant Mikuni Kogyo Co., Ltd. Agent Patent attorney Norio Ishii 87

Claims (1)

[Claims] In a flame detection circuit that digitally detects a flame using a flame rod method, by introducing a digital signal detected by a flame into a waveform processing section, an output pulse having a predetermined pulse width or less is removed, and an output pulse having a predetermined pulse width or less is removed. A flame detection circuit characterized in that only the above output/gurus is derived as a flame detection signal.