KR830000882Y1 - Ignition and flame detection device for burner combustion control system - Google Patents

Abstract

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Description

Ignition and flame detection device for burner combustion control system

1 is a circuit diagram of a conventional ignition and flame detection device having a neon lamp for a combustion control system of a burner.

2 is a voltage and current waveform diagram of each part of FIG.

3 is a circuit diagram of an ignition and flame detection device for a combustion control system of a burner according to the present invention.

4A and 4B are voltage and current characteristic diagrams of a bidirectional thyristor having a neon lamp and two terminals.

The present invention relates to an ignition and flame detection device used in a burner combustion control device.

In general, the ignition is ignited by discharging a high voltage by a pulse ignitor between a discharge electrode and a burner.

On the other hand, flame detection is performed by applying an AC voltage between the flame detection electrode and the burner installed in the flame to detect the DC voltage obtained by the rectifying effect of the flame, and requires two electrodes.

Recently, a safflower and flame detection device in which the discharge electrode and the flame detection electrode as described above are shared. They are equipped with neon lamps for bypassing spark current to protect the flame detection circuit from high voltages for ignition. However, these neon lamps have a poor voltage response, which causes discharge error, which may cause an ignition signal even though they are not ignited. In addition, this type of device has a low flame current because the circuit configuration does not take a high applied voltage to the flame for flame detection. Therefore, it was difficult to discriminate from the spark discharge current for ignition, so that flame detection was difficult. In particular, since the flame current is further reduced when combined with a bad commutation burner, the application range of the ignition and flame detection device has been narrowed.

A conventional example provided with such a neon lamp will be described with reference to FIGS. 1, 2 and 4.

In Fig. 1, 1 is a burner, 2 is a flame, and 3 is an electrode, which serves as a discharge electrode and a flame detection electrode. 4 is a pulse transformer to generate a high voltage for ignition. 5 is a well-known pulse generating circuit, which is combined with the transformer 8 to generate a high voltage by the pulse transformer 4 in reverse phase with a flame current described later. For example, it is obtained by the connection direction of the transformer 8. 6 is an ignition switch and 7 is a commercial AC power supply. 8 is a flame detection transformer, 9 is a resistor, and 10 is a capacitor, and these constitute an applied AC voltage.

11 is a neon lamp. 12 has the effect of stabilizing the input impedance to the low-pass filter circuit as a resistance to reduce the effect of insulation degradation occurring between the electrode 3 and the burner (1). 13 is a resistor and 14 is a capacitor, and these constitute a low pass filter circuit.

15 is a well-known flame detection circuit that detects a negative voltage obtained by the flame rectifying effect and determines the presence or absence of a flame. 16 supplies a current to the flame detection circuit 15 as a direct current power source. The operation of this configuration will be described. The secondary voltage of the transformer 8 is applied to the burner 1 by the electrode 3 via the resistor 9, the condenser 10, and the pulse transformer 4.

When the ignition switch 6 is turned on, the pulse voltage in the pulse generating circuit 5 is boosted by the pulse transformer 4 to perform flame discharge between the electrode 3 and the burner 1. At this time, the spark discharge current flows between 4-3-2-1-11 and the neon lamp 11 discharges to bypass the high voltage. When the flame is formed by ignition by the high voltage discharge, the alternating current applied by the transformer 8 is rectified by the flame, and the rectified current (hereinafter referred to as flame current) flows in the direction of 3-2-1. This flame causes the condenser 10 to be charged so as to be the toothed side toward the resistor 13. This DC voltage is taken out of the low pass filter and detected by the flame detection circuit 15. The ignition switch 6 is turned off after ignition. This is the operation when the neon lamp 11 is discharged normally. Figure 2 shows the voltage and current waveforms of each part at this time. a is a waveform of the secondary output voltage of the transformer 8; b is the flame discharge current waveform of the pulse transformer 4 flowing through the electrode 3; If there is no flame, the voltage of the waveform indicated by c appears at both ends of the neon lamp 11. d shows the waveform of the flame current which flows through the electrode 3. As shown in FIG. e is a voltage waveform appearing at both ends of the neon lamp 11 when there is a flame. f is a smooth voltage waveform of e in the low pass filter. That is, when the ignition switch 6 is turned on, the input voltage of the flame detection circuit is positively biased at point P under the influence of the spark discharge current.

At the point Q, as shown by n in FIG. 2 (f), it is sub-biased by the flame current as the flame 2 is formed. m is the ignition detection level of the flame detection circuit 15, and the ignition signal comes out at R point.

The discharge time by the pulse transformer 4 is very short, and since the neon lamp 11 is discharged only by this voltage, the discharge time is very short and the discharge of the capacitor 10 is very small. Therefore, when the neon lamp 11 discharges normally, since the input voltage to the flame detection circuit 15 is positively biased at the time of discharge, no malfunction occurs. However, when the neon lamp 11 is not discharged, the spark discharge current flows through the resistor 9, the capacitor 10, or the resistor 13 and the capacitor 14. This current tends to flow from the electrode 3 to the burner 1 due to the settling rectification effect due to the shape difference between the burner 1 and the electrode 3, and also the capacitors 10 and 14 are moved. It is intervening. Therefore, even if there is no flame 2, these capacitors are charged so that the side toward the resistor 13 is negative, so that the input voltage to the flame detection circuit 15 is also negatively biased. If this is a size exceeding the ignition detection level (m), the ignition signal is issued and malfunctions. The discharge error of the neon lamp 11 has a large rise characteristic of the high voltage by the pulse transformer 4. In other words, because the dv dt is large, the electron emission from the boat is not able to follow the voltage rise.

In addition, as shown in FIG. 4A, the neon lamp had a low discharge start voltage, so that the flame detection voltage could not be increased.

As described above, when a neon lamp was used as a bypass for the spark discharges for ignition, malfunction or detection was difficult.

The object of the present invention is to prevent malfunction and at the same time to easily improve the flame detection sensitivity. The purpose of this is to use a two-way two-step thyristor instead of a neon lamp.

Hereinafter, the present invention will be described by the embodiment shown in FIG. The difference between the first and second degrees lies in that the neon lamp is a two-way two-step thyristor (hereinafter referred to as SSS) 17.

The SSS 17 conducts and bypasses by spark discharges for ignition.

Since the SSS 17 is a semiconductor element, the rising characteristic is also good, flows the flame discharge reliably and does not cause malfunction. 4 is a diagram showing the difference between the neon lamp and the SSS. In general, since the breakdown voltage at which the current starts to flow is about twice that of the neon lamp, the value of the resistor 9 may be reduced to increase the high current voltage applied between the burner 1 and the electrode 3. As a result, the flame current increases, and the difference between m and n can be increased, making it easy to detect.

The resistor 9 serves to prevent the discharge of the electric charge due to the flame current charged in the capacitor 10 when the SSS 17 breaks down due to the discharge. The reduction of the time constant by reducing the value of the resistor 9 can be easily compensated for by increasing the value of the capacitor 10.

In addition, the SSS has a high breakdown voltage, and when the current reaches a certain value or more, the current voltage almost disappears, and the internal resistance is severely reduced. For this reason, the discharge current flows very easily, and when the pressure voltage n to the flame detection circuit 15 is positively biased by the discharge, it is greatly reduced, and the flame current can be easily detected.

As described above, according to the present invention, since the two-way two-terminal thyristor is used as a bypass for the spark discharge current for ignition, the rising characteristic is good and the flame current is high, and the reverse bias phenomenon due to the spark discharge flow can be easily obtained. Since there is no malfunction, there is no malfunction and the flame can be easily detected.

Claims (1)

Means for bypassing the spark discharge current for ignition on the secondary side of the pulse transformer generating high voltages for electrodes and ignition, and a burner are installed in series, and the secondary side of the flame detection transformer, a resistor and a capacitor are provided in series. In the ignition and flame detection device provided with the flame detection circuit which detects the smoothing current by providing a low-pass filter which smoothly arranges the voltage obtained at the both ends of a bypass means, and arrange | positions in parallel with the means of bypassing the latter series circuit. An ignition and flame detection device, characterized in that a two-way two-terminal thyristor (17) is used as the bypassing means.