JPS6137979Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an ignition device used in, for example, an oil burner, and in particular aims to reduce the size of the ignition device, improve low-temperature ignition characteristics, and stabilize performance.

FIG. 1 shows a conventional example of an ignition device. A bidirectional thyristor, or so-called triac, 2 is connected in series to both ends of an AC power source 1, a main capacitor 3, and a series circuit of a primary winding 5 of a transformer 4. An oscillation capacitor 6 and charging resistors 7 and 8 are also connected.
The series connection with the series circuit of the above is also connected to both ends of the AC power source 1. The connection point of the oscillation capacitor 6 and the charging resistor 7 is connected to the control terminal of the triac 2 via a trigger switch element 9, and the connection point of the triac 2 and the main capacitor 3 is connected to the connection point of the charging resistors 7 and 8 via a feedback resistor 10.
Both ends of the secondary winding 11 of the transformer 4 are used as output terminals. The oscillation capacitor 6, charging resistors 7 and 8, and trigger switch element 9 constitute a relaxation oscillation circuit that controls the triac 2, and the oscillation capacitor 6 and charging resistors 7 and 8 form a time constant circuit of the oscillation circuit.

In this device, when an AC voltage as shown in Fig. 2A is applied from the AC power supply 1, the oscillation capacitor 6 is charged from time _t0 with a time constant determined by the relationship with the charging resistors 7 and 8, and when the terminal voltage reaches the breakover voltage of the trigger switch element 9 at time _t1 , the trigger switch element 9 breaks over, and the charge in the oscillation capacitor 6 is discharged through the trigger switch element 9 and the control terminal of the triac 2, turning on the triac 2. When the triac 2 turns on, the charge is discharged from the power supply 1 to the triac 2, the main capacitor 3 and the transformer 4.
A pulse current flows through the primary winding 5 of the transformer 4, generating a pulse voltage in the primary winding 5 of the transformer 4 and a high voltage pulse voltage in the secondary winding 11 of the transformer 4. The voltage across the triac 2 rises between time points _t0 and _t1 as shown in Fig. 2B, and is zero during the turned-on period _t1 to _t2 . This pulse current of the triac 2 generates a resonant voltage between the primary winding 5 and the main capacitor 3 between time points _t2 and _t3 , turning the triac 2 off, the AC voltage becoming negative, and when the negative voltage of the oscillation capacitor 6 reaches the breakover voltage of the trigger switch element 9 at time point _t4 , the switch element 9 and the triac 2 turn on again, and the above process is repeated.

Recently, electronic type ignition of oil burners and the like has come to be widely used. Compared to the conventional transformer type, the electronic type allows the device to be lighter and smaller, but on the other hand,
Discharge energy is small. On the other hand, at low temperatures such as during the cold season, kerosene becomes difficult to vaporize and ignition is difficult due to factors such as an increase in the discharge starting voltage at the electrodes. Therefore, if the discharge energy of the ignition device was increased, the device would become larger and the cost would increase.

In the conventional ignition device shown in FIG. 1, in order to increase the discharge energy, it was necessary to increase the size due to problems such as temperature rise.

The purpose of this invention is to solve such problems by providing an ignition device that increases the discharge energy of the ignition device only at low temperatures, does not reduce the ignition performance at low temperatures, and can be constructed in a small size. According to this invention, a temperature-sensitive resistance element is provided in the time constant circuit of the relaxation oscillator circuit for controlling the thyristor, so that the firing angle automatically increases as the temperature decreases.

FIG. 3 shows an embodiment of this invention, and parts corresponding to those in FIG. 1 are given the same reference numerals. In this embodiment, a negative temperature coefficient temperature sensitive resistance element 12 is connected in parallel with the charging resistor 7, and a resistor 13 is connected in parallel with the oscillation capacitor 6.

In the ignition system shown in FIG.
Resistor 13, charging resistor 7, 8, temperature sensitive resistance element 1
It is determined by the time constant determined by 2. However, at low temperatures, the temperature coefficient of resistance of the temperature-sensitive resistance element 12 is negative, so the resistance value increases, and therefore the time constant increases. Therefore, the phase of the trigger of triator 2 is delayed, i.e. from time t ₀ in FIG. 2A to
The so-called firing angle between t ₁ and The generated pulse voltage increases, and a large high-voltage pulse voltage is generated in the secondary winding 11 of the transformer 4, so that large discharge energy is obtained.

When the device shown in FIG. 3 is used continuously, as the temperature of the device rises due to self-heating, the resistance value of the temperature-sensitive resistance element 12 decreases, and the time constant and firing angle become small. The discharge energy decreases somewhat. However, once an oil burner is ignited, it continues to burn, so combustion can be sustained even with somewhat less discharge energy.

When this ignition device is used at room temperature, the discharge energy does not need to be as large as at low temperatures, and the time constant is selected so that the device's capacity is about the same as that of conventional devices. .

FIG. 4 shows another embodiment of this invention, in which the relaxation oscillation circuit is connected directly to the power source 1 in FIG. 3, but it is connected via the primary winding 5 of the transformer 4. In other words, the power supply 1 side of the charging resistor 8 is connected to the power supply 1 side of the transformer 4.
Connect to the connection point of the secondary winding 5 and the main capacitor 3. Its operation and effect are exactly the same as in the case of FIG.

FIG. 5 shows an example in which a positive temperature coefficient temperature sensitive resistance element is used instead of a negative temperature coefficient temperature sensitive resistance element. In the configuration shown in FIG. Connected. This device also exhibits effects similar to those shown in FIG.

As mentioned above, in this invention, the time constant circuit in the relaxation oscillation circuit that controls the thyristor,
By providing the temperature-sensitive resistance element, the time constant of the time constant circuit automatically increases at low temperatures, the ignition angle increases, the discharge energy increases, and ignition can be ensured. Moreover, when the temperature of the ignition device is high due to a rise in ambient temperature, the time constant of the relaxation oscillator circuit becomes smaller, which reduces the firing angle of the thyristor and reduces the current flowing through the primary winding of the transformer, reducing the temperature rise is suppressed. Additionally, when the ambient temperature rises, the characteristics of the triac change, and the maximum value of the critical voltage increase rate dv/dt during commutation decreases, making it difficult to turn off the triac even if a reverse voltage is applied to the conducting triac. However, the firing angle becomes smaller due to the action of the temperature-sensitive resistance element, and dv to dt of the voltage waveform applied to the triax also becomes smaller, so that erroneous firing can be prevented. Even if erroneous ignition occurs and the power is turned on more than once in a half cycle,
Since the firing angle caused by the first signal is small, the amount of charge to the main capacitor 3 is small, and even if the next signal fires again, the current value flowing through the primary winding 5 is suppressed, and the temperature rise of the device is small. Therefore, it can be configured to be compact.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing a conventional example of an ignition system;
The figure is a waveform diagram for explaining the operation of the ignition device, and FIGS. 3 to 5 are circuit diagrams each showing an embodiment of this invention. 1... AC power supply, 2... Triax as a thyristor, 3... Main capacitor, 4... Transformer, 5... Primary winding, 6... Oscillation capacitor,
7, 8... Charging resistor, 9... Trigger switch element, 10... Feedback resistor, 12, 14... Temperature sensitive resistance element.

Claims (1)

[Claims for Utility Model Registration] (1) A series circuit of a thyristor, a main capacitor, and a primary winding of a transformer is connected to both ends of an AC power supply, and a relaxation oscillation circuit is connected to both ends of the power supply. The main capacitor is connected through a feedback resistor, and the output terminal of the relaxation oscillation circuit is connected to the control terminal of the thyristor, and the point of the thyristor is connected to the control terminal of the thyristor by a time constant of a time constant circuit that determines the oscillation period of the relaxation oscillation circuit. In an ignition device in which the arc angle is determined and a high voltage pulse for ignition is obtained in the secondary winding of the transformer by conduction of the thyristor, a temperature-sensitive resistance element is provided in the time constant circuit, and when the temperature decreases, the above-mentioned An ignition device characterized in that the time constant is selected to be large due to a change in the resistance value of the temperature-sensitive resistance element. (2) The ignition device according to claim 1, wherein the temperature-sensitive resistance element is an element having a negative temperature coefficient of resistance and connected in series with the capacitor of the time constant circuit. (3) The ignition device according to claim 1, wherein the temperature-sensitive resistance element is an element having a positive temperature coefficient of resistance and connected in parallel with the capacitor of the time constant circuit. (4) The relaxation oscillation circuit is connected to the alternating current power source via the primary winding of the transformer. Ignition device as described.