JPH05688Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a multi-spark ignition device particularly suitable for use in igniting oil.

<Prior art> A self-excited thyristor series inverter circuit in which an ignition coil is used as a load to self-oscillate a thyristor series inverter circuit, and a high voltage generated on the secondary side of the ignition coil causes multiple sparks to fly between discharge electrodes. An inverter-type multiple spark ignition device is known from Japanese Patent Laid-Open No. 59-44523, which was proposed by the present applicant.

<Problem to be solved by the invention> In the above ignition device, a diode and a charging circuit are connected to both ends of the feedback winding that is magnetically coupled to the primary winding of the ignition coil, and the discharge current of the charging circuit causes The thyristor triggering and charging circuit of the thyristor series inverter circuit is comprised of a capacitor and an output energy adjustment resistor in parallel with the capacitor.

Therefore, when the voltage generated by the feedback coil is low (for example, when the input voltage of the AC power supply is low or the generated voltage is suppressed due to the influence of the secondary output side load),
If the resistance value of the energy adjustment resistor is set to a small value, the amount of charge charged to the intermittent trigger capacitor will be small, and the thyristor may not be able to reliably commutate, resulting in unstable operation.

<Means for solving the problem> Therefore, the present invention connects a Zener diode in series to an energy adjustment resistor that is parallel to the intermittent trigger capacitor of the charging circuit connected with a diode at both ends of the feedback winding. The voltage across both ends is clamped above a certain voltage, in other words, the minimum amount of charge in the capacitor required for triggering is guaranteed.

<Example> The illustrated embodiment will be described below.

First, during the positive half cycle of the AC power supply 1, the capacitor 15 is charged from the power supply line 1a via the resistor 2 and the resistor 7, and when the charging voltage reaches the breakover voltage of the appropriate switching element 14, the capacitor 15 is charged. The switching element becomes conductive, and the charge stored in the capacitor 15 is discharged to the gate of the thyristor 6 via the resistor 9, and becomes a trigger current.

When the thyristor 6 becomes conductive, the resonant capacitor 8 is charged through the path of the resonant inductor 5, the thyristor 6, the resonant capacitor 8, and the power supply line 1b. This charging current oscillates due to the resonance of the resonant inductor 5 and the resonant capacitor 8, and when the charging current is reversed, the thyristor 6 is turned off because it is in the opposite direction.

Then, the charge stored in the resonant capacitor 8 is transferred to the primary winding 22 of the ignition coil.
A high voltage is generated in the secondary winding 23, causing a spark discharge during the discharge period 9. At the same time, a voltage is generated in the feedback winding 21 of the ignition coil with the illustrated + and - polarities with respect to the primary winding, but at this time, this voltage is short-circuited by the diode 17 via the resistor 18 (i.e., Since the diode 17 is connected so as to be forward biased at this time), the gate of the thyristor 6 is not affected. At this point, the capacitor 15 is reliably reset (charge discharged) by turning on the reset transistor 16.

Next, due to the resonance between the resonant capacitor 8 and the primary winding 22, the resonant current is reversed and voltages with (+) and (-) polarities are generated in the primary winding as shown in the figure. At this time, a voltage is also generated in the feedback winding 21. A voltage is generated with the polarities (+) and (-) shown in the figure, and this is the polarity that reverse biases the diode 17 mentioned above, so the short circuit between both ends of the feedback winding 21 is broken, and the resistor 1
0, the capacitor 13, and the resistor 18, the capacitor 13 is charged with the illustrated (+) and (-) polarities. Then, when the voltage generated by the feedback coil 21 becomes lower than the charging voltage of the capacitor 13, the charged charge of the capacitor 13 flows into the gate of the thyristor 6 via the resistor 9, turning it on. This operation is repeated thereafter.

Therefore, to the intermittent trigger capacitor 13,
Since the variable resistor 12 is connected in parallel, changing this value changes the gate current and changes the turn-on time of the thyristor 6, so the output energy can be easily adjusted. In other words, if the turn-on time is shortened, the resonant voltage of the resonant capacitor 8 becomes higher, and the voltage applied to the primary coil 22 of the ignition coil also becomes higher, so that the output energy becomes larger.

According to the present invention, a Zener diode 24 is connected in series to the variable resistor 12 for output energy adjustment, and the variable resistor 12 and the Zener diode 24 are connected in parallel to the capacitor 13 for the thyristor intermittent trigger. A charging circuit is configured.

As a result, the capacitor 13 for the thyristor intermittent trigger is always charged with an electric charge above a certain level, so that the thyristor 6 can be reliably commutated even if the resistor 12 for adjusting the output energy becomes small. In other words, the minimum amount of charge that can reliably commutate the thyristor 6 can be secured by the Zener diode 24.

<Effects of the invention> As described above, according to the invention, not only can a discharge spark with a long duration (overall) be obtained with an inexpensive and compact device, but also the adjustment of its absolute value can be done by changing the resistance value. A highly versatile multi-spark ignition device is obtained which can be easily carried out in the following manner and also eliminates the problem of unstable operation due to inability to reliably commutate the thyristor.

[Brief explanation of the drawing]

The drawing is a schematic diagram of an embodiment of a multi-spark ignition device according to the present invention. In the figure, 1 is an AC power supply, 5 is a resonant inductor,
6 is a thyristor, 8 is a resonant capacitor, 21 is a feedback winding, 22 is an ignition coil primary winding, 23 is also a secondary winding, 2, 7, 9, 10,
18, 19, 20 are resistances, 4, 11, 15, 13
is a capacitor, 17 is a diode, 12 is a variable resistor, and 24 is a Zener diode.

Claims (1)

[Claims for Utility Model Registration] A self-oscillation system in which a thyristor series inverter circuit is self-oscillated using an ignition coil as a load, and a high voltage generated on the secondary side of the ignition coil causes multiple sparks to fly between discharge electrodes. In an excitation thyristor series inverter type multi-spark ignition device: In a polarity where the high voltage is generated on the secondary side, both ends of the feedback winding are short-circuited at both ends of the feedback winding that is magnetically coupled to the primary winding of the ignition coil. a diode that is forward biased so that the feedback winding is forward-biased; and a capacitor that is charged with a charging current that flows in accordance with the voltage that occurs across the feedback winding when the polarity across the feedback winding becomes a polarity that reverse biases the diode. Connect; trigger the thyristor in the thyristor series inverter circuit by the discharge current of the capacitor based on the drop in the voltage across the feedback winding; and clamp the voltage across the capacitor and the resistor for output energy adjustment to a certain voltage or higher. A series circuit with a Zener diode is connected in parallel to the capacitor.