JPS631500B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a self-excited thyristor series inverter type multiple spark ignition device.

Figure 1 shows a conventional example of a common type of ignition system. In these conventional systems, the AC power source 1 is mainly 100V AC, and 200V systems are rarely used. Ta. This was due to the convenience of the thyristor used, as described below.

For example, if the power supply 1 is 200V, the resonant inductor 5 and resonant capacitor 8 in the series inverter circuit
Due to the resonance, the resonant voltage applied between the anode and cathode of the thyristor 6 becomes 800V or more, so the reverse withstand voltage required for the thyristor 6 is
It will be 1KV class. Currently, thyristors with such a high reverse breakdown voltage have a long turn-off time or recovery time of several tens of microseconds, which makes it impossible to increase the number of spark discharges per unit time. It was not possible to obtain a large amount of overall ignition energy.

Despite these limitations, if you try to increase the ignition energy with the conventional configuration, you will have to increase the capacitance of the capacitor 8, but if you do this, the resonant current per cycle will increase. Therefore, the current capacity of the thyristor 6 and the ignition coil primary winding 21 had to be increased, and in the end,
This resulted in an increase in the size and cost of the equipment. Furthermore, considering that, in general, the larger the current capacity, the longer the recovery time of the thyristor, this type of conventional method, ie, the method of increasing the energy per unit discharge, is also a vicious cycle.

The present invention was made in view of these circumstances.
The present invention aims to provide a circuit that can maintain a large number of discharges even if the thyristor portion is required to have a high withstand voltage due to a high power supply voltage.

To put it simply, the thyristor part of the series inverter circuit is constructed from a series circuit of a plurality of individual thyristors, and each thyristor is triggered simultaneously by its own dedicated gate circuit. Since the withstand voltage is one-half of the total number, the recovery time is short, and the number of repeated spark discharges can be maintained at a large number.

Hereinafter, one embodiment of the present invention is shown in FIG. 2, and two thyristors 6a,
6b in series will be explained. Note that each of the dedicated gate circuits 28a and 28b itself may be similar to the conventional gate circuit 28 shown in FIG. 1, and any existing circuit configuration may be used. It's nothing more than that. Therefore, not only the same reference numerals, but also the components indicated by the respective reference numerals with suffixes a and b indicating that they belong to the first and second gate circuits 28a and 28b of this embodiment are as follows:
The reference numerals omitting the suffixes a and b correspond to the components of the conventional structure shown in FIG. Since there is no change in the basic trigger operation and resonance operation, the explanation of these in this embodiment will replace the explanation of the operation of the prior art example.

First, a good AC power supply with high voltage such as 200V AC.
During a half cycle, capacitors 14a and 14b are charged from one terminal 1a of the battery via resistor 2 and resistors 7a and 7b. When the charging voltage of this capacitor reaches the threshold voltage or breakover voltage of the appropriate switching element 13a, 13b, this switching element becomes conductive and transfers the resonance charge of the capacitor 14a, 14b to the thyristor 6a, 14b via the resistor 9a, 9b. 6b and is used as a trigger current.

When the thyristors 6a and 6b become conductive at the same time, the resonant inductor 5, the thyristor 6a,
6b, the resonance capacitor 8, and the power supply terminal 1b, the resonance capacitor 8 is charged. 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 thyristors 6a and 6b are turned off because they are in opposite directions. Then, the charge stored in the resonant capacitor 8 is transferred to the primary winding 2 of the ignition coil.
1, a high voltage is generated in the secondary winding 23, and a spark discharge occurs in the discharge electrode g. at the same time,
Ignition coil feedback winding or tertiary winding 2
a, 22b include the + and - shown in the figure with respect to the primary winding.
A voltage is generated with the polarity of , but at this time, this voltage is short-circuited by the Zener diodes 18a and 18b via the resistors 16a and 16b, so it does not affect the gates of the thyristors 6a and 6b.

Next, due to the resonance between the resonant capacitor 8 and the primary winding 21, the resonant current is reversed and voltages with (+) and (-) polarities are generated in the primary winding as shown in the figure. While a high voltage is generated in the wire 23 and a spark discharge occurs in the discharge electrode g, a voltage is also generated in the tertiary windings 22a and 22b with the polarities (+) and (-) shown in the figure, and the diodes 11a and 11b and the capacitor 15a, 15b, resistors 16a, 16b, and capacitors 15a, 1 with polarities (+) and (-) shown in the diagram.
Charge the 5b. When the voltage of the tertiary winding becomes zero, the charges accumulated in the capacitors 15a and 15b flow into the gates of the thyristors 6a and 6b via the resistors 9a and 9b.
Turn this on. This operation is repeated thereafter.

In this embodiment, a series circuit of a resistor 24a and a capacitor 25a and a resistor 26a are connected to the first thyristor 6a, and a series circuit of a resistor 24b and a capacitor 25b and a resistor 26b are connected to the second thyristor 6b. Since the surge absorption circuits 27a and 27b are placed in parallel, the resonant voltage of the resonant capacitor 8 and the resonant inductor 5 is shared equally even if there is a slight difference in characteristics between the two thyristors 6a and 6b used. This eliminates the inconvenience of applying a high reverse voltage to only one thyristor.

As described above, in the present invention, a plurality of thyristors (two in the illustrated embodiment, but it is already obvious to those skilled in the art that three or more thyristors can be used) are connected in series, and the same number of independently separated gate circuits 28a , 28b, . . . to simultaneously trigger the corresponding thyristors 6a, 6b, . . . to cause self-oscillation. Even under conditions such as a voltage of 800V, each thyristor 6a, 6b has, for example,
It is possible to use a thyristor with a low withstand voltage of 500V and a turn-off time of several μs or less, which allows for a large number of discharge repetitions, so it can achieve large ignition energy without the disadvantages of using a large capacity capacitor as in the past. can be obtained, and the effect is great.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an example of a conventional self-excited thyristor series inverter type multiple spark ignition device, and FIG. 2 is a schematic diagram of an embodiment of the present invention. In the figure, 1 is an AC power supply, 5 is a resonant inductor,
6, 6a, 6b are thyristors, 8 is a resonant capacitor, 21 is an ignition coil primary winding, 23
Similarly, 27a and 27b are surge absorption circuits, and 28, 28a, and 28b are thyristor trigger gate circuits.

Claims (1)

[Scope of Claims] 1 Self-excitation in which a thyristor series inverter circuit is caused to self-oscillate using an ignition coil as a load, and a plurality of sparks are caused to fly between discharge electrodes using a high voltage generated on the secondary side of the ignition coil. In a thyristor series inverter type multiple spark ignition device, the thyristor in the thyristor series inverter circuit is configured by connecting multiple individual thyristors in series, and each thyristor is simultaneously triggered by a dedicated gate circuit for each thyristor to generate self-oscillation. A multi-spark ignition device characterized by causing ignition.