JPS6055713B2 - internal combustion engine ignition system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ignition system for an internal combustion engine, and more particularly to a capacitor charge/discharge type ignition system.

Figure 1 shows a conventional circuit of this type. In the figure, EXT and P are power generation coils and ignition signal generation (pulsar) coils of a magnet generator rotated by an internal combustion engine, D1 and D3 are rectifier diodes, and C and Igc. and SCR are a capacitor, an ignition coil, and a thyristor forming a closed circuit, and the capacitor C is charged via the diode D1 with the output voltage of one half cycle of the generator coil EXT. Then, a signal generated from the pulsar coil P in synchronization with the engine is applied to the gate g of the thyristor SCR via the diode D3, and the thyristor SCR is turned on (fired), and the charge in the capacitor C is discharged via the closed circuit. do. Therefore, it operates to generate a spark at the ignition plug IP via the secondary winding n2 of the ignition coil Igc. In order to fire the thyristor SCR in such a conventional circuit, the voltage generated by the pulser coil P must be the firing voltage VGT (approximately 1V) of the thyristor SCR.
The sum (V
It will not operate unless the voltage exceeds GT+VF■2V). Since the generated (output) voltage of the pulsar coil P is proportional to the engine speed, if the sum of the voltages (VGT+VF) is high, the engine starting speed must be set high.
The drawback is that it becomes difficult to start up. The present invention solves the above-mentioned drawbacks by applying a bias to the cathode of the thyristor SCR using the reverse current of the generating coil, and apparently lowering the firing voltage of the thyristor SCR. The present invention, which aims to provide an ignition device with excellent ignition characteristics, will be described in detail below with reference to the drawings. Second
The figure shows a circuit according to an embodiment of the present invention, and the same reference numerals as in the conventional circuit indicate equivalent parts. As is clear from the conventional example, in the present invention, a diode D5 is connected in parallel between the cathode K of the thyristor SCR and the ground G with the opposite polarity to the thyristor SCR, and the connection point is used to short-circuit the (generated) voltage of the generating coil EXT. This is characterized in that it is connected to one end (anode) of the diode D2. Next, the circuit operation of the present invention will be explained with reference to the operation waveform diagram of each part in FIG. First, Fig. 3a shows the output voltage waveform of the generator coil EXT, and Fig. 3b shows the output (ignition signal) voltage waveform of the pulsar coil P. In terms of the phase relationship, the ignition signal and the output voltage of the generator coil EXT are It is assumed that this is set in advance to occur during a negative half cycle. Now the terminal 6 of the generator coil EXT
When has four polarities, the capacitor C is charged via the rectifying diode D1 as in the conventional circuit. On the other hand, when terminal 5 has one polarity, terminal 5 → ground G → diode D5 → diode D
A reverse current 12 flows in the path from 2 to terminal 4. For this reason, a forward voltage drop VFD5 (approximately 1 cm) occurs in the diode D5 as shown in the illustrated polarity. This voltage VFD5 connects the cathode K of the thyristor SCR to the ground (VFD5).
It has the effect of reducing the amount of During this time, the current 11 of the pulsar coil P is from the ground G → the pulsar coil P → the diode D3 →
The current flows in a path from the gate of the thyristor SCR to the diode D2 to the terminal 5, and this current causes a forward voltage drop VFD3 (approximately 1 V) to occur in the diode D3 as shown in the illustrated polarity. In other words, the cathode potential of the thyristor SCR is lowered by ■FD5 (approximately 1V) due to the effect of the diode D5, and as a result, the voltage drop of the diode D3 is reduced by ■FD3 (approximately 1V).
) to cancel. Follow. Therefore, the voltage VP of the pulser coil P can be expressed as follows. That is, according to the present invention, when the generated voltage (P) of the pulsar coil P that causes the thyristor SCR to fire becomes approximately (ignition voltage of the thyristor SCR) GT, the generated voltage VP is apparently increased. Can be reduced to width.

Therefore, when the generated voltage VP, which is proportional to the engine rotational speed, reaches the GT, the thyristor SCR can be ignited and generate a spark at the spark plug (■), thereby greatly increasing the starting rotational speed of the engine. It is possible to obtain stable ignition characteristics from low speed rotation. FIG. 4 shows another embodiment of the circuit of the present invention, in which a low-speed generating coil 1a that generates an output during low-speed rotation and a high-speed generating coil 1b that generates an output during high-speed rotation are provided as the generating coil EXT, and the high-speed generating coil 1 is provided.
Diode D due to the output current during the other half cycle of b
The operation of the thyristor SCR is similar to that shown in FIG. 2, and will not be described here. In addition,
It is clear that the same effect can be achieved by using the reverse current of the low-speed generator coil, contrary to the above. As is clear from the above description, according to the present invention, stable ignition characteristics can be obtained from low speed rotation to high speed rotation of the engine without increasing the number of turns of the pulsar coil, so the present invention is suitable as an ignition system for vehicle engines, etc. The practical effects are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a conventional circuit diagram, FIGS. 2 and 3 are circuit diagrams of one embodiment of the present invention and operation waveform diagrams of each part thereof, and FIG. 4 is a circuit diagram of another embodiment of the present invention.

Claims (1)

[Claims] 1 A closed circuit is formed by a capacitor, an ignition coil, and a thyristor, and a circuit is provided in this circuit for charging the capacitor with the output voltage of one half cycle of the generating coil, and a circuit for charging the capacitor with the output voltage of one half cycle of the generating coil, and In an internal combustion engine ignition device, a circuit is provided for igniting the thyristor via a diode in response to an ignition signal from a half-cycle ignition signal generating coil, and the charge in the capacitor is discharged into the closed circuit for ignition. A circuit is provided to apply a diode voltage drop due to the output current (reverse current) of the other half cycle of the generating coil to the cathode of the thyristor, and a bias is applied to the thyristor for ignition of the thyristor. An internal combustion engine ignition device characterized in that the voltage is apparently reduced. 2. A patent characterized in that a high-speed coil and a low-speed coil are provided as power generation coils, and a circuit is provided for applying a voltage drop across a diode due to the output current of the other half cycle of one of the coils to the cathode of a thyristor. An internal combustion engine ignition system according to claim 1.