JPH0513989Y2 - - Google Patents

Description

[Detailed explanation of the idea] Technical field The present invention relates to an ignition device for an internal combustion engine.

Background technology The so-called capacitive discharge type (CDI) is used as an ignition device to ignite the air-fuel mixture in the combustion chamber of an internal combustion engine.
type) ignition device is known.

An example of such an ignition device is shown in FIG. In this figure, a generating coil 1 is an electromotive force generating coil of an alternator that is driven by a rotating body that rotates with the operation of an engine such as a crankshaft of an internal combustion engine, and a sensor coil 2 is mounted on the rotating body. This generates a pair of positive and negative timing pulses in synchronization with the engine operation. Generator coil 1
The alternating current voltage generated at is rectified by the diode 3 and appears as a direct current voltage at the connection point _J , thereby discharging the capacitor 4. Capacitor 4 is ignition transformer 5
is connected in series to the primary coil of Note that the secondary coil of the ignition coil 5 is connected to a spark plug 8 disposed inside the cylinder of the internal combustion engine, and
When a sharp current change occurs in the next coil, a high voltage is supplied to the ignition plug 8 and a spark is generated in the discharge gap of the ignition plug 8. A gate-controlled rectifier (hereinafter referred to as thyristor) is installed at connection point _J.
9 and 10 are connected in series to form a thyristor 9 and 10.
When both are on, the charges accumulated in the capacitors are discharged through the thyristors 9 and 10 and the primary coil of the ignition transformer 5.

On the other hand, the timing pulse sent out from the sensor coil 2 is supplied to the trigger pulse generation circuit 11. The trigger pulse generation circuit consists of resistors R ₁ to _{R 3} , capacitors C ₁ to C ₃ , diode D ₁ and transistor
_Q1 , which supplies a trigger pulse to the gate trigger generation circuit 12 when a positive timing pulse is generated. Gate trigger generation circuit 12 is a transistor
Q ₂ , diode D ₃ , resistor R ₄ to R ₁₀ , capacitor
It consists of C ₄ , C ₅ and a Zener diode D _Z , and supplies a gate trigger pulse to the gate terminals of thyristors 9 and 10 in response to a positive timing pulse to make them conductive almost simultaneously.

Due to the conduction of the thyristors 9 and 10, the charge accumulated in the capacitor is discharged through the thyristors 9 and 10 and the primary coil of the ignition transformer, and eventually ignition is performed in synchronization with the positive timing pulse.

By the way, the voltage of the gate trigger pulse that makes the thyristor conductive must be of a magnitude that generates the voltage necessary for conduction between the gate and cathode of each thyristor _. is thyristor 1
The voltage must be high enough to account for the voltage drop _VFS between the anode and cathode at turn-on.

Therefore, if the engine speed is low and the peak value of the timing pulse is small, it will not be possible to obtain a gate trigger pulse of sufficient size, and even when the engine speed is low, the transistor ₂ , the gate trigger pulse generation circuit 12 including the gate trigger pulse generating circuit 12 is provided, and the circuit as a whole is complicated and costly.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an ignition device for an internal combustion engine that has a simple circuit configuration and is low in cost.

In the ignition device for an internal combustion engine according to the present invention,
The capacitor discharge switch is formed by a thyristor, and the timing pulse obtained from the sensor coil is voltage-double rectified and then supplied to the gate terminal of the thyristor, so that a gate trigger of sufficient size can be generated without using an amplification element. You're getting a pulse. Furthermore, in a series circuit of a diode and a capacitor forming the voltage doubler current, a Zener diode was connected in parallel with the capacitor.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to FIG. 2 and the following drawings.

In the basic circuit of the present invention shown in Figure 2,
Positive and negative timing pulses obtained from the sensor coil 2 are supplied via a resistor R ₁₁ to a voltage doubler circuit 20 consisting of capacitors C ₆ and C ₇ and a diode D ₁₀ . The output voltage of the voltage doubler circuit 20 is
As trigger pulse, resistor R ₁₂ and capacitor C ₈
The signal is supplied to the gate trigger circuit 22 through a capacitive circuit 21 consisting of parallel circuits. The capacitive circuit 21 acts as a relay circuit that relays the doubled voltage output as a trigger pulse to the gate trigger circuit 22. The gate trigger circuit 22 includes diodes D ₁₁ , D ₁₂ and resistors.
It consists of R ₁₃ to R ₁₆ and triggers the thyristors 9 and 10 to conduct in response to the trigger pulse. The alternating current voltage obtained from the generator coil 1 is rectified by the diode 3 to charge the capacitor 4, and by turning on and off the thyristors 9 and 10, a steep current is generated in the primary winding of the ignition coil 5. The point of causing change and performing the ignition action is the same as the conventional example shown in FIG.

In the operation of the above basic circuit, the sensor coil 2
The timing pulse obtained from the negative pulse N of the peak voltage _VN and the peak voltage
It consists of a positive pulse P of V _P. When such a timing pulse is supplied to the voltage doubler rectifier circuit 20, first, by the negative pulse N passing through the diode _D10 ,
Capacitor C ₇ is charged. Capacitor _C7 discharges slowly until the next negative pulse, but is continuously charged by negative pulses, so the voltage _{across capacitor C7 (} voltage between connection points b and c) is Figure 3b
It will be like this. On the other hand, positive timing pulse P
is blocked by diode D ₁₀ and
The voltages across the capacitors are added and generated at the connection point C, and the potential at the connection point C becomes (V _C +V _P ) as shown in FIG. 3 and is supplied to the gate trigger circuit 22 via the capacitive circuit 21. The peak voltage (V _C +V _P ) passed through the gate trigger circuit 22 is supplied to the gate terminals of the thyristors 9 and 10 to turn them on. Here, voltage doubler rectifier circuit 2
0 is to charge the negative timing pulse N and superimpose the positive timing pulse P on top of this voltage, and other circuit configurations can be considered to achieve this effect.

Note that the capacitor _C8 acts as a so-called speed-up capacitor.

FIG. 4 shows an embodiment of the present invention, which is the same as the basic circuit of FIG. 2 except that a Zener diode ZD is connected in parallel to the capacitor _C7 .

By connecting the Zener diode ZD, the charging voltage at both ends of the capacitor _C7 is equal to the Zener diode.
Since the zener voltage is suppressed below the Zener voltage of the ZD, it is possible to prevent peak value fluctuations caused by noise mixed into the timing signal, thereby preventing fluctuations in the ignition timing.

Effects of the invention As is clear from the above, the invention
In the CDI type ignition system, the gate trigger voltage to the thyristor as a switching means is obtained by charging a capacitor with one of the positive and negative pulses obtained from the sensor coil, and superimposing the other pulse on the charging voltage to obtain voltage double rectification. Since the circuit configuration is
It operates reliably even at low engine speeds and does not use active elements in the gate trigger circuit, so the overall number of active elements is small and the cost is low.

Moreover, since a Zener diode is provided in parallel with the capacitor that constitutes the voltage doubler rectifier circuit, stable ignition operation is achieved.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a conventional example, Fig. 2 is a circuit diagram showing the basic circuit configuration of the present invention, and Fig. 3 is a circuit diagram showing the basic circuit configuration of the present invention.
Waveform diagram showing signal waveforms occurring in the circuit shown in Figure 4.
The figure is a circuit diagram showing an embodiment of the present invention. Explanation of symbols of main parts, 1...Generating coil, 2
...Sensor coil, 5...Ignition transformer, 9,1
0... Thyristor, 20... Voltage doubler rectifier circuit, 2
1, 22... Capacitive circuit and gate trigger circuit forming a relay circuit.

Claims (1)

[Claims for Utility Model Registration] A series circuit of a capacitor and the primary winding of an ignition transformer having a secondary winding that supplies high voltage to a spark plug of an internal combustion engine, and a power source that applies a DC voltage to the series circuit. a circuit, a timing pulse generating means for generating a pair of positive and negative timing pulses synchronized with the operation of the internal combustion engine, a trigger pulse generating means for generating a trigger pulse in response to the timing pulse, and conduction in response to the trigger pulse. and switch means for short-circuiting both ends of the series circuit, the switch means comprising a thyristor that becomes conductive when the trigger pulse is received at its gate terminal, and the trigger pulse generating means for generating the timing pulse. and a relay circuit that relays the voltage doubler output to the gate terminal of the thyristor. A Zener diode is connected to the capacitor, the terminal not connected to the diode is connected to the output terminal of the timing pulse generating means, and the trigger pulse is generated from the connection point between the capacitor and the diode. An ignition device characterized by an output.