JP2850622B2 - Capacitor discharge type ignition system for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor discharge ignition system for an internal combustion engine.

[0002]

2. Description of the Related Art A capacitor discharge type ignition device for an internal combustion engine is provided with an ignition energy storage capacitor provided on a primary side of an ignition coil, a charging circuit for charging the capacitor, and an ignition energy storage device when the capacitor is turned on. It comprises a discharging thyristor provided to discharge the electric charge of the capacitor to the primary coil of the ignition coil, and an ignition timing control circuit for giving a trigger signal to the thyristor at the ignition timing of the internal combustion engine.

In this type of ignition device, there is a case where a converter circuit is used as a power source for a capacitor charging circuit, which boosts a DC voltage by intermitting a primary current of a transformer by a switching element which is turned on and off by a driving pulse obtained from an oscillator. is there. In a capacitor discharge ignition device using a DC voltage boost converter circuit,
If the converter circuit is operating when the discharging thyristor is turned on, the secondary side of the transformer of the converter circuit is short-circuited through the thyristor, causing a large short-circuit current to flow and failing to commutate the thyristor. become. Therefore, in this type of ignition device, it is necessary to provide a protection circuit for stopping the operation of the converter circuit when the thyristor is turned on.

[0004] The applicant of the present invention has previously described Japanese Patent Application Laid-Open No. 1-117984.
When the trigger signal is given to the discharge thyristor and the gate-cathode voltage of the thyristor becomes equal to or higher than a predetermined value, the supply of the drive pulse to the switching element of the converter circuit is stopped, An ignition device including a protection circuit for a converter that supplies a drive pulse to a switching element only when the inter-voltage is lower than a predetermined value has been proposed.

[0005]

In the device proposed above, the operation of the protection circuit may not be able to keep up at high speed of the engine due to the variation in the gate sensitivity of the thyristor, so that the discharge before the supply of the driving pulse is stopped. Thyristor may conduct. When such a state occurs, the secondary side of the transformer of the converter circuit is short-circuited for a short time, and a large current flows through the primary side and the secondary side of the transformer, so that unnecessary power is consumed and much heat is generated. There was a problem of becoming. In addition, since it is necessary to use a large-capacity element capable of withstanding a large current as an element such as a transformer or a thyristor, it is inevitable that the ignition device becomes large.

An object of the present invention is to provide an ignition device for a capacitor discharge type internal combustion engine which eliminates the possibility that the operation of a protection circuit is delayed at the time of high speed of an engine and the secondary side of a transformer of a converter circuit is short-circuited.

[0007]

SUMMARY OF THE INVENTION The present invention provides a DC voltage boosting converter circuit having a switching element which is turned on and off by a drive pulse, and an ignition provided on the primary side of an ignition coil and charged by an output of the converter circuit. A trigger signal is supplied to the energy storage capacitor, a discharge thyristor provided to discharge the charge of the ignition energy storage capacitor to the primary coil of the ignition coil when conducting, and a discharge thyristor at the ignition timing of the internal combustion engine. The present invention relates to a capacitor discharge type ignition device for an internal combustion engine, which is provided with an ignition timing control circuit.

In the present invention, the gate-cathode voltage of the discharging thyristor is compared with a reference voltage set lower than the trigger level of the thyristor, and when the gate-cathode voltage is lower than the reference voltage, the operation permission signal is output. An operation permission signal generating circuit for outputting, a timer circuit for outputting a timer signal for a fixed time from the time when the operation permission signal is generated, and a drive pulse for the switching element when the operation permission signal and the timer signal are simultaneously generated. And a drive pulse supply control circuit for controlling the supply of the drive pulse to the switching element so as to stop the supply of the drive pulse to the switching element when the operation permission signal or the timer signal is extinguished. The time width of the timer signal is set so that the timer signal has disappeared before the time when the error occurs.

[0009]

With the above configuration, the operation of the converter circuit can be reliably stopped when the thyristor is turned on. Therefore, when the engine is running at high speed, a large short-circuit current flows to the secondary side of the transformer of the converter circuit due to the thyristor turning on. Can be eliminated. Therefore, the heat generation of the transformer can be reduced, and it is not necessary to use a transformer or thyristor having an unnecessarily large capacity, so that the size of the ignition device can be reduced.

[0010]

FIG. 1 shows an overall configuration of an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an ignition coil having a primary coil and a secondary coil 1b whose one end is grounded, and 2 does not show. The ignition plug is attached to the cylinder of the engine and connected to the secondary coil of the ignition coil. A diode 3 whose cathode is directed to the ground side is connected in parallel to the primary coil 1a, and one end of an ignition energy storage capacitor 4 is connected to a non-ground side terminal of the primary coil 1a. A discharge thyristor 5 is connected between the other end of the capacitor 4 and the ground with its cathode facing the ground, and a capacitor 6 and a resistor 7 are connected in parallel between the gate and cathode of the thyristor 5.

The gate of the thyristor 5 is connected to the output terminal of the ignition timing control circuit 8. The ignition timing control circuit 8 receives the output signal of the signal generator 9 attached to the internal combustion engine and outputs a pulse-like trigger signal Vg as shown in FIG. 3A at the ignition timing of the internal combustion engine.

To charge the capacitor 4, the transformer 1
0, an oscillating circuit 11 for generating a driving pulse, a switching element 13 connected in series to the primary coil 10a of the transformer and turned on and off by a driving pulse given from the oscillating circuit 11 through the AND circuit 12, A DC-DC converter circuit 15 including a diode 14 having an anode connected to the non-ground side terminal of the next coil 10b is provided, and a cathode of the diode 14 is connected to a connection point between the capacitor 4 and the thyristor 5.

An output of a DC power supply comprising a battery 16 is applied to a primary coil 10a of the transformer 10 through a switch 17. The battery 16 is charged by a rectified output of a magnet generator (not shown) driven by the internal combustion engine.

In the converter circuit described above, when the switching element 13 is turned on and off, the primary current of the transformer 10 is intermittent.
A high voltage is induced in the next coil 10b. Since the induced voltage of the secondary coil of the transformer 10 is applied to the capacitor 4 through the diode 14, the capacitor 4 is charged to the illustrated polarity, and the terminal voltage Vc rises as shown in FIG. When a trigger signal is given to the thyristor 5 at the ignition timing of the internal combustion engine, the thyristor 5 conducts, so that the electric charge of the capacitor 4 is discharged to the primary coil of the ignition coil 1 and a high voltage is applied to the secondary coil of the ignition coil. Is induced. Since this high voltage is applied to the spark plug 2, a spark is generated in the spark plug 2 and the engine is ignited.

To form a protection circuit for the converter circuit 15, the gate-cathode voltage of the thyristor 5 is compared with a reference voltage set lower than the trigger level of the thyristor, and the gate-cathode voltage is lower than the reference voltage. Enable signal generation circuit 2 that outputs an operation enable signal V1 to
0, a charge command generation circuit 21 for detecting a charge voltage of the ignition energy storage capacitor 4 and outputting a charge command signal V2 when the charge voltage is lower than a set voltage, and a constant from the time when the operation permission signal is generated. Timer signal V during the time
3 is provided, and the outputs of these circuits are input to the AND circuit 12. The AND circuit 21 supplies a drive pulse to the switching element 12 when all of the operation permission signal V1, the charge command signal V2, and the timer signal V3 are generated, and outputs any one of the operation permission signal, the charge command signal, and the timer signal. Stops supplying the drive pulse to the switching element when disappears. A drive pulse supply control circuit that controls the supply of the drive pulse to the switching element by the AND circuit 12 is configured.

Oscillation circuit 11, operation permission signal generation circuit 2
0, to supply a power supply voltage to the charge command generation circuit 21, the timer circuit 22, and the ignition timing control circuit 8,
Power supply circuit 23 that outputs a constant DC voltage using
Is provided.

Referring to FIG. 2, there is shown an embodiment in which each part of FIG. 1 is concretely shown. In this embodiment, the switching element 13 is composed of an FET, the source of which is grounded, and the drain of which is the primary coil 1 of the transformer 10.
0a. The gate of the FET is connected to the output terminal of the AND circuit 12.

The oscillation circuit 11 is a known non-stable multivibrator comprising an operational amplifier OP1, resistors R1 to R6, diodes D1 and D2, and a capacitor C1, and a pulse having a constant frequency is output to the output terminal of the operational amplifier OP1. Generate a signal.

The operation permission signal generating circuit 20 includes a comparator CP
1 and resistors R7 to R9. The output terminal of the comparator CP1 is input to the AND circuit 12. Comparator C
The gate-cathode voltage Vg of the thyristor 5 is input to the inverting input terminal of P1, and the reference voltage Vo obtained by dividing the output voltage of the stabilized power supply circuit 23 by the resistors R7 and R8 is input to the non-inverting input terminal. Has been entered. Comparator CP1
Outputs a high-level operation permission signal V1 (FIG. 3D) when the gate-cathode voltage Vg of the thyristor 5 is lower than the reference voltage Vo. The reference voltage Vo is set lower than the trigger level of the thyristor 5.

The charge command generation circuit 21 includes a comparator CP2
And the resistors R10 to R14. The output of the comparator CP2 is input to the AND circuit 12. The voltage at both ends of the capacitor 4 is connected to the inverting input terminal of the comparator CP2 by a resistor R.
A detection value Vc of the charging voltage of the capacitor 4 obtained by dividing the voltage by the resistors 10 and R11 is input, and the output voltage of the stabilized power supply circuit 23 is connected to the non-inverting input terminal of the comparator CP2 by the resistors R12 and R11.
The set voltage Vf obtained by dividing the voltage by 13 is input.
When the charging voltage Vc of the ignition energy storage capacitor 4 is lower than the set voltage Vf, the comparator CP2
As shown in (G), a high-level charge command signal V2 is output.

The timer circuit 22 includes a comparator CP3, resistors R15 to R19, a diode D3, and a capacitor C2.
The output of the comparator CP3 is input to the AND circuit 12. The terminal voltage of the capacitor C2 is input to the inverting input terminal of the comparator CP3, and the reference voltage Vr obtained by dividing the output voltage of the stabilized power supply circuit 23 by the resistors R15 and R16 is applied to the non-inverting input terminal of the comparator. Is entered. In this timer circuit, when the output of the comparator CP1 of the operation permission signal generating circuit goes high (when the operation permission signal V1 is generated), the resistance value of the resistor R17 and the capacitance of the capacitor C2 The capacitor C2 is charged with a constant time constant determined by the above equation, and its terminal voltage Vc2 rises as shown in FIG. When the potential of the output terminal of the comparator CP1 becomes the ground potential, the charge of the capacitor C2 is quickly discharged through the resistor R18, the diode D3, and the output stage of the comparator CP1. The resistor R18 is the comparator CP
It is provided to limit the discharge current flowing through one output stage. The comparator CP3 outputs a high-level timer signal V3 (FIG. 3F) while the terminal voltage Vc2 of the capacitor C2 is lower than the reference voltage Vr. When the terminal voltage of the capacitor C2 becomes higher than the reference voltage Vr, the comparator CP3 outputs the timer signal. Stop. The time width of this timer signal is constant irrespective of the engine speed. In this embodiment, the time width of the timer signal is set such that the timer signal V3 disappears before the time when the trigger signal Vg is generated at the time of high speed of the engine.

The AND circuit 12 supplies a pulse signal output from the oscillation circuit 11 to the switching element 13 as a drive pulse when all of the operation permission signal V1, the charge command signal V2, and the timer signal V3 are generated, and permits the operation. Signal V
1. When any one of the charge command signal V2 and the timer signal V3 disappears, the supply of the drive pulse to the switching element 13 is stopped.

In the above embodiment, when the trigger signal Vg is generated and the gate-cathode voltage of the thyristor 5 becomes lower than the reference voltage Vo, the operation permission signal generating circuit 20 shown in FIG. Thus, the operation permission signal V1 is output. At this time, since the charging voltage of the capacitor 4 is zero, the charging command generating circuit 21 outputs a charging command signal V2. Further, the timer circuit 22 outputs the timer signal V3 for a predetermined time from the time when the operation permission signal V1 is generated.
Accordingly, when the trigger signal of the thyristor 5 disappears, the AND condition of the AND circuit 12 is satisfied, and the driving pulse Vp is applied to the switching element 13 as shown in FIG. As a result, the switching element 13 is turned on and off to interrupt the primary current of the transformer 10 and induce a high voltage in the secondary coil of the transformer. This voltage is the diode 1
4, the capacitor 4 is charged. When the terminal voltage of the capacitor 4 reaches the set voltage Vf, the charge command signal V2 disappears, so that the AND condition of the AND circuit 12 is not satisfied, and the supply of the drive pulse to the switching element 13 is stopped.
As a result, the operation of the converter circuit stops, and the charging of the capacitor 4 stops. Once the terminal voltage of the capacitor 4 reaches the set voltage Vf, a pulse-like charge command signal V2 is generated only when the terminal voltage of the capacitor 4 slightly discharges and falls below the set voltage Vf. Each time a command signal is generated, a drive pulse is given to the switching element 13, the converter circuit operates, and the capacitor 4 is recharged. When the timer circuit 22 stops outputting the timer signal, the converter circuit does not operate thereafter and the capacitor 4 is not charged. When the trigger signal Vg is generated, the thyristor 5 becomes conductive, so that the electric charge of the capacitor 4 is discharged through the thyristor 5, and a high voltage Vh is generated in the secondary coil of the ignition coil 1 as shown in FIG. The operation is performed.

As described above, according to the present invention, the timer circuit is provided which outputs a timer signal which is generated simultaneously with the operation permission signal and disappears before the time when the trigger signal is generated. Is designed to stop the supply of the drive pulse to the switching element of the converter circuit even if other conditions are satisfied, so that the secondary side of the transformer of the converter circuit may be short-circuited due to conduction of the thyristor at high engine speed. Can be eliminated.

It is preferable that the time width of the timer signal be set as long as possible so that the capacitor 4 is charged to the set voltage even at the maximum operating speed of the engine. At high speed, the capacitor 4
Before the charging voltage reaches the set voltage, the timer signal may be extinguished and the capacitor may stop charging. In the present invention, the protection of the converter circuit is prioritized over the securing of the charging voltage of the capacitor 4 at high speed, and even at the maximum operating speed of the engine, the timer is provided before the time when the trigger signal of the discharging thyristor is generated. Make sure that the signal disappears.

In the above-described embodiment, the timer circuit 22 is constituted by using the comparator CP3 and the CR integrator circuit. However, the timer circuit is provided by another circuit such as a monostable multivibrator triggered by the rise of the operation permission signal. Of course, a circuit may be configured.

In the above embodiment, the battery 16 is used as a DC power supply. However, even when a DC power supply comprising an AC generator driven by an internal combustion engine and a rectifier circuit for rectifying the output of the generator is used. The present invention can be applied.

In the above embodiment, when the charging voltage of the ignition energy storage capacitor is lower than the set voltage, a charging command signal is generated, and a drive pulse is supplied to the switching element of the converter circuit based on the presence of the charging command signal. However, the circuit 21 for generating the charge command signal may be omitted, and only the presence of the operation permission signal and the timer signal may be used as the condition for supplying the drive pulse.

[0029]

As described above, according to the present invention, an operation permission signal is generated while the voltage between the gate and the cathode of the discharging thyristor is lower than the reference voltage.
A timer circuit is provided for outputting a timer signal which is generated simultaneously with the operation permission signal and disappears before the time when the trigger signal is generated, and the switching of the converter circuit is performed when the operation permission signal and the timer signal are generated simultaneously. Since the drive pulse is applied to the element, the operation of the converter circuit can be reliably stopped when the thyristor is turned on, and a large short-circuit current flows to the secondary side of the transformer of the converter circuit when the thyristor is turned on when the engine is running at high speed. Can be eliminated. Therefore, the heat generation of the transformer can be reduced. Further, since it is not necessary to use a transformer or thyristor having a larger capacity than necessary, the size of the ignition device can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an embodiment in which each part of FIG. 1 is made concrete;

3 (A) to 3 (H) are waveform diagrams showing voltage waveforms at various parts in the embodiment of FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ignition coil, 2 ... Spark plug, 4 ... Ignition energy storage capacitor, 5 ... Discharge thyristor, 8 ... Ignition timing control circuit, 10 ... Transformer, 11 ... Oscillation circuit, 12 ...
AND circuit, 13 switching element, 14 diode, 15 converter circuit, 20 operation enable signal generation circuit, 22 timer circuit.

Claims (1)

(57) [Claims] A DC voltage boosting converter circuit having a switching element which is turned on / off by a drive pulse;
An ignition energy storage capacitor provided on the primary side of the ignition coil and charged by an output of the converter circuit; and discharging the charge of the ignition energy storage capacitor to the primary coil of the ignition coil when the capacitor is turned on. A thyristor for discharge provided on the thyristor, and an ignition timing control circuit for giving a trigger signal to the thyristor for discharge at the ignition timing of the internal combustion engine. An operation permission signal generating circuit that compares a voltage with a reference voltage set lower than a trigger level of the thyristor and outputs an operation permission signal when the gate-cathode voltage is lower than the reference voltage; A timer circuit that outputs a timer signal for a fixed time from the time when the The switching element supplies the drive pulse to the switching element when an image signal is simultaneously generated, and stops the supply of the drive pulse to the switching element when the operation permission signal or the timer signal disappears. A drive pulse supply control circuit that controls the supply of the drive pulse to the thyristor, wherein the time width of the timer signal is set so that the timer signal disappears before the time when the trigger signal is given to the thyristor. An ignition device for a capacitor discharge type internal combustion engine, comprising: