Ignition system for internal combustion engines

Claim 2

An ignition system for an internal combustion engine having a plurality of spark plugs comprising: an ignition coil including a primary coil and a secondary coil for generating a secondary voltage including a high voltage generated by interruption of a primary coil current, said secondary voltage reaching a dielectric breakdown voltage of a gap between discharge electrodes of any one of said spark plugs to cause a capacitive discharge therebetween; a DC high voltage generating circuit for generating a DC high voltage which is, in absolute value magnitude, lower than the dielectric breakdown voltage and higher than a voltage required to sustain discharge between the discharge electrode gap during a predetermined time interval from before occurrence of the capacitive discharge to a predetermined time or a predetermined crank angle thereafter; said DC high voltage generating circuit including memory means for storing a plurality of predetermined time periods corresponding to a plurality of engine conditions and for generating a signal indicative of one of said time periods in response to a detected engine condition, and a circuit responsive to said output signal of said memory means to determine said predetermined time interval after the beginning of the capacitive discharge, whereby the time of interrupting said DC high voltage is determined in dependence on the detected engine condition; an output circuit for selectively applying one of the secondary voltage and the DC high voltage to the discharge electrode gap in accordance with relative levels of both voltages; and an ignition coil control circuit for controlling supply and interruption of the primary coil current.

Claim 3

An ignition system according to claim 1, in which said ignition coil is constructed to generate a negative secondary high voltage, and said DC high voltage generating circuit is constructed to generate a negative DC high voltage, wherein said output circuit includes a first high voltage diode having a cathode connected to a secondary output terminal of said ignition coil and an anode adapted to be connected to said spark plugs, and a second high voltage diode having a cathode connected to said DC high voltage generating circuit and an anode connected to the anode of said first high voltage diode.

Claim 4

An ignition system according to claim 1, in which said ignition coil is constructed to generate a positive secondary high voltage, and said DC high voltage generating circuit is constructed to generate a positive DC high voltage, wherein said output circuit includes a first high voltage diode having an anode connected to a secondary output terminal of said ignition coil and a cathode adapted to be connected to said spark plugs, and a second high voltage diode having an anode connected to said DC high voltage generating circuit and a cathode connected to the cathode of said first high voltage diode.

Claim 5

An ignition system according to claim 1, 2 or 3, wherein said DC high voltage generating circuit includes switching means for performing on-off operation at a predetermined period during said predetermined time interval, and a transformer having a primary winding connected to a battery and said switching means so that a primary current in said transformer is controlled by said switching means, whereby during said predetermined time interval a voltage of said battery is stepped up to generate said DC high voltage.

Claim 6

An ignition system according to claim 1, 2 or 3, wherein said DC high voltage generating circuit includes a circuit for generating said DC high voltage, high-voltage semiconductor switching means disposed to be turned on after the expiration of said predetermined time interval, and a circuit responsive to the turning on of said switching means to decrease said DC high voltage to a level less than said voltage required to maintain the sustained discharge.

Claim 7

An ignition system for an internal combustion engine comprising: an ignition coil having a primary winding and a secondary winding for generating a secondary voltage including a high voltage generated by interruption of a primary current, said secondary voltage being decreased after occurrence of capacitive discharge at one of a plurality of spark plugs; said plurality of spark plugs each being supplied with said secondary voltage of said ignition coil, at each of said spark plugs capacitive discharge is caused when said ignition coil secondary voltage reaches a dielectric breakdown voltage of a gap between electrodes of the spark plug and then sustained discharge is caused; ignition signal generating means for generating an AC signal synchronized with the rotation of the engine; control signal generating means responsive to said AC signal synchronized with the engine rotation to generate a control pulse signal having a first transition edge indicative of a time of starting flow of a primary current in said ignition coil and a second transition edge indicative of a time of interrupting the primary current flow; control means responsive to said control pulse signal to control the primary current flow in said ignition coil; a monostable circuit responsive to said control pulse signal to generate a pulse signal having a duration for a predetermined time interval from the second transition edge of the control pulse signal to a predetermined time or crank angle; an oscillator circuit for generating repetitive pulses of a predetermined repetition rate; an AND circuit having a first input terminal for receiving the output pulse signal of said monostable circuit and a second input terminal for receiving the repetitive pulses from said oscillator circuit for delivering the repetitive pulses during said predetermined time interval; switching means responsive to the output pulse signal of said AND circuit to perform on-off operation during said predetermined time interval; transformer means whose primary current is controlled in response to the operation of said switching means to thereby generate a high voltage pulse in its secondary winding during said predetermined time interval; DC high voltage generating means for rectifying and smoothing said secondary high voltage pulse from said transformer means to generate during said predetermined time interval a DC high voltage which is lower than said dielectric breakdown voltage of spark plug gap in absolute value magnitude and which is higher than a voltage required to maintain said sustained discharge in absolute value magnitude; and output means connected to the secondary winding of said ignition coil and said DC high voltage generating means, whereby one of said secondary voltage generated by said ignition coil and said DC high voltage is selected in accordance with the relative levels thereof and supplied to the spark plug.

Claim 8

An ignition system for an internal combustion engine comprising: an ignition coil having a primary winding and a secondary winding for generating a secondary voltage including a high voltage generated by interruption of a primary current, said secondary voltage being decreased after occurrence of capacitive discharge at one of a plurality of spark plugs; said plurality of spark plugs each being supplied with said secondary voltage of said ignition coil, at each of said spark plugs capacitive discharge is caused when said ignition coil secondary voltage reaches a dielectric breakdown voltage of a gap between electrodes of the spark plug and then sustained discharge is caused; ignition signal generating means for generating an AC signal synchronized with the rotation of the engine; control signal generating means responsive to said AC signal synchronized with the engine rotation to generate a control pulse signal having a first transition edge indicative of a time of starting flow of a primary current in said ignition coil and a second transition edge indicative of a time of interrupting the primary current flow; control means responsive to said control pulse signal to control the primary current flow in said ignition coil; a monostable circuit responsive to said control pulse signal to generate a pulse signal having a duration for a predetermined time interval from the second transition edge of the control pulse signal to a predetermined time or crank angle; an oscillator circuit for generating repetitive pulses of a predetermined repetition rate; an AND circuit having a first input terminal for receiving the output pulse signal of said monostable circuit and a second input terminal for receiving the repetitive pulses from said oscillator circuit for delivering the repetitive pulses during said predetermined time interval; switching means responsive to the output pulse signal of said AND circuit to perform on-off operation during said predetermined time interval; transformer means whose primary current is controlled in response to the operation of said switching means to thereby generate a high voltage pulse in its secondary winding during said predetermined time interval; DC high voltage generating means for rectifying and smoothing said secondary high voltage pulse from said transformer means to generate during said predetermined time interval a DC high voltage which is lower than said dielectric breakdown voltage of spark plug gap in absolute value magnitude and which is higher than a voltage required to maintain said sustained discharge in absolute value magnitude; and output means connected to the secondary winding of said ignition coil and said DC high voltage generating means, whereby one of said secondary voltage generated by said ignition coil and said DC high voltage is selected in accordance with the relative levels thereof and supplied to the spark plug.

Claim 9

An ignition system for an internal combustion engine comprising: an ignition coil having a primary winding and a secondary winding for generating a secondary voltage including a high voltage generated by interruption of a primary current, said secondary voltage being decreased after occurrence of capacitive discharge at one of a plurality of spark plugs; said plurality of spark plugs each being supplied with said secondary voltage of said ignition coil, at each of said spark plugs capacitive discharge is caused when said ignition coil secondary voltage reaches a dielectric breakdown voltage of a gap between electrodes of the spark plug and then sustained discharge is caused; ignition signal generating means for generating an AC signal synchronized with the rotation of the engine; control signal generating means responsive to said AC signal synchronized with the engine rotation to generate a control pulse signal having a first transition edge indicative of a time of starting flow of a primary current in said ignition coil and a second transition edge indicative of a time of interrupting the primary current flow and corresponding to the point of positive to negative transition of said AC signal synchronized with the engine rotation; control means responsive to said control pulse signal to control the primary current flow in said ignition coil; comparison means connected to said ignition signal generating means for comparing said AC signal synchronized with the engine rotation and a positive reference voltage so as to generate a pulse signal for a period of time during which said AC signal is greater than said reference voltage; first trigger pulse generating means responsive to the leading edge of said output pulse signal of said comparison means to generate a first trigger pulse; monostable circuit means responsive to said control pulse signal to generate a pulse signal for a predetermined period from the second transition edge of said control pulse signal; second trigger pulse generating means responsive to the trailing edge of said output pulse signal of said monostable circuit means to generate a second trigger pulse; a flip-flop circuit responsive to said first and second trigger pulses to generate a pulse signal having a duration for a time interval from the time of generation of said first trigger pulse to the time of generation of said second trigger pulse; an oscillator for generating repetitive pulses having a predetermined repetition rate; an AND circuit having a first input terminal for receiving said output pulse signal of said flip-flop circuit and a second input terminal for receiving said repetitive pulses from said oscillator for delivering the repetitive pulses during said time interval; switching means responsive to the output pulse signal of said AND circuit to perform on-off operations during said time interval; transformer means whose primary current is controlled in response to the operation of said switching means, to thereby generate a high voltage pulse in its secondary winding during said time interval; DC high voltage generating means for rectifying and smoothing said secondary high voltage pulse from said transformer means to generate during said time interval a DC high voltage which is lower than said dielectric breakdown voltage of spark plug gap in absolute value magnitude and which is higher than a voltage required to maintain said sustained discharge in absolute value magnitude; and output means connected to the secondary winding of said ignition coil and said DC high voltage generating means, whereby one of said secondary voltage generated by said ignition coil and said DC high voltage is selected in accordance with the relative levels thereof and supplied to the spark plug.

Claim 10

An ignition system for an internal combustion engine comprising: an ignition coil having a primary winding and a secondary winding for generating a secondary voltage including a high voltage generated by interruption of a primary current, said secondary voltage being decreased after occurrence of capacitive discharge at one of a plurality of spark plugs; said plurality of spark plugs each being supplied with said secondary voltage of said ignition coil, at each of said spark plugs capacitive discharge is caused when said ignition coil secondary voltage reaches a dielectric breakdown voltage of a gap between electrodes of the spark plug and then sustained discharge is caused; ignition signal generating means for generating an AC signal synchronized with the rotation of the engine; control signal generating means responsive to said AC signal synchronized with the engine rotation to generate a control pulse signal having a first transition edge indicative of a time of starting flow of a primary current in said ignition coil and a second transition edge indicative of a time of interrupting the primary current flow and corresponding to the point of positive to negative transition of said AC signal synchronized with the engine rotation; control means responsive to said control pulse signal to control the primary current flow in said ignition coil; comparison means connected to said ignition signal generating means for comparing said AC signal synchronized with the engine rotation and a positive reference voltage so as to generate a pulse signal for a period of time during which said AC signal is greater than said reference voltage; first trigger pulse generating means responsive to the leading edge of said output pulse signal of said comparison means to generate a first trigger pulse; monostable circuit means responsive to said control pulse signal to generate a pulse signal for a predetermined period from the second transition edge of said control pulse signal; second trigger pulse generating means responsive to the trailing edge of said output pulse signal of said monostable circuit means to generate a second trigger pulse; a flip-flop circuit responsive to said first and second trigger pulses to generate a pulse signal having a duration for a time interval from the time of generation of said first trigger pulse to the time of generation of said second trigger pulse; an oscillator for generating repetitive pulses having a predetermined repetition rate; an AND circuit having a first input terminal for receiving said output pulse signal of said flip-flop circuit and a second input terminal for receiving said repetitive pulses from said oscillator for delivering the repetitive pulses during said time interval; switching means responsive to the output pulse signal of said AND circuit to perform on-off operations during said time interval; transformer means whose primary current is controlled in response to the operation of said switching means, to thereby generate a high voltage pulse in its secondary winding during said time interval; DC high voltage generating means for rectifying and smoothing said secondary high voltage pulse from said transformer means to generate during said time interval a DC high voltage which is lower than said dielectric breakdown voltage of spark plug gap in absolute value magnitude and which is higher than a voltage required to maintain said sustained discharge in absolute value magnitude; and output means connected to the secondary winding of said ignition coil and said DC high voltage generating means, whereby one of said secondary voltage generated by said ignition coil and said DC high voltage is selected in accordance with the relative levels thereof and supplied to the spark plug.

Claim 11

An ignition system for an internal combustion engine comprising: an ignition coil having a primary winding and a secondary winding for generating a secondary voltage including a high voltage generated by interruption of a primary current, said secondary voltage being decreased after occurrence of capacitive discharge at one of a plurality of spark plugs; said spark plugs each being supplied with said secondary voltage of said ignition coil, at each of said spark plugs capacitive discharge is caused when said ignition coil secondary voltage reaches a dielectric breakdown voltage of a gap between electrodes of the spark plug and then sustained discharge is caused; ignition signal generating means for generating an AC signal synchronized with the rotation of the engine; control signal generating means responsive to said AC signal synchronized with the engine rotation to generate a control pulse signal having a first transition edge indicative of a time of starting flow of a primary current in said ignition coil and a second transition edge indicative of a time of interrupting the primary current flow; control means responsive to said control pulse signal to control the primary current flow in said ignition coil; a first monostable circuit responsive to said control pulse signal to generate a pulse signal having a duration for a predetermined time interval from the second transition edge of the control pulse signal to a predetermined time or crank angle; a second monostable circuit connected to said first monostable circuit to generate a pulse signal having a duration from the trailing edge of the output pulse signal of said first monostable circuit to a determined time; switching means responsive to the output pulse signal of said second monostable circuit so as to be turned on; DC high voltage generating means for generating a DC high voltage which is lower than said dielectric breakdown voltage of spark plug gap in absolute value magnitude and which is higher than a voltage required to maintain said sustained discharge in absolute value magnitude; DC high voltage output means connected to an output of said DC high voltage generating means and said switching means, whereby said DC high voltage is delivered when said switching means is off and a DC voltage lower than said voltage required to maintain said sustained discharge is generated when said switching means is on; and output means connected to the secondary winding of said ignition coil and said DC high voltage output means, whereby one of said secondary voltage generated by said ignition coil and said DC output voltage of said DC high voltage output means is selected in accordance with the relative levels thereof and supplied to the spark plug.

Claim 12

An ignition system for an internal combustion engine comprising: an ignition coil having a primary winding and a secondary winding for generating a secondary voltage including a high voltage generated by interruption of a primary current, said secondary voltage being decreased after occurrence of capacitive discharge at one of a plurality of spark plugs; said spark plugs each being supplied with said secondary voltage of said ignition coil, at each of said spark plugs capacitive discharge is caused when said ignition coil secondary voltage reaches a dielectric breakdown voltage of a gap between electrodes of the spark plug and then sustained discharge is caused; ignition signal generating means for generating an AC signal synchronized with the rotation of the engine; control signal generating means responsive to said AC signal synchronized with the engine rotation to generate a control pulse signal having a first transition edge indicative of a time of starting flow of a primary current in said ignition coil and a second transition edge indicative of a time of interrupting the primary current flow; control means responsive to said control pulse signal to control the primary current flow in said ignition coil; a first monostable circuit responsive to said control pulse signal to generate a pulse signal having a duration for a predetermined time interval from the second transition edge of the control pulse signal to a predetermined time or crank angle; a second monostable circuit connected to said first monostable circuit to generate a pulse signal having a duration from the trailing edge of the output pulse signal of said first monostable circuit to a determined time; switching means responsive to the output pulse signal of said second monostable circuit so as to be turned on; DC high voltage generating means for generating a DC high voltage which is lower than said dielectric breakdown voltage of spark plug gap in absolute value magnitude and which is higher than a voltage required to maintain said sustained discharge in absolute value magnitude; DC high voltage output means connected to an output of said DC high voltage generating means and said switching means, whereby said DC high voltage is delivered when said switching means is off and a DC voltage lower than said voltage required to maintain said sustained discharge is generated when said switching means is on; and output means connected to the secondary winding of said ignition coil and said DC high voltage output means, whereby one of said secondary voltage generated by said ignition coil and said DC output voltage of said DC high voltage output means is selected in accordance with the relative levels thereof and supplied to the spark plug.

Claim 13

An ignition system for an internal combustion engine comprising: an ignition coil having a primary winding and a secondary winding for generating a secondary voltage including a high voltage generated by interruption of a primary current, said secondary voltage being decreased after occurrence of a capacitive discharge at one of a plurality of spark plugs; said plurality of spark plugs each being supplied with said secondary voltage of said ignition coil, at each of said spark plugs capacitive discharge is caused when said secondary voltage reaches a dielectric breakdown voltage of a gap between electrodes of the spark plug and then sustained discharge is caused; ignition signal generating means for generating an AC signal synchronized with the rotation of the engine; control signal generating means responsive to said AC signal synchronized with the engine rotation to generate a control pulse signal having a first transition edge indicative of a time of starting flow of primary current in said ignition coil and a second transition edge indicative of a time of interrupting the primary current flow and corresponding to the point of positive to negative transition of said AC signal synchronized with the engine rotation; control means responsive to said control pulse signal to control the primary current flow in said ignition coil; comparison means connected to said ignition signal generating means for comparing said AC signal synchronized with the engine rotation and a positive reference voltage to generate a pulse signal for a period of time during which said AC signal is greater than said reference voltage; trigger pulse generating means responsive to the leading edge of said output pulse signal of said comparison means to generate a first trigger pulse; an oscillator for generating repetitive pulses having a predetermined repetition rate; a counter responsive to the second transition edge of said control pulse signal to start counting said repetitive pulses of said oscillator; memory means for storing a plurality of predetermined time periods or crank angles each corresponding to one of a plurality of engine conditions and for producing in accordance with a detected engine condition, a signal indicative of the corresponding one of said predetermined time periods or crank angles; a comparison circuit connected to said counter and said memory means to generate an output pulse as a second trigger pulse when the output of said counter coincides with the output of said memory means; a flip-flop circuit responsive to said first and second trigger pulses to generate a pulse signal having a duration for a time interval from the time of generation of said first trigger pulse to the time of generation of said second trigger pulse; an oscillator circuit for generating repetitive pulses of a predetermined repetition rate; an AND circuit having a first input terminal for receiving said output pulse signal of said flip-flop circuit and a second input terminal for receiving said repetitive pulses from said oscillator circuit to deliver said repetitive pulses signal during said time interval; switching means responsive to the output pulse signal of said AND circuit to perform on-off operations during said time interval; transformer means whose primary current is controlled in response to the operation of said switching means, to thereby generate a high voltage pulse in its secondary winding during said time interval; DC high voltage generating means for rectifying and smoothing said secondary high voltage pulse from said transformer means to generate during said time interval a DC high voltage which is lower than said dielectric breakdown voltage of spark plug gap in absolute value magnitude and which is higher than a voltage required to maintain said sustained discharge in absolute value magnitude; and output means connected to the secondary winding of said ignition coil and said DC high voltage generating means, whereby one of said secondary voltage generated by said ignition coil and said DC high voltage is selected in accordance with the relative levels thereof and supplied to the spark plug.

Claim 14

An ignition system for an internal combustion engine comprising: an ignition coil having a primary winding and a secondary winding for generating a secondary voltage including a high voltage generated by interruption of a primary current, said secondary voltage being decreased after occurrence of a capacitive discharge at one of a plurality of spark plugs; said plurality of spark plugs each being supplied with said secondary voltage of said ignition coil, at each of said spark plugs capacitive discharge is caused when said secondary voltage reaches a dielectric breakdown voltage of a gap between electrodes of the spark plug and then sustained discharge is caused; ignition signal generating means for generating an AC signal synchronized with the rotation of the engine; control signal generating means responsive to said AC signal synchronized with the engine rotation to generate a control pulse signal having a first transition edge indicative of a time of starting flow of primary current in said ignition coil and a second transition edge indicative of a time of interrupting the primary current flow and corresponding to the point of positive to negative transition of said AC signal synchronized with the engine rotation; control means responsive to said control pulse signal to control the primary current flow in said ignition coil; comparison means connected to said ignition signal generating means for comparing said AC signal synchronized with the engine rotation and a positive reference voltage to generate a pulse signal for a period of time during which said AC signal is greater than said reference voltage; trigger pulse generating means responsive to the leading edge of said output pulse signal of said comparison means to generate a first trigger pulse; an oscillator for generating repetitive pulses having a predetermined repetition rate; a counter responsive to the second transition edge of said control pulse signal to start counting said repetitive pulses of said oscillator; memory means for storing a plurality of predetermined time periods or crank angles each corresponding to one of a plurality of engine conditions and for producing in accordance with a detected engine condition, a signal indicative of the corresponding one of said predetermined time periods or crank angles; a comparison circuit connected to said counter and said memory means to generate an output pulse as a second trigger pulse when the output of said counter coincides with the output of said memory means; a flip-flop circuit responsive to said first and second trigger pulses to generate a pulse signal having a duration for a time interval from the time of generation of said first trigger pulse to the time of generation of said second trigger pulse; an oscillator circuit for generating repetitive pulses of a predetermined repetition rate; an AND circuit having a first input terminal for receiving said output pulse signal of said flip-flop circuit and a second input terminal for receiving said repetitive pulses from said oscillator circuit to deliver said repetitive pulses signal during said time interval; switching means responsive to the output pulse signal of said AND circuit to perform on-off operations during said time interval; transformer means whose primary current is controlled in response to the operation of said switching means, to thereby generate a high voltage pulse in its secondary winding during said time interval; DC high voltage generating means for rectifying and smoothing said secondary high voltage pulse from said transformer means to generate during said time interval a DC high voltage which is lower than said dielectric breakdown voltage of spark plug gap in absolute value magnitude and which is higher than a voltage required to maintain said sustained discharge in absolute value magnitude; and output means connected to the secondary winding of said ignition coil and said DC high voltage generating means, whereby one of said secondary voltage generated by said ignition coil and said DC high voltage is selected in accordance with the relative levels thereof and supplied to the spark plug.