Ignition system

An ignition system comprising an ignition plug that applies a voltage to a discharge gap to generate a discharge spark to ignite fuel in a combustion chamber of an engine, and an ignition control unit that controls the ignition plug;

• the ignition control unit performing ignition control after top dead center to perform the ignition after the compression top dead center when the engine is in a predetermined operating state;
• the combustion chamber being divided into a main chamber and an auxiliary chamber by a partition wall provided with a plurality of communication holes, so that airflow flows from the inside of the auxiliary chamber through the communication holes into the main chamber after the compression top dead center;
• the discharge gap being disposed in the auxiliary chamber or in a predetermined communication hole among the plurality of communication holes while being closest to the predetermined communication hole;
• and
• at the time of the ignition control after top dead center, the discharge spark is extended by airflow through the predetermined communication hole into the main chamber.

An ignition system comprising an ignition plug that applies a voltage to a discharge gap to generate a discharge spark to ignite fuel in a combustion chamber of an engine, and an ignition control unit that controls the ignition plug;

• the ignition control unit performing ignition control after top dead center to perform the ignition after the compression top dead center when the engine is in a predetermined operating state;
• the combustion chamber being divided into a main chamber and an auxiliary chamber by a partition wall provided with one or a plurality of communication holes, so that airflow flows from the inside of the auxiliary chamber through a predetermined communication hole among the one or a plurality of communication holes into the main chamber after the compression top dead center;
• the discharge gap being provided in the auxiliary chamber;
• and
• at the time of the ignition control after top dead center, the discharge spark is extended toward the predetermined communication hole by airflow flowing from the inside of the auxiliary chamber through the predetermined communication hole into the main chamber;
• and
• the ignition control unit controls the ignition plug such that the discharge spark is maintained for a period of time equal to or longer than a required period as a minimum required period for the discharge spark to be extended into the main chamber through the predetermined communication hole after the discharge spark is generated at the time of the ignition control after top dead center.