Internal combustion engine combustion state detecting device

An internal combustion engine combustion state detecting device, comprising:

• a spark plug that has a first electrode and a second electrode opposing across a gap and ignites a combustible mixture in a combustion chamber of an internal combustion engine by generating a spark discharge in the gap;
• an ignition device including a primary winding and a secondary winding magnetically coupled to the primary winding;
• a power supply device that supplies current to the primary winding;
• switches, disposed between the primary winding and the power supply device, that control a conduction and an interruption of the current supplied by the power supply device;
• an ionic current detecting circuit that detects as an ionic current ions generated in the combustion chamber by a combustion of the combustible mixture caused by voltage applied between the first electrode and the second electrode;
• a recirculating device that short-circuits the primary winding, thereby energizing a recirculation path and stopping the spark discharge;
• and
• a discharge stopping-induced current detecting device that estimates an induced current caused by the stopping of the spark discharge, wherein
• the primary winding supplies the current by the switches being switched to an energizing state, and accumulates energy that causes the spark plug to generate the spark discharge that ignites the combustible mixture,
• the current is interrupted by the switches being switched to an interrupting state in a state in which the energy is accumulated in the primary winding, a high voltage is generated in the secondary winding, and the spark discharge is generated by the high voltage in the gap of the spark plug.