Combustion state detection apparatus for internal combustion engine

A combustion state detection apparatus for an internal combustion engine comprising:

• an angle sensor which detects a revolution angle of the internal combustion engine;
• an ECU which performs fuel injection and ignition control based on revolution information from the angle sensor;
• an ignition coil which generates a high voltage for ignition based on a driving signal from the ECU;
• a spark plug which generates an ignition spark to ignite mixed gas by applying the high voltage for ignition of the ignition coil;
• a bias section which applies a bias voltage for ion current detection to the spark plug;
• an ion current detection section which detects an ion current;
• at least one of a misfire detection section, which performs misfire detection based on the ion current detected by the ion current detection section, and a knock detection section, which performs knock detection based on the ion current detected by the ion current detection section;
• at least one of a misfire determination section and a knock determination section, which performs one of misfire determination and knock control based on an output signal of the at least one of the misfire detection section and the knock detection section;
• and
• a detection period limit section which limits a detection period of the ion current processed in the at least one of the misfire detection section and the knock detection section.