Patent ID: 7673614

Claim:
An internal-combustion-engine combustion condition detection apparatus comprising: an ignition means for activating an ignition plug that ignites a fuel-air mixture taken into a combustion chamber; an ignition control means for generating a control signal for controlling operation of the ignition means; an ion-current detection means for detecting an ion current that occurs when the fuel-air mixture combusts; an ion current detection range setting means for setting a detection range for an ion current to be detected by the ion-current detection means; a preignition detection means for detecting preignition or a precursor phenomenon of preignition, based on an ion current detected within a detection range set by the ion current detection range setting means; a leakage current detection range setting means for setting a detection range for a leakage current caused by an ignition-plug smolder; and a leakage current determination means for determining whether or not an ignition-plug smolder exists, based on a current detected, within a detection range set by the leakage current detection range setting means, by the ion-current detection means, wherein the ignition control means includes a non-combustion-stroke ignition control means that makes the ignition plug perform ignition during a fuel-air mixture non-combustion stroke, and wherein the leakage-current detection range set by the leakage current detection range setting means is set within the non-combustion stroke.