Patent ID: 8701629

Claim:
An internal-combustion-engine combustion state detecting apparatus comprising: an ignition device that generates a plurality of ignition signals during a single compression stroke or power stroke of an internal combustion engine so as to ignite and burn an inflammable fuel-air mixture taken in into a combustion chamber in a cylinder of the internal combustion engine; an ion detection device that is provided in the ignition device and detects an electric quantity based on an ion that occurs in the combustion chamber due to combustion of the fuel-air mixture; an ending timing detection device that detects an ending timing of the detected electric quantity; a comparison timing device that sets a comparison timing; a combustion diagnosis device that compares the detected ending timing with the set comparison timing and then diagnoses a combustion state of the internal combustion engine, based on the result of the comparison; and a level comparison device sets a comparison level in accordance with a peak hold value of the electric quantity, wherein the comparison timing is set in such a way as to be advanced in terms of the rotation angle of a crankshaft of the internal combustion engine with respect to the ending timing of an electric quantity based on an ion that occurs when ignition is performed normally through a predetermined ignition signal among the plurality of ignition signals, wherein combustion diagnosis device determines normal combustion occurs in response to the detected ending timing of the electrical quantity following the set comparison timing in terms of the rotation angle of a crankshaft of the internal combustion engine; and determines that abnormal combustion occurs in response to the detected ending timing preceding the set comparison timing in terms of the rotation angle of the crankshaft.