PURPOSE: To restrain misjudgement of occurrence of knocking by creating the reference value for judging the existence/absence of knocking with good accuracy.
CONSTITUTION: The reference value for judgement of knocking is created according to signals in a section (noise judgement section) except a preset period immediately after the ignition timing of air-fuel mixture among output signals of a vibration sensor. When the above created reference value is less than a preset lower limit value, the reference value is re-created to a preset lower limit value. Accordingly, even if an engine is operated in a stable region with small vibration, the reference value is set with good accuracy. Then, signals outside the above noise judgement section among the output signals of a vibration sensor are compared with the above created or re-created reference value. When the signal exceeds the reference value, the occurrence of knocking can be correctly decided.
ENDO KOJI
NIINAI SUSUMU
