Control device for engine

A control device for controlling an engine including an injector that supplies fuel into a cylinder and an in-cylinder pressure sensor that detects an in-cylinder pressure being a pressure inside the cylinder, comprising:

• a processor configured to execute an abnormal combustion determining module to determine whether combustion of a mixture gas inside the cylinder is abnormal based on a detection value of the in-cylinder pressure sensor, the abnormal combustion determining module determining that abnormal combustion has occurred in which progress of the combustion of the mixture gas is excessively fast, when an in-cylinder pressure intensity that is a spectrum value of a frequency component of an in-cylinder pressure waveform detected by the in-cylinder pressure sensor less than a given reference frequency is greater than or equal to a given determination intensity, wherein the abnormal combustion determining module includes:
• a filtering module configured to extract a frequency component less than the reference frequency and greater than a given second reference frequency from the in-cylinder pressure waveform detected by the in-cylinder pressure sensor;
• an intensity calculating module configured to calculate a value of the spectrum of the extracted frequency component as the in-cylinder pressure intensity;
• and
• a determining module configured to determine that the abnormal combustion has occurred when the in-cylinder pressure intensity calculated by the intensity calculating module is greater than or equal to the determination intensity;
• and
• an ignition plug configured to ignite the mixture gas inside the cylinder at a given ignition timing,
• wherein the abnormal combustion determining module determines that a first abnormal combustion, in which the progress of the combustion of the mixture gas is changeable by changing the ignition timing, has occurred when an index period from the ignition timing to a timing of completion of combustion of a given rate of fuel supplied to the cylinder in one combustion cycle is a given determination period or longer and the in-cylinder pressure intensity is greater than or equal to the determination intensity, and determines that a second abnormal combustion, in which the progress of the combustion of the mixture gas is not changeable by changing the ignition timing, has occurred when the index period is shorter than the determination period and the in-cylinder pressure intensity is greater than or equal to the determination intensity.