Apparatus for detecting rotational position of internal combustion engine

An apparatus for detecting a rotational position of an internal combustion engine comprising:

• a rotational angle sensor outputting a rotation angle signal indicative of a rotational angle of said internal combustion engine;
• an in-cylinder pressure sensor outputting an in-cylinder pressure signal indicative of an in-cylinder pressure of a cylinder of said internal combustion engine;
• and
• a reference rotational position detecting section configured to:
• detect a first rotational angle of said internal combustion engine at which said in-cylinder pressure detected by said in-cylinder pressure sensor reaches a maximum value when said internal combustion engine is in a non-combustion condition, to determine said detected first rotational angle as a top dead center position of said cylinder equivalent to said reference rotational position of said internal combustion engine, and
• detect, when each of an intake air pressure and a rotational speed of said internal combustion engine is at a predetermined value, a second rotational angle of said internal combustion engine at which said in-cylinder pressure becomes a predetermined pressure before fuel ignites in said cylinder during a compression cycle of said cylinder when the internal combustion engine is in a combustion condition, to determine said detected second rotational angle as said reference rotational position.