Patent ID: 7921699

Claim:
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 which detects a specific rotational angle of said internal combustion engine at which said in-cylinder pressure becomes a predetermined reference pressure under a predetermined running condition of said internal combustion engine on the basis of said rotation angle signal and said in-cylinder pressure signal, and determines said detected specific rotational angle as a reference rotational position of said internal combustion engine; wherein said reference rotational position detecting section detects said specific rotational angle at least a predetermined plural number of times when said internal combustion engine is in a combustion state, and determines an average value of said detected specific rotational angle as said reference rotational position.