Patent ID: 7444262

Claim:
A device for use in an internal combustion engine having an output shaft for detecting reverse rotation of the output shaft, the device comprising: a sensor for outputting a pulse signal whenever the output shaft is rotated by a predetermined angle; a rotation angle calculation unit for executing an elimination process, in which a predetermined proportion of pulse signals are eliminated from a sequence of the pulse signals, and determining a rotation angle of the output shaft based on a remaining signal obtained through the elimination process; and a reverse rotation detection unit for detecting reverse rotation of the output shaft based on the pulse signals; wherein when rotation speed of the output shaft becomes lower than a predetermined threshold, the rotation angle calculation unit suspends the elimination process and determines the rotation angle of the output shaft based on the pulse signals that have not undergone the elimination process, and the reverse rotation detection unit detects reverse rotation of the output shaft based on the pulse signals that have not undergone the elimination process.