To accurately grasp a change amount of the rotational angle of a rotating body even in an abnormal situation in which an output signal of a first sensor unit no longer varies from a prescribed level.
A crank position sensor 42 has a main sensor 61 and a sub-sensor 62 that output pulse-shaped signals each time a crankshaft 31 rotates by a prescribed angle, and these sensors output signals mutually shifted in phase; when the condition that a sub-signal is at a high level and a main signal has varied is satisfied, a crank signal of a pulse width varying according to the direction of main signal variation is outputted; an ECU 41 judges whether or not an abnormal situation in which the sub-signal no longer varies from the high level has occurred and, if it judges that the abnormal situation has occurred, converts the number of the outputted crank signals into the number of crank signals at normal times on the basis of the relationship of correspondence among the pulse width of the crank signals, the number of engine revolutions and the number of crank signals outputted in the abnormal situation.
NAKAMURA YOSHIFUMI
YOSHIHARA MASATOMO
MASUDA SATORU
DENSO CORP
Makoto Onda
Next Patent: STEEL PLATE SURFACE INSPECTION METHOD AND APPARATUS