To accurately determine the existence of abnormality of a valve characteristic value sensor of a variable valve system.
A variable valve mechanism 9 is arranged on a camshaft 6 for driving an intake valve 2 of an engine 1, and a valve opening characteristic value of the intake valve is changed according to an engine operation state by moving the camshaft in the axial direction. The camshaft is provided with the valve characteristic value sensor 16 for detecting a present valve opening characteristic value by measuring a moving distance in the axial direction. An electronic control unit (ECU) 22 of the engine calculates an inside EGR gas quantity of the engine on the basis of a new air flow rate detected by an air flowmeter 19 and an intake air quantity calculated on the basis of engine intake pressure and an engine speed. When this gas quantity has a difference by a prescribed value or more from the inside EGR gas quantity calculated on the basis of an engine valve characteristic value, determination is made that the abnormality is caused in the valve characteristic value sensor.
KAWASAKI TAKASHI
Jun Tsuruta
Tetsuro Shimada
Masaya Nishiyama
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