A cam sensor is provided in a position opposing one surface side of a cam
driven sprocket in a valve timing control device. When the valve timing
control device is in a high revolution state, a weight is pivoted by
centrifugal force caused by the rotation. This allows a projection at the
weight to be detected by the cam sensor. In this case, for each rotation
of the valve timing control device, the projection of the weight passes
the detectable position of the cam sensor and a pulse is generated in a
cam signal to be transmitted from the cam sensor to an ECU.