VCT solenoid dither frequency control

摘要

A method that uses a dither signal for reducing hysteresis effect in a variable cam timing system is provided. The method includes the steps of: a) providing a dither signal having at least two switchable frequencies; b) determining the frequency characteristics of an engine speed; c) determining at least one frequency beating point in relation to a neighborhood of an engine crank RPM values; and d) changing the dither signal frequency when the engine is operating within the neighborhood of the engine crank RPM values. Thereby frequency beating effect is reduced.