VCT solenoid dither frequency control

摘要

A method that uses a dither signal (38) for reducing hysteresis effect in a variable cam timing system (10) is provided. The method includes the steps of: a) providing (82) a dither signal (38) having at least two switchable frequencies; b) determining (86) the frequency characteristics of an engine speed; c) determining (86) at least one frequency beating point in relation to a neighborhood (66) of an engine crank RPM values; and d) changing (88) the dither signal frequency when the engine is operating within the neighborhood (66) of the engine crank RPM values. Thereby frequency beating effect is reduced.