ACTUATOR AND CONTROL METHOD FOR VARIABLE VALVE TIMING (VVT) MECHANISM

摘要

A variable valve timing system includes a toothed rotating sleeve, a rack, and an actuator. The rack has a first end, a second end with a plurality of teeth in meshing contact with the teeth of rotating sleeves of the valve and being linearly moveable to rotate the sleeves. The actuator includes a housing, a control valve, and at least one check valve. The housing slidably receives a piston coupled to the rack separating a chamber in the housing into first and second chambers. The control valve selectively directs fluid from the first to the second chamber or vice versa. When the rack is shifted linearly by vibrational impulses from the engine, the piston moves linearly within the housing, pressurizing the first or the second chamber and under control of the control valve, fluid recirculates from the first or the second chamber to the other chamber.