VCT system having robust closed loop control employing dual loop approach having hydraulic pilot stage with a PWM solenoid

In an internal combustion engine having a rotatable crankshaft and a rotatable camshaft, the camshaft being position variable relative to the crankshaft and being subject to torque reversals during the operation thereof, the method comprising:

• providing the camshaft with a vane having at least one lobe, the vane being rotatable with the camshaft and being non-oscillatable with respect to the camshaft;
• providing the camshaft with a housing having at least one recess, the housing being rotatable with the camshaft and being oscillatable with respect to the camshaft, the at least one recess of the housing receiving the at least one lobe of the vane and permitting oscillation of the at least one lobe within the at least one recess as the housing oscillates with respect to the camshaft;
• providing means for transmitting rotary movement from the crankshaft to the housing;
• providing means for varying the position of the housing relative to the camshaft in reaction to torque reversals in the camshaft, said means delivering hydraulic fluid to said vane;
• providing check valve means functionally positioned between said housing and said means for varying the position of the housing to eliminate the need for blocking a backflow of hydraulic fluid by the operation of said means for varying the position of said housing;
• providing actuating means for supplying hydraulic fluid to said means for varying the position of the housing;
• providing processing means for controlling the on-off pulses of said actuating means by generating a PWM duty cycle to said actuating means;
• and
• providing sensing means for determining a phase angle between the crankshaft and the camshaft and issuing a feedback signal to said processing means.

An internal combustion engine comprising:

• a crankshaft, said crankshaft being rotatable about an axis;
• a camshaft, said camshaft being rotatable about a second axis, said second axis being parallel to said axis, said camshaft being subject to torque reversals during the rotation thereof;
• a vane, said vane having at least one lobe, said vane being attached to said camshaft, being rotatable with said camshaft and being non-oscillatable with respect to said camshaft;
• a housing, said housing being rotatable with said camshaft and being oscillatable with respect to said camshaft, said housing having at least one recess, said at least one recess receiving said at least one lobe, said at least one lobe being oscillatable within said at least one recess;
• rotary movement transmitting means for transmitting rotary movement from the crankshaft to the housing;
• and
• means reactive to torque reversals in the camshaft for varying the position of the housing relative to the camshaft by permitting the housing to move in a first direction relative to the camshaft in reaction to a torque pulse in the camshaft in a first direction and for preventing the housing from moving in a second direction relative to the camshaft in reaction to a torque pulse in the camshaft in a second direction.