Control apparatus of variable valve timing system for internal combustion engine

A control apparatus of a variable valve timing system for an internal combustion engine, comprising:

• a sensor that detects an angular phase of a camshaft relative to a crankshaft;
• a return spring that returns the angular phase of the camshaft to an initial position;
• and
• an electronic control unit configured to be electronically connected to the variable valve timing system to variably control a valve timing by changing the angular phase of the camshaft against a spring bias of the return spring and execute a revertive control by which the angular phase of the camshaft is returned to the initial position, said electronic control unit comprising a processor programmed to perform the following:
• (a) executing a feedback control that temporarily halts the angular phase of the camshaft at a predetermined position, which is phase-changed by a predetermined phase angle from the initial position, during the revertive control;
• and
• (b) switching to a feedforward control after the feedback control, so as to return the angular phase of the camshaft to the initial position.

A control apparatus of a variable valve timing system for an internal combustion engine, comprising:

• a sensing means for detecting an angular phase of a camshaft relative to a crankshaft;
• a return spring for returning the angular phase of the camshaft to an initial position;
• and
• an electronic control unit configured to be electronically connected to the variable valve timing system to variably control a valve timing by changing the angular phase of the camshaft against a spring bias of the return spring and execute a revertive control by which the angular phase of the camshaft is returned to the initial position, said electronic control unit comprising:
• (a) a feedback control means for executing a feedback control that temporarily halts the angular phase of the camshaft at a predetermined position, which is phase-changed by a predetermined phase angle from the initial position, during the revertive control that the angular phase of the camshaft is adjusted toward the predetermined position;
• and
• (b) a feedforward control means for initiating a feedforward control after the feedback control, so as to return the angular phase of the camshaft from the predetermined position to the initial position.

A soft-landing revertive control method of returning an actual angular phase of a camshaft relative to a crankshaft to an initial position by controlling the actual angular phase of the camshaft in a variable valve timing system for an internal combustion engine, employing a return spring creating a spring bias acting in a direction that returns the actual angular phase of the camshaft to an initial position and an electromagnetic brake creating an electromagnetic force acting against the spring bias, the method comprises:

• de-energizing the electromagnetic brake;
• calculating a target angular phase of the camshaft based on engine operating conditions;
• comparing the target angular phase to a predetermined position, which is phase-changed by a predetermined phase angle from the initial position;
• comparing the actual angular phase to the predetermined position;
• executing a feedback control that temporarily halts the actual angular phase of the camshaft at the predetermined position after the target angular phase reaches the predetermined position and the actual angular phase also reaches the predetermined position;
• and
• switching an operating mode of the variable valve timing system from the feedback control to a feedforward control after the feedback control has been continuously executed for a predetermined time period from a time when the actual angular phase has reached the predetermined position.