Variable valve timing control apparatus for internal combustion engine

A variable valve timing control apparatus for an internal combustion engine that has:

• a crankshaft;
• a camshaft;
• a hydraulic variable valve timing unit configured to adjust valve timing by changing a variable cam timing (VCT) phase that is a rotational phase of the camshaft relative to the crankshaft;
• a lock pin configured to lock the VCT phase at an intermediate lock position located within an adjustable range of the VCT phase;
• and
• a hydraulic control valve configured to control oil pressure that actuates the variable valve timing unit and the lock pin, the variable valve timing control apparatus comprising:
• VCT control means for switching a control, based on an operational state, between (a) a VCT phase control for controlling the VCT phase to a target phase and (b) a lock pin projection control for allowing the lock pin to project;
• and
• foreign object release control means for executing, when an abnormality occurs, a foreign object release control for changing a control amount of the hydraulic control valve based on a predetermined pattern, wherein:
• the VCT control means executes, upon generation of a lock request, a lock trial control, in which the VCT phase is temporarily shifted in a first direction to pass the intermediate lock position by a predetermined passing amount and then the VCT control means executes the lock pin projection control in order to lock the VCT phase by the lock pin while the VCT phase is shifted in a second direction opposite from the first direction back to the intermediate lock position;
• when the lock of the VCT phase has not been completed after the lock pin projection control has been executed for a predetermined period, the predetermined passing amount is adjusted, and the lock trial control is repeated until the lock is completed;
• and
• when the lock of the VCT phase has not been completed even after a number of times of executing the lock trial control reaches a predetermined number of times, the foreign object release control means determines that the abnormality of a lock occurs and executes the foreign object release control.

A variable valve timing control apparatus for an internal combustion engine that has:

• a crankshaft;
• a camshaft;
• a hydraulic variable valve timing unit configured to adjust valve timing by changing a variable cam timing (VCT) phase that is a rotational phase of the camshaft relative to the crankshaft;
• a lock pin configured to lock the VCT phase at an intermediate lock position located within an adjustable range of the VCT phase;
• and
• a hydraulic control valve configured to control oil pressure that actuates the variable valve timing unit and the lock pin, the variable valve timing control apparatus comprising:
• VCT control means for switching a control, based on an operational state, between (a) a VCT phase control for controlling the VCT phase to a target phase and (b) a lock pin projection control for allowing the lock pin to project;
• and
• foreign object release control means for executing, when an abnormality occurs, a foreign object release control for changing a control amount of the hydraulic control valve based on a predetermined pattern, wherein:
• the VCT control means executes a lock release control when a lock release request is generated;
• the lock release control includes:
• a pin retraction control, in which the lock pin is retracted in a lock release direction while a driving force for shifting the VCT phase in an advance direction or in a retard direction is regulated to be equal to or less than a predetermined value;
• and
• the VCT phase control that is executed after the pin retraction control has been executed for a predetermined period;
• the VCT control means further executes the lock release control once or more when the VCT phase has not been shifted from the intermediate lock position after the VCT phase control has been executed for a predetermined period;
• and
• the foreign object release control means determines that the abnormality of a lock release occurs and executes the foreign object release control when the VCT phase has still not been shifted from the intermediate lock position even after the further execution of the lock release control.