Variable valve timing control apparatus for internal combustion engine

Abstract

A variable valve timing control apparatus for an engine includes a variable valve timing unit, a lock pin, a hydraulic control unit, and an oil filling control unit. An operation mode of the hydraulic control unit is changed between a lock mode, in which the lock pin locks the camshaft phase at the intermediate lock phase, and a phase feed-back control mode, in which the camshaft phase is controlled to a target phase. The oil filling control unit supplies oil to an advance chamber and a retard chamber of the variable valve timing unit before the operation mode is changed from the lock mode to the phase feed-back control mode after an engine start. The oil filling control unit causes the lock pin to keep locking the camshaft phase until the oil filling control is completed after the engine start.

1 . A variable valve timing control apparatus for an internal combustion engine that has a camshaft and a crankshaft, comprising:
 a variable valve timing unit adapted to adjust valve timing by shifting a camshaft phase that is a rotational angular position of the camshaft relative to a rotational angular position of the crankshaft;   a lock pin adapted to lock the camshaft phase at an intermediate lock phase that is generally middle of an adjustable range of the camshaft phase;   a hydraulic control unit adapted to control oil pressure that actuates the variable valve timing unit and the lock pin, wherein an operation mode of the hydraulic control unit is changed between a lock mode, in which the lock pin locks the camshaft phase at the intermediate lock phase, and a phase feed-back control mode, in which the camshaft phase is controlled to a target phase; and   oil filling control means for executing oil filling control for supplying oil to an advance chamber and a retard chamber of the variable valve timing unit before the operation mode is changed from the lock mode to the phase feed-back control mode after a start of the internal combustion engine, wherein:   the oil filling control means causes the lock pin to keep locking the camshaft phase by prohibiting the lock pin from releasing the locked camshaft phase until the oil filling control is completed after the start of the internal combustion engine.   
   
   
       2 . The variable valve timing control apparatus according to  claim 1 , wherein:
 the oil filling control means executes the oil filling control until a certain time period elapses since the start of the internal combustion engine.   
   
   
       3 . The variable valve timing control apparatus according to  claim 1 , wherein:
 the hydraulic control unit includes a first hydraulic control valve and a second hydraulic control valve, the first hydraulic control valve controlling oil pressure for actuating the variable valve timing unit, the second hydraulic control valve controlling oil pressure for actuating the lock pin;   the oil filling control means maintains a control amount of the second hydraulic control valve at a value for causing the lock pin to keep locking the camshaft phase during an execution period for executing the oil filling control; and   the oil filling control means also changes a control amount of the first hydraulic control valve during the execution period in order to firstly execute one of (a) advance chamber oil filling control for supplying oil to the advance chamber and (b) retard chamber oil filling control for supplying oil to the retard chamber and in order to subsequently execute the other one of (a) the advance chamber oil filling control and (b) the retard chamber oil filling control.   
   
   
       4 . The variable valve timing control apparatus according to  claim 1 , wherein:
 the oil filling control means stops the oil filling control and changes a control amount of the hydraulic control unit such that the camshaft phase is controlled to a full retard phase or a full advance phase when it is detected that the lock pin does not lock the camshaft phase based on detection of change of the camshaft phase during the execution of the oil filling control.   
   
   
       5 . The variable valve timing control apparatus according to  claim 4 , wherein:
 a target idling rotational speed of the internal combustion engine indicates a first value while the lock pin locks the camshaft phase; and   the oil filling control means includes means for increasing the target idling rotational speed after the start of the internal combustion engine to be a second value that is higher than the first value when it is detected that the lock pin does not lock the camshaft phase during the execution of the oil filling control.   
   
   
       6 . The variable valve timing control apparatus according to  claim 4 , wherein:
 when it is detected that the lock pin does not lock the camshaft phase during the execution of the oil filling control, the oil filling control means executes the followings:   the oil filling control means stops the oil filling control; and   the operation mode is changed to a normal control after the oil filling control means controls the camshaft phase at a full retard phase or at a full advance phase until a certain time period that is shorter than a time required for completing the oil filling control elapses.   
   
   
       7 . The variable valve timing control apparatus according to  claim 1 , wherein:
 the hydraulic control unit employs a hydraulic control valve that controls oil pressure for actuating the variable valve timing unit and the lock pin:   the oil filling control means changes a control amount of the hydraulic control valve such that oil is firstly supplied to one of the advance chamber and the retard chamber while the lock pin locks the camshaft phase after the start of the internal combustion engine; and   the oil filling control means changes the control amount of the hydraulic control valve such that oil is subsequently supplied to the other one of the advance chamber and the retard chamber until a certain time period elapses or until the camshaft phase starts shifting when a first lock release request since the engine start is issued.   
   
   
       8 . The variable valve timing control apparatus according to  claim 7 , wherein:
 when it is detected that the lock pin does not lock the camshaft phase during the execution of the oil filling control, the operation mode is changed to a normal control after the oil filling control means supplies oil to the other one of the advance chamber and the retard chamber.