Patent ID: 8076899

Claim:
A valve timing control apparatus that controls valve timing of at least one valve of an internal combustion engine, which is driven by a camshaft upon transmission of a torque from a crankshaft of the internal combustion engine to open and close the at least one valve, the valve timing control apparatus comprising: an electric motor that includes: a plurality of stator coils, each of which generates a magnetic field upon energization thereof; and a motor shaft, which is driven to rotate by action of the magnetic field of each corresponding one of the plurality of stator coils; a plurality of switching elements, each of which is connected to a corresponding one of the plurality of stator coils; an electric power supply driving means for driving the motor shaft by sequentially changing at least one on-state switching element to be turned on among the plurality of switching elements to supply electric power to each corresponding one of the plurality of stator coils; and a phase adjusting mechanism that adjusts a relative phase between the crankshaft and the camshaft in response to a rotational state of the motor shaft, wherein: the electric power supply driving means executes duty control of turning on and off of a selected switching element, which is selected from the at least one on-state switching element, to supply the electric power to the corresponding one of the plurality of stator coils in a case where an actual rotational direction of the motor shaft and a target rotational direction of the motor shaft coincide with each other; the electric power supply driving means sets an on-duty ratio of the selected switching element below a lower limit value, which is at least required to rotate the motor shaft through the power supply to each corresponding one of the plurality of stator coils, in a case where the actual rotational direction of the motor shaft and the target rotational direction of the motor shaft do not coincide with each other; the phase adjusting mechanism includes an input rotator that is rotated in a normal rotational direction by the transmission of the torque from the crankshaft and is rotatable together with the motor shaft in the normal rotational direction or a reverse rotational direction; the phase adjusting mechanism adjusts the relative phase in response to the rotational state of the motor shaft and the input rotator; and the electric power supply driving means sets the on-duty ratio of the selected switching element below the lower limit value in a case where the actual rotational direction of the motor shaft is the normal rotational direction, and the target rotational direction of the motor shaft is the reverse rotational direction.