Conventionally, a hydraulic valve timing control apparatus is equipped with a housing rotor rotating with a crankshaft and a vane rotor rotating with a camshaft. JP H11-141315A describes such valve timing control apparatus which controls a rotation phase of a vane rotor relative to a housing rotor by a flow of hydraulic fluid relative to an advance chamber and a retard chamber which are defined by the vane rotor inside the housing rotor.
In JP H11-141315A, the flow of hydraulic fluid is controlled by a control valve. Specifically, the control valve has a first port communicating with the advance chamber and a second port communicating with the retard chamber. When an internal combustion engine is stopped, each of the first port and the second port is made to communicate with an atmospheric port. At this time, discharge of the hydraulic fluid from an advance chamber and a retard chamber through the atmospheric port is regulated by a block valve. Therefore, at the next time of starting the engine, hydraulic fluid is immediately introduced to the retard chamber, so as to control abnormal noise caused by abnormal movement of the vane rotor. In JP H11-141315A, the rotation phase is locked at a predetermined lock phase by a lock mechanism at a time of stopping and starting the engine.
USPTO Backgrounds
USPTO Backgrounds