Patent ID: 7506621

Claim:
A valve timing control system for an internal combustion engine, comprising: a variable valve timing mechanism that includes: an advance chamber that exerts a drive hydraulic pressure in an advance operation to rotate an output-side rotor, which drives a camshaft of the internal combustion engine, toward an advance side relative to an input-side rotor, which is driven by a crankshaft of the internal combustion engine; and a retard chamber that exerts a drive hydraulic pressure in a retard operation to rotate the output-side rotor toward a retard side relative to the input-side rotor; a phase control valve that supplies and drains the drive hydraulic pressure relative to the advance chamber and the retard chamber; a hydraulic control arrangement that controls hydraulic communication between the variable valve timing mechanism and the phase control valve and includes at least one of: a combination of an advance check valve and an advance drain control valve, wherein the advance check valve is provided in an advance hydraulic passage, which conducts a control hydraulic pressure of the phase control valve to the advance chamber, to enable hydraulic fluid to flow from the phase control valve to the advance chamber and to limit the hydraulic fluid to flow from the advance chamber to the phase control valve, and the advance drain control valve is provided in an advance check valve bypass passage, which bypasses the advance check valve, and is driven by a pilot hydraulic pressure to open and close the advance check valve bypass passage; a combination of a retard check valve and a retard drain control valve, wherein the retard check valve is provided in a retard hydraulic passage, which conducts the control hydraulic pressure of the phase control valve to the retard chamber, to enable hydraulic fluid to flow from the phase control valve to the retard chamber and to limit the hydraulic fluid to flow from the retard chamber to the phase control valve, and the retard drain control valve is provided in a retard check valve bypass passage, which bypasses the retard check valve, and is driven by a pilot hydraulic pressure to open and close the retard check valve bypass passage; and a drain switch valve that supplies and drains the pilot hydraulic pressure relative to at least one of the advance drain control valve and the retard drain control valve, wherein the phase control valve and the drain switch valve are integrated together as a complex valve and are driven by a common actuator.