US Patent 7793629 Valve timing control system

A valve enables and disables communication of a bypass passage, which extends from a fluid supply passage and bypasses at least one fluid control valve, to at least one of a retarding passage and an advancing passage connected to a valve timing mechanism. An ECU controls the valve to enable the communication of the bypass passage to the at least one of the retarding passage and the advancing passage when a temperature is equal to or less than a predetermined temperature. The ECU controls the valve to disable the communication of the bypass passage to the at least one of the retarding passage and the advancing passage when the temperature is higher than the predetermined temperature.