| 摘要 |
A valve operating system of an internal combustion engine enabling both valve working angle and phase to be varied, includes a variable working angle control mechanism being responsive to a supply pressure of working fluid to adjust a working angle of an intake valve, and a variable phase control mechanism being responsive to a supply pressure of working fluid to adjust a phase of the working angle of the intake valve. A control unit controls the supply pressure to each of the control mechanisms depending on engine operating conditions. In a cold-engine state that the temperature of working fluid is below a predetermined temperature, an intake valve open timing is retarded in comparison with a predetermined stability-limit valve open timing, by limiting a controlled variable of at least one of the control mechanisms.
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