US Patent 7311071 Variable valve timing control apparatus of internal combustion engine

A variable valve timing control apparatus of an internal combustion engine includes a drive rotary member, a driven rotary member, and a phase-change mechanism disposed between the drive and driven rotary members. The phase-change mechanism changes a relative phase between the drive and driven rotary members by an operating force, and returns the relative phase to an engine start-up phase suitable for the engine start-up at the engine starting. The phase-change mechanism has a phase-change characteristic that a phase-change rate reduces near the engine start-up phase when the relative phase is returned to the engine start-up phase.