US Patent 7434553 Variable valve mechanism for engine

In a variable valve mechanism, a control shaft is associated with an advance oil passage such that the same passage is closed by the control shaft when a maximum valve lift amount of an intake valve is equal to or larger than a reference lift amount. The control shaft is associated with the advance oil passage such that a range in which the control shaft displaces is limited to a range between a minimum value of the maximum valve lift amount and a lift amount just before the reference lift amount when an advance angle of the intake valve is equal to or larger than a reference advance angle.