Patent ID: 8726864

Claim:
An engine that actively varies a compress expansion ratio, comprising: an intake camshaft to which an intake cam is formed to lift an intake valve; an exhaust camshaft to which an exhaust cam is formed to lift an exhaust valve; an intake valve variable timing unit that is disposed at one end portion of the intake camshaft to advance or retard a rotation of the intake camshaft; an exhaust valve variable timing unit that is disposed at one end portion of the exhaust camshaft to advance or retard a rotation of the exhaust camshaft; an intake valve variable duration unit that is disposed at the other end portion of the intake camshaft to vary a lift duration of the intake camshaft; and an exhaust valve variable duration unit that is disposed at the other end portion of the exhaust camshaft to vary a lift duration of the exhaust camshaft; wherein the intake camshaft includes an intake outer pipe to which the intake valve variable timing unit is engaged, wherein a rotation position of the intake outer pipe is advanced or retarded by the intake valve variable timing unit and wherein an intake outer cam is formed on an exterior circumference of the intake outer pipe, and an intake inner pipe to which the intake valve variable duration unit is engaged, wherein a rotation position of the intake inner pipe is advanced or retarded by the intake valve variable duration unit and wherein an intake inner cam is formed on an exterior circumference of the intake inner pipe; and wherein the intake inner pipe is slidably inserted into the intake outer pipe.