Patent ID: 8272355

Claim:
A variable compression ratio apparatus for an engine receiving a combustion force of an air-fuel mixture from a piston so as to rotate a crankshaft, the apparatus comprising: cylinder blocks between which the crankshaft is movably disposed, the cylinder blocks being configured and dimensioned to change a position of a rotation center of the crankshaft such that the compression ratio of the air-fuel mixture is changed by the position of the rotation center of the crankshaft according to a driving condition of the engine; a guide hole formed through bodies of the cylinder blocks and slidably receiving the crankshaft therein so as to allow upward and downward movements of the crankshaft to change the rotation center of the crankshaft; an operating cylinder formed through a body of one of the cylinder blocks and connected to the guide hole and receiving hydraulic pressure according to driving condition of the engine; and an operating piston slidably mounted in the operating cylinder and engaged with the camshaft to selectively press a portion of the crankshaft to change the rotation center of the crankshaft by the hydraulic pressure.