Patent ID: 8087390

Claim:
A multi-link variable compression ratio engine comprising: a crankshaft; a piston operatively coupled to the crankshaft to move back and forth within a cylinder of the engine; a control shaft rotatably supported on the engine, the control shaft having an eccentric axle that is eccentric relative to a rotational center axis of the control shaft; a linkage operatively connecting the piston to the crankshaft and the crankshaft to the eccentric axle of the control shaft; a drive motor operatively coupled to the control shaft to rotate the control shaft about the rotational center axis such that a top dead center position of the piston is changed by turning the control shaft to vary a compression ratio of the engine by changing the position of the eccentric axle and the orientations of the linkage; and a reduction mechanism coupling the drive motor to the control shaft to reduce the rotation of the drive motor and transmit the rotation to the control shaft such that a reduction ratio of a rotation angle of the drive motor to a rotation angle of the control shaft is less at a high compression ratio than at an intermediate compression ratio.