Patent ID: 6491003
Filing Date: 2002-12-10
Classification: F02B

Abstract:
A variable compression ratio mechanism for a reciprocating internal combustion engine including a piston moveable through a stroke in the engine and having a piston pin and a crankshaft changing reciprocating motion of the piston into rotating motion and having a crankpin, the variable compression ratio mechanism comprising:a plurality of links mechanically linking the piston pin to the crankpin; a control shaft extending parallel to an axis of the crankshaft; an eccentric cam attached to the control shaft so that a center of the eccentric cam is eccentric to a center of the control shaft; a control link connected at a first end to one of the plurality of links and connected at a second end to the eccentric cam; an actuator that drives the control shaft within a predetermined controlled angular range and holds the control shaft at a desired angular position so that a compression ratio of the engine continuously reduces by driving the control shaft in a first rotational direction when at least one of engine speed and engine load changes from a first value to a second value higher than the first value and so that the compression ratio continuously increases by driving the control shaft in a second rotational direction opposite to the first rotational direction when the at least one of engine speed and engine load changes from the second value to the first value; and a distance from the center of the control shaft to a centerline of the control link passing through both connecting points of the first and second ends, measured with the piston near top dead center, being dimensioned so that the distance continuously decreases as the compression ratio decreases.