Patent ID: 6684828
Filing Date: 2004-02-03
Classification: F02B

Abstract:
A variable compression ratio mechanism for a reciprocating internal combustion engine employing a reciprocating piston movable 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, comprising:an upper link connected at its one end to the piston pin; a lower link connected to the other end of the upper link via a first connecting pin and rotatably installed on the crankpin; a control link connected at its one end to the lower link via a second connecting pin, and pivotably connected at the other end to a body of the engine to permit oscillating motion of the control link on the body of the engine; a control mechanism shifting a center of oscillating motion of the control link to vary a compression ratio of the engine; and the lower link comprising: a crankpin bearing portion into which the crankpin is fitted; a first connecting-pin bearing portion, which is parallel to the crankpin bearing portion and into which the first connecting pin is fitted; a second connecting-pin bearing portion, which is parallel to the crankpin bearing portion and into which the second connecting pin is fitted; a central connecting portion having an axial length shorter than each of an axial length of the crankpin bearing portion, an axial length of the first connecting-pin bearing portion, and an axial length of the second connecting-pin bearing portion; and the central connecting portion that connects an axial central portion of at least one of the first and second connecting-pin bearing portions to an axial central portion of the crankpin bearing portion.