Patent ID: 7574986

Claim:
A variable compression ratio device of an internal combustion engine, comprising: a piston including a piston inner part connected to a connecting rod via a piston pin, and a piston outer part which is fitted on an outer periphery of the piston inner part so as to be only slidable in an axial direction and which is movable between a low compression ratio position L near the piston inner part and a high compression ratio position H near a combustion chamber, with an outer end surface of the piston outer part facing the combustion chamber, the piston inner part being provided with a piston outer part holding device that selectively holds the piston outer part in the low compression ratio position L and the high compression ratio position H, wherein long holes with longer diameters directed in an axial direction of the piston are provided in the piston outer part to face opposite ends of the piston pin; and a shaft portion connected to the opposite ends of the piston pin is slidably fitted in the long holes to allow an axial relative movement between the piston inner part and the piston outer part while preventing relative rotation between the piston inner part and the piston outer part.