Variable compression ratio device of internal combustion engine

A variable compression ratio device adapted to be used with an internal combustion engine, comprising:

• a piston including a piston inner part operatively 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;
• a cam mechanism operatively connected between the piston inner part and the piston outer part for alternately moving the piston outer part to the low compression ratio position L and the high compression ratio position H;
• and
• an actuator operatively provided adjacent to the piston inner part for operating the cam mechanism;
• the cam mechanism including a lift member supported by the piston inner part and moved by the actuator alternately to a lift release position A and a lift position B, a plurality of first cam top portions projectingly provided integrally on a top surface of the lift member and a plurality of second cam top portions projectingly provided on an undersurface of a head part of the piston outer part;
• in the lift release position A of the lift member, the first cam top portions and the second cam top portions mesh with each other to move the piston outer part to the low compression ratio position, and
• in the lift position B of the lift member, the first cam top portions and the second cam top portions cause their top surfaces to abut on each other to move the piston outer part to the high compression ratio position H;
• wherein a skirt part is slidably guided by an inner peripheral surface of a cylinder bore of an engine E that is integrally formed at the piston inner part, and a peripheral wall of the piston outer part, to which piston rings are fitted, is terminated directly above the skirt part.