Piston control mechanism of reciprocating internal combustion engine of variable compression ratio type

A piston control mechanism of an internal combustion engine, said engine including a piston slidably disposed in a piston cylinder and a crankshaft converting a reciprocation movement of said piston to a rotation movement, said piston control mechanism comprising:

• a lower link rotatably disposed on a crank pin of said crankshaft;
• an upper link having one end pivotally connected to said lower link and the other end pivotally connected to said piston;
• a control link having one end pivotally connected to said lower link;
• and
• a position changing mechanism including a control crankshaft which extends in parallel with said crankshaft and rotates about a given axis, said control crankshaft including a main shaft portion which is rotatable about said given axis and an eccentric pin which is radially raised from said main shaft portion, said eccentric pin being received in a cylindrical bearing bore formed in the other end of said control link,
• wherein when said piston comes up to a top dead center, a rotation direction of an upper link center line relative to a first direction line is equal to a rotation direction of a control link center line relative to a second direction line, said upper link center line being an imaginary line which perpendicularly crosses both a first pivot axis between said piston and said upper link and a second pivot axis between said upper link and said lower link, said control link center line being an imaginary line which perpendicularly crosses both a third pivot axis between said lower link and said control link and said supporting axis, said first direction line being an imaginary line which perpendicularly crosses both said second pivot axis and a center axis of said crank pin, and said second direction line being an imaginary line which perpendicularly crosses both said third pivot axis and said center axis of said crank pin.