Link type variable stroke engine

A link type variable stroke engine in which,

• in a crankcase of an engine main body,
• a crankshaft is rotatably supported, and
• a rotary shaft is rotatably supported so that power is transmitted at a speed reduction ratio of 1/2 from the crankshaft, the rotary shaft having an axis parallel with the crankshaft and being provided with an eccentric shaft at an eccentric position, and
• a piston, slidably fitted to a cylinder block of the engine main body, the crankshaft and the eccentric shaft are linked by a linking mechanism, the linking mechanism including:
• a main connecting rod coupled, at one end, with the piston by using a piston pin;
• a sub connecting rod rotatably coupled with a crank pin of the crankshaft and rotatably coupled with the other end of the main connecting rod by using a connecting rod pin;
• and a swing rod rotatably coupled, at one end, with the sub connecting rod by using a swing pin at a position displaced from a position coupled with the main connecting rod and rotatably coupled, at the other end, with the eccentric shaft,
• wherein a counterweight part is provided so that in a projection view on a plane orthogonal to the axis of the rotary shaft, a center of gravity of the counterweight part is located on an opposite side of the axis of the rotary shaft from an axis of the eccentric shaft, and rotates together with the rotary shaft.