Variable stroke engine

A variable stroke engine, comprising;

• a plurality of links connecting a piston with a crankshaft;
• a control member disposed on an engine main body so as to be moveable in two directions over a prescribed range relative to the engine main body;
• a control link connecting one of the plurality of links with the control member;
• and
• an actuator for displacing the control member;
• wherein the actuator comprises a hydraulic chamber separated into a first and second hydraulic chamber by a piston, a check valve having a first and second end, and a switching valve having three positions for selectively connecting the first and second chambers to the check valve, the three position including a first position connecting the first and second chambers with the first and second ends of the check valve, respectively, a second position connecting the first and second chambers with the second and first ends of the check valve, respectively, and a third position closing the first and second chambers, and
• wherein the first end is directly connected with the switching valve and the second end is directly connected with the switching valve such that the check valve is free of connection from an oil tank.