To set the top dead center of suction and exhaust gases and the top dead center of a compression to the same, in an engine in which the stroke of a piston in an expansion stroke is set larger than that in a compression stroke.

The length L1 of a second arm 67, the length L2 of a first arm 66, the length L3 of a control rod 69, the length L4 of a connecting rod 64, a y-axis length L5 from the axis of a crankshaft to the axes of rotary shafts 81, 82, the x-axis length L6 from the axis of the crankshaft to the axes of the shafts 81, 82, the offset amount δ of the y-axis of the axis C of the cylinder from the axis of the crankshaft, an angle α formed between the first and second arms 66 and 67, the length R between the axis of the crankshaft and a crank pin 65, the length Rp of a straight line for connecting the axes of the shafts 81, 82 to the axis of a movable deviated axis 61, and an angle θp when the angle θ is '0' are set so that the top dead center of the suction and exhaust, and the top dead center of the compression coincide based on formula representing the height X of a piston pin 63.