Abstract: A four-stroke internal combustion engine including variable compression ratio comprises a crankcase including a crankshaft having a crankpin and being supported by the crankcase and rotatable with respect thereto about a crankshaft axis, a connecting rod including a big end and a small end, a crank member being rotatably mounted on the crankpin, and comprising at least a bearing portion which is eccentrically disposed with respect to the crankpin, a crank member drive system for rotating the crank member at a rotation frequency with respect to the crankcase which is half of that of the crankshaft, and a control system for operating the engine with repetitive cycles, wherein the compression ratio in the compression stroke is changed. The control system is configured to interrupt the repetitive cycles by rotating the crankshaft an additional single revolution between two successive combustion strokes for switching between a high and low compression ratio.

Abstract: A reciprocating piston mechanism comprises a crankcase and a crankshaft (rotatable about a crankshaft axis) which has at least a crankpin having a crankpin. A connecting rod includes a big end rotatably mounted on the crankpin and a small end rotatably connected to a piston. The crank member is provided with a crank member gear that meshes with an intermediate gear, both gears of which are external gears along with first and second auxiliary gears. The intermediate gear meshes with the first auxiliary gear. The first auxiliary gear is fixed to the second auxiliary gear via a common auxiliary shaft that mounts to the crankshaft and rotates with respect thereto about an auxiliary shaft axis that extends parallel to the crankshaft axis. The second auxiliary gear meshes with a central gear. The central gear is an internal gear, which has a center line that coincides with the crankshaft axis.

Abstract: A crank-connecting rod mechanism for an internal combustion engine or the like comprising a shaft rotating around its axis, a first crank fixed to the shaft and a crank pin fixed to the first crank. A crank pin extends parallel to but at a first radial distance from the shaft. A second crank rotatably mounted onto the first crank pin is fixed to a second crank pin having an axis at a second radial distance from the axis of the first crank pin. A connecting rod is rotatably mounted on the second crank pin. Rotary means are provided to force the second crank to rotate relative to the first crank upon a rotation of the shaft.