Abstract: An engine including an assembly of at least two cylinders with different displacements and two crankshafts coupled at the same rotational speed via a gear train and a variably timed transmission having three concentric shafts separable from the drive assembly and designed to reduce the compression ratio as the intake pressure increases. The maximum and minimum compression ratios are set within the angular displacement limits between the two cylinders, and between said two cylinders and the clearance space, so that (a) the start of the variably time transmission stroke increases the translation of the piston by units of angular displacement between the two crankshafts at the end of compression phase, and (b) the end of the variably time transmission stroke combines combustion gas expansion on the piston at least from the maximum torque on the crank of the short-stroke crankshaft.

Abstract: The engine is characterized by an axial group of two cylinders (2, 7) communicating by means of a channel (22) situated in the cylinder head (20). Both cylinders (2, 7) joined side to side allow for a centralization of both crankshafts (4, 13) in the cylinder case (5). Each cylinder comprises a corresponding piston (1, 6) displaceable in the first cylinder (2) intended for the intake, compression, expansion and exhaust phases, said first piston (1) depending, via a piston rod (3), from the first crankshaft (4) situated in the cylinder case (5). The second piston (6) displaceable within the second cylinder (7) delimiting the combustion prechamber (8) wherein are housed a heating plug and a fuel injector, said second piston (6) depending, via a piston rod (12), from the second crankshaft (13) also located in cylinder case (5).

Abstract: Internal combustion engine comprising at least one cylinder (10), one piston (2) mounted to the crankshaft (2'), and at least one inlet valve and one exhaust valve. At the end of the cylinder (1) corresponding to the top dead center of the piston (2) are arranged on one hand a second cylinder (3) and a second piston (6) which are integral parts of the cylinder (1) and on the other hand a third cylinder (4) and a third piston (7) wherein injection means (8) and ignition means (9) are provided, the cylinder (4) communicating by a conduit (5) with the cylinders (1) and (3). The coupler means (11) provide for the drive of a small crankshaft (13). The control (10) enables via the coupler (11) a rotation angle shift up to 180.degree. between the shaft of the crankshaft (2') of the cylinder (1) and the shaft of the small crankshaft (13 ), the latter having two throws (14) and (14') offset by 180.degree. and actuating the pistons (6) and (7).