Abstract: A device includes a driving or driven rotating shaft (AM) of axis (XX?), at least one piston (P1) which slides in a cylinder (C1) of axis (X1X1?) separate from the axis (XX?), an oscillating structure (SO) having a protuberance of axis (YY?) and being able to oscillate by a universal joint that prohibits its rotation about the axis (YY?), at least one link rod which transmits the forces between the piston and a point (CS?1, CS?2) on the oscillating structure such that when the piston (P1) moves, the axis (YY?) sweeps a cone of axis (XX?), a crankshaft (V) turning about the axis (XX?), articulated connection (F) between the oscillating structure (SO) and the crankshaft (V), an adjusting device which causes the connection means to pivot, resulting in a variation in the level of compression or cylinder capacity of the device.