Abstract: The publication relates to a power converter according to the principle of the hot-air engine (Stirling engine), comprising a cylinder containing a main piston (4) and a displacement piston (3), each of which can be moved forward and backward on the axis of the cylinder and each of which possesses a piston rod assembly (20, 25) which is connected via connecting rods (17, 21) with a link system (21-24 or 17-19 resp.) to two parallel cranks (9) which rotate synchronously in opposite directions so that the displacement piston is moved phase-shifted to the main piston. The link system (21-24) of the main piston (4) comprises a frame element (24) which is rigidly connected to the latter's piston rod assembly (25) and has at least four journals (22,23) which are arranged symmetrically to the cylinder axis in a common plane perpendicular to the cylinder axis and which are oriented parallel to the crank shafts (9) and to each of which is linked a connecting rod (21).