Linear generator or motor with integral magnetic spring

摘要

The invention relates to thermomechanical transducers drivingly linked to a linear motor or alternator, preferably a free piston Stirling engine in which the piston is drivingly linked to the field magnet of an alternator. There are symmetric and coaxial secondary magnets attached at opposite ends of the field magnet. The field magnet is polarized radially in one direction and the secondary magnets are polarized radially in the opposite direction. When the field magnet is displaced from a centered position, the secondary magnets have an oppositely directed axial net force exerted upon them. This causes a centering bias on the field magnet and therefore a centering of the piston in the Stirling engine or cooler. A secondary effect produced by the magnetic spring of the secondary magnets is amplitude limiting during load reduction on the Stirling engine. Amplitude limiting is a result of increased spring constant of the magnetic spring past a certain amplitude. This increased spring constant results in greater energy storage in the magnetic spring and decreased efficiency due to decreased phase angle.