US Patent 7884521 Rotor shaft for a magnetic bearing device

A rotor shaft (200) for a magnetic bearing device (1) is disclosed. The shaft comprises an inner portion on whose periphery a plurality of targets (240, 260, 280) separated by spacers (250, 270) are mounted. This is achieved exerting an axial pressing force (F, F′) to the peripheral parts, rather than applying a radial press fit. In this manner, a simplified construction, a higher stiffness and a higher stability at high rotational speed are achieved. Further disclosed is a rotor having a thrust disk (220) whose diameter decreases towards the periphery. This allows to use a larger thrust disk at a given rotational speed.