JPS6014209B

1525489 Automatic control of position TELDIX GmbH and ARTHUR PFEIFFER VAKUUMTECHNIK WETZLAR GmbH 28 Nov 1975 [6 Dec 1974] 49088/75 Heading G3R [Also in Division F2] A rotor, stabilized in a radial direction by active and passive bearings, includes a bell shaped portion into which at least partially extends a subassembly of a rotor position sensor, a circuit for damping rotor radial oscillations and a stator of an electrial drive motor. As shown, for use in a turbo-molecular pump, an inductive sensor 42 detects the position or speed of rotor 5 and controls at least one electromagnetic winding 35 accordingly so as to damp radial rotor oscillations. The winding 35, which has an E or U shaped core, co-operates with a ferromagnetic ring 40 on the bell shaped portion 39 of the rotor, that also houses a rotor drive (e.g. brushless) motor. The output of sensor 42, which can be the same winding as control winding 35, is filtered before amplification so that only mechanical resonant frequencies are damped. The passive bearing 11 comprises a permanent magnet 12 and ferromagnetic parts 14, 15, 18 or alternatively parts 14, 15 may be omitted and ring 18 made from a permanent magnet. The active bearing 23 includes a ferromagnetic portion 30 on the rotor and an electromagnet 24 that regulates the rotor axial position as sensed by device 31, which may be inductive, capacitive or photo-electric. The subassembly cooperating with the bell shaped portion of the rotor makes the moment of inertia at the end of the rotor greater than this moment at the middle of the rotor.