Patent ID: 7932656
Filing Date: 2011-04-26
Classification: F01D,F04D,F05D,F16C

Abstract:
1. A magnetic bearing device which comprises: a main shaft; a flange shaped thrust plate coaxially mounted on the main shaft so as to extend perpendicular to the main shaft and made of a ferromagnetic material; a rolling bearing unit for supporting a radial load and a magnetic bearing unit for supporting one or both of an axial load and a bearing preload; an electromagnet fitted to a spindle housing so as to confront the thrust plate, on a non-contact basis; a sensor for detecting an axial force acting on the main shaft; a controller for controlling the electromagnet in response to an output from the sensor; and a permanent magnet arranged within a yoke of the electromagnet on one side of the thrust plate, wherein a stiffness of a composite spring formed by the rolling bearing unit and a support system for the rolling bearing unit is higher than a negative stiffness of the electromagnet, wherein another electromagnet including no permanent magnet is arranged within the yoke on the other side of the thrust plate so as to confront the electromagnet on the one side, and wherein in a light load region of the axial load, both of the electromagnets concurrently operate.