Evaluation of High-Speed Rotation Characteristics and a Proposal for Avoiding the Vibration Mode in Repulsive Type Magnetic Bearing Systems Using Permanent Magnets

摘要

This paper reports on the performance characteristics of the permanent magnet repulsion-type magnetic bearing, which has a vertical-shaft-type inner rotor with polygon scanner mirror facets. In general, though this type of magnetic bearing system has the feature that the radial stiffness is constant in the permanent magnet sections at a steady position, if the radial stiffness can be changed by an axial active control, various applications of this system can be expected. We propose the generation of a radial restoring force, using an iron board with a conical surface set up in the rotor shaft. Stable rotation at a maximum rotation speed of about 50000 rpm is achieved, and a change in the radial stiffness in the noncontact levitation condition is confirmed.