Rotation detecting device and bearing with rotation detecting device

摘要

A rotation detecting device, which is simple in structure and capable of detecting the absolute angle accurately with a high resolution, includes a plurality of ring-shaped magnetic encoders provided concentrically with each other and having different numbers of magnetic poles, each of the magnetic encoders having a magnetization row pattern with magnetic poles arranged circumferentially thereof; a plurality of magnetic sensors each operable to detect a magnetic field emanating from the corresponding magnetic encoder; and an angle calculating unit for determining an absolute angle of the magnetic encoders based on magnetic field signals detected by the magnetic sensors; in which the magnetic encoders are fitted to at least one core metal that is formed integrally with a projection portion protruding towards an encoder support surface side, on which the magnetic encoders are mounted, the projection portion being situated between the neighboring magnetic encoders.