Magnetically coupled rotary magnetic encoder with angle error reduction

摘要

A rotary magnetic encoder assembly of noncontact or “contactless” construction having an internally disposed first exciter or sensor magnet magnetically coupled to an externally disposed second application or drive magnet attached to an encoder shaft that rotates the sensor magnet substantially in unison therewith during encoder shaft rotation. The sensor magnet is rotatively supported by a friction reducer that is a bearing arrangement that provides point bearing contact preventing stiction and reducing dynamic friction of the sensor magnet minimizing angle error and helping to prevent “Quiver.” In one embodiment, the friction reducer is a spherical ball bearing. In another embodiment, the friction reducer is a thrust bearing that includes a spindle carrying the sensor magnet. A magnetic anchor can be disposed between the sensor magnet and drive magnet to help keep the sensor magnet in point bearing contact during rotation further minimizing angle error.