Permanent magnet rotor for electrical machines - esp. bicycle dynamo, using ferrite magnet which is either sintered or bonded with polymer, and is joined to stub axle

摘要

A multiple ring magnet which can be magnetised laterally is made with a counterbore at one or both ends. A hub is fixed in the counterbore and is used to hold a stub axle. The hub(s) and the stub axle(s) are pref. made of a metal; and an adhesive is pref. used to hold the hub(s) in the counterbore(s). The hubs are pref. joined to the stub axles by welding. The rotor is pref. made by mixing a ceramic magnet powder with a polymer and then using injection or pressure moulding to make a magnet from the mixt. During moulding, a magnetic field is used to make an anisotropic magnet. Alternatively, the ceramic magnet powder may be mixed with a binder and moulded into a ring which is then sintered. The rotor is lighter and stronger than similar conventional rotors but has comparable magnetic properties.