Permanent magnet rotor for electrical machines - esp. for bicycle dynamo, where reinforced polymer shaft is moulded into barium ferrite ring magnet

摘要

A multiple ring magnet is made which can be magnetised laterally; and the magnet is anchored on a shaft made of a polymer and moulded into the magnet. The shaft is pref. anchored in the bore of the magnet by profiled chamfers provided at each end of the magnet. The magnet is pref. made by mixing a ceramic magnet material with a binder, and then pressing and sintering the mixt. to make a ring magnet. The ceramic is esp. barium- or strontium-hexaferrite. The magnet is next placed in a die used for the injection or pressure moulding of a shaft made from a thermoplastic material reinforced with fibres, esp. polyethylene-terephthalate or polyamide reinforced with glass fibres. Provides simple mfr. of permanent magnet rotors at low cost, and with a low total wt.