Permanent magnet rotor

Abstract

A permanent magnet rotor for a brushless electric motor of the kind with an internal stator, has a carrier structure of molded plastic that includes a disc portion fixed to a shaft. The disc portion has a periphery joined to a substantially cylindrical cage portion coaxial with the shaft. The cage portion accommodates a magnetic flux conducting structure forming an wall which is coaxial with the shaft, and a plurality of permanent magnets shaped as ring segments, disposed at angular intervals within and adjacent to the flux conducting structure. Each magnet has its circumferentially terminal faces parallel with each other or converging in the outward direction. The cage portion is overmolded onto the flux conducting structure and has a plurality of angularly spaced struts which are essentially parallel to the axis of the rotor and which protrude radially inwards. Each of the struts having on its flanks respective containment surfaces which are essentially parallel to, or converge in the outward direction with, corresponding facing surfaces of the adjacent struts, such that between the magnetic flux conducting structure and each pair of adjacent struts there is defined a respective seat adapted to snugly receive a respective permanent magnet.