US Patent 7847457 BLDC motor assembly

A BLDC electric motor assembly (24) includes a rotor (42) having a plurality of magnet segments (50) securely retained thereabout by an annular ring (68) which is shrunk in situ in an electromagnetic forming operation. The magnet segments (50) are formed with tongues (62, 64) on their upper and lower ends (56, 58). One tongue (64) seats in a retaining pocket (48) molded on the rotor shaft (40), whereas the other tongue (62) provides a ledge into which the ring (68) seats. After the magnet forming operation, wherein the ring (68) is shrunk, the outer surface of the ring (68) is flush with the outer surfaces (54) of the magnet segments (50).