Patent ID: 8405269

Claim:
A rotor for an electric motor with permanent magnets, said rotor having a principal axis (D), the rotor comprising: a laminated core delimited by a first and a second end wall and by a lateral surface and having a hole for coupling to a motor shaft and a plurality of longitudinal slots for housing the magnets; guide ribs in each of the slots for guiding the magnets in the slots; and a flexural spring positioned between each magnet and the respective slot for stabilizing the magnets in the slots, wherein: the core has a groove for each flexural spring, the groove extends in a direction parallel to the principal axis (D) between the first and second end walls, each spring is inserted lengthways in the groove, and each groove is located at the midpoint of the respective slot, perpendicular to the respective slot; wherein each slot has two end portions, one each on opposite ends of the slot, each end portion extending outward from the slot beyond one of the guide ribs; wherein the lateral surface includes a plurality of straight portions, with each straight portion positioned radially outwardly of adjacent end portions of adjacent slots; wherein radially inner edges and radially outer edges of adjacent end portions of adjacent slots, respectively, extend directly toward each other, and both the radially inner edges and the radially outer edges of the adjacent end portions are parallel to each other and also parallel to an adjacent straight portion of the lateral surface; the laminated core further comprising a plurality of rectangular bonding elements for joining together laminations of the laminated core, each rectangular bonding element positioned radially inwardly of a pair of adjacent end portions and having radially inner and outer edges being parallel to the radially inner and outer edges of the adjacent end portions; wherein the lateral surface is defined by a plurality of connected arcs each positioned at one of the longitudinal slots, the arcs having respective mid-points located at an equal distance (R 1 ) from the principal axis (D) and centers positioned substantially at an internal edge of the hole.