Method for realising a permanent-magnet rotor for a synchronous motor

A method for obtaining a permanent-magnet rotor, for a synchronous motor, particularly for a pump of a washing machine for industrial and domestic use and the like, with external stator, comprising a cylindrical central core, with axis X-X and having an axial passage extending along said axis X-X, surrounded by a plurality of permanent magnets having an extrados and an intrados and side edges, wherein the method comprises the following steps:

• arranging a cup-like body, in a plastic material, comprising a base end, an open end, and a side wall and having a plurality of longitudinal grooves formed on an outer side of the side wall and extending from the base end to the open end, a plurality of longitudinal bulges corresponding to said longitudinal grooves on an inner side of the side wall, and a plurality of positioning seats for a positioning of the magnets, said positioning seats being defined between one longitudinal bulge and the next along the inner side of the side wall;
• inserting the central core into the cup-like body and inserting the magnets in the positioning seats between the central core and the inner side of the side wall of the cup-like body;
• inserting the cup-like body into a mould;
• after inserting the cup-like body into the mould, injecting a plastic material into the mould in order to obtain a cage-like structure, said plastic material filling at least:
• a volume of the mould located above and below the opposite ends of the cup-like body forming opposite bottoms of the cage-like structure;
• a volume between the longitudinal grooves of the cup-like body and an internal wall of said mould forming longitudinal columns connecting said opposite bottoms.