Composite Bonded Magnets With Self-Recoverability for Miniaturized Anisotropic Magnet Rotor

Abstract

In the preparation of a miniaturized rotor, a composite bonded magnet was fabricated by taking advantage of self-recoverability. A preformed magnet was synthesized by using incomplete three-dimensional network molecular structure which was formed under the optimum conditions at a temperature of 433 K, an alignment field of 1.4 MA/m, and a low compacting pressure of 50 MPa, respectively. The preformed ones were extruded and compressed into a ring-shaped magnet by using the self-recoverability at a pressure of 200 MPa and a temperature of 423 K under non-alignment-field. Through the process, a composite bonded magnet rotor in the shape of a ring could be prepared without a bonding layer. It was clarified that a 4 pole/6 slot DC brush less motor can be obtained by using the ring-shaped rotor comprising a parallel oriented anisotropic magnet with 7 mm in outer diameter, 158 kJ m 3 in (BH) max , and 6.2 Mg m 3 in density, respectively. Resultantly, the developed rotor enabled us to increase the S-T gradient by 1.75 times compared with that for a conventional isotropic Nd-Fe-B bonded magnet rotor with the same dimensions.Index Terms-Anisotropic bonded magnet rotor, anisotropic rare earth bonded magnet, DC brushless motor, self-recoverable binder system.