US 7,321,177 B2
Synchronous electric motor
Hiroyuki Uchida, Yamanashi (Japan); Tomonaga Yamamoto, Fujiyoshida (Japan); Takuya Maeda, Yamanashi (Japan); and Hiroshi Kougami, Yamanashi (Japan)
Assigned to Fanuc Ltd, Yamanashi (Japan)
Filed on Jun. 24, 2005, as Appl. No. 11/165,403.
Claims priority of application No. 2004-186638 (JP), filed on Jun. 24, 2004.
Prior Publication US 2006/0017345 A1, Jan. 26, 2006
Int. Cl. H02K 1/14 (2006.01); H02K 1/27 (2006.01); H02K 21/14 (2006.01); H02K 21/16 (2006.01)
U.S. Cl. 310—216  [310/156.07; 310/156.46; 310/156.49; 310/156.53] 9 Claims
OG exemplary drawing
 
1. A synchronous electric motor comprising:
a rotor having a rotation axis; and
a stator surrounding said rotor through a gap;
wherein said rotor includes a rotor core having an outer circumferential surface extending about said rotation axis and a plurality of permanent magnets attached to said rotor core to form plural poles along said outer circumferential surface of said rotor core;
wherein said outer circumferential surface of said rotor core is provided, at each of said plural poles, with a contour deviating from a circular arc and bulging out in a radial outward direction, as seen in a cross-section perpendicular to said rotation axis;
wherein said plurality of permanent magnets include a plurality of magnet sets individually assigned to said plural poles, each set including two or more permanent magnets; and
wherein said gap between said rotor and said stator changes in dimension thereof along a circumferential direction of said outer circumferential surface of said rotor core; and wherein a maximum dimension of said gap Gmax, a minimum dimension of said gap Gmin and a thickness H of each of said plurality of permanent magnets have a relationship meeting a formula of Gmax/(Gmax+H)≧√2×Gmin/(G+H).