Patent ID: 6710493
Filing Date: 2004-03-23
Classification: H02K

Abstract:
A dynamo-electric machine comprising: a yoke; a rotor, which is rotatably received in the yoke and includes a predetermined number of cores circumferentially arranged at substantially equal angular intervals, wherein each core includes a tooth, which radially outwardly extends toward the yoke; and a plurality of curved magnets, which are secured to an inner circumferential surface of the yoke, wherein: each magnet has first and second tapered portions, which are tapered in opposite circumferential directions, wherein each of the first and second tapered portions has axially opposed first and second tapered surface of each of the first and second tapered portions decreases toward an outer circumferential end of each of the first and second tapered portions, wherein the first tapered surface of each of the first and second tapered portions has a first opposing point, which is radially opposed to a first imaginary end circle defined by outer peripheral surfaces of the cores at one axial ends of the cores, and the second tapered surface of each of the first and second tapered portions has a second opposing point, which is radially opposed to a second imaginary end circle defined by the outer peripheral surfaces of the cores at the other axial ends of the cores; and the rotor and each magnet are configured to satisfy one of the following conditions:(D&pgr;/Z)Ã—n+T(D&pgr;/Z)Ã—(nâˆ’1)+Twherein Z is a number of the cores of the rotor, D is an outer diameter of the rotor, T is circumferential dimension of each tooth, X is a circumferential dimension between a circumferentially innermost one of the first and second opposing points of the first tapered portion and a circumferentially innermost one of the first and second opposing points of the second tapered portion when each magnet is viewed from a radial direction, and n is the number of the teeth that are entirely placed within a range defined by X when a circumferential center of one of the teeth is radially oposed to a circumferential center of the range defined by X, wherein more than one minimum point of cogging torque occurs per 2&pgr;/Z rotation of the rotor.