Patent ID: 7514837
Filing Date: 2009-04-07
Classification: H02K

Abstract:
1. A brushless alternator comprising: a rotor mounted on a shaft; a ring-shaped yoke which is fixed to an inner surface of a bracket supporting the shaft rotatably, and which is opposed to the rotor via a very narrow radial clearance; a stepped portion provided on a side surface of an inner circumference of an axial end section of the yoke; a plate fixed to the stepped portion and having a cylindrical portion made of a magnetic material; a bobbin provided so as to surround a radially outer side of the cylindrical portion of the plate for the purpose of winding a field coil therearound; and a stator provided with a clearance retained on an outer side of the rotor, to which stator a magnetic flux generated by the field coil is propagated, wherein a radial thickness of a part of the cylindrical portion of the plate which is fixed to the stepped portion provided on the inner circumferential surface of the yoke is set larger than 1 mm and not larger than 2 mm.