Brushless direct current motor

Claim 1

A brushless d.c. motor having a stator and a rotor; said stator comprising a stator core with a plurality of magnetic pole pieces disposed circumferencially and separated by slots, stator windings wound around said magnetic pole pieces, a pattern conductor for frequency generation mounted on said stator core, and a drive circuit connectable to a power source for controlling an exciting current to said stator windings in response to a speed control signal from said pattern conductor; and said rotor comprising a yoke rotatably mounted on said stator, a plurality of permanent magnets mounted on said yoke and having magnetic pole faces in opposition to magnetic pole faces of said magnetic pole pieces of said stator core, and a permanent magnet for frequency generation mounted on said yoke and in opposition to said pattern conductor; the arrangement being such that said magnetic pieces each have a first portion extending in a radially outward direction, second portions extending from a radially outer end of said first portion in opposite circumferential directions to separate from each other, and third portions extending from tips of said second portions in radially outward direction; and that said stator windings comprise first windings wound on said first portion and serially connected to each other for each of said magnetic poles, and second windings wound on one of said third portions of said magnetic pole and the adjacent third portion of the contiguous magnetic pole and serially connected to each other, and the phase of said first windings is shifted relative to said second windings.