Disk-type single-phase brushless motor

DETAILED DESCRIPTION What is claimed is: 1.
A disk-type single-phase brushless motor, comprising a rotor supported for rotation and including a field magnet having 2P alternate north and south poles of essentially equal circumferential pole width .
theta.
, P being an integer greater than 1, a coreless stator armature including a stator yoke provided stationarily in an opposing relationship to said rotor with an axial air gap left therebetween, a printed circuit board secured to one surface of said stator yoke, and at least one coreless armature coil disposed at the same-phase positions on a surface of said stator yoke or said printed circuit, a single position-detecting element provided on said coreless stator armature for detecting a position of said rotor, and a driving circuit provided on said printed circuit board for driving said coreless stator armature, said stator yoke having at least one cutaway portion formed therein for enabling self-starting of said disk-type single-phase brushless motor, said cutaway portion of said stator yoke being defined by a first radially extending edge formed on an imaginary line passing the center of said stator yoke at an angular position of said stator yoke spaced by an angular distance of about .
theta.
/2 in the direction opposite the direction of rotation of said rotor from an imaginary Y axis line which perpendicularly crosses an imaginary X axis line at the center of said stator yoke in a plane of said stator yoke to divide said stator yoke into four imaginary sections, and a second edge formed in another imaginary line which extends substantially in a parallel relationship to said imaginary X axis line from an inner radial end of said first edge to an outer circumferential periphery of said stator yoke such that said cutaway portion has an angular width of .
theta.
+.
alpha.
at the outer ends of said first and second edges of said cutaway portion of said stator yoke, .
alpha.
being an angle smaller than .
theta.
/2, said stator yoke being positioned relative to said coreless armature coil such that said first radially extending edge of said cutaway portion thereof is located at a position spaced by an angular distance of an angle between