Four-phase hybrid type stepping motor

Claim 1

A four-phase hybrid type stepping motor comprising a rotor, eight stator poles are formed on a plane facing to an outer side surface of said rotor with a plurality of stator teeth arranged with a common pitch τ s , opposing ones of said stator poles being paired and being separated from each other by 180°, and a plurality of windings wound in heteropolar on the four pairs of said stator poles, wherein a pitch between a center of said stator teeth of a first one (1 1 ) of said stator poles and a center of said stator teeth of a fourth one (1 4 ) of said stator poles, a pitch between said center of said stator teeth of said fourth stator pole and a center of said stator teeth of a seventh one (1 7 ) of said stator poles and a pitch between said center of said teeth of said seventh stator pole and a center of said stator teeth of a second one (1 2 ) of said stator poles are common and equal to τ c , said pitches τ s and τ c being set so that they satisfy the following equations: ##EQU4## where τ R is a pitch of teeth of said rotor, Z R is the number of the teeth of said rotor and N is an integer close to 3·Z R /8.