Three-phase permanent magnet cascade claw type stepping motor

Abstract

A magnet type stepping motor which has (1) a stator with three-phase stator windings, and 6 m pieces of stator main pole arranged side by side, where m is an integer and ≧1, the stator windings of one phase are wound around every two stator main poles among the 6 m pieces of the stator main pole, wherein when the stator windings of one phase are excited with a direct current, m pieces of N pole and M pieces of S pole are formed alternately on the 6 m pieces of stator main pole, and (2) a rotor of a cylindrical permanent magnet magnetized in the circumferential direction to form Z/2 pieces of N pole and Z/2 pieces of S pole alternately, where Z is the number of rotor poles.

What is claimed is:  
     
       1. A three-phase permanent magnet cascade claw type stepping motor comprising 
       (1) a rotor consisting of a cylindrical magnet magnetized in a circumferential direction thereof so as to form M pieces of N pole and M pieces of S pole respectively, where M is an integer and is ≧2, and  
       (2) a stator having annular three stator units spread in an axial direction of the rotor concentrically with a rotor axis, each of said stator units consisting of (a) two opposite stator cores having claw poles extending axially on the inner peripheral surface thereof, and b) a respective one of three stator windings of U, V and W phases held between said two stator cores, said windings of U, V and W phases being arranged sequentially in an axial direction of said stator, the claw poles of each stator winding being separated from one another by 180°/M and are magnetized in opposite polarities, said three stator windings being connected to form a star or delta connection so that adjacent claw poles magnetized by the stator windings of U phase and V phase are deviated by 60°/M from each other in a circumferential direction of the stator and are magnetized in opposite polarities  the same polarity, and so that adjacent claw poles magnetized by the stator windings of V phase and W phase are deviated by 60°/M from each other in the circumferential direction of said stator and are magnetized in opposite polarities  the same polarity.  
     
     
       2. The three-phase permanent magnet cascade claw type stepping motor as claimed in  claim 1 , wherein, each of said annular stator windings has a center tap, and wherein said annular stator windings are excited by a unipolar circuit having no more than six transistors so that a magnetic flux generated by the excited annular stator windings of one phase in the axial direction always becomes opposite to that generated by the excited annular stator windings of the other phase in the case of two phase exciting driving.