Patent ID: 9685851
Date: 2017-06-20
CPC Classifications: H02K

Claim:
1. A magnetic drive system comprising three members, a first and second of which form a higher speed rotor and a lower speed rotor, respectively, each arranged to rotate about a common axis relative to a third member, wherein the first and second members have respective sets of permanent magnets, the first and second members having different numbers of magnetic poles, and the third member comprises: a cylindrical body having a plurality of pole pieces embedded therein, the pole pieces each including a main portion and a retaining portion, each of the main portion and the retaining portion having radially inner and outer surfaces, wherein the cylindrical body defines a first radial thickness that is measured along a first line that extends perpendicular to the common axis through the retaining portion, the first radial thickness measured in a single radial direction from the common axis and the first radial thickness being a thickness of the pole piece along the first line subtracted from a thickness of the cylindrical body along the first line, the first radial thickness being greater than a second radial thickness measured along a second line that extends parallel to the first line and perpendicular to the common axis through the main portion, the second radial thickness measured in a single radial direction from the common axis and the second radial thickness being a thickness of the pole piece along the second line subtracted from a thickness of the cylindrical body along the second line, the pole pieces being arranged to modulate the magnetic field acting between the magnets, and a support connected to the pole pieces, wherein the retaining portion of at least one of the pole pieces is completely enclosed within the cylindrical body, wherein the cylindrical body has a number of pole pieces that is equal to the sum of the number of pole-pairs of the first member and the number of pole-pairs of the second member and wherein the pole pieces consist essentially of ferromagnetic material.