Axial Flux Cycloidal Magnetic Gears

The radial flux cycloid permanent magnet gear is characterized by a high gear ratio and a high torque density due to the use of one air gap. There are at least three disadvantages of this gear: 1) eccentric motion of the output rotor must be transferred to concentric shaft rotation; 2) the bearing loads are very large due to the offset rotor rotation; and 3) parasitic counterweights are required to suppress vibration associated with the eccentric rotation. The axial flux cycloidal gear solves the first disadvantage and partially the second. In this embodiment, a disk of magnets is sandwiched between the two fixed disks. That disk is allowed to spin freely on its own axis, but is moved eccentrically around the axis of the stator disks. The result is similar to the function of a radial flux cycloid, but with the elimination of the large bearing loads registered on the radial cycloid rotor. This paper describes the operation and construction of this unusual gear along with calculations for output load performance. The cogging torque for this device is essentially zero. A magnetic coupling technique is also presented for transferring the eccentric output torque to the stationary lab frame.