US Patent No. 9,397,526

ELECTRIC MOTOR HAVING STRUCTURE FOR REDUCING COGGING TORQUE


Patent No. 9,397,526
Issue Date July 19, 2016
Title Electric Motor Having Structure For Reducing Cogging Torque
Inventorship Youichi Akasako, Yamanashi (JP)
Assignee Fanuc Corporation, Yamanashi (JP)

Claim of US Patent No. 9,397,526

1. A synchronous electric motor having s slots and 2p poles, wherein a lowest common multiple of s and p is an odd multiple
of p, the synchronous electric motor having a rotor comprising:
an iron core having a plurality of protrusions for positioning permanent magnets; and
a plurality of permanent magnets positioned on the iron core,
wherein the protrusions are arranged on the iron core so that one end of each permanent magnet is inclined towards one of
neighboring permanent magnets so as to be attracted to the one of the neighboring permanent magnets, and so that the other
end of each permanent magnet is inclined towards the other of neighboring permanent magnets so as to be attracted to the other
of the neighboring permanent magnets,

wherein each protrusion has a trapezoidal shape having a height in a direction of a rotation axis of the iron core,
wherein the iron core includes a first region and a second region defined by dividing the iron core into two halves in a direction
of a rotation axis thereof, and

wherein a first protrusion and a second protrusion are alternately positioned in a circumferential direction of the iron core,
the first protrusion having a long side positioned in the first re ion and a short side positioned in the second region, and
the second protrusion having a short side positioned in the first region and a long side positioned in the second region.