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US 6,204,584 B1Granted
Low cogging torque brushless motor rotor
AssigneeCleveland Motion Controls, Inc.
InventorJerzy Muszynski
Life of this patent
Estimating the term…
Abstract
A low cogging torque permanent magnet rotor is provided including a shaft and a permanent magnet mounted on the shaft. A gap is provided between the shaft and the magnet near a boundary between the magnet poles thereby reducing the cogging torque as the rotor poles rotate past the poles of the motor stator.
Claims33
A rotor for use in a low cogging torque brushless motor with an outlying stator, said rotor comprising:
- a shaft rotatable about a longitudinal axis having longitudinally spaced front and rear ends and a radially outer surface;
- a magnet having a radially inner surface engaging said outer surface of said shaft an outer surface radially outwardly of said inner surface, and at least two magnetic poles having different magnetic polarities circumferentially adjacent one another at a pole boundary;
- and
- said shaft and said magnet near said pole boundary having an air gap therebetween, said air gap including a contoured portion on said shaft.
1 more element
A rotor for use in a low cogging torque brushless motor with an outlying stator, said rotor comprising:
- a shaft rotatable about a longitudinal axis having longitudinally spaced front and rear ends and a radially outer surface;
- a magnet having a radially inner surface engaging said outer surface of said shaft, an outer surface radially outwardly of said inner surface, and at least two magnetic poles having different magnetic polarities circumferentially adjacent one another at a pole boundary;
- means for providing an air gap between said shaft and said magnet near said pole boundary;
- and,
- said air gap being circumferentially aligned with said pole boundary.
2 more elements
A rotor for use in a low cogging torque brushless motor with an outlying stator, said rotor comprising:
- a shaft rotatable about a longitudinal axis having longitudinally spaced front and rear ends and a radially outer surface;
- a magnet having a radially inner surface engaging said outer surface of said shaft, an outer surface radially outwardly of said inner surface, and at least two magnetic poles having different magnetic polarities circumferentially adjacent one another at a pole boundary;
- and
- means for providing a plurality of air gaps between said shaft and said magnet near said pole boundary.
1 more element
A rotor for use in an electric motor, and rotatable about a longitudinal axis, said rotor comprising:
- a magnet having radially spaced outwardly facing and inwardly facing surfaces, axially spaced first and second ends, and at least two magnetic poles of different magnetic polarities circumferentially adjacent one another at a pole boundary;
- and
- a shaft having an outer periphery including a first portion engaging said inwardly facing surface, and a second portion spaced inwardly from said first portion configured to define a circumferentially discontinuous and discrete air gap therebetween near said pole boundary.
A rotor for use in an electric motor, and rotatable about a longitudinal axis said rotor comprising:
- a magnet having radially spaced outwardly facing and inwardly facing surfaces, axially spaced first and second ends, and at least two magnetic poles of different magnetic polarities circumferentially adjacent one another at a pole boundary;
- a shaft having an outer periphery including a first portion engaging said inwardly facing surface, and a second portion spaced inwardly from said inwardly facing surface and defining an air gap therebetween near said pole boundary, said gap having a rounded radial profile with respect to said axis, and said second portion of said outer periphery being convex with respect to said axis.
A rotor for use in an electric motor, and rotatable about a longitudinal axis, said rotor comprising:
- a magnet having radially spaced outwardly facing and inwardly facing surfaces, axially spaced first and second ends, and at least two magnetic poles of different magnetic polarities circumferentially adjacent one another at a pole boundary;
- and
- a shaft having an outer periphery including a first portion engaging said inwardly facing surface, and a second portion spaced inwardly from said inwardly facing surface and defining an air gap therebetween near said pole boundary, and said gap having a polygonal radial profile with respect to said axis.
A rotor for use in an electric motor, and rotatable about a longitudinal axis, said rotor comprising:
- a magnet having radially spaced outwardly facing and inwardly facing surfaces, axially spaced first and second ends, and at least two magnetic poles of different magnetic polarities circumferentially adjacent one another at a pole boundary;
- and
- a shaft having an outer periphery including a first portion engaging said inwardly facing surface, and a second portion spaced inwardly from said inwardly facing surface and defining an air gap therebetween near each pole boundary, each gap having a discrete profile extending about a sector of the shaft's periphery.
A rotor for use in an electric motor, and rotatable about a longitudinal axis, said rotor comprising:
- a magnet having radially spaced outwardly facing and inwardly facing surfaces, axially spaced first and second ends, and at least two magnetic poles of different magnetic polarities circumferentially adjacent one another at a pole boundary;
- and
- a shaft having an outer periphery including a first portion engaging said inwardly facing surface, and a second portion spaced inwardly from said inwardly facing surface and defining an air gap therebetween near said pole boundary, said magnetic poles extending axially between said first and second ends and radially between said inwardly facing and outwardly facing surfaces, and said gap having a polygonal radial profile with respect to said axis.
A rotor for use in an electric motor, and rotatable about a longitudinal axis, said rotor comprising:
- a magnet having radially spaced outwardly facing and inwardly facing surfaces, axially spaced first and second ends, and at least two magnetic poles of different magnetic polarities circumferentially adjacent one another at a pole boundary;
- and
- a shaft having an outer periphery including a first portion engaging said inwardly facing surface, and a second portion spaced inwardly from said inwardly facing surface and defining an air gap therebetween near said pole boundary, said magnetic poles extending axially between said first and second ends and radially between said inwardly facing and outwardly facing surfaces, and said gap having a discrete profile with respect to said axis extending about a sector of said shaft.
A method of manufacturing a rotor for use in a low cogging torque brushless motor comprising;
- (a) providing a shaft having an axis, an outer surface, and axially opposite front and rear ends;
- (b) providing an annular magnet having axially spaced first and second ends and having an inner surface;
- (c) magnetizing said magnet to have at least two magnetic poles of opposite polarity circumferentially adjacent one another at a pole boundary;
- (d) engaging said outer surface with said inner surface;
- and
- (e) providing an air gap between said outer and inner surfaces near said pole boundary by providing a contoured portion in said outer surface of said shaft.
3 more elements
A method of manufacturing a rotor for use in a low cogging torque brushless motor comprising;
- (a) providing a shaft having an axis, an outer surface, and axially opposite front and rear ends;
- (b) providing an annular magnet having axially spaced first and second ends and having an inner surface;
- (c) magnetizing said magnet to have at least two magnetic poles of opposite polarity circumferentially adjacent one another at a pole boundary;
- (d) engaging said outer surface with said inner surface;
- and
- (e) providing an air gap between said outer and inner surfaces near said pole boundary, said gap having a profile extending about a discrete section of the shaft.
3 more elements
Dependencies are inferred from the claim text.