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A brushless, direct current, permanent magnet motor is disclosed, which comprises a stator and a rotor mounted for rotation about an axis in the stator. The stator has a plurality of stator teeth separated by axial interpolar teeth slots. Two pairs of ferrite ceramic magnets, formed as arc segments

A brushless, direct current, permanent magnet motor is disclosed, which comprises a stator and a rotor mounted for rotation about an axis in the stator. The stator has a plurality of stator teeth separated by axial interpolar teeth slots. Two pairs of ferrite ceramic magnets, formed as arc segments of equal circumferential length and axially constant radial thickness, are mounted on the rotor. Leading and trailing margins of each magnet are magnetized with a longitudinally varying magnetization strength or gradient while the central portion of each magnet is uniformly magnetized. This process produces axially alternating areas of low and high magnetization, which simultaneously cross each interpolar teeth slot upon rotor rotation to minimize cogging. An air gap of axially uniform width and the constant magnet thickness provides a constant reluctance path radially through the air gap and margins of the magnets.

대표청구항 ▼

[ Having thus defined the invention it is claimed:] [1.] A permanent magnetic motor comprising:a housing including a stator having an inner cylindrical surface from which a plurality of teeth between slotted openings extend radially outward therefrom for receiving windings wound between said teeth t

[ Having thus defined the invention it is claimed:] [1.] A permanent magnetic motor comprising:a housing including a stator having an inner cylindrical surface from which a plurality of teeth between slotted openings extend radially outward therefrom for receiving windings wound between said teeth to define stator poles;a rotor carrying a plurality of identical permanent magnets of alternating polarity affixed at equal circumferential increments about a longitudinally-extending rotatable shaft concentric with said inner surface, said magnets extending longitudinally along said shaft a distance about that of said inner surface and having an outer, generally cylindrical surface concentric with and spaced radially inward from said inner surface to define a constant physical, annular air gap therebetween; each magnet's outer surface circumferentially extending between a longitudinally-extending leading edge surface to a longitudinally-extending trailing edge surface;each magnet further having an imaginary trailing line and an imaginary leading line, each line positioned between said leading and trailing edges with said trailing line generally adjacent but spaced from said trailing edge to define a trailing edge margin of said magnet therebetween and said leading line generally adjacent but spaced from said leading edge to define a leading edge margin of said magnet therebetween; each magnet being uniformly magnetized to a first magnetic field strength between said leading and trailing edge margins while being magnetized to a periodic, undulating magnetic field strength which varies from said first magnetic field strength to a lesser second magnetic field strength along the length of said leading and trailing margins whereby cogging of said magnet is minimized.