Electric motor

Claim 2

An electric motor comprising a permanent magnet stator magnetized to provide north and south poles alternating on the periphery thereof; a rotor having pole teeth of soft magnetic material concentric with said permanent magnet stator through a gap therebetween; a yoke of magnetic material having salient poles as many as the number of poles of said permanent magnet stator and formed facing the pole teeth of the rotor and adapted to form with said rotor a part of a magnetic circuit; and an exciting coil concentric with said permanent magnetic stator and interlinking with the magnetic circuit formed by said pole teeth and yoke; capable of varying the magnetic resistance between said pole teeth and said salient poles on the yoke according to the rotation angle of the rotor.

Claim 3

The device of claim 1 in which said yoke comprises a pair of spaced plates between which are located in spaced relation the stator and rotor and exciting coil, the pole teeth being circumferentially spaced along the rotor, the salient poles extending from at least one of the plates axially toward the rotor and being circumferentially spaced on such plate.

Claim 4

The device of claim 2 including a plurality of further salient poles extending from the other of said plates axially toward the other side of said rotor.

Claim 5

The device of claim 2 in which the salient poles on said one plate correspond in spacing to the poles on the permanent magnet stator and are double the number of pole teeth on the rotor and spaced at half the spacing thereof, said permanent magnet having a plurality of alternating north and south poles past which the pole teeth of the rotor are movable in closed spaced relation, said salient poles each being close spaced to one of said adjacent poles on said permanent magnet and being substantially centered thereon, each of the pole teeth when substantially centered on a pole of said permanent magnet also being substantially centered on and in close spaced relation with the corresponding one of said salient poles, the magnetic resistance in the circuit between a pole tooth and opposed permanent magnet pole being reduced by opposition of the salient pole to the pole tooth.

Claim 6

The device of claim 2 in which said salient poles on said one plate extend therefrom in tapered, frustoconical form and in which said pole teeth extend toward said salient poles in tapered, frustoconical form, to enable the rotor to be given a torque by the magnetic flux resulting from energization of the exciting coil, the pole teeth and salient poles being evenly circumferentially distributed.

Claim 7

The device of claim 1 in which the yoke comprises a pair of parallel side plates, an intermediate plate spaced therebetween, magnetic circuit completing means connecting the outer portions of said plates, a shaft extending through said plates, first and second chambers being defined on opposite sides of said intermediate plate by said side plates, said permanent magnet stator and rotor and exciting coil being radially distributed outwardly from the axis of the shaft in one of the chambers and a similar permanent magnet and rotor and coil being symmetrically disposed in the other chamber, said permanent magnets being disposed adjacent said intermediate plate, each said rotor having a central portion disposed between the corresponding permanent magnet and opposed side wall, said pole teeth extending substantially in parallism with said shaft radially outboard of said permanent magnet and radially inboard of said coil and toward said intermediate wall, one set of said salient poles extending from each side of said intermediate wall into said chambers in close spaced and facing relation with the free ends of said pole teeth so as to vary the magnetic resistance of the magnetic flux developed by the exciting coils and thereby utilizing the magnetic flux developed by the exciting coils to apply torque to each of the rotors for turning the shaft.