Permanent magnet type rotor and permanent magnet type rotary electrical machine
View Patent ↗A number of embodiments of rotating electrical machines using permanent magnets wherein the cogging torque is substantially reduced as are vibrations caused by magnetic flux variations. This is accomplished by disposing the coil windings in equal circumferential spacing and disposing the associated permanent magnets in non-symmetrical relationship so that the gaps between some of the magnets are different. In addition, the coil windings are such that no two coils of any phase are immediately adjacent each other in a circumferential direction. A method for calculating the optimum spacing is also disclosed.
1. A permanent magnet rotary electric machine having a rotor and a stator, one of said rotor and said stator comprising a plurality of permanent magnets disposed such that polarities of adjacent magnets are different from each other, the other of said rotor and said stator comprising a plurality of electrical coils wound around cores juxtaposed to said permanent magnets for cooperation therewith, said coil windings being arranged in groups of coil windings, the coil windings of said groups having their windings connected to each other and common ends, no two coil windings of each group being circumferentially adjacent to the other, all said permanent magnets being of substantially of the same shape with a circumferential offset angle of each permanent magnet from a regularly disposed position being set such that a cogging number per rotation of the rotor is equivalent to as the least common multiple of the number S of slots between the electrical winding cores and the number P of magnetic poles and one of said cores and said permanent magnets being disposed in nonsymmetrical relation to the axis of rotation of said machine.
2. A permanent magnet rotary electric machine as set forth in claim 1 , wherein the number S of slots is eighteen, the number P of magnetic poles is twelve, and the twelve permanent magnets are divided into four sets, each set comprising three circumferentially adjacent permanent magnets, the circumferential pitch angle of the three permanent magnets of each set is 26.70°, and the circumferential pitch angle of adjacent two permanent magnets between the sets is 36.60°.
3. A permanent magnet rotary electric machine as set forth in claim 1 , wherein the number S of slots is eighteen, the number P of magnetic poles is twelve, and the twelve permanent magnets are divided into four sets, two of said four sets comprising three circumferentially adjacent permanent magnets, the circumferential pitch angle of the three permanent magnets of each set is 26.7°, and the circumferential pitch angle of permanent magnets within the other two sets disposed at a symmetrical position is 33.3°.
4. A permanent magnet rotary electric machine as set forth in claim 1 , wherein the number S of slots is eighteen, the number P of magnetic poles is twelve, and the twelve permanent magnets are divided into four sets of three circumferentially adjacent permanent magnets, the circumferential pitch angle of the three permanent magnets of each set is 28.3°, and circumferential pitch angles of adjacent permanent magnets between adjacent different sets are set to 33.3°, 28.3°, 33.3° and 28.3° circumferentially in this order.
5. A permanent magnet rotary electric machine having a rotor and a stator, one of said rotor and said stator comprising a plurality of permanent magnets disposed such that polarities of adjacent magnets are different from each other, the other of said rotor and said stator comprising a plurality of electrical coils wound around cores juxtaposed to said permanent magnets for cooperation therewith, said coil windings being arranged in groups of coil windings, the coil windings of said groups having their windings connected to each other and common ends, no two coil windings of each group being circumferentially adjacent to the other, wherein the magnitude of the torque exerted on each permanent magnet is determined separately by a computer numerical analysis and peaks or bottoms of the torque curves of said permanent magnets are offset from each other with respect to the rotation angle of the rotor so that the cogging number is increased.