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A synchronous motor, in particular a stepping motor, with two coaxial stator sections which are each provided with a ring coil and with two circular systems of teeth, which are shifted by half a tooth pitch relative to each other. The two stator sections are shifted by a quarter tooth pitch relative

A synchronous motor, in particular a stepping motor, with two coaxial stator sections which are each provided with a ring coil and with two circular systems of teeth, which are shifted by half a tooth pitch relative to each other. The two stator sections are shifted by a quarter tooth pitch relative to each other. In addition, the motor comprises an axially magnetized permanent-magnetic ring which is disposed between the two stator systems, for magnetizing the two systems of teeth of the stator sections with mutually the same polarity. The two systems of teeth of each stator section are constituted by annular parts which are provided with teeth at the inner circumference. The annular parts form part of the magnetic circuit which surrounds the annular coil and are disposed concentrically in such a way that the axial distance between the teeth of both systems is at least a few times greater than the air gap between stator and rotor.

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A synchronous motor which comprises: first and second coaxial spaced stator sections, each stator section including at least one annular coil, each stator section being annular and including a plurality of teeth arranged in two circular systems on the inner surface of said stator, the number of teet

A synchronous motor which comprises: first and second coaxial spaced stator sections, each stator section including at least one annular coil, each stator section being annular and including a plurality of teeth arranged in two circular systems on the inner surface of said stator, the number of teeth in all stator systems being equal and the spacing between adjacent teeth in all stator systems being uniform, said annular coils being each surrounded by a soft ferromagnetic material, said ferromagnetic material and said annular coils constituting a magnetic circuit, said motor further including a rotor having a geometric axis and first, second, third, and fourth circular axially spaced systems of teeth which each comprise a plurality of teeth which are uniformly spaced about the circumference of said rotor, the number of teeth in each of said systems being equal to the number of teeth in every other rotor system and also equal to the number of teeth in each system of teeth in said stator, said systems in said rotor being disposed respectively in first, second, third, and fourth planes which are each disposed in substantially normal relationship to said geometric axis of said rotor, each plane in which one of said systems of said rotor is disposed also having one of said systems of said stator disposed therein, each of said systems of said rotor co-operating with one of said systems of said stator, said two systems of teeth in each of said stator sections being shifted angularly by substantially half of a tooth pitch relative to each other and said two stator sections being shifted angularly with respect to each other by substantially a quarter of a tooth pitch, said motor including a single permanent magnet which is disposed axially intermediate said stator sections and which magnetizes two systems of stator teeth which are in the same section and which are also in said first and second planes with substantially identical polarity distributions and two systems of teeth in the same section which are also in said third and fourth planes with substantially identical polarity distributions which are opposite to the polarity distributions of the systems in said first and second planes, said soft ferromagnetic material and said two systems of teeth in each stator section comprising part of a magnetic circuit which surrounds said annular coil of said stator sections, the axial distance between the teeth of said systems in one of said stator sections being at least a few times greater than the spacing between each system of stator teeth and the system of rotor teeth associated therewith, said stator sections being divided into an even number of pie shaped segments along axial surfaces, the stator teeth for each stator section being shifted by half a tooth pitch relative to the rotor teeth in circumferentially successive segments and said single permanent magnet magnetizing both systems of each circumferentially successive pie shaped segment with opposite polarities.