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Abstract

A method for improving the efficiency of a stepping motor (1) comprising a rotor (15) having a permanent magnet (16) producing a first magnetic field, as well as a first coil (13) and a second coil (14) for supplying to the magnet (16) respectively a second magnetic field (18) and a third magnetic field (19) symmetrical to one another in relation to an axis of symmetry (7) intersecting the axis of rotation (15a) of the rotor (15). The method comprises supplying to the motor (1), to make its rotor (15) turn in a given sense, drive pulses during which the two coils (13, 14) are supplied simultaneously by currents having a sense and an intensity such that, at the beginning of each drive pulse, the resultant magnetic field produced by the vectorial addition, in the magnet (16), of the second field (18) and the third field (19) forms, with another magnetic field (17) that results from the vectorial addition, in the magnet (16) of the two parts of the field produced by the latter magnet each of which flows through one of the coils (13, 14), an angle between 110.degree. and 160.degree. and having a sense, measured from the latter resultant field (17) towards the former, identical to the sense of rotation of the rotor (15). The claimed motor (1) may advantageously be controlled by this method due to the fact that its positioning means (21,22) are arranged such that, in each of the rest positions of the rotor (15), the aforesaid second resultant field (17) forms an angle (A) of from 20.degree. to 70.degree. with the axis of symmetry (7).

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