CH683810A5 - Polyphase stepper motor - has axially centred permanent magnet rotor, and magnetic stator circuit having at least two parts, each comprising two principal poles, and intermediate poles - Google Patents

Abstract

The motor comprises a permanent magnet rotor (3) with N pairs of poles arranged around a central axis, with the magnets extending parallel to the axis. A magnetic stator circuit has at least two phases (4a,5a;4b,5b), each formed of two principal poles having min slots or teeth extending perpendicular to the axis. Each stator circuit is connected at each end of the slot to an end of a core carrying a coil. An intermediate polar piece (6a,6b) extends in the same plane as the principal poles, and has intermediate slots located w.r.t. the main slots and engaged between them. The rotor extends parallel to the poles. ADVANTAGE - Has large number of poles, with simple construction. Reduced parts. Increased precision of relative positioning of poles.

Description

1

CH 683 810 A5

2

Description

The present invention relates to a multipolar and polyphase stepping motor comprising a rotor with permanent magnetization with N pairs of poles distributed around a central axis and magnetized in a direction parallel to this axis and a stator magnetic circuit comprising several phases.

Stepper motors of the type corresponding to the preamble are known, in particular from patent specification CH 653 189. In the description of invention CH 653 189, there is described a motor represented by FIGS. 1, 2 and 3. Each phase of the stator winding of this motor is constituted by a set of elementary circuits 12 'and 12 "forming several U-shaped branches coupled with a coil 13', 13" ... Such provision has, on the one hand, the disadvantage of a high manufacturing cost because of the number of elementary parts to be assembled with precision and, on the other hand, a significant average length of coil, which causes more ohmic losses high.

The object of the present invention is to remedy the shortcomings of motors of the kind mentioned, by proposing a new arrangement making it possible to produce a polyphase motor with a large number of poles in a simple and economical construction.

The invention will be better understood with the aid of the description which follows and of the drawing which illustrates it by way of example, a drawing in which:

- fig. 1 shows a view in the axial direction of the multipolar rotor;

- fig. 2 shows an example of execution of the engine according to the invention;

- fig. 3 shows a first alternative embodiment of the engine according to FIG. 2;

- fig. 4 shows a second variant of the engine according to FIG. 2.

Fig. 1 shows a schematic view of the rotor with permanent magnetization in the axial direction. This rotor has at the two surfaces perpendicular to its axis of rotation a distribution of alternating North and South induction with a polar pitch ar.

Fig. 2 shows an embodiment of the engine according to the invention. This motor comprises two phases a and b, each of which consists of two main pole pieces 4 and 5 (4a, 4b, 5a, 5b), an intermediate pole piece 6, a coil core 1 and a coil 2. The main pole pieces and intermediates, as well as the coil core are made of a soft ferromagnetic material. The pole pieces have teeth distributed around the axis of rotation. The teeth of the main and intermediate pole pieces are nested in order to create an alternating north and south induction distribution on the surface of the stator when a current flows in the coil 2. The rotor 3 rotates around the axis 10 in a plane parallel to that of the pole pieces.

Fig. 3 shows a first alternative embodiment of the example of FIG. 2. In this alternative embodiment, the pole pieces 6a and 6b of the 2 phases are replaced by a single intermediate pole piece 6. The measurements have shown that this replacement had no harmful effect on the operation of the engine, but that on the other hand, at the level of realization, it presented an economy at the level of the assembly of the engine.

Fig. 4 shows a second variant of the engine according to FIG. 2. In this variant, in addition to the single intermediate pole piece 6, all of the main pole pieces 4 and 5, as well as the coil core 2, are replaced by a single piece of soft ferromagnetic material 7. This variant has the advantage of reducing the number of engine components and increasing the relative positioning accuracy between the main pole pieces.

Claims (3)

Claims 1. Multipolar stepping motor comprising a rotor with permanent magnetization with N pairs of poles distributed around a central axis and magnetized in a direction parallel to this axis and a stator magnetic circuit comprising at least two phases, characterized in that each said phase of the stator magnetic circuit is formed by two main pole pieces provided with main teeth, extending in the same plane perpendicular to said axis and each connected at one end of a coil core carrying a coil, of a pole piece intermediate extending in the same plane as that of the main pole pieces and having intermediate teeth located opposite the main teeth and engaged between them, and in that the rotor extends in a plane parallel to that of the pole pieces. 2. Motor according to claim 1, characterized in that the intermediate pole pieces of the different phases of the stator magnetic circuit are magnetically connected together to form a single assembly. 3. Motor according to claim 1 or according to claim 2, characterized in that the main pole pieces and the coil core of each phase constitute a single and inseparable assembly. 5 10 15 20 25 30 35 40 45 50 55 60 65 2