FR2972871A1 - Electric motor i.e. low power electronically commutated brushless synchronous motor, for driving e.g. door, of closing/solar protection facility in building, has stator bars whose parts form outer portion extending parallel to rotation axis - Google Patents

Abstract

The motor has a rotor comprising disks (22a) rotatably fixed to a rotor shaft (21). A magnetic stator has a set of disjointed stator bars (31, 31') made of magnetically conductive material, where parts (312a, 312b, 312'a, 312'b) of the bars form an outer portion of the stator. The stator has a carrier structure (32) holding the bars such that the bars are fixed relative to each other. The structure is mounted such that the structure rotates on the shaft, axially outside the disks. The outer portion extends parallel to a rotation axis until the structure, where the axis is outside the disks.

Description

Electric motor and closure or sun protection system comprising such an engine

TECHNICAL FIELD The invention relates to the field of electromechanical actuators for motorized control of the occultation or sun protection elements in a building, such as blinds. In particular, it relates to a motor whose radial dimensions are reduced to be integrated with a tubular actuator. The invention relates in particular to the field of synchronous electric motors with low power electronic switching. Such motors must have a high torque in a small radial space, allowing them to be integrated in a blind winding tube or in a substantially rectangular section box, for example a Venetian blind rail. These particular dimensions encourage long engines, the length of the motor compensating for its small section to obtain the power required to drive the concealment element or sun protection.

PRIOR ART The motors currently used for these applications are DC motors with brushes, comprising a wound rotor and a ferrite permanent magnet stator. The rotor is connected to a rotating manifold. The current is injected via the brushes to the collector. This type of motor is commonly replaced by so-called brushless motors, operating without brushes. These include a wound stator while the magnets are placed on the rotor. An electronic control system must switch the current in the stator windings. This type of engine is used in particular in model aircraft, for DVD players / recorders or for small fans. It is known from US-A-4,556,809 to equip the rotor with an electric motor of disks equipped with magnets intended to cooperate with a stator, extending in the form of a cylinder around the rotor disks. The thickness of the stator increases the radial width of the motor. JP-A-2003/088068 discloses an electric motor or dynamo comprising two rotor discs mounted on the same shaft, and between which is placed a set of bars each provided with a copper winding to form the stator.

Permanent magnets are placed facing the windings on the faces of the rotor discs

2 turned towards each other. The chosen arrangement aims to improve the complex process of producing the windings, in particular the aforementioned cylindrical stator, and makes it possible to reduce the production waste. A stack of two structures on top of each other makes it possible to produce a large quantity of electricity.

The structure shown in this document is however not adapted to be integrated in an actuator tube, these axial and radial dimensions are almost equivalent in the case of a simple structure. The stack of two structures allows for a more elongated engine but the purpose of this stack is not to reduce the radial size, but to produce a larger amount of energy.

The invention therefore proposes to improve the existing devices for defining an electric motor structure dedicated to tubular actuators with the following objectives: reduced space requirement, in particular with regard to the radial size improvement of the sound level production of torque at speed reduced with rotor inertia ease of winding.

SUMMARY OF THE INVENTION To this end, the invention relates to an electric motor comprising a rotor and a wound stator, the rotor comprising a shaft, two disks mounted fixed in rotation on the shaft and permanent magnets fixed on these disks, then the rotor comprises coils interposed between the two discs, along an axis of rotation of the rotor. According to the invention, the permanent magnets of each disk of the rotor are arranged with their direction of polarity oriented radially relative to the axis of rotation. Thanks to the invention, a radial magnetic flux is created between each disk of the rotor and the opposite parts of the stator, which generates self-centering forces which maintain the rotor in position relative to the stator along the rotor. axis of rotation of the rotor. This facilitates assembly and limits the stress on the bearings supporting the rotor, while minimizing the vibrations produced. According to advantageous but non-mandatory aspects of the invention, such a motor may incorporate one or more of the following features, taken in any technically permissible combination: The magnets of one of the disks are arranged in opposition to the magnets of the other disc. The magnets are disposed on the outer periphery of the rotor discs. The outer periphery of the rotor discs is polygonal, having flat areas for the positioning of parallelepiped-shaped magnets. The outer periphery of the rotor discs is substantially circular, and the magnets have a curved structure. Sensors are positioned directly next to the magnets. The length of the coils, measured parallel to the axis of rotation of the rotor, is independent of the length of the magnets, measured parallel to this axis. The stator comprises a plurality of disjoint bars, these bars being fixed in rotation relative to each other by a bearing structure allowing the recovery of the radial forces. The bars have a section adapted to the magnets so that an air gap of substantially constant thickness is provided between a bar and a magnet when they are facing each other. - The bars are formed from a stack of machined sheets. - Bars are made of machined sintered steel. The support structure is provided with localized recesses for the passage of sensor parts and / or the maintenance of metal bars belonging to the stator. The bearing structure is mounted with the possibility of rotation on the shaft, axially outside the two disks. The stator also comprises a so-called internal part, in particular a portion of a coil, extending at least partially in a cylindrical space arranged along the axis between the discs and having a diameter equal to the diameter of the discs. rotor discs. Furthermore, the invention relates to a closure or sun protection system comprising a closure screen and a motor assembly, which comprises a motor as mentioned above. Such an installation is more economical to manufacture and simpler to put into service than those of the state of the art. DESCRIPTION OF THE FIGURES FIG. 1 shows a general perspective view of an engine according to the invention. FIG. 2 shows an isolated perspective view of the rotor of the motor of FIG. 1. FIG. 3 shows a partial perspective view of the engine of FIG. 1 making it possible to visualize the interior arrangement of different engine parts, such as bearings. , sensors, magnets and the rotor. Figure 4 is an isolated perspective view of the motor stator. Figure 5 is an isolated perspective view of a portion of the stator in the form of a bent bar.

Figure 6 is a schematic axial section of a portion of the motor elements.

DESCRIPTION OF AN EMBODIMENT The motor 1, according to the invention and shown in the figures, is a synchronous brushless motor. It comprises an electronic control unit 10, a rotor 20 and a stator 30. The motor has an elongate structure. Its length L1, measured parallel to an axis XX of rotation of the rotor 20, is at least twice its maximum diameter D1 measured radially with respect to this axis. In particular, a motor of diameter D1 equal to about 22 mm, for a length L1 of 45 to 50 mm will be particularly well suited for driving an interior blind. The electronic control unit 10 comprises a printed circuit 11 located at one end of the motor and a set of sensors 12, for example Hall effect probes, arranged inside the structure of the motor 1 and mounted on the printed circuit 11 with tabs 13. The sensors are all similar.

Each component 20 and 30 of the motor is shown and described independently hereinafter. FIG. 2 shows an embodiment of the rotor 20. The rotor has a "dumbbell" shaped structure, comprising a rotor shaft 21 as well as two rotor disks 22a and 22b mounted on the shaft. The term "disk" here designates an annular structure of cylindrical shape, the axial thickness of which may be small in front of its diameter. Both discs are fixed in rotation on the shaft. The rotor shaft defines the longitudinal axis XX of the engine. The various elements making up the engine are centered around this axis XX which is also the axis of rotation of the rotor 20. The rotor shaft 21 defines, at one of its ends, the output shaft of the engine 1.

Each rotor disk 22a or 22b comprises a set of magnets 24 in even number. The magnets are oriented radially, so as to create essentially radial flows. In other words, a straight line D24 from the North pole to the South pole of a magnet, which represents the direction of polarity of this magnet, extends in a radial direction relative to the axis XX. The N and S poles of some of the magnets are shown in Figure 2 to indicate the polarity direction of the magnets. The magnets of each disc are arranged successively in opposition. The poles of two adjacent magnets 24 of the same disk have opposite configurations. Thus, when a magnet has its North pole directed towards the axis XX and its South pole to the opposite, the two adjacent magnets have their South poles directed towards the axis XX and their North poles to the opposite, and vice versa . The magnets of the two discs are also arranged in opposition to each other. In other words, two magnets 24 located in the same angular sector of the disks 22a and 22b with respect to the axis XX have their poles in opposite configuration.

We denote L24 the axial length of a magnet 24, that is to say, its dimension along the axis XX. This is substantially equal to the axial thickness of the rotor discs. This dimension is smaller in the case of using a neodymium magnet with respect to a ferrite magnet, but these different solutions are conceivable. In this embodiment, the magnets are rectangular. They may be mounted on an inner face 23i, 25i of a disc facing the other disc or on the outer periphery 27 of each disc, as shown in Figure 2. In this case, the outer periphery of each disc n ' is not circular, but polygonal and has flat areas for the positioning of the magnets 24 which are parallelepipedal shape. This configuration limits the axial space required for mounting the magnets and allows the use of simple magnets commercially available. As a variant, the outer periphery of the discs 22a and 22b is substantially circular and the magnets 24 have a curved structure adapted to this periphery. In another variant, the outer periphery is covered by a magnetic material, so as to form an annular monobloc magnetization, having the same properties as the plurality of magnets described above. In addition, the radial orientation of the magnets of the rotor creates a large radial magnetic flux F, which is directly captured by the set of sensors 12 of the electronic control unit 10. The sensors 12 are in fact arranged directly opposite the magnets 24. The sensors 12 may be aligned with the magnets 24 in a direction parallel to the axis XX. Alternatively, other means for detecting the rotation of the rotor may be implemented, for example an encoder, if it is envisaged not to mount sensors at the motor structure. The flow F also interacts with the stator 30, as explained below, in particular in connection with FIG. 6.

The magnetic stator 30 comprises several stator bars 31, 31 'disjoint, that is to say independent of each other, mounted substantially parallel to the axis XX of the motor and distributed regularly about this axis. The bars are held by a support structure or carrying structure 32 preferably in two parts 32a and 32b, fitting axially into one another. The bearing structure is held in place around the shaft 21 of the rotor 20, with possibility of relative rotation, by means of bearings 50 preloaded on the shaft 21. These bearings are axially prestressed and located closer to the rotor discs to support at best the radial forces, closer to the section where they are generated, and outside thereof, in other words on the side of the outer faces 23e, 25e of the disks 22a and 22b, thus making the structure rigid. In practice, the bearings 50 are mounted against the outer faces 23e and 25e of the disks 22a and 22b. The carrier structure 32 makes it possible to limit the risk of bending of the rotor shaft if the latter is lengthened, insofar as the length likely to bend is limited. The various bars 31, 31 'of the stator consist of bundles of sheets assembled and provided at their ends with an indentation 34. This indentation 34 constitutes a zone of lesser radial thickness, with respect to the axis XX, relative to the other parts of the bars 31 and 31 '. This indentation constitutes the part by which the bars 31 and 31 'are positioned on the supporting structure 32. In a variant or in addition, zones of lesser radial thickness may be provided in the bars 31 and 31' to the right of the disks 22a and 22b , that is to say at the same level as these discs along the axis XX. A portion of the bars 31 and 31 'of the stator 30 extends opposite the magnets 24, parallel to the axis XX and at each rotor disc, providing an air gap E between them and the magnets. 312a and 312b are respectively noted the portions of the bars 31 which are arranged axially, along the axis XX, at the level of the magnets 24 of the discs 22a and 2211. Similarly, the portions 312a and 312b are bars 31 'which are arranged axially, parallel to the axis XX, at the level of the magnets 24 of the disks 22a and 22b. The portions 312a, 312b, 312'a and 312'b are disposed radially beyond the magnets 24, with respect to the central axis XX.

At least at the level of the magnets 24, the portions 312a, 312b, 312'a and 312'b have a section suitable for maintaining a constant air gap E e with respect to the magnets 24. In particular, for rectangular magnets arranged on adjacent flat faces made at the outer circumference of each disk of the rotor, the bars are substantially parallelepipedic. In the case where the magnets at the circumference of the rotor disks form an annular surface, the laminations constituting the bars 31 and 31 'can be machined and assembled to form a bar section substantially in the shape of an arc of a circle. , so as to maintain a constant air gap E with the magnets at the outer periphery of the discs. This other embodiment is not shown. The bars 31 and 31 'can be divided into two categories: those of a first type 31 are parallel to the axis XX of the engine and are substantially straight. Those of a second type 31 'each serve to support a coil 35 belonging to the stator 30. Each coil 35 consists of a winding of copper turns 37 between two flanges 36. The bars 31' supporting the coils are preferably bent, with a portion 314 'rectilinear and offset to the axis XX. More specifically, each bar 31 'comprises two connecting portions 316'a and 316'b oblique with respect to the axis XX and which respectively connect the portions 312'a and 312'b to the portion 314' which is parallel to the XX axis. A coil 35 is mounted around each portion 314 '. The coils 35 are thus shifted towards the axis XX of the motor, with respect to the outside diameter of the discs 22a and 22b. This decreases the maximum diameter D1 of the engine relative to the case where the bars 31 'would be straight. Once the assembly of the stator 30 has been completed, the coils 35 are flush with the outer surface of the support structure 32. In addition, the elbows 318'a, 318'b of the bars 31 ', which connect the parts 316'a and 316'b at the portion 314 ', maintain the flanges 36 and the windings 37 in place on these bars, without any other fastener is necessary. We denote L35 the axial length, measured parallel to the axis XX, of a coil 35.

In practice, the stator comprises six stator bars 31 and 31 ', of which only three, namely the bars 31', support coils 35. The use of a stator with three or six coils allows reduced torque oscillations relative to to a two-phase structure. The ratio between the number of magnets 24 and the number of coils 35 is known in the state of the art. Here, there are eight magnets for three or six coils.

The wound bars 31 'are arranged, around the axis XX, alternately with the non-wound bars 31. In a variant and if the diameter D1 allows it, all the bars support coils. The volume occupied by the coils 35 is located at least partially axially between the discs 22a and 22b, which makes it possible to reduce the maximum diameter D1 of the motor 1, whereas the supports of these coils, namely the stator bars 31 ', are partly outside this volume. The two parts 32a, 32b of the carrier structure 32, made of non-magnetic material, each comprise a support cylinder 41a, 41b and half-arms 42a, 42b, some of which are interlocked, parallel to the axis XX, in those the other part to form arms 42 at least partially framing some of the stator bars 31 and 31 '. The cylinder 41a, 41b of each portion 32a, 32b comprises a peripheral groove 43a, 43b and housings 39 for the ends of the stator bars 31. The housings 39 are located either at the periphery of the cylinder 41a or 41b of the support structure 32 at the bottom of a gorge. The ends of the bars 31, in particular the indented ends of lesser radial thickness, fit into these housings to allow recovery of the rotational forces. These are therefore taken closer to the bearings, the support cylinders 41a and 41b covering the bearings 50. The grooves 43a and 43b can accommodate O-rings 33a and 33b which participate in the maintenance of the structure and its suspension in a motor housing not shown. For this, the section of the joints is slightly greater than the depth of the grooves, so that the joints exceed them. In other words, the outer diameter of the joints is greater than that of the support structure. The arms 42a and 42b also participate in the recovery of the forces, but are not essential, the distance between the rollers 41a and 41b of the two parts of the support structure 32 can be simply fixed by the length of the stator bars 31. In such a way Similarly, the ends of the bars 31 'are also rotated by the support structure. In order not to weaken the support cylinders too much, it is intended that these bars be held by studs 42c extending from a support cylinder 41a or 41b towards the other support cylinder. These pads form two by two, as before, housing for holding the ends of the bars 31 'and allow the recovery of the radial forces exerted by these bars. Alternatively, all the stator bars 31 and 31 'could be maintained in the same way.

The cylinder 41a also comprises orifices 40 for the passage of the tabs 13 of the sensors 12 from the printed circuit to the magnets 24 of the rotor. FIG. 6 makes it possible to better understand the arrangement of the elements composing the structure of the engine 1 and the flows resulting therefrom.

In particular, the following measurements and zones are defined and shown: The ideal diameter DI of the motor 1 is equal to the sum of the maximum diameter DR of the rotor 20 (diameter of a rotor disk and thickness of the magnets), twice the maximum thickness ES of a portion 312a, 312b, 312'a or 312'b of a bar 31 or 31 'of the stator 30, at the disks 22a and 22b, and twice the air gap E. It is therefore governed by the equation DI = DR + 2x ES + 2xE

This ideal diameter DI may be equal to or slightly less than the maximum outside diameter D1 of the engine without its housing. Indeed, this ideal diameter DI can be increased, a slight thickness of the support structure 32 relative to the stator bars 31 and 31 'and / or part of the section of the O-rings 33a and 33b, to define the diameter D1. The section of the coils or windings 37 does not intervene in this diameter calculation, insofar as the coils 35 are completely integrated in the cylindrical space EC defined between the rotor disks 22a and 22b, along the axis XX. This cylindrical space EC is centered on the axis XX of the rotor shaft 21. It is delimited at its ends by the two inner faces 23i and 25i of the disks 22a and 22b and has for diameter the ideal diameter DI defined above. A space EC 'is defined between the rotor disks 22a and 22b, along the axis XX.

This cylindrical space is also centered on the axis XX and delimited at its ends by the faces 23i and 25i. Its diameter is the nominal diameter D22 of the discs 22a and 22b, without the magnets. The space EC 'is shown in gray in Figure 6. It is included in the EC space. A part of the stator, namely the stator bars 31 and 31 ', more precisely their parts 312a, 312b, 312'a and 312'b, extends to the right of the disks 22a and 22b, and extends from the sides and another of each rotor disc, opposite the EC space, to be held outside the rotor discs. Another part of the stator 30, namely the parts 314 ', 316'a, 316'b of the stator bars 31 and the coils 35, which may be described as internal, is partially housed in the space EC', that is to say between the discs 22a and 22b and closer to the axis XX than the magnets 24. Alternatively, the entire inner portion of the stator can be received in the space EC '.

Thus, along the axis XX of the motor can be defined a first zone ZT1 of mechanical strength of the bars 31 and 31 ', a first rotor disk zone ZR1, an internal zone ZI (in which there is a stator winding zone ZS), joining the internal faces of the rotor disks and whose length corresponds to the spaces EC and EC ', then a second rotor disk zone ZR2 and a second zone ZT2 of mechanical strength. Two arrows symbolize in Figure 6 a part of the flow F flowing between the magnets 24 of the rotor 20 and the bars 31 and 31 'of the stator 30. This radial flow is conducted along the metal bars, a disk 22a or 22b to the other disk. The flux losses are very small because of the presence of preferential flux paths constituted by the bars 31 and 31 'and the absence of other conductive elements, for example support elements for the stator in the cylindrical space. EC, which could disrupt this flow. Indeed, if the bearings were arranged in this space, they could interact with the magnetic flux, except to use nonmagnetic bearings, for example ceramic bearings, more expensive. The coils 35 are located mainly in the cylindrical rotor space EC and partially in the space EC ', but in a plane different from that of the rotor discs 22a and 2211. The rotor 20 and the stator 30 can therefore be dimensioned in a partially independent manner. : their sections and lengths can be dimensioned independently. In particular, the length of the coils 35, along the axis XX, is adaptable without modifying the diameter D1 of the motor 1. The number of turns of windings 37, and therefore the value of Amp.tr, can therefore be increased to increase the torque obtained on the rotor. The axial thickness of the rotor discs 22a and 22b, and thus of the magnets 24, can also be adapted to increase the flux F. In other words, the axial length L35 of the coils 35 is independent of the geometry of the rotor, in particular the axial length L24 of the magnets 24, and vice versa. Thus, the invention gives the designer of an electric motor a great freedom as to the choice of the length of the windings 37 and the choice of the width of the magnets 24, which makes it possible to adjust the torque induced on the rotor and the flux magnetic transmitted between the stator 30 and the rotor 20. From the same basic configuration and one for the same maximum diameter D1, it is possible to obtain a range of several output torques for the motor. The motor 1 thus has a very interesting modular structure, which is particularly advantageous for the production of a range of different motors, with the same maximum diameter D1.

In addition, by varying the nominal diameter D22 or the outer diameter DR of the disks 22a and 22b, it is also possible to vary the output torque of the motor which is proportional to the square of this diameter. The gap E, made between the bars 31 and 31 'of the stator 30 and the magnets 24 of the rotor 20, when they are arranged radially on the periphery of the discs, is situated at the largest possible radius with respect to the outer diameter D1 of the rotor. motor, which optimizes the torque provided by the motor 1 relative to the outside diameter D1 of the engine. It is easily adjustable due to the very small rib chain. This configuration also has the advantage, in addition to the compactness of the engine 1 which is discussed above, a good distribution of electromagnetic fields in radial and axial directions. In particular, the radial orientation of the magnets in opposition creates a set of self-centering forces on the rotor 20, which makes it possible to stabilize the structure of the motor 1, in particular in the case where the number of magnets and the number Stator bars are even numbers. These efforts contribute to a better holding of the parts vis-à-vis each other and facilitate the mounting and insertion of the internal structure of the engine in an external cylindrical housing not shown. The multiplication of parts constituting an engine structure as described, if it facilitates the assembly and production of the engine, also increases the risks of inducing noise vibrations that generate noise. The following solutions contribute to improving the acoustic performance of the engine, in particular to reduce the noise generated during operation: The magnetic forces themselves contribute to the maintenance of the structure: the axial flows between parts are minimized, in favor of radial flows F. The possible axial or radial forces are countered by the presence of the bearings 50, closer to where these efforts are generated. The prestressing of the bearings also makes it possible to reduce the axial clearances. The coaxial structure of the engine 1 has a reduced coastline, games and radial forces are better controlled. The O-rings 33a and 33b make it possible to construct a self-supporting structure and to create a vibration absorption zone when the engine structure is mounted in a housing. They are inserted at the indentations 34 provided at the ends of the stator bars 31 and 31 'and which form a retaining groove of the O-rings. As a result, the required internal diameter of the crankcase is slightly greater than the diameter of the DI structure. It is also possible to provide stalling the ends of the stator bars at their housing 39 in the support structure 32, using a vibration damping material and / or reducing the mounting clearance.

Moreover, the following solutions contribute to improving the performance of the engine, particularly in terms of torque: The windings 37 can be mounted on each of the stator bars 31 and 31 '. To optimize the space taken by these windings, each is then positioned on a right or left half-zone in the stator zone ZS, alternately around the rotor shaft. The bars 31 and 31 'can be bent accordingly. They are then asymmetrical, but the same bar, according to its assembly, can be used to support a coil of half-zone right or left. The section of each stator bar 31 or 31 'is advantageously rounded, for example in the form of an oval, which avoids projecting ridges and facilitates the winding with an optimized diameter: the number of turns of a coil 35 is then increased to the same outside diameter, compared to a bar of square or rectangular section. The stator bars 31 and 31 'can be made differently than by a stack of sheet metal plates. In particular, the use of a magnetic material, such as sintered steel, can produce rounded section bars, which is more difficult to achieve in sheet metal plates. The engine 1 as described has a single output shaft. However, the structure can be made more symmetrically to allow for a dual output shaft motor. The electronic control unit can be positioned on one side only. The motor 1 described above is particularly advantageous for use in a closure or sun protection system. A closure or sun protection system comprises a movable screen, roller blind type or Venetian blind, or door, grid or shutter, movable at least between an expanded configuration where it closes or hides a building opening and a rolled position , where he frees access to this opening. The motor 1 described above can be easily integrated into the winding shaft of such an installation, while presenting a simplicity of assembly and reliability in operation particularly attractive. This motor can easily be adapted to its conditions of use, by adjusting the axial length of the zone ZS, that is to say the length L35 of the coils 35, the diameter D22 or DR or the thickness of the disks 22a and 22b of the rotor.

Claims (15)

REVENDICATIONS1. Electric motor (1) comprising a rotor (20) and a wound stator (30), the rotor comprising a shaft (21), two disks (22a, 22b) mounted rotatably on the shaft and permanent magnets (24) fixed on the discs, the stator comprising coils (35) interposed between the two discs, along an axis (XX) of rotation of the rotor, characterized in that the permanent magnets of each disc of the rotor are arranged with their direction of polarity (D24) oriented radially with respect to the axis of rotation. 2. Motor according to claim 1, characterized in that the magnets (24) of one (22a) disks are arranged in opposition to the magnets (24) of the other disk (22b). 3. Motor according to one of the preceding claims, characterized in that the magnets (24) are arranged on the outer periphery of the discs (22a, 22b) of the rotor (20). 4. Motor according to the preceding claim, characterized in that the outer periphery of the discs (22a, 22b) of the rotor (20) is polygonal, having flat areas for the positioning of parallelepiped-shaped magnets. 5. Motor according to one of claims 1 to 3, characterized in that the outer periphery of the discs (22a, 22b) of the rotor (20) is substantially circular, and in that the magnets (24) have a curved structure. 25 6. Motor according to one of the preceding claims, characterized in that sensors (12) are positioned directly opposite the magnets (24). 7. Motor according to one of the preceding claims, characterized in that the length (L35) of the coils (35), measured parallel to the axis of rotation (XX) of the rotor 30 (20), is independent of the length ( L24) magnets (24), measured parallel to this axis. 8. Motor according to one of the preceding claims, characterized in that the stator (30) comprises a plurality of disjointed bars (31, 31 '), these bars being fixed relative to each other by a carrier structure (32). ) allowing the recovery of radial forces. 9. Motor according to the preceding claim, characterized in that the bars (31, 31 ') have a section adapted to the magnets (24) so that a gap of substantially constant thickness is provided between a bar and a magnet. when they are opposite. 10. Motor according to one of claims 8 or 9, characterized in that the bars (31, 31 ') are formed from a stack of machined sheets. 11. Motor according to one of claims 8 or 9, characterized in that the bars are formed of machined sintered steel. 12. Motor according to one of claims 8 to 11, characterized in that the carrier structure (32) is provided with localized recesses (39, 40) for the passage of parts (13) of sensors (12) and / or maintaining metal bars (31) belonging to the stator. 13. Motor according to the preceding claim, characterized in that the carrier structure (32) is mounted with the possibility of rotation on the shaft (21) axially outside the two discs (22a, 22b). 14. Motor according to one of the preceding claims, characterized in that the stator (30) also comprises a portion (314 ', 316'a, 316'b, 35), said internal, in particular, a part of a winding, extending at least partially in a cylindrical space (EC ') formed along the axis between the discs (22a, 22b) and having a diameter equal to the diameter (D22) of the discs (22a, 22b) of the rotor (20). 15. A closure or sun protection system comprising a closure screen and a motor assembly, characterized in that the motor assembly comprises a motor (1) according to one of the preceding claims.