Electromechanical actuator including compact and low noise synchronous reluctance motor

Abstract

The invention relates to an electromechanical actuator for actuating a shading device, such as a roller blind or a blind, comprising a housing, a head intended to be fastened to a fixed structure, a synchronous motor, a speed reducer and a motor control unit, the motor, the speed reducer and the control unit being inserted into the housing of the electromechanical actuator, the motor comprising: a cylindrical rotor; a cylindrical stator disposed coaxially around the rotor and including a plurality of teeth extending radially toward the rotor; and a coil wound around each of the teeth of the stator; the stator has an outer diameter of less than 55 mm, the rotor is formed from an assembly of sheet metal plates and comprises recesses around a longitudinal axis of the rotor, the rotor comprises an arrangement of recesses forming four magnetic poles, each magnetic pole of the rotor comprising two or three recesses.

Description

Technical Field

[0001] The present invention relates to the field of electric motors and more specifically to the field of synchronous "brushless" electric motors ranging in power from a few tens of watts to a few hundred watts. Such motors are implemented, for example, in electromechanical actuators in the field of home automation devices. These actuators are used in particular to rotate winding shafts or tubes to drive rolling blinds or shutters for covering windows or doors of buildings. Background Art

[0002] A synchronous "brushless" electric motor conventionally comprises a rotor and a stator comprising a plurality of windings. In applications where the motor is fitted to an electromechanical actuator driving a winding tube in rotation, it is desirable for space reasons to house the actuator in the winding tube, which imposes considerable constraints on the actuator in terms of volume and temperature. In practice, the motor itself is encapsulated in a housing of the actuator, which is usually made of metal. The diameter of the motor is therefore limited to a few centimeters. Under these conditions, it is difficult to ventilate the motor. On the other hand, the actuator may also be subjected to high temperatures when it is mounted in a winding tube of a roller blind or shutter mounted on a facade of a building. The length of the motor is also reduced as much as possible to allow the actuator length to be adapted to the widest range of applications.

[0003] In the field of synchronous "brushless" electric motors, synchronous reluctance motors are becoming increasingly popular due to their performance, especially in terms of power-to-weight ratio and noise, compared to other motors, such as squirrel-cage induction motors. Synchronous reluctance motors can provide either sinusoidal or trapezoidal signals. Synchronous reluctance motors also often include Hall effect sensors to detect the position of the rotor relative to the stator.

[0004] One of the main advantages of synchronous reluctance motors is that they can be operated without magnets. This feature makes it possible to limit production costs and overcome any difficulties in procuring magnets. However, the main difficulties lie in and especially in the construction of the rotor, whose diameter is particularly small.

[0005] However, by reducing the size of the motor, resonance phenomena occur between the electromagnetic forces generated within the motor and the mechanical elements of the motor. These resonance phenomena correspond to a noise spectrum that may include peaks in the audible frequency range that can prove to be annoying to humans.

[0006] It is therefore desirable to propose improvements to synchronous reluctance type motors in order to adapt their manufacture without compromising their performance in terms of torque produced, power consumption, heat released and noise generated. Summary of the invention

[0007] An embodiment relates to an electromechanical actuator for actuating a shielding device, such as a roller blind or a shutter, comprising a housing, a head intended to be fastened to a fixed structure, a permanent magnet synchronous motor, a reducer and a motor control unit, the motor, the reducer and the control unit being inserted into the housing of the electromechanical actuator, the motor comprising: a cylindrical rotor; a cylindrical stator, which is coaxially arranged around the rotor and comprises a plurality of teeth extending radially towards the rotor; and a coil, which forms a winding around each of the teeth of the stator; characterized in that the stator has an outer diameter of less than 55 mm, the rotor is formed by an assembly of metal sheet plates, the rotor comprises a recess around the longitudinal axis of the rotor, the rotor comprises an arrangement of recesses forming four magnetic poles, each magnetic pole of the rotor comprising two or three recesses.

[0008] The motor actuator thus defined is particularly compact and inexpensive, while providing performance particularly suitable for low-torque roller blind control applications. In particular, this rotor manufacturing technology has proven to be particularly cheap and fast. In addition, it makes it possible to easily vary the length of the motor according to the desired performance, in particular the torque provided by the motor. The influence of the number of recesses on the torque value that the motor can provide must be balanced by the technical feasibility of manufacturing these housings in the space of the rotor section and the mechanical strength of the rotor. Therefore, the optimal number of recesses per pole is equal to two or three.

[0009] According to one embodiment, the stator comprises six teeth.

[0010] The motor diameter can be reduced by choosing a reduced number of "magnetic" poles and windings, without affecting the motor performance in terms of torque, power consumption and heat dissipation. 6 windings / 4 "magnetic" pole pairs offer interesting performance in the field of blinds and roller shutters applications, with a particularly compact stator.

[0011] According to one embodiment, the rotor comprises a first rotor groove extending on a cylindrical surface of the rotor facing each of the poles, the first rotor groove being centred on a line outside a first median plane of the pole passing through the longitudinal axis of the rotor.

[0012] By modifying the air gap permeability of the motor, this first groove makes it possible to attenuate annoying peaks in the spectrum of noise emitted by the motor, without significantly affecting the performance of the motor.

[0013] According to one embodiment, the rotor comprises a second rotor groove extending on a cylindrical surface of the rotor facing each of the magnetic poles.

[0014] The second groove also changes the air gap permeance of the motor and thus may also change the noise spectrum.

[0015] According to one embodiment, the first rotor groove and the second rotor groove are arranged symmetrically with respect to the first plane.

[0016] This second groove makes it possible to make the behavior of the motor symmetrical in both directions of rotation, so that the same result is obtained regardless of the direction of rotation of the motor. Thanks to this arrangement, the symmetry of the behavior of the motor in terms of noise and performance can be adapted to the operation of the actuator for winding or unwinding the mobile screen, regardless of the direction in which the actuator is mounted.

[0017] According to one embodiment, the first rotor groove or the second rotor groove or each of the first rotor groove and the second rotor groove has at least one of the following features:

[0018] an angular position between 0° and 35° about the longitudinal axis of the rotor relative to the first plane, the semicircular segment, and

[0019] Semicircular segment with a radius between 0.4 and 1.8 mm.

[0020] According to one embodiment, each tooth of the stator comprises a stator groove formed in a free end of the tooth.

[0021] This arrangement, in combination or not with one or two grooves on the rotor, also makes it possible to reduce the audible noise peaks emitted by the motor without significantly affecting the performance of the motor.

[0022] According to one embodiment, the stator groove formed in each tooth of the stator has at least one of the following features:

[0023] The stator groove is located centrally in a second middle plane of the tooth passing through the longitudinal axis of the stator,

[0024] The stator grooves have a width of 0.2 to 3 mm, and

[0025] The stator grooves have a depth of 0.2 to 6 mm.

[0026] The central position of the grooves in the teeth of the stator makes it possible to further reduce the audible noise peaks emitted by the motor.

[0027] According to one embodiment, the actuator is powered by an AC power grid.

[0028] According to one embodiment, the control unit applies a sinusoidal or trapezoidal control to the motor.

[0029] The performance of the motor can be achieved by any of these control types.

[0030] According to one embodiment, the stator is formed from an assembly of metal sheet plates.

[0031] This manufacturing technique proves to be particularly rapid and inexpensive. In addition, it makes it possible to easily vary the length of the stator according to the desired performance, in particular the torque to be provided by the motor. In addition, this technique makes it possible to simplify the production of the grooves which can be obtained by forming the notches in the sheet metal plate.

[0032] According to one embodiment, the motor has a power less than or equal to 300W.

[0033] The aforementioned features of the motor are particularly suitable for use in motors within this power range.

[0034] According to one embodiment, the thickness of the sheets forming the rotor is between 0.3 and 0.7 mm, preferably 0.5 mm.

[0035] Embodiments may also relate to a screening device of the roller blind or shutter type comprising an actuator as previously defined. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be better understood from the following description with reference to the accompanying drawings, in which like reference numerals correspond to structurally and / or functionally identical or similar elements.

[0037] Figure 1 are schematic perspective views and longitudinal cross-sectional views of a synchronous reluctance motor according to one embodiment,

[0038] Figure 2 is a schematic cross-sectional view of a synchronous reluctance motor according to one embodiment,

[0039] Figure 3 is a schematic side view of a rotor of a synchronous reluctance motor according to one embodiment,

[0040] Figure 4 is a schematic cross-sectional view of a rotor according to one embodiment,

[0041] Figure 5 is a schematic top view of a rotor plate according to one embodiment,

[0042] Figure 6 is a schematic top view of a rotor plate according to another embodiment,

[0043] Figure 7 is a schematic top view of a rotor plate according to another embodiment,

[0044] Figure 8 , Fig. 8A is a schematic cross-sectional view of a synchronous reluctance motor according to one embodiment, Fig. 8A yes Figure 8 A magnified view of a portion of

[0045] Fig. 9 is a schematic cross-sectional view of a rotor according to another embodiment,

[0046] Fig.10 is a schematic cross-sectional view of a rotor according to another embodiment,

[0047] Fig.11 is a schematic cross-sectional view of an actuator according to one embodiment,

[0048] Fig.12 is a schematic perspective view of a home automation device according to one embodiment. DETAILED DESCRIPTION

[0049] Figure 1 and Figure 2 A synchronous reluctance motor 1a according to an embodiment is shown. The motor 1a comprises a stator 2, a rotor 3 and a shaft 4 fixed to the rotor, these three elements being coaxial and housed in a housing 6. The housing 6 is fixed to the stator 2 and connected to the shaft 4 via bearings 5, for example of the ball bearing type.

[0050] exist Figure 2 In the embodiment of the present invention, the stator 2 has a hollow cylindrical shape 20 and comprises teeth 21 extending radially towards the inside of the cylindrical part 20. The teeth are designed to each receive a winding 11. The teeth 21 may each have a free end extending through a tile-shaped plate 23.

[0051] According to one embodiment, the rotor 3 is a transverse lamination type, also called a flux barrier type, without magnets. Therefore, the rotor 3 has a cylindrical outer contour, inside which recesses 31a, 31b forming a flux barrier are formed. The recesses 31a, 31b are distributed around the longitudinal axis X of the rotor and are grouped in pairs with the longitudinal plane of the rotor 3 as the center. Each pair of recesses 31a, 31b includes a recess 31a farther from the longitudinal axis X of the rotor 3 and a recess closer to the axis. The rotor also has a central hole 36, in which the shaft 4 driven to rotate by the rotation of the rotor 3 is fastened. The symmetrical geometric arrangement of different recesses, and therefore the symmetrical geometric arrangement of different flux barriers around the longitudinal axis X of the rotor, produces rotor poles, such as four poles. The curved plates 23 at the ends of the teeth 21 of the stator match the cylindrical shape of the rotor 3, while maintaining a substantially constant air gap in the facing area between each plate 23 and the outer contour of the rotor 3.

[0052] exist Figure 2 In the example of , the stator 2 includes six teeth 21 , and the rotor 3 includes four magnetic poles formed by the arrangement of recesses.

[0053] The axial length of the rotor 3 may be greater than that of the stator so as to be able to capture the magnetic flux generated by the arrangement of the rotor recesses by means of a Hall Effect sensor which gives the position of the rotor required for driving the motor 1 a.

[0054] The stator 2 has an outer diameter of less than 55 mm, for example between 35 and 55 mm. It may have a length between 14 and 20 mm. The rotor 3 may have a diameter between 18 and 25 mm and a length between 18 and 25 mm. The air gap may be between 0.2 and 0.6 mm, for example equal to 0.3 mm.

[0055] The coil forming the winding 11 around the tooth 21 can be single or double layer, with a tooth type or a concentric distribution type. The coil can be made of 0.12 to 0.2 mm copper wire to form 700 to 1000 turns around the tooth 21.

[0056] The stator 2 and the rotor 3 may be made of a stack of a plurality of plates cut from a metal sheet having a small thickness (for example between 0.3 and 0.7 mm). These plates may be assembled by stapling, in particular to ensure their alignment. Thus, Figure 3 shows a rotor 3 formed by a stack of two types of plates 33, 34, the plates 34 forming the magnetic shunt. Figure 3 In the example of , the rotor 3 is formed by 40 plates 33 , 34 , including: three plates 34 , then a group of sixteen plates 33 separated by plates 34 , a group of nineteen plates 33 , and finally one plate 34 .

[0057] Figure 2 and Figure 4 The shape of the plate 34 of the rotor is shown, wherein two recesses per pole form a flux barrier. The recesses 31a, 31b forming the flux barrier are essentially components of straight sections. For example, Figure 4 and Figure 5 As shown, the cross section of the recess may be rectangular at the middle level of the pole, with substantially trapezoidal extensions extending on both short sides.

[0058] The straight section concave section can be defined by the following parameters:

[0059] The radius RE of a circle centered on the longitudinal axis X of the rotor 3, outside which the recesses 31a, 31b are formed,

[0060] The width BW of the center portion of the recesses 31a and 31b is

[0061] The half angle Aa, Ab of the extension of each of the recesses 31a, 31b around the longitudinal axis X of the rotor 3, and

[0062] Each of the recesses 31a, 31b on the edge of the rotor has an opening angle Ga around the longitudinal axis X of the rotor.

[0063] according to Fig. 9 In the alternative embodiment shown, the recesses 31a', 31b' forming the flux barriers have a cross section substantially in the form of a ring segment and can be defined by the following parameters:

[0064] The radius Rba of the bottom of the first recess 31a closest to the edge of the rotor,

[0065] The radius Rbb of the bottom of the second closest recess 31b,

[0066] The intermediate radius Rfer between the first and second recesses 31a, 31b,

[0067] The width LB of the recesses may be the common width of all recesses.

[0068] Other flux barrier geometries are contemplated without departing from the scope of the present invention.

[0069] According to the embodiment with two recesses per pole, the recesses 31a, 31b extend in pairs along a radius of the rotor 3 and are spaced apart from each other and from the longitudinal axis X of the rotor.

[0070] according to Fig.10 In the alternative embodiment shown, each pole of the rotor 300 includes three recesses 131a, 131b, 131c, and the third recess 131c extends transversely to the radius of the rotor 300 and is spaced apart from the recesses 131a, 131b, 131c in the radial direction of the rotor 300.

[0071] Figure 5 The shape of the plate 33 is shown. The plate 33 differs from the plate 34 in that the recesses 31a, 31b are through recesses, that is, they extend to the edge of the plate forming the cylindrical surface of the rotor, dividing each plate 33 into a central part 33a, an intermediate part 33b and a peripheral part 33c. The parts 33b and 33c together with the central part 33a define the contours of the recesses 31a and 31b. In the assembled structure of the rotor, the recesses 31a, 31b freely form a through space leading to the cylindrical outer wall of the rotor 3. Figure 3 In the arrangement of plates 33 , 34 shown, recesses 31 a and 31 b extend only over one or more parts of the length (along longitudinal axis X) of rotor 3 .

[0072] According to an exemplary embodiment, the stator 2 may have an outer diameter of 40.7 mm, an inner diameter of 21.8 mm, and a length of 15 mm. The rotor 3 may have a diameter of 21.2 mm and a length of 20 mm.

[0073] Preferably, the iron Lfer and the length of the air gap are set to Lfer = 15 mm and e = 0.3 mm, corresponding to conventional dimensions in electromechanical actuator applications for actuating blinds or roller shutters. Under these conditions, the parameters Rb1, Rb2, Rfer and Lb of the rotor can take the values ​​listed in Table 1 below:

[0074] Table 1

[0075] LB(mm) Rbb(mm) Rba(mm) Rfer(mm) 0.5 to 1.5 7.8 to 10 6 to 8.2 7 to 8.6

[0076] These values ​​are obtained with 715 turns of wire of 0.15 mm diameter and with plates 33, 34 0.5 mm thick, applying sinusoidal control to the motor 1a, the average torque obtained on the shaft of the motor 1a being between 32 and 35 mN.m.

[0077] By reducing the effects of magnetic shunting, particularly by reducing the thickness of the sheet 34, torque performance may be improved.

[0078] Similarly, the presence of two recesses per pole forming a flux barrier makes it possible to limit torque ripple, compared to a structure having a single recess per pole forming a flux barrier.

[0079] However, acoustically, the motor 1a has a noise spectrum including a peak at about 2kHz, which is within the spectrum audible to the human ear. However, the dominance of the noise peak at this frequency proves to be annoying to the human ear, with the perception of a high-pitched noise.

[0080] Figure 6 A plate 34' of a rotor 3' of a motor 1b according to one embodiment is represented. Motor 1b differs from motor 1a only in its rotor 3'. The rotor 3' of motor 1b differs from the rotor 3 in that the plates 33', 34' have notches 35 distributed on their edges. The notches 35 can be defined, for example, by their angular position Na and their radius NR. The angular position Na is defined relative to the median plane 10 of the recesses 31a, 31b, which includes the longitudinal axis X of the rotor 3'. Once stacked and assembled, the notches 35 on the edges of the plates 33', 34' form a groove extending longitudinally along the rotor 3'.

[0081] According to one embodiment, the angular position Na of the notch 35 is between 0° and 35°, and the radius NR of the notch 35 is between 0.4 mm and 1.8 mm. When the notch 35 has an angular position Na of 20° and a radius NR of 0.7 mm, it can be observed that the audible noise peak is attenuated by 24 dBA, whether the motor 1b is unloaded or loaded, compared to the motor 1a without the notch.

[0082] Figure 7A motor 1c according to another embodiment is shown. The motor 1c differs from the motor 1b only in its rotor 3″. Figure 7 The rotor 3" shown differs from the rotor 3' in that the plates 33', 34' are replaced by plates 33", 34". The plates 33", 34" differ from the plates 33', 34' in that they each comprise a second recess 35' arranged symmetrically to the recess 35 relative to the mid-plane 10 of each of the recesses 31a, 31b. This arrangement does not significantly change the amplitude of the audible noise peaks, but has the advantage of making the behavior of the motor 1b symmetrical (in particular in terms of noise) according to the two directions of rotation of the motor.

[0083] Figure 8 , Fig. 8A A motor 1d according to another embodiment is shown. The motor 1d is equipped with a rotor 3' and a stator 2', the rotor having plates 33', 34' with a notch 35 per pole. The stator 2' differs from the stator 2 in that, in each plate forming the stator, each tooth 21 includes a notch 25. Each tooth 21 of each plate forming the stator 2' includes one of the notches 25. Each notch 25 extends from the free end of one of the teeth 21 and is located at the center of the free end. Thus, the notch 25 forms a groove extending longitudinally in the tooth 21 of the stator 2'. Fig. 8A In FIG. 2 , each of the notches 25 is defined by its width SW and depth SD in one of the teeth 21 .

[0084] According to one embodiment, the recess 25 has a width SW of 0.2 to 3 mm and a depth SD of 0.2 to 6 mm.

[0085] By combining a notch 35 having an angular position Na of 25° and a radius NR of 1.25 mm and a notch 25 having a width SW of 0.5 mm and a depth SD of 1 mm, the audible noise peak is attenuated by 15 dBA compared to a motor 1 without the notch, whether the motor is unloaded or loaded.

[0086] Fig.11 5 shows an electromechanical actuator 50 according to one embodiment. The actuator 50 comprises: a motor 56, which may be one of the motors 1a, 1b, 1c, 1d described previously; a reducer 57, which is coupled to the output shaft of the motor; and a control unit 55, which is connected to the motor 56, in particular to supply electrical energy to the motor and drive the motor according to control commands. The reducer 57 comprises an output shaft 58 forming the output shaft of the actuator 50. The motor 56, the reducer 57, the output shaft 58 and the control unit 55 may be coaxially housed around an axis A in a cylindrical housing 52, the inner diameter of which corresponds to the outer diameter of the stator of the motor 56. The reducer 57 may comprise a planetary reducer and / or a mechanical or electromagnetic brake.

[0087] Thus, the actuator 50 can be arranged, for example, in a winding tube 60 of a shading device, such as a roller blind or a shutter. For this purpose, the output shaft 58 of the actuator 50 is coupled to the winding tube 60 via a mechanical link 59. In addition, the head 54 of the actuator 50 is fastened to a fixed structure 61. The actuator 50 also includes a bearing crown 63, which is mounted on the housing 52 and can rotate freely relative to the housing. The bearing crown 63 is rotatably fastened to the winding tube 60, so that the bearing crown 63 provides a rotational bearing function for the winding tube 60 on the housing 52 and / or on the head 54 on the control unit 55 side, and the output shaft 58 provides a mechanical connection between the actuator and the winding tube 60 via a mechanical link 59 on the other side.

[0088] The electromechanical actuator 50 is supplied with electrical energy by the building's power supply network, for example by an AC grid or a DC bus, or even by means of batteries (not shown) which can be recharged, for example, by photovoltaic panels. Here, the electromechanical actuator 11 comprises a supply cable 62 connected to the mains power supply network.

[0089] Fig.12 : represents a home automation device according to one embodiment. The home automation device can be installed in a building comprising an opening, a window or a door, which is equipped with a screen 72 belonging to a screening device 70, in particular a motorized roller blind. The screening device 70 can alternatively be a roller blind, a shutter with adjustable slats or even a rolling door. In practice, the invention applies to all types of screening devices comprising a rotating motorized winding shaft.

[0090] The shielding member 72 of the shielding device 70 is wound on a winding tube, such as the winding tube 60 driven by the electromechanical actuator 50. The shielding member 72 is movable between a wound position, in particular a high position, and an unfolded position, in particular a low position.

[0091] In a known manner, the shield 72 of the shielding device 70 is formed by a canvas, the first end of which is attached to a winding tube and the other end is attached to a weighted rod 73. The high winding position of the shield corresponds to the position of the weighted rod at the winding tube 60, and the low unfolded position corresponds to the position of the weighted rod 73 of the shield 72 at the bottom of the opening. The unfolding of the shield 72 can be guided by a slide 71. The winding tube 60 can be arranged inside the box 74 or can be visible. The winding tube 60 can be rotatably moved relative to the support (such as cheek plate) of the box 74.

[0092] It will be clear to those skilled in the art that the invention can have various modifications and various applications. In particular, the invention is not limited to actuators for roller blinds and shutters. It is more generally applicable to cylindrical actuators with a power less than or equal to 300W.

[0093] Furthermore, the number of poles of the rotor and the number of teeth of the stator may take other values ​​without departing from the scope of the present description. If the motor is controlled by three phases, it is very important that the number of teeth of the stator is a multiple of three.

[0094] The angle Na of the notches 35, 35' is not necessarily the same from one plate 33', 33", 34', 34" to another, so that the groove formed by the notches 35, 35' is not necessarily parallel to the axis X of the rotor, or even necessarily rectilinear. In addition, not all plates 33', 33", 34', 34" must be provided with notches 35 and / or 35', so that the grooves on the rotor can be discontinuous or not extend along the entire length of the rotor. Thus, for example, only the plates 33', 33" can be provided with notches 35, 35'.

[0095] The groove formed by the notches is not necessarily symmetrical with respect to the mid-plane of the poles passing through the longitudinal axis X of the rotor. In practice, it may not be necessary to make the behavior of the motor symmetrical in both directions of rotation, especially in applications where the motor is used in only one direction of rotation.

[0096] The grooves 25 formed in the stator 2 'are not necessarily located in the center of the teeth 21. In fact, the eccentric position of the grooves 25 makes it possible to reduce the audible noise peaks of the motor. In addition, the motor can include these stator grooves without having grooves on the rotor. In fact, such an arrangement also makes it possible to reduce the audible noise peaks.

Claims

1. An electromechanical actuator for actuating a shading device, such as a roller blind or a shutter, comprising a housing (52), a head (54) intended to be fastened to a fixed structure (61), a synchronous motor (1a, 1b, 1c, 1d, 56), a reducer (57) and a motor control unit (55), the motor (1a, 1b, 1c, 1d, 56), the reducer (57) and the control unit (55) being inserted into the housing (52) of the electromechanical actuator, the motor comprising: Cylindrical rotor (3, 3', 3"), a cylindrical stator (2, 2') coaxially arranged around the rotor and comprising a plurality of teeth (21) extending radially towards the rotor, and a coil (11) forming a winding around each of the teeth of the stator, Features: The stator (2, 2') has an outer diameter of less than 55 mm, The rotor (2, 2') is formed from an assembly of metal sheet plates, The rotor (3, 3', 3") comprises recesses (31a, 31b) around the longitudinal axis of the rotor, the rotor (3, 3', 3") comprising an arrangement of recesses forming four magnetic poles, each magnetic pole of the rotor comprising two or three recesses (31a, 31b, 31c), the recesses being formed around the longitudinal axis of the rotor and extending to the cylindrical surface of the rotor.

2. The actuator according to claim 1, wherein: The stator (2, 2') comprises six teeth.

3. The actuator according to any one of claims 1 and 2, wherein: The rotor (3', 3") comprises a first rotor groove (35) extending on a cylindrical surface of the rotor facing each of the poles, the first rotor groove being centred on a line outside a first median plane of the pole passing through the longitudinal axis of the rotor.

4. The actuator according to claim 3, wherein: The rotor (3") comprises a second rotor groove (35') extending on a cylindrical surface of the rotor facing each of the magnetic poles.

5. The actuator according to claim 4, wherein: The first rotor groove and the second rotor groove (35, 35') are arranged symmetrically with respect to the first plane.

6. The actuator according to claim 4 or 5, wherein: The first rotor groove or the second rotor groove (35, 35') or each of the first rotor groove and the second rotor groove has at least one of the following features: an angular position (Na) between 0° and 35° about the longitudinal axis of the rotor relative to the first plane, semicircular segments, and Semicircular segment with a radius (NR) between 0.4 and 1.8 mm.

7. The actuator according to any one of claims 1 to 6, wherein: Each tooth (21) of the stator (2') comprises a stator groove (25) formed in a free end of the tooth.

8. The actuator according to claim 7, wherein: The stator groove (25) formed in each tooth (21) of the stator (2') has at least one of the following features: The stator groove is located centrally in a second median plane of the tooth passing through the longitudinal axis of the stator, The stator groove has a width (SW) of 0.2 to 3 mm, and The stator groove has a depth (SD) of 0.2 to 6 mm.

9. The actuator according to any one of claims 1 to 8, wherein: The actuator is powered by an AC power grid.

10. The actuator according to claim 9, wherein: The control unit (55) applies sinusoidal or trapezoidal control to the motor.

11. An actuator according to any one of claims 1 to 10, wherein: The stator (2, 2') is formed from an assembly of metal sheet plates.

12. An actuator according to any one of claims 1 to 11, wherein: The motor (1a, 1b, 1c, 1d, 56) has a power less than or equal to 300W.

13. An actuator according to any one of claims 1 to 12, wherein: The thickness of the sheet forming the rotor is between 0.3 and 0.7 mm, preferably 0.5 mm.

14. A rolling blind or shutter type screening arrangement comprising an actuator according to any one of claims 1 to 13.

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