FR3152198A1 - Improved axial flux electric motor - Google Patents

Abstract

Improved axial flux electric motor An axial flux electric motor (1) extending about a central axis (X) and comprising a stator (20) having electrical windings (24) and a rotor (10) arranged axially adjacent to the stator (20) and being rotatable about the central axis (X), the rotor (10) comprising at least one rotor disk (12) comprising magnets (14) and ferromagnetic parts (13) distributed circumferentially about the central axis (X), each ferromagnetic part (13) being arranged between two adjacent magnets (14), the rotor disk (12) comprising at least one concave axial face (121, 122) such that a thickness of the rotor disk (12) at an internal diameter (Di) of the rotor disk is smaller than a thickness of the rotor disk (12) at an external diameter (De). Figure for abstract: Fig. 6.

Description

Improved axial flux electric motor

This disclosure relates to the field of electric motors, in particular electromagnetic motors, used in aircraft turbomachines, but not only. In particular, this disclosure relates to an axial flux electric motor, and a smart motor comprising such an electric motor.

As is known, an electric motor comprises a fixed part (the stator) and a mobile part rotating around a central axis (the rotor). The rotor may comprise magnets, and the stator comprises a winding of electric wires which, supplied by an electric current, produces a magnetic field. In a synchronous electric motor, the interaction of the field of the rotor magnets in quadrature with the stator currents allows the creation of an electromagnetic torque, which can then drive the rotation of the rotor. The rotation of the rotor can then generate the rotation of a machine component, for example a propeller.

Unlike a radial flux motor, in which a cylindrical rotor rotates inside an annular stator (or conversely, an annular rotor rotates around a cylindrical stator), generating a radial magnetic flux perpendicular to the central axis of rotation, an axial flux motor involves at least one stator and one rotor axially facing each other, and therefore a magnetic flux axial and parallel to the central axis of rotation.

Typically, an axial flux motor may comprise a stator disk sandwiched between two rotor disks, a plane air gap existing between these different disks. However, other configurations are possible, in particular a rotor disk sandwiched between two stator disks, a rotor disk and a stator disk alone, facing each other, or a multi-rotor arrangement, comprising for example three rotor disks and two stator disks, each stator disk being interposed between two successive rotor disks.

Axial flux electric motors offer a number of advantages over radial flux electric motors, including better performance in terms of power density and torque density. In particular, the rotor disc, not being radially limited by the stator, can have a large diameter, which allows for increased torque and therefore performance of the axial flux motor, compared to the radial flux motor. However, axial flux electric motors also have disadvantages.

In particular, the increase in torque through an increase in rotor diameter implies a significant amount of material to mechanically hold the active electromagnetic parts of the motor, which requires greater resources and costs. Larger rotor diameters also result in increased rotational inertia, uneven distribution of the magnetic flux, and more difficult or even impossible integration into compact machines. Furthermore, the rotors of axial flux electric motors contain magnets, but generally little or no iron, unlike the rotors of modern radial flux electric motors, which does not allow for optimized torque-to-weight ratio performance.

There is therefore a need for a system to at least partially overcome the aforementioned drawbacks and to improve the performance of axial flux electric motors.

The present disclosure relates to an axial flux electric motor extending about a central axis and comprising a stator having electrical windings and a rotor arranged axially adjacent to the stator and being rotatable about the central axis, the rotor comprising at least one rotor disk comprising magnets and ferromagnetic parts distributed circumferentially about the central axis, each ferromagnetic part being arranged between two adjacent magnets, the rotor disk comprising at least one concave axial face such that a thickness of the rotor disk at an inner diameter of the rotor disk is less than a thickness of the rotor disk at an outer diameter.

In this disclosure, the terms “axial direction”, “radial direction” and their derivatives are defined relative to the central axis of the electric motor, which is also the axis of rotation of the rotor around which the latter rotates. Typically, the rotor disk is integral with a rotating shaft, and extends radially between its radially inner end fixed to said rotating shaft, and its radially outer end. Furthermore, it is understood that the thickness of the rotor disk corresponds to its thickness in the axial direction, i.e. along the central axis.

As is known, the stator comprises a ferromagnetic circuit with slots housing electrical windings, typically made of copper wires. The rotor disk comprises magnets, typically permanent magnets, each magnet extending radially between the radially inner end and the radially outer end, i.e. between the inner diameter of the rotor disk and the outer diameter. The magnets are distributed, preferably at regular intervals, around the central axis.

The rotor disk further comprises ferromagnetic parts, which are not permanent magnets, but comprise iron and may further comprise nickel and cobalt. Thus, the magnetic flux generated by two adjacent magnets can be deflected to a ferromagnetic part, which then itself acts as a magnet. The rotor disk may also comprise a ferromagnetic yoke carrying the magnets, such that a ferromagnetic portion is arranged between the adjacent magnets.

By “each ferromagnetic part being arranged between two adjacent magnets”, it is understood that, when a space exists between two adjacent magnets, a ferromagnetic part is interposed between these two magnets. More precisely, the rotor disk can comprise a plurality of ferromagnetic parts, each being formed so as to house therein a magnet which matches the shape of the ferromagnetic part. The magnet can perfectly match the shape of the ferromagnetic part, or have local deformations to insert non-magnetic holding elements such as glue or a polymer matrix.

According to the disclosure, the fact that the rotor disk comprises a concave axial face leading to a lower thickness of the rotor disk at the inner diameter than at the outer diameter, implies that the magnets of the rotor disk can themselves have a greater thickness near the radially outer end. This geometry implies a three-dimensional effect which allows to maintain a constant or nearly constant level of magnetic flux concentration in the air gap between the rotor and the stator, along the radius of the rotor disk in the radial direction.

Thus, for a given rotor diameter, this geometry allows, compared to a flat rotor geometry without a concave axial face and therefore with a constant rotor thickness, to increase the magnetic field in the air gap, to increase the motor torque and consequently the specific torque and the specific power of the motor. It is thus possible to improve the performance of the electric motor for a given diameter, which allows the use of more compact electric motors, which can be integrated more easily into machines that are themselves more compact.

In some embodiments, the concave axial face of the rotor disk has the shape of a portion of a cone.

In other words, in a section in a plane parallel to the central axis, the thickness of the rotor disk is linearly increasing from the radially inner end to the radially outer end. It is thus possible to more effectively maintain a constant level of magnetic flux concentration in the air gap between the rotor and the stator.

In some embodiments, each magnet has a flared shape, having a linearly increasing section from the inner diameter to the outer diameter.

It is understood that each magnet is flared so as to follow the general shape of the rotor disk, and in particular its concave axial face. It is further understood that the section considered is a section in a plane perpendicular to the radial direction. Thus, in such a plane, the section of the magnet increases linearly from the radially inner end to the radially outer end. Consequently, the space or housing existing between two adjacent magnets, which widen identically from each other radially outwards, can remain substantially constant over the entire radius of the rotor disk, thus maintaining even more effectively a constant level of magnetic flux concentration in the air gap between the rotor and the stator.

In some embodiments, each magnet has a circular, oblong, or polygonal radial cross-section.

It is understood that a magnet of circular section is a magnet having a truncated cone shape, widening from the radially internal end towards the radially external end. Similarly, a magnet of polygonal section is a magnet having a pyramidal shape, for example with a square base.

In some embodiments, the stator comprises at least one stator disk, an axial face of the stator disk, facing the concave axial face of the rotor disk, being convex and of complementary shape to the concave axial face of the rotor disk, such that an air gap between the concave axial face of the rotor disk and the convex axial face of the stator disk has a constant thickness.

When the concave axial face of the rotor disk is conical, for example, the convex axial face of the stator disk is also conical with a shape complementary to the concave axial face of the rotor disk, such that said convex axial face of the stator disk is housed in the open cavity formed by the concave axial face of the rotor disk and matches the shape of the latter. The air gap, i.e. the space between the axial face of the rotor disk and the axial face of the stator disk, is thus constant, which makes it possible to maintain a constant level of magnetic flux concentration in said air gap and to further improve the performance of the electric motor.

In some embodiments, the concave axial face of the rotor disk is a first axial face, and the stator disk is a first stator disk, the rotor disk comprising a second concave axial face opposite the first axial face, and the stator comprising a second stator disk, an axial face of the second stator disk, opposite the second concave axial face of the rotor disk, being convex and of complementary shape to the second concave axial face of the rotor disk, such that an air gap between the second concave axial face of the rotor disk and the convex axial face of the second stator disk has a constant thickness.

It is understood that according to this embodiment, the rotor disk is sandwiched between two stator disks. The rotor disk thus comprises two axial faces axially opposite one another, each of them being concave so as to accommodate the convex axial face of the first stator disk, and the convex axial face of the second stator disk respectively. The arrangement according to the present disclosure thus makes it possible to improve the performance of an electric motor having such an architecture.

In some embodiments, the stator comprises a single stator disk having two planar axial faces, the rotor disk is a first rotor disk, the rotor comprising a second rotor disk having a concave axial face, the first rotor disk and the second rotor disk each further having a planar axial face, opposite the concave axial face, facing one of the planar axial faces of the stator disk.

It is understood that according to this embodiment, the stator disk is sandwiched between two rotor disks. The stator disk thus comprises two axial faces axially opposite one another, each of them being flat and facing the flat axial face of the first and second rotor disks respectively, so as to thus form a flat and constant air gap on either side of the stator. The opposite axial face of the first and second rotor disks is concave, which makes it possible to obtain the aforementioned effects related to the concentration of magnetic fluxes. The arrangement according to the present disclosure thus makes it possible to improve the performance of an electric motor having such an architecture.

In some embodiments, the rotor disk includes a holding die capable of holding the magnets and ferromagnetic parts in position.

The holding matrix is preferably non-magnetic. Alternatively, it could be ferromagnetic and of thin thickness to limit flux leakage inside the rotor. The holding matrix acts as a mechanical support for the ferromagnetic parts and the magnets, and can be for example, but not limited to, made of polymer material, aluminum, or honeycomb-shaped.

In some embodiments, a distance between two adjacent magnets is zero or constant from the inner diameter to the outer diameter.

It is understood that adjacent magnets may be in contact with each other over their entire radial length, from the radially inner end to the radially outer end, or be slightly spaced apart from each other by, for example, a distance of less than 5 mm, the spacing being constant over their entire radial length. This makes it possible to maintain even more effectively a constant magnetic flux concentration over the entire radius of the rotor disk.

In some embodiments, the rotor disk is formed such that the relationship E2=E1*(De/Di) is satisfied, where E1 and E2 are the thicknesses of the rotor disk at the inner and outer diameter respectively.

The rotor disk geometry thus defined makes it possible to improve the maintenance of a constant level of magnetic flux concentration in the air gap and to further improve the performance of the electric motor.

In some embodiments, the magnets are arranged about the central axis such that the polarities of at least two adjacent magnets are oriented differently from each other, such as to alternate the orientation of the magnetic fluxes induced between said adjacent magnets.

Two adjacent magnets arranged so that their polarities are opposite each other allows their magnetic fluxes to be directed towards the ferromagnetic part in contact with these adjacent magnets, and thus to concentrate the magnetic fluxes in said ferromagnetic part. This arrangement, combined with the concave shape of the rotor disk, allows the aforementioned effects of concentrating the magnetic fluxes in the air gap to be further improved, and therefore the performance of the electric motor.

The present disclosure also relates to an intelligent motor comprising at least one electric power module comprising an electric motor according to any one of the preceding embodiments, and two electronic control units arranged on either side of the electric motor.

Smart motors include their own control electronics and have a generally parallelepiped shape. The electric motor defined above is more compact thanks to the concave shape of its rotor disk, which allows for easier integration into such a smart motor.

The invention and its advantages will be better understood upon reading the detailed description given below of different embodiments of the invention given as non-limiting examples. This description refers to the appended pages of figures, in which:

FIG. 1 There FIG. 1 schematically represents in perspective different architectures of axial flux electric motors according to the prior art,

FIG. 2 There FIG. 2 schematically represents in perspective an axial flux electric motor according to the prior art, and a partial radial sectional view, along a curved sectional plane, of said electric motor,

FIG. 3 There FIG. 3 represents a front view of a rotor disk of the engine of the FIG. 1 ,

FIG. 4 There FIG. 4 represents a radial sectional view of an axial flux electric motor according to the prior art at the level of the internal diameter (left) and the external diameter (right),

FIG. 5 There FIG. 5 schematically represents in perspective an exploded view of an axial flux electric motor according to a first embodiment of the invention,

FIG. 6 There FIG. 6 schematically represents an axial sectional view of the electric motor of the FIG. 5 ,

FIG. 7 There FIG. 7 represents a radial sectional view of the electric motor of the FIG. 5 at the internal diameter (left) and external diameter (right),

FIG. 8 There FIG. 8 represents in perspective different examples of rotor magnets of the motor according to the invention,

FIG. 9 There FIG. 9 schematically represents the dimensions of the rotor disk of the motor according to the invention, in an axial sectional view of the rotor disk,

FIG. 10 There FIG. 10 represents a radial sectional view of a rotor disk according to a modified example of the first embodiment of the invention,

FIG. 11 There FIG. 11 schematically represents different examples of shapes and arrangements of magnets of an electric motor rotor according to the invention,

FIG. 12 There FIG. 12 schematically represents an axial sectional view of an axial flux electric motor according to a second embodiment of the invention,

FIG. 13 There FIG. 13 schematically represents an intelligent motor comprising an axial flux electric motor according to the invention,

FIG. 14 There FIG. 14 represents different examples of arrangements of the intelligent engine of the FIG. 13 .

In the remainder of the description, the terms “axial direction”, “radial direction” and their derivatives are defined in relation to the central axis X of the electric motor 1, 1’, which is also the axis of rotation of the rotor around which the latter turns.

Figures 1 to 3 represent axial flux electric motors 1’ according to the prior art.

There FIG. 1 depicts various examples of axial flux electric motor architectures 1' (hereinafter simply referred to as "motor 1'"). A motor 1' comprises a rotor 10 and a stator 20, each comprising one or more rotor and stator disks respectively.

In example a) of the FIG. 1 , the rotor 10 comprises a single rotor disk 12, and the stator 20 comprises a single stator disk 22 arranged axially facing the rotor disk 12. In particular, an axial face 121 of the rotor disk 12 faces an axial face 221 of the stator disk 22.

On example b) of the FIG. 1 , the stator 20 comprises a single stator disk 22, and the rotor 10 comprises two rotor disks 12a and 12b arranged axially on either side of the stator disk 22.

In example c) of the FIG. 1 , the rotor 10 comprises a single rotor disk 12, and the stator 20 comprises two stator disks 22a and 22b arranged axially on either side of the rotor disk 12.

On example d) of the FIG. 1 , the rotor 10 comprises three rotor disks 12a, 12b, 12c, and the stator 20 comprises two stator disks 22a and 22b. The first stator disk 22a is axially disposed between the first rotor disk 12a and the second rotor disk 12b, and the second stator disk 22b is axially disposed between the second rotor disk 12b and the third rotor disk 12c.

Whatever the architecture of the motor 1', the stator comprises a plurality of notches 23 housing electrical windings 24 (not shown in the FIG. 1 ), typically made of copper wires. The rotor 10 comprises permanent magnets 14 (hereinafter simply referred to as “magnets 14”) each extending radially between the radially inner end, corresponding to the inner diameter Di of the rotor disk 12 and the radially outer end, corresponding to the outer diameter De, as illustrated in the FIG. 3 representing a front view, parallel to the central axis X, of a rotor disk 12 alone. The magnets 14 are distributed, preferably at regular intervals, on the first axial face 121 and/or the second axial face 122 of the rotor disk 12 around the central axis X. It will be noted that the magnets 14 do not necessarily extend from the inner end Di to the outer end De, but extend radially between these ends, a portion of the material 13 carrying the magnets 14 extending radially above and below the magnets 14.

There FIG. 2 on the left is an exploded schematic and perspective view of an engine 1' according to the arrangement example c) of the FIG. 1 . The image on the right of the FIG. 2 represents a partial radial section of the engine 1' of the left image. This radial section is taken in a cutting plane P, which is a curved plane following the radius of curvature of the disks 12, 22a, 22b and being arranged at a given radial position along the radius of the engine 1'. The plane P, marked in dotted lines on the FIG. 2 , extends on the one hand axially, and on the other hand circumferentially around the central axis X, over a portion of the circumference of the motor 1'. In the remainder of the description, by "radial section" is meant a section taken in a curved section plane corresponding to the definition above, at a given position along the radius of the motor 1'.

In this example, the rotor disk 12 comprises a non-magnetic material 13, supporting and holding in position the magnets 14. The first axial face 121 of the rotor disk 12 is axially facing the axial face 221 of the stator disk 22b, so as to form an air gap E between the rotor disk 12 and the stator disk 22b. Similarly, the second axial face 122 of the rotor disk 12 is axially facing the axial face 222 of the stator disk 22a, so as to form an equivalent air gap between the rotor disk 12 and the stator disk 22a.

The arrows on the magnets 14 represent the polar orientation of each of the magnets 14. The alternating orientation of the magnets makes it possible to create, with the electrical windings 24 of the stator 20, lines of magnetic flux between the rotor 10 and the stator 20. It will be noted that by convention, on the FIG. 2 and the following, the magnets 14 oriented in a given direction are shown hatched, and the magnets 14 oriented in the opposite direction are not hatched.

There FIG. 4 represents, on the left, a radial section taken near the radially internal diameter Di of a motor 1' according to the prior art, and on the right, a radial section taken near the radially external diameter De of this same motor 1'. It will be noted that this example, corresponding to the architecture c) described above, differs from the previous example in that the rotor disk 12 comprises ferromagnetic parts 13 arranged alternately with the magnets 14, and which make it possible to conduct or concentrate the magnetic flux towards the stator, more precisely towards the stator disks 22a, 22b. Each ferromagnetic part 13 is formed and arranged so as to be in contact with two adjacent magnets 14, by matching the shape of these magnets (by means of the presence of a mechanical element such as glue, not shown).

Given the shape of a disk, the notches 23, close to each other near the internal diameter Di, gradually move away from each other as one moves away from the central axis X radially outwards. Thus, near the external diameter De, the notches 23, and consequently the windings 24, are further away from each other and less densely distributed than near the internal diameter Di, as illustrated in the FIG. 4 .

Similarly, the magnets 14, close to, or even in contact with each other near the internal diameter Di, tend to move away from each other as they approach the external diameter De. Conversely, the width L of the ferromagnetic parts 13, due to the spacing between two adjacent magnets 14, tends to increase.

Consequently, the curvilinear length c of the output (or input depending on the orientation of the magnets) of the field at the adjacent magnets 14, whose polarity direction is reversed, becomes smaller than the width L of the ferromagnetic part 13 on the side of the air gap F. The curvilinear length c is shown in bold lines on the FIG. 4 , and the field lines are shown in broken lines. Thus, the concentration of the magnetic flux directed by two adjacent magnets 14 towards the ferromagnetic part 13, which itself directs this flux towards the air gap F, tends to decrease as one moves away radially towards the outside.

Furthermore, increasing the width of the magnets 14 by approaching the external diameter De would imply a reduction in the width L of the ferromagnetic part 13, and therefore a reduction in the interaction effect with the stator field, the windings 24 themselves being further away from each other near the external diameter De.

The engine 1 according to the invention, described with reference to FIGS. 5 to 14, makes it possible to overcome these drawbacks at least in part.

There FIG. 5 schematically represents an exploded perspective view of an axial flux motor 1 according to a first embodiment, corresponding to the architecture c) of the FIG. 1 . There FIG. 6 schematically represents a sectional view of the engine 1, in a sectional plane parallel to the central axis X and including the central axis X.

The motor 1 of the invention differs from the motor 1' of the prior art in particular in that the axial faces of the rotor disk 12 are not flat, but are concave, in this example concave conical. More precisely, in this embodiment applied to architecture c), the rotor disk 12 comprises a first concave conical axial face 121, and a second concave conical axial face 122.

Therefore, the thickness of the rotor disk 12 in the axial direction increases, in particular increases linearly, from the inner diameter Di to the outer diameter De. In particular, a thickness E1 of the rotor disk 12 at the inner diameter Di is smaller than a thickness E2 of the rotor disk 12 at the outer diameter De ( FIG. 7 ).

Furthermore, each of the first and second stator disks 22a, 22b comprises a convex conical axial face 221, 222, the axial faces 221, 222 being arranged opposite the axial faces 121, 122 respectively of the rotor disk 12. The convex conical axial faces 221, 222 of the stator disks 22a, 22b are preferably of a shape complementary to the concave conical axial faces 121, 122 of the rotor disk 12, so that the stator disks 22a, 22b can easily fit into the rotor disk 12, and so that the air gaps thus formed on either side of the rotor disk 12 have a constant thickness over the entire surface of the disk.

It will be noted that, although the axial faces of the stator disks 22a, 22b, opposite the axial faces 221, 222, are concave on the FIG. 6 , this representation is not limiting, these axial faces can be flat without departing from the scope of the invention, the stator disks 22a, 22b being in this case thicker towards the internal diameter Di than towards the external diameter De.

The radially inner end Di of the rotor disk 12 may further be fixed to a non-magnetic mechanical wheel 40 secured to a hollow rotating shaft 30, coaxial with the central axis X. The rotating shaft 30 may be movable in rotation relative to the stator 20 by means of bearings 50 such as ball bearings. It will be noted that the electrical winding 24 is not shown in the FIG. 5 .

According to the invention, the magnets 14 have a flared shape, typically conical or truncated, from the internal diameter Di to the external diameter De, following the flared shape of the rotor disk 12. The FIG. 8 represents in perspective examples of magnets 14 alone of truncated cone shape, of circular section. This example is not limiting, the magnets 14 could have a different flared shape without departing from the scope of the invention, for example pyramidal of square section, or of oblong section.

Furthermore, the magnets 14 can be manufactured in different ways. For example, they can be solid as shown in example a) of the FIG. 8 , or segmented by being composed of a significant number of pieces of magnets isolated from each other and concatenated. In the example of figure b), the magnet 14 is segmented longitudinally into a plurality of longitudinal portions 141 of concatenated magnets, and in the example of figure c), the magnet 14 is segmented transversely into a plurality of transverse portions 142 of concatenated magnets. Alternatively, the magnets 14 can be segmented both longitudinally and transversely, that is to say a segmentation with a longitudinal component and a transverse component.

There FIG. 7 represents a radial section of the motor 1 near the internal diameter Di (on the left) or at the level of the internal diameter Di, and near the external diameter De (on the right) or at the level of the external diameter De. Given the flared shape of the rotor disk 12 and in particular of the magnets 14, a space between two adjacent magnets 14 remains constant, or even zero as illustrated in the FIG. 7 , from the internal diameter Di to the external diameter De.

In the radial sectional view of the FIG. 7 , the adjacent magnets 14 define a curvilinear contour c marked in bold on the FIG. 7 , creating an open housing in which a ferromagnetic part 13 is arranged, the latter thus filling said housing while being in contact with each of these two adjacent magnets 14. It will also be noted that in this radial sectional view, the face of the ferromagnetic part 13 delimiting the air gap F is flat.

Furthermore, the adjacent magnets 14 are oriented so that their polarities are opposite to each other. This makes it possible to direct their magnetic fluxes towards the ferromagnetic part 13 in contact with these adjacent magnets 14, and thus to concentrate the magnetic fluxes in said ferromagnetic part 13.

This arrangement makes it possible to create a substantially constant flux concentration from the internal diameter Di to the external diameter De. Indeed, the length of the curvilinear contour c of the magnetic field output at the adjacent magnets 14 is greater than the width L of the ferromagnetic part 13 on the side of the air gap F and this, over the entire radius of the rotor disk 12 between the internal diameter Di and the external diameter De. The magnetic field thus created by the ferromagnetic part 13, then acting itself as a magnet, is greater than the flux which would exit from a magnet 14 alone.

The concave conical shape of the rotor disk 12 allows an increase in the active length of the motor 1, including the magnets 14 and the ferromagnetic parts 13, compared to an axial flux motor with constant rotor thickness. This increase in the active length allows the torque performance of the motor to be increased by a factor of approximately 2 to 5%.

The geometric form factor of the rotor disk 12 can be defined by the geometric rules shown in the FIG. 9 . In particular, in order to maintain the level of concentration of the magnetic flux constant radially, the thickness E2 of the rotor disk 12 at the external diameter De is proportional to the thickness E1 of the rotor disk 12 at the internal diameter Di, by the factor of the ratio between the external diameter De and the internal diameter Di, in other words E2=E1*(De/Di).

ThereFIG. 10represents a radial section of an alternative example, in which the rotor disk 12 comprises a holding matrix 15 for mechanically holding the magnets 14 and the ferromagnetic parts 13 in position. The holding matrix 15 may be magnetic or non-magnetic. It will be noted that in the presence of such a matrix 15, the values E2 and E1 in the expression of the form factor of the previous paragraph, are increased by the value of the thickness of the holding matrix 15.

Furthermore, the shape and orientation of the magnets 14 shown in the FIG. 7 is not limiting, different arrangements of the magnets 14 allowing the concentration of the magnetic flux towards the ferromagnetic part 13, can be envisaged. For this purpose, the FIG. 11 shows different examples of shapes and arrangements of the magnets 14 in the rotor disk 12.

In particular, in examples a), c) and d), the magnets 14 have a circular or substantially circular section, the orientation of the magnets in example c) being different than in example a). In example b), the magnets 14 have an oblong section with curved ends, corresponding to the configuration of the FIG. 7 . In example e), the magnets 14 have a square section, and in example h), the magnets 14 have a rectangular section, the adjacent magnets in the latter example not being in contact with each other. In examples f) and g), the magnets 14 have a hexagonal section, the adjacent magnets being in contact with each other in example f), and not being in contact with each other in example g).

There FIG. 12 schematically represents a sectional view of the engine 1 according to an alternative example, corresponding to architecture b) of the FIG. 1 . In this configuration, the stator 20 comprises a single stator disk 22, and the rotor 10 comprises two rotor disks 12a, 12b arranged axially on either side of the stator disk 22.

The rotor disks 12a, 12b each comprise a flat axial face 120 facing a first axial face 221 and a second axial face 222, respectively, of the stator disk 22. An axial face 121, 122 of the first and second rotor disks 12a, 12b respectively, opposite the flat axial face 120, is concave conical.

This arrangement provides the same advantages as the arrangement corresponding to architecture c) described above.

In particular, whatever the architecture used, for a given torque, and assuming that the external diameter De is twice the internal diameter Di, the concave conical topology of the rotor disk 12 allows a reduction of at least 15%, or even at least 20%, for example 24%, of the total external diameter of the engine 1. The reduction in the external diameter of the engine 1 allows the latter, more compact, to be used in an intelligent parallelepiped-shaped engine, usually more suited to the form factor of aeronautical thermal engines.

There FIG. 13 schematically represents in perspective an intelligent motor 300 comprising an electric power module comprising a central portion 310 having an electric motor 1 as described previously, and two electronic control units 320 arranged on either side of the central portion 310.

Each electronic control unit 320 comprises an electronic part 321, and fins 322 for cooling the electronic part 321. An exchanger 340, comprising cooling oil, makes it possible to cool the electric motor 1 arranged in the central portion 310.

The intelligent motor 300 further comprises a main rotor 330 carrying blades 332, and being actuated by the electric motor 1 arranged in the central portion 310.

There FIG. 14 schematically represents in perspective different examples of intelligent motors 300 comprising an electric motor 1 as described above. Example a) corresponds to the configuration described above with reference to the FIG. 13 , wherein the smart engine 300 comprises a single electrical power module. In example b), the smart engine 300 comprises two electrical power modules, the two electrical power modules each being identical to the electrical power module described above with reference to the FIG. 13 . In example c), the smart engine 300 comprises three electrical power modules, the three electrical power modules each being identical to the electrical power module described above with reference to the FIG. 13

Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various illustrated/mentioned embodiments may be combined in additional embodiments. Therefore, the description and drawings are to be considered in an illustrative rather than restrictive sense.

Claims (12)

An axial flux electric motor (1) extending about a central axis (X) and comprising a stator (20) having electrical windings (24) and a rotor (10) arranged axially adjacent to the stator (20) and being rotatable about the central axis (X), the rotor (10) comprising at least one rotor disk (12) comprising magnets (14) and ferromagnetic parts (13) distributed circumferentially about the central axis (X), each ferromagnetic part (13) being arranged between two adjacent magnets (14), the rotor disk (12) comprising at least one concave axial face (121, 122) such that a thickness of the rotor disk (12) at an internal diameter (D _i ) of the rotor disk is smaller than a thickness of the rotor disk (12) at an external diameter (D _e ). Electric motor (1) according to claim 1, in which the concave axial face (121, 122) of the rotor disk (12) has the shape of a portion of a cone. Electric motor (1) according to claim 1 or 2, in which each magnet (14) has a flared shape, having a section linearly increasing from the internal diameter (D _i ) towards the external diameter (D _e ). Electric motor (1) according to any one of claims 1 to 3, in which each magnet has a circular, oblong or polygonal radial section. Electric motor (1) according to any one of claims 1 to 4, wherein the stator (20) comprises at least one stator disk (22a, 22b), an axial face (221, 222) of the stator disk (20), opposite the concave axial face (121, 122) of the rotor disk (12), being convex and of complementary shape to the concave axial face (121, 122) of the rotor disk (12), such that an air gap (F) between the concave axial face (121, 122) of the rotor disk (12) and the convex axial face (221, 222) of the stator disk (20) has a constant thickness. Electric motor (1) according to claim 5, wherein the concave axial face of the rotor disk (12) is a first axial face (121), and the stator disk is a first stator disk (22a), the rotor disk (12) comprising a second concave axial face (122) opposite the first axial face (121), and the stator (20) comprising a second stator disk (22b), an axial face (222) of the second stator disk (22b), opposite the second concave axial face (122) of the rotor disk (12), being convex and of complementary shape to the second concave axial face (122) of the rotor disk (12), such that an air gap between the second concave axial face (122) of the rotor disk (12) and the convex axial face (222) of the second stator disk (22b) has a constant thickness. Electric motor (1) according to claim 5, wherein the stator (20) comprises a single stator disk (22) having two flat axial faces (221, 222), the rotor disk is a first rotor disk (12a), the rotor (10) comprising a second rotor disk (12b) having a concave axial face (122), the first rotor disk (12a) and the second rotor disk (12b) each further having a flat axial face (120), opposite the concave axial face, facing one of the flat axial faces (221, 222) of the stator disk (22). Electric motor (1) according to any one of claims 1 to 7, wherein the rotor disk (12) comprises a holding die (15) capable of holding the magnets (14) and the ferromagnetic parts (13) in position. Electric motor (1) according to any one of claims 1 to 8, wherein a distance between two adjacent magnets (14) is zero or constant from the internal diameter (D _i ) to the external diameter (D _e ). An electric motor (1) according to any one of claims 1 to 9, wherein the rotor disc (12) is formed such that the relationship E2=E1*(De/Di) is satisfied, where E1 and E2 are the thicknesses of the rotor disc (12) at the inner (D _i ) and outer (D _e ) diameters respectively. Electric motor (1) according to any one of claims 1 to 10, wherein the magnets (14) are arranged around the central axis (X) in such a way that the polarities of at least two adjacent magnets (14) are oriented differently from each other, so as to alternate the orientation of the magnetic fluxes induced between said adjacent magnets (14). Intelligent motor (300) comprising at least one electric power module comprising an electric motor (1) according to any one of the preceding claims, and two electronic control units (320) arranged on either side of the electric motor (1).