Electromagnetic motor with magnetic flux concentration

Abstract

The invention relates to an electromagnetic motor (1) comprising an inner rotor (2) and an outer rotor (2a) which are concentric with respect to a central axis of rotation (3), wherein the rotors (2, 2a) interpose between them a stator (10) with an air gap (14, 14a) between the stator (10) and each rotor (2, 2a), each rotor (2, 2a) being provided with a magnetic circuit (8) for circulating magnetic flux opposite a respective air gap (14, 14a) and carrying magnets (6, 6a). The outer rotor (2a) carries surface magnets (6a) positioned in or on the associated magnetic circuit (8) flush with the magnetic circuit (8) towards the air gap (14, 14a) of the outer rotor (2a) with the stator (10). The inner rotor (2) carries magnets (6) arranged to perform a flux concentration by being buried and positioned radially in the magnetic circuit (8) of the inner rotor (2).

Description

[0001] DESCRIPTION

[0002] Title: Electromagnetic motor with magnetic flux concentration

[0003] The invention relates to an electromagnetic motor for driving a member arranged externally to the motor by at least partially surrounding it, in particular by integrating it into its interior, or by being attached to the motor, the motor having magnets on its rotor arranged to carry out a concentration of magnetic flux.

[0004] In a non-limiting embodiment of the present invention, the motor is housed in a wheel of a means of transport for propulsion of the means of transport, thereby forming what is called a wheel motor. In the case of a means of transport or vehicle provided with several wheels, such a motor may be installed in each wheel of the vehicle.

[0005] Such a motor for driving a member arranged externally to the motor, at least partially surrounding it or being attached to the motor, is particularly suitable for low speed and high torque applications in a restricted space requirement of a substantially discoid shape.

[0006] To do this, it is known to use an electromagnetic motor comprising a rotor carrying permanent magnets and a stator carrying windings, the stator and the rotor delimiting an air gap between them.

[0007] Such a single-air-gap motor, although of reduced size which is favorable to its installation in a member to be driven, has the major disadvantage of not delivering a high torque. Document FR 2 881 290 A1 describes an electric wheel or wheel motor comprising a motor incorporated in the wheel for its drive. The motor comprises a stator and a rotor connected to a torque transmission system in order to transmit a torque to the wheel.

[0008] In one embodiment, the rotor has two field generators or rotors each delimiting with the stator an air gap, each field generator or rotor comprising magnets with poles magnetized in a radial direction relative to an axis of rotation of the motor and magnetized yoke magnets each of which is placed between two adjacent pole magnets to strengthen the magnetic field formed by the pole magnets.

[0009] The presence of cylinder head magnets, however, reduces the space allocated to the pole magnets in the necessarily reduced size of the engine.

[0010] Documents EP 3 832 850 A1 and US 2019 / 190413 A1 describe an electromagnetic motor comprising an inner rotor and an outer rotor concentric with respect to a central axis of rotation. The rotors interpose between them a stator with an air gap between the stator and each rotor, each rotor being provided with a magnetic circuit for circulating magnetic flux opposite a respective air gap and carrying magnets.

[0011] For the outer rotor, surface magnets are positioned on the associated magnetic circuit by flush with the magnetic circuit towards the air gap of the outer rotor with the stator. For the inner rotor, magnets are arranged to carry out a flux concentration by being buried and positioned radially in the magnetic circuit of the inner rotor. In these documents, firstly the surface magnets are compact magnets, which is disadvantageous for the reduction of eddy currents and for the energy dissipation created during their use. Secondly, the surface magnets of the outer rotor are located on the magnetic circuit without penetrating into the magnetic circuit. At high rotational speed of the rotor, these magnets can become detached because they are insufficiently held on the outer rotor.Such positioning of the surface magnets on the magnetic circuit prevents the possibility of fragmenting the surface magnets into small magnets, which would be favorable to the reduction of eddy currents and the dissipation of the heat released in the magnets.

[0012] The problem underlying the present invention is to design an electromagnetic motor intended for driving an associated member with increased power density while remaining as compact as possible by a significant increase in the magnetic exchange surfaces compared to a motor according to the state of the art.

[0013] To this end, the present invention relates to an electromagnetic motor comprising an inner rotor and an outer rotor concentric with respect to a central axis of rotation, the rotors interposing between them a stator with an air gap between the stator and each rotor, each rotor being provided with a magnetic circuit for circulating magnetic flux opposite a respective air gap and carrying magnets, with, for the outer rotor, surface magnets positioned in or on the associated magnetic circuit by being flush with the magnetic circuit towards the air gap of the outer rotor with the stator and, for the inner rotor, magnets arranged to carry out a flux concentration by being buried and positioned radially in the magnetic circuit of the inner rotor, characterized in that the surface magnets of the outer rotor protrude from the magnetic circuit towards the respective air gap by being partially buried in the outer rotor,each surface magnet of the external rotor being segmented in at least two directions into a multitude of at least fifty pixelated unit magnets.,

[0014] By surface magnet is meant magnets protruding at least partially from the magnetic circuit. These surface magnets can be secured to the magnetic circuit by any means, in particular by gluing without penetrating the magnetic circuit.

[0015] In the context of the present invention, these surface magnets can be semi-buried in the magnetic circuit until they only protrude slightly from the magnetic circuit, therefore not completely buried on all sides by the magnetic circuit.

[0016] By magnets effecting flux concentration is meant magnets positioned radially in the rotor with orthoradial magnetization.

[0017] The superposition of the fluxes from the two magnets moving away from each other the closer the magnet parts are to the air gap creates a resultant flux at the air gap surface which can be greater than the simple flux created by a surface magnet.

[0018] This is partly explained by the fact that the sum of the magnet surfaces can be greater than the surface available for the installation of a surface magnet. Thus positioning the magnets by carrying out a flux concentration makes it possible to improve the power density in applications where compactness is a major issue, in the sense that we exploit an additional volume in the internal rotor compared to a motor with surface magnets.

[0019] Such a motor makes it possible to achieve a high volume torque in a reduced size, by better use of the allocated volume, hence a better power density.

[0020] In order to obtain a high volume torque, current densities of between 15 and 20 A / mm can be achieved. 2 Such a motor makes it possible to achieve a low air gap value, currently limited to 0.8 millimeters.

[0021] When a motor has a high number of pole pairs, its architecture generally has a large internal bore diameter, resulting in a large air gap diameter conducive to torque generation. This observation is valid whether the motor has an internal or external rotor.

[0022] One solution to be able to gain even more torque is to use this internal volume by switching to a double air gap architecture with a stator and two rotors, which is what the present invention recommends. By allowing the electromagnetic exchange surface to be increased by positioning, for example, both around an internal axis and on the periphery, we have the equivalent of "two motors in one". This makes it possible to increase the torque of the motor in the given space.

[0023] An architecture carrying out a flux concentration also presents a mechanical interest compared to an architecture with surface magnets, in particular with regard to the radial holding of the magnets, the magnets being buried and therefore solidly attached to the magnetic circuit and to the rotor carrying them.

[0024] It has been identified that a magnet motor carrying out a flux concentration on the internal rotor, in addition to presenting an increase in the volume torque compared to a conventional magnet motor, makes it possible to smooth out a torque ripple which may occur.

[0025] According to the prior art, it was understood that the magnets are cut into relatively long strips or bars. According to the present invention, pixelated magnets having smaller geometric surfaces are used, for example cubes, cylinders or polygonal shapes. Pixelated unit magnets are therefore in the form of small cross-sectional pads compared to conventionally segmented magnets.

[0026] Advantageously, the unit magnets are in the form of elongated pads with a circular, cylindrical, polygonal or ovoid section, the pads extending partially into a thickness of the external rotor.

[0027] By studs is meant elements of elongated shape not necessarily being of conical shape extending longitudinally in a thickness of the rotor thus carrying them radially in the rotor. Such studs can also be called rods.

[0028] A large magnet is subject to greater eddy current losses than its equivalent in small or micro-magnets. The use of small or micro-magnets therefore makes it possible to reduce these losses which are detrimental to the operation of the rotor.

[0029] Therefore, in each rotor, eddy current losses in the magnets have been considerably reduced by proposing ironless rotors or by proposing magnet poles consisting of a plurality of small unit magnets.

[0030] Considering a unit magnet as an elementary element in the form of a plot, the ideal shape of this plot is a symmetrical ellipsoid of revolution also called an ovoid shape, approximately a flattened sphere, which by its topology is difficult to demagnetize because its magnetic field relative to the magnetization is formless. There is no rotating field in the corners.

[0031] From this observation, it is advantageous to constitute a mesh of unit magnets which individually come as close as possible to the ellipsoid of revolution.

[0032] Several embodiments are possible and the ovoid shape of the unit magnet can be more or less perfect by having a convex rounded end portion at one longitudinal end or at both longitudinal ends.

[0033] A relatively perfect ovoid shape with two convex longitudinal ends is optimal but difficult to achieve by machining. On the other hand, it is the ideal shape to combat demagnetization of the unit magnet.

[0034] Alternatively, a unit magnet based on a poly-facet structure with a first portion called a body with longitudinal facets and at least one end portion with inclined facets whose angles are between 0 and 45° can also be envisaged, making it possible to increase the magnetic field relative to the magnetization while retaining significant active faces at the ends of the unit magnets in the form of pads. Between these two embodiments, many other shapes more or less approaching an ovoid shape are also possible.

[0035] Advantageously, a width of the magnets of the internal rotor increases with distance from the air gap of the internal rotor with the stator.

[0036] The variable magnet width effecting flux concentration allows for better creation of flux concentration in the case of a motor with a high number of pole pairs, which is frequently the case for an electromagnetic motor according to the present invention. Advantageously, the magnetic circuit of the inner rotor comprises a recess on an edge of the magnetic circuit opposite the air gap between the stator and the inner rotor. This recess or recessed area aims to increase the leakage reluctance in order to limit the leakage fluxes of the magnet and therefore to optimize the use of the magnet. Advantageously, the stator comprises an armature core carrying teeth having flanges at each of their longitudinal ends oriented towards a respective rotor, two adjacent teeth leaving between them a notch for a winding, the notch being narrowed by the flanges of the two adjacent teeth at each of their longitudinal ends.

[0037] Advantageously, the notches receive fractional pitch windings.

[0038] Advantageously, the motor comprises a hoop circumferentially covering the magnets of the external rotor. Such a hoop prevents the magnets from detaching from their associated rotor.

[0039] Advantageously, the masses of the magnets of the inner and outer rotors are respectively selected relative to each other so that the inner and outer rotors achieve an equivalent induction level. An equivalent induction level is a necessary condition for the correct dimensioning of the magnetic circuit of a motor in general.

[0040] Advantageously, the motor is radial flux, the external and internal rotors being respectively in the form of a crown perpendicular to the axis of rotation, each crown being extended by a cylindrical portion connected to the external edge of the crown and extending at a distance along the axis of rotation.

[0041] Advantageously, the rotors are mechanically connected to each other by a connecting piece relative to the plane orthogonal to the axis of rotation.

[0042] From a theoretical point of view, a mechanical connection by connecting piece is not necessary but in practice it greatly simplifies the stability of the motor by making it impossible for a rotor to come loose.

[0043] The invention also relates to a member driven by such a motor, the member being arranged external to the motor, at least partially surrounding it or being placed against the motor.

[0044] Advantageously, the member is a wheel driven in rotation by said motor, the wheel housing the motor inside it.

[0045] The invention finally relates to a means of transport comprising at least one such member in the form of a wheel driven in rotation by said motor, the means of transport having a means of suspending the wheel while leaving the wheel free to rotate.

[0046] The accompanying drawings illustrate the invention:

[0047] [Fig 1] represents a sectional view of a portion of an electromagnetic motor with a stator interposed between two rotors, the outer rotor carrying surface magnets and the inner rotor carrying magnets configured to obtain a flux concentration according to an embodiment of the present invention, [Fig 2] represents a perspective view of an inner rotor carrying magnets configured to obtain a flux concentration and an outer rotor carrying surface magnets, these rotors forming part of an electromagnetic motor according to an embodiment of the present invention,

[0048] [ Fig 3 ] represents a curve of total magnetic torque delivered by an electromagnetic motor according to the present invention,

[0049] [ Fig 4 ] represents a magnet allowing a concentration of flux when positioned with other similar magnets on the internal rotor of an electromagnetic motor according to the present invention, the magnet being segmented into several lateral bars each forming a unit magnet,

[0050] [ Fig 5 ] represents a magnet allowing a concentration of flux when positioned with other similar magnets on the internal rotor of an electromagnetic motor according to the present invention, the magnet being segmented into several longitudinal bars each forming a unit magnet,

[0051] [ Fig 6 ] represents a magnet allowing a concentration of flux when positioned with other similar magnets on the internal rotor of an electromagnetic motor according to the present invention, the magnet being pixelated into several small unit magnets in the form of square section pads,

[0052] [ Fig 7 ] represents a magnet allowing flux concentration when positioned with other similar magnets on the internal rotor of an electromagnetic motor according to the present invention, the magnet being pixelated into several small unit magnets in the form of hexagonal section pads,

[0053] [Fig 8] shows a sectional view of a wheel rim comprising an electromagnetic motor according to the present invention,

[0054] [Fig 9] shows a bottom view of a means of transport having four wheels, each of the wheels being provided with an electromagnetic motor according to the present invention.

[0055] In the following, reference is made to all figures taken in combination. When reference is made to a specific figure, this figure is to be taken in combination with the other figures for the recognition of the designated reference numerals. In the figures, when present, only one magnet or magnet pole and only one small unit magnet forming part of a magnet forming a magnet pole are referenced but what is stated respectively for the magnet forming a pole and the unit magnet is valid respectively for all the magnets forming a pole and all the unit magnets. The same applies in Figure 1 to the stator elements which are referenced only to a single element of the same type as well as to the recesses of the magnetic circuit in Figure 1.

[0056] Referring to all the figures and in particular firstly to figures 1 and 2, the invention relates to a drive motor 1 which is intended to be associated with a member 15 to be driven by being housed at least partially in the member 15 or by being placed against the member 15.

[0057] The motor 1 comprises an inner rotor 2 and an outer rotor 2a concentric with respect to a central axis of rotation 3, the rotors 2, 2a interposing between them a stator 10 with an air gap 14, 14a between the stator 10 and each rotor 2, 2a. Each rotor 2, 2a is provided with a magnetic circuit 8 for circulating magnetic flux opposite a respective air gap 14, 14a and carrying magnets 6, 6a. An inner and outer rotor yoke as well as the teeth 11 form the magnetic circuit 8 of the motor 1.

[0058] According to the invention, for the external rotor 2a, its magnets are surface magnets 6a positioned in or on the associated magnetic circuit 8 by being flush with the magnetic circuit 8 towards the air gap 14, 14a of the external rotor 2a with the stator 10 and, for the internal rotor 2, its magnets 6 are arranged to carry out a flux concentration by being buried and positioned radially in the magnetic circuit 8 of the internal rotor 2.

[0059] For a first type of surface magnet 6a, the magnet 6a is positioned on the magnetic circuit 8 of the associated rotor without the presence of a housing to receive it, therefore glued to the magnetic circuit 8.

[0060] A second type of surface magnet groups together magnets 6a partially inserted into a housing but protruding at least slightly from their housing, these magnets being described as semi-buried magnets.

[0061] These semi-buried or embedded 6a surface magnets have the advantage of adding a reluctant torque which can be used to limit the magnet volume or the current intensity at a given torque. The theoretical gains should however be put into perspective because of the potential leaks between the 6a magnets which are then greater.

[0062] The advantages of a surface magnet 6a of the first or second type are an optimal use of the surface magnets 6a for the creation of torque to the rotors 2, 2a internal and external and a limitation of the inter-magnet leakage flux.

[0063] With respect to the inner rotor, the flux concentration consists of a radial positioning of the magnets 6 with an ortho-radial magnetization. The superposition of the fluxes coming from the two magnets 6 facing each other creates a resultant flux at the air gap surface 14 which can be greater than the simple flux created by a surface magnet 6a when carried by a similar inner rotor. This is partly explained by the fact that the sum of the surfaces of the magnets 6 can be greater than the surface available for the placement of a surface magnet 6a.

[0064] As in a flux concentration the magnets 6 are buried, this has the major advantage of limiting the risk of demagnetization of the magnets 6 and of doing without the use of a hoop in any case for the internal rotor 2.

[0065] The buried magnets 6 are also more rigidly held in place in the magnetic circuit 8 than surface magnets 6a glued to the magnetic circuit 8 or semi-buried.

[0066] Figure 1 represents the architecture of the motor 1 with flux concentration at the inner rotor 2 with magnets 6 and an outer rotor 2a with surface magnets 6a. At the inner radius of the inner rotor 2, the magnetic circuit 8 has a recess 19 on an edge of the magnetic circuit 8 opposite the air gap 14 between the stator 10 and the inner rotor 2.

[0067] This recess 19 or removal of material may create a conically shaped recessed area pointing towards the air gap 14 and at a distance from it. This recessed area may be less than half the depth of the magnetic circuit 8 taken radially in the internal rotor 2.

[0068] This recess 19 or recessed area makes it possible to increase the leakage reluctance of the flux concentration magnets 6. There may be magnetic field losses making part of the magnet 6 useless for creating torque.

[0069] The presence of the recesses 19, each recess 19 being located between two adjacent flux concentration magnets 6 and at equal distance from the two magnets 6, theoretically makes the presence of leakage flux limited compared to a full magnetic circuit 8.

[0070] Another advantageous optional feature is that a width of the magnets 6 of the inner rotor 2 effecting a flux concentration increases with distance from the air gap 14 of the inner rotor 2 with the stator 10, the width of the magnets 6 being perpendicular to the length of the magnets 6 taken in the radial direction. This makes it possible to improve the flux concentration.

[0071] A number of magnet poles 6 effecting flux concentration on the inner rotor 2 may be equal to a number of surface magnet poles 6a on the outer rotor 2a, although their positioning is different, the surface magnets 6a extending circumferentially in their magnetic circuit 8 on the outer rotor 2a and the magnets 6 effecting flux concentration extending radially in their magnetic circuit 8 on the inner rotor 2.

[0072] In this configuration, the field lines therefore cross the two rotors 2, 2a.

[0073] It has been found that the current density remains globally unchanged for a motor 1 with magnets 6 carrying out a flux concentration at the inner rotor 2 and with surface magnets 6a at the outer rotor 2a compared to a motor with surface magnets at the inner and outer rotors, such a rotor not being shown in the figures.

[0074] The torque generated by the external rotor 2a is also globally identical for the two motor 1 architectures. On the other hand, it is the torque generated by the internal rotor 2 with magnets 6 carrying out a flux concentration which has increased by 43% compared to a motor with an internal rotor with surface magnets, now making it possible to provide approximately 40% of the torque of motor 1 compared to 33% previously, hence an increase in the total torque of motor 1.

[0075] For example, at the level of internal rotor 2, the induction reaches 1.8 Tesla, explaining the gain in torque.

[0076] The stator 10 may comprise an armature core carrying teeth 11 having collars 13, also called isthmuses, at each of their longitudinal ends oriented towards a respective rotor.

[0077] Two adjacent teeth 11 may leave between them a notch 12 for a winding, the notch 12 being narrowed laterally by the collars 13 of the two adjacent teeth 11 at each of their longitudinal ends. The notches 12 may receive fractional pitch windings.

[0078] It is not possible to increase the thickness of the teeth 11 to improve the mechanical strength by increasing the notch depth, which would make the winding impossible to achieve. As the size is fixed, it is therefore necessary to reduce the number of notches 12. Rather than also reducing the number of pole pairs in order to keep the same winding architecture, it may be advantageous to use fractional pitch windings, which offer the opportunity to reduce the torque ripple at the same time. Figure 3 shows the total electromagnetic torque referenced C mag t and measured in Newton, meter or N / m as a function of time. In this figure, a very low torque ripple of the order of less than 5%, advantageously 1 to 5%, can be observed.

[0079] The current density can reach 18 A / mm 2. While it is possible to achieve this current density at peaks with water cooling, continuous operation may require oil cooling. The rationale for cooling will also depend on the thermal time constant of motor 1 and the actual temperature rise in the coil windings during the operating time.

[0080] Without this being limiting, for a motor 1 with internal rotor 2 comprising magnets 6 carrying out a flux concentration, with 28 pairs of poles, it was found that the number of notches 12 giving the best winding coefficient is 48. This also makes it possible to keep a number of symmetries of 4, which would be an advantage from a vibro-acoustic point of view.

[0081] A reduction in the number of notches 12 in the stator 10 has made it possible to increase the radius of the internal air gap 14, allowing the passage to reduce the mass and the overall volume of magnet 6, 6a of the motor 1 compensated by the increase in the resulting torque.

[0082] With a virtually identical total torque, the mass of motor 1 has been reduced by 29% with a slight increase in current density of 3.2%. In addition, from a qualitative point of view, the geometry of stator 10 appears more consistent from the point of view of the mechanical strength of teeth 11 and the possibility of winding.

[0083] Continuous copper losses are of the order of 10 kW, which limits efficiency to a value below 94% for this operating point.

[0084] Masses of the magnets 6, 6a of the inner and outer rotors 2, 2a can be selected respectively relative to each other so that the inner and outer rotors 2, 2a achieve an equivalent induction level. Such a motor 1 can have an estimated mass of the active parts of almost 70 kg, which implies a relatively low power density despite the high torque.

[0085] It turned out that, for a motor 1 according to the present invention with the previously mentioned characteristics seeking the highest possible volume torque and / or mass torque for rotation speeds of the order of 1,500 rotations per minute, the losses could remain high.

[0086] Furthermore, the high compactness of the motors 1 makes the extraction of losses a real challenge, beyond performance considerations. Among all the loss items, the most difficult to evacuate are those present at each rotor 2, 2a, linked to its rotary movement.

[0087] It is thus optionally sought to reduce one of the main loss items in motor 1 linked to magnets 6, 6a.

[0088] Due to the non-zero electrical conductivity of the ferromagnetic materials constituting the magnets 6, 6a, these are subject to the presence of eddy currents, sources of losses that are all the more significant as the field passing through them is strong. To reduce the presence of these circulating currents, the objective was set to reduce the average conductivity of the medium without having too strong an impact on the magnetic properties of the material.

[0089] A first solution involves segmenting the magnets 6, 6a into multiple bars 7. These bars 7 are spaced from each other by the presence of an electrically insulating material, for example a non-conductive varnish. This process makes it possible to drastically reduce the formation of circulating currents without excessively deteriorating the magnetic performance.

[0090] Figures 4 to 7 show as a pole magnet a magnet 6 effecting flux concentration but this is also applicable to a surface magnet 6a.

[0091] Bars 7 extending laterally in the magnet 6 forming unit magnets 7 are shown in Figure 4 while Figure 5 shows bars 7 extending in the longitudinal direction of the magnet. These bars 7 may advantageously be of parallelepiped shape.

[0092] In Figures 4 and 5, it is visible that a large magnet, intended to become a magnet 6 carrying out a flux concentration, can be cut into more than five unit magnets 7 for longitudinal bars 7 and into more than twenty unit magnets 7 for lateral bars 7.

[0093] In the case where this solution is not sufficient, it is possible to go further with pixelization. According to this technique, the magnets 6 will be segmented in two directions following rules similar to that of the tiling of the regular plane in the plane orthogonal to the direction of the flux or to the direction of polarization of the magnets 6. The conventional patterns used for pixelization can be square, rectangular, cylindrical or polygonal, in particular hexagonal or ovoid. The unit magnets 7 in this configuration can be in the form of studs or rods of elongated shape. The unit magnets 7 can extend in length in the thickness of a magnet structure formed by a grouping of the unit magnets 7 secured to each other.

[0094] Thus, a large magnet intended to become a flux concentrating magnet 6 can be cut into a multitude of much smaller unit magnets 7. In Figures 6 and 7, more than fifty unit magnets 7 are shown as part of a single flux concentrating magnet 6.

[0095] The flux concentrating magnets 6 can be laser cut. A layer of insulating and adhesive varnish or an insulating composite resin can be inserted between the individual magnets 7.

[0096] However, to hold the unit magnets 7 relative to each other before bonding, it may be advantageous to leave in the flux-concentrating magnet 6 during cutting a heel which joins all the unit magnets 7 together. Such a heel may have a zig-zag shape, i.e. be non-planar by extending over several successive planes, which has been shown to reduce the eddy currents created by a similar but planar heel.

[0097] It should be kept in mind that the surface magnets 6a of the external rotor 2a can also be segmented or pixelated.

[0098] Particularly in the case of segmented or pixelated magnets 6, 6a, as the inner and outer rotors 2, 2a can rotate at high speed and be subjected to a high centrifugal force, the motor 1 can comprise at least one hoop circumferentially covering the magnets 6a of the outer rotor 2a, because the magnets 6 carrying out a flux concentration are buried in the magnetic circuit 8 and therefore better protected.

[0099] For the external rotor 2a, it is also the motor housing

[0100] 1 which can be used as a fret.

[0101] As shown in particular in figures 1 and 2, the electromagnetic motor 1 according to the present invention can be radial flux but this is not limiting.

[0102] In this case, the outer and inner rotors 2, 2a may respectively be in the form of a crown 9 perpendicular to the axis of rotation 3, each crown 9 being extended by a cylindrical portion 9a connected to the outer edge of the crown 9 and extending at a distance along the axis of rotation 3.

[0103] The references concern the crown 9 and the cylindrical portion 9a of the external rotor 2a but the internal rotor

[0104] 2 has the same configuration.

[0105] The rotors 2, 2a may be mechanically connected to each other by a connecting piece. This piece may be offset from the plane orthogonal to the axis of rotation 3.

[0106] As shown in Figure 8, the invention also relates to a member 15 driven by an electromagnetic motor 1 as previously described. A connecting piece ensures torque transmission between the electromagnetic motor 1 and the driven member 15. The driven member 15 is in this Figure 8 a wheel rim 15. The member 15 can be arranged external to the motor 1 by at least partially enveloping it, which is the case for a wheel motor for which the motor 1 is entirely or mostly integrated in the wheel. Alternatively, the member 15 can be attached to the electromagnetic motor 1 by being secured to one of the sides of the motor 1.

[0107] In the non-limiting case of a wheel motor, common name for a wheel 16 comprising inside it an electromagnetic motor 1 for its drive, the wheel motor can be part of a means of transport 17 by being associated with one or more other wheel motors, the means of transport 17 having a means of suspending the wheel motor while leaving it free to rotate.

[0108] As shown in Figure 9, the means of transport 17 may comprise a battery 21 powering the wheel motor(s) 16, the wheel motor also being able to serve as a generator for recharging the battery 21. This is valid for an electromagnetic motor 1 according to the present invention which can also serve as a generator. The electromagnetic motor(s) 1 present in the wheel(s) 16 may be controlled by an electronic unit 18 for controlling the means of transport.

Claims

CLAIMS) Electromagnetic motor (1) comprising an internal rotor (2) and an external rotor (2a) concentric with respect to a central axis of rotation (3), the rotors (2, 2a) interposing between them a stator (10) with an air gap (14, 14a) between the stator (10) and each rotor (2, 2a), each rotor (2, 2a) being provided with a magnetic circuit (8) for circulating magnetic flux opposite a respective air gap (14, 14a) and carrying magnets (6, 6a), with, for the external rotor (2a) surface magnets (6a) positioned in or on the associated magnetic circuit (8) flush with the magnetic circuit (8) towards the air gap (14, 14a) of the external rotor (2a) with the stator (10) and, for the internal rotor (2), magnets (6, 6a) arranged to perform flux concentration by being buried and positioned radially in the magnetic circuit (8) of the internal rotor (2),characterized in that the surface magnets (6a) of the external rotor (2a) protrude from the magnetic circuit (8) towards the respective air gap (14, 14a) while being partially embedded in the external rotor, each surface magnet (6) of the external rotor (2a) being segmented in at least two directions into a multitude of at least fifty pixelated unit magnets (7). Motor (1) according to the preceding claim, wherein the unit magnets (7) are in the form of elongated studs with circular, cylindrical, polygonal, or ovoid cross-sections, the studs extending partially into a thickness of the external rotor (2a). 3) Motor (1) according to the preceding claim, in which a width of the magnets (6, 6a) of the internal rotor (2) increases with distance from the air gap (14) of the internal rotor (2) with the stator (10). 4) Motor (1) according to any one of the preceding claims, wherein the magnetic circuit (8) of the internal rotor (2) has a recess (19) on an edge of the magnetic circuit (8) opposite the air gap (14, 14a) between the stator (10) and the internal rotor (2). 5) Motor (1) according to any one of the preceding claims, in which the stator (10) comprises an armature core carrying teeth (11) having collars (13) at each of their longitudinal ends oriented towards a respective rotor, two adjacent teeth (11) leaving between them a notch (12) for a winding, the notch (12) being narrowed by the collars (13) of the two teeth (11) adjacent at each of their longitudinal ends. 6) Motor (1) according to the preceding claim, in which the slots (12) receive fractional pitch windings. 7) Motor (1) according to any one of the preceding claims, in which the motor (1) comprises a ring circumferentially covering the magnets (6a) of the external rotor (2a). 8) Motor (1) according to any one of the preceding claims, wherein masses of the magnets (6, 6a) of the internal and external rotors (2, 2a) are respectively selected relative to each other so that the internal and external rotors (2, 2a) achieve an equivalent induction level. 9) Motor (1) according to any one of the preceding claims, wherein the motor (1) is radial flux, the external and internal rotors (2, 2a) being respectively in the form of a ring (9) perpendicular to the axis of rotation (3), each ring (9) being extended by a cylindrical portion (9a) connected to the outer edge of the ring (9) and extending a distance along the axis of rotation (3). 10) Motor (1) according to any one of the preceding claims, wherein the rotors (2, 2a) are mechanically linked to each other by a connecting piece with respect to the plane orthogonal to the axis of rotation (3). 11) Component (15) characterized in that it is driven by a motor (1) according to any one of the preceding claims, the component (15) being disposed externally to the motor (1) by at least partially enveloping it or by being attached to the motor (1) • 12) Component (15) according to the preceding claim, which is a wheel (16) driven in rotation by said motor (1), the wheel (16) housing the motor (1) inside it. 13) Means of transport (17), characterized in that it comprises at least one component (15) in the form of a wheel (16) driven in rotation by said motor (1) according to the preceding claim, the means of transport having a means of suspending the wheel (16) leaving the wheel (16) free to rotate.

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