Compact axial flux electric machine

Abstract

Compact axial flux electric machine. One aspect of the invention relates to a compact axial flux electric machine comprising a main rotating body including a frame and teeth extending each from an internal radial face of the frame, the frame further comprising a second external radial face opposite the first internal radial face, a main stator winding located in the main stator body, comprising a first axial end facing towards the rotating axial end of a main rotating winding and a second axial end opposite the first axial end,a rotary feed device comprising a feed rotor body and a feed stator body and wherein at least 50% along an axial length of the feed rotor body or the feed stator body is located axially between the external radial face of the main rotating body frame and the second axial end of the stator winding Figure to be published with the abbreviation: Figure 4a,

Description

Title of the invention: Compact axial flux electric machine TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of axial flux electric machines.

[0002] The present invention relates to an axial flux electric machine. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] The synchronous machine comprises, like any electric motor, a rotor and a stator, mainly the rotor forms the inductor and the stator forms the armature. In the state of the art, inductors for synchronous electric machines are known, wound and / or with magnets. The inductor may have an advantage in being wound. Indeed, a machine with a wound iron core can produce a higher induction than those with magnets which are also more expensive and thermally limited by their characteristics than a coil. Thus at iso volume, a synchronous electric machine comprising a magnet inductor will be more expensive, more thermally limited and less efficient (torque) particularly at high rotation speed than a machine compared to an electric machine comprising a wound inductor.

[0004] There are also mainly two main families of air gaps known in electrical machines.

[0005] A first family of synchronous electrical machine has a radial air gap, the flux of which is mainly radial, also called field, the air gap volume of which between a stator comprising coils forming the armature and the rotor forming an inductor (magnet or wound) is cylindrical in shape surrounding the axis of rotation of the rotor.

[0006] A second family of synchronous electrical machine has an axial air gap, the flux of which is mainly axial, also called an axial field, and the air gap volume of which between a stator comprising coils forming the armature and the rotor forming the inductor (magnet or wound) is in the form of a disc perpendicular to the axis of rotation of the rotor.

[0007] A transverse flux family is also known, having an axial air gap part and a radial air gap part.

[0008] The advantage of the axial air gap machine is to use the maximum diameter of the machine for the air gap surface, but the larger the useful air gap diameter, the greater the torque. Furthermore, these machines are often chosen for reasons of axial size, which is much smaller than those of radial air gap machines, which have the advantage of radial size.

[0009] The induced stator of an axial machine comprises a stator body and a winding housed in the stator body, which can be a concentric winding, a corrugated winding, etc.

[0010] The rotor is wound and may be a salient pole or claw inductor. It comprises a rotor body tightly mounted on the rotor shaft.

[0011] Claw rotors comprise a single coil wound around the axis of rotation passing through the claws formed in the rotor body. This makes it possible to have ampere turns produced by this coil passing through each pole having the advantage of improving the conductor rate per pole and therefore increasing the torque as well as reducing joule losses. However, the disadvantage is that the claws are subjected to a concentration of deformation stress at the foot of the claws by centrifugal force requiring a sufficiently large air gap depending on the manufacturing tolerances of the internal diameter of the armature and the external diameter of the claws. However, the larger the air gap, the more the performance of the synchronous electrical machine decreases. In addition, these claws have the disadvantage of having leakage fluxes not crossing the air gap and not contributing to the supply of torque.Finally, unlike the case of radial flux machines, a claw rotor of an axial machine will be unbalanced at the poles because the claws of a first polarity, for example North, extend from a frame of the rotor body along a radius relative to the axis of the rotor larger than the other claws of the second polarity, in this example South, which extend from the same frame but closer to the axis of rotation.

[0012] The salient pole inductor rotor comprises a rotor body comprising a ferromagnetic frame and a plurality of ferromagnetic teeth distributed angularly and extending axially from the frame. The salient pole rotor further comprises one coil per tooth. Each coil is wound around one of the ferromagnetic teeth.

[0013] The rotor coil, whether in a rotor body with salient poles or claws, must be supplied with current, the machine therefore requires a power supply device. This power supply device comprises a stator part, generally comprising brushes and is fixed to a yoke of the machine surrounding and secured to the stator and the stator part faces the rotor part, for example the brushes rub on a rotating part comprising copper traces, typically called a slip ring, mounted on one end of the rotor shaft surrounded by the stator part. This device increases the axial length of the machine while this is often chosen to reduce axial size. One of the known solutions has then been to manufacture power supply devices whose rotor part faces axially the stator part to reduce axial size.However, these power devices always increase the axial length of the electric machine.

[0014] There is therefore a need to have a synchronous electrical machine architecture of a single axial flux wound inductor while allowing its length to be reduced. axial without reducing the torque performance of the electric machine. Summary of the invention

[0015] The invention offers a solution to the problems mentioned above, by making it possible to incorporate at least part of the power supply device surrounded by the active part of the electrical machine (the rotor body and the stator body).

[0016] One aspect of the invention relates to a compact axial flux electric machine comprising: • a rotor comprising: • a rotation axis rotation shaft, • a main rotating body integral in rotation with the rotation shaft, made of ferromagnetic material, comprising a frame and teeth each extending from an internal radial face of the frame, the frame further comprising a second external radial face opposite the first internal radial face, • a main rotating winding located in the main rotating body, the main rotating winding comprising a first rotating axial end and a second rotating axial end opposite the first axial end, • a stator comprising: • a main stator body comprising an opening crossed by the rotation shaft, • a main stator winding located in the main stator body and secured to the latter, comprising a first axial end facing the rotating axial end of the main rotating winding and a second axial end opposite the first axial end, • a rotary feeding device comprising: • a power supply rotor body secured to the rotation shaft and electrically connected to the main rotating winding to power it, • a power supply stator body integral in rotation with the main stator body to transmit energy to the power supply rotor body, • characterized in that the power supply rotor body and the power supply stator body each comprise an axial length and in that at least 50% of the axial length of the power supply rotor body or the power supply stator body is located axially between the external radial face of the frame of the main rotating body and the second axial end of the stator winding.

[0017] Thanks to the invention, the incorporation of the power supply device in an area located at least largely between the axial end of the rotor frame and that of the stator winding greatly reduces the size of the axial flux electric machine. The invention makes it possible to use an area of ​​an axial flux machine that has no use for increasing the torque of the electric machine.

[0018] Indeed, as can be seen in [Fig.2], the fact of using an axial flux machine with an internal radius noted rl in [Fig.2], from the rotor body to the level of the coil equal to 60% of the external radius noted r2, from the rotor body to the level of the coil makes it possible to have the maximum torque of the electric machine. Thus, there is a free zone between the internal radius and the radius of the rotation shaft of the machine. The fact of using this zone to house at least a large part of the power supply device by mainly surrounding its rotor or stator body with the main stator body and / or the stator, makes it possible to reduce its axial size and therefore to reduce or even not increase the total axial length of the electric machine.Of course, some machines with radii of several meters can have a ratio lower than 40% and have enough space for the insertion of the power supply device in this free zone between these two axial ends (frame and stator winding).

[0019] In addition to the characteristics which have just been mentioned in the preceding paragraph, the electrical machine according to one aspect of the invention may have one or more complementary characteristics among those in the following paragraphs, considered individually or according to all technically possible combinations.

[0020] According to one embodiment, the power supply rotor body and the power supply stator body each comprise an axial length and in that at least 50% along the axial length of the power supply rotor body or the power supply stator body is located axially between the second axial end of the rotor winding and the second axial end of the stator winding.

[0021] According to one embodiment, the power supply rotor body has 100% of its axial length located axially between the second outer radial face and the second axial end of the stator winding. According to one example, the power supply rotor body has 100% of its axial length located axially between the second outer radial face and the first axial end of the stator winding and in that at least 50% of the power supply stator body is located axially between the first end of the rotor winding and the second axial end of the stator winding.

[0022] According to one embodiment, • the rotating body further comprises: • a first radial face of axial rotor air gap, • a second radial face of the rotor axial end, opposite the first radial face of the rotor axial air gap, • the stator body also includes: • a first radial face of the stator axial air gap facing the first radial face of the rotor axial end, • a second radial face of the stator axial end opposite the first radial face of the stator axial air gap, • teeth each comprising a fixed air gap surface forming a part of the first radial face of the stator axial air gap axially opposite the first rotor air gap face, • an opening surrounding the rotation shaft, centered on the axis of rotation, axially opposite the first rotor air gap face, and the axis of rotation extending from the first radial face of the stator axial end towards the second radial face of the stator axial end, • the power supply device being 100% located axially between the second radial face of the stator axial end and the second radial face of the rotor axial end. This embodiment makes it possible to house the power supply device without it influencing the axial length of the electrical machine.

[0023] According to one embodiment, the rotor comprises an internal radius measured between the axis of rotation and an internal radial end of the main rotor body located axially closest to the axial air gap and radially closest to the axis of rotation and an external radius measured between the axis of rotation and an external radial end of the main rotating body located axially closest to the axial air gap and radially furthest from the axis of rotation, and in that the internal radius is between 40% and 80% of the external radius: the fact of being in excess of 40% makes it possible to have sufficient space radially between the coil bodies at the level of the coils and the rotor shaft to house the power supply device.Whether a claw rotor, salient pole rotor or smooth pole rotor, each tooth comprises a base extending axially from the frame to a tip of the tooth, the tip comprises a radial axial air gap surface and in that the inner radius is measured at the tip edge closest to the axis of rotation and the outer radius at an edge of the tip furthest from the axis of rotation.

[0024] According to one embodiment, the power supply rotor body is axially opposite the power supply stator body. This makes it possible to use the space cy available lindic between the rotor and the stator having a diameter larger than the axial length.

[0025] According to an example of a combination of these last two embodiments: • the feed rotor body comprises a rotating outer feed radius less than or equal to the inner radius and comprises a first and a second rotating axial feed end face axially opposite each other, • the power stator body comprises a rotary power external radius less than or equal to the internal radius and comprises a first and a second axial power stator end face opposite each other axially, • the first rotary power supply axial end face and the first stator power supply axial end face face each other and are each located between the second axial end of the rotary winding and the second axial end of the stator winding.

[0026] According to a variant of the previous embodiment, the power supply rotor body is surrounded by at least one air gap formed between a first rotary air gap face of the rotor and a first stator air gap face of the stator.

[0027] According to one embodiment, the main rotating body is integral with the rotation shaft via the power rotor body. This allows the power rotor body as a connecting means and therefore to reduce the weight, furthermore this can allow to use all the available space formed inside the main rotating body.

[0028] According to one embodiment, the axial flux electric machine comprises a bearing between the power supply stator body and the rotation shaft. This makes it possible to better support the rotation shaft.

[0029] According to one embodiment, the rotary power supply device is a brush type, the power supply rotor body comprises a collector comprising at least two tracks insulated from one another and the power supply stator body comprising at least two brushes each in contact with one of the corresponding tracks. The tracks may be, for example, rings.

[0030] According to a variant of this embodiment, the rotary power supply device is inductive, • the power supply stator body comprising an induction circuit and • the power supply rotor body comprising • an induced coil opposite the induction circuit to transform the energy of the induction circuit into electric current, and • electronic components to rectify the electric current transformed by the induced coil, connected to the main rotating winding to power it. This reduces friction compared to the previous embodiment.

[0031] According to one example, the power supply rotor body comprises an electronic printed card comprising the electronic components.

[0032] According to an example of this embodiment: the rotary power supply device is inductive, comprising: • a second power rotor body, • a second main rotating body secured to the second rotor body power supply, • a second main coil wound in the second main rotating body, • and in which the main stator body and the main stator winding are located between the two main rotating bodies and the power stator body secured to the main stator body is located between the two power rotor bodies. This makes it possible to balance the axial forces and therefore increase the efficiency of the machine and reduce wear on the bearings.

[0033] According to one example, the machine comprises a printed card comprising: • the main stator body, • the stator winding formed by traces engraved on the printed board and • the power supply stator body located between the two power supply rotor bodies, • the stator power supply winding formed by traces etched on the printed board. This makes it possible to have an axial flux machine that is easy to manufacture and also takes up little space axially.

[0034] According to a variant of these last two embodiments, the rotary supply device is capacitive.

[0035] According to one embodiment, the power supply device further comprises a second power rotor body, the power stator body being located between the first and second power rotor bodies to power them. This makes it possible to balance the axial forces between the rotor bodies and the stator body of the power supply device.

[0036] According to one embodiment, the power supply device further comprises a second power supply rotor body, the power supply stator body being located between the first and second power supply rotor bodies to power them. This makes it possible to balance the axial forces between the stator bodies and the rotor body.

[0037] According to one embodiment, the power supply device further comprises a second power stator body, the power rotor body being located between the first and second power stator bodies to power them. This makes it possible to balance the axial forces between the stator bodies and the rotor body.

[0038] According to one embodiment, the main rotating body comprises an opening housing the rotating shaft, the opening having a diameter equal to + or - 5% of the diameter of the opening of the main stator body. This makes it possible to reduce the weight of the main rotor.

[0039] According to one embodiment, the main rotor body comprises teeth comprising at least one radial air gap surface forming a portion of a first radial face of the rotor axial air gap, the rotor further comprises a hoop surrounding and in contact with the teeth of the rotor body.

[0040] According to an example of this embodiment, the hoop comprises walls forming a housing receiving a portion of the winding, the housing having a diameter external to the diameter of the teeth of the rotating body. This makes it possible to make the hoop in one piece with the winding and thus reduce the number of parts.

[0041] According to one example, the rotating body of the power supply device comprises a base fitted onto the rotor shaft and a shell extending from the base, the shell being integral with the rotating ferromagnetic body and forming a housing complementary to the housing of the hoop to receive a portion of the winding.

[0042] According to one embodiment, the main rotating body has a salient pole comprising a plurality of teeth each forming a north or south pole, the main rotating winding comprising a plurality of coils powered and electrically connected to the power supply rotor body, this makes it possible to have the advantages of a salient pole machine stated previously.

[0043] According to a variant of this embodiment, the main rotating body is claw-shaped, in which the teeth each form a north or south pole and each comprise a base extending axially from the base of the ferromagnetic frame and a beak extending radially from the base, the teeth forming either internal claws whose base extends from an internal periphery of the frame on the side of the orifice or external claws whose base extends on the side of an external periphery of the frame opposite the orifice. This makes it possible to increase or improve the conductor rate per pole and therefore increase the torque as well as to reduce joule losses while having an anti-deformation means for maintaining the claws.

[0044] According to one example, the rotor comprises a second main rotating body integral in rotation with the rotation shaft, identical to that of the first main rotating body and a second main rotating winding wound in the second main rotating body, the first and second main rotating bodies each comprising a plurality of teeth each forming a north or south pole, • the rotary power supply body being connected to the first and second rotary windings such that each tooth forming a pole of the second rotary body is axially aligned with a tooth of the first rotary body having a pole of a different polarity from the first body, • the main stator body being located axially between the two main rotating bodies and in that each tooth comprises a second air gap surface opposite the first air gap surface and in that the second air gap surface is located opposite the second main rotating body.

[0045] According to one embodiment, the stator comprises a second main stator body identical to and integral in rotation with the first main stator body and the power supply stator body, and a second main stator winding wound in the second main stator body, the first and second main stator bodies each comprising a plurality of teeth each forming a north or south pole, • the main rotating body being located axially between the two main stator bodies and in that the frame comprises several angular sections and the second external radial face of the frame forms on each section a second air gap surface opposite the first air gap surface and in that the second air gap surface is located opposite the second main stator body.

[0046] These last two examples each allow the axial forces to be balanced.

[0047] In particular in these last two embodiments, the use of a power supply device respectively with a double rotary power supply body or with a double stator power supply body, each described previously in one embodiment, is particularly advantageous, both in terms of size and in terms of distribution of forces and electrical energy.

[0048] According to one embodiment, the rotor further comprises inter-tooth-base magnets between each tooth.

[0049] According to one embodiment, the rotor further comprises inter-pole magnets between each tooth.

[0050] These two previous embodiments each make it possible to increase the magnetic saturation level of the claw and therefore to have a greater inductive current before saturation and therefore the possibility of having more torque. That is to say that a claw without a magnet will be magnetically saturated more quickly than the same claw with a magnet.

[0051] According to another unclaimed innovation, an axial flux electric machine with

[0052]

[0053]

[0054]

[0055] claws includes: • a stator comprising a winding and teeth comprising a radial surface of axial air gap and • a claw rotor comprising an axis of rotation and a ferromagnetic body comprising a frame and teeth each extending from the frame in a claw shape, each tooth comprising: • a base extending axially from an internal face of the frame and • a beak extending radially from one end of the base opposite the frame to a free end of the beak, forming a radial axial air gap surface between its free end and its end extending from the base, located axially opposite the radial axial air gap surface, • in which every other tooth has its beak extending from its base towards the axis of rotation to its free end, each forming an external claw and the other teeth have its beak extending radially from its base towards the outside opposite the axis of rotation, each forming an internal claw, • characterized in that the rotor comprises inter-pole magnets each mounted between two beaks of an internal claw and an external claw and / or inter-frame-beak magnets each mounted between a free end of a beak and the frame. • According to one example, the machine includes a hoop surrounding the beaks of the internal and external claws. • According to one example, the machine comprises a power supply device according to the invention described above or a power supply device comprising its rotary part mounted on the rotation shaft outside the rotor and the stator and its stator part mounted against the stator or a yoke for example, axially opposite the stator. The invention and its various applications will be better understood upon reading the description which follows and examining the figures which accompany it. BRIEF DESCRIPTION OF THE FIGURES The figures are presented for information purposes only and in no way limit the invention. [Fig.l] represents a schematic diagram of an electrical machine with salient poles according to a first embodiment. [Fig.2] represents a curve representing the torque ratio versus ratios of internal and external diameters of the active parts of a main rotor or stator of an axial flux electric machine

[0056] [Fig.3a] represents a schematic diagram of an electric claw machine according to a second embodiment.

[0057] [Fig.3b] represents a schematic diagram according to another view of the machine electric claw according to the second embodiment.

[0058] [Fig.4a] schematically represents a third embodiment according to a axial section of an axial flux electric machine.

[0059] [Fig.4b] schematically represents a section AA of [Fig.4a].

[0060] [Fig.5a] schematically represents a fourth embodiment according to a axial section of an axial flux electric machine.

[0061] [Fig.5b] schematically represents a section AA of [Fig.5a].

[0062] [Fig.6a] schematically represents a fifth embodiment according to a axial section of an axial flux electric machine.

[0063] [Fig.6b] schematically represents a section AA of [Fig.6a].

[0064] [Fig.7a] schematically represents a sixth embodiment according to a section axial of an axial flux electric machine.

[0065] [Fig.7b] schematically represents a section AA of [Fig.7a].

[0066] [Fig.8a] schematically represents a seventh embodiment according to a axial section of an axial flux electric machine.

[0067] [Fig.8b] schematically represents a section AA of [Fig.8a].

[0068] [Fig.9a] schematically represents a ninth embodiment according to a axial section of an axial flux electric machine.

[0069] [Fig.9b] schematically represents a section AA of [Fig.9a].

[0070] [Fig. 10] schematically represents an axial section of a feeding device induction of an axial flux electric machine according to an example of one of the embodiments.

[0071] [Fig. 11] schematically represents an axial section of an induction power supply device of an axial flux electric machine according to an example of a second embodiment.

[0072] [Fig. 12] schematically represents an axial section of an induction power supply device of an axial flux electric machine according to an example of a third embodiment.

[0073] [Fig. 13] schematically represents an axial flux electric machine according to a ninth embodiment.

[0074] [Fig. 14] schematically represents a rotor of an axial flux electric machine according to the ninth embodiment.

[0075] [Fig. 15] schematically represents an axial section of an axial flux electric machine according to a tenth embodiment. DETAILED DESCRIPTION

[0076] The figures are presented for information purposes only and in no way limit the invention.

[0077] [Fig.l] shows a schematic representation of principle according to a three-dimensional view of an example of an axial flux electric machine according to a first embodiment.

[0078] The axial flux electric machine comprises a rotor 1 comprising a rotation shaft 11 with rotation axis X, a main rotating body 12 integral in rotation with the rotation shaft 11 and a main rotating winding 13 located in the main rotating body 12. The main rotating body 12 is ferromagnetic and comprises a rotating frame 121 in the form of a ferromagnetic crown and ferromagnetic teeth 120 each extending axially from an internal radial surface of the rotating frame 121 and each comprising a radial surface of axial air gap axially opposite the rotating frame 121.

[0079] In this embodiment, the teeth 120 are each a salient pole each comprising a central portion extending axially from the internal radial surface of the rotary frame 121 and a beak extending axially from the central portion and projecting circumferentially on either side. The beak therefore comprises the radial surface of the axial air gap. The main rotary winding 12 may be concentric or distributed, in this case it is concentric and comprises a coil 130 per salient pole (of which only two are referenced) but could also have a concentric winding having a coil on 2 salient poles.

[0080] The axial flux electric machine further comprises a stator 2 comprising a main stator body 21 comprising a central opening 21o crossed by the rotation shaft 11.

[0081] The stator further comprises a main stator winding 23 located in the main stator body 21 and secured to the latter.

[0082] The main stator body 21 is in this embodiment also ferromagnetic and comprises a ferromagnetic stator frame 211 and teeth 210 also forming salient poles extending from an internal radial surface of the stator frame 211. The teeth 210 have the same shape as that of the main rotating body 11 (central part and beak) but do not have the same dimension. In this case, in this example the main stator body 21 comprises fewer teeth 21 than the number of teeth 110 of the main rotating body 11. The radial axial air gap surfaces of the teeth 210 of the main stator body 21 face the teeth 110 of the main rotating body 11 delimiting between them an axial air gap, in other words the axial air gap is delimited axially between the radial axial air gap surfaces of the tips of the teeth of the main stator body 21 and of the main rotating body 11.

[0083] The main stator winding 23 may be concentric or distributed, in this case it is concentric and comprises a coil 230 per salient pole but could also have a concentric winding having a coil on 2 salient poles. The main stator body 21 may also be, according to another example, made of amagnetic or paramagnetic material, for example resin and fiberglass or even a PCB type electronic card comprising conductive active parts (for example etched copper layer) each forming the concentric type coil.

[0084] The main rotary winding 13 and the main stator winding 23 each comprise a first and second axial end opposite each other, called a first rotary axial end 13a and a second rotary axial end 13b for the main rotary winding 13 and are called a first axial end 23a and a second axial end 23b for the main stator winding 23. The first rotary axial end 13a and stator axial end 23a are the ends closest to the axial air gap. In this embodiment, the two main rotary and stator windings 13, 23 being concentric windings, at least one coil comprises the first axial end 13a, 23a and at least one other coil (or the same) comprises the second axial end 13b, 23b.

[0085] The frames 121 and 211 of the main rotating and stator bodies each have in this example a washer shape and extend axially between an external radial face and the internal radial face.

[0086] The electrical machine further comprises a rotary power supply device C comprising a power supply rotor body C1 secured to the rotation shaft 11 and electrically connected to the main rotary winding 13 to power it. The electrical machine thus further comprises conductors (not shown) connecting the power supply rotor body C1 to the main rotary winding 13 (which may be a continuity of a conductor forming the main rotary winding 13 or a coil of the power supply rotor body C1

[0087] The rotary power supply device C further comprises a power supply stator body C2 integral in rotation with the main stator body 21 to transmit the energy to the power supply rotor body CL. The mechanical connection between the power supply stator body C2 and the main stator body 21 is not shown but may for example be arms extending radially between them in the central opening 21o or a plate closing the central opening 21o.

[0088] In this example, the power supply stator body C2 surrounds the power supply rotor body CL. In this example, the stator body C2 comprises brushes and the power supply rotor body Cl comprises a commutator with blades for powering the power supply coils of the main rotating winding 13.

[0089] The power rotor body C1 comprises an axial length 11 and the power stator body C2 has an axial length 12 which are not referenced in this [Fig.l]. By the axial length 11 of the power rotor body C1 or the axial length 12 of the power stator body C2, is meant respectively the maximum length of the rotary and stator parts of the power device C necessary for the transmission of electrical energy from one to the other. At least 50% of the axial length 11 or 12 of the power rotor body C1 or of the power stator body C2 is located axially between the second external radial face 12b of the frame 121 of the main rotary body 12 and the second axial end 23b of the stator winding 23.

[0090] Here in this example the two axial lengths 11 and 12 are equal. In this example, the power supply rotor body C1 and the power supply stator body C2 are each surrounded by the rotor 1 and the stator 2 such that they are each located axially between the two external radial faces of the stator 211 and rotor 121 frames. In other words the length between the external radial face of the rotor 121 frame and the external radial face of the stator 211 frame is longer than each of the two axial lengths 11 and 12. In other words, the power supply device C is entirely located axially between these external radial faces of the stator 211 and rotor 121 frames. In this case the power supply device is surrounded by the two stator 211 and rotor 121 frames and by the axial air gap between the rotor 1 and the stator 2.In this example, the largest radius R4 of the power supply stator body C2 (the largest radius therefore of the power supply device) is less than the internal radius R2 of the main rotating body 11 measured at the level of the tip of the tooth 120 closest to the x axis (i.e. the smallest radius of the rotating body 12 measured at the level of the tips of the teeth 120).

[0091] Thus in this example the feed device C does not take up any axial space. In addition, the internal radius R2 is between 40 and 80% (here 60%) of an external radius RI of the main rotating body 11 measured at the level of the tip of a tooth furthest from the axis X (i.e. the largest radius of the rotating body 12 measured at the level of the tips of the teeth 120). As can be seen in [Fig.2], this ratio makes it possible to have the best torque efficiency.

[0092] More precisely, in this example at least 50% (in this case 80%) along the axial length 11, 12 of the power supply rotor body C1 or of the power supply stator body C2 (in this case both bodies) is located axially between the second axial end 13b of the rotary winding 13 and the second axial end 23b of the stator winding 23. Thus the volume of the power supply device is located in a free location without affecting the axial length of the machine and without reducing the efficiency of the axial flux electric machine.

[0093] Figures 3a and 3b each schematically represent a three-dimensional view of an example of an axial flux electric machine according to a second embodiment identical to the example of the first embodiment except that the rotor 1 is different and the power supply device C is different.

[0094] In this example, the rotor 1 is claw-shaped and not salient-pole as in the first example of the first embodiment, in other words the main rotating body 12 is different in that the teeth 120 have a claw shape and in that the winding 13 is a single coil wound between the claws. Every other tooth 120 is an external claw 120e comprising a base extending axially from the inner face of the frame 121 to the radial level of the outer radius RI and the other teeth are internal claws 120i extending from the inner face of the frame 121 to the radial level of the inner radius R2. As can be seen, the internal and external claws are angularly alternated. The outer claws 120e each include a beak extending radially from the base toward the axis of rotation and the inner claws 120i each include a beak extending radially from the base outwardly away from the axis of rotation X.

[0095] In this second embodiment, the power supply device C is different in that the power supply rotor body C1 is located axially opposite the power supply stator body C2. The power supply device C can always be brushed or can be capacitive or even inductive, in the latter case, the power supply device C can be like that shown in section [Fig.l 1] explained below.

[0096] In [Fig.3a], we can see the power supply rotor body Cl surrounded by the main rotating body 12 and the rotating winding 13 of the rotor 1 and in [Fig.3b] we can see the power stator body C2 surrounded by the main stator body 21 and the rotating winding 23 of the stator 2.

[0097] In this example, the main rotating body 12 is coupled to the rotation shaft 11 via the power rotor body CL. The mechanical connection between the power rotor body Cl and the main rotating body 12 is not shown. For example, arms forming spokes connecting the two bodies can be produced. According to another example, the power rotor body Cl can be mounted tightly in the main rotating body 12 (in the latter case an external radius R3 of the power rotor body Cl would be equal to the internal radius R2 of the main rotating body 12).

[0098] As in [Fig.l] of the previous embodiment, the mechanical connection between the power supply stator body C2 and the main stator body 21 is not shown, but may for example be arms extending radially between them in the central opening 21o or a plate closing the central opening.

[0099] The electric machine further comprises here a PI bearing (a ring) mounted in the power supply stator body C2 surrounding the rotor shaft 11 to support it and allow its rotation along the X axis.

[0100] In this embodiment, the power supply device C is located between the two surfaces between at least 50% along the axial length 11, 12 of the power supply rotor body C1 or of the power supply stator body C2 is located axially between the second axial end 13b of the rotary winding 13 and the second axial end 23b of the stator winding 23.

[0101] This feed device C can also be mounted in place of that of the machine of the first embodiment and vice versa.

[0102] Other embodiments will now be described, the rotor 1 can be represented with claws or with salient poles as in the first or second embodiment and can also be replaced by one or the other.

[0103] [Fig.4a] represents a schematic diagram according to an axial section (comprising the axis of rotation) of an electric machine according to a third embodiment and [Fig.4b] a section AA of the machine at the level of the beaks of the teeth 120 of the main rotating body 12.

[0104] This electrical machine is identical to that of the second embodiment except that the rotor has salient poles as in the first embodiment and that the frame 121 is coupled to the rotor shaft 11. Thus in this example, the power supply rotor body C1 is mounted axially between the frame 121 and the power supply stator body C2 while being surrounded by the teeth 120, the axial air gap and the teeth 211. Furthermore, the axial length dimension 11 of the power supply rotor body C1 is shown between a first end Cia and a second end Clb. As can be seen, here the power supply rotor body Cl is located axially (according to its length 11 to 100%) between the second axial end 13b of the rotary winding 13 and the second axial end 23b of the stator winding 23. An empty space is located axially between the internal radial face of the frame 121 and the second axial end of the power supply rotor body Cl.Thus, the feed device C could also, according to another example, be moved axially towards this internal radial face of the frame 121.

[0105] The axial length 12 of the power supply stator body C2 is also shown between a first end C2a and a second end C2b. Here in this example only 50% of the axial length 12 of the power supply stator body C2 is located axially between the second axial end 13b of the rotating winding (13) and the second axial end 23b of the stator winding 23.

[0106] Finally, the electrical machine comprises in this example a closing plate 23 partially closing the central opening and making it possible to fix the power supply stator body C2 to the main stator body 21 by being pressed against its second axial end radial face 21b and against the second end C2b of the power supply stator body C. The plate 23 can be fixed by gluing or by screwing or by welding, or by crimping or any other fixing means. The electric machine further comprises a bearing PI between the rotor shaft 11 and the power supply stator body C2 allowing the rotational connection between them.

[0107] [Fig.5a] represents a schematic diagram according to an axial section (comprising the axis of rotation) of an electric machine according to a fourth embodiment and [Fig.5b] a section AA of the machine at the level of the beaks of the teeth 120 of the main rotating body 12.

[0108] This electrical machine is identical to that of the second embodiment except that the power supply device C comprises a second power supply rotor body Cl', the power supply stator body C2 being located axially between the first and second power supply rotor bodies Cl, Cl'. In the case of a brush power supply device C, the power supply stator body C2 comprises brushes extending on either side of a brush support plate. In the case of an inductive power supply device C, the power supply device C may be like that shown in section [Fig. 11] explained below.

[0109] The machine may comprise an electrical conductor in a groove or on the shaft 11 connecting the second power supply rotor body Cl' to the coil 13 to supply it in parallel with the power supply rotor body CL

[0110] [Fig.6a] represents a schematic diagram according to an axial section (comprising the axis of rotation) of an electric machine according to a fifth embodiment and [Fig.6b] a section AA of the machine at the level of the beaks of the teeth 120 of the main rotating body 12.

[0111] This electric machine is identical to that of the third embodiment except as regards the following elements: • the main rotating body 12 is claw-type (as in the second embodiment) and is secured to the rotation shaft 11 by means of the power rotor body C1; • the main stator body 21 comprises a frame 211 in place of the plate 23, mounted on the bearing PI and in that the power supply stator body C2 is fixed to the frame 211.

[0112] [Fig.7a] represents a schematic diagram according to an axial section (comprising the axis of rotation) of an electric machine according to a fifth embodiment and [Fig.7b] a section AA of the machine at the level of the beaks of the teeth 120 of the main rotating body 12.

[0113] This electric machine is similar to that of the first mode except in that the power supply stator body C2 is mounted on a bearing PI and is mounted tightly in the opening of the main stator body 21 making them integral with each other.

[0114] Furthermore, in this example the power supply stator body C2 comprises, in addition to a part surrounding the main rotating body 12, a part mounted axially opposite the main rotating body 12.

[0115] Finally, the frame 121 of the rotor body 12 is directly mounted on the rotor shaft in this example. Such a power supply device may be brushed or inductive.

[0116] [Fig.8a] represents a schematic diagram according to an axial section (comprising the axis of rotation) of an electric machine according to a fifth embodiment and [Fig.8b] a section AA of the machine at the level of the beaks of the teeth 120 of the main rotating body 12.

[0117] This electrical machine is similar to that of the second embodiment except that the power supply device C comprises a second power supply stator body C2', the power supply rotor body C1 being located axially between the first and second power supply stator bodies C1, C1'. Each power supply stator body C1, C1' is mounted on a bearing P1, P1'. In the case of a brush power supply device C, each power supply stator body C2, C2' comprises brushes rubbing against either the same tracks of the power supply rotor body C1 or on different tracks. In the case of an inductive power supply device C, the power supply device C may be like that shown in section [Fig. 12] explained below.

[0118] Furthermore, as in the previous embodiment, the rotor body 12 comprises a frame 121 secured directly to the rotor shaft (fitted for example) and the power supply stator body C2 is mounted on a bearing PI and is mounted tightly in the opening of the main stator body 21, making them secured to each other.

[0119] The machine may comprise an electrical conductor in a groove or on the shaft 11 connecting the power supply rotor body C1 to the coil 13 to power it.

[0120] In these different embodiments described previously, the power supply device C comprises at least one part surrounded by at least one axial air gap formed between a first rotary air gap face 12a of the rotor 1 and a first stator air gap face 21a of the stator 2.

[0121] [Fig.9a] represents a schematic diagram according to an axial section (comprising the axis of rotation) of an electric machine according to a fifth embodiment and [Fig.9b] a section AA of the machine at the level of the beaks of the teeth 120 of the main rotating body 12.

[0122] This electrical machine is similar to that of the third embodiment, except that the power supply stator body C2 is mounted in place of the closing plate 23, i.e. against the external radial face 21b of the frame 211 of the body main stator 21 and is mounted on the PI bearing.

[0123] In the various examples, the rotor shaft may comprise at one of its ends a toothed wheel or directly a rotating device such as a fan.

[0124] [Fig. 10] schematically represents an inductive power supply device C which may be that mounted in the second, third, fifth and eighth embodiment, and a rotation shaft 11. The stator power supply body C2 comprises an induction circuit, here in this case a ferromagnetic body C21 and an induction coil C20 mounted in this ferromagnetic body C21. The rotor power supply body C1 comprises a ferromagnetic body C11 secured to the rotation shaft 11. The rotor power supply body C1 further comprises an induced coil C10 mounted in the ferromagnetic body C11 opposite the induction circuit to transform the energy of the induction circuit when it is powered by an external source into electric current. The rotor power supply body C1 comprises a printed board C12 comprising the electronics necessary for rectifying the electric current to power the main rotary winding 13.The printed card C12 in this case covers a surface of the ferromagnetic body Cl 1. The axial length 11 is also represented between the first end Cia located on an external face of the printed card and the second end Clb located in this case on one end of the ferromagnetic body CIL.

[0125] The axial length 12 is also represented between the first end C2a located on an external face of the ferromagnetic body C21 and the second end C2b located in this case on one end of the ferromagnetic body C21 opposite the second end Clb.

[0126] The power supply device further comprises connection terminals, not shown, for connecting the coil C20 to an electrical power source.

[0127] [Fig. 11] schematically represents an inductive power supply device C which may be an example of that mounted in the fourth embodiment and a rotation shaft 1. The power supply stator body C2 comprises an induction circuit, here in this case an induction coil C20 mounted in a ferromagnetic body C21.

[0128] According to another example, the ferromagnetic body C21 is a printed card comprising one or more traces forming the winding, the trace may be in the form of a spiral or several traces may be open concentric circles, one of the ends of which is connected to a following or preceding trace connecting them to each other in series.

[0129] The first and second power rotor bodies Cl, Cl' each comprise an identical ferromagnetic body Cl 1, Cl 1' each mounted tightly on the rotation shaft Cl, in which the induced coil CIO, CIO' is wound. Each body The power rotor body Cl, Cl' comprises an induced coil CIO, CIO' opposite the induction circuit to transform the energy of the induction circuit when it is powered by an external source, into electric current. Each power rotor body Cl, Cl' comprises a printed board C12, C12' comprising the electronics necessary for rectifying the electric current to power the main rotary winding 13.

[0130] In this example (as in that of [Fig. 10]), the power supply device further comprises connection terminals not shown for connecting the coil C20 to an electrical power source.

[0131] [Fig. 12] schematically represents an inductive power supply device C which may be an example of that mounted in the seventh embodiment, and a rotation shaft 11. Each power supply stator body C2, C2' comprises an induction circuit, here in this case an induction coil C20, C20' mounted in a ferromagnetic body C21, C21'. The power supply rotor body C1 is integral with the rotation shaft 11. The power supply rotor body C1 comprises a first and second induced coil CIO, CIO' each facing the corresponding induction circuit respectively of the first and second power supply stator bodies C2, C2' to transform the energy of the induction circuit when it is powered by an external source, into electric current.The power supply rotor body C1 comprises a first and a second printed card C12, C12' comprising the electronics necessary for rectifying the electric current transformed by the first and second induced coil CIO, CIO' respectively to power the main rotating winding 13.

[0132] In this example, the power supply rotor body C1, C1' comprises a first and a second identical ferromagnetic body C11, C11' each mounted tightly on the rotation shaft C1, in which the first and second induced coil C10, C10' are wound respectively. The first and a second printed board C12, C12' are located between the two ferromagnetic bodies C11, C11', one next to the other and could be a single printed board.

[0133] [Fig. 13] represents an axial flux electric machine according to a ninth embodiment, in which the stator 2 comprises a second main stator body 21' identical and integral in rotation with the first main stator body 21 and the power supply stator body C2.

[0134] The stator 2 further comprises a second main stator winding, not shown, wound in the second main stator body 21', the first and second main rotating bodies 21, 21' each comprising a plurality of teeth each forming a north or south pole. The first main stator winding 13 is also not shown to simplify the reading of the diagram.

[0135] The main rotating body 12 is located axially between the two main stator bodies 21, 21', also called hereinafter the central main rotating body. The central main rotating body 12 is also shown schematically in a three-dimensional view in [Fig. 14]. In this embodiment, the frame 121 comprises a plurality of ferromagnetic sections each having a portion of the second radial face forming on each section a second air gap surface opposite the first air gap surface and in that the second air gap surface is located opposite the second main stator body 21'. In this example, the rotor comprises a plurality of magnets M1, called inter-pole magnets mounted between each of the sections.

[0136] The rotor 1 further comprises a hoop 121f mounted around the sections of the frame 121 and a hoop 120f mounted around the tips of the teeth 120. Of course, the two hoops could be in one piece.

[0137] Furthermore, in this example, the main rotary winding comprises a coil 13a wound around a portion of one tooth 120 out of two on the side of the beak of the tooth 120 and a second coil 13b wound around another portion of one tooth 120 out of two on the side of the frame 121. Thus, each tooth 120 comprises a bare portion 120n around which none of the two coils 13a, 13b is wound (by going around). Thus, the notches 124 formed between each tooth 120 have a first axial zone filled by portions of conductors of the first coil 13a and a second axial zone filled by portions of conductors of the second coil 13b. Such a winding makes it possible to increase the copper filling rate in a notch in a simple manner. Indeed, the first coil 13a may have its last conductor turn closer to a bare part of the neighboring tooth than to the tooth around which the conductor turn is wound.

[0138] Finally, such an axial flux electric machine with these two main stator bodies 21, 21' and a central main rotary body 12 preferably comprises an inductive power supply device C according to the example of [Fig. 12] by having its power supply rotor body C1 in the central main rotary body 12, in particular by making it integral with the rotation shaft 11 and the two power supply stator bodies C2, C2 are each located in the corresponding main rotary body 12, 12'.

[0139] [Fig. 15] shows an axial flux electric machine according to a tenth embodiment, in which the rotor 1 comprises a second main rotating body 12' integral in rotation with the rotation shaft 11, identical to that of the first main rotating body 12 and a second main rotating winding 13' wound in the second main rotating body 12'. The first and second main rotating bodies 12, 12' each comprise a plurality of teeth each forming a north or south pole.

[0140] The main stator body 21 of the stator 2 is located axially between the two main rotating bodies 12, 12' and in that each tooth 210 comprises a second air gap surface opposite the first air gap surface and in that the second air gap surface is located opposite the second main rotating body 12.

[0141] In this example, the power supply device C is inductive and is of the type shown in [Fig. 11] such that the rotary power supply body C1 is connected to the first main rotary winding 13, and the second rotary power supply body C1' is connected to the second main rotary winding 13'. The power supply by the two rotary power supply bodies C1, C1 of the two main rotary windings 13, 13' is such that each tooth forming a pole of the second main rotary body 12, 12' is axially aligned with a tooth of the first rotary body having a pole of a different polarity from the first body. In particular, in this example, the main rotary windings 13, 13' have salient poles, one tooth 120 out of two.The main rotating bodies 12, 12' are offset from each other angularly so that a bare tooth 120 (i.e. the winding does not include a turn wound around the tooth) of the first main rotating body 12 is axially aligned with a tooth 120 wound by the second main winding 13', of the second main rotating body 12. Thus, in this example, the first power rotating body Cl powers the first main winding 13 in a first direction and the second power rotating body Cl' powers the second main winding 13' in the other direction.

[0142] The power supply stator body C2 is integral with the main stator body 21 of the stator 2, for example by arms or by being tightly mounted. Of course, the machine could have a power supply device C comprising only one rotary power supply body C1 supplying the two main rotary windings 13, 13'. In this example, the power supply stator body C2 and the main stator body 21 could be made of resin or fiberglass, in particular formed by a printed card whose etched traces would form the power supply winding 13 and the induction coil C20.

[0143] Unless otherwise specified, the same element appearing in different figures has a single reference.

Claims

Claims

1. Compact axial flux electric machine comprising: - a rotor (1) comprising: • a rotation shaft (11) with rotation axis (x), • a main rotating body (12) integral in rotation with the rotation shaft, made of ferromagnetic material, comprising a frame (121) and teeth (120) each extending from an internal radial face of the frame (121), the frame (121) further comprising a second external radial face (12b) opposite the first internal radial face, • a main rotary winding (13) located in the main rotary body (12), the main rotary winding (13) comprising a first rotary axial end (13a) and a second rotary axial end (13b) opposite the first axial end (13a), - a stator (2) comprising: • a main stator body (21) comprising an opening crossed by the rotation shaft (11), • a main stator winding (23) located in the main stator body (21) and secured to the latter, comprising a first axial end (23a) facing the rotary axial end (13a) of the main rotary winding (13) and a second axial end (23b) opposite the first axial end (23a) - a rotary feed device (C) comprising: • a power supply rotor body (Cl) secured to the rotation shaft (11) and electrically connected to the main rotary winding (13) to power it, • a power supply stator body (C2) rotationally fixed to the main stator body (21) to transmit energy to the power supply rotor body (Cl), • characterized in that the power supply rotor body (Cl) and the power supply stator body (C2) each comprise a axial length (11,12) and in that at least 50% along the axial length (11,12) of the power supply rotor body (Cl) or of the power supply stator body (C2) is located axially between the external radial face (12b) of the frame (121) of the main rotating body (12) and the second axial end (23b) of the stator winding (23).

2. A compact axial flux electric machine according to claim 1, wherein the rotor (1) comprises an inner radius (rl) measured between the axis of rotation (x) and an inner radial end (21i) of the main rotor body (11) located axially closest to the axial air gap and radially closest to the axis of rotation (X) and an outer radius (r2) measured between the axis of rotation (x) and an outer radial end (21e) of the main rotating body (11) located axially closest to the axial air gap and radially furthest from the axis of rotation (x), and in that the inner radius (rl) is between 40% and 80% of the outer radius (r2).

3. Compact axial flux electric machine according to claim 1 or 2, in which the power rotor body (Cl) is axially opposite the power stator body (C2).

4. A compact axial flux electric machine according to claims 2 and 3, wherein - the power rotor body (Cl) comprises a rotary power outer radius (r3) less than or equal to the inner radius (rl) and comprises a first and a second rotary power axial end face (Cia, Clb) axially opposite each other, - the power stator body (C2) comprises a rotary power outer radius (r4) less than or equal to the inner radius (rl) and comprises a first and a second rotary power stator axial end face (C2a, C2b) axially opposite each other, - the first rotary power axial end face (Cia) and the first rotary power stator axial end face (C2a) face each other and are each located between the second axial end (13b) of the winding rotary (13) and the second axial end (23b) of the stator winding (23).

5. Compact axial flux electric machine according to one of the preceding claims, in which the main rotating body (12) is integral with the rotating shaft (11) via the power rotor body (Cl).

6. Compact axial flux electric machine according to one of the preceding claims, comprising a bearing (PI) between the power supply stator body (C2) and the rotation shaft (11).

7. Compact axial flux electric machine according to one of the preceding claims, in which the rotary power supply device (C) is brush-type, the power supply rotor body (Cl) comprises a collector comprising at least two tracks insulated from each other and the power supply stator body (C2) comprising at least two brushes each in contact with one of the corresponding tracks.

8. Compact axial flux electric machine according to one of claims 1 to 6, in which the rotary power supply device (C) is inductive, - the stator power supply body (C2) comprising an induction circuit and - the rotor power supply body (Cl) comprising: • an induced coil (CIO) opposite the induction circuit to transform the energy of the induction circuit into electric current, and • electronic components to rectify the electric current transformed by the induced coil (CIO), connected to the main rotary winding (13) to power it.

9. Compact axial flux electric machine according to the preceding claim, comprising: - a second power supply rotor body (Cl'), - a second main rotating body (12') integral with the second power supply rotor body (Cl), - a second main coil (12') wound in the second main rotating body (12'), - a printed card comprising: • the main stator body (21), • the main stator winding (23) formed by traces etched on the printed card and • the power supply stator body (C2), • the power supply stator winding formed by traces etched on the printed card. - and in which the main stator body (21) and the main stator winding are located between the two main rotating bodies (12') and the power supply stator body (C2) integral with the main stator body (21) is located between the two power supply rotor bodies (Cl, Cl').

10. A compact axial flux electric machine according to one of the preceding claims, wherein the power supply device (C) further comprises a second power supply rotor body (Cl'), the power supply stator body (C2) being located between the first and second power supply rotor bodies (Cl, Cl') to power them.

11. A compact axial flux electric machine according to one of claims 1 to 4 or one of claims 6 to 8, wherein the power supply device (C) further comprises a second power supply stator body (C2'), the power supply rotor body (Cl) being located between the first and second power supply stator bodies (C2, C2') to power them.

12. A compact axial flux electric machine according to any preceding claim, wherein the main rotating body (12) comprises an opening housing the rotating shaft, the opening having a diameter equal to + or - 5% of the diameter of the opening (210) of the main stator body (21).

13. A compact axial flux electric machine according to any preceding claim, wherein the main rotor body (12) comprises teeth comprising at least one radial air gap surface forming part of a first radial rotor axial air gap face (12a), the rotor (1) further comprises a hoop surrounding and in contact with the teeth of the rotor body.

14. A compact axial flux electric machine according to any preceding claim, wherein the main rotating body (12) is pole salient comprising a plurality of teeth each forming a north or south pole, the main rotating winding (13) comprising a plurality of coils powered and electrically connected to the power rotor body (Cl).

15. A compact axial flux electric machine according to one of the preceding claims, wherein the main rotating body (12) is claw-type, wherein the teeth (120) each form a north or south pole and each comprise a base each extending axially from the ferromagnetic frame (121) and a beak extending radially from the base, the teeth forming either internal claws (120i) whose base extends from an internal periphery of the frame on the side of the orifice or external claws (120e) whose base extends on the side of an external periphery of the frame opposite the orifice.

16. A compact axial flux electric machine according to the preceding claim wherein the rotor further comprises inter-tooth-base magnets between each tooth.

17. A compact axial flux electric machine according to any preceding claim, wherein the rotor further comprises interpole magnets between each tooth.

18. Compact axial flux electric machine according to one of the preceding claims, wherein: - the rotor (1) comprises a second main rotating body (12') integral in rotation with the rotation shaft (11), identical to that of the first main rotating body (12) and a second main rotating winding (13') wound in the second main rotating body (12'), the first and second main rotating bodies (12, 12') each comprising a plurality of teeth each forming a north or south pole, - the power rotating body (Cl) being connected to the first and second rotating windings (13, 13') such that each tooth forming a pole of the second rotating body is axially aligned with a tooth of the first rotating body having a pole of a different polarity from the first body, - the main stator body (21) being located axially between the two main rotating bodies (12,12') and in that each tooth (210) comprises a second air gap surface opposite the first air gap surface and in that the,

19. second air gap surface is located opposite the second main rotating body (12'). Compact axial flux electric machine according to one of the preceding claims, in which: - the stator (2) comprises a second main stator body (21') identical to and integral in rotation with the first main stator body (21) and the power supply stator body (C2), and a second main stator winding wound in the second main stator body (21'), the first and second main stator bodies (21, 21') each comprising a plurality of teeth each forming a north or south pole, - the main rotating body (12) being located axially between the two main stator bodies (21, 21') and in that the frame (121) comprises several angular sections and the second external radial face (12b) of the frame (121) forms on each section a second air gap surface opposite the first air gap surface and in that the second air gap surface is located opposite the second main stator body (21').

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