Axial flux machine comprising a one-piece wound rotor body

Abstract

Axial flux machine comprising a one-piece wound rotor body. One aspect of the invention relates to an axial flux electric machine (1B) comprising a stator (3B) and a rotor each comprising a ferromagnetic body (20A, 20B) of which that of the rotor is made of a single one-piece including a yoke (24A, 24B), each body comprising pole teeth comprising two lateral flat surfaces opposed to each other and notches formed each between two lateral flat surfaces of two circumferentially adjacent teeth. The stator (3B) and the rotor further comprising a winding (21A, 21B, 31A, 31B) comprising windings around a tooth comprising active parts each housed in one of the two adjacent notches of the pole tooth, forming a plurality of layers superimposed one on top of the other such that the active parts of the last layer face active parts of a last layer of the adjacent winding in the same notch.Figure to be published with the abbreviation: Figure 2A.

Description

Title of the invention: Axial flux machine comprising a one-piece wound rotor body. TECHNICAL FIELD OF THE INVENTION

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

[0002] The present invention relates to an axial flux machine and its manufacturing process, and in particular to an axial flux machine comprising a wound rotor. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Axial flux machines exist that include rotors generally with magnets. Axial machines with a wound rotor are generally not industrialized due to their fill factor, resulting from the shape of the cylindrical slots radially drilled into the rotor body. Other axial machines include hybrid rotors comprising wound pole teeth interposed between magnetic poles by permanent magnets. However, these permanent magnets are expensive, have radial mechanical retention problems due to centrifugal forces and axial problems due to the magnetic field between the stator and the rotor, have a lower operating temperature range than windings, and are less efficient than an electrical coil of the same volume. Therefore, there is a need for low-cost, high-performance wound-rotor electric machines. Summary of the invention

[0004] The invention offers a solution to the problems mentioned above, by proposing an electrical machine with good performance while reducing the manufacturing cost by manufacturing an electrical machine whose rotor winding and stator winding can be carried out by the same type of production machine.

[0005] One aspect of the invention relates to an axial flux electric machine comprising: • a rotor comprising a ferromagnetic body made of a single, monobloc piece, • a stator comprising a ferromagnetic body, • each ferromagnetic body comprising: • polar teeth comprising an axially extending base including an air gap surface facing the other ferromagnetic body and two opposing lateral flat surfaces each extending axially and radially from the air gap surface of the tooth to an opposite end of the air gap surface of the base, • notches formed each between two lateral flat surfaces of two circumferentially adjacent teeth, and comprising an axial opening between the two air gap surfaces of the two adjacent teeth, • in which: • the ferromagnetic body of the rotor further comprising a yoke including a bottom surface axially delimiting the bottom of the notch, • the stator and rotor further comprising a winding comprising a winding for each pole tooth, each winding comprising a conducting wire, each conductor of the rotor comprising an identical cross-section, and each conductor of the stator comprising an identical cross-section, forming a plurality of turns around the corresponding tooth, comprising • chignon sections outside the two adjacent notches circumferentially and • active parts each housed in one of the two adjacent notches of the polar tooth connecting each two bun parts, forming a plurality of layers comprising each of the active parts aligned along the lateral flat surface between the air gap surface of the corresponding polar tooth and the opposite end of the base, the layers being superimposed one on top of the other around the polar tooth such that the active parts of the last layer face active parts of a last layer of the neighboring winding in the same notch.

[0006] Thanks to the invention, the axial flux electric machine has a low cost and good performance.

[0007] Having teeth with flat surfaces defining the slots allows for well-aligned and therefore neatly arranged conductor layers, which improves the copper fill rate in the slot. For example, for cylindrical conductors, with the same slot volume, the fill rate is 35% for a cylindrical slot (easily made by radially drilling the magnetic body) and over 45% for slots with flat lateral surfaces. This increase in the fill rate improves the machine's performance for the same volume. Having a one-piece rotor body also provides good resistance to centrifugal force and facilitates balancing. Furthermore, the one-piece rotor body allows for better efficiency due to the magnetic field and lower costs. weaker than rotor bodies assembled in several parts forming in particular parasitic axial or ortho-radial air gaps between each part of the assembled rotor body.

[0008] Finally, such a machine can have the rotor and stator windings performed by the same type of winding machine, for example, a needle winder, thereby reducing production and research and development costs. Indeed, unlike a radial machine, the winding of such a machine is carried out in the same way since the rotor and stator have slots extending in a similar manner. Furthermore, the rotor and stator windings can even be performed by the same winder, reducing production investment costs. Using the same type of needle winder allows for the use of the same research and development and the same know-how, thus reducing costs. Moreover, unlike radial machines, the winding in the stator body and the rotor body can even be performed by the same winder.When using the same needle winding machine, the electric motor may exhibit winding traces characteristic of the winding machine, related to winding tolerances on the stator and rotor. Furthermore, having aligned layers of active parts increases the filling rate. Thus, this electric motor comprises, in each slot, active parts of a winding for a north pole tooth and active parts of a winding for a south pole tooth. Finally, such an electric motor is easily convertible; the stator body and its winding can become the rotor body and its rotor winding, and vice versa. In addition, such a motor can also have a two-part rotor and a central stator located axially between each rotor part, or conversely, a two-part stator and a central rotor located axially between each stator part.

[0009] In addition to the characteristics mentioned in the preceding paragraph, the electrical machine according to one aspect of the invention may have one or more additional characteristics from among the following, considered individually or in all technically possible combinations: • In one embodiment, each tooth of the rotor body and / or stator body comprises two notches forming an extension of the tooth's air gap surface, extending circumferentially towards another notch of an adjacent tooth, the slot opening being formed between the two notches. Having pole teeth with notched notches improves mechanical strength by retaining the winding within the rotor or stator body. Indeed, axial flux machines have a magnetic force that attracts one of the two rotor or stator windings towards the air gap. Furthermore, the notched notches, by partially closing the slots, improve magnetic performance and thus the efficiency of the electric machine. • In one embodiment, the ferromagnetic body of the stator is a single piece and includes a yoke with a bottom surface that axially defines the bottom of the slot. This allows the stator to be wound using the same type of needle winder, thus reducing manufacturing, research and development, and know-how costs. Furthermore, it makes it easy to manufacture, using the same type of machine, a dual-rotor electric machine with a central stator, or a dual stator with a central rotor. • According to a variant of the preceding embodiment, the ferromagnetic body of the stator consists of a plurality of parts, each formed by different teeth. Since the pole pieces of the stator do not experience centrifugal force, it is possible to make a stator without a yoke that serves as a mechanical support, thus reducing the weight of the stator and therefore of the electrical machine.

[0010] According to one embodiment, the conductor portion of a turn in a second layer of a rotor winding has a winding clamping tension value on the first layer surrounding the rotor pole tooth equal to ±10% of the winding clamping tension value of the second layer of a stator winding on the first layer surrounding the stator pole tooth. Using the same winding machine for both the rotor and the stator implies the same manufacturing tolerances related to the winding machine. During the winding of the first layer, the first turn is either on the slot root side or on the air gap side (the tooth's nose if it has one), and vice versa for the last turn of the layer. The active portion of the last wound turn of the first layer is therefore the closest in conductor length to the first active portion of the second layer.During winding by a needle winder (of the same type), due to its settings, wear, technology, etc., the clamping force exerted on the conductor will be identical on the lateral flat surface for the first layer and on the preceding layer for subsequent layers, whether winding the rotor or the stator. Therefore, the internal tolerance distance between the bottom and the nearest active part of the first layer, or the external tolerance distance between the bottom and the nearest active part of the first layer, will be identical for each winding of the rotor and / or stator. To optimize the copper fill in the slot and thus improve the efficiency of the electrical machine, it is necessary to maximize the active part within the slot. For this reason, the internal and external tolerances must be less than the conductor layer distance; otherwise, an additional turn can be added. • According to an example of this embodiment, each conductor section comprises a layer distance measured along the alignment of the active parts forming a layer, and an internal or external tolerance value Tl, T2 of a rotor winding between the last wound active part of the first layer and respectively the bottom of the slot or the surface opposite the bottom, is identical to the internal or external tolerance value Tl, T2 of a stator winding, the internal and external tolerance Tl, T2 each being less than a layer distance of the conductor in the slot. • For example, in each slot, a total tolerance value is equal to the sum of the internal and external tolerance T1, T2, the effective depth of each rotor slot subtracted from the total tolerance value is equal to the number of turns of the winding around the rotor tooth to form a layer multiplied by the layer distance of the conductor cross-section of the rotor winding and the effective depth of each stator slot subtracted from the total tolerance value is equal to the number of turns of the winding around the stator tooth to form a layer multiplied by the layer distance of the conductor cross-section of the rotor winding.

[0011] The effective slot depth is the slot depth less, if applicable, the thickness of an insulator such as insulating paper inserted into the slot or an insulating block surrounding the pole tooth. The effective slot depth depends on the conductor cross-section and a total manufacturing tolerance value comprising, in particular, an internal tolerance measured between a first active portion of the layer and the bottom of the slot, and an external tolerance measured between a last active portion and the slot tip. When the filling ratio is optimized, the total tolerance is therefore a function of the conductor layer distance. Thus, if the rotor winding conductor has the same layer distance as the stator winding conductor, the total tolerance Tt is identical.The winding of the stator and the rotor, performed by the same winding machine, called a needle winder because of its nozzles, implies the same total tolerance value. Indeed, each winding machine is set according to its own manufacturing tolerance, allowing for more or less tightness of the active parts against each other, thus imposing a tolerance.

[0012] According to one example, the first turn in each slot of the rotor and the first turn in each slot of the stator are housed in the same position within the slot. Because it is the same winding machine, the first turn is always located in the same position.

[0013] According to one embodiment, the number of pole teeth of the rotor is different from the number of teeth of the stator. This makes it possible to reduce torque ripples when the coils are energized.

[0014] According to a variant of this embodiment, the number of pole teeth of the rotor is identical to the number of pole teeth of the stator, and the slots of the rotor and stator have the same radial length and width. This simplifies winding using the same winding machine.

[0015] According to one embodiment, the electrical conductors of each rotor winding have a cross-sectional value different from the cross-sectional value of each stator conductor. By cross-sectional value, we mean the surface area of ​​the cross-section.

[0016] According to a variant of this embodiment, the electrical conductors of each rotor winding have the same cross-sectional area as each conductor of the stator. This simplifies winding using a single winding machine. It also reduces manufacturing costs.

[0017] According to one embodiment, the electrical conductors of each rotor winding have a different shape from the shape of each stator conductor. For example, the shape of the rotor winding conductor is such that the cross-section has a cylindrical or rectangular shape, and the shape of the stator winding conductor is such that the cross-section has a rectangular or cylindrical shape, respectively.

[0018] According to a variant of this embodiment, the electrical conductors of each rotor winding have an identical shape to the shape of each conductor of the stator, for example a rectangular or cylindrical section.

[0019] According to one embodiment, the electrical conductor of the rotor or stator windings is made of aluminum or copper.

[0020] In one embodiment, the ferromagnetic body of the rotor comprises a plurality of radially extending recesses, located closer to the external radial surface of the ferromagnetic body than to a flat surface of the tooth, opposite a tooth. This reduces the weight of the electric machine without compromising electromagnetic characteristics, while also improving cooling by the fluid expelled outwards by centrifugal force. Indeed, having such a recess in the rotor body extending from the inner diameter to the outer diameter reduces significant centrifugal force stresses, partly by reducing material at the outer diameter. Furthermore, such a recess can be used for balancing by adding material. In one example, the recess is a notch open on the external cylindrical surface. In a variant of this example, the recess is a hole extending radially on both sides.

[0021] According to one embodiment, the stator and / or rotor comprises an insulator mounted in the slot against the corresponding ferromagnetic body, surrounded and in contact with the turns of the first layer of the winding. According to an example in which the stator teeth and the rotor teeth are without teeth, the insulation is made of hard plastic and the windings of the rotor and stator winding are each made by the same winding machine.

[0022] According to one embodiment, the rotor body and / or the stator body is formed from a ferromagnetic metal strip, comprising notches and teeth, wound in a spiral to form the rotor body and / or the stator body respectively. This simplifies manufacturing and reduces the cost of the rotor body and / or the stator.

[0023] According to one embodiment, the flat surfaces delimiting a notch are parallel for each notch of each body of the rotor and the stator, the fact that the flat surfaces delimiting a notch are parallel makes it possible to improve the filling coefficient and therefore the efficiency of the machine.

[0024] Another aspect of the invention relates to a manufacturing process comprising: • a rotor winding stage using a needle winder, winding an electrical conductor around each pole tooth by inserting it through a slot opening, and • a stator winding step using the same needle winder according to the same winding method as the rotor.

[0025] According to one embodiment of this method, the electrical machine is, according to the embodiment in which the ferromagnetic body of the stator is a single piece, the method further comprising: • a manufacturing step for the stator body, comprising: • a sub-step of cutting a sheet metal strip, forming notches and teeth between each notch, • a sub-step of attaching one end of the band to a hub • a sub-step of winding the strip around the core of a winding machine forming the stator body, • a rotor body manufacturing stage, comprising: • a sub-step of cutting a sheet metal strip, forming notches and teeth between each notch, • a sub-step of attaching one end of the band to a hub • a sub-step of winding the strip around a core of the winding machine forming the rotor body

[0026] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0027] The figures are presented for illustrative purposes only and are in no way limiting of the invention.

[0028] [Fig.1A] shows a schematic representation of a cross-section of part of an axial flux electrical machine according to a first example of a first embodiment of the invention.

[0029] [Fig.1B] shows a schematic representation of part of a stator body according to the first example of the first embodiment of the invention.

[0030] [Fig.1C] shows a schematic representation of part of a stator according to the first example of the first embodiment of the invention

[0031] [Fig.1D] shows a schematic representation of two ferromagnetic bodies of an axial flux electric machine according to a second example of the first embodiment of the invention.

[0032] [Fig.2A] shows a schematic representation of an axial flux electric machine according to a first example of a second embodiment of the invention.

[0033] [Fig.2B] shows a schematic representation of the rotor of the axial flux electric machine according to the first example of the second embodiment of the invention.

[0034] [Fig.2C] shows a schematic representation of the stator of the axial flux electric machine according to the first example of the second embodiment of the invention.

[0035] [Fig.2D] shows a schematic perspective representation of the stator body of the axial flux electric machine according to the first example of the second embodiment of the invention.

[0036] [Fig.2E] shows a representation according to another perspective view of [Fig.2D] of a part of the stator body of [Fig.2D].

[0037] [Fig.2F] shows a schematic representation of a variant of the stator body of the axial flux electric machine according to the first example of the second embodiment of the invention.

[0038] [Fig.3A] shows a schematic representation of an axial flux electric machine according to a second example of the second embodiment of the invention.

[0039] [Fig.3B] shows a schematic representation of the rotor body of the axial flux electric machine according to the second example of the second embodiment of the invention.

[0040] [Fig.4] shows a schematic representation of a rotor body of a machine axial flux electric according to a third example of the second embodiment of the invention. DETAILED DESCRIPTION

[0041] The figures are presented for illustrative purposes only and are in no way limiting of the invention.

[0042] An axial flux electric machine IA is shown in part in a tangent section on [Fig.1A] according to a first example of a first embodiment of the invention.

[0043] The axial flux electric machine 1A comprises a stator 3A including a ferromagnetic body 30A, also referred to hereafter as the stator body. In this embodiment, the ferromagnetic body 30A of the stator 3A is made of a single, monolithic piece, a portion of which is shown in [Fig. 1B]. The stator body 30A includes pole teeth 32, each separated by a plurality of slots 33. The stator 3A includes a stator winding 31 wound within the stator body 30A, a portion of which is shown in [Fig. 1C].

[0044] The axial flux electric machine 1A comprises a rotor 2A comprising a ferromagnetic body 20A, also referred to hereafter as the rotor body, made of a single, monobloc piece. The ferromagnetic body 20A comprises pole teeth 22, each separated by a plurality of notches 23.

[0045] The rotor winding 21 and stator winding 31 each comprise a winding per pole tooth 22, 32 of the rotor body 20A and stator body 30A respectively. In [Fig. 1A] the tangent section is shown at three teeth 22, 32 of each ferromagnetic body 20A, 30A and of the conductors of the rotor winding 21 and the stator winding 31.

[0046] The rotor 2A comprises a rotor winding 21 wound in the ferromagnetic body 20A. The ferromagnetic body 20A according to this first example is schematically represented in [Fig. 1D] with a stator body according to a second example of this embodiment. The number of teeth 22 of the rotor body 2A may be greater than, equal to, or less than the number of teeth 32 of the stator body 3A

[0047] In this first example, the rotor 2A comprises a lower number of pole teeth 22 and rotor windings 21 than that of the stator 3A. In this first example, the ferromagnetic body 20A of the embodiment can be similar to that of [Fig. 1B] with a lower number of teeth.

[0048] According to the second example of this first embodiment of an electric machine, the stator body 30A' has the same number of teeth as the rotor body 20A, the two bodies of which are shown in [Fig. 1D]. The electric machine therefore has the same number of windings in the rotor as in the stator in this second example. In this first embodiment, each ferromagnetic body 20A, 30A includes a yoke 24, 34, in this case disc-shaped, from which the pole teeth 22, 32 extend axially.

[0049] In this example, each ferromagnetic body 20A, 30A comprises a central opening 9 for the axis of rotation; in other words, each yoke 24, 34 comprises a central opening opposite the other. This opening can accommodate a rotating shaft fixed to the ferromagnetic body 20A of the rotor or a fixed shaft fixed to the ferromagnetic body 30A of the stator.

[0050] The machine includes a rotor supply device not shown which may include brushes exerting an axial force against a rotor ring connected to the rotor winding 21 or brushes exerting a radial force against a rotor ring connected to the rotor winding 21.

[0051] The ferromagnetic body 20A of the rotor 2A comprises an external radial end periphery 203, in this case cylindrical in shape, comprising, for each tooth 22, an external radial end surface of a tooth 223 in the shape of a portion of a cylinder and an external radial end surface of a yoke 243 in the shape of a cylinder. The ferromagnetic body 20A of the rotor 2A comprises an internal radial end surface 204, in this case cylindrical in shape, comprising, for each tooth 22, an internal radial end surface of a tooth 224 in the shape of a portion of a cylinder and an internal radial end surface of a yoke 244 in the shape of a cylinder. The notches 23 are radially open on this external radial end periphery 203 and on the internal radial end surface 204.

[0052] The ferromagnetic body 20A of the rotor 2A further comprises an air gap surface 225, extending radially over each tooth 22, facing an air gap surface 325 of the stator 3A. The ferromagnetic body 20A of the rotor 2A further comprises an axial end face 245 having a surface shaped in this example of a disk, opposite the air gap surfaces 225.

[0053] These cylindrical surfaces simplify the balancing of the rotor 2A. According to another example not shown, the ferromagnetic body 20A of the rotor 2A comprises an external radial end periphery 203 and / or an internal radial end periphery 204 of a different shape, for example, different flat surfaces forming an internal or external periphery, respectively, of the rectangular axial end face 245. Such a shape can allow, respectively, either the easy coupling of a functional element of a lathe or a rotor shaft to it in rotation.

[0054] The stator body 30A of the stator 3A has in this example an identical shape to that of the rotor body 20A, namely an internal and external radial end surface of cylindrical shape, but could have a different shape from that of the rotor body 20A.

[0055] The depth Pr of each notch 23 of the rotor body 2A may be greater, equal to or less than the depth Ps of each slot 33 of the stator body 3A, but preferably have the same radial length. The width of each slot 23, 33, measured perpendicular to the depth Ps, Pr, and the radial length, depends on the number of slots 23, 33, the diameter of the ferromagnetic body 20A, 30A, and is regular in this example, but can vary, increasing from the inner diameter to the outer diameter. Thus, in this example, each tooth 22, 32 has a width that increases from the inner diameter to the outer diameter.

[0056] Each pole tooth 22, 32 of each ferromagnetic body 20A, 30A comprises a base 227, 327 extending axially from the yoke 24, 34 comprising two air gap surfaces facing the other ferromagnetic body. In this example, each tooth further comprises two prongs 226a, 226b, 326a, 326b extending from the base 227, 327, each forming a continuation of the air gap surface, towards another prong 226a, 226b, 326a, 326b of an adjacent tooth circumferentially. Each notch 23, 33 is axially delimited by a bottom surface 246 formed by the breech face 24, 34, opposite an axial opening delimited at the level of the two spurs 226a, 226b, 326a, 326b of the two pole teeth 22, 32 adjacent to it. Each notch 23, 33 is radially delimited longitudinally by an external opening and an internal opening. Each notch 23, 33 is delimited widthwise between two lateral surfaces 220, 221, 320, 321 of the two pole teeth 22, 32 defining it.In this example, as described above, the two lateral surfaces 220, 221, 320, 321 delimiting each notch 23, 33 are parallel, but it could be the two lateral surfaces 220, 221, 320, 321 of each pole tooth 22, 32 that are parallel. The opening of the notch 23, 33 includes a width b measured between the two beaks 226a, 226b, 326a, 326b of the two pole teeth 22, 32, which is lower than a filling area of ​​the notch 23, 33.

[0057] A one-piece ferromagnetic body is defined as one that is not assembled from separate parts. The ferromagnetic body can be a machined solid mass or a wound and welded metal strip. For example, a sheet of metal is cut to form the strip; for instance, a punch in the shape of a notch cuts openings in the sheet metal in several successive operations, forming a T-shaped tooth between two successive openings. The end of the strip is then fixed to a hub and wound by rotating the hub. The cutting space is calculated such that the notches in the strip are opposite each other. Thus, the teeth, the jaws, and the yoke are made of the same material and are a single, one-piece component.The rotor winding 21 and the stator winding 31 are described in this example with a single conductor per winding, but they can be wound with two or more conductors connected in series or in parallel. The conductors of the rotor windings can have the same or a different shape than the conductors of the stator windings, for example, having a cylindrical or rectangular cross-section. The conductors of the rotor windings can be made of the same or a different material than the conductors of the stator windings, for example, copper or aluminum.

[0058] Each winding of the rotor winding 21 and each winding of the stator winding 31 comprises a conducting wire having a cross-section here, in this case represented by a circular shape, but could have a rectangular or square cross-section. For example, the same conductor can form different windings of the rotor winding 21 or the stator winding 31. In this example, the cross-section of the conductors in the rotor winding 21 is larger than the cross-section of the conductors in the stator winding 31, but the reverse could be true, and advantageously, they could be identical.

[0059] Each winding of the rotor winding 21 or the stator winding 31 comprises a plurality of turns around the corresponding pole tooth 22, 32. One turn is one revolution of the conductor around the tooth 22, 32. Each turn comprises an active portion housed in a notch delimited by the tooth and another active portion housed in the adjacent notch delimited by the pole tooth 22, 32. In [Fig. 1A], the cross-section is made in the three teeth 22, 32, at the level of the active portions of the turns. Each turn further comprises an outer loop and an inner loop, each connecting the two active portions of the turn outside the notch. The external bun parts of the turns of a winding form an external winding bun 391 of a bun 39 of the stator winding 31, part of which is visible on [Fig.lC].

[0060] Each notch 23, 33 therefore houses active parts of a winding around the tooth 22, 32 defining it and active parts of another winding around the other tooth 22, 32 defining it.

[0061] As can be seen in [Fig. 1 A], each winding comprises a plurality of turns forming a plurality of layers, each layer comprising the active parts aligned between the tip of the corresponding pole tooth and the root surface 246 of the corresponding slot, the layers being superimposed one on top of the other around the corresponding pole tooth. The number of layers in a winding of the rotor winding 21 2A may be equal to, less than, or greater than the number of layers in a winding of the stator winding 31 3A.

[0062] The rotor and / or the ferromagnetic stator body 20A, 30A may include in each slot an insulator (not shown) pressed against the tooth or teeth defining the slot. The insulator may be an insulating body surrounding the tooth or may be an insulating paper inserted into the slot 23 between the bottom surface 246 and the nozzle 226a, 226b, 326a, 326b, running along the two lateral surfaces 220, 221 of the two teeth 22 defining the slot 23. The insulating body may have conductor impressions to guide the conductor during the winding of the turns of the first layer. The bottom of the slot 23 is then formed in this example by a portion of the insulator pressed against the bottom surface 246.

[0063] By rotor winding 21 and stator winding 31, wound in the body of rotor 20A and stator 30A respectively, it is understood that the conducting wire has been wound around the tooth. This is done using a winding machine with a needle that holds the wire. The needle passes through the slot opening between the two jaws to position and place the wire against the tooth, the insulation, or the live parts of the previous layer (NL). The width b must therefore be greater than the width of the needle in the electric winding machine. In this case, the width b of each slot opening 23 of the rotor 2A is the same as the width b of the slot opening 33 of the stator 3A, allowing the same needle in the winding machine to pass through and thus reduce production costs.

[0064] The rotor and stator windings are wound by the same type of winding machine, called a needle winding machine, because the rotor and stator bodies are one piece and the teeth 22, 32 include jaws 226a, 226b, 326a, 326b. Indeed, the fact that the jaws 226a, 226b, 326a, 326b are one piece with the yoke 24, 34 prevents winding a coil beforehand and then inserting it around the tooth 22, 32. The process of winding the coils outside the tooth and then mounting them may be less expensive but requires: • Consider a ferromagnetic body assembled from various mechanical parts, including teeth mechanically mounted on the cylinder head, resulting in assembly play that reduces the electromagnetic performance of the electrical machine, as well as mechanical problems. • Either teeth without beaks leading to problems in retaining conductors in the notch as well as a reduction in the electromagnetic performance of the electrical machine.

[0065] In this example, the winding machine used to wind the rotor windings is the same winding machine used to wind the stator windings. The winding machine needle can be changed if necessary, if it does not fit the cross-section of the rotor and stator conductors.

[0066] In this example, the winding machine winds the conductor around each tooth 22, 32, applying the same force whether in the rotor body 2A or the stator body 3A. Thus, the winding machine winds the conductor, forming the first layer by winding several turns (turns) around each pole tooth 22 of the rotor 2A, for example in contact with an insulating block, applying the same force as when it winds the conductor, forming the turns of the first layer around each pole tooth 32, of the stator 3A, for example in contact with an insulating block. The same applies to the successive layers N+1 on the lower layers NL. By applying the same force, we mean plus or minus 10% due, for example, to a difference in the machine's tolerance settings, for example, related to the width of the tooth 22, 32 or the conductor cross-section.Thus a conductor part of a turn (whether it is an active part or an external or internal bun part) of a . second layer of a winding of the rotor 2A winding includes a winding clamping tension value on the first layer surrounding the pole tooth 22, 32 of the rotor 2A equal to + or - 10% of the winding clamping tension value of the second layer of a stator winding on the first layer surrounding the stator pole tooth.

[0067] Each section of the rotor 2A and stator 3A conductors comprises a layer distance Des, Dcr, corresponding here to the conductor diameter. In the case of a rectangular conductor, depending on its orientation, the layer distance will be the width of the rectangular conductor section if the conductor is positioned with its lateral surface wound, or the length of the rectangular conductor section if the conductor is positioned with its longitudinal surface wound.

[0068] Furthermore, due to the winding tolerance of the machine, the number of turns per layer of a stator winding 3A is equal to the depth Ps of the slot 33 subtracted from a bottom tolerance T1 subtracted from a tip tolerance T2 all divided by the layer distance Des of the stator conductor section Cs.

[0069] Furthermore, due to the winding tolerance of the machine, the number of turns per layer of a winding of the rotor 2A is equal to the depth Pr of the notch 23 of a bottom tolerance T1 subtracted from a tip tolerance T2, all divided by the layer distance Dcr of the rotor conductor section.

[0070] It can be seen that the internal tolerance value T1 between the first turn and the bottom of the slot 23 of the rotor 2A of the first layer of the slot 23 shown in [Fig. 1A] is equal to within 10% of the external tolerance value T2 between the last turn of the first layer and an internal surface of the tooth tip 32 of the stator 3A. This is due in particular to manufacturing tolerances during the winding process of the winding machine. In the case where the tooth is without a tip, the external tolerance value T2 is measured between the air gap surface 225 and the last turn. In other words, the external tolerance T2 is measured between the last or first turn and the surface opposite the bottom of the slot.

[0071] Figure 2A represents an electrical machine IB according to a first example of a second embodiment comprising a stator 3B mounted axially between a first and a second rotor body 20A, 20B of a rotor 2B. The second rotor body 20B is identical to the first rotor body 20A of the first example, as can be seen in Figure 2B, which shows only the two rotor bodies 20A, 20B. The rotor 2B therefore includes a second rotor winding 21B wound in the second rotor body 20B, identical to the first rotor winding 21. In this second embodiment, the stator 3B shown in Figure 2C differs from the stator 3A of the first embodiment in that it includes a stator body 34 shown in Figure 2D, comprising: • a first part of the stator body 34A comprising a number N of teeth 32A, extending axially towards the first rotor body 20A, comprising an air gap surface opposite the first rotor body 20A, • a second stator body part 34B comprising the same number N of teeth 32B, extending towards the second rotor body 20B, comprising an air gap surface 325B opposite the second rotor body 20B, such that each base end of each tooth 32B located opposite the air gap surface 325B of the tooth 32B extends from a base end of a corresponding tooth 32A of the first stator body part 34A.

[0072] In this example each tooth 32A, 32B comprises two beaks as in the example of the first embodiment.

[0073] In this example shown in [Fig. 2C], the stator body 34 consists of a plurality of parts, each formed by different teeth 32A, 32B arranged angularly around an axis forming the central opening 9 of the stator body 34. In this example, the stator body 34' is without a yoke. In this example, the first and second parts are separate pieces; that is, each tooth 3A forming the first part of the stator body 34A is mounted against a tooth 32B forming the second part of the stator body 34B. The stator 3B in this example includes a support (not shown) which can be made by overmolding onto the separate wound or bare parts. According to one embodiment, the support is a solid part comprising recesses housing each stator body part 34A, 34B, each mounted rigidly in a corresponding recess. This part can be made of plastic or composite material.The notches 33A and 33B of each stator body part 34A, 34B can therefore be opened onto each other or closed by the support.

[0074] According to an example of the first embodiment, the stator body 3A is formed by only the first part of the stator body 34A, in other words without a yoke 34.

[0075] According to a second example of this second embodiment, in which the stator body 34' of the stator 3B is shown in [Fig. 2F], the stator body 34' comprises a central disc-shaped yoke 34C. The central yoke 34C is formed by a portion of the first stator body portion 34A' and a second portion of the second stator body portion 34B'. In other words, each stator body portion 34A', 34B' comprises a yoke portion forming the yoke 34C. Each first and second stator body portion, 34A, 34B, is a single piece and can either be mounted against each other, forming the central yoke 34C together, or they can be a single, monolithic piece. In this example, the notches 33A, 33B are therefore closed axially by the cylinder head 34C opposite the air gap surface 325B.

[0076] The teeth 32A, 32B are also T-shaped (i.e., include prongs) in this example, as in the first example. In the following, the electric machine is described using the references of the first example of this second embodiment, but the stator bodies of the first and second examples are interchangeable in these two examples of electric machines of this second embodiment.

[0077] The stator 3B further comprises, in addition to the first stator winding 31A comprising windings wound each around a tooth 32A of the first part of the stator body 34A, a second stator winding 31B comprising windings wound each around a tooth 32B of the second part of the stator body 34B.

[0078] The first rotor winding 21A and the second rotor winding 21B are preferably made respectively in the first and second rotor body 20A, 20B of the rotor 2B by the same needle winding machine.

[0079] The first stator winding 31A and the second rotor winding 31B of the stator 3B are preferably made in the first and second stator body sections 34A and 34B, respectively, by the same needle winding machine. The needle winding machine may be the same as that used to make the first rotor winding 21A and the second rotor winding 21B.

[0080] Each slot 23A, 23B formed between two teeth 22A, 22B of each rotor body 20A, 20B of the rotor 2B includes flat lateral surfaces 220A, 221A, 220B, 22IB, formed by each of the two teeth 22A, 22B forming the slot 23A, 23B in order to increase the percentage of copper in the slot and thus the efficiency of the electric machine. The bottom of the slot formed by the yoke 24A, 24B is also preferably flat. Each notch 33A, 33B formed between two teeth 32A, 32B of each first and second part of stator body 34A, 34B also includes flat lateral surfaces 320A, 321A, 320B, 321B referenced on [Fig.2E], formed by each of the two teeth 32A, 32B forming the notch 33A, 33B.

[0081] According to other examples of this first or second embodiment, of which only two examples of the second embodiment are shown in Figures 3a to 4, the ferromagnetic rotor bodies 20A, 20B are identical to those of the first example except with regard to the yoke 24', 24" which comprises a plurality of radially extending recesses 27A, 27B, 27A', 27B', each situated between two planes, each passing through a flat surface 220A, 221A, 220B, 221B of the same tooth 22A, 22B, and is closer to the external radial surface of the ferromagnetic body 20A, 20B than to a flat surface 220A, 221A, 220B, 221B of the tooth 22A, 22B. In these examples, each body The rotor 20A, 20B includes a recess 27A, 27B, 27A', 27B', per tooth. Preferably, the recesses 27A, 27B, 27A', 27B' are located equidistant from the first and second flat surfaces 220A, 221A of the nearest tooth 22A, 22B. This area where the recess is formed is not or very little crossed by the magnetic field, thus allowing the weight of the rotor bodies 20A, 20B to be reduced without reducing efficiency.

[0082] In the two other examples shown in Figures 3A to 4, each recess 27A, 27B, 27A', 27B' extends from the inner diameter to the outer diameter of the rotor body 20A', 20B', 20A”, 20B” of the rotor 2', 2”. In other words, each recess 27A, 27B, 27A', 27B' is open on the outer periphery of the radial end 203', more precisely on the outer periphery of the radial end of the cylinder head 243, and on the inner periphery of the radial end 204', more precisely on the inner periphery of the radial end of the cylinder head 244'. This allows for cooling of a fluid by centrifugal force.

[0083] In the second example of this second embodiment of an electric machine 1' visible in [Fig. 3A], whose two rotor bodies 20A', 20B' of the rotor 2' are shown in [Fig. 3B], each recess 27A, 27B is axially open on the axial end face 245' of the yoke 24', forming notches. This example reduces the weight compared to the first example while also allowing for the formation of air disturbances to cool the rotor 2', 2" and the stator 3'.

[0084] In the third example of this second embodiment of the electric machine 1”, whose rotor 2” is shown in [Fig. 4], each recess 27A', 27B' are holes radially traversing the yoke 24'', opening only radially on one side outwards and on the other side inwards (towards the axis of rotation). The axial end face 245' of the yoke 24' is therefore, in this example, flat (a disk having a central hole) comprising a circular outer periphery and a circular inner periphery.

[0085] In this second embodiment, according to an example not shown, some or all of the recesses 27A, 27B can house a permanent magnet to increase the performance and efficiency of the electrical machine.

[0086] In this second embodiment, according to an example not shown, some or all of the recesses 27A, 27B can be used to balance the rotor.

[0087] In this second embodiment, according to an example not shown, some or all of the recesses 27A, 27B can be used for fixing to a rotor shaft or to a part of a machine to be driven in rotation.

[0088] According to another embodiment, the rotor in the examples of the second embodiment is a stator and the central stator is a central rotor.

[0089] Unless otherwise specified, the same element appearing on different figures has a unique reference.

Claims

1. Demands Axial flux electric machine (IA, IB, 1', 1") comprising - a rotor (2A, 2B, 2', 2") comprising a ferromagnetic body (20A, 20B, 20A', 20B') made of a single monobloc piece, - a stator (3A, 3B) comprising a ferromagnetic body (30A, 30A', 34), - each ferromagnetic body (20A, 20B, 20A', 20B', 30A, 30A', 34) comprising: • polar teeth (22, 22A, 22B, 32, 32A, 32B) comprising a base (227, 327) extending axially comprising an air gap surface facing the other ferromagnetic body and two lateral flat surfaces (220, 221, 320, 321, 220A, 221A, 320A, 321A, 320B, 321B) opposite each other, each extending axially and radially from the air gap surface of the tooth (22, 22A, 22B, 32, 32A, 32B) to an opposite end of the air gap surface of the base (227, 327), • notches (23, 23A, 23B, 33, 33A, 33B) each formed between two lateral flat surfaces (220, 221, 320, 321, 220A, 221A, 320A, 321A, 320B, 321B) of two circumferentially adjacent teeth (22, 22A, 22B, 32, 32A, 32B), and comprising an axial opening between the two air gap surfaces of the two adjacent teeth (22, 22A, 22B, 32, 32A, 32B), - in which the ferromagnetic body (20A, 20B, 20A', 20B') of the rotor further comprising a yoke (24, 24', 24”, 24A, 24B) comprising a bottom surface (246) axially delimiting the bottom of the notch (23, 23A, 23B, 33, 33A, 33B), - the stator (3A, 3B) and the rotor (2A, 2B, 2', 2") further comprising a winding (21, 31, 21A, 21B, 31A, 31B) comprising a winding per tooth (22, 22A, 22B, 32, 32A, 32B) pole, each winding comprising a conductor wire of which each rotor conductor comprises an identical section (Cr), and each stator conductor comprises an identical section (Cs), forming a plurality of turns around the corresponding tooth (22, 22A, 22B, 32, 32A, 32B), comprising - bun portions outside the two circumferentially adjacent notches (23, 23A, 23B, 33, 33A, 33B) and - active portions each housed in one of the two adjacent notches (23, 23A, 23B, 33, 33A, 33B) of the pole tooth (22, 22A, 22B, 32, 32A, 32B), each connecting two bun portions, forming a plurality of layers each comprising active portions aligned along the lateral flat surface (220A, 221A, 320A, 321A, 320B, 321B) between the air gap surface of the corresponding pole tooth and the opposite end of the base (227, 327),the layers being superimposed one on top of the other around the polar teeth such that the active parts of the last layer face the active parts of a last layer of the neighboring winding in the same notch (23, 23A, 23B, 33, 33A, 33B).

2. An axial flux electric machine (IA, IB, 1', 1") according to the preceding claim, wherein each tooth (22, 22A, 22B, 32, 32A, 32B) comprises two nozzles (226a, 226b, 326a, 326b) forming an extension of the air gap surface (225, 225A, 235, 235A) of the tooth extending towards another nozzle (226a, 226b, 326a, 326b) of a neighboring tooth (22, 22A, 22B, 32, 32A, 32B), the opening of the notch (23, 23A, 23B, 33, 33A, 33B) being formed between the two nozzles.

3. Axial flux electric machine (IA, IB, 1', 1") according to any one of the preceding claims, wherein the conductor portion of a turn of a second layer of a winding of the rotor winding (21) (2A) comprises a winding clamping tension value on the first layer surrounding the rotor pole tooth (22, 22A, 22B) equal to ±10% of the winding clamping tension value of the second layer of a winding of the stator winding (31) on the first layer surrounding the stator pole tooth (32, 32A, 32B).

4. An axial flux electric machine (IA, IB, 1', 1") according to the preceding claim, wherein - each conductor section comprises a layer distance measured along the alignment of the active parts forming a layer, - an internal or external tolerance value Tl, T2 of a rotor winding between the last wound active part of the first layer and respectively the bottom of the slot (23, 23A, 23B) or the surface opposite the bottom of the slot (23, 23A, 23B) of air gap (225B) or a surface is identical to an internal or external tolerance value Tl, T2 of a stator winding, the internal and external tolerance Tl, T2 each being less than a layer distance of the conductor in the slot.

5. An axial flux electric machine (IA, IB, 1', 1") according to the preceding claim, wherein: - in each slot, a total tolerance value is equal to the sum of the internal and external tolerance T1, T2, - the effective depth of each rotor slot subtracted from the total tolerance value is equal to the number of turns of the winding around the tooth (22, 22A, 22B) of the rotor to form a layer multiplied by the layer distance of the conductor cross-section of the rotor winding and - the effective depth of each stator slot subtracted from the total tolerance value is equal to the number of turns of the winding around the tooth (32, 32A, 32B) of the stator to form a layer multiplied by the layer distance of the conductor cross-section of the rotor winding.

6. An axial flux electric machine (1', 1") according to any one of the preceding claims in which the ferromagnetic body of the rotor (20A', 20B') comprises a plurality of recesses (27A, 27A', 27B, 27B') extending radially, closer to the external radial surface of the ferromagnetic body than to a flat surface (220, 221, 320, 321, 220A, 221A) of the tooth (22A, 22B) being opposite a tooth (22A, 22B).

7. Axial flux electric machine (1') according to the preceding claim, wherein the recess (27A', 27B') is an open notch on the external cylindrical surface.

8. Axial flux electric machine (IA, IB, 1', 1") according to any one of the preceding claims, wherein the rotor body (20A, 20B, 20A', 20B') and / or the stator body (30A, 30A', 34) is formed by a ferromagnetic metal strip, comprising notches and teeth, spirally wound to form the rotor body and / or the stator body respectively.

9. Axial flux electric machine (IA, IB, 1', 1”,) according to any one of the preceding claims, wherein the planar surfaces (220A, 221A, 320A, 321A, 320B, 321B) defining a notch ((23, 23A, 23B, 33) are parallel for each notch of each body of the rotor (20A, 20B, 20A', 20B') and of the stator (30A, 30A', 34).

10. An axial flux electric machine (IA, IB, 1”) according to any one of the preceding claims, wherein the ferromagnetic body of the stator is monobloc and includes a yoke (34, 34C) comprising a bottom surface (346) axially delimiting the bottom of the notch (33).

11. An axial flux electric machine (1') according to any one of claims 1 to 9, wherein the ferromagnetic body (34) of the stator (3B) is made up of a plurality of parts each formed by different teeth (32A, 32B).

12. A method for manufacturing an electric machine according to any one of the preceding claims, comprising: - a step of winding the rotor by a needle winder by winding around each pole tooth, an electrical conductor by inserting it through the opening of a notch, and - a step of winding the stator by the same needle winder according to the same winding method as that of the rotor.

13. A manufacturing method according to the preceding claim, wherein the electrical machine is according to claim 10, further comprising: a manufacturing step for the stator body, comprising: • a sub-step of cutting a sheet metal strip, forming notches and teeth between each notch, • a sub-step of attaching one end of the band to a hub • a sub-step of winding the strip around the core of a winding machine forming the stator body, a manufacturing step for the rotor body, comprising: • a sub-step of cutting a sheet metal strip, forming notches and teeth between each notch, • a sub-step of attaching one end of the band to a hub • a sub-step of winding the strip around a core of the winding machine forming the rotor body.

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