Wound rotor of an axial flux synchronous machine

Abstract

One aspect of the invention relates to an axial flux wound rotor (1) comprising at least a first group of a first set of teeth (2s) and a second set of teeth (2n), a winding comprising coils (17) each wound around a tooth of a set, each tooth (2s) of at least the first set comprising at least one housing extending longitudinally radially, open to an air gap surface (25). The rotor (1) comprises a first group of N permanent magnets (4s), each housed in the housing of a corresponding tooth (2s) of the first set of teeth (2s), and is magnetized parallel to the axis of rotation from a first polarity to a second polarity, wherein the pole of each permanent magnet (2s) oriented towards the air gap surface is of the same first polarity. Figure to be published with the abbreviation: Figure 1A

Description

Title of the invention: Wound rotor of an axial flux synchronous machine. TECHNICAL FIELD OF THE INVENTION

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

[0002] The present invention relates to a wound rotor of an axial flux machine. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] For space reasons, there is a need for axial flux machines rather than radial flux machines. Devices exist that include a wound-rotor axial flux machine, which can provide high torque, but the machine has poor efficiency when supplying low torque to the device relative to the maximum torque of the electric machine. For example, for electric vehicles with at least one wheel, such as an electric scooter, when driving or starting on a slight downhill or flat incline, the axial flux machine must provide low torque to propel the vehicle. Permanent magnet axial flux machines are known to be used when this low torque range is required because they provide much higher efficiency than electrically excited synchronous machines (wound rotor) in this range.However, the disadvantage of a permanent magnet axial flux machine compared to an electrically excited (wound) synchronous axial flux machine is its price, its weight at the same power level, and its limited maximum torque, which may be necessary, particularly for starting a vehicle on a positive slope.

[0004] There is therefore a need for an axial flux electric machine which provides better efficiency in the low torque range than an electrically excited synchronous axial flux machine but is less expensive than the permanent magnet axial flux machine. Summary of the invention

[0005] The invention offers a solution to the problems mentioned above, by making it possible to increase the performance of a synchronous electric machine, particularly in the low torque range.

[0006] One aspect of the invention relates to an axial flux wound rotor of an axial flux electric machine comprising: • at least a first group of teeth, twice a number N in number, regularly distributed angularly around an axis of rotation, each tooth being made of soft ferromagnetic material and comprising an axial air gap surface, the first group comprising a first series of N teeth and a second series of N teeth, each tooth of the first series being located angularly between two teeth of the second series, • a notch between each tooth of the first group, • a winding comprising active parts housed in slots, • characterized in that each tooth of the first series comprises at least one housing extending longitudinally radially, open on the air gap surface, and the rotor comprising a first group of N permanent magnets, in which each permanent magnet is housed in the housing of a corresponding tooth of the first series of teeth, and is magnetized parallel to the axis of rotation from a first polarity to a second polarity, in which the pole of each permanent magnet oriented towards the air gap surface is in the same first polarity.

[0007] Thanks to the invention, permanent magnets make it possible to increase the magnetic flux in the same direction in the tooth as that produced in the tooth housing it by supplying the winding with a current flowing in the active parts in the slots adjacent to the tooth housing the permanent magnet. This makes it possible to increase efficiency at low torque since, to produce torque in the low range, the rotor according to the invention consumes less current (or even none if the flux produced by the permanent magnets is sufficient) in its winding thanks to the flux produced by the permanent magnets compared to an axial flux rotor comprising only the same winding. Because the rotor includes a winding, the permanent magnets are less powerful and therefore less expensive than the magnets of a rotor with a magnet of the same power.In this case, for a 75 kW machine, a cost saving of €350 was observed compared to a synchronous machine with a permanent magnet (without windings), and an efficiency gain of 5% for a torque of 100 Nm compared to the same synchronous machine without a permanent magnet and housing. Finally, due to the radial centrifugal force exerted on an axial flux machine, the machine has the advantage of easily resolving the issue of retaining the permanent magnet in its housing. This can be achieved either by having a housing that is radially closed outwards, or, if it is radially open outwards, by adding an external retaining ring, or by having a trapezoidal longitudinal section (parallel to the length of the housing), or by using an epoxy overmolding that bonds the magnet to the housing, or by using a tight fit to increase the coefficient of friction. All these methods of retaining the permanent magnet are simple and inexpensive.

[0008] In addition to the characteristics just mentioned in the preceding paragraph, the rotor according to one aspect of the invention may have one or more complementary characteristics among those described in the following paragraphs, considered individually or according to all technically possible combinations.

[0009] According to one embodiment, each tooth comprises a first and second beak, each partially closing the notch axially with the beak of the neighboring tooth.

[0010] According to one embodiment, each tooth of the second series of the first group comprises a housing extending longitudinally radially, open to the air gap surface, and the rotor comprises a second group of N permanent magnets, each housed in the housing of a corresponding tooth of the second series of teeth, and each magnetized parallel to the axis of rotation from a first polarity to a second polarity, wherein the pole of each permanent magnet oriented towards the air gap surface is of the same second polarity. This makes it possible to increase the torque and reduce torque ripple if the winding is wound around each tooth.

[0011] According to one embodiment, the winding comprises one coil per tooth of the second series, each coil wound around a corresponding tooth of the second series, the winding being devoid of coils around the teeth of the first series. This makes it possible to increase the winding power by increasing the conductor ratio in each slot, since there are only active parts of a coil in each slot, and to reduce torque ripple by mixing the flux on the teeth in the case where the teeth of the second series of teeth lack a housing for a magnet.

[0012] According to one embodiment, each permanent magnet comprises an air gap surface flush with the air gap surface of the tooth housing it. This increases the flux density transmitted by each permanent magnet to the stator.

[0013] According to one embodiment, each permanent magnet of the rotor has the same size / volume and the same magnetic force to within ±10%. This makes it possible to harmonize the flux density transmitted by each permanent magnet to the stator to avoid torque ripples.

[0014] According to one embodiment, the housing is positioned angularly at the center of the tooth housing it.

[0015] According to one embodiment, the housing is radially open on both the internal and external sides, and the permanent magnet extends along the entire length of the opening. This allows the full length of the air gap surface to be used, thereby increasing performance at the same magnet volume compared to a magnet extending only partially along the air gap surface.

[0016] According to one embodiment, the tooth includes a beak. This makes it possible to increase the air gap area and to axially maintain the active parts of the winding in the slot.

[0017] According to one embodiment, the rotor comprises a washer-shaped yoke made of a soft ferromagnetic material, the teeth extending axially from the yoke. The yoke allows the flow to be recirculated from one tooth to another in the same tooth group in the case of a rotor having a single tooth group, and furthermore, in the case of one or two tooth groups, allows the rotor body, comprising the yoke and the teeth, to be made from a spirally stacked sheet metal.

[0018] According to one example of this embodiment, the yoke and teeth are formed from a spirally wound sheet of rolled metal. This simplifies the manufacture of the rotor body and also reduces eddy current losses.

[0019] According to another example, the teeth are made of soft magnetic composites, in particular sintered or machined. This makes it possible to reduce losses at high speed compared to rolled sheets.

[0020] According to one embodiment, a second group of teeth made of soft ferromagnetic material distributed regularly angularly around the axis of rotation, each comprising an axial air gap surface axially opposite an axial surface of a tooth in the first group of teeth, the second group of teeth comprising: • a first series of teeth, each aligned axially with a tooth from the second series of the first group of teeth, • a second series of teeth, each axially aligned with a tooth from the first series of the first group of teeth, each comprising at least one housing extending longitudinally radially open onto the axial air gap surface, • a permanent magnet in each housing of a tooth in the second series of the second group of teeth, each permanent magnet is magnetized parallel to the axis of rotation from a first polarity to a second polarity, in which the polarity of each permanent magnet on the side of the air gap surface of the tooth housing it is of a different polarity to that of the permanent magnet on the side of the air gap surface of the tooth in the first series of the first group of teeth. This allows for a central rotor between two stators. Thus, for the same volume and diameter, a central rotor machine has the advantage of having a single rotor while increasing efficiency and maximum torque compared to a machine with a stator and a rotor. Furthermore, this maximizes efficiency for the same permanent magnet volume compared to a machine with only a single axial air gap.

[0021] According to an example of this embodiment and of the embodiment in which each tooth of the second series of the first group comprises a housing and a permanent magnet in the housing, each tooth of the first series of the second group of teeth includes a housing extending longitudinally radially open on the axial surface and in that the rotor includes a permanent magnet housed in each housing of each tooth of the first series of the second group of teeth, each permanent magnet is positioned by being magnetized parallel to the axis of rotation from a first polarity to a second polarity, in which the polarity of each permanent magnet on the side of the air gap surface of the tooth housing it is of a different polarity to the polarity of the permanent magnet on the side of the air gap surface of the tooth of the first group axially aligned.

[0022] Another aspect of the invention relates to an electrical machine comprising a first rotor according to the first aspect of the invention (with or without one or more features of one or more embodiments described above) and a stator comprising a first group of stator teeth regularly distributed angularly around the axis of rotation X, stator slots between each stator tooth of the first group and a winding in the stator slots, each stator tooth of the first group having a stator air gap surface axially opposite an air gap surface of the rotor.

[0023] According to one embodiment, the machine comprises a second rotor according to the first aspect of the invention (with or without one or more features of one or more embodiments described above), the stator comprising a second group of stator teeth regularly distributed angularly around the axis of rotation X, each stator tooth of the second group having a stator air gap surface axially opposite an air gap surface of the second rotor. This makes it possible to balance the axial forces and increase the efficiency for the same axial and radial dimensions (diameter).

[0024] Another aspect of the invention relates to an electric machine comprising a rotor according to the first aspect of the invention in which the rotor is in the embodiment comprising a second group of teeth, a first stator and a second stator each comprising stator teeth regularly distributed angularly around the axis of rotation X, stator slots between each stator tooth and a winding in the slots, each stator tooth of the first stator having a stator air gap surface axially opposite an air gap surface of the teeth of the first group of the rotor and each stator tooth of the second stator having a stator air gap surface axially opposite an air gap surface of the teeth of the second group of the rotor.

[0025] 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

[0026] The figures are presented for illustrative purposes only and are in no way limiting of the invention.

[0027] [Fig.1A] schematically represents in perspective, a rotor according to an example of a first embodiment.

[0028] [Fig.1B] schematically represents in perspective, the rotor of [Fig.1A] without winding.

[0029] [Fig.2] schematically represents, in perspective, a rotor body according to [Fig.1A],

[0030] [Fig.3A] schematically represents an electrical machine comprising the rotor of [Fig.1A] and a stator.

[0031] [Fig.3B] schematically represents an enlargement of part of an electrical machine comprising the rotor of the [Fig.1B] and a stator.

[0032] [Fig.4A] schematically represents an electrical machine comprising two rotors of the [Fig.1A] and a stator.

[0033] [Fig.4B] schematically represents part of the electrical machine of [Fig.4A].

[0034] [Fig.5A] schematically represents in perspective, a rotor without its winding according to a first example of a second embodiment.

[0035] [Fig.5B] schematically represents in perspective, an axial flux electric machine comprising the wound rotor of the [Fig.5A].

[0036] [Fig.6A] schematically represents in perspective, a rotor without its winding according to the second example of the second embodiment.

[0037] [Fig.6B] schematically represents in perspective, a portion of the rotor of the [Fig.6A] with a coil of the winding.

[0038] [Fig.6C] schematically represents in perspective, an electrical machine comprising two stators and a rotor according to the second example of the second embodiment. DETAILED DESCRIPTION

[0039] The figures are presented for illustrative purposes only and are in no way limiting of the invention.

[0040] [Fig. 1A] shows a schematic representation of an axial flux rotor 1 according to a first example of a first embodiment of an axial flux electric machine M, shown in [Fig. 3A]. The rotor 1 is a wound rotor comprising a winding formed by coils 17 which may be wires with a circular or rectangular cross-section. [Fig. 1B] shows the rotor 1 without windings.

[0041] The rotor 1 comprises a body 12, visible alone in [Fig. 2], comprising in this first embodiment a single first group of teeth 2 comprising a number N of south teeth 2s and a number N of north teeth 2n, i.e., a total of twice a number N of teeth 2. The teeth 2 are regularly distributed angularly around an axis of rotation X and notches 3, each formed between two teeth 2. All the teeth 2s, 2n of one polarity and all the teeth of the other polarity form, respectively, a first and second series of N teeth. In the following example, the first series of teeth 2s comprises the teeth intended to be south-biased by the winding, and the second series of N teeth comprises the teeth intended to be north-biased by the winding, but this could be reversed. Each tooth of a polarity 2s, 2n is located angularly between two teeth of the other polarity, respectively 2n, 2s.

[0042] In this example, the body 12 comprises a washer-shaped yoke 10 and each tooth 2 extends axially from the yoke 10. The yoke 10 thus comprises a plurality of surfaces 13 between each tooth 2, delimiting the axial bottom of each notch 3. Each coil 17 of the winding comprises active parts in each notch 3.

[0043] According to this first example of this embodiment, the winding comprises one coil 17 per tooth 2, i.e., twice N coils 17, each wound around the corresponding tooth 2. Each slot 3 thus accommodates active portions of a coil 17 surrounding a tooth 2 (of one of the two sets of teeth) delimiting it, and active portions of another coil 17 surrounding the other tooth 2 (of the other set) delimiting it. The current flowing in the winding is such that it flows in the active portions of one coil 17 and the active portions of the other coil 17 in the same slot in opposite directions, and flows in series in the active portions of the two other neighboring slots in the opposite direction, forming a north magnetic field on one tooth 2n and a south magnetic field in the other tooth 2s.In other words, one out of every two teeth is north-polarized by the current flowing in the two adjacent notches, and the other teeth are south-polarized by the current flowing in the two adjacent notches.

[0044] According to a second example of this embodiment, not shown, only every other tooth, angularly distributed and therefore having the same polarity (belonging to the same set of teeth), is surrounded by a coil 17 of the winding. In other words, the rotor lacks a coil 17 around the teeth of one of the two sets, for example, the first set of teeth (north or south), and has N coils 17, each wound around a tooth 2 of the second set of teeth (same polarity). Each slot 3 thus houses active parts of a single coil 17 surrounding one of the two teeth 2 delimiting it, in this example not shown, the teeth of the second set 2n. The current flowing in the winding 17 is such that it flows in the active parts in one slot in only one radial direction and in the neighboring slot in the opposite direction.Thus, all the coils 17, by the direction of the current, form a magnetic field of the same polarity, whether north or south, on the corresponding tooth of the second series. In other words, every other tooth is a tooth polarized, for example, north by the current. circulating in the two adjacent notches and the other teeth are south-polarized teeth due to the return of the magnetic field.

[0045] Each tooth 2 is made of a soft ferromagnetic material, such as iron. In this example, the teeth 2 and the yoke 10 are a single piece and are formed from a rolled sheet metal, but could be made of soft magnetic composites, in particular sintered or machined. In other words, the body 12 is a single piece of soft ferromagnetic material.

[0046] According to another example not shown, in which the teeth are made of soft magnetic composites, in particular sintered or machined and are mounted on the breech 10, for example fitted.

[0047] In this example shown, each tooth 2 comprises two beaks 23, each partially closing the notch 3 axially with the beak 23 of the neighboring tooth 2.

[0048] Each tooth 2 comprises an axial air gap surface 25 and each tooth 2 of at least one series of the first group of teeth comprises at least one housing 24 extending longitudinally radially, open on the air gap surface 25 dividing the axial air gap surface 25 into two portions.

[0049] In this example, each tooth 2 comprises a housing 24, shown in [Fig. 2], angularly dividing, in this example, the axial air gap surface 25 into two equal portions. The housing 24 is therefore angularly positioned at the center of the corresponding tooth 2. In this example, all the teeth 2 of the first and second series thus each comprise a housing 24.

[0050] The rotor 1 further comprises at least a first group of N permanent magnets oriented with the same polarity towards the air gap, here in this example of south-polarity permanent magnets 4s, in which each permanent magnet 4s is housed in the housing 24 of a corresponding tooth 2s, 2n of the first series of teeth 2s. Each permanent magnet 4s is positioned in the housing 24 by being magnetized parallel to the axis of rotation X from a first polarity to a second polarity (i.e., by having its polarities in series parallel to the axis of rotation X), in which the pole of each permanent magnet 4s oriented towards the air gap surface 24 is with the same first polarity, here in this case south.

[0051] In this example, the rotor 1 comprises a second group of N permanent magnets 4n, each housed in the housing 24 of a corresponding tooth of the second series of teeth 2n. Each permanent magnet 4n of the second group is also positioned in the housing with its polarities in series parallel to the axis of rotation X, from a first polarity to a second polarity, in which the pole of each permanent magnet 4n oriented towards the air gap surface 24 is in the same second polarity, here in this case north.

[0052] In the case of the example with one tooth out of two wound (the winding comprises only N coils 17 each wound around the same series of teeth), preferably only each unwound tooth can include a housing 24 and the rotor 1 comprises only the first group of magnets housed in the housings of the teeth of the unwound series.

[0053] Preferably, as shown, each permanent magnet 4s, 4n comprises an air gap surface 45 flush with the air gap surface 25 of the tooth 2s, 2n housing it. Each permanent magnet 4s, 4n has the same size / volume and the same magnetic strength plus or minus 5%.

[0054] In this example, each housing 24 opens radially on the internal side (towards the X-axis) and therefore includes an internal radial opening. Optionally, each housing 24, as shown in this example, also opens radially on the external side (opposite the X-axis) and therefore includes an external radial opening. Each housing 24 is thus radially as long as the tooth, thereby maximizing the longitudinal size of the permanent magnet 4s, 4n housed in the housing 24. This can also be advantageous for its radial insertion when the permanent magnet and the tooth have a radial length greater than the diameter of the rotor shaft opening receiving the rotating shaft.

[0055] To resist centrifugal force, each housing 24 and each permanent magnet 4s, 4n can (in the case where the shaft opening has a diameter greater than the length of the magnet or in the case where the permanent magnet can be inserted axially through the axial opening of the housing) have a shape that allows the permanent magnet 4s, 4n to be held radially against each other. For example, the housing 24 has a trapezoidal cross-section in a radial plane (perpendicular to the axis of rotation) whose longer base is on the side of the internal radial opening of the housing 24 and whose shorter base is on the side of the internal radial opening of the housing 24, and the permanent magnet 4s, 4n comes radially outward against the two surfaces extending non-parallel between the two radial openings.

[0056] To resist the axial magnetic force towards the air gap, each housing 24 and each permanent magnet 4s, 4n can have a shape that allows the permanent magnet 4s, 4n to be held axially against each other. For example, the housing 24 has a trapezoidal cross-section in a plane parallel to the X-axis, with its longer base on the side of the bottom of the housing 24 and its shorter base on the side of the axial opening (air gap surface 25) of the housing 24, and the permanent magnet 4s, 4n is axially abutted towards the air gap against the two surfaces extending non-parallel between the bottom and the axial opening.

[0057] The trapezoidal shapes in each of these examples may be regular or not.

[0058] According to another example than those of trapezoidal shapes for centrifugal force or axial force, the housing 24 includes a hole housing a protrusion of the permanent magnet 4s, 4n or of a tab inserted with the magnet retaining the permanent magnet 4s, 4 radially.

[0059] According to one example, the rotor 1 includes a ring surrounding the teeth 2 at the external radial openings to retain the permanent magnets 4s, 4n. In this case each housing and permanent magnet 4s, 4n can have the shape of a rectangular parallelepiped.

[0060] Each permanent magnet 4s, 4n can have the same shape and volume as the corresponding housing 24 so as to fill the housing. Each permanent magnet 4s, 4n can be press-fitted (negative clearance) into the corresponding housing 24 to be held in place.

[0061] A resin can be overmolded on the permanent magnet 4s, 4n before or after its insertion into the housing 24 to hold the permanent magnet 4s, 4n in the corresponding housing 24.

[0062] The electric machine M represented in [Fig.3A], comprises a stator 5 in addition to the rotor 1 according to the first example of the first embodiment.

[0063] Fig. 3B represents a portion of a synchronous electric machine without windings, comprising a stator 5 and a rotor 1 according to the first embodiment. The stator 5 in this example comprises a single (first) group of stator teeth 52 regularly distributed angularly around the axis of rotation X, stator slots 53 between each stator tooth 52 of the first group, and a winding 57 comprising active parts in the stator slots 53. The stator 5 in this example comprises a stator body including the stator teeth 52 and a yoke 50 including an internal surface from which each stator tooth 52 extends axially towards the rotor 1 and forming the bottom of each stator slot 53. The stator body can be manufactured in one of the ways mentioned for the rotor body of the rotor 1, that is, either formed from rolled sheet metal or from soft magnetic composites, in particular sintered or machined.Each stator tooth 52 has a stator air gap area axially opposite a rotor air gap area. In this example, the stator has more than twice the number N of a series of teeth 2s, 2n (i.e., more than the number 2 of teeth in the first group of rotor 1). Both rotor 1 and stator 5 have an internal central opening. This opening can accommodate a shaft that rotates directly with the rotor or an electronic power and / or control unit to supply power to the coils 17 and the winding 57.

[0064] According to another electrical machine M' shown in figures 4A and 4B, of which the winding 57 and the coils 17 are not shown, comprising two rotors lb 12 according to the first embodiment described and a central stator 5' located axially between the two rotors lb 12 The index of the rotor references indicates the first or second rotor h, 12.

[0065] The central stator 5' here comprises a second group of stator teeth 52' regularly spaced angularly around the axis of rotation X. In this example, the central stator 5' is without a yoke but could include one. Each stator tooth 52' of the second group is axially aligned with a stator tooth 52 of the first group, together forming a pair. A line represents the boundary between two stator teeth 52, 52' of an axially assembled pair, but each pair of stator teeth 52, 52' can be a single piece. The assembly can be achieved by welding, for example, or by interlocking, for example, a male and female dovetail joint. In the case of a single-piece pair, the boundary between the two axially aligned stator teeth 52', 52' is the radial plane located midway between the two stator air gap surfaces of each stator tooth 52, 52' of the pair.The stator air gap surface of each tooth 52' of the second group of teeth is axially opposite an air gap surface of a tooth 22 of the second rotor 12.

[0066] The first rotor 1 and the second rotor 12 are rotationally fixed to each other and are angularly positioned such that a tooth 2si of the first series of the first group of the first rotor 1 is opposite a tooth 2n2 of a second series of the first group of the second rotor 12. The tooth 2ni of the second series of the first group of the first rotor 1 is opposite a tooth 2s2 of the first series of the first group of the second rotor 12. Thus, each permanent magnet 4si of the first group of the first rotor is axially aligned with a permanent magnet 4ni of the second group of the second rotor 12, and each permanent magnet 4ni of the second group of the first rotor is axially aligned with a permanent magnet 4si of the first group of the second rotor 12.

[0067] In [Fig. 4B], the magnetic fluxes of a portion of the electrical machine of [Fig. 4A] are represented by arrows. These fluxes are produced by the winding (not shown in this figure) of each rotor b 12, by the winding 57 (not shown in this figure) of the central stator 5', and by the two groups of permanent magnets 4sb, 4nB of the first rotor b and the two groups of permanent magnets 4s2, 4n2 of the second rotor 12. The supply to the winding 57 of the stator 5' changes according to the angular position of the two rotors sb, 12 so that the direction of the flux produced by each coil is at its maximum, corresponding to the direction of the fluxes of the two groups of permanent magnets 4sb, 4ni, 4s2, 4n2 of the two rotors b, b.

[0068] Figure 5A represents a first example of a second embodiment of a central rotor 1' identical to the rotor 1 of the first embodiment except in this which relates to the characteristics described below. The central rotor 1' further comprises a second group of teeth 2', made of soft ferromagnetic material, regularly distributed angularly around the axis of rotation. Each tooth 2' of this second group has an axial air gap surface 25' axially opposed to an axial surface 25 of a tooth 2 of the first group of teeth 2. The second group of teeth 2' comprises, like the first group, on the one hand, a first series of teeth 2s', each axially aligned with a tooth 2n of the second series of teeth of the first group of teeth 2, and on the other hand, a second series of teeth 2n', each axially aligned with a tooth 2s of the first series of teeth of the first group of teeth 2. Each tooth 2' of the second group includes those of the first group, with at least one housing extending longitudinally radially open onto the air gap surface 25'.The rotor 1' further includes a permanent magnet 4n' in each housing of the second set of teeth 2n'. In this example, since the rotor 1 of the first embodiment includes a second group of magnets 2s, the rotor 1' in this example includes a permanent magnet 4s' in each housing of the first set of teeth 2s' of the second group.

[0069] Each permanent magnet 4n', 4n, 4s', 4s is positioned in the corresponding housing with a first polarity in series with a second polarity along a direction parallel to the axis of rotation. The polarity (here north) of each magnet 4n' on the side of the air gap surface 25' of the second series of teeth 2n' of the second group of teeth 2' is of different polarity (here north) to the polarity (here south) of the permanent magnet 2s on the side of the air gap surface 25 of the first series 2s of the first group of teeth 2.

[0070] In this example, the polarity (here south) of each magnet 4s' on the side of the air gap surface 25' of the first series of teeth 2s' of the second group of teeth 2' is of different polarity (here south) to the polarity (here north) of the permanent magnet 2n on the side of the air gap surface 25 of the second series 2n of the first group of teeth 2.

[0071] In this first example of this second embodiment, the central rotor 1' comprises a washer-shaped yoke 10' from which extend, on one side, the teeth 2 of the first group of teeth 2 and, on the other side, the teeth 2' of the second group of teeth 2. Hereafter, a pair of teeth 2,2' designates a tooth 2 of the first group axially aligned (that is, a straight line parallel to the axis of rotation passes through the two teeth 2, 2' and their air gap surfaces) with a tooth 2' of the second group (on the other side). Thus, there are pairs of teeth 2s, 2s' of the first series and pairs of teeth 2n, 2n' of the second series. The rotor body of rotor 1', comprising the tooth pairs 2, 2' and the yoke 10', according to this example, is a single piece and can be made by winding (spiraling) a rolled sheet as in the first example of the first embodiment or may be in soft magnetic composites, in particular sintered or machined.

[0072] The rotor 1' comprises a winding including coils 17, 17' shown in [Fig. 5B] representing an electrical machine M” comprising the wound rotor 1' and a first and second stator 51 52. The winding comprises two coils, 17, 17' per tooth pair 2, 2', of which a first coil 17 is wound around tooth 2 of the first group and a coil 17' is wound around tooth 2' of the second group of the same tooth pair 2, 2'. Each coil 17, 17' forms an external and internal winding that may include a portion radially covering the yoke 10' and thus touch the winding of the coil covering the other tooth 2', 2 of the same tooth pair. A small dashed line represents the separation between each first and second coil 17, 17', each wound around a tooth 2, 2', from the same pair.

[0073] According to a first winding example, the coil 17 around the tooth 2 of the first group is in electrical series with the coil 1' around the tooth 2' of the second group of the same pair of teeth 2, 2'.

[0074] According to a second winding example, the coils 17 around each tooth 2s of the first series of the first group are in series together, forming a first group of a first series of coils 17, which are in series with a second group of a first series of coils 17', each around a tooth 2s' of the first series of the second group. The same applies to the coils 17, 17' wound around the teeth 2n, 2n' of each pair of the second series.

[0075] According to another example, the rotor winding comprises only coils 17, 17' around each tooth of the pair of a first series or (exclusively) of the second series. Thus, in this example, each slot houses only the active parts of a single coil 17, 17'.

[0076] According to another example, the rotor winding comprises only coils 17 around one series of the first group of teeth and coils 17' around the other series of the second group of teeth. Thus, each notch formed between two teeth of the first group houses only the active parts of a single coil 17 around one series of teeth (south or north), and each notch formed between two teeth of the first group houses only the active parts of a single coil 17 around another series of teeth (north or south, respectively).

[0077] According to another example, shown in Figures 6A to 6C, of ​​this second embodiment, the rotor 1” is identical to the first example except that it lacks the yoke 10' of the first example. This rotor 1” thus comprises two N pairs of teeth 2p, each comprising one tooth 2 from the first group and one tooth 2' from the second group. Each tooth 2, 2' in this example comprises a housing for a permanent magnet 4n, 4s, 4n', 4s', as in the first example. Each pair The 2p teeth can be monobloc and made of soft magnetic composites, notably sintered or machined. The notch 3 formed between two teeth 2n, 2s of the first group of teeth 2 is therefore open to the notch 3' formed between two teeth 2n', 2s' of the second group of teeth 2'.

[0078] In this example, the rotor 1” comprises a winding including coils (not shown) wound around each tooth 2, 2'. The winding may be according to the first winding example explained previously and preferably according to a second winding example. In this second winding example, shown schematically in [Fig. 0A], representing a coil 17' wound on a pair of teeth 2, 2' of the rotor 1” of the second example of the second embodiment, the rotor 1” has a single coil 17 per pair of teeth 2, 2' comprising N layers of loops (or turns) electrically connected in series.The loops of a layer being aligned axially around the tooth pair 2, 2', each comprising an active part in one notch and an active part in the other notch delimited by the tooth pair 2, 2', each layer comprising a first group of loops around a tooth 2 of the first group, in electrical series with a second group of loops of the layer around the tooth 2' of the second group of the same tooth pair 2, 2'.

[0079] The [Fig.ôB] represents an axial flux electric machine M”' comprising the rotor 1” of the [Fig.ôA] with its winding and a first and second rotor 5b 52 identical to those of the electric machine M' ' each identical to the stator 5 of the electric machine M according to the first example of the first embodiment.

[0080] Unless otherwise specified, the same element appearing on different figures has a unique reference.

Claims

1.

2. Demands Axial flux wound rotor (1, 1', 1") of an axial flux electrical machine (M, M', M", M'") comprising: - at least a first group of teeth (2) in number twice a number N, regularly distributed angularly around an axis of rotation, each tooth (2) being made of soft ferromagnetic material and comprising an axial air gap surface (25), the first group comprising a first series of N teeth (2s) and a second series of N teeth (2n), each tooth (2s) of the first series being located angularly between two teeth (2n) of the second series, - a notch (3) between each tooth (2) of the first group, - a winding comprising active parts housed in the notches (3), - Characterized in that each tooth (2s) of the first series comprises at least one housing (24) extending longitudinally radially, open on the air gap surface (25), and the rotor (1, 1', 1") comprising a first group of N permanent magnets (4s), in which each permanent magnet (4s) is housed in the housing of a corresponding tooth (2s) of the first series of teeth (2s), and is magnetized parallel to the axis of rotation from a first polarity to a second polarity, in which the pole of each permanent magnet (2s) oriented towards the air gap surface is in the same first polarity. Axial flux wound rotor (1, 1', 1") according to claim 1, wherein each tooth (2n) of the second series of the first group comprises a housing (24) extending longitudinally radially, open on the air gap surface (25), and the rotor (1, 1', 1") comprising a second group of N permanent magnets (4n), each housed in the housing (24) of a corresponding tooth (4n) of the second series of teeth (4n), and each magnetized parallel to the axis of rotation (x) from a first polarity to a second polarity, wherein the pole of each permanent magnet (4n) oriented towards the air gap surface (24) is in the same second polarity.

3. Axial flux wound rotor according to claim 1 or 2, wherein the winding comprises a coil (17, 17') per tooth (2n) of the second series each wound around a corresponding tooth (2n) of the second series, the winding being devoid of coil around the teeth (2s) of the first series.

4. Axial flux wound rotor (1, 1', 1") according to any one of the preceding claims, wherein each magnetic permanent magnet (4n, 4s, 4n', 4s') comprises an air gap surface flush with the air gap surface (25, 25') of the tooth (2, 2') housing it.

5. Axial flux wound rotor according to any one of the preceding claims, wherein each permanent magnet (2n, 2s, 2n', 2s') of the rotor (1, 1', 1”) has the same size / volume and the same magnetic strength to plus or minus 10%.

6. Axial flux wound rotor according to any one of the preceding claims, comprising a washer-shaped yoke (10, 10') made of soft ferromagnetic material, the teeth (2, 2') extending axially from the yoke (10, 10').

7. Axial flux wound rotor according to the preceding claim, wherein the yoke (10, 10') and the teeth (2, 2') are formed from a spirally wound rolled sheet.

8. Axial flux wound rotor according to any one of the preceding claims 1 to 6, wherein the teeth (2, 2') are made of soft magnetic composites, in particular sintered or machined.

9. Axial flux wound rotor (1') according to any one of the preceding claims, further comprising: - a second group of teeth (2') made of soft ferromagnetic material regularly distributed angularly around the axis of rotation (x), each comprising an axial air gap surface (25') axially opposed to an axial surface (25) of a tooth (2) of the first group of teeth, the second group of teeth (2') comprising: • a first series of teeth (2s'), each axially aligned with a tooth (2n) of the second series of the first group of teeth (2), • a second series of teeth (2n') each aligned axially with a tooth (2s) of the first series of the first group of teeth (2), each comprising at least one housing extending longitudinally radially open on the axial air gap surface (25'), - a permanent magnet (4n') in each housing of a tooth (2n') of the second series of the second group of teeth (2'), each permanent magnet (4n') is magnetized parallel to the axis of rotation from a first polarity to a second polarity, in which the polarity of each permanent magnet (4n') on the side of the air gap surface (25') of the tooth (2n') housing it is of a different polarity to that of the permanent magnet (4s) on the side of the air gap surface (25) of the tooth (2s) of the first series of the first group of teeth (2).

10. Axial flux wound rotor according to claim 9 and claim 2, wherein each tooth (2s') of the first series of the second group of teeth (2') comprises a housing extending longitudinally radially open on the axial surface and in that the rotor comprises a permanent magnet (4s') housed in each housing of each tooth (2s') of the first series of the second group of teeth (2'), each permanent magnet (4s') is positioned by being magnetized parallel to the axis of rotation from a first polarity to a second polarity, wherein the polarity of each permanent magnet (4s') on the side of the air gap surface (25') of the tooth (2s') housing it is of different polarity to the polarity of the permanent magnet (4n) on the side of the air gap surface (25) of the tooth (2n) of the first group (2) axially aligned.

11. Electric machine (M, M') comprising a first rotor (1) according to any one of the preceding claims 1 to 9 and a stator (5) comprising a first group of stator teeth (52) regularly distributed angularly around the axis of rotation X, stator slots (53) between each stator tooth (52) of the first group and a winding in the stator slots (53), each stator tooth (52) of the first group having a stator air gap surface axially opposite an air gap surface (25) of the rotor (1).

12. Electric machine (M') according to the preceding claim comprising a second rotor (12) according to any one of the preceding claims 1 to 8, the stator (5') comprising a second group of stator teeth (52') regularly distributed angularly around the axis of rotation X, each stator tooth (52') of the second group having a stator air gap surface axially opposite an air gap surface of the second rotor (12).

13. An electric machine (M”, M”') comprising a rotor according to claim 9 or 10, comprising a first stator and a second stator each comprising stator teeth regularly distributed angularly around the axis of rotation X, stator slots between each stator tooth and a winding in the slots, each stator tooth of the first stator having a stator air gap surface axially opposite an air gap surface of the teeth of the first group of the rotor and each stator tooth of the second stator having a stator air gap surface axially opposite an air gap surface of the teeth of the second group of the rotor.

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