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 series of teeth (2s) and a second series of teeth (2n), and a winding comprising coils (17), each wound around a tooth of one of the series, each tooth (2s) of at least the first series comprising at least one recess which extends longitudinally in a radial direction and opens onto an air gap surface (25). The rotor (1) comprises a first group of N permanent magnets (4s), each of which is housed in the recess 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, wherein the pole of each permanent magnet (2s) oriented towards the air gap surface has the same first polarity.

Description

DESCRIPTION TITLE: 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] Due to space constraints, axial flux machines are often preferred over radial flux machines. Some devices incorporate a wound-rotor axial flux machine, which can deliver high torque, but the machine's efficiency is poor when providing low torque relative to the maximum torque of the electric motor. For example, in electric vehicles with at least one wheel, such as electric scooters, 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 offer significantly higher efficiency than electrically excited synchronous machines (wound rotor) in this range.However, the disadvantage of a permanent magnet axial flux machine compared to the electrically excited (wound) synchronous axial flux machine is its price, its weight at the same power and its limited maximum torque which may be necessary, in particular for starting a vehicle on a positive slope.

[0004] Therefore, there is a need for an axial flux electric machine that 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 enabling the performance of a synchronous electric machine to be increased, particularly in the low torque range.

[0006] One aspect of the invention relates to an axial flux wound rotor of an axial flux electrical machine comprising: at least a first group of teeth, twice a number N, 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 situated 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 increase the magnetic flux in the same direction in the tooth as that produced in the tooth housing the permanent magnet. This is achieved by supplying the winding with a current flowing through the active parts in the slots adjacent to the tooth housing the permanent magnet. This increases efficiency at low torque levels because, 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 consisting solely of the same winding. Because the rotor includes a winding, the permanent magnets are less powerful and therefore less expensive than the magnets in a rotor with a single magnet of the same power.In this case, for a 75 kW machine, a cost saving of €350 was found compared to a synchronous machine with a 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 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 mentioned in the preceding paragraph, the rotor according to one aspect of the invention may have one or more complementary characteristics from 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 adjacent tooth.

[0010] In one embodiment, each tooth in 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 in 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 facing the air gap surface is in the same second polarity. This allows for increased torque and reduced torque ripple if the winding is wound around each tooth.

[0011] In one embodiment, the winding comprises one coil per tooth of the second series, each coil wound around a corresponding tooth of the second series, while the winding has no coil around the teeth of the first series. This increases the winding power by increasing the conductor density in each slot, since only active portions of a coil are present in each slot, and reduces torque ripple. by mixing the flux on the teeth in the case where the teeth of the second set of teeth lack a housing for a magnet.

[0012] In one embodiment, each permanent magnet has an air gap surface that is 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 strength to within ±10%. This allows the flux density transmitted by each permanent magnet to the stator to be harmonized in order to avoid torque ripples.

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

[0015] In 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] In one embodiment, the tooth includes a beak. This increases the air gap area and axially maintains the active parts of the winding in the slot.

[0017] In one embodiment, the rotor comprises a washer-shaped yoke made of a soft ferromagnetic material, with the teeth extending axially from the yoke. The yoke allows the flux to be recirculated from one tooth to another within the same tooth group in the case of a rotor with 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 constructed from a spirally stacked sheet metal.

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

[0019] In another example, the teeth are made of soft magnetic composites, notably sintered or machined. This reduces losses at high speed compared to rolled sheets.

[0020] According to one embodiment, a second group of teeth made of soft ferromagnetic material, regularly distributed 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 on the axial gap surface, a permanent magnet in each housing of a tooth of 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 of 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 allows for maximizing 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 comprises a housing extending longitudinally radially open on the axial surface, and in that the rotor comprises a magnet 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 aligned axially.

[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 to the invention.

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

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

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

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

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

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

[0033] [Fig. 4B] schematically represents part of the electrical machine in Figure 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 including the wound rotor of figure 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 figure 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 to 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 Figure 3A. The rotor 1 is a wound rotor comprising a winding formed by coils 17 which can be wires with a circular or rectangular cross-section. Figure 1B shows the rotor 1 without windings.

[0041] The rotor 1 comprises a body 12, visible alone in Figure 2, which in this first embodiment includes a single first group of teeth 2 comprising N southbound teeth 2s and N northbound teeth 2n, i.e., twice N teeth 2. The teeth 2 are regularly spaced angularly around an axis of rotation X and slots 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 southbound by the winding, and the second series of N teeth comprises the teeth intended to be northbound by the winding, but this could be reversed. Each tooth of polarity 2s, 2n is located angularly between two teeth of the other polarity, respectively 2n, 2s.

[0042] In this example, the body 12 includes a washer-shaped yoke 10 and each tooth 2 extends axially from the yoke 10. The yoke 10 thus includes a plurality of surfaces 13 between each tooth 2, delimiting the axial bottom of each notch 3. Each coil 17 of the winding includes 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 the active parts of a coil 17 surrounding a tooth 2 (of one of the two sets of teeth) defining it, and the active parts of another coil 17 surrounding the other tooth 2 (of the other set) defining it. The current flowing in the winding is such that it flows in the active parts of one coil 17 and the active parts of the other coil 17 in The same notch, but in a different direction, circulates in series through the active parts of the two other neighboring notches 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, every other tooth is north-polarized by the current flowing through the two neighboring notches, and the other teeth are south-polarized by the current flowing through the two neighboring 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 that define 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 of 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 polarized, for example, north by the current flowing in the two adjacent slots, and the other teeth are south-polarized by 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 of metal, but could be made of soft magnetic composites, such as 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 includes two beaks 23, each partially closing the notch 3 axially with the beak 23 of the neighboring tooth 2.

[0048] Each tooth 2 includes an axial air gap surface 25 and each tooth 2 of at least one series of the first group of teeth includes 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 includes a housing 24, shown in Figure 2, which angularly divides the axial air gap 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 in the first and second series each include 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 permanent magnets of south polarity 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 (that is to say 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 surface of the air gap 24 is with the same first polarity, here in this case south.

[0051] In this example, the rotor 1 includes 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 according to the same second polarity, here in this case north.

[0052] In the case of the example with every other tooth wound (the winding includes 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 includes 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 inner 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 outer side (opposite the X-axis) and therefore includes an external radial opening. Each housing 24 is thus radially as long as the tooth that maximizes the longitudinal length 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 that receives the rotating shaft.

[0055] To resist centrifugal force, each housing 24 and each permanent magnet 4s, 4n can (in cases where the shaft opening has a diameter greater than the magnet's length, or where the permanent magnet can be inserted axially through the housing's axial opening) 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), with its longer base on the side of the internal radial opening of the housing 24 and its shorter base on the side of the internal radial opening of the housing 24. The permanent magnet 4s, 4n then comes to a radially outward abutment against the two non-parallel surfaces extending 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 comes to rest axially against 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 or may not be regular.

[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 a rectangular parallelepiped shape.

[0060] Each permanent magnet 4s, 4n can have the same shape and volume as its corresponding housing 24 so as to fill the housing. Each permanent magnet 4s, 4n can be press-fitted (negative clearance) into its 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 electrical machine M shown in figure 3A includes a stator 5 in addition to the rotor 1 according to the first example of the first embodiment.

[0063] Figure 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 to say, 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 surface axially opposite a rotor air gap surface. In this example, the stator comprises a number of stator teeth 52 greater than twice the number N of a series of teeth 2s, 2n (i.e., more than the number of teeth 2 of the first). (rotor group 1). The rotor 1 and the stator 5 each have an internal central opening. This opening can allow the insertion of a shaft fixed to the rotor for rotation or an electronic power and / or control unit to control the power supply to the coils 17 and the winding 57.

[0064] According to another electrical machine M' shown in figures 4A and 4B, whose winding 57 and coils 17 are not shown, comprising two rotors 11, 12 according to the first embodiment described and a central stator 5' located axially between the two rotors 1i, I2. The index of the rotor references indicates the first or second rotor 1i, I2.

[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 2m 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 5'. Thus, each permanent magnet 4si of the first group of the first rotor 11 is axially aligned with a permanent magnet 4m of the second group of the second rotor 12, and each permanent magnet 4m of the second group of the first rotor 11 is axially aligned with a permanent magnet 4si of the first group of the second rotor 12.

[0067] Figure 4B shows with arrows the magnetic fluxes of a part of the electrical machine of Figure 4A, produced by the winding (not shown in this figure) of each rotor 1i, 12, by the winding 57 (not shown in this figure) of the central stator 5', as well as by the two groups of permanent magnets 4si, 4m, of the first rotor 1i 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 s11, 12 so that the direction of the flux produced by each coil is at its maximum in accordance with the direction of those of the two groups of permanent magnets 4si, 4m, 4s2, 4n2, of the two rotors 11, 12.

[0068] Figure 5A shows a first example of a second embodiment of a central rotor 1' identical to the rotor 1 of the first embodiment except for the features described below. The central rotor 1' further comprises a second group of teeth 2', made of soft ferromagnetic material, distributed regularly 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 series 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 series of teeth 2s' of the second group.

[0069] Each permanent magnet 4n', 4n, 4s', 4s is positioned in its 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 a different polarity (here north) to the polarity (here south) of the magnet. permanent 2s 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 set 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 set 2n of the first group of teeth 2.

[0071] In this first example of the 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 aligned axially (that is, a straight line parallel to the axis of rotation passes through both 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 the rotor 1' comprising the tooth pairs 2, 2' and the yoke 10', according to this example is monobloc and can be made by winding (spiral) a rolled sheet as in the first example of the first embodiment or can be made of soft magnetic composites, in particular sintered or machined.

[0072] The rotor 1' comprises a winding consisting of coils 17, 17' shown in Figure 5B, which depicts 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', with a first coil 17 wound around tooth 2 of the first group and a coil 1T 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 touching 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' of the same tooth 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] In another example, the rotor winding comprises only coils 17, 17' around each tooth of the pair in either the first series or (exclusively) 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 pair comprising one tooth 2 from the first group and one tooth 2’ from the second group. Each tooth 2, 2’ in this example includes a housing for a permanent magnet 4n, 4s, 4n’, 4s’, as in the first example. Each pair of teeth 2p can be one-piece and made of soft magnetic composites, in particular 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” includes a winding comprising coils (not shown) wound around each tooth 2, 2'. The winding can be according to the first winding example explained previously, and preferably according to a second winding example. This second winding example, shown schematically in Figure 6A, represents 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) in electrical series. The loops of a layer being axially aligned around the pair of teeth 2, 2', each comprising an active part in one notch and an active part in the other notch delimited by the pair of teeth 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 pair of teeth 2, 2'.

[0079] Figure 6B represents an axial flux electric machine M'" comprising the rotor 1" of Figure 6A with its winding and a first and second rotor 5i, 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

DEMANDS

1. 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 slots (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.

2. 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, 11”) 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 within ±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: o a first series of teeth (2s') each aligned axially with a tooth (2n) from the second series of the first group of teeth (2), o 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 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 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 wherein 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. An electrical 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 about 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 (I2) 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 (I2).

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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