Axial flux inductor of a synchronous electric machine

Abstract

One aspect of the invention relates to an inductor (I) of a synchronous axial flux electric machine (M1'), wherein the inductor (I) comprises a first series of salient poles (1) and a second series of salient poles (1, 2) each located between two salient poles (1) of the first series, wherein each salient pole comprises a coil body (21) and an excitation coil (22) of the second series of salient poles (2) comprises windings wrapped around a covered wound portion (210) of the coil body (21) to form active portions in at least one portion of each slot (3) on either side of the coil body (21) formed between a bare portion (11n) of a base (11) of a neighbouring pole of the first series and the coil body, such that the last winding is closer to each of the two neighbouring bare portions (11n) than to the coil body.

Description

DESCRIPTION TITLE: Axial flux inductor of a synchronous electrical machine TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of axial flux synchronous electrical machines, in particular the axial flux inductor.

[0002] The present invention relates to the axial flux inductor and in particular to different embodiments of axial flux synchronous electrical machines comprising such an axial flux inductor. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Like any electric motor, a synchronous machine comprises a rotor and a stator; primarily, the rotor forms the field winding and the stator forms the armature. In the prior art, synchronous electric machine field windings are known to be wound and / or magnetic. A wound field winding can have an advantage. Indeed, a machine with a wound iron core can produce a higher magnetic flux density than a machine with a magnetic core, which is also more expensive and thermally limited by its characteristics compared to a coil. Thus, for the same volume, a synchronous electric machine with a magnetic field winding will be more expensive, more thermally limited, and less efficient (torque), particularly at high rotational speeds, compared to an electric machine with a wound field winding.

[0004] It is also known primarily for two large families of air gaps in electrical machines.

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

[0006] A second family of synchronous electric machines is the axial air-gap type, whose flux is primarily axial, also called an axial field type, and whose air gap volume between a stator comprising coils forming the armature and the rotor forming the field winding (magnetic or wound) is in the shape of a disk perpendicular to the axis of rotation of the rotor.

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

[0008] The advantage of axial air gap machines is that they utilize the maximum machine diameter for the air gap area; the larger the effective air gap diameter, the greater the torque. Furthermore, these machines can also be chosen for their significantly smaller axial footprint compared to radial air gap machines, which have the advantage of a larger radial footprint.

[0009] There are also salient pole or claw inductor rotors.

[0010] Claw rotors consist of a single coil wound around the shaft of rotation, passing through the claws. This allows for high ampere-turns produced by this coil passing through each pole, which has the advantage of improving the conductor-per-slot ratio and thus increasing torque, as well as reducing Joule losses. However, the disadvantage is that the claws are subjected to a concentration of strain stress at their base due to centrifugal force, necessitating a sufficiently large air gap, within the manufacturing tolerances of the armature's internal diameter and the external diameter of the claws. The larger the air gap, the lower the performance of the synchronous electric machine. Furthermore, these claws have the disadvantage of leakage fluxes that do not pass through the air gap, thus not contributing to torque delivery.

[0011] Among synchronous machines, there is the electric machine with a salient-pole inductor comprising a ferromagnetic frame, a plurality of ferromagnetic elements distributed angularly extending axially from the frame, and one coil per ferromagnetic element. Each coil is wound around one of the ferromagnetic elements.

[0012] Therefore, there is a need for a simpler-to-manufacture synchronous electric machine architecture with an axial flux wound inductor to reduce costs while improving efficiency and torque. SUMMARY OF THE INVENTION

[0013] The invention offers a solution to the problems mentioned above, by allowing an excitation coil surrounding part of a coil body to have more turns than in the prior art.

[0014] One aspect of the invention relates to an inductor of an axial flux synchronous electric machine, the inductor being of the salient pole type comprising: a first series of salient poles each comprising a ferromagnetic base regularly distributed angularly around the central axis, and a beak extending from the ferromagnetic base comprising a radial axial air gap surface, each ferromagnetic base comprising at least one bare part, a second series of salient poles, each located between two salient poles of the first series, each salient pole of the second series comprising at least: a coil body comprising a wound covered part, an excitation coil wound around the wound covered part of the coil body, a radial axial air gap face.notches, each formed between a coil body of salient poles of the second series and a neighboring base of one of the neighboring salient poles of the first series, characterized in that each excitation coil of the second series of salient poles comprises turns wound around the covered wound part of the coil body forming active parts in at least a part of each notch on each side of the coil body formed with the bare part of the base of a neighboring salient pole of the first series, such that the last turn is closer to each of the two bare parts of the two neighboring bases of salient poles of the first series than to the coil body.

[0015] Thanks to the invention, having a bare section on the base of a first set of poles allows the excitation coil of the adjacent pole in the second set to be larger. A bare section is therefore understood to be a portion of a ferromagnetic base or coil body not surrounded by a single wound excitation coil; that is, there is no coil wound around this bare section, but this bare section faces excitation coils of adjacent poles. Having a beak on each pole of the first series allows the excitation coil to be axially held on each side by a protrusion relative to the bare part of the base extending towards the corresponding wound salient pole of the second series of salient poles. Indeed, the beak protrusion axially covers turns of the excitation coil, thus increasing the air gap area of ​​the pole of the first series while simultaneously holding the excitation coil axially. The excitation coil is a block of turns around the salient pole of the second coil; holding the turns of the outermost layers allows the entire excitation coil to be held axially. In fact, there is an axial magnetic force that can attract the excitation coil towards the stator.Finally, the fact that each salient pole in the first series has a bare base (not surrounded by a coil) and a soft ferromagnetic block at the tip allows for a higher copper filling ratio by the excitation coil of the adjacent pole compared to inductors with only identical wound salient poles. Indeed, for example, having every other pole wound makes the inductor easier to manufacture (for example, only one coil out of two) and also allows these wound poles to have a higher conductor density in the slot since, unlike in inductors with only identical wound salient poles, there are no necessary gaps between the coils.Furthermore, the fact that it is an axial flux inductor allows for easy radial winding of the coils within the slot, maintaining a constant winding axis parallel to the central axis. This contrasts with a radial flux inductor, where the changing angle during winding around an axis perpendicular to the central axis results in areas (the middle zone within the slot) not held against centrifugal force by the nozzle. These unheld areas necessitate shims or spacers at the air gap, reducing the fill rate in the slot. Finally, such an inductor allows for salient poles without the need for a permanent magnet.

[0016] In addition to the characteristics mentioned in the preceding paragraph, the inductor 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: According to one embodiment, at least one excitation coil has its last turn in contact with the bare part of at least one base of one of the two adjacent salient poles. This maximizes the percentage rate of Conductor filling in a notch. According to an example, each excitation coil has its last turn in contact with the bare part. In one embodiment, at least one excitation coil has its last turn positioned at a distance from the bare portion of each base of two adjacent salient poles that is less than a diameter, width, or length of a cross-section of the excitation coil conductor. This maximizes the conductor fill percentage in a slot. In one example, each excitation coil has its last turn positioned at this distance from the bare portion. In another example, each coil either has its last turn positioned at this distance from the bare portion or its last turn in contact with the bare portion, as in the previous embodiment. In one embodiment, the inductor further comprises inter-pole magnets positioned between each salient pole of the first series and each salient pole of the second series at the radial face and surface of the axial air gap. This increases the magnetic saturation level of the poles, resulting in a higher inductance current before saturation and thus the potential for greater torque. According to a variant of the preceding embodiment, the inductor comprises a damping cage formed by electrical conductors, including inter-pole sections, each located between each pole at the notch axially covering the coils, and an outer cylindrical section surrounding the bare and wound poles, and an inner cylindrical section surrounded by the bare and wound poles. The inner cylindrical section is electrically connected to the outer cylindrical section by the inter-pole sections. The damping cage absorbs torque variations (stabilizing the instantaneous rotational speed) caused by a sudden change in load and acts in the event of an asymmetric load (one of the phases interrupted) or a short circuit. It also facilitates the synchronization and maintenance of several alternators (damping phase oscillations between alternators). In one embodiment, at least one or all of the coil bodies are made of paramagnetic or diamagnetic material, particularly a material lighter than the ferromagnetic material of the bases. This reduces the machine's weight; for example, each coil body comprises a plastic frame around which the first turn(s) of the coil are wound, and air is contained within the frame. Such a coil body is therefore lighter and less expensive than the following embodiment. According to one embodiment or a variant thereof, at least or all of the coil bodies are made of ferromagnetic material and each radial face of the axial air gap is formed by a radial surface of axial air gap. This allows the magnetic flux to be channeled (guided) and facilitated. According to one embodiment, each coil body comprises a bare part extending from the wound covered part, each ferromagnetic base of a salient pole of the first series comprises a second wound covered part of the ferromagnetic base extending from the first bare part, and in that each salient pole of the first series comprises an excitation coil wound around the second wound covered part having a last turn closer to each bare part adjacent to the coil body of the two salient poles adjacent to the first series than to the second wound covered part, this allows to be a central axial flux inductor of a double armature machine on both sides axially of the inductor. According to an example of the two preceding embodiments, the inductor is a central inductor in which: the coil bodies are each ferromagnetic and each comprise a first radial surface with axial air gap and The coil bodies and ferromagnetic bases each include a second radial axial air gap surface opposite the first radial axial air gap surface. This allows for a central inductor comprising ferromagnetic coil bodies that guide the axial flux. According to a variant of the previous embodiment, the inductor is a single-layer lateral inductor comprising a ferromagnetic frame having a radial face with respect to the central axis, in which: each salient pole of the first series extends axially from a radial face of the ferromagnetic frame comprising only the bare part extending from the frame to the nozzle and each coil body of the second series extends axially from the radial face of the ferromagnetic frame comprising only the wound covered part of the coil body extending axially from the frame, the excitation coil entirely surrounding only the wound covered part: Unlike the previous embodiment, this allows it to be a lateral axial flux inductor.

[0017] Another aspect of the invention relates to an axial flux synchronous electric machine: an inductor according to the first aspect of the invention with or without different features of one or more embodiments described above, a rotor shaft having an axis of rotation (X) corresponding to the central axis, a stator armature comprising: a winding comprising a number Pa of active parts (an active part comprises portions of conductors of a single coil (winding) protruding into a slot) regularly distributed angularly around the axis of rotation surrounding the rotor shaft; a winding comprising active parts in slots, a radial face with an axial air gap. This machine can be either an electric machine with a single inductor and a single armature, or an electric machine with two inductors and one armature, or even with two armatures and a single inductor. It can also be a stator-inductor machine with a ferromagnetic rotor, as described in one of the embodiments below. Furthermore, the armature winding can be concentric or distributed. In particular, it is also possible to have an armature with a concentric winding, with every other coil like the inductor, or an armature formed by teeth or coil bodies made of non-magnetic or paramagnetic material, for example, resin and fiberglass, or even a PCB-type electronic board including the active parts.

[0018] In addition to the characteristics mentioned in the preceding paragraph, the inductor 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:

[0019] In one embodiment, the inductor is integral with the rotor shaft and together they form a rotor, each radial surface of axial air gap being opposite the radial face of axial air gap of the armature, forming an axial air gap between them. The inductor is part of the rotor in this machine.

[0020] According to one example of this embodiment, the rotor further comprises a ring surrounding and in contact with the poles of the inductor. This helps to hold the coils, coil body, and ferromagnetic body of the inductor against centrifugal force.

[0021] In one particular example, the collar comprises an external portion forming a housing that receives part of the winding, the housing having an external diameter equal to the diameter of the inductor. Such a collar can be fitted onto the inductor, specifically onto the winding or onto a spur of the coil body. In another example of this feature, the collar comprises an internal portion fitted onto the rotor shaft, forming a second housing that accommodates another part of the coil body. The coil body can thus be a resin embedded within the housings.

[0022] According to an example of this embodiment, the inductor comprises an internal radius and an external radius measured radially respectively between an internal radial end of the nozzle closest to the central axis and an external radial end of the nozzle furthest from the central axis, and in that the internal radius is equal to 60% ± 20% of the external radius, and the rotor further comprises a device for supplying the excitation coils of the inductor comprising: a rotating part fixed to the rotor shaft and electrically connected to the excitation coils, being located axially between an axial end of an armature or inductor and an axial end of another armature or inductor axially opposed to this axial end, a stator part fixed in rotation to the stator armature.This allows for an axially compact electrical machine. Indeed, the machine with optimal axial flux will have an internal diameter of the active part (corresponding to the slot diameter) of the field winding or armature approximately equal to 60% of the external diameter of the active part of the field winding or armature, respectively (the armature and field winding normally having the same internal and external slot diameter, plus or minus manufacturing tolerances). Thus, by placing the rotating part of the machine's power supply within the available space inside the internal diameter of the field winding and / or armature, the machine is more axially compact. The axial ends of the armature or field winding can be an axial end of a field winding frame opposite its radial face of axial air gap, or an end of an armature yoke opposite its radial face of axial air gap.

[0023] According to a variant of this embodiment, the inductor is stator-shaped surrounding the rotor shaft, the machine further comprising a ferromagnetic rotor including the rotor shaft and a first set of ferromagnetic parts comprising a number Ns of parts regularly distributed around the axis of rotation, the number Ns being equal to the sum of or the difference between Pa / 2 and Pe / 2, where Pe is the number of active parts in the inductor, in which each excitation coil of a pole of the inductor comprises one active part per slot The conductor sections are formed in the slots of the coil windings, with the entire set of ferromagnetic components located between the first stator inductor and the first stator armature. This design eliminates the need for a stator inductor that is susceptible to centrifugal force and avoids the need for a power supply with a moving part.

[0024] In one embodiment, the machine comprises a second inductor identical to the first, with a ferromagnetic frame. The armature is a central armature located axially between the two inductors. This armature includes a second radial face with an axial air gap per tooth. The two inductors are angularly offset from each other by one pole such that each pole of the second series of one inductor is axially aligned with a pole of the first series of the other inductor. A machine with an even number of inductors and only one excitation coil out of every two allows for better filling of the slots, saving manufacturing and assembly time and avoiding even harmonics compared to an electrical machine with an odd number of inductors. This type of machine also allows for balancing the axial forces between the armature and the inductor.

[0025] In one example of this embodiment, the coils are embedded in resin, for example with fiberglass, or etched onto a printed circuit board (PCB). In another variation, the stator comprises ferromagnetic teeth held together by an internal or external yoke, or embedded in resin, with the coils wound between the teeth, for example around them in the case of concentric winding.

[0026] According to an example of this embodiment in which the inductor comprises magnets, each magnet of the first inductor has a polarity opposite to that of an axially aligned magnet of the second inductor. This improves the maximum performance of the machine.

[0027] According to another embodiment, the electrical machine comprises a second stator armature identical to the first armature; the field winding, according to the embodiment, has each ferromagnetic pole piece comprising a second radial surface with an axial air gap; the field winding being a central inductor located axially between the two armatures, and each armature comprising a yoke and teeth extending from the cylinder head to the central inductor, forming notches (numbered Pa) between them, each housing an active part. Such a machine allows for a balancing of axial forces between the armature and the inductor.

[0028] In one embodiment, the armature comprises a yoke, and teeth extend from the yoke to the central field winding, forming slots Pa in number, each slot housing an active portion of the armature coil / winding. The active portion of the armature coil / winding may comprise a plurality of conductor segments within the slot, each segment formed by a turn of the coil / winding.

[0029] In one embodiment, the rotor shaft further comprises a cooling channel including an axial duct extending axially within the rotor shaft and at least one spray duct extending from the axial duct to an opening opposite an armature or field winding. This allows the rotor shaft to be used as a system for spraying coolant onto the field windings and / or the armature winding to increase machine efficiency.

[0030] 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

[0031] The figures are presented for illustrative purposes only and are in no way limiting to the invention.

[0032] [Fig. 1 A] shows a schematic view of an inductor according to a first example of a first embodiment.

[0033] [Fig. 1 B] shows a cross-section of the inductor of figure 1 A.

[0034] [Fig. 1 C] shows a representation according to a schematic diagram at the level of a section AA of a salient pole of a first series of an example of the first embodiment.

[0035] [Fig. 1 D] shows a representation according to a schematic diagram at the level of a section BB of a salient pole of a second series of an example of the first embodiment.

[0036] [Fig. 2] shows a synchronous electrical machine according to a first example of a first embodiment including an inductor according to figure 1 A.

[0037] [Fig. 3] shows a synchronous electric machine according to another example of the first embodiment comprising two inductors according to figure 1 A.

[0038] [Fig. 4]. shows an inductor without excitation coils according to an example of a second embodiment.

[0039] [Fig. 5] shows the inductor of figure 4 comprising, according to a second embodiment

[0040] [Fig.6] shows a synchronous electrical machine according to a second embodiment comprising an inductor according to figure 5.

[0041] [Fig.7] shows a schematic diagram of an example of an electrical machine according to a third embodiment comprising two inductors according to the first embodiment.

[0042] [Fig.8] shows a schematic diagram of a ferromagnetic rotor of an electrical machine according to figure 7. DETAILED DESCRIPTION

[0043] The figures are presented for illustrative purposes only and are in no way limiting to the invention.

[0044] A first aspect of the invention relates to an inductor I, I', an example of a first embodiment of which is shown in its entirety in Figure 1A and in cross-section in Figures 1B to 1D, and another example of a second embodiment is shown partially and in its entirety respectively in Figures 4 and 1D. A second aspect of the invention relates to a single-layer axial flux synchronous electric machine M1, M1', M2, M3, each comprising at least one inductor I, I' according to the first aspect of the invention. Different embodiments of the single-layer axial flux synchronous electric machine M1, M1', M2, M3 are shown in Figures 2, 3, 6, and 7.

[0045] The inductor I, I' according to the first and second embodiments comprises a first series of salient poles 1 and a second series of salient poles 2 different from the first series of salient poles 1. In both embodiments, each salient pole 2 of the second series is located between two salient poles 1 of the first series. The salient poles 1, 2 of both series are regularly distributed angularly around a central axis X. The inductor I, I' comprises a number Y of pairs of salient poles, equal to the number of poles 1 in the first series plus the number of salient poles 2 in the second series. The inductor I of the first embodiment comprises a number Y of pole pairs equal to 5. and the number Y of pole pairs in the inductor I' of the second embodiment is 7. Preferably, as shown in both embodiments, each salient pole 1 of the first series is identical to manufacturing tolerances ready and each salient pole 2 of the second series is identical to manufacturing tolerances ready in order to avoid an imbalance.

[0046] In both embodiments, each salient pole 1 of the first series comprises a ferromagnetic base 11 including a bare portion 11n and a ferromagnetic beak 110 extending from the ferromagnetic base 11. The beak 110 includes a radial surface with an axial air gap 10. The beak 110 and the base 11 are formed from a soft ferromagnetic block, for example, a single piece of steel or stacked rolled steel sheets forming a block. Thus, each salient pole of the first series is devoid of permanent magnets.

[0047] In both embodiments, each salient pole 2 comprises a coil body 21 and an excitation coil 22 wound around at least a part of the coil body 21, called the wound covered part 210. Each salient pole 2. Each salient pole 2 comprises an axial air gap radial face 20.

[0048] In both embodiments, the inductor I, I' comprises slots 3. Each slot 3 houses an active portion of the various excitation coils 22 of a salient pole 2 of a second series. That is to say, each excitation coil 22 comprises two active portions, each housed in a slot adjacent to the coil body 21 of the second series of salient poles. Each active portion is formed by one or a plurality of conductor segments of the coil housed in the slot 3, each conductor segment corresponding to a turn of the excitation coil representing one turn around the coil body. Each slot 3 is formed between a coil body 21 of the salient poles 2 of the second series and a base 11 adjacent to one of the salient poles 1 adjacent to the first series. In other words, there is a number of notches equal to two Ys, i.e., one notch 3 on each side of each coil body 21 and one notch 3 on each side of each base 11.The nearest salient pole is defined as the closest salient pole. The higher the percentage of copper in slot 3 of an active portion of an excitation coil 22, the better the power of the machine at isovolume. A slot fill percentage is known to express the percentage of conductor volume (the active portion of the coil) within the volume of slot 3. In both embodiments, each coil. The excitation coil 22 comprises turns wound around the covered winding 210 of the coil body 21. Each turn is one turn of the coil's electrical conductor around the covered winding 210 of the coil body 21. Thus, the coil is wound along an axis substantially parallel to the central axis X of the inductor I, I'. Each turn comprises two active portions, each housed in a corresponding notch 3 on either side of the coil body 21. Each excitation coil 22 therefore comprises a first turn around and opposite (see in contact) the covered wound part 210, having one end connected to a terminal of the inductor or to another excitation coil 22 and a last turn connected to a terminal of the inductor or to another excitation coil 22. The excitation coils can be mounted electrically in parallel by connecting each end of the first turns together and each end of the last turns together.The excitation coils can also be electrically connected in series by linking each end of the first few turns to one end of the last turn of another excitation coil. The beak of the salient pole of the first series of salient poles 1 includes a protrusion that axially covers active portions of the excitation coil turns. The excitation coil can be embedded in a resin forming a block. The beak of each salient pole in the first series of salient poles thus allows two excitation coils to be held axially, by axially retaining active portions of each excitation coil housed in one of the two adjacent notches.In this example, each covered wound part 210 of the coil body 21 is completely covered by an active part of the excitation coil 22 and in this respect at least an active portion of a turn of the excitation winding 22 is closer to the nozzle 110 than to the covered wound part 210 of the coil body 21 and than to the bare part 11n. According to the first aspect of the invention, each last turn of each excitation coil 22 of a salient pole 2 of a second series of the inductor I, I' according to the first and second embodiment is closer to the bare part 11n of the base 11 of the second series of salient pole 1 than to the coil body 22 around which the last turn is wound. The last turn of each excitation coil 22 is closer to the bare part 1 1 n of the base 1 1 of the second series of salient pole 1 than to the first turn of the same excitation coil 22.This feature of the first aspect of the invention makes it possible to increase this percentage of notch filling in two different ways, whether according to the first or second embodiment described below.

[0049] In particular in the inductor I of the first embodiment, as seen in particular in Figure 1 B representing a radial section, i.e. in a plane perpendicular to the central axis, at the level of the excitation coils 22, only the salient poles 2 of the second series include an excitation coil 22 unlike the inductor I' of the second embodiment, as seen in Figure 5, of which each salient pole 1, 2 of the first and second series includes an excitation coil 12, 22 wound each around the base 11 or the coil body 21 but not at the same height as will be explained later.

[0050] According to one example, in the inductor I of the first embodiment, each excitation coil 22 is wound in the two slots 3 surrounding the corresponding coil body 21, with its last turn in contact with the bare part 11n of each base 11 of one of the two adjacent salient poles 1. This maximizes the conductor filling percentage in the slot 3. According to another example, each excitation coil has its last turn positioned at a distance from the bare part of each base of the two adjacent salient poles that is less than a diameter, width, or length of a section of the coil conductor. According to yet another example, at least one excitation coil 22 has its last turn distant from the bare part of each base of the two neighboring salient poles and at least one other excitation coil 22 has its last turn in contact with the bare part 1 1 n of a base 1 1 of one of the two neighboring salient poles 1.Of course, according to yet another example, the last turn of at least one excitation coil 22 can also be further from the bare part 1 1 n of a base 11 of one of the two salient poles 1 neighbor than the diameter or width or length of a section of the conductor of the excitation coil 22.

[0051] The inductor I according to the first embodiment further comprises a frame 4 having a central axis opening X. The base 11 and the coil body 21 each extend from a radial face of the base 11 in a direction parallel to the central axis X.

[0052] In this example, each coil body 21, in particular visible according to Figure 1D, schematically representing the axial section AA (section in a plane including the central axis X) in a salient pole 2 of the second series shown in Figure 1A, is made of ferromagnetic material and is in this case identical to Each base 1 of each salient pole 1 of the first series, in particular visible in Figure 1C, schematically represents the axial section BB in a salient pole 1 of the first series shown in Figure 1A. A schematic representation of the axial section AA or BB means that the dimensions are not to scale. In another example not shown, the coil body is made of plastic or composite material and includes a central opening to reduce weight. Thus, each salient pole of the inductor is devoid of a permanent magnet. Interpolar magnets can be inserted between two salient poles, covering the active part of the excitation coil, as explained later. The absence of a permanent magnet in a salient pole reduces cost but also increases torque for a given volume / diameter and eliminates demagnetization problems in case of high temperatures.In the case of an inductor comprising interpolar magnets and high heat having demagnetized one or more magnets, the inductor will always operate with lower efficiency.

[0053] In this example, optionally, each salient pole 2 of the second series also includes a ferromagnetic beak 212 extending from the coil body 21 to the radial face of the axial air gap of the salient pole 2. In other words, the radial face 20 includes a radial surface 20 of the beak 212. In this example, each beak 212 is identical to the beak 110 of a salient pole 1 of the first series.

[0054] In this example, as can be seen in Figure 1D, each excitation coil 22 completely covers the corresponding coil body 21 and therefore each covered wound part 210 completely forms the coil body 21 of the salient pole 2 of the second series.

[0055] Each bare part 1 1 n of a salient pole 1 of the first series of the inductor I of the first embodiment also entirely forms the ferromagnetic base 11 of the salient pole 1 of the first series.

[0056] In particular, in this example of this first embodiment, the inductor I comprises inter-pole magnets 7 each positioned between a beak 1 10 of a salient pole 1 of the first series and a beak 212 near a salient pole 2 of the second series at the level of the axial air gap radial face and surface.

[0057] Each magnet 7 comprises a first side having a first polarity, attached to a beak 1 10 of a salient pole 1 of the first series and its other side having a second polarity, attached to a beak 212 of the salient pole 2 of the second series. For example, the first polarity of each magnet is north and the second polarity is south, but this can be reversed, it all depends on the direction of the current and the direction of the winding of the excitation coils 22.

[0058] The inductor I also includes an internal radius r1 measured radially between an internal radial end of the nozzle 110 closest to the central axis X and an external radial end of the nozzle 110 furthest from the central axis X. Preferably the internal radius r1 is equal to 60% ± 20% of the external radius r2; here in this example, this ratio r1 / r2 is equal to 60%, allowing the best optimization of the torque for the same external diameter.

[0059] In this example, the inductor I is intended to be part of a rotor of a synchronous electric machine M1, M1' shown in Figures 2 and 3 and therefore to be mounted on a rotor shaft, a ring 6 surrounds the poles 1, 2, while being in contact with an external circumference of these poles 1, 2. In this example, the ring 6 is ring-fitted (press-mounted) against a circumferential surface of each beak 110, 212 thus surrounding the inter-pole magnets 7 to retain them radially against the centrifugal force as well as to prevent deformation of the poles 1, 2 in particular at the connection between the frame 4 and the bases 11 or the coil bodies 21.In this example, we can see that the excitation coils 22 comprise an inner (near the central axis) and an outer (farthest from the central axis) winding. The smallest radius of the inductor I is measured from the end of the inner winding closest to the central shaft, and the largest radius of the inductor I is measured from the end of the outer winding furthest from the central shaft (or the outer diameter is measured between the two outer ends of the outer windings of two excitation coils 22). Of course, according to another example, the frame 4 could have the largest outer diameter of the inductor, but the inductor would be heavier. In this example, the ferrule 6 has an outer diameter between the outer diameter of the frame 4 and the outer diameter (2 * r²) of the salient poles 1 and 2. According to another example, fret 6 may include a part forming an external housing surrounding the external coil ends on the outer side.

[0060] According to another example not shown, the inductor is a squirrel cage damper; in this example, each inter-pole magnet and the fret are replaced by electrical conductors in the shape of a bar and a ring respectively.

[0061] The axial flux synchronous machine M1 shown in Figure 3 is, according to an example of a first embodiment, without the representation of the rotor shaft, the fret 6 and the interpolar magnets 7.

[0062] The rotor of the axial flux synchronous machine M1 includes, in addition to the inductor I, a rotor shaft with a central axis X fixed to the frame 4 directly or indirectly, for example by a bushing press-fitted onto the rotor shaft and against a circumferential peripheral surface 40 of the frame 4 visible in Figure 2. According to another example, the rotor shaft includes a collar or shoulder allowing an external circumferential surface to be press-fitted directly against the circumferential peripheral surface 40 of the frame 4. According to another example not shown, the frame 4 and the rotor shaft are made as a single unit (cast or machined). According to yet another example, the rotor flange 6 can surround the inductor I, cover the radial surface of the frame 4 opposite the salient poles 1, 2, and form the connecting piece between the rotor shaft (by being press-fitted or by other means of attachment (flange, etc.)) and the inductor I.

[0063] The axial flux synchronous machine M1 further comprises a lateral stator armature 5 including a winding with a number Pa of active sections (the number of conductor segments of a coil, each conductor segment being formed by a turn of the coil), each in this case housed in a slot formed between two teeth of the armature 5. The teeth are regularly spaced angularly around the central axis C, i.e., the axis of rotation X, surrounding the rotor shaft (not shown). In this example, the number Pa of active sections is equal to 12, and the winding is a concentric fractional winding, corresponding to a number where the number of armature teeth divided by the number of phases and by the number of poles of the field winding is not a whole number (or half-whole number). In this case, this number is equal to 12 / 10 / 3 = 0.4."The armature can also include coil bodies, each wound by a coil of the winding, forming active parts distributed regularly angularly around the central axis C.

[0064] The armature 5 (explained in more detail in the third machine embodiment shown in Figure 7) includes slots between each tooth and a winding with the active parts in the slots. In this example, the winding is concentric but could be distributed, for example, a wave-distributed configuration. The armature 5 can have, for example, three phases, but could have more. In this example, the armature 5 has a rear yoke 54 made of a lamination pack, but could also be made of compact magnetic iron powder. The teeth in this example are also made of soft ferromagnetic material and preferably formed from a lamination pack. In other words, the stator armature 5 is an armature comprising a winding 50 wound within a lamination pack forming the teeth. Thus, each tooth of the armature is devoid of a permanent magnet.

[0065] The coils are wound into notches in the lamination pack of the armature 5.

[0066] The armature 5 has a radial face with an axial air gap, in this example facing the air gap surfaces 10 of the nozzles 110 of the salient poles 1 of the first series and the radial face 20 (in this case, a radial surface of the nozzle 212) of the salient poles 2 of the second series. In this embodiment, the axial flux air gap is thus formed between the armature I and the field winding 5.

[0067] The second example of this embodiment of the axial flux rotating electrical machine M1' visible in figure 3 is different from the axial flux rotating electrical machine M1 in that it includes two inductors I according to the first example of this embodiment and a central armature 5'.

[0068] In this second example, the rotor includes the two inductors I and are coupled in rotation to a rotor shaft (not shown) according to one of the examples described previously.

[0069] The central stator armature 5' differs from the lateral stator armature 5 in that it does not have a yoke 54 but only a plurality of teeth forming slots and a winding 50 comprising active parts in slots. The windings can be held together by various manufacturing methods, for example by being embedded in resin, or the stator can comprise an external cylindrical yoke surrounding the armature 5' or an internal yoke surrounded by the winding 50.

[0070] In particular, in this example, each tooth of the central stator armature 5' is ferromagnetic and comprises a first ferromagnetic radial surface forming together the first axial air gap radial face opposite the first armature I and a second ferromagnetic radial surface on the opposite side axially from the first radial surface, together forming a second radial face with axial air gap opposite the second armature I.

[0071] In this second example, the two inductors I are fixed to the rotor by being angularly offset from each other by one pole such that each pole of a first series of one of the inductors I is axially aligned with a pole of a second series of the other inductor I.In other words, when the first radial surface of the armature 5, comprising a radial surface of each active part of the winding and, in this case, also that of each tooth or coil body of the armature 5, is opposite (depending on the angle of rotation of the armature) an air gap surface 10 of a nozzle 110 of one of the salient poles 1 of the first series of the first armature I, the second radial surface of the armature 5 (also comprising a second radial surface of each active part of the winding and, in this case, also that of a tooth or coil body of the armature 5) is opposite a radial face 20 (in this case, a radial surface of the nozzle 212) of one of the salient poles 2 of the second series of the second armature I (and conversely when the rotor rotates angularly by one pole so here 36° (180° / Y = 180 / 5 = 36°).This second example of this first embodiment of the axial flux electric machine M1 has a double advantage compared to that of the first example of the axial flux electric machine M1, the first is to avoid even harmonics, the second is to balance the axial forces on the rotor allowing to increase the life of the bearings (for example bearings) supporting the rotor shaft.

[0072] In these two examples of this embodiment, the rotor further includes a power supply device (not shown) for the field windings 20 of the field winding I. This device comprises a rotating portion fixed to the rotor shaft and electrically connected to the field windings 20, and a stator portion fixed for rotation to the stator armature. The ratio r1 / r2, equal to 60% ± 20% (here equal to 60%), allows for a radius r1 of the field winding I sufficiently large so that the rotating portion fixed to the power supply device is located axially between an axial end of the yoke of one armature in the case of the first example, or of the frame 4 of the second field winding I in the case of the second example, and an axial end of the frame 4 of the first field winding I.

[0073] In the various examples shown, the coil bodies are made of ferromagnetic material but could be made of paramagnetic or diamagnetic material.

[0074] The inductor I' according to the second embodiment is now described, in this case in this example it is a central inductor I' to be located between two lateral armatures 5, as shown in Figure 6 representing an axial flux electric machine M2 according to a second embodiment comprising the inductor I' surrounded axially on both sides by two lateral armatures 5 (whose winding is not shown).

[0075] Figure 4 represents the inductor I' without excitation coil 20. As can be seen, this inductor ï is different in that it is devoid of a frame 4 and in that each pole 1, 2 comprises: a second radial air gap face 20' formed in this example by a radial air gap surface of a second nozzle 212' extending from a coil body 21 opposite the first nozzle 212 and a second radial axial air gap surface 10' formed in this example by a second nozzle 110' extending from a base 11 opposite the first nozzle 110 forming the first radial axial air gap surface 10 opposite the first radial axial air gap surface.

[0076] In this example, the two air gap faces of inductor I' are identical to those of inductor I, except, as already mentioned, that it comprises 7 pairs of poles. In this particular example, inductor I' also includes, on its other face, inter-pole magnets T between each salient pole 1, 2, and a second ring 6' surrounding the second terminals 1, 10', 2, 12'.

[0077] In this figure, a cross-section is also shown at the level of a collar 8 of a rotor shaft.

[0078] Figure 5 shows a schematic diagram in perspective view of the second face of the inductor I' of Figure 4 (with a different angle of rotation about the central axis X) with the excitation winding, which differs from that of the first embodiment in that it comprises an excitation coil 12 per salient pole 1 of the first series. Each base 11 therefore includes, in addition to a bare part 11n, a second covered wound part 11' (referenced in Figure 4).

[0079] In this second embodiment, each excitation coil 12 is therefore wound around the second covered wound part 11' of the ferromagnetic base 11 extending from the first bare part 11n.

[0080] In addition, each coil body 21 comprises a bare part 21n extending from the covered wound part 210. Each excitation coil 12 wound around a second covered wound part 11' of the ferromagnetic base 11 of each pole 1 of the first series has a last turn closer to the two bare parts 21n adjacent to the two coil bodies 21 adjacent to each salient pole 2 adjacent than to the second covered wound part 210 of that coil body 21 around which it is wound.

[0081] Thus, each notch 3 has two axial volume halves divided in two by a radial median plane perpendicular to the axis of rotation. The first half houses the active parts of the excitation coil 12 of a salient pole 1 of a first series, and the second half houses the active parts of the excitation coil 22 of a salient pole 2 of a second series. The filling rate can therefore be greater than in the prior art, where each coil of each pole of the first series completely surrounds the entire axial length of the corresponding base (no bare parts), and each other coil of each pole of the second series completely surrounds the entire axial length of the corresponding coil body. Indeed, in the prior art, the active parts of each coil of each pole are housed in each notch opposite the active parts of the neighboring coil, producing an unfilled gap in the notch.Indeed, in the prior art, each coil includes its active parts in a circumferential half of the volume defined by a plane passing through the axis, whereas in this embodiment they are located in an axial half of the notch defined by a plane perpendicular to the axis, making it possible to dispense with the gap (indeed, the excitation coils 12, 22 can be in contact with each other in the notch 3).

[0082] The active part filling rate per notch is therefore close to 100% (unattainable due to the insulation between each conductor and the space formed between each turn).

[0083] According to another embodiment of an inductor not shown, identical to this second embodiment, except that the inductor is a lateral inductor comprising, in place of the second radial face, a frame replacing the fret, the interpolar magnets, and the salient pole tips of the two series. Thus, this lateral inductor is like the lateral inductor I of the first embodiment except that the winding is like that of the second embodiment.

[0084] Figure 6 shows the axial flux synchronous electric machine M2 according to a second embodiment comprising the field winding I' shown in Figure 5. This axial flux synchronous electric machine M2 includes a second stator armature 5 identical to the first stator armature 5 of the electric machine M1 of the first example of the first embodiment, except that the stator armature comprises 7 pole pairs. In Figure 6, the winding of each stator armature 5 is not shown. The central field winding I' is located axially between the two armatures 5, each comprising a cylindrical yoke 54 and poles formed by a ferromagnetic base 51 extending axially from a radial face of the yoke 54 and a ferromagnetic nozzle 510 extending from the base towards the central field winding I'.

[0085] Figure 7 shows a schematic diagram of an axial cross-section (including the axis of rotation) of an axial flux synchronous electric machine M3 according to a third embodiment. As this figure is a schematic diagram, length ratios, for example r1 / r2, are not shown.

[0086] The axial flux synchronous electric machine M3 comprises two lateral field windings I according to the first embodiment and a central armature 5' as in the axial flux synchronous electric machine M1' according to the second example of the first embodiment. The two lateral field windings I are shown schematically but are like those of the axial flux synchronous electric machine M1' except that the two lateral field windings I are stator-type, that is, fixed in rotation to the armature 5 and not to the rotor shaft.

[0087] The axial flux electric machine M3 comprises a ferromagnetic rotor 9 including a rotor shaft 91 and a first and second set 90, 90' of preferably identical ferromagnetic parts 93 rotatably fixed to the rotor shaft 91. The first set 90 of ferromagnetic parts 93 is shown in Figure 8. The first and second sets 90, 90' of ferromagnetic parts 93 each comprise a ring 92 fixed to the rotation shaft 91 of the rotor 9 and a number Ns of ferromagnetic parts 93 regularly distributed around the axis central X each fixed on the crown 92. The crown 92 can be made of plastic or composite for example. The number Ns is equal to the sum of or the difference between Pa / 2 and Pe / 2, where Pa is the active part number of the armature and Pe is the active part number of the field winding. The first set 90 of ferromagnetic parts 93 is located between the first stator field winding I and the central stator armature 5, while the second set 90 of ferromagnetic parts 93 is located between the second stator field winding I and the central stator armature 5. The first set 90 of ferromagnetic parts 93 has a first radial face of axial air gap facing the radial face of the first armature I. The second set 90' of ferromagnetic parts 93 has a second radial face of axial air gap facing the radial face of the second armature I.As a reminder, the radial air gap face of each armature I includes the radial axial air gap face 20 of the salient poles 2 of the second series, i.e. in this example a radial surface of the nozzle 212 as well as the radial axial air gap surface of the nozzle 110 of the salient poles 1 of the first series.

[0088] The two inductors I are fixed together, being angularly offset from each other by a pole such that each pole of a first series of one of the inductors I is axially aligned with a pole of a second series of the other inductor I. In this figure 7, we can see a salient pole 2 of the second series of the first armature I axially aligned with salient pole 1 of the first series of the second armature, as well as a salient pole 1 of the first series of the first armature I axially aligned with a salient pole 2 of the second series of the second armature I.

[0089] In this example, the coil bodies 51 of the armature 5 are symmetrical and comprise a base 510 and a first 512 and a second 512' beak axially opposed to each other extending from the base 510. The base 510 with the first beak 512 and the second beak 512' form between them a notch housing the winding 50, for example a concentric coil per pole. In other words, in this axial flux electric machine M3, the first nozzle 512 of the central armature 5 has a first radial axial air gap surface opposite a second radial axial air gap face of the first set 90 of ferromagnetic parts 93 and the second nozzle 512' of the central armature 5 has a second radial axial air gap surface opposite a first radial axial air gap face of the second set 90' of ferromagnetic parts 93.

[0090] The coils in the different embodiments each include an electrical conductor, for example made of copper, and an insulator allowing the conductor to be isolated from one turn to another turn or from one coil to another coil or from the coil to a ferromagnetic part (base, beak or coil body or frame, yoke etc).

[0091] In the various embodiments of the different machines, the rotor shaft may include a cooling channel comprising an axial conduit extending axially in the rotor shaft, an opening in the axial conduit to receive a cooling fluid such as oil and at least one spray conduit extending from the axial conduit to an opening on the circumference of the rotor shaft opposite an armature or field coil.

[0092] Unless otherwise specified, the same element appearing on different figures has a unique reference.

Claims

CLAIMS

1. Inductor (I, I') of an axial flux synchronous electrical machine (M1, M1 M2, M3) the inductor (I, I') being wound with a salient pole comprising: o a first series of salient poles (1) each comprising: o a ferromagnetic base (11) regularly distributed angularly around a central axis (X), and a nose (110) extending from the ferromagnetic base (11) comprising a radial axial air gap surface (10), each ferromagnetic base (11) comprising at least one bare portion (11n), o a second series of salient poles (2), each located between two salient poles (1) of the first series, each salient pole (2) of the second series comprising at least:

1. a coil body (21) comprising a wound covered portion (21 1), 2. an excitation coil (22) wound around the covered wound portion (210) of the coil body (21), 3. an axial air gap radial face (20), o notches (3), each formed between a coil body (21) of the salient poles (2) of the second series and a base (1 1 1 ) adjacent to one of the salient poles (1 ) adjacent to the first series o characterized in that each excitation coil (22) of the second series of salient poles (2) comprises turns wrapped around the wound covered portion (210) of the coil body (21) forming active portions in at least a portion of each notch (3) on each side of the coil body (21) formed with the bare portion (11 n) of the base (1 1 ) of a salient pole (1 ) adjacent to the first series, such that the last turn is closer to each of the two bare portions (11 n) of the two bases (1 1 ) adjacent to the salient pole (1 ) of the first series, than of the coil body (21).

2. Inductor (I, I') of an axial flux synchronous electrical machine (M1, M1 M2, M3) according to claim 1, wherein in each salient pole (1) of the first series, the base (11) and the nose (110) are a block of soft ferromagnetic material, the nose (110) comprising on each side a protrusion relative to the bare part (11n) of the base (11) extending towards the corresponding neighboring salient pole of the second series of salient poles (2), the protrusion axially covering turns of the excitation coil.

3. Inductor (I') of a synchronous electrical machine (M2) according to one of the preceding claims in which: - each coil body (21) comprising a bare part (21n) extending from the covered wound part, - each ferromagnetic base (1 1 ) of a salient pole (1 ) of the first series comprises a second covered wound part (1 1 ') extending from the first bare part (1 1 n), and - in that each salient pole (1 ) of the first series comprises an excitation coil (12) wound around the second covered wound part (11 ') having a last turn closer to each bare part (21 n) neighboring the coil body (21 ) of the two salient poles (1 ) neighboring the first series than to the second covered wound part (1 1 ').

4. Inductor (I') of a synchronous electrical machine according to claim 3, in which the inductor (I') is a central inductor in which: - the coil bodies (21) are each ferromagnetic and each comprise a first radial axial air gap surface (10) and - the ferromagnetic bases (11) and the coil bodies (21) each comprise a second radial axial air gap surface (20', 10') opposite the first radial axial air gap surface (10, 20).

5. Inductor (I) of a synchronous electrical machine (M1, M1') according to one of claims 1 to 4, in which the inductor is a single-layer lateral inductor comprising a ferromagnetic frame (4) comprising a radial face relative to the central axis (X), - each salient pole (1) of the first series extending axially from the radial face of the ferromagnetic frame (4) comprising only the bare part (11 n) extending from the frame (4) to the beak (1 10) and - each coil body of the second series extending axially from the radial face of the ferromagnetic frame comprising only the covered wound part (210) of the coil body (21) extending axially from the frame, the excitation coil entirely surrounding only the covered wound part (210). [Claim s] Axial flux synchronous electric machine (M1, M1', M2, M3) comprising an inductor (I, I') according to one of the preceding claims, comprising: - a rotor shaft having an axis of rotation (X) corresponding to the central axis (X), - a stator armature (5, 5') comprising: o a winding (50) comprising a number Pa of active parts regularly angularly distributed around the axis of rotation (X) surrounding the rotor shaft, o a radial face of axial air gap.

7. Axial flux synchronous electrical machine according to claim 6 in which the inductor (M1, M1', M2) is integral with the rotor shaft and together forms a rotor, each axial air gap radial surface facing the axial air gap radial face of the armature (I, I') forming an axial air gap between them. [Claim s] Axial flux synchronous electric machine (M1, M1', M2) according to claim 7 wherein the rotor further comprises a hoop (6) surrounding and in contact with the poles of the inductor (I, I').

9. A compact axial flux electric machine according to claim 8, wherein the hoop comprises a housing receiving a portion of the winding, the housing having a diameter external to the diameter of the inductor.

10. Compact axial flux electric machine according to one of the preceding claims 7 to 9, in which: the inductor comprises an internal radius (r1) and an external radius (r2) measured radially respectively between an internal radial end of the nozzle (110) closest to the central axis (X) and an external radial end of the nozzle (110) furthest from the central axis (X) and in that the internal radius (r1) is equal to 60% + or - 20% of the external radius (r2) and - the rotor further comprises a device for supplying the excitation coils (20) of the inductor comprising: o a rotary part secured to the rotor shaft and electrically connected to the excitation coils (20), being located axially between an axial end of an armature (5) or inductor (i) and an axial end of another armature or another inductor axially opposite this axial end, o a stator part secured in rotation to the stator armature. [Claim 1 1 ] Axial flux synchronous electric machine (M3) according to claim 6 wherein the inductor (I) is stator surrounding the rotor shaft (9), the machine further comprising a ferromagnetic rotor (90) comprising the rotor shaft (9) and a first set (90) of ferromagnetic parts (93) comprising a number Ns of parts regularly distributed around the axis of rotation (X), the number Ns is equal to the sum of or the difference between Pa / 2 and Pe / 2, Pe being the number of active parts of the inductor, the set (90) of ferromagnetic parts (93) being located between the first stator inductor (I) and the first stator armature (5).

12. Axial flux synchronous electric machine (M1 ', M3) according to one of the preceding claims 6 to 11 comprising a second inductor (I) according to claim 5 identical to the first inductor, the armature (5) being a central armature (5) located axially between the two inductors (I), the armature (5) comprising a second radial axial air gap face per tooth, and the two inductors are angularly offset from each other by one pole such that each pole of the second series of one of the inductors is axially aligned with a pole of the first series of the other inductor.

13. An axial flux electrical machine according to the preceding claim, wherein the inductor is according to claim 2 and in that each magnet of the first inductor has a polarity opposite to the polarity of an axially aligned magnet of the second inductor.

14. An axial flux machine (M2) according to one of the preceding claims 6 to 12 comprising a second stator armature (5) identical to the first stator armature (5), the inductor (I') being according to claim 3 or 4 and being a central inductor located axially between the two armatures (5), each armature (5) comprising a yoke and teeth extending from the yoke towards the central inductor forming between them notches of number Pa each housing an active part.

15. A compact axial flux electrical machine according to one of the preceding claims 6 to 14, wherein the rotor shaft further comprises a cooling channel comprising an axial duct extending axially in the rotor shaft and at least one projection duct extending from the axial duct to an opening opposite a coil of the armature or the inductor.

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