Electric machine comprising a magnetic gear torque transmission mechanism

Abstract

The present description relates to an electrical machine (21) comprising: a stator (19c) having an internal surface (190c) delimiting a cavity centered on an axis of rotation (X'') of the electrical machine; a plurality of first electromagnets (57) configured to generate a first magnetic field, the plurality of first electromagnets (57) being fixed to the stator (19c); a magnetic generation device (50) configured to generate a second magnetic field, the magnetic generation device (50) being fixed to the stator (19c); a magnetic excitation device (51); and a first shaft (19a) extending within the cavity along the axis of rotation (X''); and a second shaft (19b) extending within the cavity, along the axis of rotation (X''), being concentric with the first shaft (19a);in which one of the first and second shafts (19a, 19b) is configured to generate a third magnetic field, following excitation by the magnetic excitation device (51), the third magnetic field being synchronized with: the first magnetic field so as to implement an electromechanical conversion between a mechanical power from one of the first shafts (19a) and the second shaft (19b), and an electrical power from the plurality of first electromagnets (57); and the second magnetic field so as to transmit a torque between the first shaft (19a) and the second shaft (19b). Figure for the abstract: Figure 11b;

Description

Title of the invention: Electric machine comprising a magnetic gear torque transmission mechanism technical field

[0001] The present exposition relates to electrical machines, in particular electrical machines with a torque transmission mechanism. STATE OF THE ART

[0002] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types of aircraft and those currently in operation, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0003] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and whose integration and use in civil aviation have moderate environmental impacts, with the aim of improving the energy efficiency of aircraft.

[0004] Consequently, the Applicant is constantly working to reduce its climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work focuses on new generations of aircraft engines, the lightening of aircraft, in particular through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and, as essential complements to technological progress, aviation biofuels.

[0006] In this regard, certain electrical machines, on which the Applicant is working, include a torque transmission mechanism operating by interaction between permanent magnets. For example, the torque transmission mechanism includes a magnetic gear, which includes permanent magnets. positioned at the external surface of its input shaft which interact with other permanent magnets positioned at the internal surface of its crown.

[0007] Such magnetic gears are notably an alternative to reduction mechanisms using toothed meshing. Indeed, the absence of teeth avoids the risk of mechanical breakage due to friction or cavitation phenomena.

[0008] But, at high speed, this type of magnetic gear presents problems: demagnetization of the permanent magnets, variation of the air gap due to the play generated by the shrink fitting of the permanent magnets, or even risks of runaway, which can sometimes cause significant damage.

[0009] One solution to overcome these drawbacks would be to replace the permanent magnets in the ring gear with an electromagnet and to eliminate permanent magnets from the input shaft, while designing it to be asymmetrical in rotation. However, in this case, since the transmitted torque is purely reluctant, the transmissible torque density is low and unsuitable for high-speed applications. GENERAL STATEMENT

[0010] The aim of this presentation is to propose an electric machine that is robust at high speed while transmitting a high torque density.

[0011] To this end, the present presentation is the result of technological research aimed at significantly improving aircraft performance and, in this sense, contributes to reducing the environmental impact of aircraft.

[0012] To this end, according to a first aspect of this presentation, an electrical machine comprising: is proposed a stator having an internal surface delimiting a cavity centered on an axis of rotation of the electrical machine; a plurality of first electromagnets configured to generate a first magnetic field, the plurality of first electromagnets being attached to the stator; a magnetic generation device configured to generate a second magnetic field, the magnetic generation device being attached to the stator; a magnetic excitation device; and a first tree extending within the cavity along the axis of rotation; and a second tree extending within the cavity, along the axis of rotation, being concentric with the first tree; in which one of the first and second shafts is configured to generate a third magnetic field, following excitation by the magnetic excitation device, the third magnetic field being synchronized with the first magnetic field so as to implement an electromechanical conversion between a mechanical power of one of the first shafts and the second tree, and an electrical power from the plurality of first electromagnets; and the second magnetic field so as to transmit a torque between the first tree and the second tree.

[0013] It may be provided that the magnetic excitation device is integral with the stator.

[0014] It may be provided that the magnetic excitation device comprises a second electromagnet.

[0015] It may be provided that the one of the first shaft and the second shaft which is configured to generate a third magnetic field, is further configured to present at least two pairs of magnetic poles following excitation by the magnetic excitation device.

[0016] It may be provided that a plurality of shoulders extend in projection from that of the first shaft and the second shaft which is configured to generate a third magnetic field, the plurality of shoulders forming pairs of magnetic poles following excitation by the magnetic excitation device.

[0017] It may be provided that the magnetic generation device includes a permanent magnet.

[0018] The magnetic generation device may be provided to include a third electromagnet.

[0019] It may also be provided, where the magnetic excitation device includes a second electromagnet, that at least one of the second and third electromagnets is configured to control the torque transmitted between the first shaft and the second shaft as a function of a supply current to that of the second and third electromagnets.

[0020] It may be provided that the plurality of first electromagnets is configured to control the electromechanical conversion as a function of supply currents of the plurality of first electromagnets.

[0021] It may be provided that the stator has an external surface extending around the internal surface; the stator further comprising a first plurality of teeth extending radially between the inner surface and the outer surface and being aligned in a first plane, and a second plurality of teeth extending radially between the inner surface and the outer surface and being aligned in a second plane offset axially with respect to the first plane; in which: The plurality of first electromagnets comprises a first row of first electromagnets, each first electromagnet of the first row of first electromagnets being fixed to a respective tooth of the first plurality of teeth, and a second row of first electromagnets, each first electromagnet of the second row of first electromagnets being fixed to a respective tooth of the second plurality of teeth; The magnetic generation device comprises a first plurality of permanent magnets fixed to the internal surface and aligned in the first plane, and a second plurality of permanent magnets fixed to the internal surface of the stator and aligned in the second plane; and The magnetic excitation device includes a second electromagnet fixed to the internal surface of the stator and positioned axially between the first plane and the second plane.

[0022] According to a second aspect, an aeronautical propulsion system is proposed comprising: a first mobile drive shaft rotating around an axis of rotation of the propulsion system; a blower shaft; an aircraft electrical network; and a first electrical machine according to the first aspect, in which: the first drive shaft is connected to one of the first shafts and the second shafts of the first electric machine; The blower shaft is connected to the other shaft of the first shaft and the second shaft of the first electrical machine; and the electrical network is electrically connected to the plurality of first electromagnets of the first electrical machine.

[0023] It may be provided that the first electric machine is a motor configured to drive one of the first shaft and the second shaft in rotation around the axis of rotation from an electrical power supplied by the electrical network.

[0024] It may be provided that the first electrical machine is a generator configured to inject electrical power into the electrical network from mechanical power supplied by one of the first shaft and the second shaft.

[0025] It may be provided that the aeronautical propulsion system further comprises: a second drive shaft, the second drive shaft being configured to rotate at a speed about the axis of rotation of the propulsion system different from the speed of rotation, about the axis of rotation of the propulsion system, of the first drive shaft; and a second electric machine according to the first aspect, in which: the second drive shaft is connected to one of the first and second shafts of the second electric machine, the other of the first and second shafts being free; and the electrical network and the plurality of first electromagnets of electromagnets of the first electric machine are electrically connected to the plurality of first electromagnets of the second electric machine.

[0026] According to a third aspect, an aircraft is proposed comprising a cell and an aeronautical propulsion system according to the second aspect, in which the aeronautical propulsion system is fixed to the cell. DESCRIPTION OF THE FIGURES

[0027] Other features, purposes and advantages will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0028] Fig. 1 illustrates an example of an aircraft that may include a propulsion system.

[0029] Figure 2 is a schematic, partial, cross-sectional view of an example system dual-flow, twin-body propulsion system in which the fan section is enclosed.

[0030] Fig. 3 is a schematic, partial, cross-sectional view of an example of a dual-flow, dual-body propulsion system in which the fan section is unfaired.

[0031] Fig. 4a and Fig. 4b are schematic isometric views of magnetic gear torque transmission mechanisms.

[0032] Fig. 5a and Fig. 5b are schematic isometric views of a stator of magnetic gear torque transmission mechanisms.

[0033] Fig. 6a and Fig. 7a are schematic isometric cross-sectional views transverse magnetic gear torque transmission mechanisms.

[0034] Figures [Fig. 6b] and [Fig. 7b] are schematic front views in longitudinal section of magnetic gear torque transmission mechanisms.

[0035] Fig. 8 is an isometric schematic view of a first shaft of a magnetic gear torque transmission mechanism.

[0036] Fig. 9 is an isometric schematic view of a second shaft of a magnetic gear torque transmission mechanism.

[0037] The [Fig. 10] is an electrical diagram of a propulsion system.

[0038] Fig. 11a and Fig. 11b are schematic isometric views of machines electric.

[0039] Fig. 12a and Fig. 12b are schematic front views of electrical machines. DETAILED DESCRIPTION

[0040] An example of an application to the aeronautical field of the electric machine and the magnetic gear torque transmission mechanism according to this exposition is described below. Of course, the electric machine and the torque transmission mechanism according to this exposition may be suitable for other electromechanical conversion chains, particularly in the automotive, rail, or even wind power sectors, and is therefore not limited to aircraft.

[0041] Aircraft

[0042] An aircraft 100 is a device configured to rise and move through the air, and may, for example, be a civil or military airplane, or even a helicopter. An aircraft 100 comprises an airframe (or "airframe" in Anglo-Saxon terminology) which, in the case of an airplane, consists of a fuselage, a wing comprising two wings, tail assemblies, flight controls, and a landing gear.

[0043] Propulsion system

[0044] A propulsion system 1 has a principal direction along a longitudinal axis X along which the propulsion system 1 extends. The propulsion system 1 is an aeronautical propulsion system 1 configured to be attached to the airframe of the aircraft 100 by means of a pylon (or mast), which is fixed to the airframe of the aircraft 100.

[0045] Unless otherwise specified, the terms "upstream" and "downstream" are used with reference to the overall direction of airflow through the propulsion system 1 in operation.

[0046] The propulsion system 1 comprises, from upstream to downstream, a blower section 2 and a primary body 3, often called a "gas generator". The primary body 3 is centered on the longitudinal axis X, and comprises a compressor section 4, 5, a combustion chamber 6, and a turbine section 7, 8.

[0047] The fan section 2 comprises at least one rotor 9 adapted to be driven in rotation, about the longitudinal axis X, relative to a stator portion of the propulsion system 1, by the primary body 3. In this way, an airflow F is drawn into the propulsion system 1. Each rotor 9 of the fan section 2 comprises a hub 13 and blades 14 extending radially from the hub 13. The blades 14 of each rotor 9 may be fixed relative to the hub 13 or have a variable pitch. In this case, the root of the blades 14 of each rotor 9 is pivotally mounted about a pitch axis and is connected to a pitch-changing mechanism 15 mounted in the propulsion system 1, the pitch being adjusted according to the flight phases by the pitch-changing mechanism 15.

[0048] The blower section 2 may further include a stator 16, or rectifier, which includes blades 17 mounted on a hub of the stator 16 and whose function is to rectify an airflow F2 which flows out of the rotor 9. The blades 17 of the stator 16 may be fixed relative to the hub of the stator 16 or have a variable pitch. If necessary, and similarly to the rotor blades 14 of the rotor 9, the base of the stator blades 16 is pivotally mounted about a pitch axis and is connected to a pitch-changing mechanism 15a, which is generally separate from that of the rotor 9, the pitch being adjusted according to the flight phases by the pitch-changing mechanism 15a. The hub of the stator 16 can be fixed to a stator part of the propulsion system 1.

[0049] The blower section 2 can be shrouded or unshrouded.

[0050] In the case of a shrouded blower section 2, the blower section 2 comprises a blower housing 12, centered on the longitudinal axis X, and the rotor 9 is housed in the blower housing 12. A shrouded blower section 2 comprises a rotor 9 extending upstream of a stator 16. The blades 17 of the stator 16 are then generally called "outlet blades" (or "OGV", for "Outlet Guide Vane" in Anglo-Saxon terminology) and have a fixed position relative to the hub of the stator 16.

[0051] In the case of an unfaired fan section 2, the fan section 2, which may also be referred to as the "propeller," is not enclosed by a fan casing. The blades 14 of the rotor 9 also have variable pitch. Propulsion systems 1 comprising at least one unfaired rotor 9 are known, in Anglo-Saxon terminology, as "open rotor" or "unducted fan." The propulsion system 1 may comprise two unfaired, counter-rotating rotors 9. Such a propulsion system 1 is known, in Anglo-Saxon terminology, by the acronym "CROR" for "Contra-Rotating Open Rotor" or "UDF" for "Unducted Double Fan." The rotors 9 can be placed at the rear of the primary body 3 so as to be of the pusher type or at the front of the primary body 3 so as to be of the tractor type.Alternatively, the propulsion system 1 may comprise a single unfaired rotor 9 and an unfaired stator 16 (rectifier). Such a propulsion system 1 is known, in Anglo-Saxon terminology, by the acronym "USF" for "Unducted Single Fan". In the case of a USF-type propulsion system 1, the blades 17 of the rectifier 16 are fixed relative to the stator portion of the propulsion system 1 and, consequently, are not subjected to centrifugal force. The blades 17 of the rectifier 16 are, moreover, variable pitch. Removing the fairing around the fan section 2 allows for a very significant increase in the bypass ratio of the propulsion system 1 without the propulsion system 1 being negatively impacted by the mass of the housings 12 or nacelles intended to surround the fan section 2.

[0052] The compressor section 4, 5 comprises a series of stages, each including a rotating blade wheel (rotor) 4a, 5a rotating in front of a stationary blade wheel (stator) 4b, 5b. The turbine section 7, 8 also comprises a series of stages each comprising a fixed blade wheel (stator) 7b, 8b behind which rotates a moving blade wheel (rotor) 7a, 8a.

[0053] In a twin-spool propulsion system 1, the compressor section 4, 5 comprises a low-pressure compressor 4 and a high-pressure compressor 5, and the turbine section 7, 8 comprises a high-pressure turbine 7 and a low-pressure turbine 8. The rotor stages 5a of the high-pressure compressor 5 are driven in rotation by the rotor stages 7a of the high-pressure turbine 7 via a high-pressure shaft 10. The rotor stages 4a of the low-pressure compressor 4 and the rotor 9 of the blower section 2 are driven in rotation by the rotor stages 8a of the low-pressure turbine 8 via a low-pressure shaft 11. Thus, the primary body 3 comprises a high-pressure body including the high-pressure compressor 5, the high-pressure turbine 7, and the high-pressure shaft 10, and a low-pressure body including the blower section 2, the low-pressure compressor 4, the low-pressure turbine 8, and the shaft low pressure 11.The rotational speed of the high-pressure body is greater than the rotational speed of the low-pressure body.

[0054] In a three-spool propulsion system 1, the turbine section 7, 8 further comprises an intermediate turbine, positioned between the high-pressure turbine 7 and the low-pressure turbine 8, and whose rotor stages are configured to drive the rotor stages 4a of the low-pressure compressor 4 via an intermediate shaft. The rotor 9 of the blower section 2, on the one hand, and the rotor stages 5a of the high-pressure compressor 5, on the other hand, remain driven by the low-pressure shaft 11 and the high-pressure shaft 10, respectively.

[0055] The low-pressure shaft 11 is generally housed, along a portion of its length, within the high-pressure shaft 10 and is coaxial with the high-pressure shaft 10. The low-pressure shaft 11 and the high-pressure shaft 10 may be co-rotating, that is, driven in the same direction around the longitudinal axis X. Alternatively, the low-pressure shaft 11 and the high-pressure shaft 10 may be counter-rotating, that is, driven in opposite directions around the longitudinal axis X. In any case, the high-pressure shaft 10 and the low-pressure shaft 11 each extend along the longitudinal axis X. If applicable, the intermediate shaft is housed between the high-pressure shaft 10 and the low-pressure shaft 11. The intermediate shaft and the low-pressure shaft 11 may be co-rotating or counter-rotating.

[0056] The rotor 9 of the blower section 2 can be decoupled from the low-pressure shaft 11 by means of a torque transmission mechanism 19, placed between the low-pressure shaft 11 and the rotor 9, in order to independently optimize their respective rotational speeds. In this case, the propulsion system 1 further includes an additional shaft 20 (or blower shaft 20). The low-pressure shaft 11 connects the rotor stages 8a of the low-pressure turbine 8 to an inlet of the mechanism torque transmission 19 while the blower shaft 20 connects the output of the torque transmission mechanism 19 to the rotor 9 of the blower section 2. The rotor 9 of the blower section 2 is therefore driven by the low-pressure shaft 11 via the torque transmission mechanism 19 and the blower shaft 20 at a rotational speed lower than the rotational speed of the low-pressure turbine 8. This decoupling makes it possible to reduce the rotational speed and the pressure ratio of the rotor 9 of the blower section 2 and to increase the power extracted by the low-pressure turbine 8.

[0057] In operation, the airflow F entering the propulsion system 1 is divided, by an annular nozzle 300 of the primary body 3, between a primary airflow Fl and a secondary airflow F2, which circulate from upstream to downstream in the propulsion system 1.

[0058] The primary airflow Fl flows in a primary channel 29 defined by the primary body 3, passing successively through the compressor section 4, 5, the combustion chamber 6 where it is mixed with fuel to serve as an oxidizer, and the turbine section 7, 8. The passage of the primary airflow Fl through the turbine section 7, 8 receiving energy from the combustion chamber 6 causes a rotation of the rotor stages 7a, 8a of the turbine section 7, 8, which in turn drives the rotation of the rotor stages 4a, 5a of the compressor section 4, 5 as well as the rotor 9 of the blower section 2.

[0059] The secondary airflow F2, also called the "bypass airflow", flows around the primary body 3. The secondary airflow F2 cools the periphery of the primary body 3 and is used to generate most of the thrust provided by the propulsion system 1.

[0060] Torque transmission mechanism

[0061] The torque transmission mechanism 19 comprises a first shaft 19a (input of the torque transmission mechanism 19), centered on an axis of rotation X' of the torque transmission mechanism 19 generally coincident with the longitudinal axis X and configured to be driven in rotation by the low pressure shaft 11, a second shaft 19b concentric with the first shaft 19a and configured to drive in rotation the blower shaft 20 around the axis of rotation X' of the torque transmission mechanism 19 and a stator 19c having an internal surface 190c delimiting a cavity centered on the axis of rotation X' of the torque transmission mechanism 19.The low-pressure shaft 11 can be mechanically connected to the first shaft 19a by mechanical coupling, or the first shaft 19a can be confused with the low-pressure shaft 11. The blower shaft 20 can be mechanically connected to the second shaft 19b by mechanical coupling, or the second shaft 19b can be confused with the blower shaft 20.

[0062] In the present description, an axial direction corresponds to a direction collinear with the axis of rotation X' of the torque transmission mechanism 19, and a radial direction is a direction orthogonal to the axis of rotation X' of the torque transmission mechanism 19 and intersecting the axis of rotation X' of the torque transmission mechanism 19. Furthermore, an axial plane is a plane parallel to the axis of rotation X' of the torque transmission mechanism 19, and a radial plane is a plane orthogonal to the axis of rotation X' of the torque transmission mechanism 19. A circumference is understood as a circle belonging to a radial plane and whose center lies on the axis of rotation X' of the torque transmission mechanism 19.A tangential or circumferential direction is a direction tangent to a circumference: it is orthogonal to the axis of rotation X' of the torque transmission mechanism 19 but does not pass through the axis of rotation X' of the torque transmission mechanism 19. A circumferential plane is a plane normal to a radial axis, the radial axis being perpendicular to the axis of rotation X' of the torque transmission mechanism 19. Finally, the adjectives "interior" (or "internal") and "exterior" (or "external") are used with reference to a radial direction such that the inner part of an element is, along a radial direction, closer to the axis of rotation X' of the torque transmission mechanism 19 than the outer part of the same element.

[0063] The stator 19c is generally annular in shape, typically crown-shaped. The stator 19c has a thickness, the thickness being measured in a radial plane passing through the stator 19c between the internal surface 190c and an external surface 197c of the stator 19c. The stator 19c also has an internal diameter measured in the same radial plane between the axis of rotation X' of the torque transmission mechanism 19 and the internal surface 190c. A ratio between the thickness of the stator 19c and its internal diameter is between 0.2 and 0.4, preferably between 0.25 and 0.35. The stator 19c extends along the axis of rotation X' of the torque transmission mechanism 19 between two opposite faces, each extending in a radial plane, in order to accommodate a permanent magnet and / or an electromagnet.

[0064] In one embodiment, a groove 191c is formed on the inner surface 190c of the stator 19c, dividing the inner surface 190c into two distinct faces 192c, 194c. The groove 191c includes a bottom, positioned radially external to the inner surface 190c of the stator 19c, such that the groove 191c extends in the radial direction between the inner surface 190c of the stator 19c and the bottom. Furthermore, the bottom has a substantially cylindrical shape. The groove 191c also includes two opposing faces such that the groove 191c extends in the axial direction between the two opposing faces of the groove 191c. Thus, the groove 191c forms an annular cavity in which an electromagnet can be housed.

[0065] In one embodiment, the inner surface 190c further comprises two plurality of notches 193c, 195c extending over the inner surface 190c over a circumference of the rotor 19c, for example on either side of the groove 191c. Each notch 193c, 195c of the respective plurality of notches 193c, 195c comprises a bottom, in a radially external position relative to the inner surface 190c of the rotor 19c, so that the notch 193c, 195c extends in the radial direction between the inner surface 190c of the stator 19c and the bottom. The bottom has a substantially cylindrical shape and extends over a portion of the rotor 19c between two opposite faces extending in distinct axial planes so that the bottom extends circumferentially between the two axial planes.Each notch 193c, 195c extends longitudinally along the axis of rotation X' of the torque transmission mechanism 19 and opens onto one of the opposite faces of the groove 191c and one of the opposite faces of the stator 19c. Therefore, the internal surface 190c of the stator 19c has a generally grooved shape, and a coil can be wound in each of the plurality of notches 193c, 195c. Alternatively, the stator 19c may have only one plurality of notches 193c, 195c. The internal surface 190c is thus devoid of notches 193c, 195c on one of the two faces 192c, 194c separated by the groove 191c.

[0066] The stator 19c is formed from a highly permeable ferromagnetic material (generally an iron, iron-silicon, iron-cobalt, or iron-nickel alloy). The stator 19c may be solid or laminated to reduce eddy current losses. The groove 191c and the slots 193c, 195c are obtained by material removal, typically by machining.

[0067] The torque transmission mechanism 19 further includes a magnetic generation device 50 attached to the stator 19c and configured to generate a first magnetic field.

[0068] The magnetic generation device 50 may include a permanent magnet 53, 55 and / or an electromagnet 52, 54 in direct electric current.

[0069] The term "electromagnet" refers to an assembly comprising a coil wound around a magnetic core made of ferromagnetic material. The coil may be formed of a plurality of turns wound around the magnetic core. Unlike permanent magnets, it does not exhibit natural magnetization, and a magnetic field is created by the flow of an electric current through the coil.

[0070] The term "permanent magnet" refers to a magnetic material that exhibits natural magnetization in the absence of a magnetic field created by an external magnetic source. In other words, permanent magnets remain magnetized after the removal of a magnetizing field. This is also referred to as remanent magnetization.

[0071] In one embodiment, the magnetic generation device 50 comprises permanent magnets 53, 55 housed on the inner surface of the rotor 19c. For example, a first plurality of permanent magnets 53, 55 is housed at the level of one of the two faces 192c, 194c separated by the groove 191c and a second plurality of permanent magnets 53, 55 is housed at the level of the other face of the two faces 192c, 194c separated by the groove 191c.

[0072] In one embodiment, the stator 19c comprises electromagnets 52, 54. Coils are wound in the slots 193c, 195c and the stator 19c acts as the magnetic core. Alternatively, in the case where the inner surface 190c is devoid of slots 193c, 195c on one of the two faces 192c, 194c separated by the groove 191c, the face 192c, 194c devoid of slots 193c, 195c comprises a plurality of permanent magnets 53, 55.

[0073] The electromagnet 52, 54 of the magnetic generation device 50 allows control of the torque transmitted between the first shaft 19a and the second shaft 19b. Indeed, by controlling the supply current of the electromagnet 52, 54, it is possible to modulate the field generated by the device 50 and therefore the torque transmitted between the first and second shafts 19a, 19b. It is thus possible, thanks to the electromagnet 52, 54, to control the transmissible torque for different speed regimes of the aircraft 100. Another advantage of the electromagnet 52, 54 is that it allows the use of fewer rare earth elements while remaining suitable for high-speed applications. As for the permanent magnet 53, 55 of the magnetic generation device 50, it improves the transmissible torque density of the torque transmission mechanism 19.

[0074] The torque transmission mechanism 19 further comprises a magnetic excitation device 51. In the present description, the magnetic excitation device 51 differs from the magnetic generation device 50 in that the magnetic generation device 50 generates a magnetic field produced at the stator 19c of the torque transmission mechanism 19 (“first magnetic field”), whereas the magnetic excitation device 51 generates a magnetic field produced by the first shaft 19a of the torque transmission mechanism 19 (“second magnetic field”). Moreover, the second magnetic field is synchronized with the first magnetic field. That is to say, at least one spectral line of the second magnetic field has a frequency equal to that of a spectral line of the first magnetic field.In other words, the spectral decomposition of the first magnetic field and the spectral decomposition of the second magnetic field share a common line. To achieve this, the second tree 19b modulates the second magnetic field by introducing spatial harmonics into the spectrum of the second magnetic field, one of which is common with a line in the spectrum of the first magnetic field, and vice versa. versa. This synchronicity is at the origin of the transmissible couple between the first and second trees 19a, 19b.

[0075] The magnetic excitation device 51 may in particular include an electromagnet powered by direct electric current.

[0076] The electromagnet of the magnetic excitation device 51 can be fixed to the stator 19c. For example, a coil of circular turns collinear with the axis of rotation of the torque transmission mechanism 19 and extending in the groove 191c around the entire circumference of the stator 19c. The stator 19c acts as the iron core in the electromagnet of the magnetic excitation device 51.

[0077] Alternatively, the electromagnet of the magnetic excitation device 51 can be fixed to the first shaft 19a, the first shaft 19a acting as the iron core in the electromagnet of the magnetic excitation device 51.

[0078] Since the magnetic excitation device 51 is supplied with direct current to excite the first shaft 19a, it can be switched on and off. Therefore, switching off the magnetic excitation device 51 allows the first shaft 19a and the second shaft 19b to be decoupled. That is to say, the rotation of the first shaft 19a and the rotation of the second shaft 19b are independent when the magnetic excitation device 51 is switched off. Thus, the maintenance of the transmission mechanisms 19 is improved. Indeed, it is possible to perform maintenance operations on the two shafts 19a and 19b independently of each other. The electromagnet of the magnetic excitation device 51 also allows the torque transmitted between the first shaft 19a and the second shaft 19b to be controlled.Indeed, by controlling the direct current supplying the electromagnet, it is possible to modulate the field generated by the first shaft 19a and therefore the torque transmitted between the first and second shafts 19a, 19b. It is therefore possible, thanks to the electromagnet, to control the transmissible torque for different aircraft speed regimes.

[0079] It is also possible to control the torque transmitted between the first shaft 19a and the second shaft 19b by the electromagnet of the magnetic generation device 50 and by the electromagnet of the magnetic excitation device 51. Thus, by combining two controls of the torque transmitted between the first shaft 19a and the second shaft 19b, the accuracy and reliability of the control of the torque transmitted between the first shaft 19a and the second shaft 19b is improved.

[0080] The first shaft 19a extends along the axis of rotation X' of the torque transmission mechanism 19 within the cavity delimited by the internal surface 190c. The first shaft 19a has a plurality of shoulders 191a projecting from the first shaft 19a, which is configured to generate the second magnetic field following the excitation of the magnetic excitation device 51. In this case, the first shaft 19a has a base 190a, substantially cylindrical in shape, and shoulders 191a, forming cylindrical sections and extending from the base 190a. The shoulders 191a can be arranged in pairs, and the two shoulders 191a of each pair are arranged symmetrically around the axis of rotation X' of the torque transmission mechanism 19 with respect to an axial plane passing through the axis of rotation of the torque transmission mechanism 19. The pairs of shoulders 191a therefore extend on either side of the first shaft 19a in the same plane. Furthermore, the planes in which the pairs of shoulders 191a extend are angularly offset around the axis of rotation X' of the torque transmission mechanism 19. For example, the first shaft 19b comprises two pairs of shoulders 191a (therefore four shoulders 191a) offset by 90° from each other around the axis of rotation X' of the torque transmission mechanism 19.Each pair of shoulders 191a is polarized to the North or South pole depending on the direction of the field lines of the second magnetic field generated by the first shaft 19a following the excitation of the magnetic excitation device 51, and thus forms magnetic poles. Each pair of shoulders 191a is opposite the magnetic generation device 50. In one embodiment, each pair of shoulders 191a is opposite one of the first and second pluralities of permanent magnets 53, 55. In another embodiment, each pair of shoulders 191a is opposite one of the pluralities of notches 193c, 195c.

[0081] Alternatively, the shoulders 191a may be arranged in two rows, each row of shoulders 191a comprising at least two shoulders 191a, typically three shoulders 191a, or even four shoulders 19a.The shoulders 191a of each row of shoulders 191a are mutually offset angularly around the axis of rotation X' of the torque transmission mechanism 19. For example, in the case where each row of shoulders 191a comprises three shoulders 191a, the three shoulders 191a are mutually offset by 120° to each other around the axis of rotation X' of the torque transmission mechanism 19 and two circumferentially adjacent shoulders 191a belonging respectively to a first row of shoulders 191a of the two rows of shoulders 191a and a second row of shoulders 191a of the two rows of shoulders 191a are angularly offset by 60°.In the case where each row comprises four shoulders 191a, the four shoulders 191a are mutually offset by 90° around the axis of rotation X' of the torque transmission mechanism 19, and two circumferentially adjacent shoulders 191a belonging respectively to a first row of shoulders 191a of the two rows of shoulders 191a and a second row of shoulders 191a of the two rows of shoulders 191a are angularly offset by 45°. Each row of shoulders 191a is polarized to the North pole or the South pole according to the direction of the field lines of the second magnetic field generated by . The first shaft 19a is excited by the magnetic excitation device 51 and thus forms magnetic poles. Each row of shoulders 191a is opposite the magnetic generation device 50. Alternatively, each row of shoulders 191a is opposite one of the first and second pluralities of permanent magnets 53, 55. According to another variant, each row of shoulders is opposite one of the pluralities of notches 193c, 195c.

[0082] The first shaft 19a is therefore devoid of permanent magnets, which reduces air gap variations related to the shrink-fitting of magnets on the first shaft 19a. There is also no longer a risk of demagnetization caused by heating the first shaft 19a at high speed. The torque transmissible by the torque transmission mechanism 19 is thus improved, and consequently, so is the efficiency of the torque transmission mechanism 19. Another advantage is that fewer rare earth elements are used to excite the first shaft 19a while still remaining suitable for high-speed applications.

[0083] In the case where the electromagnet is integral with the stator 19c, the first shaft 19a is also devoid of electromagnets. Thus, the robustness of the first shaft 19a is improved and, consequently, the operating speed range of the first shaft 19a is also improved.

[0084] The second shaft 19b extends along the axis of rotation X' of the torque transmission mechanism 19 within the cavity defined by the internal surface 190c. The second shaft 19b is substantially cylindrical in shape and has two rows of axially offset studs 190b. The studs 190b in each row are arranged circumferentially around the axis of rotation X' of the torque transmission mechanism 19. The studs 190b are separated from each other by a constant angle measured between a first face of a first stud 190b and a second face of a second stud 190b opposite the first face of the first stud 190b. For example, the second shaft 19b comprises two rows of studs 190b, and each of the two rows of studs 190b comprises eighteen studs 190b. Each of the two rows of studs 190b is opposite the magnetic generation device 50.According to one embodiment, each row of studs 190b is opposite one of the first and second pluralities of permanent magnets 53, 55. According to another embodiment, each row of studs 190b is opposite one of the pluralities of slots 193c, 195c. The studs 190b can be held at a distance from the first shaft 19a and the stator 19c, as well as from each other, by means of a support structure mechanically connected by coupling to the second shaft 19b or integrated with the second shaft 19b. The support structure can, for example, be crown-shaped. The studs 109b are then mounted on the hub. The hub material is typically electrically insulated and non-ferromagnetic, for example, plastic or fiber. The second shaft 19b and the first shaft 19a. are concentric and the studs 190b extend around a circumference with a diameter greater than a diameter of the first shaft 19a taken between two shoulders 191a of a pair of shoulders 191a of the first shaft 19a. The first shaft 19a is therefore surrounded by the second shaft 19b. Thus, moving away from the axis of rotation X' of the torque transmission mechanism 19, each row of studs 190b of the second shaft 19b is interposed between the magnetic generation device 50 and the respective pair of shoulders 191a of the first shaft 19a.

[0085] The first and second shafts 19a, 19b are formed from a highly permeable ferromagnetic material (generally an iron, iron-silicon, iron-cobalt, or iron-nickel alloy). The first and second shafts 19a, 19b may be solid or laminated to reduce eddy current losses.

[0086] Relationships between the magnetic pole pairs of the magnetic generation device, the pads and the magnetic pole pairs of the first shaft

[0087] In order to synchronize the second magnetic field with the first magnetic field so as to transmit a torque between the first shaft 19a and the second shaft 19b, the number of magnetic pole pairs Ps of the magnetic generation device 50, the number of studs Pr1 of a row of studs 190b and the number of magnetic pole pairs 1 / 2 formed by the shoulders 191a of the first shaft 19a are related by the following relation: Ps ~ PrrPr2-

[0088] For example, p.— 18 if Pr1 = 20 and Pr2 = 2.

[0089] A transformation ratio G between a rotational speed of the first shaft 19a and a rotational speed of the second shaft 19b is given by the following relation: ~ ~ Pr2

[0090] with the rotation speed of the first shaft 19a and ilr2 the rotation speed of the second shaft 19b.

[0091] For example, for the previous values, G = 10.

[0092] Hybridization of the propulsion system

[0093] The propulsion system 1 further includes an electrical network 22 configured to carry electrical power within the propulsion system 1. The electrical network 22 may be of the high-voltage direct current (HVDC) type. For example, the operating voltage of the electrical network 22 may be 540 V. In this respect, the electrical network 22 is configured to operate at a constant voltage (the operating voltage of the electrical network 22).

[0094] The propulsion system 1 also includes a power supply device 200 connected to the electrical network 22. The propulsion system 1 may include several power supply devices 200 connected in parallel to the electrical network 22. The device The power supply 200 includes an electric machine 21. In the case of a dual-body propulsion system 1, the rotor of the electric machine 21 is configured to be connected to the low-pressure shaft 11 or the high-pressure shaft 10. The power supply 200 may further include a second electric machine 21. The propulsion system 1 may further include two power supply 200s, each comprising an electric machine 21 connected to one of the low-pressure shaft 11 and high-pressure shaft 10. In general, the propulsion system 1 may include one or more electric power supply 200s, each comprising one or more electric machines 21 connected to a separate shaft of the propulsion system 1. The electric machines 21 may also be electrically interconnected.For example, a first electrical machine 21 connected to the low pressure shaft 11 can be electrically connected to a second electrical machine 21 connected to the high pressure shaft 10.

[0095] The power supply device 200 further includes electrical conversion means 23, typically an AC / DC converter, particularly when the electrical network is of the direct current type.

[0096] Electric machine

[0097] The electric machine 21 comprises a stator and a rotor that rotates relative to the stator 19c around an axis of rotation X” of the electric machine 21. The electric machine 21 is configured to perform a constant power electromechanical conversion between mechanical energy at the rotor and electrical energy at the stator.

[0098] By "electromechanical conversion" we mean a conversion of electrical energy into mechanical energy, and vice versa, from an intermediate form of energy called "magnetic energy" resulting from the principle of conservation of energy applied to the electrical machine.

[0099] In the present exposition, the definitions given above for the directions and planes with respect to the axis of rotation X' of the torque transmission mechanism 19 remain valid with respect to the axis of rotation X” of the electric machine 21. The same applies to the adjectives “interior” (or “internal”) and “exterior” (or “external”) as well as the term “circumference”.

[0100] The electric machine 21 is reversible, that is to say, it is configured to operate as an electric generator at any rotational speed of the propulsion system 1, typically when connected to the low-pressure shaft 11, and / or as an electric motor, typically when connected to the high-pressure shaft 10. The power supply device 200 is configured to supply the electrical network 22 by drawing power from each shaft, typically the low-pressure shaft 11 and the high-pressure shaft 10, when both electric machines 21 are in generator mode. and to implement a power transfer, typically from the low pressure shaft 11 to the high pressure shaft 10, when one of the electrical machines 21 connected respectively to the low pressure shaft 11 and the high pressure shaft 10 is in electric motor mode and the other of the electrical machines 21 connected respectively to the low pressure shaft 11 and the high pressure shaft 10 is in electric generator mode.

[0101] The electric machine 21 may further comprise a torque transmission mechanism 19 of the same type as the aforementioned torque transmission mechanism 19 (the same reference numeral will therefore be used). The electric machine 21 is thus simultaneously a speed reducer (or even a speed multiplier), thanks to the torque transmission mechanism 19, a generator, and a motor due to its reversibility and electromechanical conversion.

[0102] In this case, the electrical machine 21 comprises a plurality of electromagnets 57 fixed to the stator 19c of the torque transmission mechanism 19 and supplied by electric currents, preferably sinusoidal. For example, the stator 19c further has an external surface 197c extending around the internal surface 190c, a first plurality of teeth 198c extending radially between the internal surface 190c and the external surface 197c and being aligned in a first plane, and a second plurality of teeth 198c extending radially between the internal surface 190c and the external surface 197c and being aligned in a second plane offset axially with respect to the first plane.The plurality of electromagnets 57 comprises a first row of electromagnets, each electromagnet of the first row of electromagnets being fixed to a respective tooth 198c of the first plurality of teeth 198c, and a second row of electromagnets, each electromagnet of the second row of electromagnets being fixed to a respective tooth 198c of the second plurality of teeth 198c.

[0103] In one variant, the external surface 197c is concentric with the internal surface 190c.

[0104] The plurality of electromagnets 57 is configured to generate a third magnetic field. To this end, the plurality of electromagnets 57 may comprise three electromagnets (per row in the case where the electromagnets of the plurality of electromagnets are distributed over several rows as stated in the example above), or even a multiple of three in the case of several pole pairs, for example, six electromagnets, supplied by sinusoidal currents. The electromagnets are distributed around the axis of rotation X” of the electrical machine 21 so that the sinusoidal currents form a balanced three-phase electric current system, i.e., the three electromagnets are supplied by three sinusoidal currents having the same RMS value and phase-shifted by an angle value of 120°.

[0105] By "effective value" of a quantity, we mean the square root of an average of the quantity raised to the square.

[0106] In one variant, the rotor of the electric machine 21 can be mechanically connected to the torque transmission mechanism 19 by mechanical coupling of the rotor of the electric machine and the first shaft 19a of the torque transmission mechanism 19.

[0107] In one embodiment, the rotor of the electric machine 21 and the first shaft 19a of the torque transmission mechanism 19 can be combined. For example, the first shaft 19a extends at least from the first row of electromagnets of the plurality of electromagnets 57 to the second row of electromagnets of the plurality of electromagnets 57. Thus, by integrating the torque transmission mechanism 19 into the same volume as the electric machine 21, the respective sizes of the electric machine 21 and the torque transmission mechanism 19 are reduced.

[0108] Furthermore, the second magnetic field is synchronized with the third magnetic field. That is to say, a rotational speed of the first shaft 19a (in rad / s) is equal to an angular frequency of the currents supplying the plurality of electromagnets 57 (also in rad / s), up to the number of pole pairs of the first shaft 19a. In other words, the electromagnets of the plurality of electromagnets 57 are supplied by currents with an angular frequency equal to the product of the rotational speed of the first shaft 19a and the number of pole pairs of the first shaft 19a. This synchronism is the basis for the electromechanical conversion between the mechanical energy of the first shaft 19a and the electrical energy of the plurality of electromagnets 57.

[0109] The second magnetic field generated by the first shaft 19a is therefore synchronized with the third magnetic field generated by the plurality of electromagnets 57 and the first magnetic field generated by the magnetic generation device 50 of the torque transmission mechanism 19.

[0110] Furthermore, the second magnetic field is simultaneously synchronized with the third magnetic field generated by the plurality of electromagnets 57 and the first magnetic field generated by the magnetic generation device 50 of the torque transmission mechanism 19. Indeed, a pulsation of the first magnetic field and the pulsation of the supply currents of the plurality of electromagnets 57 are equal to the rotational speed of the first shaft 19a, up to the number of pole pairs of the first shaft 19a. Thus, the torque supplied by the electric machine 21 is a function of the transformation ratio G, which, in the present application, is greater than 1. The volume torque density of the electric machine 21 is therefore improved and can expect A value exceeding 60 kNm / m³ is achieved, and the power factor is also improved to a value exceeding 0.9. The footprint of the electric machine 21 is therefore reduced. The footprint of the high-pressure turbines 7 and / or low-pressure turbines 8 of the propulsion system is also reduced. Consequently, the mass of the propulsion system 1 is also reduced. The efficiency of the propulsion system 1 is therefore improved.

[0111] The plurality of electromagnets 57 also allows control of the torque transmitted between the first shaft 19a and the second shaft 19b. Indeed, by controlling the supply currents of the plurality of electromagnets 57, it is possible to modulate the third magnetic field and thus the electromechanical conversion. It is therefore possible, thanks to the plurality of electromagnets 57, to control the torque of the first shaft 19a for different speed regimes of the aircraft 100. Various strategies for controlling the supply currents of the plurality of electromagnets 57, in particular so-called "vector" controls, can, in this respect, be considered.

[0112] It is also possible to control the torque transmitted between the first shaft 19a and the second shaft 19b by the electromagnet of the magnetic generation device 50, by the electromagnet of the magnetic excitation device 51 and by the plurality of electromagnets 57 of the electric machine 21. Thus, by combining three controls of the torque transmitted between the first shaft 19a and the second shaft 19b, the accuracy and reliability of the control of the torque transmitted between the first shaft 19a and the second shaft 19b is further improved.

[0113] Several advantageous operating modes of the electric machine 21 including the torque transmission mechanism 19 can be envisaged and are detailed below.

[0114] In a first mode of operation, the electric machine 21 is deactivated, i.e. the power supply device 200 of the electric machine 21 is in open circuit and the electric machine 21 does not supply the electrical network 22 of the aircraft.

[0115] Thus, risks of overvoltage on the electrical network 22 caused by a loss of control of the electrical machine 21, an electrical fault, or by an extreme high or low speed of the low pressure shaft 11 are reduced while continuing to control the blower 2 by the torque transmission mechanism.

[0116] In a second operating mode, the electric machine 21 is in motor mode. That is to say, electrical energy from the electrical network 22 and / or another electric machine 21 is converted into mechanical rotational energy at the first shaft 19a by electromechanical conversion. Thus, the available mechanical energy can be transmitted, in particular, to the blower shaft 20. Therefore, the dilution ratio of the propulsion system, defined as the ratio of the secondary airflow F2 to the primary airflow Fl, can be increased. The efficiency of the propulsion system is therefore improved. It can also be transmitted to the high-pressure shaft 10. It is also transmitted to the low-pressure shaft 11 and / or the high-pressure shaft 10. The size of the high-pressure turbine 7 and / or the low-pressure turbine 8 is then reduced. The mass of the propulsion system 1 is therefore also reduced. The efficiency of the propulsion system 1 is therefore improved.

[0117] In a third operating mode, the electric machine is in generator mode. That is to say, mechanical rotational energy at the first shaft 19a is converted into electrical energy injected into the electrical network 22 (for example to recharge a battery) and / or to another electric machine 21 in motor mode by electromechanical conversion.

Claims

Demands

1. An electrical machine (21) comprising: a stator (19c) having an internal surface (190c) delimiting a cavity centered on an axis of rotation (X”) of the electrical machine; a plurality of first electromagnets (57) configured to generate a first magnetic field, the plurality of first electromagnets (57) being fixed to the stator (19c); a magnetic generation device (50) configured to generate a second magnetic field, the magnetic generation device (50) being fixed to the stator (19c); a magnetic excitation device (51); and a first shaft (19a) extending within the cavity along the axis of rotation (X”); and a second shaft (19b) extending within the cavity, along the axis of rotation (X”), being concentric with the first shaft (19a);in which one of the first and second shafts (19a, 19b) is configured to generate a third magnetic field, following excitation by the magnetic excitation device (51), the third magnetic field being synchronized with: the first magnetic field so as to implement an electromechanical conversion between a mechanical power from one of the first shafts (19a) and the second shaft (19b), and an electrical power from the plurality of first electromagnets (57); and the second magnetic field so as to transmit a torque between the first shaft (19a) and the second shaft (19b).

2. Electric machine (21) according to claim 1, wherein the magnetic excitation device (51) comprises a second electromagnet.

3. Electric machine (21) according to any one of claims 1 and 2, wherein the magnetic generation device (50) comprises a permanent magnet.

4. Electric machine (21) according to any one of claims 1 to 3, wherein the magnetic generation device (50) comprises a third electromagnet.

5. An electrical machine (21) according to any one of claims 1 to 4, wherein the plurality of first electromagnets (57) is configured to control the electromechanical conversion as a function of supply currents of the plurality of first electromagnets (57).

6. Electric machine (21) according to any one of claims 1 to 3, wherein the stator (19c) has an external surface (197c) extending around the internal surface (190c); the stator (19c) further comprising a first plurality of teeth (198c) extending radially between the internal surface (190c) and the external surface (197c) and being aligned in a first plane, and a second plurality of teeth (198c) extending radially between the internal surface and the external surface and being aligned in a second plane offset axially with respect to the first plane;in which: the plurality of first electromagnets (57) comprises a first row of first electromagnets, each first electromagnet of the first row of first electromagnets being fixed to a respective tooth (198c) of the first plurality of teeth (198c), and a second row of first electromagnets, each first electromagnet of the second row of first electromagnets being fixed to a respective tooth (198c) of the second plurality of teeth (198c); the magnetic generation device (50) comprises a first plurality of permanent magnets fixed to the inner surface (190c) and aligned in the first plane, and a second plurality of permanent magnets fixed to the inner surface of the stator and aligned in the second plane; and the magnetic excitation device (51) comprises a second electromagnet fixed to the inner surface of the stator (19c) and positioned axially between the first plane and the second plane.

7. An aeronautical propulsion system (1) comprising: a first drive shaft (11) rotatable about an axis of rotation (X) of the propulsion system (1); a fan shaft (20); an aircraft electrical network (22); and a first electrical machine (21) according to any one of claims 1 to 6, wherein: the first drive shaft (11) is connected to one of the first shaft (19a) and the second shaft (19b) of the first electric machine (21); the blower shaft (20) is connected to the other of the first shaft (19a) and the second shaft (19b) of the first electric machine (21); and the electrical network (22) is electrically connected to the plurality of first electromagnets (57) of the first electric machine (21).

8. Aeronautical propulsion system (1) according to claim 7, wherein the first electric machine (21) is a motor configured to drive one of the first shaft (19a) and the second shaft (19b) in rotation about the axis of rotation (X”) from electrical power supplied by the electrical network (22).

9. Aeronautical propulsion system (1) according to claim 7, wherein the first electrical machine (21) is a generator configured to inject electrical power into the electrical network (22) from mechanical power supplied by one of the first shaft (19a) and the second shaft (19b).

10. An aeronautical propulsion system (1) according to any one of claims 7 to 9, further comprising: a second drive shaft (10), the second drive shaft being configured to rotate at a speed of rotation about the axis of rotation (X) of the propulsion system (1) different from a speed of rotation, about the axis of rotation (X) of the propulsion system (1), of the first drive shaft (11); and a second electric machine (21) according to any one of claims 1 to 9, wherein: the second drive shaft (10) is connected to one of the first shaft (19a) and the second shaft (19b) of the second electric machine (21), the other of the first shaft (19a) and the second shaft (19b) being free;and the electrical network (22) and the plurality of first electromagnets (57) of the first electrical machine (21) are electrically connected to the plurality of first electromagnets (57) of the second electrical machine (22).;