Magnetic gear torque transmission mechanism

Abstract

The present description relates to a magnetic gear torque transmission mechanism (19) comprising: a stator (19c) having an internal surface (190c) delimiting a cavity centered on an axis of rotation (X') of the torque transmission mechanism (19); a magnetic generation device (50) configured to generate a first magnetic field, the magnetic generation device (50) being fixed to the stator (19c); a magnetic excitation device (51); 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 second magnetic field, following excitation by the excitation device (51), the second magnetic field being synchronized with the first magnetic field so as to transmit a torque between the first shaft (19a) and the second shaft (19b). Figure for the abstract: Figure 4a;

Description

Title of the invention: Magnetic gear torque transmission mechanism technical field

[0001] The present exposition relates to torque transmission mechanisms, in particular magnetic gears. 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 torque transmission mechanisms, on which the Applicant is working, operate through the interaction between permanent magnets. For example, a magnetic gear comprises permanent magnets positioned at the level of the external surface of its input shaft which interact with other permanent magnets positioned at the level of 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 the present exposition is to propose a magnetic gear torque transmission mechanism 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] For this purpose, according to a first aspect of the present exposition, a magnetic gear torque transmission mechanism is proposed comprising: a stator having an internal surface delimiting a cavity centered on an axis of rotation of the torque transmission mechanism; a magnetic generation device configured to generate a first magnetic field, the magnetic generation device being attached to the stator; a magnetic excitation device; 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 shaft and the second shaft is configured to generate a second magnetic field, following excitation by the excitation device, the second magnetic field being synchronized with the first magnetic field so as to transmit a torque between the first shaft and the second shaft.

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

[0014] It can be provided that the one of the first tree and the second tree which is configured to generate a second magnetic field, is further configured to present at least two pairs of magnetic poles following excitation by the magnetic excitation device.

[0015] 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 second magnetic field, the plurality of shoulders forming pairs of magnetic poles following excitation by the magnetic excitation device.

[0016] It may be provided that the magnetic generation device includes a permanent magnet.

[0017] It may be provided that the magnetic excitation device includes a first electromagnet.

[0018] It may be provided that the magnetic generation device includes a second electromagnet.

[0019] It may be provided that at least one of the first and second electromagnets is configured to control the torque transmitted between the first shaft and the second shaft as a function of a supply current to at least one of the first and second electromagnets.

[0020] It may be provided that the magnetic excitation device does not include the first electromagnet.

[0021] It may be provided that the magnetic generation device comprises a first plurality of permanent magnets fixed to the internal surface of the stator and aligned in a first plane, and a second plurality of permanent magnets fixed to the internal surface of the stator and aligned in a second plane offset axially with respect to the first plane; and the magnetic excitation device comprises an 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 drive shaft; a blower shaft; and a magnetic gear torque transmission mechanism according to the first aspect, in which the drive shaft is connected to one of the first and second shafts and the blower shaft is connected to the other of the first and second shafts.

[0023] 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

[0024] 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:

[0025] Fig. 1 illustrates an example of an aircraft that may include a propulsion system.

[0026] 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.

[0027] Fig. 3 is a schematic, partial, cross-sectional view of an example of a twin-body, dual-flow propulsion system in which the fan section is unfaired.

[0028] Fig. 4a and Fig. 4b are schematic isometric views of magnetic gear torque transmission mechanisms.

[0029] Fig. 5a and Fig. 5b are schematic isometric views of a stator of magnetic gear torque transmission mechanisms.

[0030] Fig. 6a and Fig. 7a are schematic isometric cross-sectional views of magnetic gear torque transmission mechanisms.

[0031] Fig. 6b and Fig. 7b are schematic front views in longitudinal section of magnetic gear torque transmission mechanisms.

[0032] Fig. 8 is an isometric schematic view of a first shaft of a magnetic gear torque transmission mechanism.

[0033] Fig. 9 is an isometric schematic view of a second shaft of a magnetic gear torque transmission mechanism. DETAILED DESCRIPTION

[0034] We detail below an example of the application of the transmission mechanism of magnetic gear torque, in this case in the field of aeronautics. Of course, the torque transmission mechanism of this application can be suitable for other electromechanical conversion chains, particularly in the automotive or rail sectors, or even wind power, and is therefore not limited to aircraft.

[0035] Aircraft

[0036] 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.

[0037] Propulsion system

[0038] 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 a system aeronautical propulsion 1 configured to be fixed to the airframe of aircraft 100 by means of a pylon (or mast), which is fixed to the airframe of aircraft 100.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] The fan section 2 may further include a stator 16, or rectifier, which comprises blades 17 mounted on a stator hub 16 and whose function is to rectify an airflow F2 exiting the rotor 9. The stator blades 17 may be fixed relative to the stator hub 16 or have variable pitch. If so, and similarly to the rotor blades 14 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 stator hub 16 may be fixed to a stator portion of the propulsion system 1.

[0043] The blower section 2 can be shrouded or unshrouded.

[0044] 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.

[0045] In the case of an unshrouded fan section 2, the fan section 2, which can also be referred to as the "propeller", is not surrounded by a casing of the blower. The blades 14 of the rotor 9 also have variable pitch. Propulsion systems 1 comprising at least one unducted rotor 9 are known, in Anglo-Saxon terminology, as "open rotor" or "unducted fan". The propulsion system 1 may comprise two unducted, 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 may be positioned at the rear of the primary casing 3 so as to be of the pusher type or at the front of the primary casing 3 so as to be of the tractor type. Alternatively, the propulsion system 1 may include a single unshod rotor 9 and an unshod 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, do not experience centrifugal force. The blades 17 of the rectifier 16 also have 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.

[0046] The compressor section 4, 5 comprises a series of stages, each including a rotating blade wheel (rotor) 4a, 5a in front of a fixed blade wheel (stator) 4b, 5b. The turbine section 7, 8 also comprises a series of stages, each including a fixed blade wheel (stator) 7b, 8b behind which a rotating blade wheel (rotor) 7a, 8a rotates.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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 comprises 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 input of the torque transmission mechanism 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 pressure ratio of the rotor 9 of the blower section 2 and to increase the power extracted by the low pressure turbine 8.

[0051] 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.

[0052] 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 to through turbine section 7, 8 receiving energy from combustion chamber 6 causes a rotation of rotor stages 7a, 8a of turbine section 7, 8, which in turn drives into rotation the rotor stages 4a, 5a of compressor section 4, 5 as well as the rotor 9 of blower section 2.

[0053] 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.

[0054] Torque transmission mechanism

[0055] The torque transmission mechanism may include a magnetic gear torque transmission mechanism 19.

[0056] 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 coinciding 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 considered as 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.

[0057] 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 so that the inner part of an element is, following a radial direction, closer to the axis of rotation X' of the torque transmission mechanism 19 than the outer part of the same element.

[0058] 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.

[0059] 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.

[0060] 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 notch. only plurality of notches 193c, 195c. The internal surface 190c is therefore devoid of notches 193c, 195c on one of the two faces 192c, 194c separated by the groove 191c.

[0061] The stator 19c is formed from a ferromagnetic material with high permeability (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.

[0062] 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.

[0063] The magnetic generation device 50 may include a permanent magnet 53, 55 and / or an electromagnet 52, 54 in direct electric current.

[0064] 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.

[0065] 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 the magnetic field is created by the flow of an electric current through the coil.

[0066] In one embodiment, the magnetic generation device 50 comprises permanent magnets 53, 55 housed at the internal surface of the rotor 19c. For example, a first plurality of permanent magnets 53, 55 is housed at 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 other face of the two faces 192c, 194c separated by the groove 191c.

[0067] In one embodiment, the stator 19c comprises electromagnets 52, 54. Coils are wound in 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.

[0068] 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 therefore possible, thanks to the electromagnet 52, 54 to control the transmissible torque for different aircraft speed regimes 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.

[0069] 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 its spectrum, one of which is common to a line in the spectrum of the first magnetic field, and vice versa. This synchronicity is the origin of the transmissible torque between the first and second trees 19a, 19b.

[0070] The magnetic excitation device 51 may in particular include an electromagnet powered by direct electric current.

[0071] 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.

[0072] 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.

[0073] 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, a rotation of the first shaft The rotation of shaft 19a and the second shaft 19b are independent when the magnetic excitation device 51 is deactivated. This improves maintenance of the transmission mechanisms 19. Maintenance operations can be performed on both shafts 19a and 19b independently. The electromagnet of the magnetic excitation device 51 also allows control of the torque transmitted between the first shaft 19a and the second shaft 19b. By controlling the direct current supplying the electromagnet, it is possible to modulate the field generated by the first shaft 19a and thus the torque transmitted between the first and second shafts 19a and 19b. Therefore, the electromagnet allows control of the transmissible torque for different aircraft speeds.

[0074] 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.

[0075] The first shaft 19a extends along the axis of rotation X' of the torque transmission mechanism 19 in the cavity delimited by the internal surface 190c. The first shaft 19a has a plurality of shoulders 191a extending outward 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 shoulder pairs 191a extend are angularly offset around the rotation axis 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 rotation axis 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. According to... In one variant, each pair of shoulders 191a is opposite one of the first and second pluralities of permanent magnets 53, 55. According to another variant, each pair of shoulders 191a is opposite one of the pluralities of notches 193c, 195c.

[0076] 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 in each row of shoulders 191a are mutually offset angularly about 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° 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 45°.Each row of shoulders 191a is polarized to 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 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.

[0077] 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.

[0078] 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.

[0079] 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.In one embodiment, each row of studs 190b is opposite one of the first and second pluralities of permanent magnets 53, 55. In 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 ring-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.

[0080] 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.

[0081] Relationships between the magnetic pole pairs of the magnetic generation device, the pads and the magnetic pole pairs of the first shaft

[0082] 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 generating device magnetic 50, the number of studs Pr in a row of studs 190b and the number of magnetic pole pairs Pri formed by the shoulders 191a of the first shaft 19a are related by the following relation: Ps~ PrrPr2-

[0083] For example, p.— 18 if Pr1 = 20 and Pr2 = 2.

[0084] 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: - 0^2 - Pr2

[0085] with the rotation speed of the first shaft 19a and the rotation speed of the second shaft 19b.

[0086] For example, for the previous values, G = 10.

Claims

Demands

1. Magnetic gear torque transmission mechanism (19) comprising: a stator (19c) having an internal surface (190c) defining a cavity centered on an axis of rotation (X') of the torque transmission mechanism (19); a magnetic generation device (50) configured to generate a first magnetic field, the magnetic generation device (50) being integral with the stator (19c); a magnetic excitation device (51); 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 second magnetic field, following excitation by the excitation device (51), the second magnetic field being synchronized with the first magnetic field so as to transmit a torque between the first shaft (19a) and the second shaft (19b).

2. Magnetic gear torque transmission mechanism (19) according to claim 1, wherein that of the first shaft (19a) and of the second shaft (19b) which is configured to generate a second magnetic field, is further configured to present at least two pairs of magnetic poles following excitation by the magnetic excitation device (51).

3. Magnetic gear torque transmission mechanism (19) according to any one of claims 1 and 2, wherein a plurality of shoulders (191a) project out of that of the first shaft (19a) and the second shaft (19b) which is configured to generate a second magnetic field, the plurality of shoulders (191a) forming pairs of magnetic poles following excitation by the magnetic excitation device (51).

4. Magnetic gear torque transmission mechanism (19) according to any one of claims 1 to 3, wherein the magnetic generation device (50) includes a permanent magnet.

5. Magnetic gear torque transmission mechanism (19) according to any one of claims 1 to 4, wherein the magnetic excitation device (51) comprises a first electromagnet.

6. Magnetic gear torque transmission mechanism (19) according to claim 5, wherein the magnetic generation device (50) comprises a second electromagnet.

7. Magnetic gear torque transmission mechanism (19) according to claim 6, wherein at least one of the first and second electromagnets is configured to control the torque transmitted between the first shaft (19a) and the second shaft (19b) as a function of a supply current to at least one of the first and second electromagnets.

8. Magnetic gear torque transmission mechanism (19) according to any one of claims 1 to 5, wherein: the magnetic generation device (50) comprises a first plurality of permanent magnets fixed to the internal surface (190c) of the stator (19c) and aligned in a first plane, and a second plurality of permanent magnets fixed to the internal surface of the stator and aligned in a second plane axially offset from the first plane; and the magnetic excitation device (51) comprises an electromagnet fixed to the internal surface of the stator (19c) and positioned axially between the first plane and the second plane.

9. Aeronautical propulsion system (1) comprising: a drive shaft (11); a fan shaft (20); and a magnetic gear torque transmission mechanism (19) according to any one of claims 1 to 8, wherein the drive shaft (11) is connected to one of the first shaft (19a) and the second shaft (19b) and the fan shaft (20) is connected to the other of the first shaft (19a) and the second shaft (19b).

10. Aircraft (100) comprising an airframe and an aeronautical propulsion system according to claim 9, wherein the aeronautical propulsion system (1) is fixed to the airframe.

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