REDUCTION GEAR WITH AN ELECTRIC MACHINE

Description

Scope of the invention

[0001] The present invention relates to the field of speed reducers, particularly for aircraft turbomachinery. It specifically concerns a speed reducer equipped with an electric machine and a turbomachine comprising such a speed reducer. Technical background

[0002] Prior art includes documents US-A1-2019 / 085714, which forms the basis of the two-part form, WO-A1-2019 / 243558 and US-A-4291233.

[0003] An aircraft turbomachine, such as a turbofan, generally comprises a shrouded fan located at the turbomachine's inlet and driven by a low-pressure shaft. A reduction gear can be interposed between the fan and the low-pressure shaft so that the fan rotates at a lower speed than the shaft. Reducing the speed also allows for an increase in the fan size, thus enabling very high bypass ratios.In addition to aircraft propulsion, the turbomachine ensures the production of electrical current typically using a permanent magnet alternator (generally called PMA meaning "Permanent Magnet Alternator") and an accessory gearbox known by the English acronym AGB (for Accessory Gear Box) to power various equipment enabling, for example, aircraft cabin lighting or the aircraft cabin air conditioning and pressurization system.

[0004] It is known to equip the turbomachine, and in particular the accessory gearbox, of an electric machine. An electric machine is an electromechanical device based on electromagnetism that converts electrical energy, for example, into mechanical energy (generator mode) or, reversibly, produces electricity from mechanical energy (motor mode). The electric machine can also operate in generator mode as well as in motor mode.

[0005] Faced with the environmental challenges in the aeronautical sector and the increasing electrical power requirements that accompany the growing number of aircraft components and new functions, the question of turbomachine hybridization arises. The electric machine as described above does not provide a significant increase in electrical power for all aircraft functions, and the efficiency of converting mechanical power into electrical power is not optimal. Furthermore, integrating the electric machine into various areas of the turbomachine proves complex and is constrained by size, the temperature resistance of certain electric machine components, accessibility, the performance of the turbomachine itself, and other factors. Summary of the invention

[0006] The objective of the present invention is to provide an ease of integration of an electrical machine intended to provide additional electrical power in a turbomachine without significantly modifying the components of the turbomachine.

[0007] We achieve this objective in accordance with the invention by means of an epicyclic gear reducer for an aircraft turbomachine, the reducer is defined by claim 1.

[0008] Thus, this solution achieves the aforementioned objective. In particular, this configuration avoids cluttering the turbomachine since the electric machine is integrated into the gearbox, and it also allows the gearbox's design (fixed ring gear and movable planet carrier) to control the position of the rotor and stator to achieve an acceptable air gap. Furthermore, integrating the electric machine into the gearbox provides a modular approach because the gearbox and electric machine components can be assembled independently of each other and also independently of other turbomachine components. Assembly and disassembly are also simplified because the electric machine and gearbox are located in the same place.

[0009] The reducer also includes one or more of the following features, as defined by the claims: The stator of the electric machine extends around the rotor. The stator comprises a first annular piece centered on the longitudinal axis and extending the ring gear downstream along the longitudinal axis. In particular, the rotor and stator downstream of the speed reducer are more accessible compared to those of the prior art, which are located within the speed reducer, requiring the electric machine to be mounted simultaneously with each component of the speed reducer. The first annular piece is either attached to the ring gear or is integral with the ring gear. The rotor comprises a second annular piece mounted on a cage of the planet carrier. The planet carrier comprises an annular cage supporting a plain bearing on which the planet gear is mounted.

[0010] The invention also relates to an aircraft turbomachine comprising a drive shaft with longitudinal axis X and a fan having a fan shaft driven in rotation by the drive shaft via a reduction gear having any of the above characteristics, the ring being fixed to a stator housing of the turbomachine and the planet carrier being coupled to the fan shaft to drive it in rotation around the longitudinal axis.

[0011] The turbomachine also includes one or more of the following features, as defined by the claims: The solar element is coupled to the drive shaft, which rotates it around the longitudinal axis. The lubrication chamber is delimited, at least partially, by a ferrule forming, at least partially, a radially internal wall of the primary flow and the blower shaft. The gearbox and the electric machine are arranged within a lubrication chamber located upstream of an internal casing.

[0012] The invention also relates to a modular assembly method for a turbomachine as described above, the method comprising the following steps: assemble the speed reducer as described above, integrate the electric machine into the speed reducer by mounting the rotor on the planet carrier and the stator on the ring gear, and mount the assembly including the speed reducer and the integrated electric machine in the turbomachine lubrication chamber. Brief description of the figures

[0013] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent upon reading the detailed explanatory description that follows, of embodiments of the invention given by way of purely illustrative and non-limiting examples, with reference to the accompanying schematic drawings in which: [ Fig.1 ] there figure 1 is a schematic and axial cross-sectional view of a double-flow turbomachine with a gearbox according to the invention; [ Fig. 2 ] there figure 2 is a schematic, axial cross-sectional and detailed view of a fan module of the double-flow turbomachine with a reduction gear interposed between a fan shaft and a drive shaft of the turbomachine according to the invention; Fig.3 ] there figure 3 is a perspective view, in axial half-section and upstream of a reducer according to the invention; and [ Fig. 4 ] there figure 4is a perspective view in axial half-section downstream of a reducer according to the invention. Detailed description of the invention

[0014] There figure 1 Figure 1 shows an axial cross-sectional view of a turbomachine 1 with longitudinal axis X to which the invention applies. The turbomachine shown is a twin-spool, twin-flow turbomachine intended for mounting on an aircraft according to the invention. Of course, the invention is not limited to this type of turbomachine.

[0015] In this application, the terms "upstream", "downstream", "axial" and "axially" are defined with respect to the direction of gas flow in the turbomachine and also along the longitudinal axis (and even from left to right on the figure 1 ). The terms "radial", "radially", "internal" and "external" are also defined with respect to a radial axis Z that is perpendicular to the X axis of the turbomachine.

[0016] This twin-flow, twin-body turbomachine 1 includes a fan 2 which is mounted upstream of a gas generator 3. The fan 2 includes a plurality of fan blades 4 which extend radially from the periphery of a disk 5 (cf. figure 2 ) crossed by a blower shaft 6. The blower 2 is surrounded by a blower housing 7 which at least partially supports a nacelle 8. The latter extends around the gas generator 3 and along the longitudinal axis X.

[0017] The gas generator 3 comprises, from upstream to downstream, a low-pressure compressor 9, a high-pressure compressor 10, a combustion chamber 11, a high-pressure turbine 12, and a low-pressure turbine 13. The high-pressure (HP) compressor 10 is connected to the HP turbine via an HP shaft to form the first section, referred to as the high-pressure section. The low-pressure (LP) compressor 9 is connected to the LP turbine via an LP shaft 14 to form the second section, referred to as the low-pressure section. The HP shaft extends inside the LP shaft 14.

[0018] An airflow F entering the turbomachine via the fan 2 is split by a separation nozzle 15 of the turbomachine into a primary airflow F1, which passes through the gas generator 3 and specifically into a primary duct 16, and a secondary airflow F2, which circulates around the gas generator 3 in a secondary duct. The primary duct 16 and the secondary duct 17 are coaxial. The secondary airflow F2 is ejected by a secondary nozzle 18 terminating the nacelle 8, while the primary airflow F1 is ejected outside the turbomachine via an ejection nozzle 19 located downstream of the gas generator. The primary and secondary airflows rejoin at the outlet of their respective nozzles.

[0019] With reference to the figure 2The blower shaft 6 is connected to a drive shaft that rotates it around its longitudinal axis via a power transmission mechanism 20. In this example, the drive shaft is the low-pressure shaft 14. The power transmission mechanism 20 reduces the speed of the blower 2 to a speed lower than that of the low-pressure shaft 14. Furthermore, the power transmission mechanism 20 allows for the arrangement of a blower with a large diameter to increase the dilution ratio. The blower dilution ratio is advantageously greater than 10. Preferably, the dilution ratio is between 12 and 18.

[0020] The power transmission mechanism includes a gearbox 21, which is in this case an epicyclic gear reducer. This gearbox is housed in a lubrication chamber 22 located upstream of the gas generator. The lubrication chamber lubricates the gearbox 21 as well as the rotating guide bearings. Specifically, the lubrication chamber 22 is arranged within an annular inner casing 23, which extends upstream into an aerodynamically shaped inlet cone 24.

[0021] The inner casing 23 includes an annular rotor ferrule 23a which rotates about the longitudinal axis X relative to an annular stator ferrule 23b of the inner casing 23. The disc 5 of the blower 2 is mounted in the ferrule 23a. The stator shell 23b is structurally connected to an inlet housing 27 by first stator vanes 25 (known by the acronym "IGV") which extend radially in the primary airflow F1 and around the longitudinal axis X. The inlet housing 27 carries the separation nozzle 15 upstream and the inlet housing 27 is extended downstream by an inter-vein housing 29. Of course, the rotor shell 23a, the disc 5 form a rotor assembly while the inlet housing 27, the stator vane 25 and the stator shell 23b form a stator assembly.Second stator vanes 26 (known by the acronym "OGV") structurally connect the inlet housing 27 to the blower housing 7 which are heard radially in the secondary airflow and around the longitudinal axis X. Advantageously, the lubricant which occupies the lubrication chamber 22 is oil in the form of a mist.

[0022] The epicyclic gear reducer 21 typically comprises a sun gear 30 (or inner planet gear), at least one satellite gear 31, a planet carrier 32, and a ring gear (outer planet gear) 33. In this example, the reducer includes several satellite gears, for example, three. The sun gear 30 is centered on the longitudinal axis X and is rotationally coupled to the drive shaft (here, the BP shaft) along the longitudinal axis X via a sun gear shaft 34. The latter comprises first elements designed to cooperate with complementary second coupling elements carried by the sun gear. The satellite gears 31 are carried by the planet carrier 32. Each satellite gear 31 meshes with external teeth of the sun gear 30 and internal teeth of the ring gear 33. Each satellite gear 31 is guided in rotation about a satellite axis A, which is parallel to the longitudinal axis X. The satellite axes A are fixed to the planet carrier 32.The corona 33 surrounds the solar 30 and is centered on the longitudinal axis X.

[0023] The planet carrier 32 is rotationally coupled to the fan shaft 6, and the ring gear 33 is fixed to a stator housing of the turbomachine. In other words, the ring gear 33 is rotationally fixed. Thus, the solar shaft 30 forms the input of the speed reducer, while the planet carrier 32 forms the output of the speed reducer. The fan shaft 6, the solar shaft 34, and the drive shaft (BP shaft 14) rotate about the longitudinal axis and are coaxial. In this embodiment, the planet carrier 32 and the fan shaft 6 are monoblocs. That is, they are formed as a single unit. The fan shaft 6 is guided in rotation relative to a fixed structure of the turbomachine by means of at least one bearing 35. This bearing is advantageously a ball bearing.The bearing comprises, in particular, an inner ring 36 mounted on the blower shaft 6, an outer ring 37 carried by an annular support 38, and a ball bearing 39 between the inner and outer rings. The annular support 38 is fixed to the stationary structure of the turbomachine.

[0024] On the figures 3 and 4The crown gear 33 is formed of a first part 33a and a second part 33b, which are coaxial. Each first and second part 33a, 33b comprises portions of the crown gear teeth. Each first and second crown gear part includes at one end an annular flange 40a, 40b extending outwards along the radial axis. The annular flanges are fastened to each other by fasteners 41 such as screws, bolts, nuts, or similar elements. The flanges 40a, 40b are located at a median plane perpendicular to the longitudinal axis. The crown gear 33 is also fixed to a crown carrier 42, which is attached to the annular support 38 of the bearing 35 by fasteners as described above. A closing cover 43 of the enclosure 22 covers the crown 33 radially and a portion of the crown carrier 42.

[0025] In this embodiment, the turbomachine further includes an electric machine 50 to provide additional electrical power. The electric machine 50 operates as both a generator and a motor. In the latter case, the electric machine provides propulsion in addition to the blower and fossil fuel. In generator mode, the electric machine supplies additional electrical power, for example, of at least one hundred kilowatts.

[0026] The electric machine comprises a rotor 51 and a stator 52. As we can see on the figures 3 and 4The electric machine is arranged within the lubrication chamber 22 (in the gas generator) so that it can also be cooled by the lubricant. The temperature within the lubrication chamber is at most around 150°C, which is perfectly acceptable for the electric machine. Indeed, the temperature of the electric machine's components (electrical conductors, electrical insulators, magnetic circuits, temperature sensors, exciters) generally should not exceed this value. Furthermore, the machine generates significant power, which is directly dissipated into the lubricating oil.

[0027] The enclosure 22 is delimited at least in part by the ferrule 23b, 28 forming at least in part a radially internal wall of the primary vein, the blower shaft 6 and the support 38 of the bearing 35. Air circulates outside the enclosure 22 as for example between the support 38 and the internal casing 23 and inter-vein casing 27 assembly.

[0028] The electric machine is integrated here into the speed reducer 21, which facilitates integration into the gas generator and in particular into the lubrication chamber 22. For this purpose, the rotor 51 is mounted on the planet carrier 32 so as to drive in rotation around the longitudinal axis and the stator 52 is mounted on the ring 33.

[0029] The stator 52 comprises a first annular part 53 around the longitudinal axis and is integral with the ring 33. The first annular part 53 extends downstream of the annular ring 33 along the longitudinal axis X. The first annular part 53 is an added part (i.e., separate and / or manufactured using a different process) on the ring. The stator 52 (first annular part) can be fixed by gluing, screwing (screws / bolts / nuts), etc., to the ring 33. Alternatively, the annular part 53 is formed from a single piece of material with the ring. The stator 52 extends around the rotor 51. The first annular part 53 is advantageously supported by the second part 33b of the ring (the one located downstream of the speed reducer), as can be seen in the figures 3 and 4 .

[0030] As for the rotor 51, it also includes a second annular part 55 around the longitudinal axis X. The rotor 51 can be fixed by gluing, screwing (screws / bolts / nuts), etc., to the planet carrier. The first part 53 and the second part 55 are concentric. We understand that the second part 55 also extends downstream of the speed reducer. The first annular part 53 has a length I1 significantly less than that I2 of the second part 55. To mount the rotor 51 on the planet carrier, the latter includes an annular cage 58 centered on the longitudinal axis. The first flank 59 is mounted upstream of the speed reducer, while the second flank 60 is mounted downstream of the speed reducer. Each first and second flank includes axial ports 61 (cf. figure 3) passing through their walls on either side along an axis parallel to the longitudinal axis X. Each satellite is mounted to rotate freely about a satellite axis on a bearing 62. Each bearing is preferably, but not exclusively, a plain bearing. Each bearing has its axis coaxial with the satellite axis, and its free ends 62a, 62b are mounted respectively at a corresponding opening in the first and second flanks 59, 60. An oil film circulates between the external surface 63 of each bearing and the internal surface 64 of each satellite. This oil film is continuously supplied by a lubrication circuit 69 in order to improve the performance of the speed reducer and extend the service life of the plain bearings.

[0031] As we can see on the figures 3 and 4Also, the second annular part 55 is mounted on the periphery of the second flange 60. The second flange 60 has, for this purpose, an annular collar 65 extending outwards along the radial axis. The collar 65 is housed in a notch 66 of the second annular part 55. The notch 66 is arranged in a radially internal surface 67 of the first annular part 53 and oriented towards the longitudinal axis. The second annular part 55 also has a radially external surface 68 (opposite to the radially internal surface along the radial axis) which carries permanent magnets. The permanent magnets are arranged opposite a winding carried by the first annular part 53. Conversely, the second annular part may contain the winding, and the first annular part may contain the permanent magnets.

[0032] With reference to the figure 4An electrical harness 70 extends radially outside the ring gear 33 and runs out of the gearbox. In particular, the electric machine 50 includes at least one electrical cable 71 that connects the electric stator to an electronic control system (such as the FADEC or a full authority control system) to provide power to the electric machine. Advantageously, other electrical cables of the electric machine 50 are bundled into this single harness 70. The electrical harness 70 runs out of the enclosure via a housing arm or stator vane. The fact that the ring gear 33 of the planetary gear reducer is fixed facilitates, in particular, the routing of this electrical harness out of the enclosure to external components of the turbomachine.

[0033] When the electric machine 50 operates in motor mode, it adds torque to the output of the gearbox 21 in order to provide more power, for example, to the fan. One or more batteries can be installed in the aircraft, and electrical energy is supplied to the electric machine 50 via the electrical cable 71. This energy rotates the rotor 51 of the electric machine 50. The electrical energy is thus converted into mechanical energy. An additional energy input is provided to assist in the rotation of the fan 2 via the fan shaft 6.

[0034] When the electric machine is in generator mode, the electric machine 50 draws torque from the gearbox 21 to provide additional electrical power. The torque is transmitted via the low-pressure shaft 14 to the gearbox 21 and is then transmitted to the fan shaft 6 and to the electric machine 50. The latter converts mechanical energy into electrical energy to power electrical equipment such as batteries mounted on the aircraft, aircraft equipment, or electric motors mounted on the aircraft (non-exhaustive list).

[0035] As we have seen, integrating the electric machine 50 onto the speed reducer 21 allows for the modularization of the entire reducer and electric machine assembly. To this end, during assembly, the speed reducer 21 is first assembled with its various components. Then, the electric machine 50, with its rotor and stator, is mounted on the speed reducer with the stator on the ring gear 33 and the rotor on the planet carrier 32. The stator and rotor extend downstream of the speed reducer, and specifically downstream of the ring gear and the planet carrier. This arrangement facilitates the mounting and dismounting of the electric machine on the speed reducer. If the stator is a single unit with the ring gear, the stator is mounted on the reducer at the same time as the ring gear. The electrical cable 71 is connected to the electric machine 50.Finally, the gearbox and the electric motor are installed in the lubrication chamber 22 as a single unit, thus allowing for easy modularity of the assembly. This assembly is slid from upstream to downstream so that the solar shaft 34 is coupled with the drive shaft (LP shaft). The disc 5 and the blower shaft 6 are then inserted from the upstream side of the inner housing to couple the blower shaft 6 to the satellite carrier 32. The inlet cone 24 is then mounted onto the inner housing to close the blower module.

Claims

1. A reducer (21) with epicyclic gear train for an aircraft turbomachine (1), the reducer (21) comprising a sun gear (30) and a ring gear (33) which are centred on a longitudinal axis X and a planet carrier (32) which carries at least one planet gear (31) mounted so as to be able to rotate about a planet gear axis A parallel to the longitudinal axis X, the sun gear (30) being able to rotate about the longitudinal axis, the planet gear (31) meshing with both the sun gear (30) and the ring gear (33), the reducer (21) comprises an electric machine (50) integrated therewith, the reducer being characterised in that the planet carrier (32) is movable about the longitudinal axis and the ring gear (33) is stationary in rotation the reducer, and in that the electric machine comprises a rotor (51) mounted on the planet carrier (32) so as to be driven in rotation about the longitudinal axis X and a stator (52) mounted on the ring gear (33), an in that an electric harness (70) extends outside the ring gear (33) and at least one electric cable (71) connected to the stator (52) of the electric machine (50) circulates inside the electric harness (70).

2. The reducer (21) according to the preceding claim, characterised in that the stator (52) of the electric machine (50) extends around the rotor (51) of the electric machine.

3. The reducer (21) according to any of the preceding claims, characterised in that the stator (52) comprises a first annular part (53) centred on the longitudinal axis and extending the ring gear (33) downstream along the longitudinal axis.

4. The reducer (21) according to the preceding claim, characterised in that the first annular part (53) is fitted on the ring gear (33) or formed as an integral part of the ring gear (33).

5. The reducer (21) according to the preceding claim, characterised in that the rotor comprises a second annular part (55) mounted on a cage (58) of the planet carrier (32).

6. The reducer (21) according to any of the preceding claims, characterised in that the planet carrier (32) comprises an annular cage (58) carrying a plain bearing (62) on which the planet gear is mounted.

7. An aircraft turbomachine (1) comprising a drive shaft (14) of longitudinal axis X and a fan (2) having a fan shaft (6) driven in rotation by the drive shaft via a reducer (21) according to any of the preceding claims, the ring gear (33) being attached to a stator casing of the turbomachine and the planet carrier (32) being coupled to the fan shaft (6) in order to drive it in rotation about the longitudinal axis.

8. The turbomachine according to the preceding claim, characterised in that the reducer (21) and the electric machine (50) are arranged in a lubrication enclosure (22) arranged upstream of an internal casing.

9. The turbomachine according to any one of claims 7 and 8, characterised in that the sun gear is coupled to the drive shaft (14) for driving it in rotation about the longitudinal axis.

10. A method of modular assembly for a turbomachine (10) according to the preceding claim, characterised in that it comprises the following steps: - assembling the speed reducer (21) according to any of claims 1 to 6, - integrating the electric machine (50) with the speed reducer (50) by mounting the rotor (51) on the planet carrier and the stator (52) on the ring gear (33), and - mounting the speed reducer and integrated electric machine (50) assembly in the lubrication enclosure (22) of the turbomachine.