TURBOMACHINE EQUIPPED WITH AN ELECTRIC MACHINE ARRANGED IN ITS DEDICATED ENCLOSURE AND A DEDICATED ENCLOSURE LUBRICATION SYSTEM

Abstract

The invention relates to a turbomachine (1), for an aircraft, comprising: - a low-pressure shaft (2) extending along a longitudinal axis to a rear end (3), - a turbomachine stator (4) supporting the rear end (3) by a rear bearing (5) arranged in a first enclosure (7), and - an electrical machine (15), located at the rear of the turbomachine, comprising a stator (24) and a rotor (25) capable of being driven in rotation in a disconnectable manner by the low-pressure shaft (2) by means of a connection device (30). According to the invention, the electrical machine is contained in a second dedicated lubrication enclosure (19) separate from the first enclosure and in that the rotor of the electrical machine is supported by at least one rotation bearing which is arranged in the second enclosure, a lubrication system (60), of the rotation bearing (40), being contained in the second enclosure. Figure for the abstract: Fig.2

Description

Title of the invention: TURBOMACHINE EQUIPPED WITH AN ELECTRIC MACHINE ARRANGED IN ITS DEDICATED ENCLOSURE AND WITH A LUBRICATION SYSTEM FOR THE DEDICATED ENCLOSURE Technical field of the invention

[0001] The present invention relates to the field of turbomachines, and in particular aircraft. It relates in particular to a turbomachine equipped with an electric machine which is arranged at the rear of the turbomachine. Technological background

[0002] Faced with the environmental challenge in the aeronautical field and the increasing need for electrical power concomitantly with the number of equipment and new functions of the aircraft, the question of the hybridization of the turbomachine arises. The electric machine which equips the accessory boxes known by the English acronym AGB (for Accessory Gear Box) does not allow a significant gain in electrical power to be provided for all the functions of the aircraft and the efficiency of the conversion of mechanical power into electrical power is not at its optimum.

[0003] An electric machine is an electromechanical device based on electromagnetism allowing the conversion of electrical energy, for example, into mechanical energy (generator mode) or reversibly, allowing the production of electricity from mechanical energy (motor mode). The electric machine can also behave in generator mode as well as in motor mode.

[0004] It is known to integrate the electric machine at the rear of the turbomachine where there is space for its integration and where high temperature constraints and other layout difficulties apply. An example of an electric machine placed at the rear of the turbomachine is described in document FR-A1-3124541. In this example, the electric machine 01 comprises a rotor 02 which is rotationally coupled with the low pressure shaft 03 which extends furthest to the rear of the turbomachine. However, the rotor 02 of the electric machine 01 is not mounted directly on a rear end 04 of the low pressure shaft so as not to weigh down the low pressure shaft 03 and also because of the increasingly reduced size of the shafts of the turbomachine. The low pressure shaft 03 is guided by a rear bearing 05 arranged at its rear end 04.

[0005] The electrical machine 01 is mounted independently of the rest of the turbomachine so as to facilitate its maintenance using a connection device 06. The latter is configured so as to connect or disconnect in rotation the rotor of the electrical machine from the low pressure shaft 03 for example in the event of damage.

[0006] The connection device 06 comprises a shaft section 07 fixed in a separable manner from the rear end 04 of the low pressure shaft 03 and carrying rotation bearings 08 supporting the electric machine 01. The rotation bearings 08 allow the rotation of the rotor of the electric machine 01 relative to the stator 09 of the electric machine and independently of the rotation of the low pressure shaft 03 when the latter is disconnected from the low pressure shaft. The rotation bearings 08 supporting the electric machine and the rear bearing 05 are housed in the same lubricated enclosure. Several nozzles open into the same enclosure to lubricate the bearings of the low pressure shaft and of the electric machine.

[0007] However, such a configuration involves the complete disassembly of the entire electrical machine and the low-pressure shaft in the event of maintenance. A failure of one of the components of the electrical machine or another element such as a seal in the enclosure could have a significant impact such as stopping the turbomachine.

[0008] There is a need to resolve all or part of the aforementioned drawbacks. Summary of the invention

[0009] The objective of the present invention is to provide a solution making it possible to make the electric machine independent and autonomous in terms of arrangement, lubrication and modularity in a simple, economical and robust manner.

[0010] We achieve this objective in accordance with the invention by means of a turbomachine, in particular for aircraft, comprising: - a low pressure shaft extending along a longitudinal axis to a rear end, - a turbomachine stator supporting the rear end of the low pressure shaft by a rear bearing which is arranged in a first lubrication enclosure, and - an electric machine, located at the rear of the turbomachine, comprising an electric machine stator fixed to the stator of the turbomachine and an electric machine rotor capable of being driven in rotation in a disconnectable manner by the low pressure shaft using a connection device, the electric machine being contained in a second dedicated lubrication enclosure which is separate from the first lubrication enclosure and in that the electric machine rotor is supported by at least one rotation bearing which is arranged in the second enclosure, the turbomachine comprising a lubrication system, less one rotation bearing, which is contained in the second enclosure.

[0011] Thus, this solution makes it possible to achieve the aforementioned objective. In particular, this configuration makes it possible to isolate the electrical machine from the enclosure of the turbomachine and to be able to lubricate its components, in particular its rotation bearing, independently of the other components of the turbomachine. The service life and performance of the rotation bearing are improved. Furthermore, this makes it possible to create a modularity of the electrical machine which facilitates its assembly and disassembly in relation to the rest of the turbomachine, in particular in the event of maintenance or even failure. In this way, the bearing of the electrical machine is lubricated and cooled by the lubrication system which is independent of the lubrication of the enclosure where the rear bearing of the low-pressure shaft is located.Failure of an element within the enclosure of the electric machine, for example a seal, is controlled because it is contained within the enclosure of the electric machine and it is possible to shut down the electric machine without hindering the operation of the turbomachine. In addition, such a configuration requires very few structural modifications to the turbomachine.

[0012] The turbomachine also comprises one or more of the following features and / or steps, taken alone or in combination:

[0013] - the lubrication system comprises a lubrication circuit of at least the bearing rotation and a feed pump allowing the circulation of lubrication in the lubrication circuit, the feed pump being driven in rotation by the low pressure shaft or the rotor of the electric machine.

[0014] - the lubrication system comprises a reservoir arranged radially outside of the electric machine and located on an angular sector approximately at 6 o'clock with reference to the dial of a clock, the reservoir being in fluid communication with the feed pump.

[0015] - the electrical machine comprises a heat exchanger configured to cool the lubricant of the lubrication system and the electrical machine.

[0016] - the heat exchanger is arranged in a housing surrounding the stator of the machine electric.

[0017] - the turbomachine comprises a connecting shaft which is coupled to the rear end and which extends the low pressure shaft rearwardly along the longitudinal axis and in that the electric machine rotor is connected to a drive shaft which carries at least one rotation bearing, the connection device being configured so as to secure or detach in rotation the drive shaft from the connecting shaft.

[0018] - the second enclosure is delimited at least in part by the connecting shaft, a stator armature which is connected to the electric machine stator and the electric machine rotor, sealing elements being arranged on the one hand between the armature of stator and the connecting shaft, and on the other hand between members of the stator armature separating the electric machine rotor from the electric machine stator.

[0019] - the connection device comprises first dog teeth which are connected to the drive shaft and which are intended to mesh or disengage with second dog teeth connected to the connecting shaft.

[0020] - the connecting device comprises a carriage which cooperates with the shaft drive and which carries the first dog teeth, the carriage being controlled in movement along the longitudinal axis relative to the drive shaft between a coupling position and a decoupling position by an actuator.

[0021] - sealing gaskets are arranged on either side of the connection device.

[0022] The invention relates to an aircraft comprising at least one turbomachine having any one of the aforementioned characteristics. Brief description of the figures

[0023] The invention will be better understood, and other aims, details, characteristics and advantages thereof will appear more clearly on reading the detailed explanatory description which follows, of embodiments of the invention given as purely illustrative and non-limiting examples, with reference to the appended schematic drawings in which:

[0024] - [Fig.l] represents a turbomachine according to the prior art;

[0025] - [Fig.2] is a schematic and partial axial sectional view of an example of turbomachine to which the invention applies;

[0026] - [Fig.3] is an example of the embodiment of a connecting shaft connected at one end rear of a low pressure shaft of the turbomachine according to the invention;

[0027] - [Fig.4] illustrates in a partial axial sectional view an example of sealing elements insulating a dedicated enclosure of an electrical machine according to the invention;

[0028] - [Fig.5] illustrates in a partial axial sectional view another example of sealing elements insulating a dedicated enclosure of an electrical machine according to the invention;

[0029] - [Fig.6] is a partial axial sectional view of a lubrication system of organs of the electric machine according to the invention. Detailed description of the invention

[0030] [Fig.l] has already been described previously.

[0031] [Fig. 2] schematically and partially represents a turbomachine 1 with longitudinal axis X to which the invention applies. The turbomachine 1 is intended to be mounted on an aircraft. In particular, the turbomachine may be a turbojet, a turboprop, a turboshaft or generally a turbomachine which includes a fan or propeller that is either shrouded or unshrouded. Only the rearmost or downstream part of the turbomachine along the longitudinal axis X is shown.

[0032] In the present invention, and generally, the terms "upstream" and "downstream" are defined with respect to the circulation of gases or air flows in the turbomachine and here along the longitudinal axis X. The terms "axial" and "axially" are defined with respect to the longitudinal axis X. The terms "external", "external", "internal", "internal" and "radial" are defined with respect to a radial axis Z which extends from the longitudinal axis X and with respect to the distance from the longitudinal axis X. The radial axis Z is perpendicular to the longitudinal axis X.

[0033] The turbomachine 1 comprises a low-pressure shaft 2 which extends along the longitudinal axis X and up to a rear end 3. Advantageously, the low-pressure shaft 2 is coupled to a rotor of a turbine (not shown) of the turbomachine. In particular, the turbine considered, but not limited to, is the low-pressure turbine. The rotor of the low-pressure turbine is generally connected via the low-pressure shaft 2 to a rotor of a low-pressure compressor (not shown) which is located further upstream in the turbomachine along the longitudinal axis X.

[0034] The low pressure shaft 2 is supported by a stator 4 of the turbomachine using several bearings. More specifically, the turbomachine 1 comprises a rear bearing 5 allowing the stator 4 to support the rear end of the low pressure shaft 2. Optionally, the rear bearing 5 comprises an inner ring 5a secured to the rear end 5 of the low pressure shaft 2 and an outer ring 5b secured to a cylindrical bearing surface 6a of the stator 4 of the turbomachine. The cylindrical bearing surface 6a is for example secured to a bearing support 6. Rolling members 5c, for example rollers, are arranged between the inner and outer rings 5a, 5b.

[0035] Advantageously, the rear bearing 5 is arranged in a first lubrication enclosure 7. This first lubrication enclosure 7 is closed by means of seals 8. In particular, a first seal 8a is arranged between a first shell 9 of the stator 4 and a cylindrical bearing surface 10 of the low-pressure shaft 2 and a second seal 8b is placed between a second shell 11 connected to the stator and a journal 12 secured to the rear end 3 of the low-pressure shaft 2. The bearing support 6 further comprises a shell 6b which is fixed by means of fixing members to the second shell 11. In other words, the first lubrication enclosure 7 is delimited at least by the rear end 3 of the low-pressure shaft 2, the first shell 9, the second shell 11 of the stator 4 as well as the first and second seals 8a, 8b.

[0036] Advantageously, the first enclosure 7 is supplied by a lubrication circuit which is supplied by a power source (not shown). The circuit lubrication comprises a nozzle 13 which is shown schematically in [Fig.l]. The nozzle 13 is aimed, for example, at the rear bearing 5. This can be connected to a conduit which passes through a radial arm 14a of an exhaust casing 14. The lubricant is preferably oil (in the form of a mist) which makes it possible to lubricate and cool the bearings 5 ​​guiding the rotation of the low pressure shaft 2 and which produce heat.

[0037] The turbomachine 1 comprises an electrical machine 15 which is located at the rear of the turbomachine. The electrical machine 15 is advantageously housed in a cavity 16 which is formed downstream of the rear end 3 of the low-pressure shaft. In other words, the electrical machine 15 is arranged downstream of the rear end 3 of the low-pressure shaft. The cavity 16 is closed at least in part by a cover 17 which is fixed to the stator 4, and in particular to the exhaust casing 14 of the turbomachine, by a bolted connection for example. A thermal protection 18 can be applied to the internal wall of the cover 17 to protect the latter from the heat produced by the exhaust gases at the outlet of the low-pressure turbine (not shown) of the turbomachine.

[0038] The electric machine 15 is arranged more precisely in a second lubrication enclosure 19 which is dedicated for the electric machine 15 and which is distinct from the first lubrication enclosure 7. The second enclosure 19 is contained for example in the cavity 16. The second enclosure 19 is delimited at least in part by a stator armature 20, a support shaft (described later) 21, a casing 22 and a rotor 25 of the electric machine 15 described later. The casing 22 is fixed to the stator armature 20 by means of fixing members (not shown).

[0039] The electrical machine 15 comprises a stator 24 and a rotor 25. The electrical machine 15 can, for example, operate alternately in generator mode and in motor mode. That is to say, the electrical machine 15 can take power from the low-pressure shaft 2 or inject power onto the low-pressure shaft 2.

[0040] Advantageously, but not limited to, the electric machine stator 24 comprises electrical windings (not shown) and the electric machine rotor 25 comprises permanent magnets (not shown). In the present example, the electric machine stator 24 surrounds the electric machine rotor 15 and is fixed to the stator 4 of the turbomachine.

[0041] Advantageously, but not limitatively, the electric machine stator 24 comprises the stator armature 20 which comprises a first arm 20a and a second arm 20b which are located on either side of the electric machine stator 24 along the longitudinal axis X. The electric machine 15 may comprise a housing 26 which radially surrounds the stator 24 and the rotor 25. In the present example, the first arm 20a is fixed upstream of the housing 26 and the second arm 20b is fixed downstream of the housing 26. The first and second arms 20a, 20b extend radially towards the longitudinal axis X. The electric machine rotor 25 and the electric machine stator 24 are contained axially, advantageously, but not limited to, between the first and second arms 20a, 20b.

[0042] In [Fig. 2], a first flange 27 makes it possible to fix the stator 24 of the electrical machine 15 to a second flange 28 of the stator 4. The first flange 27 extends advantageously, but not limited to, from the stator armature 20 and radially outwards. The second flange 28 is here carried by one of the first and second shells 9, 11 of the stator 4 of the turbomachine 1 and extends radially outwards. This makes it possible to free up space in the enclosures of the turbomachine. The fixing of the first and second flanges 27, 28 is carried out by a bolt-type fixing member 29. Other similar fixing members 29 allowing easy detachment of the first and second flanges 27, 28 are conceivable. Advantageously, the fixing member comprises a threaded rod whose axis extends parallel to the longitudinal axis X. The fixing is axial here.

[0043] The rotor 25 of the electric machine 15 is advantageously driven by the low-pressure shaft 2 in a disconnectable manner. This is made possible by a connection device 30 which is configured so as to couple or uncouple in rotation the rotor 25 of the electric machine 15 from the low-pressure shaft 2. Preferably, the coupling is carried out when the turbomachine is stopped. The uncoupling can take place in the event of damage to the electric machine 15 which would require the rotor 25 of the electric machine 15 to no longer be driven by the low-pressure shaft.

[0044] For this purpose and as shown in [Fig. 3], the turbomachine 1 comprises a connecting shaft 21 which extends along the longitudinal axis X. The connecting shaft 21 extends in this example downstream of the rear end 3 of the low pressure shaft 2 and extends the low pressure shaft 2 towards the rear of the turbomachine 1. The connecting shaft 21 is advantageously, but not limited to, coaxial with the low pressure shaft 2. The connecting shaft 21 is fixed to the rear end 3 of the low pressure shaft in a removable manner so as to facilitate disassembly in a modular manner. In particular, the connecting shaft 21 may comprise a third fixing flange 31 which is fixed to a fourth fixing flange 32 of the rear end 3. The third fixing flange 31 extends radially from an upstream end 21a of the connecting shaft 21 so as to facilitate assembly and disassembly.The fixing is carried out here by a bolt-type fixing member 33 so as to separate or secure the connecting shaft 21 even more easily. The axis of the threaded rod of this bolted connection is here parallel to the longitudinal axis X. In this way, it is possible to extract the electric machine 15 by removing the fixing members 29 and 33 at the level of the respective flanges in order to carry out maintenance on it. The turbomachine 1 can continue. to operate without the electric machine 15.

[0045] Alternatively, the attachment between the third flange 31 and the fourth flange 32 can be achieved using grooves. The connecting shaft 21 also comprises a downstream end 21b opposite the upstream end 21a along the longitudinal axis X.

[0046] In the present example, the attachment between the third flange 31 and the fourth flange 32 advantageously, but not limitatively, has a flexibility or flexibility allowing the movements of the low pressure shaft and in particular the misalignments of the connecting shaft 21 relative to the low pressure shaft 2.

[0047] The connecting shaft 21 has a flexibility (radial and rotational) making it possible to withstand misalignments between the low-pressure shaft 2 and the electrical machine 15 which is supported by at least its own rotation bearing. The connecting shaft 21 comprises, for example, an annular ferrule 41, substantially of frustoconical shape, which extends radially outwards from the upstream end 21a and which gives flexibility to the connecting shaft 21. The flexibility may also be determined by a predetermined length and / or by a predetermined wall thickness. The connecting shaft 21 may have a length of between 250 mm and 500 mm and which is less than the low-pressure shaft. The length of the connecting shaft 21 may be similar to that of the flexible input shaft of the speed reducer that the turbomachine may comprise.Advantageously, but not limited to, the thickness of the connecting shaft may be between 1 and 10 mm and preferably between 2 and 5 mm. The fixing with the fixing members 33 can provide this flexibility as seen previously. The misalignments between the two shafts may be due to the flexibilities of the stators which respectively support the connecting shaft 21 and the low pressure shaft 2 and which are different. Any thermal expansions of different members of the turbomachine, in particular the shafts (low pressure shaft 2 which is swept by the gases from the combustion chamber) and connecting shaft 21, may cause an elongation and / or axial displacement of these relative to the stator of the turbomachine and transiently.Typically, the stators of the turbomachine will be exposed first to the highest temperatures which will cause their thermal expansion, then the rotors which are exposed to temperatures lower than those seen by the stators will expand in a second stage. The displacements and elongations are preferably taken up by the sliding grooves and / or deformations of the fixing flanges due to their flexibility.

[0048] According to an exemplary embodiment, the connecting shaft 21 is hollow. The fact that the shaft is hollow allows a gain in mass and flexibility. Alternatively, in the case of fixing members comprising splines, the internal cavity of the connecting shaft allows the passage of tools to tighten, for example, a nut on the splines. The connecting shaft 21 is advantageously closed at a downstream end 21b, for example by a plug 23 and at its upstream end 21a for example by a radial wall 42. The radial wall 42 comprises for example an annular flange 42a which is installed axially between the third and fourth fixing flanges 31, 32. The fixing members pass for example through the annular flange 42a of the radial wall 42.

[0049] With reference to [Fig. 4], sealing elements are provided to at least partially isolate the second enclosure 19 from the first enclosure 7. The sealing elements comprise, for example, a seal 35 which is arranged radially between the stator armature 20 and the connecting shaft 21. More precisely, the stator armature 20 comprises an annular ferrule 34 which extends along the longitudinal axis X and which is arranged radially around the connecting shaft 21. A support shaft 47 may be mounted so as to rotate integrally with the connecting shaft 21, for example using tight splines. The seal 35 is mounted radially between the annular ferrule 34 and the support shaft 47, and preferably towards the upstream end 47a of the support shaft 47. Alternatively, the annular ferrule 34 could be axially shorter and the seal placed further upstream.Of course, the seal 35 could be mounted radially between the annular ferrule 34 and the connecting shaft 21 directly. Indeed, the support shaft 47 has a diameter greater than that of the connecting shaft 21 which makes it easier to integrate the connection device 30. The connecting shaft 21 could include this greater diameter so as to dispense with the support shaft 47.

[0050] Another seal 36 is mounted radially between the casing 22 and the connecting shaft 21, preferably towards the downstream end 47b of the support shaft 47.

[0051] [Fig.5] illustrates sealing elements 46 which are also arranged between members of the stator armature 20, at least one of which separates the electric machine rotor 25 from the electric machine stator 24. Preferably, the sealing elements 46 are arranged between cylindrical bearing surfaces 43 of the stator armature 20 and a stator wall 45 secured to the cylindrical bearing surfaces 43. Advantageously, the stator wall 45 supports at least a portion of the electric machine. In other words, the sealing elements 46 are placed between two stator parts. In particular, each first and second arm 20a, 20b comprises one of the cylindrical bearing surfaces 43. Optionally, the stator wall 45 extends axially between the first and second arms 20a, 20b and radially between the stator 24 and the rotor 25 of the electric machine. The stator wall 45 is centered here on the longitudinal axis X. Advantageously, but not limitingly, the stator wall 45 extends opposite the electric machine rotor 25.

[0052] Advantageously, the stator wall 45 is configured to separate the electric machine stator 24 from the electric machine rotor 25 and thereby enclose the electric machine stator 24 in a volume formed by the housing 26, the armature of stator 20 and the stator wall 45. Preferably, the stator wall 45 seals the electric machine stator 24 in said volume. In other words, the stator wall 45 is part of the stator module of the electric machine 15. Advantageously, but not limitingly, the stator module comprises the stator armature 20, the electric machine stator 24, the housing 26, possibly a heat exchanger 70. The sealing elements 46 comprise for example O-rings which are arranged radially between each cylindrical bearing surface 43 and the stator wall 45, and preferably each in a groove of the cylindrical bearing surfaces 43.

[0053] With reference to figures 2 and 3, the electric machine 15 comprises a drive shaft 37 which is on the one hand, integral in rotation with the rotor 25 of the electric machine 15 and on the other hand connected to the connecting shaft 21. Optionally, the drive shaft 37 is centered and coaxial with the connecting shaft 21. At least one annular ferrule 38 makes it possible, for example, to connect the drive shaft 37 to the electric machine rotor 25. The drive shaft 37 is supported by at least one rotation bearing 40. In the present embodiment, there are two rotation bearings. Each rotation bearing 40 comprises an inner ring 40a secured to the drive shaft 37 and an outer ring 40b secured to a bearing support 39 secured to the stator armature 20. Rolling members 40c are arranged between the inner and outer rings 40a, 40b. Advantageously, but not limited to, the rolling members are balls.In other words, the electric machine 15 is on its own rotating bearings.

[0054] In [Fig. 3], the support shaft 47 is configured to transmit the rotational movement of the low pressure shaft 2 to the drive shaft 37 of the electrical machine 15. The support shaft 47 is also configured to accommodate the connection device 30 that couples and uncouples the rotor 25 from the low pressure shaft 2. The diameter of the support shaft 47 facilitates integration although it is optional. The connection device 30 comprises first dog teeth 53 connected to the drive shaft 37 that are intended to mesh with second dog teeth 54 connected to the connecting shaft 21.

[0055] More specifically, the connection device 30 comprises for example a carriage 50 cooperating with the drive shaft 37 of the electrical machine 15. In the present embodiment, the carriage 50 comprises external splines 51 which extend along the longitudinal axis X. These external splines 51 are intended to engage with internal splines 52 which are carried by the drive shaft 37. The internal splines 52 also extend along the longitudinal axis X. This cooperation allows the carriage 50 to be axially movable relative to the drive shaft 37 between a coupling position and a disengagement position. coupling.

[0056] With reference to [Fig. 4], the first dog teeth 53 are carried by the carriage 50 while the second dog teeth 54 are carried by an external ring gear 44 fixed and integral in rotation with the support shaft 47. Advantageously, the external ring gear 44 extends radially outside the support shaft 47. The external ring gear 44 is secured to the support shaft 47, for example, by means of sliding splines 48, 49. The external ring gear 44 comprises, for example, internal splines 48 which extend along the longitudinal axis X and the support shaft 47 comprises, for example, external splines which extend axially. These internal splines 48 and external splines 59 are intended to engage with each other and form the sliding splines. These sliding grooves 48, 49 allow the connecting shaft 21 to move axially according to thermal expansions.The diameter of the support shaft 47 promotes the arrangement of the sliding splines 48, 49 and the sliding of the connecting shaft 21. The first dog teeth 53 are arranged for example at an upstream end 50b of the carriage 50 and in the form of an annular row. Similarly, the second dog teeth 54 are positioned at an upstream end 44a of the external crown 44 and in the form of an annular row. The first and second teeth extend axially. According to an alternative embodiment, the carriage 50 is arranged so as to slide relative to the support shaft 47 and the fixed crown 44 is integral with the drive shaft 37.

[0057] In this way, the low pressure shaft 2 drives the rotor 25 of the electric machine in rotation via the connecting shaft 21, the support shaft 42, the external crown 44, and the dog teeth 53, 54 which are engaged in each other in the coupling position of the carriage 50. The coupling position where the dog teeth 53, 54 are engaged is illustrated precisely in [Fig.6].

[0058] Advantageously, but not limitatively, and as can be seen in [Fig. 4], at least one rolling bearing 56 is mounted radially between the external ring gear 44 and a portion of the casing 22 or of the stator armature 20. The or each bearing 56 makes it possible to control the position of the ring gear 44 and better operation of the connection device 30. Good positioning of the ring gear 44 implies that the splines 51, 52 and the dog teeth 53, 54 are well positioned relative to each other. Preferably, a double ball bearing is provided so as to obtain very little axial play.

[0059] In the event of the need to uncouple the rotor 25 of the electric machine 15 and the low-pressure shaft, the first dog teeth 53 disengage from the second dog teeth 54. The carriage 50, which may comprise the first dog teeth 53, moves upstream here. In this position, the rotor 25 of the electric machine 15 is no longer driven by the low-pressure shaft 2.

[0060] Advantageously, but not limitatively, the carriage 50 is controlled by an actuator 55 between the coupling position and the uncoupling position. The actuator 55 may be a jack which comprises a casing which is carried by the casing 22 or by the stator armature 20, or even by both the casing 22 and the stator armature 20, and a rod, sliding inside the housing. The rod of the jack slides for example along the radial axis Z. To move from the coupling position to the uncoupling position if necessary, the rod of the jack applies a force to the carriage 50 which disengages the first dog teeth 53 from the second dog teeth 54.

[0061] According to an advantageous, but non-limiting, configuration, the connection device 30 is arranged towards the downstream end 21b of the connecting shaft 21. The seals 35, 36 are arranged axially on either side of the connection device 30. The arrangement of the connection device 30 towards the downstream of the electrical machine makes it possible to have a connecting shaft 21 with a greater length than if the connection device 30 were arranged upstream. Furthermore, the arrangement of the seals 35, 36 provides, for example, flexibility to the connecting shaft 21.

[0062] Advantageously, but not limitatively, the seals 35, 36 are not pressurized. Indeed, a pressurized air flow passing through the low-pressure shaft is directed towards the cavity 16 which surrounds the electrical machine 15. However, the connecting shaft 21 being closed at each of its ends 21a, 21b, and the electrical machine 15 being enveloped by the casing 22, the stator armature and the housing, the pressurized air flow does not reach the seals 35, 36. The non-pressurized seals 35, 36 make it possible to avoid a dedicated system for separating the air from the oil which could be complex to install in a restricted environment and impact the mass of the turbomachine.

[0063] With reference to [Fig. 6], the turbomachine comprises a lubrication system 60 for at least one rotation bearing 40 of the electric machine 15 and which is contained at least in part in the second enclosure 19. The lubrication system 60 comprises a lubrication circuit 61 for the rotation bearing(s) 40 and a feed pump 62 allowing the circulation of a lubricant in the lubrication circuit 61. The lubricant advantageously makes it possible to lubricate and cool the bearings 40. In the present exemplary embodiment, the second enclosure 19 is supplied with lubricant via the feed pump 62 which is driven in rotation by the low-pressure shaft 2 or the rotor 25 of the electric machine 15.For this, the external crown 44 comprises at a downstream end 44b (axially opposite the upstream end 44a) an annular row of external teeth 63 which mesh with teeth of a pinion 64 for actuating the feed pump 62. The latter is connected to a lubricant supply source.

[0064] As shown in [Fig. 6], the lubricant supply source is a reservoir 65 arranged radially outside the electrical machine 15 (in particular around the housing 26 forming the external casing of the electrical machine 15) and located on an angular sector substantially at 6 o'clock with reference to the dial of a clock. The reservoir 65 is in fluid communication with the feed pump 62. The casing 22 here envelops the feed pump 62 and receives the downstream end 21b of the connecting shaft 21. The feed pump 62 could comprise its own independent casing fixed to the casing 22 or its casing could be directly integrated into the casing 22. Advantageously, the casing of the pump would be only a part of the casing 22, the other part of the casing 22 serving in particular to close the enclosure and to provide support for the seal 36.

[0065] The lubrication circuit 61 comprises passages which are arranged in the electrical machine 15 and which open at the level of the rotation bearings 40 or the splines to be lubricated. Passages are also provided to open and return the lubricant to the reservoir 65. An example of passage 66 is arranged in the first and second arms 20a, 20 of the stator armature 20. In other words, the lubricant which circulates in the second enclosure 19 falls back (by gravity) into the reservoir 65. In this way, the lubrication system is arranged according to a closed loop. Such a configuration of the closed-loop lubrication system makes it possible to avoid constraints of arrangement of services outside the second enclosure 19 which implies a saving in mass and a simpler arrangement. Since the lubricant is circulated by pump 62 and by gravity, it is not necessary to check the passages in the lubrication circuit.

[0066] In order to cool the lubricant which circulates in a closed loop, the turbomachine 1 comprises for example at least one heat exchanger 70 which is shown precisely in Figures 5 and 6. Indeed, the lubricant which circulates within the second enclosure 19 heats up in contact with the bearings and grooves. The calories must be evacuated. The lubrication system 60 is configured so as to transfer the lubricant to the heat exchanger 70. Advantageously, but not limitingly, the heat exchanger 70 is arranged in the housing 26 of the electric machine 15. The heat exchanger 70 comprises for example at least two heat exchange circuits. One of the heat exchange circuits comprises a portion of the lubrication circuit in which the lubricant circulates. Another of the heat exchange circuits comprises a portion of a cooling circuit 71 in which a heat transfer fluid circulates intended to cool the lubricant.

[0067] With reference to figures 5 and 6, the cooling circuit 71 comprises conduits 72 which are arranged in the housing 26 and which open opposite the stator of the electric machine 24. The circuit comprises an inlet 73 (shown in dotted lines) which is connected to an external source of heat transfer fluid and which opens into the conduits 72. Passages connect the conduits 72 to a part 74 of the electric machine 15, formed between the cylindrical bearing surfaces 43 and the housing 26. The cooling circuit further comprises an outlet 75 (shown in dotted lines) which opens on the one hand, into the cavity 74 and on the other hand, onto the external surface of the housing 26. In this way, the heat exchanger 70 makes it possible to cool both the electric machine 15 and the lubricant of the lubrication system.

[0068] The connecting shaft 21 makes it easier to install an electric machine 15 which rests on its own bearings. This configuration of the electric machine 15 makes it easier to assemble and disassemble it in a modular manner relative to the rest of the turbomachine, in particular the low-pressure shaft 3. For example, the connecting shaft 21 is first fixed to the low-pressure shaft. The elements of the electric machine 15 are then mounted relative to the connecting shaft 21 and to the stator of the turbomachine. The thermal protection 18 and the cover 17 are then added to protect the electric machine 15.

Claims

Claims

1. A turbomachine (1), in particular for an aircraft, comprising: - a low-pressure shaft (2) extending along a longitudinal axis (X) to a rear end (3), - a turbomachine stator (4) supporting the rear end (3) of the low-pressure shaft (2) by a rear bearing (5) which is arranged in a first lubrication enclosure (7), and - an electric machine (15), located at the rear of the turbomachine, comprising an electric machine stator (24) fixed to the stator (4) of the turbomachine and an electric machine rotor (25) capable of being driven in rotation in a disconnectable manner by the low-pressure shaft (2) by means of a connection device (30),characterized in that the electric machine (15) is contained in a second dedicated lubrication enclosure (19) which is separate from the first lubrication enclosure (7) and in that the electric machine rotor (25) is supported by at least one rotation bearing (40) which is arranged in the second enclosure (19), the turbomachine (1) comprising a lubrication system (60), of the at least one rotation bearing (40), which is contained in the second enclosure (19).,

2. Turbomachine (1) according to the preceding claim, characterized in that the lubrication system (60) comprises a lubrication circuit (61) of at least the rotation bearing (40) and a feed pump (62) allowing the circulation of lubrication in the lubrication circuit (61), the feed pump (62) being driven in rotation by the low pressure shaft (2) or the electric machine rotor (25).

3. Turbomachine (1) according to the preceding claim, characterized in that the lubrication system (60) comprises a reservoir (65) arranged radially outside the electric machine (15) and located on an angular sector substantially at 6 o'clock with reference to the dial of a clock, the reservoir (65) being in fluid communication with the feed pump (62).

4. Turbomachine (1) according to one of the preceding claims, characterized in that the electric machine (15) comprises a heat exchanger (70) configured to cool the lubricant of the lubrication system (60) and the electric machine (15).

5. Turbomachine (1) according to the preceding claim, characterized in that the heat exchanger (70) is arranged in a housing (26) surrounding the stator (24) of the electric machine (15).

6. Turbomachine (1) according to one of the preceding claims, characterized in that it comprises a connecting shaft (21) which is coupled to the rear end (3) and which extends the low pressure shaft (2) rearwardly along the longitudinal axis (X) and in that the electric machine rotor (25) is connected to a drive shaft (37) which carries the at least one rotation bearing (40), the connection device (30) being configured so as to secure or detach in rotation the drive shaft (37) from the connecting shaft (21).

7. Turbomachine (1) according to the preceding claim, characterized in that the second enclosure (19) is delimited at least in part by the connecting shaft (21), a stator armature (20) which is connected to the electric machine stator (24) and the electric machine rotor (25), sealing elements (35, 36, 46) being arranged on the one hand between the stator armature (20) and the connecting shaft (21), and on the other hand between members of the stator armature (20) separating the electric machine rotor (25) from the electric machine stator (24).

8. Turbomachine (1) according to one of claims 6 and 7, characterized in that the connection device (30) comprises first dog teeth (53) which are connected to the drive shaft (37) and which are intended to mesh or disengage with second dog teeth (54) connected to the connecting shaft (21).

9. Turbomachine (1) according to the preceding claim, characterized in that the connection device (30) comprises a carriage (50) which cooperates with the drive shaft (37) and which carries the first dog teeth (53), the carriage (50) being controlled in displacement along the longitudinal axis (X) relative to the drive shaft (37) between a coupling position and a decoupling position by an actuator (55).

10. Turbomachine (1) according to one of claims 7 to 9, characterized in that sealing elements (35, 36, 46) are arranged on either side of the connection device (30) along the longitudinal axis (X).

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