TURBOMACHINE EQUIPPED WITH A DISCONNECTABLE ELECTRIC MACHINE AND AN AUTOMATIC ELECTRIC MACHINE CONNECTION DEVICE

Abstract

The invention relates to a turbomachine (1) comprising:- a shaft of longitudinal axis (X) having a rear end supported by a stator (4) of the turbomachine via a rear bearing (6),- an electrical machine (10), located at the rear of the turbomachine, comprising a stator and a rotor driven in rotation by the shaft,- a connection device (25) configured to connect or disconnect in rotation the rotor from the shaft (2), and- an actuator (40) acting on the connection device (25). According to the invention, the connection device comprises a first carriage (34) carrying first teeth (32) meshing with second teeth (33) of the shaft and translating axially between coupling and uncoupling positions, and a second carriage (54) connected to a movable body (42) of the actuator and integral in movement with the first carriage (34), a bearing (51) being arranged between the first and second carriages (34, 50). Figure for the abstract: Fig. 2

Description

Title of the invention: TURBOMACHINE EQUIPPED WITH A DISCONNECTABLE ELECTRIC MACHINE AND A DEVICE FOR AUTOMATICALLY CONNECTING THE ELECTRIC MACHINE 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 comprises a rotor which is rotationally coupled with the low pressure shaft of the turbomachine which extends furthest to the rear of the turbomachine. However, the rotor of the electric machine is not mounted directly on a rear end of the low pressure shaft but on a connecting shaft so as not to weigh down the low pressure shaft and also because of the increasingly reduced size of the turbomachine shafts. The electric machine is mounted independently of the rest of the turbomachine so as to facilitate its maintenance using a connection device which is configured to couple or uncouple the shaft connecting device which is integral in rotation with the rotor of the electric machine of the low pressure shaft, for example in the event of damage. Indeed, the malfunction of the electric machine can have repercussions on the low pressure shaft which can impact the operation of the turbomachine. In this case, the turbomachine can stop working by itself which can be detrimental and / or following the intervention of an operator to preserve it in flight. The connection device comprises a rod or a finger actuated by an actuator which is mounted on a stator of the turbomachine and which acts directly on the connecting shaft to move it and cause its disconnection with the low pressure shaft. An example of an electric machine at the rear of the turbomachine cooperating with a connection device equipped with a finger is described in document FR-A1-3130323.

[0005] However, such direct contact induces significant friction between the parts which are in different reference frames and which operate at different speeds, which can lead to a safety risk (for example a fire) and impact the service life of the actuator and the connecting shaft.

[0006] There is a need to resolve all or part of the aforementioned drawbacks. Summary of the invention

[0007] The objective of the present invention is to provide a solution making it possible to achieve a transition between connection means of a turbomachine shaft driving in rotation a rotor of an electric machine which is independent and autonomous in terms of arrangement, and said shaft in a simple, economical, durable, repetitive and robust manner.

[0008] 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 which is supported by a stator of the turbomachine via a rear bearing, - 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 by the low pressure shaft, - a connection device configured so as to connect or disconnect in rotation the rotor of the electric machine from the low pressure shaft, and - at least one actuator fixed to the stator of the turbomachine and capable of acting on the connection device, the connection device comprising a first carriage which carries first teeth intended to mesh with second teeth carried by the low pressure shaft and which is able to move along the longitudinal axis between a coupling position and a decoupling position, and a second carriage which is connected to a movable body of the actuator and which is integral in movement with the first carriage, at least one bearing being arranged between the first carriage and the second carriage.

[0009] Thus, this solution makes it possible to achieve the aforementioned objective. In particular, such a configuration of the connection device makes it possible to avoid direct contact of a stator part on the low-pressure rotor shaft so as to cancel the movement of the rotor of the electrical machine on the low-pressure shaft. This connection device ensures the safety of the turbomachine by preventing fires from sparks due to excessive friction in a high-temperature and restricted area and by eliminating certain risks of shaft breakage, for example. Furthermore, this solution is also non-destructive and reversible because it makes it possible to preserve the integrity of the parts to disconnect the electrical machine for the purpose of subsequent maintenance of the latter and to be able to reconnect the electrical machine once it is in operating condition so that it is re-driven by the low-pressure shaft.Added to this is the fact that such a configuration requires very few structural modifications to the turbomachine. Keeping the actuator at the stator reference level helps to contain the costs of the turbomachine.

[0010] The turbomachine also comprises one or more of the following features and / or steps, taken alone or in combination: - the bearing comprising an inner ring which is secured to the first carriage, an outer ring which is secured to the second carriage and rolling members installed between the inner and outer rings. - the first carriage carries external splines intended to engage with internal splines of a rotor shaft of the electric machine so as to move relative to the rotor shaft. - the actuator comprises a fixed body and the movable body is mounted movable relative to the fixed body, the movable body being connected to the second carriage by at least one connecting rod. - the moving body moves along an axis offset or transverse to the longitudinal axis. - the turbomachine comprises at least one elastic return element configured so as to exert a force on the moving body so as to separate the rotor of the electric machine from the low pressure shaft. - the turbomachine comprises at least one elastic return element configured so as to exert a force on the moving body so as to maintain the solidity of the rotor of the electric machine with the low pressure shaft. - the actuator is connected to an electronic unit which is configured to check the operation of the connection device at least every starting the turbomachine by successively connecting and disconnecting the rotor of the electric machine from the low pressure shaft. - the actuator is connected to an electronic unit which is configured to detach the rotor from the electrical machine via the actuator according to a predetermined parameter or a predetermined action. - the connection device comprises coupling members which have first teeth connected to the electric machine and second teeth connected to the pressure base shaft. - the connection device comprises sliding grooves between the rotor shaft of the electric machine and at least one member of the connection device. - the first carriage is axially movable relative to the rotor shaft using sliding splines between a coupling position and an uncoupling position. - - the connecting rod is articulated at each of its first and second ends.

[0011] - - there are as many connecting rods as there are actuators

[0012] The invention relates to an aircraft comprising at least one turbomachine having any one of the aforementioned characteristics.

[0013] According to one aspect, the invention relates to a method for controlling a connection device of a turbomachine, implemented by an electronic unit, the turbomachine comprising an electric machine which is mounted at a rear end of a low-pressure shaft which is supported by a stator of the turbomachine via a rear bearing, and which comprises an electric machine rotor which is capable of being driven in rotation by the low-pressure shaft via the connection device, the turbomachine comprising an actuator acting on the connection device and being connected to an electronic control unit, the method comprising at least one step of verifying the operation of the connection device at each start-up of the turbomachine by controlling the actuator to successively secure and detach the rotor of the electric machine from the low-pressure shaft. Brief description of the figures

[0014] 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:

[0015] - [Fig.l] is a schematic and partial axial sectional view of an example of turbomachine to which the invention applies;

[0016] - [Fig.2] is an example of an embodiment of a connection device between a rotor of an electric machine and a low pressure shaft of a turbomachine according to the invention;

[0017] - [Fig.3] illustrates in a partial axial sectional view a rotor of a electric machine connected to a low pressure shaft of a turbomachine according to the invention;

[0018] - [Fig.4] illustrates in an axial and partial sectional view the rotor of the machine electric which is no longer connected to the low pressure shaft of the turbomachine according to the previous figure;

[0019] - [Fig.5] represents an embodiment of an actuator connected to a device of connection and elastic return means cooperating with said actuator according to the invention;

[0020] - [Fig.6] represents another embodiment of an actuator connected to a connection device and elastic return means cooperating with said actuator according to the invention; and,

[0021] - [Fig.7] represents another embodiment of an actuator connected to a connection device and elastic return means cooperating with said actuator according to the invention. Detailed description of the invention

[0022] [Fig. 1] 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 comprises a fan or a propeller which is ducted or not ducted. Only the rearmost or downstream part of the turbomachine along the longitudinal axis X is shown in [Fig. 1].

[0023] 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.

[0024] 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 par 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.

[0025] The low pressure shaft 2 is supported by a stator 4 of the turbomachine using several bearings. The stator 4 is for example a casing and preferably an exhaust casing 5. More precisely, the turbomachine comprises a rear bearing 6 allowing the stator 4 to support the rear end 3 of the low pressure shaft 2. Optionally, the rear bearing 6 comprises an inner ring 6a secured to the rear end 3 of the low pressure shaft 2 and an outer ring 6b secured to a cylindrical bearing surface 7a of the stator 4 of the turbomachine. The cylindrical bearing surface 7a is for example secured to a bearing support 7. Rolling members 6c, for example rollers, are arranged between the inner and outer rings 6a, 6b.

[0026] Advantageously, the rear bearing 6 is arranged in a first lubrication enclosure 8. This first lubrication enclosure 8 is for example closed by means of one or more seals which are arranged between walls (of shafts, ferrules, etc.) delimiting the first enclosure 8. The first enclosure 8 can be connected to a lubrication circuit which is supplied by a power source (not shown). The lubricant is preferably oil (in the form of a mist) which makes it possible to lubricate and cool at least the rear bearing 6.

[0027] The turbomachine 1 comprises an electrical machine 10 which is located at the rear of the turbomachine. The electrical machine 10 is advantageously housed in a cavity 11 which is formed downstream of the rear end 3 of the low-pressure shaft. In other words, the electrical machine 10 is arranged downstream of the rear end 3 of the low-pressure shaft. The cavity 11 is closed at least in part by a cover 12 which is fixed to the stator 4, and in particular to the exhaust casing 5 of the turbomachine, by a bolted connection for example. A thermal protection 13 can be applied to the internal wall of the cover 12 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.

[0028] The electric machine 10 is arranged more precisely in a second lubrication enclosure 15 which is dedicated for the electric machine 10 and which is distinct from the first lubrication enclosure 8. The second enclosure 15 is contained in the cavity 11. The second enclosure 15 is delimited by walls (of shafts, ferrules, etc.). Seals may be arranged between certain walls.

[0029] The electric machine 10 comprises a stator 16 and a rotor 17. The electric machine 10 can alternately operate in generator mode and in motor mode. That is, the electric machine 10 can draw power from the low shaft pressure 2 or inject power onto the low pressure shaft 2. Advantageously, but not limited to, the electric machine stator 16 comprises stator windings (or coils) and the electric machine rotor 17 comprises permanent magnets. The stator windings are intended to be electrically powered.

[0030] In the present example, the stator 16 of the electric machine 10 surrounds the rotor 17 of the electric machine 15 and is fixed to the stator 4 of the turbomachine. As shown in [Fig.l], the cover 12 equipped with the thermal protection 13 advantageously surrounds the stator 16 of the electric machine 10.

[0031] Advantageously, but not limitingly, the electric machine stator 16 comprises a stator armature 18 which comprises a first arm 19a and a second arm 19b and which are located on either side of the electric machine stator 16 along the longitudinal axis X. The electric machine 10 may comprise a housing (not shown) which radially surrounds the stator 16 and the rotor 17 of the electric machine. The first arm 19a may be fixed upstream of the housing and the second arm 19b may be fixed downstream of the housing. The first and second arms 19a, 19b extend radially towards the longitudinal axis X. The rotor 17 and the stator 16 are contained axially between the first and second arms 19a, 19b and optionally radially in the housing.

[0032] The electric machine stator 16 (and in particular the stator armature 18) comprises a fixing flange 20 which is fixed to a fixing flange 21 of the stator 4 of the turbomachine (in particular the exhaust casing 5). The flanges 20, 21 extend radially and fixing members 26 allow them to be fixed together.

[0033] The rotor 17 of the electric machine 10 is advantageously driven by the low-pressure shaft 2 in a disconnectable manner. This is made possible by a connection device 25 which is configured so as to couple or uncouple in rotation the rotor 17 of the electric machine 10 from the low-pressure shaft 2. The uncoupling can occur in the event of damage to the electric machine 10 which would require the rotor 17 of the electric machine 10 to no longer be driven by the low-pressure shaft 2. The rotor 17 of the electric machine can be blocked and impact the operation of the turbomachine and its drag. Disconnecting the rotor 17 from the electric machine 10 makes it possible to avoid stopping the low-pressure shaft 2 which would cause the turbomachine to shut down. In the case where the turbomachine is shut down but not blocked, the fan or the propeller rotates naturally, which limits its drag.

[0034] For this purpose and as shown in [Fig.l], the turbomachine 1 comprises a connecting shaft 26 which extends along the longitudinal axis X and downstream of the rear end 3 of the low pressure shaft 2. The connecting shaft 26 extends the low pressure shaft 2 towards the rear of the turbomachine 1. The connecting shaft 26 is advantageously coaxial with the low pressure shaft 2. The connecting shaft 26 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. The connecting shaft 26 comprises for example a fixing flange 27 which is fixed to a fixing flange 28 of the rear end 3. The fixing is carried out here by a bolt-type fixing member so as to easily separate or secure the connecting shaft 26. Other similar fixing members can be used to carry out this fixing. 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 connecting shaft 26 to access the electric machine 10, which rests on this connecting shaft 26 and possibly extract it. The turbomachine 1 can continue to operate without the electric machine 10.

[0035] With reference to Figures 1 and 2, the electrical machine 10 comprises a rotor shaft 29 which is, on the one hand, integral in rotation with the rotor 17 of the electrical machine 10 and, on the other hand, connected to the connecting shaft 26. Optionally, the rotor shaft 29 is centered and coaxial with the connecting shaft 26. The rotor shaft 29 is secured to the rotor 17, for example using tight splines (not shown). The rotor shaft 29 is supported by at least one rotation bearing 30.

[0036] In the present embodiment, there are two rotation bearings 30 and these two rotation bearings are mounted for example between the first and second arms 19a, 19b, and the rotor shaft 29. Each rotation bearing 30 comprises an inner ring 30a secured to the rotor shaft 29 and an outer ring 30b secured to one of the first and second arms 19a, 19b of the stator armature 18. Rolling members 30c are arranged between the inner and outer rings 30a, 30b. Advantageously, but not limitingly, the rolling members of one of the bearings are balls and of the other of the bearings are rollers. In other words, the electric machine 10 is on its own rotational bearings 30. Furthermore, the electric machine 10 can be easily extracted by dismantling the fixing members at the fixing flanges 21 and 22 and removing the rotor shaft 29.

[0037] The connection device 25 comprises coupling members 31 which are provided for coupling or uncoupling the rotor of the electric machine from the low-pressure shaft 2. The coupling members 31 may be of the type known by the English expression "curving coupling" or of the dog type. The cutting members of the curving coupling type allow centering, coupling and transfer of the torque from the low-pressure shaft to the rotor of the electric machine or vice versa. Conversely, the dog type members only allow coupling and transfer of torque. Advantageously, the coupling members 31 comprise first teeth 32 connected to the rotor shaft 29 which are intended to mesh with second teeth 33 connected to the low-pressure shaft 2. The first and second teeth 32, 33 are in the form of an annular row and each preferably extends axially.

[0038] The connection device 25 also comprises at least in part sliding grooves 35 allowing the translational movement of one of the first and second teeth 32, 33.

[0039] In [Fig. 2], the connection device 25 comprises for example a first carriage 34 which is capable of being connected to the rotor shaft 29 on the one hand and to the low pressure shaft 2 on the other hand. The first carriage 34 has an axis of revolution and extends between a first end 34a and a second end 34b. The axis of revolution is advantageously centered on the longitudinal axis X. The first carriage 34 advantageously, but not limited to, comprises the first teeth 32 which are arranged for example at the first end 34a. The second teeth 33 are advantageously, but not limited to, carried by the low pressure shaft 2. In particular, the second teeth 33 are positioned at a ferrule 38 secured to the connecting shaft 26. The second teeth 33 are complementary to the first teeth 32.

[0040] According to an advantageous characteristic, the first carriage 34 comprises external splines 36 which extend along the longitudinal axis X. Advantageously, but not limitingly, the external splines 36 are arranged towards the second end 34b. The external splines 36 are intended to engage with internal splines 37 which are carried in this example by the rotor shaft 29. The internal splines 37 also extend along the longitudinal axis X. The internal splines 37 and the external splines 36 form the sliding splines. This cooperation allows the first carriage 34 to be axially movable relative to the rotor shaft 29 between a coupling position (of the teeth 32, 33) and a decoupling position (of the teeth 32, 33). The sliding grooves also allow the connection device 25 to be directly connected to the electrical machine in order to take into account its operating state.

[0041] According to an alternative embodiment, the first carriage 34 is coupled to the rotor shaft between the coupling position and the uncoupling position.

[0042] Advantageously, but not limitatively, the turbomachine comprises at least one actuator 40 which is fixed to the stator of the turbomachine and which is capable of acting on the connection device 25. In particular, the movement of the first carriage 34 is controlled by an actuator 40 between the coupling position and the uncoupling position. The actuator 40 comprises for example a fixed body 41 which is intended to be fixed on the stator of the turbomachine and a movable body 42 mounted movable relative to the fixed body 41 between a first position and a second position. The stator of the turbomachine here may be the stator armature 18 or the casing exhaust 5.

[0043] In the example shown, the fixed body 41 is carried by a radial flange 43 of the second arm 19b. The radial flange 43 is fixed to a radial fixing flange of the stator. In particular, an annular wall 19c, centered on the longitudinal axis X, extends axially from the second arm 19b (in particular downstream) and the radial flange 43 extends radially from an end of the annular wall 19c which is opposite the annular wall 19b.

[0044] The actuator 40 comprises for example a tubular section 44 and an annular base 45 which extends radially from one end of the wall of the tubular section 44. The annular base 45 rests on an external surface of the annular wall 19c and the tubular section 44 passes through a radial opening formed in the annular wall 19c. The tubular section 44 extends radially according to this exemplary embodiment.

[0045] The movable body 42 of the actuator 40 slides inside the fixed body 41 between the first position and the second position. The axis A of movement of the movable body 42 is offset or transverse relative to the longitudinal axis X. The movable body 42 is here in the form of a piston 46 which moves in the present example along the radial axis. The piston 46 is advantageously cylindrical and has a circular section. The movable body 42 comprises a collar 47 which extends radially, at a first end 46a, from the external wall of the piston 46. Advantageously, but not limitingly, the piston 46 extends inside the tubular section 44 and the collar 47 is arranged radially outside the annular base 45. Of course, the piston 46 can move through the radial opening of the annular wall 19c.In this example, the actuator 40 is installed radially (radial displacement of the mobile body 42) in order to use the space available at this location and to reduce the overall size. Of course, the actuator 40 could be installed in the turbomachine 1 so that the mobile body 42 moves axially. In this case, the axis of movement of the mobile body 42 is parallel and offset relative to the longitudinal axis X.

[0046] The actuator 40 is connected to a power source 49, for example an electrical power source. The electrical energy may be supplied by the electrical machine. The actuator 40 may also be powered by a pneumatic or hydroelectric power source. According to a further alternative, the power source may be an electrical circuit powered by an electrical generator which is driven by a high-pressure shaft. In this case, the electrical circuit may comprise an accumulator.

[0047] In the first position of the movable body 42, the first carriage 34 is coupled to the low pressure shaft 2 (coupling position) and in the second position of the movable body 42, the first carriage 34 is uncoupled from the low pressure shaft 2 (uncoupling position). Alternatively, when the movable body 42 is in the second position, the first carriage 34 is in the coupling position and when the movable body 42 is in the first position, the first carriage 34 is in the uncoupling position. The actuator 40 is reversible and the position of the movable body 42 will depend on the state of the electrical power supply. The actuator 40 has a natural ability to change state.

[0048] Optionally, the actuator 40 is configured to have an active state and an inactive state. In the active state, the actuator 40 is supplied with electrical energy and in the inactive state, the actuator 40 is not supplied with electrical energy.

[0049] The connection device 25 comprises for example a second carriage 50 which is integral in movement with the first carriage 34. The second carriage 50 can be connected to the movable body 42 of the actuator 40. The second carriage 50 is configured so as to guarantee the position of the first carriage 34. Furthermore, the second carriage 50 advantageously ensures the transmission of forces to the first carriage 34. The second carriage 50 has in this example an axis of revolution advantageously centered on the longitudinal axis X and extends between a first end 50a and a second end 50b. The second carriage 50 optionally extends radially around the first carriage 34.

[0050] Between the first carriage 34 and the second carriage 50 is arranged at least one bearing 51. The arrangement of the bearing 51 makes it possible to ensure the passage from the fixed reference mark (second carriage 50 connected to the actuator 40) to the rotating reference mark (first carriage 34 movable in translation and possibly in rotation when connected to the low pressure shaft 2) in a non-violent manner. Furthermore, such a configuration has a high robustness. More precisely, the configuration does not cause a rise in temperature within the system, no wear of the parts between the rotating reference mark and the fixed reference mark, and has a high force transmission capacity.

[0051] In the example illustrated, there are two bearings 51. Of course, a single bearing or a different number of bearings is possible.

[0052] The or each bearing 51 comprises an inner ring 52a which is secured to the first carriage 34 and an outer ring 52b which is secured to the second carriage 50. Rolling members 52c are installed between the inner and outer rings 52a, 52b. These rolling members 52c are preferably angular contact balls. Such an arrangement of these bearings 51 allows a high axial force and avoids axial play. Of course, the rolling members can have an O-shaped or X-shaped contact, well known to those skilled in the art. The rolling members 52c can also be angular contact rollers.

[0053] Each bearing 51 is advantageously, but not limited to, immobilized axially. Advantageously, the inner ring of the first bearing 51 is mounted in abutment against a shoulder 53 formed on the first carriage 34. On the other hand, the outer ring 52b is held axially between a spacer 54 mounted on the first carriage 34 and a shoulder 55 formed on the second carriage 50. The outer ring 51b of the second bearing 51 is in abutment against a shoulder 56 formed on the second carriage 50 while the inner ring of the second bearing 51b is held by a nut 57. The latter is mounted for example around the first carriage 34 and has an internal thread cooperating with an external thread of the first carriage 34. The nut 57 is mounted here at the second end of the first carriage 34. Advantageously, but not limitingly, the nut 57 applies a tightening torque to the two bearings 51. In this way, the cohesion between the first carriage 34, the or each bearing 51, and the second trolley 50 is insured.

[0054] The connection between the second carriage 50 and the movable body 42 is made by at least one connecting rod 58. The latter is configured so as to transmit the force from the actuator 40 to the second carriage 50. The connecting rod 58 comprises a first end 58a which is mounted in a pivot connection with a second end 46b of the piston 46. The connecting rod 58 comprises a second end 58b which is mounted in a pivot connection with the second end 50b of the second carriage 50. In this example, the axis of the pivot connections is perpendicular to the radial axis and to the longitudinal axis X. Furthermore, in this example, only the connecting rod 58 is mounted articulated between the movable body 42 of the actuator 40 and the second carriage 50. The force from the actuator 40 in the radial direction is transmitted to the first carriage 34 in the axial direction.The installation of the second carriage 50 and the connecting rod 58 makes it possible to increase the service life of the connection device 25 because it avoids direct contact between the movable body 42 of the actuator 40 which is located in a fixed reference frame and the low pressure shaft 2 which is located in a rotating reference frame. The low pressure shaft 2 rotates for example at very high speeds of the order of 10,000 rpm and the movable body 42 of the actuator 40 acting directly on a rotating element could generate sparks, wear, etc.

[0055] Advantageously, but not limitingly, there are as many connecting rods 58 as there are actuators 40.

[0056] [Fig. 3] illustrates the connection device 25 in the coupling position. In this figure, the first teeth 32 of the first carriage 34 are engaged with the second teeth 33 of the connecting shaft 26. The external splines of the first carriage 34 are also coupled with the internal splines of the rotor shaft 29. The actuator 40 is in its active state, that is to say that it is supplied with electrical energy and the movable body 42 is in a first position in which it keeps the first carriage 34 coupled with the low pressure shaft 2 (here the connecting shaft 26). In this way, the low pressure shaft 2 drives the rotor 17 of the electric machine 10 in rotation by means of the teeth 32, 33 which are engaged with each other in the coupling position of the carriage 34.

[0057] [Fig. 4] illustrates the connection device 25 in the uncoupling position. The first teeth 32 are disengaged from the second teeth 33. For this, the first carriage 34 which carries the first teeth 32 is moved here upstream by the actuator 40. To move from the coupling position to the uncoupling position if necessary, the actuator 40 (in its active state) applies a force radially outwards, which allows the pivoting of the connecting rod 58 which is driven by the piston 46 and the movement of the first and second carriages 34, 50 upstream. In this position, the rotor 17 of the electrical machine 10 is no longer driven by the low pressure shaft 2. As is also illustrated, the second end 34b of the first carriage 34 is advantageously, but not limited to, in abutment against a stop surface 59 carried by the rotor shaft 29 of the electrical machine 10.Once the first carriage 34 is decoupled, the actuator 40 is in its inactive state, that is to say that it is no longer supplied with electrical energy.

[0058] Alternatively, when the actuator is in an inactive state then the connection device 25 is in the coupled position and when the actuator is in an active state then the connection device 25 is in the uncoupled position.

[0059] Figures 5 to 6 illustrate embodiments of at least one actuator 40 cooperating with at least one elastic return element 48. The latter is capable of acting on the movable body 42 of the actuator 40. In particular, the return element 48 makes it possible to exert a force on the movable body 42. Advantageously, the force of the elastic return element 48 tends to assist the passage from the first position to the second position or to oppose the passage from the second position to the first position of the actuator 40. In other words, the elastic return element 48 is configured so as to exert a force on the movable body 42 so as to separate the rotor 17 of the electrical machine 10 from the low-pressure shaft 2.This makes it possible to secure the disconnection between the first carriage 34 and the low pressure shaft 2 in the rest state (stoppage of the turbomachine) or in a malfunction state (for example, a shutdown in flight) with the low pressure shaft 2 in autorotation. Conversely, the elastic return element 48 is configured so as to exert a force on the mobile body 42 so as to maintain the connection of the rotor of the electric machine 10 with the low pressure shaft 2.

[0060] Advantageously, but not limitatively, the force exerted by the elastic return element 48 is for example a function of at least one force corresponding to a friction component at the level of the internal and external grooves (sliding grooves 35) between the first carriage and the rotor shaft of the electrical machine 10. In particular, the force exerted by the elastic return element 48 is greater than the force corresponding to the friction component.

[0061] Such a configuration of the elastic return element 48 makes it possible, on the one hand, to overcome a failure of the actuator 40, for example, or in the event of a loss of power thereof, and, on the other hand, to install one or more actuators 40 with low power, which allows for an economic gain.

[0062] The return element 48 is chosen from the group comprising at least one spring, one coil and one Belleville type washer.

[0063] In [Fig. 5], the elastic return element 48 comprises two springs 48a, 48b which are mounted between the base 45 of the movable body 42 of the actuator 40 and the collar 47 of the fixed body of the actuator 40. According to this arrangement, the springs 48a, 48b provide assistance in uncoupling the rotor of the electrical machine 10 from the low-pressure shaft 2. In this embodiment, each spring 48a, 48b is composed of two Belleville-type washers 48a1, 48a2, 48b1, 48b2 arranged one on top of the other. Advantageously, but not limitingly, the washers 48a1, 48a2, 48b1, 48b2 are arranged so as to be in opposition. This arrangement of the washers advantageously involves high forces. Of course, other types of arrangements or return elements are possible. The force of the elastic return element is here greater than the force applied by the actuator 40 for the coupling which is not supplied with electrical energy.In this case, the actuator 40 must be supplied with electrical energy so that it can maintain the coupling position of the first carriage 34. In this example, the actuator 40 can exert a force of 3000 N and the arrangement of the return elements makes it possible to exert a force of 3500 N.

[0064] Alternatively, the operation is reversed when the springs are arranged radially above the base 45 of the movable body 42. In this case, the springs 48a, 48b provide assistance in coupling the rotor of the electrical machine with the low-pressure shaft. In other words, the springs 48a, 48b apply a force to the movable body 42 of the actuator 40 in the direction of the connection device 25. The springs 48a, 48b advantageously make it possible to reduce the force of the actuator 40.

[0065] In [Fig. 6], the elastic return element 48 comprises springs which operate in opposition. The elastic return element 48 here comprises five springs 48a, 48b, 48c, 48d, 48e, including three 48a, 48b, 48c which are mounted radially below the base 45 of the movable body 42 and two 48d, 48e which are mounted radially below the base 45. In this exemplary embodiment, each spring 48a, 48b, 48c, 48d, 48e is composed of two Belleville-type washers stacked on top of each other. Advantageously, but not limitingly, the washers are arranged so as to be in opposition. Of course, other types of arrangements or return elements are possible. In this exemplary embodiment, the three springs 48a, 48b, 48c make it possible to decouple the rotor of the electric machine 10 from the low pressure shaft 2 and the two springs 48d, 48e participate in the force exerted by the actuator 40 on the first carriage 34. The elastic return force of the three springs 48a, 48b, 48c is greater than the elastic return force of the two springs 48a, 48b. More precisely still, the return force of the elastic return element is here greater than the force applied by the actuator 40 which is not supplied with electrical energy and the elastic return force of the springs 48d, 48e. In other words, the elastic return elements 48 generate a prestress taking up part of the load of the actuator and the actuator 40 taking up only the remaining load. According to this embodiment, the elastic return elements 48 are mounted in a housing 61 which is fixed to the annular wall 19c. The housing serves as a guide means for the elastic return elements and / or the piston. The housing 61 also serves as a protection means for the piston 46. Of course, the piston can serve alone as a guide means for the elastic return elements.

[0066] In [Fig. 7], the elastic return element 48 comprises four springs 48a, 48b, 48c, 48d (as illustrated in [Fig. 3]). Two springs 48d, 48e are mounted on either side of the base 45 of the movable body 42. Advantageously, each spring comprises two Belleville-type washers arranged one on top of the other in opposition. The return forces of the two springs on each side of the base are identical. The arrangement of the elastic return elements 48 on either side of the base 45 is considered to be in equilibrium. In particular, in this example, the return elements 48 exert a force which makes it possible to oppose the displacement forces of the carriage 50 and the actuator 40 exerts an additional force to maintain a coupling or uncoupling position.

[0067] According to an alternative, the actuator 40 is dimensioned so as to counter the force of the return elements 48 as well as so as to guarantee the coupling between the first carriage 34 and the low pressure shaft 2.

[0068] According to an advantageous characteristic, the actuator 40 is connected to an electronic unit 60 which is installed for example in the aircraft. The electronic unit 60 can be a computer known by the term FADEC in English for (Full Authority Digital Engine Control). The electronic unit 60 is configured so as to send control orders to the actuator 40 so that the latter acts on the connection device 25. The electronic unit 60 is also able to receive information relating to the operating state or the environment of the electrical machine 10, the torque and / or vibration level of the low pressure shaft or an action (of a pilot for example) to control the actuator 40. This information comes from example of sensors and concern for example the temperature in the electric machine 10 or in its environment, the torque of the rotor shaft 29, a variation or cut-off of the current in the electric machine 10, the torque of the low pressure shaft 2, the vibration level of the low pressure shaft 2, etc.

[0069] By way of example, the electronic unit 60 is configured to check the operation of the connection device 25 at least at each start-up of the turbomachine by successively connecting and disconnecting the rotor 17 of the electric machine 10 from the low-pressure shaft 2. Such a configuration makes it possible to know whether the connection device 25 can be connected or disconnected to the low-pressure shaft 2 to ensure the safety of the turbomachine in all circumstances, in particular in flight and to meet aeronautical standards. In this way, the operation of the connection device 25 is guaranteed at each flight in order to mitigate a risk of damage, the turbomachine being able to operate without the electric machine 10 until the next inspection.

[0070] The electronic unit 60 is also configured to detach the rotor 17 from the electrical machine 10 according to a predetermined parameter or a predetermined order. Such an action is preferably carried out in flight.

[0071] The electronic unit 60 is also configured to secure the rotor of the electric machine to the low pressure shaft. Such an action is for example carried out on the ground after checking the state of the electric machine 10.

[0072] We will now describe an example method for controlling a connection device 25 as described previously. The method comprises at least one step of verifying the operation of the connection device 25 at each start-up of the turbomachine in which the electronic control unit 60 sends a control command to the actuator 40 to successively secure and detach the rotor 17 of the electric machine 10 from the low-pressure shaft 2. The control command is sent automatically at start-up by the electronic control unit 60 for example. This verification step may comprise several successive couplings and decouplings. During this step, the mobile body 42 exerts a force on the first carriage 34 via the second carriage 50.

[0073] If an elastic return element 48 is present, this can help to couple or uncouple depending on the state of the actuator 40. Information on the state of the connection device 25 is sent to the electronic unit 60 after this verification step. If the couplings and uncouplings are successful, the information takes a positive value indicating that the connection device 25 is in working order. If the couplings and uncouplings have not taken place, information concerning a malfunction of the connection device 25 is transmitted to the electronic control unit 60. The malfunction is by example a fault in the movement of the piston 46 of the actuator 40. If the piston does not move then there is no change in position of the second carriage. Advantageously, but not limitingly, a proximity or movement sensor (not shown) may be provided at the actuator 40 and / or at least one of the first and second carriage(s).

[0074] The method comprises a step of detaching the rotor 17 from the electrical machine 10 in which the electronic control unit 60 sends a control command to the actuator 40 to detach the first carriage 34 according to a predetermined parameter or a predetermined action. For this purpose, the electronic unit 60 analyzes information received to detect a particular event or actions received from a pilot. The information comes as stated above from sensor measurements for example. The monitoring by the electronic unit 60 is preferably carried out at several regular intervals. When a torque value is for example greater than a predetermined value, then the electronic unit 60 commands the detachment of the first carriage 34. For this, the electronic unit 60 sends a control command to the actuator 40.The predetermined value is stored in a memory of the electronic unit 60 which is compared with the or each measured value. Other means for detecting a malfunction are possible. Alternatively, the pilot can order the first carriage 34 to be uncoupled. The uncoupling is thus carried out on request or in the event of a malfunction. The pilot can order uncoupling, for example, in the event of extreme temperature readings, in the event of a flight with few or no passengers and / or a shutdown of the turbomachine in flight.

[0075] The connection device 25 as described, connected directly to the electric machine 10 and cooperating with an actuator 40 as described, ensures the reliable, robust and reversible coupling and decoupling of the electric machine 10 with the low pressure shaft 2. In addition, the arrangement of this connection device 25 and the actuator 40 can be tested at any time and preferably before each flight to guarantee the availability of the disconnection function in the event of a malfunction in full flight. The displacement capacity of at least the actuator 40 is checked, which also implies the operating capacity of the connecting rod 58, the carriages 34, 50 and / or the bearings. The system is then considered to be automatic.

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) which is supported by a stator (4) of the turbomachine via a rear bearing (6), - an electric machine (10), located at the rear of the turbomachine, comprising an electric machine stator (16) fixed to the stator (4) of the turbomachine and an electric machine rotor (17) capable of being driven in rotation by the low-pressure shaft (2), - a connection device (25) configured so as to connect or disconnect in rotation the rotor from the low-pressure shaft (2), and - at least one actuator (40) fixed to the stator (4) of the turbomachine and capable of acting on the connection device (25),characterized in that the connection device (25) comprises a first carriage (34) which carries first teeth (32) intended to mesh with second teeth (33) carried by the low pressure shaft (2) and which is able to move along the longitudinal axis (X) between a coupling position and a decoupling position, and a second carriage (54) which is connected to a movable body (42) of the actuator (40) and which is integral in movement with the first carriage (34), at least one bearing (51) being arranged between the first carriage (34) and the second carriage (54).,

2. Turbomachine (1) according to the preceding claim, characterized in that the bearing (51) comprises an inner ring (52a) which is secured to the first carriage (34), an outer ring (52b) which is secured to the second carriage (50) and rolling members (52c) installed between the inner and outer rings.

3. Turbomachine (1) according to the preceding claim, characterized in that the first carriage (34) carries external splines (36) intended to engage with internal splines (37) of a rotor shaft (29) of the electric machine (10) so as to move relative to the rotor shaft (29).

4. Turbomachine (1) according to one of the preceding claims, characterized in that the actuator (40) comprises a fixed body (41) and the movable body (42) is mounted movable relative to the fixed body (41), the movable body (42) being connected to the second carriage (54) by at least one connecting rod (57).

5. Turbomachine (1) according to the preceding claim, characterized in that the movable body (42) moves along an axis (A) offset or transverse to the longitudinal axis (X).

6. Turbomachine (1) according to one of the preceding claims, characterized in that it comprises at least one elastic return element (48) configured so as to exert a force on the movable body (42) so as to separate the electric machine rotor (17) from the low pressure shaft.

7. Turbomachine (1) according to one of claims 1 to 5, characterized in that it comprises at least one elastic return element (48) configured so as to exert a force on the movable body (42) so as to maintain the connection of the electric machine rotor (17) with the low pressure shaft.

8. Turbomachine (1) according to one of the preceding claims, characterized in that the actuator (40) is connected to an electronic unit (60) which is configured to check the operation of the connection device (25) at least at each start-up of the turbomachine by successively securing and detaching the electric machine rotor (17) from the low pressure shaft (2).

9. Turbomachine (1) according to one of the preceding claims, characterized in that the actuator (40) is connected to an electronic unit (60) which is configured so as to detach the electric machine rotor (17) via the actuator (40) according to a predetermined parameter or a predetermined action.

10. Method for controlling a connection device (25) of a turbomachine (1) according to any one of claims 1 to 9, characterized in that the method comprises at least one step of verifying the operation of the connection device (25) at each start-up of the turbomachine in which the electronic control unit (60) sends a control order to the actuator (40) to successively secure and detach the electric machine rotor (17) from the low pressure shaft (2).

11. Method according to claim 10, characterized in that it comprises a step of detaching the electric machine rotor (17) in which the electronic control unit (60) sends a control order to the actuator (40) to detach the first carriage (34) according to a predetermined parameter or a predetermined action.

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