Aircraft propulsion assembly comprising a propulsion power transmission system with the capacity to decouple two rotating elements actuated from the inside of one of the rotating elements

Abstract

A system (2) for the transmission of propulsion power of a propulsion assembly (1) for an aircraft comprises means (12) for coupling a first rotating element (4) with a second rotating element (8), and an actuator (10) for moving the second rotating element (8) axially between a coupling position in which the coupling means (12) are engaged with one another, and a disengaging position in which the coupling means (12) are disengaged from one another. The actuator (10) comprises an actuating member (40) extending in a bore (8A) of the second rotating element (8) and cooperating with a drive device (42). A rolling bearing (44) is interposed between the actuating member (40) and an inner surface (8B) of the second rotating element (8) so as to secure the actuating member (40) and the second rotating element (8) to one another axially while allowing the second rotating element (8) to rotate freely relative to the actuating member (40). The rotor is kinematically connected to the rotor of an electric machine configured to receive propulsion power from the first rotating element (4).

Description

[0001] DESCRIPTION

[0002] TITLE: AIRCRAFT PROPULSION ASSEMBLY COMPRISING A PROPULSION POWER TRANSMISSION SYSTEM CAPABLE OF DECOUPLING TWO ROTATING ELEMENTS, OPERATED FROM INSIDE ONE OF THE ROTATING ELEMENTS

[0003] Technical field

[0004] The present invention relates to the field of aircraft propulsion systems and more particularly concerns a transmission system capable of decoupling two rotating elements.

[0005] Such transmission systems are intended in particular to enable efficient torque transmission between a turbomachine and an electric machine, while allowing decoupling between them in the event of failure, or to prevent failure of the electric motor, or of the equipment, components or systems related to the latter, without requiring the complete shutdown of the turbomachine.

[0006] Aircraft main propulsion engines generally drive non-propulsive electrical power generating machines at a moderate speed, typically of the order of a few thousand revolutions per minute. These electrical machines are sometimes subject to failures, particularly of mechanical origin, with relatively high prevalence rates compared to the reliability required for main engines. One way to continue using the propulsion engine is then to mechanically disconnect the electrical machine from the turbomachine.

[0007] With the development of hybrid thermal / electric propulsion systems, it is desirable to develop reliable, lightweight, inexpensive, and easily integrated mechanical decoupling systems, which are also adapted to the specificities of such systems.

[0008] Indeed, in propulsion systems comprising a turbogenerator intended to generate propulsive electrical energy, the electrical machines have a power of an order of magnitude comparable to the power of the turbomachine (this nevertheless depending on the number of electrical machines driven by the turbomachine), whereas the non-propulsive electrical machine of a conventional propulsion system is relatively "small" compared to the thermal engine.

[0009] Furthermore, the mechanical power received by an electric machine within such a propulsion unit is considerably greater than that received by a non-propulsion electric machine from a conventional propulsion unit.

[0010] Furthermore, the mass of such a machine is not negligible compared to that of the complete propulsion system, which results in a strong interest in optimizing this mass by the use of high-speed electric machines (of the order of several tens of thousands of revolutions per minute) and / or by the use of permanent magnet machines, also called "PMG" from the English terminology "Permanent Magnet Generators", which have a high power mass density, but for which short-circuit cases cannot be treated simply by de-energizing the rotor.

[0011] Furthermore, transmission systems with decoupling capability also find application within "parallel" hybrid propulsion systems, where power can be selectively supplied by a thermal engine and / or by an electric motor to a receiver such as a propeller. When it is desired to use reversible electric machines, in particular to be able to perform functions such as recharging power batteries, it is then interesting or even necessary to also have decoupling mechanisms between the electric motor-generator and the receiver.

[0012] Climate change is a major concern for many legislative and regulatory bodies around the world. Various states have, are, or will adopt various carbon emission restrictions. In particular, an ambitious standard applies to both new aircraft types and those currently in operation, requiring the implementation of technological solutions to comply with current regulations. For several years now, civil aviation has been mobilizing to contribute to the fight against climate change.

[0013] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. All stakeholders in the sector are constantly working to improve energy efficiency. The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental impacts with the aim of improving the energy efficiency of air transport.

[0014] Consequently, the Applicant is constantly working to reduce its climate impact by using methods and operating virtuous development and manufacturing processes and minimizing greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0015] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to ensure propulsion, and, as an essential complement to technological progress, aeronautical biofuels.

[0016] To this end, the invention is the result of technological research aimed at significantly improving the performance of aircraft and, in this sense, contributes to reducing their environmental impact.

[0017] State of the prior art

[0018] A wide variety of disengageable coupling devices between two rotating elements, generally shafts, are known. These devices essentially consist of: - ramp devices, in which an actuator acts radially on a ramp secured to one of the rotating elements so as to cause an axial displacement of the rotating element causing decoupling between the latter and the other rotating element;

[0019] - screw devices, which operate on a principle similar to the previous one, the ramp being replaced by a thread and the actuator being shaped to act on the thread and cause axial movement of the rotating element in the manner of a screw-nut effect;

[0020] - ball devices, in which the connection between the rotating elements is achieved by means of balls capable of being disengaged from their housing to effect decoupling;

[0021] - freewheel devices that can be disengaged on command;

[0022] - devices with actuated frangible section, in which the rupture of a section is caused by contact with a friction member controlled for this purpose;

[0023] - devices with a section that can be broken by thermal fusion; and

[0024] - axial piston devices, in which a piston is moved axially to cause one of the rotating elements to mechanically decouple from the other rotating element.

[0025] The implementation of ramp and screw devices presents a risk of jerks that can limit their ability to operate at high speeds, and these devices generally present a risk of premature wear. In addition, the radial size of the actuator of such devices is sometimes unacceptable.

[0026] Ball devices are generally characterized by irreversible operation, preventing any possibility of resetting.

[0027] Frangible section devices are destructive and therefore risk damaging nearby components. In addition, these devices cannot be tested.

[0028] Document EP3746669A1 provides an example of a device of the latter type, i.e. with axial piston, in which an annular hydraulic actuator is arranged around an intermediate pinion itself interposed axially between two shafts to be connected. The hydraulic actuator is configured to axially move the intermediate pinion so as to mechanically decouple the latter from one of the shafts, under the effect of fluid pressure.

[0029] However, such a device is cumbersome and expensive due to the relatively large number of moving parts involved in its operation.

[0030] There is therefore a need for transmission systems with decoupling capacity that are of limited mass and size.

[0031] There is also a need for transmission systems with decoupling capacity which are as suitable as possible for coupling rotating elements intended for the transmission of propulsive power (typically having to transmit power levels of the order of several hundred kilowatts) and / or elements rotating at high speeds (typically of the order of several tens of thousands of revolutions per minute), and / or which are suitable for power transmission in both directions of rotation. This latter property is particularly used in the case of electrical machines for generating propulsive power which also act as starters for turbomachines.

[0032] Finally, there is a need for transmission systems with decoupling capacity that have a reversible operating mode allowing them to be reset.

[0033] Statement of the invention

[0034] The invention aims to at least partially address these needs.

[0035] To this end, it offers a transmission system with decoupling capacity for aircraft propulsion systems, comprising:

[0036] - a first rotating element;

[0037] - a second rotating element mounted to rotate along an axis relative to a stator;

[0038] - coupling means configured to mechanically couple the first rotating element with the second rotating element when said coupling means are engaged, and to be disengaged under the effect of a movement of the second rotating element along the axis; and - an actuator for axially moving the second rotating element, on command, between a coupling position in which the coupling means are engaged, and a disengaging position in which the coupling means are disengaged; wherein:

[0039] - the actuator comprises an actuating member extending at least partially into a bore of the second rotating element and cooperating with a motor device configured to axially move the actuating member;

[0040] - a rolling bearing is interposed between the actuating member and an internal surface of the second rotating element so as to axially secure the actuating member and the second rotating element while allowing free rotation of the second rotating element relative to the actuating member.

[0041] The invention thus proposes a transmission system with decoupling capacity, offering advantages in terms of limitation of size and mass, and suitable for the applications mentioned above.

[0042] In embodiments, the actuator is an electromechanical actuator.

[0043] Thus, the actuator can advantageously be a solenoid linear actuator.

[0044] In other embodiments, the actuator is a single-acting or double-acting cylinder.

[0045] In embodiments, the actuating member includes a channel for circulating a lubricating fluid into the bore of the second rotating element.

[0046] In such embodiments, the second rotating element advantageously comprises orifices connecting the bore thereof with at least one lubrication chamber formed on an external surface of the second rotating element.

[0047] In embodiments, the transmission system includes a spring that axially biases the actuating member in a direction from the disengaged position to the coupled position. In embodiments, the first rotating member is a shaft, and the second rotating member is a coupling sleeve or a coupling pinion, coaxial with the shaft.

[0048] The invention also relates to a propulsion assembly for an aircraft, comprising a receiver, an electric machine, a turbomachine and a transmission system of the type described above, in which the first rotating element of the transmission system is kinematically connected to a rotor of the electric machine while the second rotating element of the transmission system is kinematically connected to a rotor of the turbomachine, and in which at least one of the electric machine and the turbomachine is configured to transmit propulsive power to the receiver.

[0049] In embodiments, the first rotating element is a shaft, the second rotating element is a coupling sleeve coupled to a coupling pinion so as to be rotationally integral with the latter but so that the coupling sleeve is free to move axially relative to the coupling pinion, and in which the coupling sleeve is kinematically connected to the rotor of the turbomachine via the coupling pinion.

[0050] In embodiments, the electric machine is configured to receive propulsive power from the first rotating element.

[0051] Brief description of the drawings

[0052] The invention will be better understood, and other details, advantages and characteristics thereof will appear on reading the following description given by way of non-limiting example and with reference to the appended drawings in which:

[0053] [Fig. 1] is a schematic axial sectional view of an aircraft propulsion assembly comprising an electric machine, a turbomachine and a transmission system with decoupling capability;

[0054] [Fig. 2] is a schematic axial sectional view of a transmission system with decoupling capability according to a first embodiment of the invention which may be part of the propulsion assembly of Figure 1, shown in a coupled configuration; [Fig. 3] is a view similar to Figure 2, in which the transmission system is shown in a decoupling configuration;

[0055] [Fig. 4] is a view similar to Fig. 2, illustrating a transmission system with decoupling capability according to a second embodiment of the invention, which may also be part of the propulsion assembly of Fig. 1, shown in a coupled configuration;

[0056] [Fig. 5] is a view similar to Fig. 4, in which the transmission system is shown in a decoupled configuration;

[0057] [Fig. 6] is a view similar to Fig. 4, illustrating a variation of the second embodiment;

[0058] [Fig. 7] is a view similar to Fig. 4, illustrating another variation of the second embodiment;

[0059] [Fig. 8] is a view similar to Figure 2, illustrating a decoupling capable transmission system according to a third embodiment of the invention, which may also be part of the propulsion assembly of Figure 1, shown in a decoupling configuration.

[0060] Throughout these figures, like references may designate identical or similar elements.

[0061] Detailed disclosure of preferred embodiments

[0062] Figure 1 very schematically illustrates a propulsion assembly 1 for an aircraft, comprising a transmission system 2 with decoupling capacity according to a first embodiment of the invention.

[0063] This transmission system 2 generally comprises a shaft 4, a coupling pinion 6, a coupling sleeve 8 and an actuator 10.

[0064] The transmission system 2, visible in more detail in Figures 2 and 3, is configured to allow a disengageable coupling between the shaft 4 and the coupling pinion 6 by means of the coupling sleeve 8. For this purpose, disengageable coupling means 12 are provided for mechanically coupling the shaft 4 with the coupling sleeve 8, as will become more clearly apparent in the following. The shaft 4 is rotatably mounted relative to a stator 16, for example by means of one or more guide bearings 18 (one of which is visible in Figures 2-6), on a first side C1 of the transmission system. The coupling pinion 6 is rotatably mounted about an axis 14 relative to the stator 16, typically by means of one or more - for example two - guide bearings 20A, 20B, on a second side C2 of the transmission system.The coupling sleeve 8 is mounted in the coupling pinion 6, or, alternatively, on the latter, so as to be integral in rotation with the latter and to have the ability to slide axially relative to the latter, as will become more clearly apparent in the following. The axis 14 therefore also constitutes an axis of rotation for the coupling sleeve 8. Furthermore, the axis 14 advantageously constitutes the axis of rotation of the shaft 4. The axis 14 defines an “axial” direction according to the terminology used in the present description.

[0065] The shaft 4 constitutes an example of a first rotating element, while the coupling sleeve 8 constitutes an example of a second rotating element, according to the terminology used in the most general definition of the invention.

[0066] In embodiments, the shaft 4, or more generally the first rotating element, is kinematically connected to an electric machine rotor, and the coupling sleeve 8, or more generally the second rotating element, is kinematically connected to a turbomachine rotor. By “kinematically connected” elements, it is generally understood in the context of the present description that the elements considered are integral in rotation or form a gear (i.e. are engaged with each other), or form a gear train by being mechanically connected by means of one or more pinions.

[0067] In the illustrated example, the shaft 4 is for example integral with the rotor 22 of an electric machine 24 (figure 1), while the coupling pinion 6 is engaged with a return pinion 26 (visible in full in figure 1 and in part in figures 2-8), the latter being moreover engaged with a rotor 28 of a turbine 29 of a turbomachine 30 (figure 1). The return pinion 26 thus ensures a transmission of rotational movement between the coupling pinion 6 and the rotor 28 of the turbine 29. In view of the above, it will be understood that the shaft 4 can, in other examples, be in direct or indirect mechanical engagement with the rotor 22 of the electric machine 24, that is to say form a gear or a gear train with the latter.

[0068] Furthermore, the illustrated propulsion assembly 1 further comprises a receiver 32, such as a propeller or a fan, the drive of which relies on energy supplied by at least one of the electric machine 24 and the turbomachine 30 (where appropriate, by the rotor 28 of the turbine 29), to ensure the propulsion of an aircraft. The energy supplied by the electric machine 24 may be electrical or mechanical energy, depending on the type of architecture of the propulsion assembly and depending on the role played by the electric machine within this propulsion assembly.

[0069] The transmission system 2 is in particular intended to be part of a mechanical propulsion power transmission system within a hybrid aircraft propulsion assembly.

[0070] The propulsion unit 1 is for example a series hybrid propulsion unit, in which the receiver 32 is mechanically engaged with an electric motor 33 supplied with electrical energy by a distribution unit 34, itself supplied with electrical energy in parallel by a power battery 35, on the one hand, and by the electric machine 24 on the other hand. The latter is thus configured to operate as a generator of propulsive electrical energy by converting mechanical energy received from the turbomachine 30 and supplying the resulting electrical energy to the distribution unit 34. The latter typically comprises DC / AC and AC / DC conversion means. The distribution unit 34 thus also makes it possible to recharge the power battery 35 with surplus electrical power in certain operating phases.In such a case, a transmission system with decoupling capacity similar to the transmission system 2, which will be described in detail below, can, alternatively or in addition, provide a disengageable mechanical coupling between a shaft of the receiver 32 and the rotor of the electric motor 33.

[0071] In other examples, the propulsion assembly 1 may be of the parallel hybrid type, that is to say comprising a transmission system, for example of the type comprising a gear train reducer, configured to mechanically couple to the receiver the electric machine, operating selectively as a motor or generator, and the turbomachine, in parallel. In this case, the electric machine is supplied with electrical energy by a power battery when it operates as a motor and recharges said battery when it operates as a generator driven by the turbomachine, via the mechanical transmission system.

[0072] In order to allow a disengageable coupling between the shaft 4 and the coupling sleeve 8 and thus indirectly allow a disengageable coupling between the shaft 4 and the coupling pinion 6, the coupling means 12 are configured to couple the shaft 4 with the coupling sleeve 8 when these coupling means 12 are engaged, and to be disengaged under the effect of a movement of the coupling sleeve 8 along the axis 14.

[0073] The actuator 10 is configured to axially move the coupling sleeve 8, on command, between a coupling position, for example located on the first side C1, in which the coupling means 12 are engaged, and a disengaging position, for example located on the second side C2, in which the coupling means 12 are disengaged. The control of the actuator 10 is for example triggered by a control unit 36 ​​receiving signals representative of the state of the propulsion assembly emanating from one or more sensors provided for this purpose.

[0074] To allow axial movement of the coupling sleeve 8, the actuator 10 generally comprises an actuating member 40, at least one part of which extends into a bore 8A of the coupling sleeve 8 from one end of the latter, for example located on the second side C2, or more generally on the side opposite the side where the coupling means 12 are arranged.

[0075] This actuating member 40 cooperates with a motor device 42 configured to axially move the actuating member 40, if necessary under the effect of an order received for this purpose from the aforementioned control unit 36.

[0076] Furthermore, a rolling bearing 44 is interposed between the aforementioned part of the actuating member 40 and an internal surface 8B of the coupling sleeve 8 so as to axially secure the actuating member 40 and the coupling sleeve 8 while allowing free rotation of the coupling sleeve 8 relative to the actuating member 40. Different examples of configurations of the actuator 10 and the coupling means 12 will be described below through the presentation of several embodiments of the invention.

[0077] In the first embodiment illustrated in Figures 2 and 3, in which the coupling sleeve 8 is respectively in the coupling position and in the disengaged position, the actuator 10 is an electromechanical actuator, in particular a solenoid linear actuator. It should be understood by this that the motor device 42 of the actuator comprises a solenoid 50 electrically controlled by the control unit 36, and that this solenoid 50 is fixedly housed in a housing 52 secured to a stator structure 16A (forming part of the stator 16) and that it delimits a central space 54 within which an end portion 56B of an actuating rod 56 extends. This actuating rod 56 constitutes a part of the actuating member 40.

[0078] The end portion 56B of the rod 56 thus constitutes the part of the actuating member 40 which cooperates with the motor device 42. In addition, an end portion 56A of the rod 56, on the opposite side, constitutes the part of the actuating member 40 in contact or cooperating with the rolling bearing 44, as will appear more clearly in the following. The stator structure 16A, arranged axially between the housing 52 and the coupling sleeve 8, comprises for example a through passage through which a middle portion 56C of the actuating rod 56 extends.

[0079] The actuating member 40 further comprises a support sleeve 60 integral in translation with the actuating rod 56 and forming a seat 62 for one end of a preload spring 64, the opposite end of which bears against the stator structure 16A, so that the preload spring 64 axially urges the actuating rod 56 in the direction of the first side C1. The support sleeve 60 may be integral with the actuating rod 56 or, as in the example illustrated, be mounted on the latter.

[0080] The rolling bearing 44 is for example held axially in position relative to the coupling sleeve 8 by being sandwiched between a shoulder 66 formed in the bore 8A of the coupling sleeve 8, on the first side C1 relative to the bearing 44, and a nut 68 screwed into a thread formed on the internal surface 8B of the coupling sleeve 8, on the second side C2 relative to the bearing 44.

[0081] Similarly, the rolling bearing 44 is for example held axially in position relative to the actuating rod 56 by being sandwiched between a shoulder 70 of the rod 56, located on the first side C1, and the support sleeve 60, located on the second side C2, relative to the bearing 44.

[0082] The installation of the rolling bearing 44 can thus comprise bringing the bearing 44 to its final position around the actuating rod 56 in the bore 8A from the opening of the latter located on the second side C2, then screwing the nut 68 into the coupling sleeve 8 until an outer ring of the bearing 44 is adequately tightened against the shoulder 66, and finally installing the support sleeve 60 around the actuating rod 56 so that the latter is able to hold an inner ring of the bearing 44 against the shoulder 70.

[0083] Furthermore, in the example illustrated in Figures 2 and 3, the coupling means 12 comprise first coupling splines 12A extending radially inwards from an internal surface 4B delimiting a bore 4A of the shaft 4, and second coupling splines 12B extending radially outwards from an external surface 8C of a first part 8D of the coupling sleeve 8, for example located on the first side C1. The first and second coupling splines 12A, 12B have conjugate configurations to allow the coupling sleeve 8 and the shaft 4 to be secured in rotation.

[0084] In the coupling position (figure 2), the first part 8D of the coupling sleeve 8 is engaged in the bore 4A of the shaft 4 such that the first coupling splines 12A are engaged with the second coupling splines 12B and the shaft 4 and the coupling sleeve 8 are thus rotationally integral.

[0085] In the disengaged position (Figure 3), the coupling sleeve 8 is axially offset towards the second side C2, relative to the coupling position, so that the first coupling splines 12A are not engaged with the second coupling splines 12B and the shaft 4 and the coupling sleeve 8 are thus free to rotate relative to each other.

[0086] In the illustrated example, the shaft 4 and the first part 8D of the coupling sleeve 8 are configured to define between them a first lubrication chamber 72 intended to allow the lubrication of the coupling means 12, in the coupling position (figure 2).

[0087] The sealing of the first lubrication chamber 72 is for example ensured by means of a compressible annular seal 74 housed in a corresponding groove, arranged at a location axially situated on the second side C2 relative to the first splines 12A in the coupling position (figure 2), and formed in the coupling sleeve 8 (or alternatively in the shaft 4), so that the seal 74 is compressed between the shaft 4 and the coupling sleeve 8.

[0088] The first lubrication chamber 72 communicates with the bore 8A of the coupling sleeve 8, for example via first through-orifices 78 formed through the coupling sleeve 8, to allow the first lubrication chamber 72 to be supplied with a lubricating fluid, such as oil, from the bore 8A. For this purpose, the bore 8A is for example closed on the first side C1 by an end wall 8G of the coupling sleeve 8, and on the second side C2, by the bearing 44 and the actuating member 40. In addition, the bore 8A is itself supplied with lubricating fluid by a supply device provided for this purpose.This device comprises, for example, in particular a conduit 80 formed in the stator structure 16A and having an inlet intended to be supplied with lubricating fluid LBF, and an outlet opening into the through passage delimited by the stator structure 16A, more precisely into an annular chamber 82 formed around the actuating rod 56 and defined axially between two compressible annular seals 84A, 84B. The supply device further comprises a channel 86 formed in the actuating rod 56, for example in the center thereof, and one or more orifices 88 formed in the actuating rod 56 so as to put the channel 86 in communication with the aforementioned annular chamber 82, whatever the axial position of the rod 56, from the position corresponding to the coupling position of the coupling sleeve 8 to the position corresponding to the disengagement position of the coupling sleeve 8.The channel 86 opens into the bore 8A of the coupling sleeve 8 through a free end of the end portion 56B of the actuating rod 56, whereby the channel 86 makes it possible to inject the lubricating fluid LBF from the conduit 80 into the bore 8A.

[0089] Furthermore, in the illustrated example, the coupling pinion 6 (or at least a portion thereof) is arranged around a second portion 8E of the coupling sleeve 8, located on the second side C2 relative to the first portion 8D thereof. To allow the coupling pinion 6 to be rotationally integral with the coupling sleeve 8 but for the coupling sleeve 8 to be free to move axially relative to the coupling pinion 6, the coupling pinion 6 is for example provided with internal splines 92A formed on an internal surface 6B thereof and engaged with external splines 92B formed on an external surface 8F of the second portion 8E of the coupling sleeve 8. These splines 92A, 92B are dimensioned to remain engaged regardless of the axial position of the coupling sleeve 8 from its coupling position to its disengagement position.In addition, the coupling pinion 6 is for example provided, on its external surface 6C, with external teeth 94 engaging with the return pinion 26.

[0090] The second part 8E of the coupling sleeve 8 and the coupling pinion 6 are for example configured to define between them a second lubrication chamber 96 intended to ensure the lubrication of the splines 92A, 92B.

[0091] For this purpose, the coupling sleeve 8 comprises for example a structure 98, such as a collar, formed to project outwards from the external surface 8F of the second part 8E of the coupling sleeve 8, so as to come at a short distance from the internal surface 6B of the coupling pinion 6, beyond the splines 92A, 92B in the direction of the second side C2. In addition, the coupling pinion 6 comprises for example a structure 100, such as a shoulder formed to project inwards from the internal surface 6B of this pinion, so as to come at a short distance from the external surface 8F of the sleeve, beyond the splines 92A, 92B in the direction of the first side C1. The structures 98 and 100 thus axially delimit between them the second lubrication chamber 96.The sealing of the second lubrication chamber 96 is for example ensured by means of compressible annular seals 102 and 104 respectively compressed between the collar 98 and the coupling pinion 6, and between the external surface 8F of the coupling sleeve 8 and the coupling pinion 6 at a location situated beyond the shoulder 100 in the direction of the first side C1.

[0092] The second lubrication chamber 96 communicates with the bore 8A of the coupling sleeve 8, for example via second through orifices 106 formed through the coupling sleeve 8, to allow the second lubrication chamber 96 to be supplied with lubricating fluid, from the bore 8A.

[0093] In operation, the coupling sleeve 8 being initially in the coupling position (figure 2), the lubricating fluid LBF injected through the channel 86 into the bore 8A supplies the two lubrication chambers 72 and 96.

[0094] Furthermore, the preload spring 64 axially biases the actuating rod 56 towards the first side C1 and thus contributes to maintaining the coupling sleeve 8 in the coupling position.

[0095] When decoupling of the shaft 4 and the coupling pinion 6 is required, the control unit 36 ​​induces the solenoid 50 to move the actuating rod 56 towards the second side C2, driving the coupling sleeve 8 with it into the disengaging position, so that the coupling splines 12A, 12B are no longer engaged with each other. The coupling sleeve 8 is thus decoupled from the shaft 4, whereby the shaft 4 and the coupling pinion 6 are decoupled.

[0096] In some embodiments, synchronization means (not described here) allow the shaft 4 and the coupling sleeve 8 to be brought into unison and angular coincidence in order to allow them to be re-coupled. To implement such re-coupling, the control unit 36 ​​then induces the solenoid 50 to move the actuating rod 56 towards the first side C1, driving with it the coupling sleeve 8 into the coupling position, so that the coupling splines 12A, 12B are engaged with each other. The coupling sleeve 8 is thus re-coupled to the shaft 4, whereby the shaft 4 and the coupling pinion 6 are re-coupled.

[0097] Figures 4 and 5 illustrate a second embodiment of the invention, in which there is no coupling sleeve, the role of second rotating element, within the meaning of the most general definition of the invention, being played here by the coupling pinion 6.

[0098] Incidentally, the actuator 10 in this second embodiment is a single-acting hydraulic or pneumatic cylinder.

[0099] In addition, the coupling means 12 are dogs 12C, 12D formed respectively on the shaft 4 and on the coupling pinion 6.

[0100] More specifically, the actuator 10 comprises a cylinder body 110 secured to the stator 16 and delimiting a cylinder chamber 112 into which a conduit 114 suitable for fluid circulation opens. This conduit is for example connected to a pump 116 capable of generating a depression of the fluid in the conduit 114, and therefore, in the cylinder chamber 112. The pump 116, and / or a valve 117 provided on the conduit 114, is operationally connected to the control unit 36 ​​to be controlled by the latter and thus allow the actuator 10 to be controlled.

[0101] On the first side C1, or more generally on the side of the coupling position, the cylinder chamber 112 is delimited by a piston 120 axially movable and rigidly connected to an actuating rod 122 extending beyond the piston 120 in the direction of the first side C1 into the bore 6A of the coupling pinion 6. The piston 120 is for example provided, on its periphery, with a compressible seal 123 in contact with the inner surface of the cylinder body 110 to ensure the sealing of the cylinder chamber 112.

[0102] The actuating rod 122 is connected to the coupling pinion 6 by the rolling bearing 44, in a manner analogous to that described above in relation to the first embodiment. In the terminology of the invention, the actuating rod 122 constitutes an example of an actuating member 40 of the actuator 10, while the cylinder body 110, the piston 120, the conduit 114 and the pump 116 form an example of a motor device 42 of the actuator 10. A spring 64 is further compressed between the piston 120 and a bottom of the cylinder chamber 112 so as to bias the piston 120, and thus the actuating rod 122, towards the first side C1.

[0103] The rolling bearing 44 is for example held axially in position relative to the coupling pinion 6 in a manner analogous to that described above in relation to the first embodiment.

[0104] In addition, the rolling bearing 44 is for example held axially in position relative to the actuating rod 122 by being sandwiched between a shoulder 124 of the rod 122, located on the second side C2 relative to the bearing 44, and a nut 126, located on the first side C1 relative to the bearing 44. The rod 122 can thus be assembled to the bearing 44 by inserting the rod 122 through the inner ring of the bearing 44, towards the first side C1, then mounting the nut 126 on the rod from the first side C1.

[0105] The coupling pinion 6 further comprises external teeth 130 formed on the external surface 6C of the latter and by which this coupling pinion is engaged with the idler pinion 26. These external teeth 130 and the corresponding teeth of the idler pinion 26 are straight teeth so that the relative axial displacement between the coupling pinion 6 and the idler pinion 26 is possible without inducing any significant axial force on these elements. In addition, the external teeth 130 have an axial extent such that the coupling pinion 6 remains engaged with the idler pinion 26 regardless of the axial position of the coupling pinion 6, from the coupling position (figure 4) to the disengaged position (figure 5).

[0106] At its end located on the second side C2, the shaft 4 comprises the dogs 12C which, in the coupled configuration of figure 4, are engaged with the dogs 12D formed at the end of the coupling pinion 6 located on the first side Cl.

[0107] In operation, the spring 64 tends to hold the coupling pinion 6 in the coupling position (figure 4).

[0108] A decoupling of the shaft 4 and the coupling pinion 6 is implemented by generating a vacuum in the cylinder chamber 112 by means of the pump 116, to the point that the resulting force exceeds that induced by the spring 64, so as to move the actuating rod 122 towards the second side C2. Thus, the rod drives the coupling pinion 6 with it into the disengaged position, so that the dogs 12C, 12D are no longer engaged with each other. The shaft 4 and the coupling pinion 6 are thus decoupled.

[0109] Figure 6 illustrates a variant, similar to the embodiment of Figures 4 and 5, but in which the actuator 10 is a double-acting hydraulic or pneumatic cylinder.

[0110] Thus, the cylinder body 110 delimits two cylinder chambers 112 and 113 into which respectively open conduits 114 and 115 configured to be selectively supplied with pressurized fluid, and thus selectively increase the pressure in one or other of the cylinder chambers 112 and 113 and thus cause the displacement of the actuating rod 122 in the direction of the first side C1 or the second side C2.

[0111] For this purpose, the conduits 114 and 115 are for example connected, via an appropriate distributor 117, to a circuit in which the circulation of a pressurized fluid, for example a lubricant, is driven by means of a pump 116. Thus, the pump 116 is not necessarily dedicated specifically to controlling the cylinder but may be the pump of a lubrication circuit of the turbomachine.

[0112] In this case, the spring 64 fulfills a preloading function, that is to say it helps to maintain the coupling pinion 6 in the coupling position, in particular when the fluid pressure in the chamber 112 is insufficient on its own to achieve this. This is particularly advantageous at low speed in embodiments where the power of the pump 116 depends on the operating speed of the turbomachine.

[0113] The conduit 114 and the pump 116 are for example part of a lubrication circuit of the turbomachine, in which case the fluid considered is a lubricating fluid such as oil.

[0114] Incidentally, in the example illustrated in Figure 6, the actuating member 40 is provided with a nut 132 mounted on the end 122A of the actuating rod 122 located on the first side C1 and on which the rolling bearing 44 is mounted in a manner analogous to that described above. This configuration of the actuating member 40 in this case makes it easier to assemble the assembly composed of the actuator 10, the coupling pinion 6 and the rolling bearing 44.

[0115] Furthermore, the cylinder body 110 has, for example, an end forming a stop 133 against one end of the nut 132 and thus limiting the travel of the actuating member 40 towards the second side C2, and thus defining the disengagement position.

[0116] Figure 7 illustrates another variant in which the actuator 10 is still a single-acting hydraulic or pneumatic cylinder, but configured so that a pressure of the fluid in its chamber 113 acts against the force induced by the spring 64.

[0117] For this purpose, the single chamber 113 receiving fluid is for example defined on the other side of the piston 120 relative to the chamber 112 housing the spring 64, the latter still functioning as a compression spring. The chamber is not connected to a fluid supply but is provided with a vent 134. In addition, the pump 116 is here configured to supply the chamber 113 with pressurized fluid. Thus, the spring 64 here again tends to maintain the coupling pinion 6 in the coupling position, while an injection of pressurized fluid into the chamber 113 makes it possible, when the force applied by the fluid to the piston 120 exceeds that induced by the spring 64, to move the actuating rod 122 towards the second side C2, in a manner analogous to that explained above in relation to FIG. 6.The injection of pressurized fluid into the chamber 113 can be carried out by the pump 116 and / or by opening a valve 117 provided on the conduit 114 in order to connect the conduit 114 with a pressurized fluid circuit, such as a lubrication circuit of the turbomachine, as explained above.

[0118] Of course, other embodiments are still possible without departing from the scope of the invention.

[0119] For example, dog-type coupling means, such as those of Figures 4 and 5, may be used in the embodiment of Figures 2 and 3 instead of the coupling splines 12A, 12B. Furthermore, the coupling sleeve 8 or the coupling pinion 6 may be formed of sections connected by ball-and-socket articulation means, for example domed splines, so as to increase an admissible level of misalignment between the shaft 4 and the actuating member 40.

[0120] Furthermore, the coupling means 12 may, in other embodiments, be arranged to ensure a disengageable coupling between the coupling pinion 6 and the return pinion 26. In other words, according to the terminology used in the most general definition of the invention, the role of first rotating element is then played by the return pinion 26, while the role of second rotating element is played by the coupling pinion 6.

[0121] Figure 8 illustrates an example of such an embodiment, in which the coupling means 12 consist of outer teeth 12E of the coupling pinion 6 and teeth 12F of the idler pinion 26, arranged to be engaged when the coupling pinion 6 is in a coupling position, and to be disengaged when the coupling pinion 6 is in a disengaged position (as illustrated in Figure 8).

[0122] The coupling between the shaft 4 and the coupling pinion 6 is, in such cases, ensured by coupling means 140, such as straight splines 140A, 140B, configured to remain engaged regardless of the position of the coupling pinion 6. A relative axial displacement between the coupling pinion 6 and the shaft 4 is thus made possible without inducing any significant axial force on these elements.

[0123] In the illustrated example, the first rotating element (in this case the idler pinion 26) is arranged offset relative to the axis 14. More precisely, the idler pinion 26 is mounted to rotate about an axis 17 distinct from the axis 14. In the illustrated example, the axis 17 of the idler pinion 26 is parallel to the axis 14 of the shaft 4 and the coupling pinion 6. Alternatively, the axis 17 of the idler pinion and the axis 14 of the coupling pinion may be intersecting, provided that the coupling means 12 are configured appropriately.

[0124] The example of Figure 8 shows a single-acting cylinder type actuator similar to that of Figures 4 and 5, but such embodiments are of course compatible with other types of actuators, in particular with the electromechanical actuator of Figures 2 and 3 or with a cylinder such as those of Figures 6 and 7.

[0125] In addition, arrangements similar to those described above in relation to Figures 1 and 2 may be provided for the lubrication of the coupling means 140, this being possible regardless of whether the actuator is similar to the electromechanical actuator of Figures 2 and 3 or whether it is a cylinder as in Figures 4-7.

Claims

CLAIMS 1. Propulsion assembly (1) for aircraft, comprising: - a receiver (32); - an electric machine (24); - a turbomachine (30); and - a propulsion power transmission system (2), with decoupling capability; in which at least one of the electric machine (24) and the turbomachine (30) is configured to transmit propulsion power to the receiver (32); in which the transmission system (2) comprises: - a first rotating element (4; 26) kinematically connected to a rotor (22) of the electric machine (24), the electric machine (24) being configured to receive propulsive power from the first rotating element (4); - a second rotating element (8; 6) mounted to rotate along an axis (14) relative to a stator (16) and kinematically connected to a rotor (28) of the turbomachine (30); - coupling means (12) configured to mechanically couple the first rotating element (4; 26) with the second rotating element (8; 6) when said coupling means (12) are engaged, and to be disengaged under the effect of a movement of the second rotating element (8; 6) along the axis (14); and - an actuator (10) for axially moving the second rotating element (8; 6), on command, between a coupling position in which the coupling means (12) are engaged, and a disengaging position in which the coupling means (12) are disengaged; in which: - the actuator (10) comprises an actuating member (40) extending at least partially in a bore (8A; 6A) of the second rotating element (8; 6) and cooperating with a motor device (42) configured to axially move the actuating member (40); - a rolling bearing (44) is interposed between the actuating member (40) and an internal surface (8B; 6B) of the second rotating element (8; 6) so as to secure axially the actuating member (40) and the second rotating element (8; 6) while allowing free rotation of the second rotating element (8; 6) relative to the actuating member (40).

2. Propulsion assembly according to claim 1, in which the actuator (10) is an electromechanical actuator.

3. Propulsion assembly according to claim 2, in which the actuator (10) is a solenoid linear actuator.

4. Propulsion assembly according to claim 1, in which the actuator (10) is a single-acting or double-acting cylinder.

5. Propulsion assembly according to any one of claims 1 to 4, in which the actuating member (40) comprises a channel (86) for circulating a lubricating fluid into the bore (8A) of the second rotating element (8).

6. Propulsion assembly according to claim 5, in which the second rotating element (8) comprises orifices (78, 106) putting the bore (8A) thereof into communication with at least one lubrication chamber (72, 96) formed on an external surface (8C) of the second rotating element (8).

7. Propulsion assembly according to any one of claims 1 to 5. 6, comprising a spring (64) which axially biases the actuating member (40) in a direction going from the disengaged position towards the coupling position.

8. Propulsion assembly according to any one of claims 1 to 10. 7, wherein the first rotating element is a shaft (4), and the second rotating element is a coupling sleeve (8) or a coupling pinion (6), coaxial with the shaft (4).

9. Propulsion assembly according to any one of claims 1 to 10. 7, wherein the first rotating element is a shaft (4), the second rotating element is a coupling sleeve (8) coupled to a coupling pinion (6) so as to be rotationally integral with the latter but so that the coupling sleeve (8) is free to move axially relative to the coupling pinion (6), and wherein the coupling sleeve (8) is kinematically connected to the rotor (28) of the turbomachine (30) via the coupling pinion (6).

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