Assembly comprising a shaft section guided by a flexibly held bearing

Abstract

The invention relates to an aircraft propulsion system assembly (60) comprising a fixed structural element (73) and a shaft (54) rotating about a longitudinal axis (X) relative to the structural assembly, the shaft (54) comprising two flexible coupling members (79) and an intermediate section (76) interposed between the flexible coupling members (79), wherein the assembly (60) further comprises a bearing (92) guiding the intermediate section (76) in rotation relative to the structural element (73), said bearing (92) being connected to the structural element (73) via a flexible linkage device (90). Figure for the abstract: Fig. 3

Description

Title of the invention: Assembly comprising a shaft section guided by a bearing held flexibly Field of the invention

[0001] The present invention relates to mechanical reducers and the management of misalignments between a reducer and the input shaft coupled to the latter. The present invention relates more particularly to propulsion systems for aircraft and the management of misalignments between the turbine shaft and the fan reducer of such a system. Technological background

[0002] New generations of dual-flow turbomachines, particularly those with a high bypass ratio, include a mechanical reducer to drive the shaft of a fan. Usually, the reducer is intended to transform the relatively fast rotation speed of the shaft of a gas turbine rotor into a slower rotation speed for the shaft driving the fan.

[0003] Most often, the reducers used in such turbomachines are epicyclic gear reducers comprising a central pinion, called a sun gear, a crown coaxial with the sun gear, surrounding the latter, and pinions, called satellites, which are engaged between the sun gear and the crown gear and are held by a frame called a planet carrier. Conventionally, the sun gear is rotated by the turbine shaft and the fan shaft is rotated by the planet carrier (when the reducer is in epicyclic configuration) or by the crown gear (when the reducer is in planetary configuration).

[0004] For optimal operation of such a turbomachine, the various elements which are connected by a shaft must be perfectly aligned with each other and with said shaft. Excessive misalignment of a shaft relative to the elements to which it is connected can cause damage to the shaft itself, which may go as far as breaking the latter, or to the elements connected to the shaft which may wear quickly, in particular due to friction. However, since a certain degree of misalignment, which may be horizontal and / or vertical, and axial displacements at the level of a shaft are inevitable, it is known to position one or more flexible coupling devices on the shaft.Thus, it is known to position on the turbine shaft, between the upstream bearing and the reducer, flexible coupling devices intended to prevent misalignment between the upstream bearing and the reducer from causing damage or wear to the shaft, the low pressure turbine and / or the reducer, in particular the solar one.

[0005] These flexible coupling devices must meet opposing constraints. On the one hand, they must be sufficiently flexible so as not to induce excessive overload at the level of the toothing of the solar. On the other hand, they must be sufficiently stiff so as not to enter into resonance in the operating range of the turbomachine.

[0006] However, in order to reduce the consumption of such turbomachines, it is sought to minimize the size of the reducers while maximizing their reduction ratio, which results in a reduction in the load level that can be supported by the solar. Under these conditions, it becomes increasingly difficult to size the flexible coupling devices so that they can satisfy the aforementioned double constraint. Statement of the invention

[0007] An objective of the invention is to enable the coupling of a gas turbine shaft to a reducer, in particular an epicyclic gear train, so as to reduce the loads transmitted to the input pinion while having a resonant frequency which is outside the operating range of the gas turbine.

[0008] To this end, the invention relates to an aircraft propulsion system assembly comprising a fixed structural element and a shaft rotating about a longitudinal axis relative to the structural assembly, the shaft comprising two flexible coupling members and an intermediate section interposed between the flexible coupling members, in which the assembly further comprises a bearing guiding the intermediate section in rotation relative to the structural element, said bearing being connected to the structural element by means of a flexible connecting device.

[0009] The flexible connecting device makes it possible to limit the radial movements of the intermediate section by flexible support of the intermediate section. This makes it possible to compensate for the loss of stiffness resulting from the softening of the flexible coupling members intended for managing misalignments and to reject the resonance frequency of the assembly outside the operating range of the propulsion system in which it is intended to be integrated. Thus, certain elements of the propulsion system assembly are not likely to enter into resonance during the operation of said propulsion system.

[0010] According to particular embodiments of the invention which can be taken alone or in combination: - the flexible connecting device comprises an internal flange secured to the bearing and an external flange secured to the structural element, the internal flange and the external flange being connected to each other by a plurality of flexible members; the flexibility of the flexible connecting device is thus enabled by the flexibility of all the members flexible; - each flexible member is elastically deformable in a radial direction relative to the input shaft; the flexible connecting device is thus radially flexible in a homogeneous manner; in other words, each flexible member is deformable along its axis of elongation; - the flexible members form radii distributed regularly around the internal flange; the flexibility of the flexible connecting device is thus homogeneous in the different radial directions; - the assembly further comprises a reducer coupling the shaft, which constitutes an input shaft of the reducer, to an output shaft, the flexible coupling members comprising a first flexible coupling member connecting the intermediate section to a distal section of the shaft and a second flexible coupling member connecting the intermediate section to the input pinion; - each flexible coupling member is configured to allow longitudinal translations and rotations about axes perpendicular to the longitudinal axis; thus, the input pinion is free to move radially and longitudinally relative to the input shaft, these movements being compensated by the deformation of the flexible coupling members, which limits the loads undergone by the input pinion; - each flexible coupling member is configured to allow only longitudinal translations and rotations around axes perpendicular to the longitudinal axis; thus, the flexible coupling members allow good transmission of torque between the input shaft and the reducer; - each flexible coupling member comprises a first ring connected to the intermediate section, a second ring connected to another element, a crown surrounding the first and second rings, a first flexible annular structure interposed between the first ring and the crown and a second flexible annular structure interposed between the second ring and the crown; each flexible coupling member thus allows relative movements between the intermediate section and the element to which it is attached while limiting the extent of these movements; the first and / or the second annular structure may be a flexible annular membrane making it possible to absorb, by elastic deformations, part of the misalignments and / or displacements of the input pinion relative to the input shaft; - each flexible annular structure is formed from a solid circular metal membrane pierced in its center; thus, each flexible coupling member allows good transmission of torque around the longitudinal axis and has good resistance over time; - the intermediate section forms a main section rotating the input pinion, the second flexible coupling member comprising two flexible coupling elements arranged axially on either side of the input pinion, each flexible coupling element forming a connection between the input pinion and the main section; the second flexible coupling member thus allows the input pinion to move longitudinally relative to the main section, which makes it possible to reduce the loads experienced by the input pinion; and - the assembly comprises a turbine and a fan, the input shaft being driven in rotation by the turbine and the output shaft driving in rotation the fan; - the reducer is an epicyclic gear reducer comprising a sun gear constituting the input pinion, a crown surrounding the sun gear and a plurality of satellites, carried by a planet carrier, meshing with the sun gear and the crown gear, one of the crown gear and the planet carrier being fixed and the output shaft being driven in rotation by the other of the crown gear and the planet carrier.

[0011] The invention also relates to an aircraft comprising a propulsion system assembly as previously described. Brief description of the Figures

[0012] Other characteristics and advantages of the invention will appear on reading the description which follows, given solely by way of example and with reference to the appended drawings, in which:

[0013] [Fig-1] [Fig.l] is a schematic top view of an aircraft according to a mode of realization of the invention;

[0014] [Fig.2] [Fig.2] is a schematic view in partial section of a propulsion system of the aircraft of [Fig.l];

[0015] [Fig.3] [Fig.3] is a schematic view of an assembly of the propulsion system of the [Fig.2] ;

[0016] [Fig.4] [Fig.4] is a schematic view of a reducer of the propulsion system assembly of [Fig.3];

[0017] [Fig.5] [Fig.5] is a schematic view of an assembly of the propulsion system according to a first embodiment; and

[0018] [Fig.6] [Fig.6] is a schematic view of an assembly of the propulsion system according to a second embodiment. Detailed description of an example of realization

[0019] In the example shown, the aircraft 1 is an airplane. This comprises, in a conventional manner, a fuselage 4, a tailplane 6 and two wings 8. The propulsion systems 10 are here two in number and are each housed under a respective wing 8. In a variant (not shown), the propulsion systems 10 are arranged along the fuselage 4, for example example near the empennage 6. As a further variant (also not shown), the aircraft 1 comprises a single propulsion system 10 or at least three propulsion systems 10.

[0020] One of the propulsion systems 10 is shown in [Fig.2].

[0021] In [Fig.2], the propulsion system 1 has a main direction extending along a longitudinal axis X. The propulsion system 1 comprises a fan section 2 and a primary body 3, often called a “gas generator”.

[0022] The fan section 2 comprises a fan 22 and a fan housing 12. The fan 22 comprises a fan rotor 9. The fan housing 12 surrounds the fan rotor 9. The fan rotor 9 is rotatably mounted relative to the fan housing 12.

[0023] The fan rotor 9 comprises a fan hub 13 and fan blades 14 extending radially from the hub 13. The fan blades 14 may be fixed relative to the fan hub 13 or have a variable pitch. In the latter case, each of the fan blades 14 is pivotally mounted relative to the fan hub 13 along a pitch axis and is connected to a pitch change mechanism mounted in the propulsion system 1. The pitch change mechanism makes it possible to adjust the pitch angle of the fan blades 14 according to the flight phases.

[0024] In this example, the fan section 2 also comprises a fan stator 16 fixedly mounted on the fan casing 12. The fan stator 16 comprises fixed vanes 17 generally called “outlet vanes” (or “OGV”, for “Outlet Guide Vane” in English).

[0025] Alternatively, the outlet blades 17 could have a variable pitch. If necessary, and in a similar manner to the fan blades 14 of the fan rotor 9, the root of the outlet blades 17 is pivotally mounted along a pitch axis and is connected to a pitch change mechanism (not shown), the pitch being adjusted according to the flight phases by the pitch change mechanism.

[0026] The primary body 3 comprises a compressor section 18, a combustion chamber 6 and a turbine section 19.

[0027] The compressor section 18 comprises a low pressure compressor 4 and a high pressure compressor 5.

[0028] The turbine section 19 comprises a high pressure turbine 7 and a low pressure turbine 8.

[0029] The propulsion system 1 comprises a low pressure shaft 54 ​​connecting the low pressure turbine 4 to the low pressure compressor 8, the low pressure shaft 54 ​​being rotatably mounted relative to a casing 26 of the primary body 3 around the longitudinal axis X.

[0030] When the propulsion system 1 is in operation, the low pressure turbine 8 drives the low pressure compressor 4 in rotation via the low pressure shaft 54.

[0031] The propulsion system 1 further comprises a high pressure shaft 10 connecting the high pressure turbine 7 to the high pressure compressor 5, the high pressure shaft 10 being rotatably mounted relative to the casing 26 around the longitudinal axis X. The high pressure shaft 10 is coaxial with the low pressure shaft 54 ​​and extends around the low pressure shaft 54.

[0032] When the propulsion system 1 is in operation, the high pressure turbine 7 drives the low pressure compressor 4 in rotation via the low pressure shaft 54.

[0033] When the propulsion system is in operation, an air flow F entering the propulsion system 1 passes through the fan 22 and is then divided between a primary air flow F1 and a secondary air flow F2, which circulate from upstream to downstream in the propulsion system 1.

[0034] The secondary air flow F2, also called “bypass air flow”, flows in a secondary vein, around the primary body 3. The secondary air flow F2 makes it possible to cool the periphery of the primary body 3 and is used to generate the majority of the thrust provided by the propulsion system 1.

[0035] The primary air flow F1 flows in a primary vein 29 inside the primary body 3, passing successively through the compressor section 18 (low pressure compressor 4 and high pressure compressor 5), the combustion chamber 6 where it is mixed with fuel to serve as an oxidant, and the turbine section 19 (high pressure turbine 7 and low pressure turbine 8).

[0036] Furthermore, the turbomachine 10 comprises a coupling system 50 by which the low pressure turbine 8 drives the fan 22 in rotation around a longitudinal axis X, the coupling system 50 comprising the low pressure shaft 54.

[0037] With reference to [Fig. 3], the coupling system 50 is part of an assembly 60 of the turbomachine 10, said assembly also comprising a structural element 73 of the turbomachine 10 to which the coupling system 50 is connected. The structural element 73 is typically formed by a portion of the casing 26, for example by an inlet casing of the turbomachine 10.

[0038] The coupling system 50 comprises a reducer 52 making it possible to couple an input shaft, which is the low pressure shaft 54, with an output shaft 56 which is the shaft driving the fan 12.

[0039] With reference to [Fig.4], the reducer 52 comprises an input pinion 58 which is driven in rotation by the input shaft 54. Here, this input pinion 58 at least partially surrounds the input shaft 54.

[0040] Preferably, the reducer 52 is, as shown, a spur gear reducer. cycloidal comprising a sun gear constituting the input pinion 58, a crown 53 surrounding the sun gear 58 and a plurality of satellites 52', carried by a planet carrier, engaged with the sun gear 58 and the crown. One of the crown 53 and the planet carrier is fixed and the output shaft 56 is driven in rotation by the other of the crown 53 and the planet carrier.

[0041] Returning to [Fig. 3], the input shaft 54 ​​comprises a proximal section 74 connected to the input pinion 58 of the reducer 52, a distal section 78 connected to the low-pressure turbine 8 and an intermediate section 76 interposed between the distal 78 and proximal 74 sections. Furthermore, the input shaft 54 ​​comprises flexible coupling members 79a, b connecting the intermediate section 76, on the one hand, to the distal section 78 and, on the other hand, to the input pinion 58.

[0042] The assembly 60 also comprises a flexible connecting device 90 making it possible to connect the intermediate section 76 to the structural element 73 via a bearing 92. The bearing 92 makes it possible to guide the intermediate section 76 in rotation relative to the structural element 73.

[0043] The intermediate section 76 being held to the structural element 73 in a flexible manner by the flexible connecting device 90, the radial movements of the intermediate section 76 are permitted but limited. The flexible coupling members 79 positioned on either side of the bearing 92 and intended for managing misalignments of the input shaft 54 ​​can thus be made more flexible while maintaining the resonant frequency of the coupling system 50 outside the operating range of the turbomachine 10. Thus, the coupling system 50 does not risk entering into resonance during operation of the turbomachine 10.

[0044] The flexible connecting device 90 comprises an internal flange 94 secured to the bearing 92 and an external flange 96 secured to the structural element 73. The internal flange 94 and the external flange 96 are preferably circular in shape and the internal flange 94 has a diameter smaller than the diameter of the external flange 96. A plurality of flexible members 98, preferably identical to each other, connect the internal flange 94 and the external flange 96 to each other.

[0045] The set of flexible members 98 allows the intermediate section 76 to be able to move radially relative to the structural element 73 but in a limited manner so as to avoid excessive displacements of the intermediate section 76. Advantageously, the set of flexible members 98 also allows the intermediate section 76 to be able to move longitudinally relative to the structural element 73.

[0046] Each flexible member 98 is elongated along an elongation axis. It is elastically deformable along said elongation axis so as to allow the flexibility of said member 98, but also that of the entire flexible connecting device 90. For this, each flexible member 98 preferably comprises at least one flexible portion 100. In this exemplary embodiment, the flexible portion 100 takes the form of a U-shaped portion. The flexible portion 100 can also be defined as comprising two blades connected together and extending along an axis substantially parallel to the input shaft. According to other possible exemplary embodiments, the flexible portion 100 may comprise one or more bent portions, an S-shaped portion or any other shape allowing deformation of the flexible member 98 along its axis of elongation.

[0047] Here, each flexible member 98 also comprises another portion, relatively stiff (i.e. stiffer than the flexible portion). This stiff portion connects, in the example shown, the flexible portion 100 to the external flange 96. All of the stiff portions of the flexible members 98 form a structure to which all of the flexible portions 100 are connected. This structure is relatively rigid and the flexibility is provided essentially, or even solely, by the flexible portions 100. This structure is here of frustoconical shape.

[0048] The flexible members 98 are typically connected to each other by an intermediate flange (not shown) at the interface between their stiff portion and their flexible portion 100.

[0049] As a variant (not shown), the flexible members 98 consist solely of the flexible portions 100 and the truncated conical structure is a solid structure possibly comprising openings.

[0050] Furthermore, the flexible members 98 form radii distributed regularly around the internal flange 94, which allows flexibility of the flexible connecting device 90 which is homogeneous in the different radial directions. The number of flexible members 98 in the flexible connecting device can range, for example, from 10 to 60.

[0051] The flexible members 98 are dimensioned so that the resonant frequency of the flexible connection device 90 is also located outside the operating range of the turbomachine 10.

[0052] The bearing 92 surrounds the intermediate section 76 so that the intermediate section 76 is guided in rotation by the bearing 92. It comprises an inner ring, an outer ring coaxial with the inner ring and surrounding the latter, and a friction reduction system, for example bearings or rolling elements, between the inner ring and the outer ring. The inner ring is integral with the intermediate section 76 and the outer ring is integral with the inner flange 94, for example by means of screws. The bearing 92 may be, for example, a plain bearing, a ball bearing or a roller bearing. Preferably, the bearing 92 is a roller bearing, thus allowing axial movements of the intermediate section 76 relative to the inner flange 94.

[0053] The external flange 96 is connected to the structural element 73 in a fixed manner, for example by means of screws.

[0054] As previously described, the assembly 60 comprises two flexible coupling members 79a,b which are arranged on either side of the intermediate section 76. In particular, the flexible coupling members 79a,b comprise a first flexible coupling member 79a connecting the intermediate section 76 to the distal section 78 of the shaft 54 ​​and a second flexible coupling member 79b connecting the intermediate section 76 to the input pinion 58.

[0055] Each flexible coupling member 79a,b is configured to allow longitudinal translations and rotations about axes perpendicular to the longitudinal axis X. The flexible coupling members 79a,b thus allow misalignments and longitudinal displacements of the input pinion 58 relative to the input shaft 54, in particular relative to the distal section 78, which limits the loads undergone by the input pinion 58. The flexible coupling members 79a,b together form, in particular, between the proximal section 74 and the distal section 78 of the input shaft 54, a relatively homokinetic coupling connection, also called a homokinetic joint.

[0056] According to a first embodiment shown in [Fig.5], the assembly 60 comprises a downstream flexible coupling member 79a and an upstream flexible coupling member 79b.

[0057] The downstream flexible coupling member 79a comprises a first ring 80a connected to the intermediate section 76, a second ring 81a connected to the distal section 78 and a crown 82a surrounding the first and second rings 80a and 81a. Furthermore, the downstream flexible coupling member 79a comprises a first flexible annular structure 83a interposed between the first ring 80a and the crown 82a and a second flexible annular structure interposed between the second ring 81a and the crown 82a.

[0058] The upstream flexible coupling member 79b is identical to the downstream flexible coupling member 79a except that the second ring 81b is connected to the proximal section 74. The references for the upstream flexible coupling member 79b are identical to those of the downstream flexible coupling member 79a but are indexed “b” instead of “a”.

[0059] The flexible coupling members 79a,b allow relative movements between the intermediate section 76 and the distal section 78, on the one hand, and between the intermediate section 76 and the proximal section 74, on the other hand, while limiting the amplitude of these movements. The flexible annular structures make it possible to absorb part of the misalignments and / or displacements of the sections relative to each other by elastic deformations.

[0060] Preferably, the flexible annular structures 83a, 83b, 84a and 84b are each formed by a solid circular metal membrane pierced in its center so as to allow good transmission of torque around the longitudinal axis and also to have good durability over time.

[0061] The downstream 79a and upstream 79b flexible coupling members constitute what are commonly called “flectors”. They are formed, in this embodiment, by a double-membrane longitudinal shaft seal, each membrane having a disc shape extending radially relative to the shaft. They can also be formed by another type of longitudinal shaft seal such as, for example, a multiple-membrane longitudinal shaft seal or a metal-membrane coupling seal.

[0062] Furthermore, according to a possible variant not shown, the input shaft 54 ​​can be formed in one piece. The downstream and upstream flexible coupling members 79a, 79b are then single-piece members which can be formed by radially enlarged portions of the input shaft 54. They are typically machined from the mass of the input shaft 54.

[0063] Furthermore, in this embodiment, the assembly 60 comprises a flexible connecting device such as that described in more detail with reference to [Fig. 6], this flexible connecting device connecting the proximal section 74 to the input pinion 58 of the reducer 52 while being positioned on either side of said input pinion 58. However, according to a possible variant, the assembly 60 may not comprise this flexible connecting device and the proximal section 74 is then integral with the input pinion 58 of the reducer 52.

[0064] According to a second embodiment shown in [Fig. 6], a first flexible coupling member 79 is identical to the downstream and upstream flexible coupling members 79a and 79b previously described, and a second flexible coupling member is constituted by a flexible coupling device 61.

[0065] In this embodiment, the intermediate section 76 forms a main section driving the input pinion 58 in rotation. The input shaft 54 ​​then does not have a proximal section, or the proximal section 74 and the intermediate section 76 form a main section in a single block.

[0066] The flexible coupling device 61 thus comprises a first flexible coupling element 62a arranged downstream of the input pinion 58 and a second flexible coupling element 62b arranged upstream of the input pinion 58, each flexible coupling element forming a connection between the input pinion 58 and the main section 76.

[0067] In this way, thanks to the flexibility of the first and second flexible coupling elements 62a and 62b, but also thanks to that of the first flexible coupling member 79, the input pinion 58 can move longitudinally and radially relative to the input shaft 54 ​​and therefore undergoes less load than in the systems of the prior art. In particular, rather than having to remain aligned with the input shaft 54 ​​and support the radial loads applied by the other gears of the reducer 52, the input pinion 58 is free to move relative to the input shaft 54, in particular relative to its distal section 78, under the effect of these loads, these movements being compensated by the deformations of the two flexible coupling elements 62a and 62b and of the first flexible coupling member 79.

[0068] The first and second flexible coupling elements 62a, 62b are in particular positioned around the main section 76 near the input pinion 58.

[0069] As shown in [Fig. 6], each flexible coupling element 62a,b comprises a first ring 72a,b connected to the main section 76, a second ring 70a,b connected to the input pinion 58 and a crown 64a,b surrounding the first and second rings 72a,b and 70a,b.Each flexible coupling element 62a,b further comprises a first flexible annular structure 68a,b interposed between the first ring 72a,b and the crown 64a,b and a second flexible annular structure 66a,b interposed between the second ring 70a,b and the crown 64a,b.

[0070] The first and second flexible annular structures 68a,b and 66a,b, by their flexibility, allow the input pinion 58 to move radially and longitudinally relative to the input shaft 54. Indeed, the radial and longitudinal displacements of the input pinion 58 are compensated, at least partially, by the deformations of the first flexible annular structure 68a,b and of the second flexible annular structure 66a,b.

[0071] Each annular structure 66a,b and 68a,b is in particular a flexible annular membrane, in particular a solid circular metal membrane pierced in its center, extending between one of the rings 70a,b and 72a,b and the crown 64a,b, said membrane having flexibility along the longitudinal axis X. The annular structures 66a,b and 68a,b thus allow good transmission of the torque between the rings 70a,b and 72a,b and the crown 64a,b and have good resistance over time.

[0072] Each second ring 70a,b is rigidly connected to the input pinion 58. For example, each inner ring 70a,b tightly surrounds the input pinion 58 and is fixed to the latter, for example, by means of screws. Similarly, each first ring 72a,b is rigidly connected to the main section 76 and, for example, is fixed to the latter by screws.

[0073] Each crown 64a,b makes it possible to maintain an empty space 67a,b between the first flexible annular membrane 68a,b and the second flexible annular membrane 66a,b, which contributes to the flexibility of the flexible coupling elements 62a,b. The empty spaces 67a and 67b are connected by an empty zone 71 which allows the input shaft 54, and in particular the main section 76, and the input pinion 58 not to be in contact with each other. Thus, the drive of the input pinion 58 by the input shaft 54 ​​is only done via the flexible coupling elements 62a and 62b.

[0074] In the first and second embodiments, shown in Figures 5 and 6, the sections 74, 76, 78, the flexible coupling members 79a,b and flexible coupling elements 62a,b are formed from separate parts assembled, for example welded, brazed and / or screwed, to each other.

[0075] Advantageously, the flexible connecting device 90 makes it possible to limit the radial movements of the intermediate section 76 by flexible maintenance of the intermediate section. This device thus makes it possible to compensate for the loss of stiffness resulting from the softening of the flexible coupling members 79a,b intended for managing misalignments and to prevent the resonance frequency of the coupling system 50 from being located in the operating range of the propulsion system 10. Thus, the propulsion system assembly 60 does not risk entering into resonance during operation of the propulsion system 10.

Claims

Claims

1. An aircraft propulsion system assembly (60) comprising a fixed structural element (73) and a shaft (54) rotating about a longitudinal axis (X) relative to the structural assembly, the shaft (54) comprising two flexible coupling members (79) and an intermediate section (76) interposed between the flexible coupling members (79), each flexible coupling member being configured to allow longitudinal translations and rotations about axes perpendicular to the longitudinal axis X, wherein the assembly (60) further comprises a bearing (92) guiding the intermediate section (76) in rotation relative to the structural element (73), said bearing (92) being connected to the structural element (73) via a flexible connecting device (90).

2. A propulsion system assembly (60) according to claim 1, wherein the flexible connecting device (90) comprises an internal flange (94) integral with the bearing (92) and an external flange (96) integral with the structural element (73), the internal flange (94) and the external flange (96) being connected to each other by a plurality of flexible members (98).

3. A propulsion system assembly (60) according to claim 2, wherein each flexible member (98) is elastically deformable in a radial direction relative to the shaft (54).

4. A propulsion system assembly (60) according to any one of claims 2 or 3, wherein the flexible members (98) form radii distributed regularly around the internal flange (94).

5. An assembly (60) according to any one of claims 1 to 4, wherein each flexible coupling member (79, 79a, 79b, 62a, 62b) comprises a first ring (80, 80a, 80b, 72a, 72b) connected to the intermediate section (76), a second ring (81, 81a, 81b, 70a, 70b) connected to another element (78, 74, 58), a crown (82, 82a, 82b, 64a, 64b) surrounding the first and second rings, a first flexible annular structure (83, 83a, 83b, 68a, 68b) interposed between the first ring and the crown and a second flexible annular structure (84, 84a, 84b, 66a, 66b) interposed between the second ring and the crown.

6. A propulsion system assembly (60) according to any one of claims 1 to 5, further comprising a reduction gear (52) coupling the shaft (54), which constitutes an input shaft of the reduction gear, to an output shaft (56), the flexible coupling members (79) comprising a first flexible coupling member connecting the intermediate section (76) to a distal section (78) of the shaft and a second flexible coupling member connecting the intermediate section to the input gear (58).

7. A propulsion system assembly (60) according to any one of claims 1 to 6, comprising a turbine (38) and a fan (12), the input shaft (54) being rotated by the turbine (38) and the output shaft (56) rotating the fan (12),

8. A propulsion system assembly (60) according to any one of claims 1 to 7, wherein the reducer (52) is an epicyclic gear reducer comprising a sun gear constituting the input pinion (58), a crown surrounding the sun gear (58) and a plurality of satellites, carried by a planet carrier, engaged with the sun gear (58) and the crown, one of the crown gear and the planet carrier being fixed and the output shaft (56) being rotated by the other of the crown gear and the planet carrier.

9. An aircraft comprising a propulsion system assembly according to any one of claims 1 to 8.

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