REDUCER WITH A SOLAR GUIDING BEARING

Abstract

The invention relates to a coupling system (50) comprising an input shaft (54) extending along a longitudinal axis (X), an output shaft (56) and a reducer (52) coupling the input shaft (54) to the output shaft (56), the reducer being an epicyclic gear reducer comprising a sun driven in rotation by the input shaft (54), a ring surrounding the sun (58) and a plurality of satellites (57), carried by a satellite carrier, meshing with the sun (58) and the ring, the output shaft (56) being driven in rotation by one of the ring and the satellite carrier (57), in which the coupling system (50) further comprises a bearing (60) surrounded at least in part by the sun (58) and guiding the sun (58) in rotation about the longitudinal axis (X) relative to a fixed structure. Figure for the abridged version: Fig. 4

Description

Title of the invention: REDUCER COMPRISING A SOLAR GUIDE BEARING Field of 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, in particular the reducer, 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.

[0007] In particular, flexible coupling devices minimize axial misalignments but do not make it possible to limit radial misalignments at the level of the reducer. Statement of the invention

[0008] An objective of the invention is to enable the coupling of a gas turbine shaft to a reduction gear so as to reduce the loads transmitted to the input gear while having a resonant frequency which is outside the operating range of the gas turbine.

[0009] For this purpose, the invention relates to a coupling system comprising an input shaft extending along a longitudinal axis, an output shaft and a reduction gear coupling the input shaft to the output shaft, the reduction gear being an epicyclic reduction gear comprising a sun gear driven in rotation by the input shaft, a ring gear surrounding the sun gear and a plurality of satellites, carried by a planet carrier, engaged with the sun gear and the ring gear, the output shaft being driven in rotation by one of the ring gear and the planet carrier, in which the coupling system further comprises a bearing surrounded at least in part by the sun gear and guiding the sun gear in rotation around the longitudinal axis relative to a fixed structure.

[0010] The coupling system described above makes it possible to limit the impact of radial displacements of the input shaft on the reducer. Indeed, during operation of the coupling system, the pinion is held radially by the bearing and the radial stresses to which it is subjected, in particular due to misalignments of the input shaft, are damped. This radial retention makes it possible to considerably increase the frequency of the natural bending mode of the shaft. The loads supported by the input pinion are thus limited, which prevents excessive wear of the latter.

[0011] When it is said that the bearing is partially surrounded by the solar, this means that the bearing is surrounded by the solar over at least a portion of its length. Preferably, the bearing is surrounded by the solar over its entire length.

[0012] Preferably, one of the crown and the planet carrier are fixed and the output shaft is rotated by the other of the crown and the planet carrier. The fixed structure is then that of the crown and the planet carrier which is fixed.

[0013] According to particular embodiments of the invention which can be taken alone or in combination: - the bearing is a plain bearing and the coupling system further comprises a lubricant supply device connected to a fixed element and making it possible to inject lubricant at an interface between the plain bearing and the sun gear; preferably, the fixed element is an element of the reducer, for example the planet carrier or the crown; the interface is an area located between an outer surface of the plain bearing and an inner surface of the sun gear and in which these two surfaces are at a constant distance from each other, this distance being at most a few millimeters; thus, at the interface, the inner surface of the sun gear and the outer surface of the plain bearing have complementary shapes; - the plain bearing comprises at least one set of orifices connected to the lubricant supply device and opening at the interface between the bearing and the solar, said at least one set comprising at least two orifices; thus, when the input shaft rotates the solar, the interface is supplied with lubricant at different locations on its circumference by means of the orifices and is then distributed under the effect of the rotation of the solar; the lubricant is thus distributed homogeneously at the interface; - the orifices of a set are distributed around the circumference of the bearing and in the same radial plane extending in a plane perpendicular to the longitudinal axis; - the coupling system further comprises at least one fixing device, said fixing device being connected to the planet carrier; the fixing device may in particular be connected to the pivot of the planet carrier, for example by an elongated portion passing through the pivot along an axis parallel to the longitudinal axis; preferably, the planet carrier may be fixed; - the lubricant supply device is integrated into the fixing device; in this way, the space requirement is limited around the bearing and the reducer; - the fixing device comprises an elongated portion passing through a planet carrier pivot along an axis parallel to the longitudinal axis (X) and the lubricant supply device comprises a supply duct extending inside the elongated portion; - the supply device comprises a main supply duct extending inside the plain bearing along the longitudinal axis, said supply duct main being connected to each of the orifices opening at the interface by a secondary supply conduit; thus, the different secondary supply conduits are supplied by a single source of lubricant; - the bearing is a cylinder of constant diameter; the interface then extends over a portion of the interior surface of the solar, and preferably over the entire interior surface of the solar; the bearing is preferably a plain bearing comprising at least one set of orifices; - the bearing comprises an upstream portion and a downstream portion, the upstream portion and the downstream portion each having an interface with the solar and being connected to each other by a central portion having a radial dimension less than a radial dimension of the upstream portion and the downstream portion; the bearing is preferably a plain bearing and the upstream portion and the downstream portion then each comprise at least one set of orifices so as to be able to lubricate each of the portions; - the bearing comprises an upstream frustoconical portion and a downstream frustoconical portion connected to each other by their ends of smaller diameter in a central part, the solar being configured to comprise an interface with both of the upstream and downstream frustoconical portions; such a bearing has the advantage of being able to hold the solar so as to limit its radial movements but also its axial movements; the bearing is preferably a plain bearing and the central part is provided with at least one set of orifices;

[0014] - the input shaft is formed of several sections, including a coupled proximal section to the solar, a distal section and an intermediate section interposed between the distal and proximal sections, the input shaft further comprising a flexible coupling device comprising a first and a second flexible coupling member connecting the intermediate section respectively to the distal section and to the proximal section, each flexible coupling member allowing longitudinal translations and rotations around axes perpendicular to the longitudinal axis, and in particular only allowing said translations and rotations; the flexible coupling members make it possible to absorb part of the misalignments and / or displacements of the input shaft and are thus complementary to the bearing;the misalignments and / or displacements of the input shaft being compensated by the flexible coupling members and by the bearing, the flexibility of the coupling members can be limited so as to prevent them from entering into resonance in the operating range of the propulsion system in which the coupling system is placed; ; And - each flexible coupling member comprises a first ring connected to the intermediate section, a second ring connected to one of the distal and proximal sections, 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.

[0015] The invention also relates to an aircraft propulsion system comprising a gas generator, a fan and a coupling system such as that previously described, the input shaft being driven in rotation by a gas generator rotor and the output shaft being movable in rotation jointly with a rotor of the fan.

[0016] The invention also relates to an aircraft comprising a coupling system or a propulsion system as previously described. Brief description of the Figures

[0017] 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:

[0018] [Fig.l] is a schematic top view of an aircraft according to one embodiment of the invention;

[0019] [Fig.2] is a schematic view in partial section of a propulsion system of the aircraft of [Fig.l];

[0020] [Fig. 3] is a schematic view of a reducer of the propulsion system of [Fig. 2];

[0021] [Fig. 4] is a partial schematic view in longitudinal section of a coupling system according to the invention;

[0022] [Fig.5a] is a partial schematic view in longitudinal section of a coupling system according to a first embodiment of the invention;

[0023] [Fig.5b] is a schematic view in longitudinal section of a coupling system according to a second embodiment of the invention;

[0024] [Fig.5c] is a schematic longitudinal sectional view of a coupling system according to a third embodiment of the invention; and

[0025] [Fig. 6] is a schematic longitudinal sectional view of a coupling system according to an alternative embodiment of the invention. Detailed description of an example of realization

[0026] 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. As a variant (not shown), the propulsion systems 10 are arranged along the fuselage 4, for example near the tailplane 6. As a further variant (also not shown), the aircraft 1 comprises a single propulsion system 10 or at least three propulsion systems 10.

[0027] One of the propulsion systems 10 is shown in [Fig.2].

[0028] 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”.

[0029] 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.

[0030] 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.

[0031] 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).

[0032] 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.

[0033] The primary body 3 comprises a compressor section 18, a combustion chamber 6 and a turbine section 19.

[0034] The compressor section 18 comprises a low pressure compressor 4 and a high pressure compressor 5.

[0035] The turbine section 19 comprises a high pressure turbine 7 and a low pressure turbine 8.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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).

[0043] Furthermore, the turbomachine 10 comprises a coupling system 50 by which the low-pressure turbine 8 drives the fan 22 in rotation about a longitudinal axis X, the coupling system 50 comprising the low-pressure shaft 54. 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.

[0044] With reference to [Fig. 3], the reducer 52 comprises an input pinion 58 which is driven in rotation by the input shaft 54.

[0045] Preferably, the reducer 52 is, as shown, a reducer with an epicyclic gear train comprising a sun gear constituting the input pinion 58, a crown 53 surrounding the sun gear 58 and a plurality of satellites 55, carried by a planet carrier and 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.

[0046] With reference to [Fig. 4], a coupling system 50 according to the invention, shown partially in [Fig. 4], further comprises a bearing 60 surrounded at least in part by the sun 58 and guiding the sun 58 in rotation around the longitudinal axis X relative to a fixed structure, in particular to a casing (not shown) of the turbomachine 10. An outer surface 65 of the bearing 60 is thus surrounded by an inner surface 59 of solar 58 thus forming an interface 61.

[0047] The coupling system described above makes it possible to limit the impact of radial displacements of the input shaft on the reducer. Indeed, during operation of the coupling system, the sun gear is held radially by the bearing and the radial stresses to which it is subjected, in particular due to misalignments of the input shaft, are damped. This radial holding makes it possible to considerably increase the frequency of the natural bending mode of the shaft. The loads supported by the input pinion are thus limited, which prevents excessive wear of the latter.

[0048] The bearing 60 can have different shapes according to a longitudinal section and has a symmetry of revolution around the longitudinal axis X.

[0049] Furthermore, the bearing 60 is connected to the reducer 52 by that of the crown 53 or the planet carrier 57 which is fixed. Preferably, the planet carrier 57 is fixed and the output shaft 56 is driven in rotation by the crown 53.

[0050] The bearing 60 is in particular connected to the reducer 52 by a first fixing device 70 formed by a fixing plate 72 positioned at an upstream end of the bearing 60 and fixed to the reducer 52. Preferably, the fixing plate 72 extends substantially along a plane perpendicular to the axis of revolution X.

[0051] Preferably, the bearing 60 is a plain bearing and the rotational mobility of the sun 58 relative to the bearing 60 is facilitated by means of lubricant (preferably oil) injected at an interface 61 between the bearing 60 and the sun 58. The injected oil is then in contact with the outer surface 65 of the bearing 60 and with the inner surface 59 of the sun 58 and allows these two surfaces to be movable relative to each other. The coupling system 50 then comprises an oil supply device 62 which is connected to the reducer and which makes it possible to inject oil at the interface 61.

[0052] The oil supply device 62 comprises a main oil supply duct 63 which is connected, on the one hand, to an oil reservoir 64, and, on the other hand, to the bearing 60. In the bearing 60, the main supply duct 63 opens at the interface 61 by means of orifices 67 located on the outer surface 65 of the plain bearing 60.

[0053] The plain bearing 60 comprises one or more sets of orifices 67, each set comprising at least two orifices, preferably distributed regularly around the circumference of the bearing 60. The plain bearing 60 may comprise, for example, one, two or three sets of orifices. The orifices 67 of each set are located in the same radial plane which extends perpendicular to the longitudinal axis.

[0054] Thus, the interface 61 is supplied with oil at different locations on its circumference and the oil can be distributed homogeneously at the interface 61. Indeed, the oil is injected by means of the orifices 67 then is distributed under the effect of the rotation of the sun 58 around the bearing 60.

[0055] According to a possible variant embodiment, the sets of orifices can be distributed differently, for example aligned along a longitudinal axis or even in a staggered manner.

[0056] Each orifice 67 is connected to the main supply duct 63 by a secondary oil supply duct 66 which extends inside the bearing 60. Thus, the different secondary supply ducts 66 are supplied by a single source of oil.

[0057] In this embodiment, the main oil supply duct 63 is integrated with a second fixing device which is formed by the structure through which the supply duct passes.

[0058] According to a possible variant embodiment, the oil supply device may comprise one or more oil reservoirs making it possible to supply one or more main supply conduits.

[0059] Preferably, the planet carrier 57 is fixed and the crown 53 drives the output shaft 56 in rotation. The oil supply device 62 is then connected to the plain bearing 60 and to the planet carrier 57.

[0060] The feed device 62 comprises a second fixing device 68 inside which the main feed duct 63 extends. The second fixing device 68 comprises at least a first elongated portion 69 inserted into the plain bearing 60 passing through its axis of revolution which is the longitudinal axis X.

[0061] Preferably, the second fixing device 68 also comprises a second elongated portion 74 passing through the pivot of one of the satellites 55 to cross it from upstream to downstream along an axis parallel to the longitudinal axis X. This second elongated portion 74 also allows the passage of the main supply duct 63. The oil reservoir 64 is preferably positioned downstream of the reducer 52 and is connected to the second elongated portion 74 and to the main supply duct 63. The oil reservoir 64 can also be positioned upstream of the reducer 52.

[0062] The first elongated portion 69 and the second elongated portion 74 are connected by a third elongated portion 75 which can also be fixed to the planet carrier 57 but not necessarily.

[0063] The main supply conduit 63 extends within the first, second and third elongated portions, and is connected to the oil reservoir 64.

[0064] According to a first embodiment shown in [Fig.5a], the plain bearing 60 is a cylinder of constant diameter surrounded by the solar 58 over its entire length. The plain bearing comprises a single set of orifices 67 each positioned on the surface of the plain bearing 60 and each being connected to a secondary supply conduit 66. The assembly comprises at least three orifices distributed regularly on the surface of the bearing 60. The orifices 67 are placed in a radial plane P extending perpendicular to the longitudinal axis X and positioned in the center of the bearing 60.

[0065] The oil is thus injected so as to form a homogeneous film throughout the interface 61 between the bearing 60 and the solar 58. Preferably, the oil is distributed from the orifices 67 towards the ends of the bearing 60 under the effect of the rotation of the solar 58.

[0066] In this embodiment, the oil supply device 62, the second fixing device 68 and the first fixing device 70 are as described with reference to [Fig.4].

[0067] In a second embodiment shown in [Fig.5b], the coupling system differs from that of the first embodiment in that the plain bearing 60 comprises an upstream portion 76 and a downstream portion 78 each having an interface with the solar. The upstream portion 76 and the downstream portion 78 are connected to each other by a central portion 77 which has a radial dimension smaller than a radial dimension of the upstream portion and the downstream portion. The upstream 76 and downstream 78 portions thus form two axially distant and reduced-sized bearings and each comprise a set of orifices 67 such as that described for the first embodiment. The two upstream 76 and downstream 78 portions make it possible to obtain a total interface with a surface area smaller than that of the first embodiment, while allowing sufficient guidance of the solar. Having a reduced interface makes it possible in particular to use less oil.

[0068] The first fixing device 70 is connected to the end of the upstream portion 76 opposite the central portion 77.

[0069] In this embodiment, the oil supply device 62 comprises two branches to the secondary supply conduits 66, a first branch 79 at the upstream portion 77 and a second branch 79' at the downstream portion 78.

[0070] In a third embodiment shown in [Fig.5c], the coupling system 50 differs from those of the first and second embodiments by the shape of the plain bearing 60, by the second fixing device 68 as well as by the oil supply device 62.

[0071] In this third embodiment, the plain bearing 60 comprises an upstream frustoconical portion 80 and a downstream frustoconical portion 82 connected to each other by their ends of smaller diameter in a central part 83. The plain bearing 60 then comprises a set of orifices 67 positioned at the central part so that the oil can be distributed towards each frustoconical portion under the effect of centrifugal force. The first fixing device 70 is then connected to the end wider than the upstream truncated portion 80.

[0072] Such a bearing has the advantage of being able to hold the solar 58 so as to limit its radial movements but also its axial movements. For this, the bearing is configured to include an interface with one and the other of the upstream and downstream frustoconical portions and thus have a shape complementary to that of the plain bearing.

[0073] In this embodiment, the second fixing device 68 is identical to that of the first and second embodiments but further comprises an additional elongated portion 84 extending between the first and second elongated portions 69 and 74 and along an axis parallel to these two portions. The additional elongated portion 84 is fixed to the planet carrier 57 and forms part of the means for supporting the second fixing device 68 on the planet carrier s.

[0074] Furthermore, in this embodiment, the oil reservoir 64 is positioned upstream of the reducer 52 and the main supply conduit 63 then connects to the second fixing device 68 at the level of the third portion 75.

[0075] According to a possible alternative embodiment, the second fixing device 68 and the lubricant supply device 62 may be identical to those of the first and second embodiments, except for the elements located in the plain bearing 60 which are specific to each embodiment.

[0076] According to a fourth possible embodiment not shown, the bearing could be of concave shape according to a longitudinal sectional view, the part of larger diameter being located in the middle of the bearing. The inner surface of the solar 58 is then of convex shape so as to fit the bearing and form a ball joint. According to this embodiment, the bearing makes it possible to hold the solar so as to limit its radial movements but also its axial movements.

[0077] According to a possible variant embodiment, shown in [Fig. 6] and which can be applied to the embodiments previously described, the input shaft 54 ​​comprises a proximal section 86 connected to the solar 58 of the reducer 52, a distal section 88 connected to the low-pressure turbine 8 and an intermediate section 87 interposed between the distal 88 and proximal 86 sections. Furthermore, the input shaft 54 ​​comprises flexible coupling members 89a, b connecting the intermediate section 87, on the one hand, to the distal section 88 and, on the other hand, to the proximal section 86.

[0078] In particular, the flexible coupling members 89a,b comprise a first flexible coupling member 89a connecting the intermediate section 76 to the distal section 78 of the shaft 54 ​​and a second flexible coupling member 89b connecting the intermediate section 76 to the proximal section 86.

[0079] Each flexible coupling member 89a,b is configured to allow longitudinal translations and rotations about axes perpendicular to the Ion- axis longitudinal X. The flexible coupling members 89a,b thus allow misalignments and longitudinal displacements of the solar 58 relative to the input shaft 54, in particular relative to the distal section 88, which limits the loads undergone by the solar 58. The flexible coupling members 89a,b together form in particular, between the proximal section 86 and the distal section 88 of the input shaft 54, a relatively homokinetic coupling connection, also called a homokinetic joint.

[0080] The flexible coupling members make it possible to absorb part of the misalignments and / or displacements of the input shaft, they are thus complementary to the bearing. The misalignments and / or displacements of the input shaft 54 ​​being compensated by the flexible coupling members 89a,b and by the bearing 60, the flexibility of the coupling members can be limited so as to prevent them from entering into resonance in the operating range of the propulsion system in which the coupling system is placed.

[0081] The downstream flexible coupling member 89a comprises a first ring 90a connected to the intermediate section 76, a second ring 91a connected to the distal section 88 and a crown 92a surrounding the first and second rings 90a and 91a. Furthermore, the downstream flexible coupling member 89a comprises a first flexible annular structure 93a interposed between the first ring 90a and the crown 92a and a second flexible annular structure 94a interposed between the second ring 81a and the crown 92a.

[0082] The upstream flexible coupling member 89b is identical to the downstream flexible coupling member 89a except that the second ring 91b is connected to the proximal section 86. The references for the upstream flexible coupling member 89b are identical to those of the downstream flexible coupling member 89a but are indexed “b” instead of “a”.

[0083] The flexible coupling members 89a,b allow relative movements between the intermediate section 87 and the distal section 88, on the one hand, and between the intermediate section 87 and the proximal section 86, 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.

[0084] Preferably, the flexible annular structures 93a, 93b, 94a and 94b are each formed by a solid circular metal membrane pierced in its center so as to allow good transmission of the torque around the longitudinal axis and also so as to have good resistance over time.

[0085] The downstream 89a and upstream 89b 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 a multi-diaphragm longitudinal shaft seal or a metal diaphragm coupling seal.

[0086] 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 89a, 89b 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.

[0087] Advantageously, the bearing 60 of the input shaft 54 ​​to the solar 58 makes it possible to dimension the flexible coupling members 89a and 89b, so that their resonance frequency is located outside the operating range of the propulsion system 10. Indeed, the flexible coupling members make it possible to absorb part of the misalignments and / or displacements of the input shaft and are thus complementary to the bearing. The misalignments and / or displacements of the input shaft are thus compensated by the assembly of the flexible coupling members and the bearing, and the flexibility of each coupling member can then be limited so as to prevent them from entering into resonance in the operating range of the propulsion system in which the coupling system is placed.

Claims

Claims

1. A coupling system (50) comprising an input shaft (54) extending along a longitudinal axis (X), an output shaft (56) and a reduction gear (52) coupling the input shaft (54) to the output shaft (56), the reduction gear being an epicyclic reduction gear comprising a sun gear rotated by the input shaft (54), a ring gear surrounding the sun gear (58) and a plurality of satellites (57), carried by a planet carrier, engaged with the sun gear (58) and the ring gear, the output shaft (56) being rotated by one of the ring gear and the planet carrier (57), wherein the coupling system (50) further comprises a bearing (60) surrounded at least in part by the sun gear (58) and guiding the sun gear (58) in rotation about the longitudinal axis (X) relative to a fixed structure.

2. A coupling system according to claim 1, wherein the bearing (60) is a plain bearing, the coupling system (50) further comprising a lubricant supply device (62) connected to a fixed element (52) and allowing lubricant to be injected at an interface (59) between the plain bearing (60) and the sun (58).

3. Coupling system according to claim 1 or 2, wherein the coupling system (50) further comprises at least one fixing device, said fixing device being connected to the planet carrier.

4. A coupling system according to claims 2 and 3, wherein the lubricant supply device is integrated into the fixing device.

5. A coupling system according to claim 4, wherein the fixing device comprises an elongated portion passing through a planet carrier pivot along an axis parallel to the longitudinal axis (X) and wherein the lubricant supply device comprises a supply conduit extending inside the elongated portion.

6. Coupling system according to any one of claims 2 to 5, in which the supply device (62) comprises a main supply duct (63) extending inside the plain bearing (60) along the longitudinal axis (X), said main supply duct (63) being connected to orifices opening at the interface (59) by a secondary supply duct (66).

7. A coupling system according to any one of claims 1 to 6, wherein the bearing is a cylinder of constant diameter.

8. A coupling system according to any one of claims 1 to 6, wherein the bearing comprises an upstream portion (76) and a downstream portion (78), the upstream portion and the downstream portion each having an interface with the solar and being connected to each other by a central portion (77) having a radial dimension less than a radial dimension of the upstream portion and the downstream portion.

9. Coupling system according to any one of claims 1 to 6, in which the plain bearing (60) comprises an upstream frustoconical portion (80) and a downstream frustoconical portion (82) connected to each other by their smaller diameter ends in a central part (83), the solar being configured to comprise an interface with both of the upstream and downstream frustoconical portions.

10. A coupling system according to any one of claims 1 to 9, wherein the input shaft (54) is formed of several sections, including a proximal section (86) coupled to the sun (58), a distal section (88) and an intermediate section (87) interposed between the distal (88) and proximal (86) sections, the input shaft (54) further comprising a flexible coupling device (100) comprising first and second flexible coupling members (89a, 89b) connecting the intermediate section (87) respectively to the distal section (88) and to the proximal section (86), each flexible coupling member (89a, 89b) allowing longitudinal translations and rotations around axes perpendicular to the longitudinal axis.

11. A coupling system according to claim 9, wherein each flexible coupling member (89a and 89b) comprises a first ring (90a, 90b) connected to the intermediate section (76), a second ring (91a, 91b) connected to one of the distal and proximal sections (88, 86), a crown (92a, 92b) surrounding the first and second rings, a first flexible annular structure (93a, 93b) interposed between the first ring and the crown and a second flexible annular structure (94a, 94b) interposed between the second ring and the crown.

12. A propulsion system (10) for an aircraft comprising a gas generator, a fan (12) and a coupling system (50) according to any one of claims 1 to 11, the input shaft (54) being rotated by a gas generator rotor (38) and the output shaft (56) being rotatable together with a rotor of the fan.

13. Aircraft comprising a coupling system according to any one of of claims 1 to 11 or a propulsion system according to claim 12.

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