Including a reduction gear with a bearing for guiding the sun gear.

Abstract

The present invention relates to a coupling system (50) comprising an input shaft (54) extending along a longitudinal axis (X), an output shaft (56), and a reduction gear (52) connecting the input shaft (54) to the output shaft (56). The reduction gear is a rotary reduction gear comprising a sun gear rotating from the input shaft (54), a ring gear surrounding the sun gear (58), and a plurality of planet gears (57) carried by a planet carrier and meshing with the sun gear (58) and the ring gear. The output shaft (56) is rotated by one of the ring gear and the planet carrier (57). The coupling system (50) further comprises a bearing (60) at least partially surrounding the sun gear (58) and guiding the sun gear (58) to rotate about the longitudinal axis (X) relative to a fixed structure.

Description

Technical Field

[0001] This invention relates to mechanical reduction gears, and to the management of misalignment between the reduction gear and the input shaft connected to it. More specifically, this invention relates to propulsion systems for aircraft, and to the management of misalignment between the fan reduction gear and the turbine shaft in such systems. Background Technology

[0002] New-generation ducted turbines, especially those with high bypass ratios, include mechanical reduction gears to drive the fan shaft. Typically, the purpose of reduction gears is to convert the relatively fast rotational speed of the gas turbine rotor shaft into a slower rotational speed for driving the fan shaft.

[0003] Typically, the reduction gears used in such turbines are planetary reduction gears. A planetary reduction gear consists of a central pinion called the sun gear, a ring gear coaxial with the sun gear, and pinions called planetary gears. The planetary gears mesh between the sun gear and the ring gear and are held by a frame called the planet carrier. Traditionally, the sun gear is driven by the turbine shaft, and the fan shaft is driven by the planet carrier (when the reduction gear is in a planetary configuration) or by the ring gear (when the reduction gear is in a planetary configuration).

[0004] For optimal operation of such a turbine, the various components connected by the shaft must be perfectly aligned with each other and with the shaft itself. Excessive misalignment of the shaft relative to the components connected to it (especially reduction gears) can damage the shaft itself, ultimately leading to shaft failure, or can damage the components connected to the shaft, particularly causing rapid wear due to friction. However, since a certain degree of misalignment (which can be horizontal and / or vertical) and axial displacement at the shaft are unavoidable, known practice is to position one or more flexible coupling devices on the shaft. Therefore, known practice involves positioning a flexible coupling device on the turbine shaft, between the upstream bearing and the reduction gear, designed to prevent any damage or wear at the shaft, low-pressure turbine, and / or reduction gear (especially the sun gear) caused by misalignment between the upstream bearing and the reduction gear.

[0005] These flexible coupling devices must meet opposing constraints. On the one hand, they must be flexible enough to prevent any excessive overload on the sun gear teeth. On the other hand, they must be rigid enough to prevent resonance within the turbine's operating range.

[0006] However, to reduce the power consumption of such turbines, it is desirable to minimize the volume of the reduction gear while maximizing its reduction ratio, which leads to a reduction in the load level that can be supported by the sun gear. Under these conditions, it becomes increasingly difficult to determine the dimensions of the flexible coupling device in a way that satisfies the aforementioned dual constraints.

[0007] In particular, flexible coupling devices should minimize axial misalignment but cannot restrict radial misalignment at the reduction gear. Summary of the Invention

[0008] One object of the present invention is to allow the gas turbine shaft to be connected to a reduction gear to reduce the load transmitted to the input pinion, while achieving a resonant frequency outside the operating range of the gas turbine.

[0009] Therefore, the subject of this invention is a coupling system comprising an input shaft extending along a longitudinal axis, an output shaft, and a reduction gear connecting the input shaft to the output shaft. The reduction gear is a planetary reduction gear comprising a sun gear rotatably driven by the input shaft, a ring gear surrounding the sun gear, and a plurality of planet gears carried by a planet carrier and meshing with the sun gear and the ring gear. The output shaft is rotatably driven by one of the ring gear and the planet carrier. The coupling system further comprises a bearing at least partially surrounding the sun gear and guiding the sun gear to rotate about the longitudinal axis relative to a fixed structure.

[0010] The aforementioned coupling system allows for limiting the effect of radial displacement of the input shaft on the reduction gear. Specifically, during operation of the coupling system, the pinion is radially held by the bearing, and the radial stress on the pinion, particularly the radial stress caused by misalignment of the input shaft, is suppressed. This radial holding significantly increases the frequency of the shaft's natural bending patterns. Therefore, the load supported by the input pinion is limited, preventing excessive wear on the input pinion.

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

[0012] Preferably, one of the ring gear and the planet carrier is fixed, and the output shaft is rotatably driven by the other of the ring gear and the planet carrier. The fixed structure is then the structure formed by the fixed planet carrier and the ring.

[0013] According to specific embodiments of the invention that can be used alone or in combination:

[0014] - The bearing is a sliding bearing, and the coupling system also includes a lubricant supply device connected to a stationary element and capable of injecting lubricant at the interface between the sliding bearing and the sun gear; preferably, the stationary element is a component of a reduction gear, such as a planetary carrier or a ring gear; the interface is the region located between the outer surface of the sliding bearing and the inner surface of the sun gear, wherein the two surfaces are separated from each other by a constant distance, which is at most a few millimeters; therefore, at the interface, the inner surface of the sun gear and the outer surface of the sliding bearing have complementary shapes;

[0015] - The sliding bearing includes at least one set of orifices connected to a lubricant supply device and opening at the interface between the bearing and the sun gear, the at least one set of orifices including at least two orifices; thus, when the input shaft rotatably drives the sun gear, lubricant is supplied to the interface at different positions on the circumference of the interface through the orifices, and then the lubricant is distributed under the rotation of the sun gear; thus, the lubricant is evenly distributed at the interface;

[0016] - A set of orifices are distributed on the circumference of the bearing and in the same radial plane, which extends in a plane perpendicular to the longitudinal axis;

[0017] - The connection system also includes at least one attachment device connected to the planet carrier; the attachment device may in particular be connected to the pivot of the planet carrier, for example by means of an elongated portion of the pivot that runs through the pivot along an axis parallel to the longitudinal axis; preferably, the planet carrier may be fixed.

[0018] - The lubricant supply equipment is included in the attachment equipment; in this way, the volume is limited around the bearings and reduction gears;

[0019] - The attachment includes an elongated portion that traverses the planetary carrier pivot along an axis parallel to the longitudinal axis (X), and the lubricant supply device includes a supply conduit extending within the elongated portion;

[0020] - The supply device includes a main supply pipe extending along a longitudinal axis within a sliding bearing, the main supply pipe being connected via secondary supply pipes to each of the orifices opening onto the interface; thus, the different secondary supply pipes are supplied by a single lubricant source;

[0021] - The bearing is a cylinder of constant diameter; then, the interface extends on a portion of the inner surface of the sun gear, preferably on the entire inner surface of the sun gear; preferably, the bearing is a sliding bearing including at least one set of orifices;

[0022] - The bearing includes an upstream portion and a downstream portion, each having an interface with the sun gear, and the upstream and downstream portions are connected to each other through a central portion, the radial dimension of which is smaller than that of the upstream and downstream portions; preferably, the bearing is a sliding bearing, in which case the upstream and downstream portions each include at least one set of orifices, thus enabling lubrication of each portion;

[0023] - The bearing includes an upstream truncated conical portion and a downstream truncated conical portion, which are connected to each other at a central portion via their respective smaller diameter ends. The sun gear is configured to include interfaces with the upstream and downstream truncated conical portions. This bearing has the advantage of retaining the sun gear to limit not only its radial displacement but also its axial displacement. Preferably, the bearing is a sliding bearing with at least one set of orifices at the central portion.

[0024] - The input shaft is formed by multiple segments, including a proximal segment connected to the sun gear, a distal segment, and an intermediate segment inserted between the distal and proximal segments. The input shaft also includes flexible connecting members, comprising a first flexible connecting member and a second flexible connecting member connecting the intermediate segment to the distal and proximal segments respectively. Each flexible connecting member allows rotation and longitudinal translation about an axis perpendicular to the longitudinal axis, specifically allowing only said rotation and translation. The flexible connecting members allow for the absorption of partial misalignment and / or displacement of the input shaft, thus complementing the bearings. Misalignment and / or displacement of the input shaft are offset by the flexible connecting members and bearings, limiting the flexibility of the connecting members to prevent resonance within the operating range of the propulsion system in which the connecting system is arranged.

[0025] - Each flexible connecting member includes a first bushing connected to the intermediate section, a second bushing connected to one of the distal and proximal sections, an annular gear surrounding the first and second bushings, a first flexible annular structure inserted between the first bushing and the annular gear, and a second flexible annular structure inserted between the second bushing and the annular gear.

[0026] Another subject of the invention is a propulsion system for an aircraft, the propulsion system comprising a gas generator, a fan, and a coupling system, the coupling system being, for example, the coupling system previously described, wherein the input shaft is rotatably driven by the rotor of the gas generator, and the output shaft is rotatably movable in conjunction with the rotor of the fan.

[0027] Another subject of the invention is an aircraft that includes a coupling system or propulsion system as previously described. Attached Figure Description

[0028] Other features and advantages of the invention will become apparent upon reading the following description, given by way of example only and with reference to the accompanying drawings, in which:

[0029] - Figure 1 This is a schematic top view of an aircraft according to an embodiment of the present invention;

[0030] - Figure 2 yes Figure 1 A schematic partial cross-sectional view of the propulsion system of an aircraft;

[0031] - Figure 3 yes Figure 2 A schematic diagram of the reduction gears in the propulsion system;

[0032] - Figure 4 This is a schematic partial longitudinal sectional view of the connection system according to the present invention;

[0033] - Figure 5a This is a schematic partial longitudinal sectional view of the connection system according to a first embodiment of the present invention;

[0034] - Figure 5b This is a schematic longitudinal sectional view of the connection system according to a second embodiment of the present invention;

[0035] - Figure 5c This is a schematic longitudinal sectional view of the connection system according to a third embodiment of the present invention; and

[0036] - Figure 6 This is a schematic longitudinal sectional view of a connection system according to a variant embodiment of the present invention. Detailed Implementation

[0037] In the example shown, aircraft 1 is an airplane. Aircraft 1 typically includes a fuselage 4, a tail 6, and two wings 8. Here, there are two propulsion systems 10, each positioned below a corresponding wing 8. In one variant (not shown), the propulsion systems 10 are positioned along the fuselage 4, for example, near the tail 6. In yet another variant (also not shown), aircraft 1 includes a single propulsion system 10 or at least three propulsion systems 10.

[0038] One of the propulsion systems 10 is in Figure 2 As shown in the image.

[0039] exist Figure 2 In this system, the propulsion system 1 has a main direction extending along the longitudinal axis X. The propulsion system 1 includes a fan section 2 and a main valve core 3, commonly referred to as a "gas generator".

[0040] Fan section 2 includes a fan 22 and a fan housing 12. Fan 22 includes a fan rotor 9. Fan housing 12 surrounds fan rotor 9. Fan rotor 9 is rotatably mounted relative to fan housing 12.

[0041] The fan rotor 9 includes 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 they may have a variable arrangement. In the latter case, each fan blade 14 is pivotally mounted relative to the fan hub 13 along a predetermined axis and connected to a pitch mechanism mounted in the propulsion system 1. The pitch mechanism allows for adjustment of the predetermined angle of the fan blades 14 according to the flight phase.

[0042] In this example, fan section 2 also includes a fan stator 16 fixedly mounted on the fan housing 12. The fan stator 16 includes fixed blades 17, commonly referred to as outlet guide vanes (OGV).

[0043] Alternatively, the exit guide vanes 17 may have a variable setting. Where applicable, and similar to the fan blades 14 of the fan rotor 9, the root of each exit guide vane 17 is pivotally mounted along a set axis and connected to a pitch mechanism (not shown), the setting of which is adjusted by the pitch mechanism according to the flight phase.

[0044] The main valve core 3 includes the compressor section 18, the combustion chamber 6, and the turbine section 19.

[0045] Compressor section 18 includes low-pressure compressor 4 and high-pressure compressor 5.

[0046] Turbine section 19 includes high-pressure turbine 7 and low-pressure turbine 8.

[0047] The propulsion system 1 includes a low-pressure shaft 54 ​​that connects the low-pressure turbine 4 to the low-pressure compressor 8. The low-pressure shaft 54 ​​is rotatably mounted about a longitudinal axis X relative to the housing 26 of the main valve core 3.

[0048] When the propulsion system 1 is in operation, the low-pressure turbine 8 drives the low-pressure compressor 4 to rotate via the low-pressure shaft 54.

[0049] The propulsion system 1 also includes 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 housing 26 about a longitudinal axis X. The high-pressure shaft 10 is coaxial with and extends about a low-pressure shaft 54.

[0050] When the propulsion system 1 is in operation, the high-pressure turbine 7 drives the low-pressure compressor 4 to rotate via the low-pressure shaft 54.

[0051] When the propulsion system is working, the airflow F entering the propulsion system 1 crosses the fan 22 and is then divided into a primary airflow F1 and a secondary airflow F2. The primary airflow F1 and the secondary airflow F2 flow from upstream through the propulsion system 1 to downstream.

[0052] The secondary airflow F2, also known as the "ducted airflow," flows through a secondary air path surrounding the main valve core 3. The secondary airflow F2 allows for cooling of the outer periphery of the main valve core 3 and is used to generate most of the thrust provided by the propulsion system 1.

[0053] The main airflow F1 flows through the main air path 29 in the main valve core 3, and successively passes through the compressor section 18 (low-pressure compressor 4 and high-pressure compressor 5), the combustion chamber 6 (in the combustion chamber 6, the main airflow F1 is mixed with fuel to be used as combustion material) and the turbine section 19 (high-pressure turbine 7 and low-pressure turbine 8).

[0054] Furthermore, the turbine 10 includes a coupling system 50 through which the low-pressure turbine 8 drives the fan 22 to rotate about a longitudinal axis. The coupling system 50 includes a low-pressure shaft 54. The coupling system 50 includes a reduction gear 52, which allows the input shaft, serving as the low-pressure shaft 54, to be coupled to the output shaft 56, serving as the shaft driving the fan 12.

[0055] refer to Figure 3 The reduction gear 52 includes an input pinion 58 that is rotatably driven by the input shaft 54.

[0056] Preferably, as shown in the figure, the reduction gear 52 is a planetary reduction gear, which includes a sun gear constituting the input pinion 58, a ring gear 53 surrounding the sun gear 58, and a plurality of planet gears 55 carried by a planet carrier and meshing with the sun gear 58 and the ring gear. One of the ring gear 53 and the planet carrier is fixed, and the output shaft 56 is rotatably driven by the other of the ring gear 53 and the planet carrier.

[0057] refer to Figure 4 The connection system 50 according to the invention is partially in Figure 4 As shown, the coupling system 50 also includes a bearing 60, which is at least partially surrounded by and guides the sun gear 58 to rotate about the longitudinal axis X relative to the fixed structure, particularly relative to the housing (not shown) of the turbine 10. Therefore, the outer surface 65 of the bearing 60 is surrounded by the inner surface 59 of the sun gear 58, thus forming an interface 61.

[0058] The aforementioned coupling system allows for limiting the effect of radial displacement of the input shaft on the reduction gear. Specifically, during operation of the coupling system, the sun gear is radially held by the bearing, and the radial stress on the sun gear, particularly the radial stress caused by misalignment of the input shaft, is suppressed. This radial holding allows for a significant increase in the frequency of the shaft's natural bending pattern. Therefore, the load supported by the input pinion is limited, preventing excessive wear on the input pinion.

[0059] The bearing 60 may have different shapes along its longitudinal section and has rotational symmetry about the longitudinal axis X.

[0060] Furthermore, the bearing 60 is connected to the reduction gear 52 via either the reduction gear 53 or the fixed planetary carrier 57. Preferably, the planetary carrier 57 is fixed, and the output shaft 56 is rotatably driven by the ring gear 53.

[0061] Specifically, the bearing 60 is connected to the reduction gear 52 via a first attachment device 70, which is formed by an attachment plate 72 positioned at the upstream end of the bearing 60 and attached to the reduction gear 52. Preferably, the attachment plate 72 extends substantially along a plane perpendicular to the axis of rotation X.

[0062] Preferably, bearing 60 is a sliding bearing, and the rotational movement of sun gear 58 relative to bearing 60 is simplified by injecting lubricant (preferably oil) at interface 61 between bearing 60 and sun gear 58. The injected oil then contacts the outer surface 65 of bearing 60 and the inner surface 59 of sun gear 58, allowing these two surfaces to move relative to each other. Thus, coupling system 50 includes an oil supply device 62 connected to the reduction gear and enabling oil injection at interface 61.

[0063] The oil supply device 62 includes a main oil supply pipe 63, which is connected to an oil reservoir 64 on one side and a bearing 60 on the other. In the bearing 60, the main supply pipe 63 is opened to the interface 61 through an orifice 67 located on the outer surface 65 of the sliding bearing 60.

[0064] The sliding bearing 60 includes one or more sets of orifices 67, each set including at least two orifices, preferably, the at least two orifices are regularly distributed around the circumference of the bearing 60. For example, the sliding bearing 60 may include one, two, or three sets of orifices. The orifices 67 in each set are located in the same radial plane extending perpendicular to the longitudinal axis.

[0065] Therefore, oil is supplied to interface 61 at different locations on its circumference, and the oil can be evenly distributed at interface 61. Specifically, oil is injected through orifice 67, and then distributed by the rotation of sun gear 58 around bearing 60.

[0066] According to possible variations, the groups of orifices can be distributed differently, for example, aligned or staggered along the longitudinal axis.

[0067] Each orifice 67 is connected to the main supply line 63 via a secondary oil supply line 66 extending within the bearing 60. Thus, the different secondary supply lines 66 are supplied by a single oil source.

[0068] In this embodiment, the main oil supply pipe 63 is included in the second attachment device, which is formed by the structure through which the supply pipe passes.

[0069] According to possible variations, the oil supply pipeline may include one or more oil reservoirs, enabling supply to one or more oil supply pipelines.

[0070] Preferably, the planetary carrier 57 is fixed, and the ring gear 53 rotatably drives the output shaft 56. Then, the oil supply pipe 62 is connected to the sliding bearing 60 and the planetary carrier 57.

[0071] The supply device 62 includes a second attachment device 68, within which the main supply conduit 63 extends. The second attachment device 68 includes at least one first elongated portion 69, which is inserted into the sliding bearing 60 through the axis of rotation (which is the longitudinal axis X).

[0072] Preferably, the second attachment device 68 further includes a second elongated portion 74 that passes through a pivot of one of the planetary carriers 55 to traverse the pivot from upstream to downstream along an axis parallel to the longitudinal axis X. The second elongated portion 74 also allows passage of the main supply line 63. Preferably, the oil reservoir 64 is located downstream of the reduction gear 52 and connected to the second elongated portion 74 and the main supply line 63. The oil reservoir 64 may also be located upstream of the reduction gear 52.

[0073] The first elongated portion 69 and the second elongated portion 74 are connected by the third elongated portion 75, which may also be attached to the planet carrier 57, but not necessarily to the planet carrier 57.

[0074] The main supply pipe 63 extends within the first elongated section, the second elongated section, and the third elongated section, and connects to the oil reservoir 64.

[0075] according to Figure 5aIn the first embodiment shown, the sliding bearing 60 is a cylinder of constant diameter, surrounded by a sun gear 58 along its entire length. The sliding bearing includes a single set of orifices 67, each orifice 67 positioned on the surface of the sliding bearing 60 and connected to a secondary supply conduit 66. This set includes at least three orifices regularly distributed on the surface of the bearing 60. The orifices 67 are positioned in a radial plane P extending perpendicular to the longitudinal axis X and located at the center of the bearing 60.

[0076] Therefore, oil is injected in such a manner that a uniform film is formed on the entire interface 61 between the bearing 60 and the sun gear 58. Preferably, the oil is distributed from the orifice 67 toward the end of the bearing 60 under the rotation of the sun gear 58.

[0077] In this embodiment, the oil supply device 62, the second attachment device 68, and the first attachment device 70 are as described in reference to Figure 4 As described.

[0078] exist Figure 5b In the second embodiment shown, the connection system differs from that of the first embodiment in that the sliding bearing 60 includes an upstream portion 76 and a downstream portion 78, each having an interface with the sun gear. The upstream portion 76 and downstream portion 78 are connected to each other via a central portion 77, the radial dimension of which is smaller than that of the upstream and downstream portions. Therefore, the upstream portion 76 and downstream portion 78 form two axially spaced and reduced-size bearings, each including a set of orifices 67, such as those described for the first embodiment. Both the upstream portion 76 and downstream portion 78 allow for a total interface with a smaller surface area than that of the interface in the first embodiment, while simultaneously enabling adequate guidance of the sun gear. The reduced interface, in particular, allows for the use of less oil.

[0079] The first attachment device 70 is connected to the end of the upstream portion 76 opposite to the central portion 77.

[0080] In this embodiment, the oil supply device 62 includes two branches leading to the secondary supply pipeline 66, namely a first branch 79 located at the upstream portion 77 and a second branch 79' located at the downstream portion 78.

[0081] exist Figure 5c In the third embodiment shown, the connection system 50 differs from the connection systems in the first and second embodiments in terms of the shape of the sliding bearing 60, the second attachment device 68, and the oil device 62.

[0082] In this third embodiment, the sliding bearing 60 includes an upstream truncated conical portion 80 and a downstream truncated conical portion 82, which are connected to each other at a central portion 83 via their respective smaller diameter ends. The sliding bearing 60 then includes a set of orifices 67 located at the central portion, allowing oil to be distributed to each truncated conical portion under centrifugal force. A first attachment device 70 is then connected to the widest end of the upstream truncated conical portion 80.

[0083] The advantage of this bearing is that it can retain the sun gear 58 in order to limit its radial and axial displacement. To this end, the bearing is constructed to include interfaces with one and the other of the upstream and downstream truncated conical portions, thus having a shape complementary to that of a sliding bearing.

[0084] In this embodiment, the second attachment device 68 is the same as the attachment device in the first and second embodiments, but the second attachment device 68 further includes an additional elongated portion 84 that extends between the first elongated portion 69 and the second elongated portion 74 and along an axis parallel to these two portions. The additional elongated portion 84 is attached to the planet carrier 57 and serves as part of a means for supporting the second attachment device 68 on the planet carrier.

[0085] Furthermore, in this embodiment, the oil reservoir 64 is located upstream of the reduction gear 52, and then the main supply pipe 63 is connected to the second attachment device 68 at the third section 75.

[0086] According to possible variant embodiments, the second attachment device 68 and the oil supply device 62 may be the same as those in the first and second embodiments, except that the element located in the sliding bearing 60 is unique to each embodiment.

[0087] According to a fourth possible embodiment (not shown), the bearing may have a concave shape along its longitudinal section, with the larger diameter portion located in the middle of the bearing. The inner surface of the sun gear 58 then has a convex shape to follow the shape of the bearing and form a rotational connection. According to this embodiment, the bearing allows the sun gear to be held in place to limit its radial and axial displacement.

[0088] According to possible variant embodiments, this implementation, for example Figure 6As shown and applicable to the previously described embodiments, the input shaft 54 ​​includes a proximal section 86 connected to the sun gear 58 of the reduction gear 52, a distal section 88 connected to the low-pressure turbine 8, and an intermediate section 87 inserted between the distal section 88 and the proximal section 86. Furthermore, the input shaft 54 ​​includes flexible connecting members 89a and 89b, which connect the intermediate section 87 to the distal section 88 on one hand, and to the proximal section 86 on the other.

[0089] Specifically, the flexible connecting members 89a and 89b include a first flexible connecting member 89a that connects the intermediate section 76 to the distal section 78 of the shaft 54, and a second flexible connecting member 89b that connects the intermediate section 76 to the proximal section 86.

[0090] Each flexible connecting member 89a, 89b is configured to allow rotation and longitudinal translation about an axis perpendicular to the longitudinal axis X. Therefore, the flexible connecting members 89a, 89b allow misalignment and longitudinal displacement of the sun gear 58 relative to the input shaft 54, particularly relative to the distal section 88, which limits the load borne by the sun gear 58. Specifically, the flexible connecting members 89a, 89b together form a relatively constant velocity connecting link between the proximal section 86 and the distal section 88 of the input shaft 54, also referred to as a constant velocity joint.

[0091] Because the flexible connecting members can absorb some of the misalignment and / or displacement of the input shaft, they complement the bearings. Since the misalignment and / or displacement of the input shaft 54 ​​is offset by the flexible connecting members 89a, 89b and the bearing 60, the flexibility of the connecting members can be limited to prevent resonance within the operating range of the propulsion system in which the connecting system is arranged.

[0092] The downstream flexible connection member 89a includes a first bushing 90a connected to the intermediate section 76, a second bushing 91a connected to the distal section 88, and an annular gear 92a surrounding the first bushing 90a and the second bushing 91a. Furthermore, the downstream flexible connection member 89a includes a first flexible annular structure 93a inserted between the first bushing 90a and the annular gear 92a, and a second flexible annular structure 94a inserted between the second bushing 81a and the annular gear 92a.

[0093] The upstream flexible connecting member 89b is the same as the downstream flexible connecting member 89a, except that the second bushing 91b is connected to the proximal section 86. The reference numerals for the upstream flexible connecting member 89b are the same as those for the downstream flexible connecting member 89a, but it is labeled "b" instead of "a".

[0094] The flexible connecting members 89a and 89b allow relative movement between the intermediate segment 87 and the distal segment 88, and between the intermediate segment 87 and the proximal segment 86, while limiting the amplitude of these movements. The flexible ring structure allows for the absorption of partial misalignment and / or displacement of the segments relative to each other through elastic deformation.

[0095] Preferably, the flexible annular structures 93a, 93b, 94a and 94b are each formed from a solid metal circular film with a centrally drilled hole, so as to allow good torque transmission around the longitudinal axis and good durability over time.

[0096] The downstream flexible coupling member 89a and the upstream flexible coupling member 89b constitute a component commonly referred to as a "flexible member". In this embodiment, the downstream flexible coupling member 89a and the upstream flexible coupling member 89b are formed by a longitudinal shaft seal having a double membrane, each membrane having a disk shape extending radially relative to the shaft. The downstream flexible coupling member 89a and the upstream flexible coupling member 89b may also be formed by another type of longitudinal shaft seal (e.g., a longitudinal shaft seal having multiple membranes or a coupling seal having a metal membrane).

[0097] Furthermore, according to possible variations not shown, the input shaft 54 ​​may be formed from a single component. Then, the downstream flexible coupling member 89a and the upstream flexible coupling member 89b are integral components that can be formed from the radially expanded portion of the input shaft 54. The downstream flexible coupling member 89a and the upstream flexible coupling member 89b are typically machined within the body of the input shaft 54.

[0098] Advantageously, the bearing 60 located on the input shaft 54 ​​on the sun gear 58 allows for the determination of the dimensions of the flexible coupling members 89a and 89b, such that the resonant frequencies of the flexible coupling members 89a and 89b are outside the operating range of the propulsion system 10. Specifically, the flexible coupling members are designed to absorb partial misalignment and / or displacement of the input shaft, thus complementing the bearing. Therefore, the misalignment and / or displacement of the input shaft is offset by a set of flexible coupling members and bearings, and the flexibility of each flexible coupling member can then be limited to prevent the flexible coupling members from resonating within the operating range of the propulsion system in which the coupling system is arranged.

Claims

1. A propulsion system (10) for an aircraft, comprising a gas generator, a fan (12), and a coupling system (50), the coupling system (50) comprising an input shaft (54) extending along a longitudinal axis (X), an output shaft (56), and a reduction gear (52) connecting the input shaft (54) to the output shaft (56), the reduction gear being a planetary reduction gear comprising a sun gear rotatably driven by the input shaft (54), a ring gear surrounding the sun gear (58), and a plurality of planetary gears carried by a planet carrier and meshing with the sun gear (58) and the ring gear, the output shaft (56) being rotatably driven by one of the ring gear and the planet carrier (57), wherein, The connection system (50) also includes a bearing (60) which is at least partially surrounded by and guides the sun gear (58) to rotate about the longitudinal axis (X) relative to the fixed structure, and wherein the input shaft (54) is rotatably driven by the rotor of the gas generator (38), and the output shaft (56) is movable in a rotational manner with the rotor of the fan.

2. The propulsion system (10) according to claim 1, wherein, The bearing (60) is a sliding bearing, and the coupling system (50) further includes a lubricant supply device (62) connected to a fixed element and capable of injecting lubricant at the interface (59) between the sliding bearing (60) and the sun gear (58).

3. The propulsion system (10) according to claim 2, wherein, The connection system (50) also includes at least one attachment device connected to the planet carrier.

4. The propulsion system (10) according to claim 3, wherein, The lubricant supply device is included in the attachment device.

5. The propulsion system (10) according to claim 4, wherein, The attachment device includes an elongated portion that traverses the planetary carrier pivot along an axis parallel to the longitudinal axis (X), and wherein the lubricant supply device includes a supply conduit extending within the elongated portion.

6. The propulsion system (10) according to any one of claims 2 to 5, wherein, The lubricant supply device (62) includes a main supply pipe (63) extending along the longitudinal axis (X) within the sliding bearing (60), the main supply pipe (63) being connected via a secondary supply pipe (66) to each of the orifices opening into the interface (59).

7. The propulsion system (10) according to any one of claims 1 to 5, wherein, The bearing is a cylinder with a constant diameter.

8. The propulsion system (10) according to any one of claims 1 to 5, wherein, The bearing includes an upstream portion (76) and a downstream portion (78), each having an interface with the sun gear, and the upstream portion and the downstream portion are connected to each other via a central portion (77), the radial dimension of which is smaller than that of the upstream portion and the downstream portion.

9. The propulsion system (10) according to any one of claims 2 to 5, wherein, The sliding bearing (60) includes an upstream truncated conical portion (80) and a downstream truncated conical portion (82), which are connected to each other at a central portion (83) via their respective smaller diameter ends, and the sun gear is configured to include an interface with the upstream truncated conical portion and the downstream truncated conical portion.

10. The propulsion system (10) according to any one of claims 1 to 5, wherein, The input shaft (54) is formed by a plurality of segments, including a proximal segment (86) connected to the sun gear (58), a distal segment (88), and an intermediate segment (87) inserted between the distal segment (88) and the proximal segment (86). The input shaft (54) also includes a flexible connecting member (100), which includes a first flexible connecting member and a second flexible connecting member (89a, 89b) connecting the intermediate segment (87) to the distal segment (88) and the proximal segment (86), respectively. Each of the first flexible connecting member and the second flexible connecting member (89a, 89b) allows rotation and longitudinal translation about an axis perpendicular to the longitudinal axis.

11. The propulsion system (10) according to claim 10, wherein, The first flexible connecting member and the second flexible connecting member (89a, 89b) include a first bushing (90a, 90b) connected to the intermediate section (87), a second bushing (91a, 91b) connected to one of the distal section and the proximal section (88, 86), an annular gear (92a, 92b) surrounding the first bushing and the second bushing, a first flexible annular structure (93a, 93b) inserted between the first bushing and the annular gear, and a second flexible annular structure (94a, 94b) inserted between the second bushing and the annular gear.

12. An aircraft comprising a propulsion system according to any one of claims 1 to 11.

Images