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EP-4739894-A1 - REDUCTION GEAR INCLUDING A BEARING FOR GUIDING THE SUN GEAR

EP4739894A1EP 4739894 A1EP4739894 A1EP 4739894A1EP-4739894-A1

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 reduction gear (52) coupling the input shaft (54) to the output shaft (56), the reduction gear being an epicyclic reduction gear including a sun gear rotated by the input shaft (54), a ring gear surrounding the sun gear (58) and a plurality of planet gears (57), carried by a planet carrier, engaging 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 rotation of the sun gear (58) about the longitudinal axis (X) with respect to a stationary structure.

Inventors

  • ALBOUY, LOIC MARIUS JOSEPH
  • ROUFFET, Jonathan Jean-Pierre

Assignees

  • SAFRAN AIRCRAFT ENGINES

Dates

Publication Date
20260513
Application Date
20240703

Claims (12)

  1. 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) coupling the input shaft (54) to the output shaft (56), the reduction gear being an epicyclic reduction gear comprising a sun gear driven in rotation 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 driven in rotation by one of the ring gear and the planet carrier (57), in which the coupling system (50) further comprises a bearing (60) surrounded at least in part by the sun gear (58) and guiding the solar (58) in rotation about the longitudinal axis (X) relative to a fixed structure and in which the input shaft (54) is driven in rotation by a rotor of the gas generator (38) and the output shaft (56) is movable in rotation together with a rotor of the blower.
  2. 2. Propulsion system (10) according to claim 1, in which 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 making it possible to inject lubricant at an interface (59) between the plain bearing (60) and the solar (58).
  3. 3. Propulsion system (10) 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. 4. Propulsion system (10) according to claims 2 and 3, in which the lubricant supply device is integrated into the fixing device.
  5. 5. Propulsion system (10) according to claim 4, in which the fixing device comprises an elongated portion passing through a planet carrier pivot along an axis parallel to the longitudinal axis (X) and in which the lubricant supply device comprises a supply duct extending inside the elongated portion.
  6. 6. Propulsion system (10) 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. 7. Propulsion system (10) according to any one of claims 1 to 6, in which the bearing is a cylinder of constant diameter.
  8. 8. Propulsion system (10) according to any one of claims 1 to 6, in which 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. 9. Propulsion system (10) 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 ends of smaller diameter in a central part (83), the solar being configured to comprise an interface with both of the upstream and downstream frustoconical portions.
  10. 10. A propulsion system (10) 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 solar (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 about axes perpendicular to the longitudinal axis.
  11. 11. A propulsion system (10) according to claim 10, 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. 12. Aircraft comprising a propulsion system according to any one of claims 1 to 11.

Description

TITLE: REDUCER COMPRISING A SOLAR GUIDE BEARING FIELD OF THE INVENTION 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 New generations of dual-flow turbomachines, particularly those with a high bypass ratio, include a mechanical reducer to drive the shaft of a fan. Typically, the reducer is designed 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. 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 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 (when the reducer is in planetary configuration). For optimum operation of such a turbomachine, the various elements that 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 can go as far as breaking the latter, or to the elements connected to the shaft which can wear out quickly, in particular due to friction. However, since a certain degree of misalignment, which can 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 the misalignment between the upstream bearing and the reducer from causing damage or wear. at the shaft, low pressure turbine and/or reducer level, especially solar. These flexible coupling devices must meet opposing constraints. On the one hand, they must be sufficiently flexible to not induce excessive overload at the level of the solar toothing. On the other hand, they must be sufficiently stiff to not enter into resonance in the operating range of the turbomachine. However, in order to reduce the consumption of such turbomachines, we seek to minimize the size of the reducers while maximizing their reduction ratio, which leads to a reduction in the load level that can be supported by solar energy. Under these conditions, it becomes increasingly difficult to size flexible coupling devices so that they can satisfy the aforementioned double constraint. In particular, flexible coupling devices minimize axial misalignments but do not limit radial misalignments at the reducer level. PRESENTATION OF THE INVENTION An object 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 pinion while having a resonant frequency which is outside the operating range of the gas turbine. For this purpose, the invention relates to a coupling system comprising an input shaft extending along a longitudinal axis, an output shaft and a reducer coupling the input shaft to the output shaft, the reducer being an epicyclic gear reducer 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 about the longitudinal axis relative to a fixed structure. The coupling system described above makes it possible to limit the impact of radial movements of the input shaft on the reducer. In fact, 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 holding makes it possible to considerably increase the frequency of the shaft's natural bending mode. The loads supported by the input pinion are thus limited, which prevents excessive wear of the latter. When the bearing is said to be partially surrounded by solar, it means that the bearing is surrounded by solar for at least part of its length. Preferably, the bearing is surrounded by solar for its entire length. Preferably, one of the crown and the planet carrier are fixed and the output shaft is rotate