Mechanical reduction gear for an aircraft turbine engine

Abstract

The invention relates to a mechanical reduction gear (100) for a turbine engine, comprising: - a pinion (110) intended to be driven by an input shaft, - a gearwheel (120) which has a main axis (C2) parallel to a main axis (C1) of the pinion and is configured to engage with the pinion (110), and - a geartrain (130) configured to be driven by the gearwheel (120) and having a sun gear (132), a ring gear (134) radially around the sun gear, planet gears (136) and a planet carrier mounted rotatably in relation to the ring gear and to the sun gear, wherein the ring gear, the sun gear and the planet carrier are substantially coaxial with the main axis (C2) of the gearwheel (120), and the planet carrier (138) has a portion for coupling with an output shaft. The sun gear (132) is configured to be rotated by the gearwheel (120) which has a rim (1222) accommodating the ring gear (134).

Description

[0001] DESCRIPTION

[0002] TITLE OF THE INVENTION: MECHANICAL REDUCTION GEARBOX FOR AIRCRAFT TURBOMACHINE

[0003] TECHNICAL FIELD

[0004] The present invention relates to the field of mechanical reducers for turbomachinery, in particular aircraft.

[0005] PREVIOUS TECHNIQUE

[0006] The technical background includes documents DE 10 2020 131802 A1, JP 2018 517098 A1 and EP 3 019 771 B1.

[0007] The role of a mechanical reducer is to modify the speed and torque ratio between the input shaft and the output shaft of a mechanical system.

[0008] Newer generations of turbofan engines, particularly those with a high bypass ratio, incorporate a mechanical gearbox to drive the fan shaft. Typically, the gearbox's purpose is to transform the high rotational speed of the power turbine shaft into a slower rotational speed for the fan shaft.

[0009] Such a reduction gear comprises a central pinion, called the sun gear, a ring gear, and pinions called planet gears, which mesh between the sun gear and the ring gear. The planet gears are held by a frame called the planet carrier. The sun gear, ring gear, and planet carrier are planetary gears because their axes of revolution coincide with the longitudinal axis of the turbomachine. The planet gears each have a different axis of revolution and are evenly spaced on the same operating diameter around the axis of the planet gears. These axes are parallel to the longitudinal axis of the turbomachine.

[0010] Several gearbox architectures exist. In state-of-the-art turbomachinery, gearboxes are of the planetary or epicyclic type. In other similar applications, differential or compound architectures exist.

[0011] - On a planetary reducer, the planet carrier is fixed and the ring forms the output shaft of the device which rotates in the opposite direction to the sun.

[0012] - On an epicyclic reducer, the ring is fixed and the planet carrier constitutes the output shaft of the device which rotates in the same direction as the solar.

[0013] - In a differential gearbox, no element is fixed for rotation. The ring gear rotates in the opposite direction to the sun and the satellite carrier. Gearboxes can consist of one or more meshing stages. This meshing is achieved in various ways, such as by contact, friction, or magnetic fields.

[0014] In this application, the terms "stage" or "toothing" refer to a series of teeth interlocking with a series of complementary teeth. A toothing can be internal or external.

[0015] A satellite can have one or two gear stages. A single-stage satellite has teeth that can be straight, helical, or chevron-shaped, with teeth on the same diameter. These teeth cooperate with both the sun gear and the crown gear.

[0016] A two-stage satellite comprises two sets of teeth or two series of teeth located on different diameters. One set of teeth cooperates with the sun gear and a second set of teeth cooperates with the crown gear.

[0017] Furthermore, each satellite is centered and guided in rotation around an axis by a bearing which is supported by the satellite carrier.

[0018] Such a reduction gear allows for large propellers that can move more air and turbines that rotate quickly and are therefore more efficient.

[0019] However, the presence of a reduction gear in an aircraft engine adds a relatively massive assembly with a significant radial and axial footprint.

[0020] However, compactness and weight are determining factors in the design of an aircraft engine.

[0021] In order to obtain a sufficient reduction ratio of approximately 9, reducers, also called gearboxes, are often composed of at least two reduction stages.

[0022] These reduction stages can be of the pinion / wheel, planetary, and / or epicyclic type. Figure 1 schematically represents an example of a conventional two-stage mechanical reducer mounted on a turbomachine, which typically includes a fan S.

[0023] According to this example, the first reduction stage R1 consists of a pinion 11A driven by an input shaft such as a low-pressure turbine shaft 30A of the turbomachine T, and a gear 12A meshed with the pinion. The second reduction stage R2 consists of a gear train 13A meshing with the gear 12A of the first reduction stage, for example, of the epicyclic or planetary type. The gear train 13A typically comprises a sun gear 132A driven by coupling with the gear of the first reduction stage, a ring gear 134A, planet gears 136A meshing with the ring gear and the sun gear, and a planet carrier 138A coupled to a propeller drive shaft in the case of a turboprop engine or to a fan wheel drive shaft 40A in the case of a turbomachine.

[0024] The presence of a first-stage reduction gear of the pinion / wheel type implies a shift, called an "offset" (denoted D in Figure 1), between the input and output shafts of the gearbox. This offset D is the distance between the axis of the input shaft, for example, the shaft of a low-pressure turbine, and the axis of the output shaft, for example, the drive shaft of a propeller or fan. This gap or offset between the two axes allows the propeller or fan to be raised closer to the wing plane, thus directing airflow both above and below the aircraft wing.

[0025] In general, adding multiple reduction stages increases the axial dimensions, which affects the motor's length, internal arrangement, and mass.

[0026] The objective of the present invention is therefore to overcome these drawbacks.

[0027] SUMMARY OF THE INVENTION

[0028] To this end, the invention relates to a mechanical reducer for a turbomachine comprising:

[0029] - a pinion having a first main axis and intended to be driven by an input shaft,

[0030] - a wheel having a second main axis parallel to the first main axis, the wheel being configured to mesh with the pinion, and

[0031] - a gear train configured to be driven by the wheel and comprising a sun gear having a central axis coaxial with the second main axis, a ring gear arranged radially around the sun gear, satellites configured to mesh with the ring gear and with the sun gear, and a satellite carrier mounted movable in rotation relative to the ring gear and the sun gear and supporting the satellites, in which the ring gear, the sun gear and the satellite carrier are substantially coaxial and the satellite carrier has a coupling part intended to be coupled in rotation with an output shaft.

[0032] According to the invention, the solar panel is configured to be driven in rotation around the central axis by the wheel, and the wheel has a rim housing the ring gear. The invention thus proposes a two-stage reduction gear capable of overcoming the aforementioned drawbacks.

[0033] To this end, the invention proposes a two-stage reduction reducer in which an epicyclic reducer is arranged inside the ring of a wheel.

[0034] Thus, the second reduction stage is nested within the first stage of the reducer, allowing for a reduction and optimization of the radial and axial dimensions of the reducer compared to the prior art.

[0035] Advantageously, this reduction in axial space has an impact on the length of the motor and / or on the internal arrangement of the motor.

[0036] Indeed, the invention makes it possible to integrate accessories onto the reducer without increasing the radial footprint of the motor.

[0037] Such a reducer according to the invention thus advantageously offers a high degree of compactness. The reducer according to the invention may comprise one or more of the following features, taken individually or in combination with each other in all technically possible combinations:

[0038] - the wheel is configured to mesh directly with the pinion;

[0039] - the mechanical reducer includes a reversing pinion having a third main axis substantially parallel to the first main axis, the reversing pinion being configured to mesh with the pinion and with the wheel;

[0040] - the gear train is an epicyclic gear train;

[0041] - the wheel has a flange from which the wheel rim extends in a first direction and a first shaft extending from the flange in a second direction opposite to the first direction;

[0042] - the satellite carrier includes a second shaft extending axially along the second main axis between an upstream end and a downstream end, the second shaft being substantially coaxial with the first shaft, a downstream portion of the second shaft extends inside the first shaft of the wheel so that the downstream end of the second shaft emerges from the first shaft of the wheel;

[0043] - the mechanical reducer includes at least two bearings configured to support and guide the planet carrier, the two bearings each being arranged on the second shaft of the planet carrier respectively at the upstream end and at the downstream end;

[0044] - The wheel comprises a toothed wheel configured to be mechanically connected to at least one piece of equipment of the turbomachine. The invention also relates to a turbomachine, in particular an aircraft turbomachine, comprising a mechanical gearbox according to the invention and as described above.

[0045] The invention also relates to an aircraft comprising such a turbomachine according to the invention and as described above or a mechanical reducer according to the invention and as described above.

[0046] BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The present invention will be better understood and other details, features, and advantages of the present invention will become more apparent upon reading the following description of a non-limiting example, with reference to the accompanying drawings in which:

[0048] - Figure 1, already described, represents a schematic axial cross-sectional view of a reducer according to the prior art;

[0049] - Figure 2 is a schematic axial cross-sectional view of a turbomachine to which the invention applies;

[0050] - Figure 3 is a schematic axial cross-sectional view of a first embodiment of a reducer according to the invention;

[0051] - Figure 4 is a schematic cross-sectional view of the reducer in Figure 3;

[0052] - Figure 5 is a schematic axial cross-sectional view of a second embodiment of a reducer according to the invention; and

[0053] - Figure 6 is a schematic cross-sectional view of the reducer in Figure 5; Elements having the same functions in the different implementations have the same references in the figures.

[0054] In the figures, the scales and proportions are not strictly respected for the purposes of illustration and clarity.

[0055] Furthermore, in the description and claims, the terminology axial, radial, and transverse shall be adopted without limitation, referring to the trihedral axis A, R, T shown in the figures, the axial axis A being parallel to the longitudinal axis of the gearbox according to the invention. Thus, the terms "axial" and "axially" are defined with respect to the axial axis A, which is parallel to the longitudinal axis C of the gearbox. The terms "radial" and "radially" are defined with respect to the axis R, which is perpendicular to the longitudinal axis C of the gearbox. In the description, and unless otherwise stated, the expressions "internal" and "external" are used without limitation with reference to the radial distance from the longitudinal axis around which the lubrication chamber extends, the expression "internal" defining an area radially closer to the longitudinal axis of the gearbox, as opposed to the expression "external."

[0056] DESCRIPTION OF IMPLEMENTATION METHODS

[0057] The present invention relates to a speed reducer intended to equip in particular a turboprop engine or a turbomachine of an aircraft.

[0058] Figure 2 illustrates such a turbomachine 10, which conventionally comprises a fan S, a low-pressure compressor 12, a high-pressure compressor 13, an annular combustion chamber 14, a high-pressure turbine 15, a low-pressure turbine 16, and an exhaust nozzle 17. The high-pressure compressor 13 and the high-pressure turbine 15 are connected by a high-pressure shaft 20 and together form a high-pressure (HP) unit. The low-pressure compressor 12 and the low-pressure turbine 16 are connected by a low-pressure shaft 30 and together form a low-pressure (LP) unit.

[0059] The blower S is driven by a blower shaft 40 which is driven by the low pressure shaft 30 by means of a mechanical reducer 100 according to the invention.

[0060] The mechanical reducer 100 is positioned in the upstream part of the turbomachine. A fixed structure, schematically comprising an upstream part 50a and a downstream part 50b which make up the motor or stator housing 50, is arranged to form an enclosure E surrounding the reducer 100. This enclosure E is closed upstream by seals at the level of a bearing allowing the passage of the blower shaft 40, and downstream by seals at the level of the passage of the low-pressure shaft 30.

[0061] Figures 3 and 4 schematically represent a first embodiment of a mechanical reducer 100 according to the invention. Figure 3 is a schematic axial cross-sectional view of the mechanical reducer according to the invention, while Figure 4 is a schematic transverse cross-sectional view of the mechanical reducer in the BB plane of Figure 3.

[0062] According to this first embodiment, the mechanical reducer 100 according to the invention is of the two-stage reduction type.

[0063] For this purpose, the mechanical reducer 100 according to the invention comprises a pinion 110, a wheel 120, and a gear train 130. The pinion 110 and the wheel 120 form a first reduction stage of the reducer. The gear train 130 forms a second reduction stage of the reducer.

[0064] The pinion 110 has a first main axis C1 intended to be parallel to, and even coincide with, the longitudinal axis X of the turbomachine that the reducer equips.

[0065] The pinion 110 is intended to be driven by an input shaft (not visible), for example by the low-pressure shaft 30 of the turbomachine.

[0066] For this purpose, the pinion 110 of the first stage of the gearbox 100 is connected, at its input, to the input shaft, for example via splines. The pinion 110 has first external splines (not shown) designed to mesh with internal splines on the input shaft, for example the low-pressure turbine shaft of the turbomachine.

[0067] Preferably, the first external splines of the pinion 1 10 meshing with the input shaft are straight or herringbone.

[0068] The 110 pinion is supported by two bearings P1 and P2.

[0069] The 110 pinion has two opposite ends: an upstream end 110a and a downstream end 110b.

[0070] Preferably, the two bearings P1, P2 of the pinion 110 are each arranged at one of the ends 110a, 1 10b of the pinion.

[0071] For example, the two bearings P1, P2 are plain bearings or roller or ball bearings.

[0072] The 120 wheel has a main axis, called the second main axis C2, parallel to the first main axis C1 of the 110 pinion.

[0073] The wheel 120 includes a tubular part forming a first shaft 121 extending axially along the second main axis C2 between a first end, called the upstream end 121a, and a second end, called the downstream end 121b, opposite the upstream end 121a. In the figure, the second main axis C2 is parallel to the axial direction A.

[0074] The wheel 120 further comprises an annular part 122 extending radially outwards from the upstream end 121 a of the tubular part forming the first shaft 121.

[0075] More specifically, the annular part 122 comprises a flange 1221 and a rim 1222. The flange 1221 extends radially outwards from the upstream end 121a of the first shaft 121. Furthermore, the rim 1222 extends from the flange 1221 in a direction parallel to the axial direction A such that the flange 1221 is arranged between the rim 1222 and the first shaft 121. In other words, the rim 1222 of the wheel 120 extends from the flange 1221 in a first direction, namely axially upstream in the example shown, while the tubular part 121 extends from the flange in a second direction opposite to the first direction, namely axially downstream in the example shown.

[0076] Wheel 120 is configured to mesh with pinion 110. More precisely, wheel 120 is configured to mesh directly with pinion 110 according to this first embodiment.

[0077] For this purpose, the pinion 110 of the first stage of the reducer 100 has external splines, called second external splines 114, intended to cooperate by meshing with complementary external splines 124 provided on the wheel 120, and in particular on an external surface 1222A of the rim 1222.

[0078] The second external splines 114 of the pinion 110 are arranged on an external surface of the pinion 110 between its upstream end 121a and its downstream end 121b.

[0079] Preferably, the second external splines 1 14 of the pinion 1 10 meshing with the wheel 120 and the external splines 124 of the wheel 120 are straight or herringbone.

[0080] The 120 wheel is supported by two bearings P3 and P4.

[0081] Preferably, the two bearings P3, P4 are roller or ball bearings.

[0082] Advantageously, the two bearings P3, P4 of the wheel 120 are arranged on the tubular part forming the first shaft 121 of the wheel 120. Preferably, the two bearings P3, P4 of the wheel 120 are each arranged at one of the ends 121 a, 121 b of the tubular part forming the first shaft 121 of the wheel 120.

[0083] Advantageously, the wheel 120 of the first reduction stage of the mechanical reducer 100 can further include a toothed wheel 125 configured to be mechanically connected to one or more pieces of equipment of the turbomachine. For example, the equipment can be a propeller or fan brake, a pump, a generator, or a turning motor, i.e., a low-speed motor useful for maintenance operations.

[0084] Preferably, the toothed wheel 125 extends radially outwards from the tubular part forming the first shaft 121 of the wheel 120.

[0085] Advantageously, the toothed wheel 125 is arranged between the two bearings P3, P4 supporting the wheel 120. The gear train 130 is configured to be driven by the wheel 120.

[0086] Gear train 130 comprises:

[0087] - an internal planetary, also called solar 132,

[0088] - an outer planetary gear, also called the 134 crown,

[0089] - 136 satellites, and

[0090] - a satellite carrier 138.

[0091] The gear train 130 is of the epicyclic type. Thus, the planet carrier 138 and the sun gear 132 are mobile in rotation while the ring gear 134 of the reducer is fixed in the frame of the turbomachine.

[0092] The solar 132 has a central axis coaxial with the second main axis C2 of the wheel 120. In other words, the second main axis C2 is a rotation axis of the solar 132.

[0093] The solar 132 includes a tubular part 1321 extending axially along the second main axis C2 between a first end, called the upstream end 1321 a, and a second end, called the downstream end 1321 b.

[0094] The solar 132 further comprises an annular part 1322 extending radially outwards from the upstream end 1321 a of the tubular part 1321.

[0095] The annular part 1322 of the solar 132 extends into the annular part 122 of the wheel 120.

[0096] Furthermore, the tubular part 1321 extends axially inside the tubular part forming the first shaft 121 of the wheel 120.

[0097] Furthermore, the solar element 132 is mechanically connected to the wheel 120. More precisely, the tubular section 1321 of the solar element 132 is mechanically connected to the tubular section forming the first shaft 121 of the wheel 120. For example, this mechanical connection is achieved by a splined joint, a weld, or a bolted flange. Thus, the solar element 132 is configured to be driven in rotation around the central axis, coaxial with the second main axis C2, by the wheel 120.

[0098] Furthermore, the solar element 132, and more specifically the annular portion 1322, has on a radially external surface 1322A a coupling means for the satellites 136. Preferably, the coupling means comprises radially external teeth 1323. For example, the radially external teeth are straight teeth, helical teeth, or chevron teeth. Alternatively, the coupling means may also comprise radially internal grooves. The ring 134 is arranged axially around the solar element 132. It has a central axis substantially coaxial with the solar element 132. By "axially around the solar element," it is understood, for the purposes of the invention, that the ring 134 extends radially outward from the solar element 132 and, moreover, the ring 134 and the solar element 132 have substantially the same median plane orthogonal to the central axis of the solar element. This median plane is a plane transverse to the central axis of the solar system which is substantially coaxial with the second principal axis C2.

[0099] The ring gear 134 has on its radially internal surface 134B a coupling means for the planet gears 136. Preferably, the coupling means has radially internal teeth 1341. For example, the radially internal teeth are straight, helical, or herringbone teeth. Alternatively, the coupling means may also have radially internal splines. The ring gear 134 is mechanically connected to a housing (not shown) of the gearbox, for example, by a flange.

[0100] According to the invention, the ring gear 134 of the second reduction stage of the mechanical reducer 100 is advantageously integrated into the wheel 120 of the first reduction stage of the mechanical reducer 100. In other words, the ring gear 134 of the gear train 130 is radially internal to the rim 1222 of the wheel 120. That is to say, the ring gear 134 of the gear train 130 has a radially external surface 134A arranged opposite a radially internal surface 1222B of the rim 1222 of the wheel 120.

[0101] The ring 134 of the gear train 130 is housed radially inside the annular part 122 of the wheel 120 of the first reduction stage and radially outside the annular part 1322 of the sun 132 of the gear train 130. In other words, the ring 134 of the gear train 130 has an outside diameter which is less than an inside diameter of the wheel 120 and in particular of the rim 1222 of the latter.

[0102] In other words, a median plane can be defined for the ring 134, called the "first median plane," which is transverse to the central axis of the sun gear, that is, orthogonal to the central axis of the sun gear, which is substantially coaxial with the second principal axis C2. More precisely, this first median plane passes through the midpoint of the teeth of the ring 134. Similarly, the rim 1222 of the wheel 120 has a median plane called the "second median plane," which is transverse to the second principal axis C2. More precisely, this second median plane passes through the midpoint of the teeth of the wheel 120. The distance, along the axial direction A, between the second median plane and the first median plane is less than 2.5 times one axial dimension, or total width, of the teeth of the wheel 120, and preferably less than half the axial dimension of the teeth of the wheel 120.

[0103] The satellites 136 are configured to each mesh simultaneously with the ring gear 134 and the sun gear 132 of the gear train 130. For this purpose, each satellite 136 has a radially external tooth 1361 configured to mesh both with the radially internal tooth 1341 of the ring gear 134 and the radially external tooth 1323 of the annular part 1322 of the sun gear 132. For example, the radially external tooth 1361 of the satellites is a straight tooth or a helical tooth or a herringbone tooth.

[0104] The 136 satellites are equally distributed over the same diameter around the central axis of the solar 132 which coincides with the second main axis C2 of the wheel 120.

[0105] The number of 136 satellites is generally defined as between three and seven for this type of application.

[0106] The set of satellites 136 is held by a chassis called a satellite carrier 138. Each satellite 136 rotates around its own axis Ci.

[0107] The planet carrier 138 is mounted to rotate freely relative to the ring 134 and the sun 132 of the gear train 130. The planet carrier 138 supports the set of satellites 136 in such a way that the rotation of the set of satellites 136 causes the planet carrier 138 to rotate around the central axis of the sun 132 which coincides with the second main axis C2 of the wheel 120.

[0108] The satellite carrier 138 includes a tubular part forming a second shaft 1381 extending axially along the second main axis C2 between a first end, called the upstream end 1381 a, and a second end, called the downstream end 1381 b.

[0109] The planet carrier 138 includes a coupling portion intended to be rotationally coupled to an output shaft. More specifically, the upstream end 1381 of the tubular portion forming the second shaft 1381 of the planet carrier 138 is intended to be mechanically connected to an output shaft, for example, a drive shaft of a propeller or a fan. Preferably, the upstream end 1381 of the second shaft 1381 of the planet carrier 138 has radially external splines, not visible in Figure 3, for coupling with the output shaft. Alternatively, the upstream end 1381 of the second shaft 1381 of the planet carrier 138 is intended to be mechanically connected to the output shaft by a bolted flange or a weld.

[0110] The second shaft 1381 is substantially coaxial with the first shaft 121 of the wheel 120. The tubular part forming the second shaft 1381 of the satellite carrier 138 includes a downstream portion that extends inside the solar 132 and the wheel 120. More precisely, the tubular part forming the second shaft 1381 of the satellite carrier 138 passes through the solar 132 and the wheel 120 in such a way that the downstream end 1381b of the tubular part 1381 emerges from the tubular part forming the first shaft 121 of the wheel 120.

[0111] Furthermore, the satellite carrier 138, and in particular its tubular part forming the second shaft 1381, is supported and guided by three bearings P5, P6 and P7. The three bearings P5, P6 and P7 are arranged on the tubular part forming the second shaft 1381 of the satellite carrier 138.

[0112] Preferably, bearings P5 and P7 are roller bearings or hydrodynamic bearings, while bearing P6 is a thrust ball bearing. The two bearings P5 and P7 of the planet carrier 138 are each arranged at one of the ends 1381a and 1381b of the tubular section 1381 of the planet carrier 138. They are therefore arranged on either side of the solar array 132 and the wheel 120 to optimize the transfer of forces from the propeller or fan by spacing the supporting bearings apart. The thrust ball bearing P6 is arranged at the upstream end 1381a of the tubular section 1381 of the planet carrier 138, between bearing P5 and an annular section 1382 of the planet carrier 138.

[0113] The annular part 1382 of the satellite carrier 138 extends radially outwards from an external surface 1383 of the tubular part 1381.

[0114] The satellite carrier 138 includes shafts 1384 extending axially from the radially external periphery of the annular part 1382 downstream.

[0115] Each satellite 136 is mounted to rotate freely around one of the shafts 1384 via a bearing 1385, for example, a roller bearing or plain bearing. There are a number of shafts 1384 and bearings 1385 equal to the number of satellites 136.

[0116] Figures 5 and 6 schematically represent a second embodiment of a mechanical reducer 200 according to the invention. Figure 5 is a schematic axial cross-sectional view of the mechanical reducer according to the invention, while Figure 6 is a schematic transverse cross-sectional view of the mechanical reducer in the CC plane of Figure 5. This second embodiment differs from the first embodiment in that the mechanical reducer 200 further comprises a reversing pinion 140 and the wheel 120 is configured to mesh with the pinion 110 via the reversing pinion 140.

[0117] The reversing pinion 140 has a main axis, called the third main axis C3, substantially parallel to the first main axis C1 of the pinion 110 and to the second main axis C2 of the wheel 120. The first, second and third main axes C1, C2, C3 respectively of the pinion 110, the wheel 120 and the reversing pinion 140 are distinct from each other and parallel to each other.

[0118] The reversing pinion 140 pinion 110 is configured to be driven by the pinion 110 and to drive the wheel 120.

[0119] For this purpose, the reversing pinion 140 has external splines 144 intended to cooperate by meshing with the second external splines 114 of the pinion 110 and with the external splines 124 of the wheel 120.

[0120] Preferably, the external splines 144 of the reversing pinion 140 engaging the wheel 120 and the pinion 110 have the same teeth as the external splines 124 of the wheel 120 and those of the second external splines 114 of the pinion 110, that is to say straight or herringbone teeth.

[0121] According to this second embodiment, the first reduction stage of the mechanical reducer consists of the pinion 110, the reversing pinion 140 and the wheel 120.

[0122] In operation, the input shaft, for example a low-pressure turbine shaft of a turbomachine, drives the pinion 110 in rotation.

[0123] The pinion 110 drives the wheel 120 in rotation by meshing, either directly, according to the first embodiment, or via the reversing pinion 140, according to the second embodiment. The wheel 120 rotates more slowly than the pinion 110. This assembly, formed by the pinion 110, the wheel 120, and, where applicable, the reversing pinion 140, constitutes the first reduction stage of the mechanical reducer according to the invention.

[0124] The wheel 110 then drives by meshing the gear train 130 and more specifically the solar 132.

[0125] The satellites 136 are configured to be driven in rotation by meshing with the solar element 132 and the fixed ring gear 134. The rotation of the entire set of satellites 136 causes the satellite carrier 138 to rotate around the central axis of the solar element 132, which coincides with the second main axis C2 of the wheel 120. Since the satellite carrier 138 is coupled to an output shaft, for example, a drive shaft for a propeller or a fan, the rotation of the satellite carrier 138 drives the rotation of the propeller or fan. The invention, as described, thus provides a two-stage mechanical reduction gear, the second stage of which, formed by a gear train, is housed within the wheel of the first stage. The invention thus makes it possible to optimize the size, particularly axial, of the reducer and therefore to make the mechanical reducer more compact than those of the prior art, axially and radially.Furthermore, the invention allows accessories to be integrated onto the reducer without increasing the radial footprint of the motor.

[0126] The invention applies to any type of aircraft engine incorporating a fan or propeller and an offset between the axis of the fan shaft and the longitudinal axis of the engine.

Claims

DEMANDS 1. Mechanical gearbox (100; 200) for turbomachine comprising: - a pinion (1 10) having a first main axis (C1) and intended to be driven by an input shaft, - a wheel (120) having a second main axis (C2) parallel to the first main axis (C1), the wheel (120) being configured to mesh with the pinion (110), and - a gear train (130) configured to be driven by the wheel (120) and comprising a sun gear (132) having a central axis coaxial with the second main axis (C2), a ring gear (134) arranged radially around the sun gear, satellites (136) configured to mesh with the ring gear (134) and with the sun gear (132), and a satellite carrier (138) mounted to rotate freely relative to the ring gear (134) and the sun gear (132) and supporting the satellites (136), wherein the ring gear (134), the sun gear (132) and the satellite carrier (138) are substantially coaxial and the satellite carrier (138) comprises a coupling portion intended to be rotationally coupled with an output shaft,The mechanical reducer is characterized in that the solar element (132) is configured to be driven in rotation around the central axis by the wheel (120), and the wheel (120) has a rim (1222) housing the ring gear (134) of the gear train (130).

2. Mechanical reducer (100) according to claim 1, in which the wheel (120) is configured to mesh directly with the pinion (110).

3. Mechanical reducer (200) according to claim 1, comprising a reversing pinion (140) having a third main axis (C3) substantially parallel to the first main axis (C1), the reversing pinion (140) being configured to mesh with the pinion (110) and with the wheel (120).

4. Mechanical reducer (100; 200) according to any one of the preceding claims, wherein the gear train (130) is an epicyclic gear train.

5. Mechanical reducer (100; 200) according to any one of the preceding claims, wherein the wheel (120) has a flange (1221) from which the rim (1222) of the wheel extends in a first direction and a first shaft (121) extending from the flange in a second direction opposite to the first direction.

6. Mechanical reducer (100; 200) according to claim 5, in which the planet carrier (138) comprises a second shaft (1381) extending axially along the second main axis (C2) between an upstream end (1381 a) and a downstream end (1381 b), the second shaft (1381) being substantially coaxial with the first shaft (121), a downstream portion of the second shaft (1381) extends inside the first shaft (121) of the wheel (120) so that the downstream end (1381 b) of the second shaft (1381) emerges from the first shaft (121) of the wheel (120).

7. Mechanical reducer (100; 200) according to claim 6, comprising at least two bearings (P5, P7) configured to support and guide the satellite carrier (138), the two bearings (P5, P7) each being arranged on the second shaft (1381) of the satellite carrier (138) respectively at the upstream end (1381 a) and at the downstream end (1381 b).

8. Mechanical reducer (100; 200) according to any one of the preceding claims, wherein the wheel (120) comprises a toothed wheel (125) configured to be mechanically connected to at least one piece of equipment of the turbomachine.

9. Aircraft turbomachine (10), comprising at least one mechanical reducer (100; 200) according to any one of the preceding claims.

10. Aircraft comprising at least one turbomachine (10) according to claim 9.

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