Mechanical reduction gear for an aircraft turbine engine

Abstract

The invention relates to a mechanical reduction gear (10) for an aircraft turbine engine (1), this reduction gear comprising: - a sun gear (11), - a ring gear (14), - planet gears (12) rotatably guided by bearings (8) and meshed with the sun gear (11) and the ring gear (14), and - a planet carrier (213) comprising a cage (220) in which the sun gear (11) and the planet gears (12) and the bearings (8) thereof are mounted, the cage (220) comprising an annular row of slots (300) which form two skins (236a, 236b) at each of the planet gears (12), one longitudinal end (8a) of each of the bearings (8) being mounted without clearance in the inner skin and with radial clearance (J) in the outer skin.

Description

[0001] DESCRIPTION

[0002] TITLE: MECHANICAL REDUCTION GEAR FOR AN AIRCRAFT TURBOMACHINE

[0003] Technical field of the invention

[0004] The present invention relates to a mechanical reducer for an aircraft turbomachine, as well as a turbomachine comprising such a reducer.

[0005] Technical Downstream Plan

[0006] The state of the art includes in particular documents CN-A-116 292 857, FRAI -2 987 416, FR-A1-2 853 382, ​​FR-A1-3 041 054, FR-A1-3 073 915, FRAI -3 084428.

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

[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 gearbox 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 around the same operating diameter around the axis of the planet gears. These axes are parallel to the longitudinal axis of the turbomachine. 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.

[0010] - 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.

[0011] - 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.

[0012] - On a differential gearbox, no element is fixed in rotation. The ring rotates in the opposite direction to the solar and satellite carrier.

[0013] Gearboxes can consist of one or more meshing stages. This meshing is achieved in various ways, such as by contact, friction, or magnetic field. There are several types of contact meshing, such as with spur or herringbone teeth.

[0014] The satellite carrier can be a single unit or consist of a cage and a cage-bearing assembly. The cage comprises an internal cavity housing the solar array, the satellites, and their guidance bearings. The solar array has internal splines for coupling to a first shaft of the turbomachine, and the cage-bearing assembly has a cylindrical portion with external splines for coupling to another shaft.

[0015] The cage connection to the cage holder is generally rigid. Alternatively, a technology can be considered in which the cage is connected to the cage holder by "flexible" connections, as described in FRAI-2 853 382. In such a case, the cage holder comprises an annular row of axial fingers that carry first connecting elements. These first connecting elements cooperate with second connecting elements mounted in housings in the cage to form the flexible connections between the cage holder and the cage, which allow at least one degree of freedom.

[0016] During operation, the planet carrier is subjected to stresses that tend to deform it. This is the case for a one-piece planet carrier or a cage-and-cage type. These deformations cause the planets to tilt, leading to a degradation of the meshing and the risk of an asymmetrical oil film forming when using plain or hydrodynamic planetary guidance bearings, or the risk of roller tilting when using roller bearings for planetary guidance. These stresses and deformations must be rebalanced to limit or even eliminate these effects.

[0017] Satellite misalignment is an important point to monitor to avoid excessive stress on the gear teeth. To address this, the design of the satellite carrier can be optimized for flexibility to reduce or even eliminate this misalignment. Specifically, incorporating flexible zones into the carrier cage has already been proposed.

[0018] However, the introduction of such flexibility zones can compromise the mechanical strength of the reducer.

[0019] Indeed, a structural component like the satellite carrier is sized according to several operating conditions, divided into two categories: nominal conditions (corresponding to the torques encountered during the different phases of flight) and exceptional conditions (encountered during specific events). The latter are more severe than nominal conditions but occur much less frequently during the engine's lifetime. They must nevertheless be taken into account during the sizing process and require reinforcement of the structure. It is therefore understandable that there is an impact on the mass and flexibility of the gearbox when designing areas of flexibility for these conditions.

[0020] The present invention offers a solution to this problem, which is simple, effective and economical.

[0021] Summary of the invention: The invention relates to a mechanical gearbox for an aircraft turbomachine, this gearbox comprising:

[0022] - a solar panel centered on a central axis,

[0023] - a corona centered on the central axis and extending around the sun,

[0024] - satellites guided in rotation by bearings centered on bearing axes that are parallel to the central axis, the satellites being meshed with the sun and the corona, and

[0025] - a satellite carrier comprising a cage formed from a single piece in which the solar array and the satellites and their bearings are mounted, the cage comprising:

[0026] - a first disc centered on the central axis and extending perpendicularly to this central axis, this first disc having first bearing holes centered respectively on the bearing axes and which are suitable for receiving first longitudinal ends of the bearings,

[0027] - a second disc centered on the central axis and extending parallel and axially at a distance from the first disc, this second disc having second bearing ports which are respectively centered on the bearing axes and which are suitable for receiving second longitudinal ends of the bearings, and

[0028] - bridges extending between the first and second discs and connecting them, the bridges being separated circumferentially from each other by openings intended to be traversed by the satellites for their meshing with the ring, characterized in that the cage comprises around the central axis an annular row of lights which are formed at least partly in the first disc and which extend radially from the outer periphery of the cage where they open radially outwards next to said openings to the inner periphery of the cage, each of these lights locally separating the first disc into two skins, respectively inner and outer, at the level of each of the satellites, the inner skin being located on the inner side of the cage and comprising an inner portion of one of the first bearing orifices,and the outer skin being located on the outside of the cage and comprising an external portion of this first bearing orifice, and in that the first longitudinal end of each of the bearings is mounted without play in the internal portion of one of the first bearing orifices, and with radial play, with respect to the corresponding bearing axis, in the external portion of this first bearing orifice.

[0029] To avoid the aforementioned problem, the invention proposes implementing a bypass mechanism for exceptional loading conditions. The absence of clearance between the first ends of the bearings and the internal portions of the first ports creates primary load paths. The presence of clearance between the first ends of the bearings and the external portions of the first ports creates secondary or standby load paths. These additional load paths are activated during exceptional loading conditions to bypass the areas of flexibility created by the cage openings. Indeed, during exceptional loading conditions, cage deformations bring the first ends of the bearings into contact with the external portions of the first ports, generating additional load paths that relieve stress on the cage's areas of flexibility.

[0030] The present invention is compatible with:

[0031] - of a multi-stage reducer;

[0032] - of a planetary, epicycloidal or differential reducer;

[0033] - with straight or herringbone teeth.

[0034] The reducer according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0035] - the first longitudinal end of each of the bearings comprises a first cylindrical section mounted without clearance in the internal portion of one of the first bearing orifices, this internal portion comprising a first internal cylindrical surface; - the first longitudinal end of each of the bearings comprises a second cylindrical section mounted with clearance in the external portion of one of the first bearing orifices, this external portion comprising a second internal cylindrical surface;

[0036] - the first longitudinal end of each of the bearings includes a second cylindrical section mounted with clearance in the external portion of one of the first bearing orifices, this external portion having a second non-cylindrical internal surface;

[0037] - the second internal surface has a general elliptical or oblong shape;

[0038] - the second internal surface and / or the second section is / are covered with an anti-wear coating;

[0039] - the first section has a first radial thickness which is greater than a second radial thickness of the second section, each of these radial thicknesses being measured with respect to the corresponding bearing axis;

[0040] - the opening of each of the lights at the outer periphery of the cage has a general U-shape;

[0041] - the U shape comprises a central and straight part formed in the first disc and extending in a plane perpendicular to the central axis, and two lateral parts formed respectively in two bridges;

[0042] - the lateral parts are perpendicular to the median part and extend respectively in two planes passing through the central axis;

[0043] - the middle part has an axial width or dimension that is less than a circumferential width or dimension of each of the lateral parts;

[0044] - each of the bridges has a general T-shape due to the lateral parts of the lights, and includes a part of greater circumferential width located on the side of the second disc, and a part of lesser circumferential width located on the side of the first disc;

[0045] - the narrower part of each of the bridges has a circumferential width or dimension which represents at least 1 / 3 of a circumferential width or dimension of the wider part; - the first longitudinal ends of the bearings have a length greater than that of the second longitudinal ends of these bearings;

[0046] -- each of the bridges includes, on the side of the first disc, a V-shaped notch;

[0047] -- said V-shaped notch is formed in the part with the smallest circumferential width of each of the bridges;

[0048] - the cage is formed from a single piece with a cage holder which has a portion-of-a-tree shape and may include external grooves for coupling to another tree;

[0049] - the satellite carrier is of the monobloc type.

[0050] The present invention also relates to an aircraft turbomachine comprising a reducer as described above.

[0051] Brief description of the figures

[0052] Other features and advantages will become apparent from the following description of a non-limiting embodiment of the invention with reference to the accompanying drawings in which:

[0053] [Fig.1] Figure 1 is a schematic axial cross-sectional view of a turbomachine using the invention;

[0054] [Fig.2] Figure 2 is a schematic axial cross-sectional view of a mechanical reducer;

[0055] [Fig.3] Figure 3 is a perspective view of a cage and cage-carrier assembly forming a mechanical reducer planet carrier;

[0056] [Fig.4] Figure 4 is an axial and partial cross-sectional view of part of the satellite carrier of Figure 3;

[0057] [Fig.5] Figure 5 is a detail view of Figure 4;

[0058] [Fig.6] Figure 6 is a schematic front view of the satellite carrier in Figure 3;

[0059] [Fig.7] Figure 7 is a schematic perspective view of a satellite carrier for a reducer according to the invention; [Fig.8] Figure 8 is a larger scale view of part of the satellite carrier of Figure 7 and shows a light and an opening of the cage of the satellite carrier;

[0060] [Fig.9] Figure 9 is a partial schematic axial cross-section view of a reducer and shows more particularly a satellite and its bearing mounted in the cage of a satellite carrier;

[0061] [Fig. 10] Figure 10 is a view similar to that of Figure 9 and represents an embodiment of the invention; and

[0062] [Fig.11] Figure 11 is another view of the embodiment of Figure 10, the section here being made in a plane tangent to a circumference centered on the central axis of the reducer.

[0063] Detailed description of the invention

[0064] Figure 1 depicts a turbomachine 1 which conventionally comprises a fan S, a low-pressure compressor 1a, a high-pressure compressor 1b, an annular combustion chamber 1c, a high-pressure turbine 1d, a low-pressure turbine 1e, and an exhaust nozzle 1h. The high-pressure compressor 1b and the high-pressure turbine 1d are connected by a high-pressure shaft 2 and together form a high-pressure (HP) housing. The low-pressure compressor 1a and the low-pressure turbine 1e are connected by a low-pressure shaft 3 and together form a low-pressure (LP) housing.

[0065] The blower S is driven by a blower shaft 4 which is connected to the BP shaft 3 by means of a mechanical reducer 10. This reducer 10 is generally of the planetary or epicyclic type.

[0066] Although the following description concerns a planetary or epicyclic gearbox, it also applies to a mechanical differential in which its three essential components—the planet carrier, the ring gear, and the sun gear—are free to rotate, the rotational speed of one of these components depending, in particular, on the difference in speeds between the other two components. The gearbox 10 is positioned in the upstream part of the turbomachine. A fixed structure, schematically comprising an upstream part 5a and a downstream part 5b, which together form the motor or stator housing 5, is arranged to form an enclosure E surrounding the gearbox 10. This enclosure E is closed upstream by seals at a bearing that allows the fan shaft 4 to pass through, and downstream by seals at the point where the low-pressure shaft 3 passes through.

[0067] Figure 2 shows part of a gearbox 10, which can take different forms depending on whether certain parts are fixed or rotating. At the input, the gearbox 10 is connected to the shaft BP 3, for example, via splines 7. Thus, the shaft BP 3 drives a planetary gear called the sun gear 11. Typically, the sun gear 11, whose axis of rotation coincides with the X-axis of the turbomachine 1, drives a series of gears called sun gears 12, which are equally spaced circumferentially on the same diameter around the X-axis of rotation. This diameter is equal to twice the operating center distance between the sun gear 11 and the sun gears 12. The number of sun gears 12 is generally defined as between three and seven for this type of application.

[0068] The set of satellites 12 is held by a frame called the satellite carrier 12. Each satellite 12 rotates around its own Y axis, and meshes with the ring 14.

[0069] At the output of the reducer 10, we have: o In an epicycloidal configuration, the set of satellites 12 drives the satellite carrier 13 in rotation around the X axis of the turbomachine. The ring gear 14 is fixed to the motor or stator housing 5 via a ring carrier 15, and the planet carrier 12 is fixed to the fan shaft 4. In a planetary configuration, the set of planets 12 is held by a planet carrier 12, which is fixed to the motor or stator housing 5. Each planet drives the ring gear, which is connected to the fan shaft 4 via a ring carrier 15. Each planet 12 is mounted to rotate freely by means of a bearing 8 around a Y-axis. The Y-axes of rotation of the planets 12 are distributed around the X-axis and parallel to this X-axis. The bearings 8 are, for example, of the roller bearing or hydrodynamic bearing type.Each bearing 8 is mounted on a physical axis 13a of the planet carrier 12 and all these physical axes 13a are positioned relative to each other using one or more structural frames of the planet carrier 12. There is a number of physical axes 13a and bearings 8 equal to the number of planets 12. For reasons of operation, assembly, manufacturing, control, repair or replacement the axes 13a and the frame can be separated into several parts.

[0070] For the same reasons mentioned previously, the teeth of a reduction gear can be separated into several helices. In our example, we detail the operation of a multi-helix reduction gear 10 with a ring gear divided into two half-rings: A front half-ring 14a consisting of a rim 14aa and a mounting flange half 14ab. The front helix of the reduction gear teeth is located on the rim 14aa. This front helix meshes with that of the satellite gear 12, which meshes with that of the solar gear 11. A rear half-ring 14b consisting of a rim 14ba and a mounting flange half 14bb. The rear helix of the reduction gear teeth is located on the rim 14ba. This rear helix meshes with that of the satellite gear 12, which meshes with that of the solar gear 11.

[0071] The front sprocket 14a mounting bracket half-flange 14ab and the rear sprocket 14b mounting bracket half-flange form the sprocket mounting bracket 14c. The sprocket 14 is attached to the sprocket carrier 15 by joining the sprocket mounting bracket 14c and the sprocket carrier mounting bracket 15a using, for example, a bolted assembly. In the following, a half-flange may be referred to as a flange.

[0072] The arrows in Figure 2 describe the oil flow within the gearbox 10. The oil enters the gearbox 10 from the stator section 5 into the distributor 16 by various means, which will not be detailed in this view as they are specific to one or more types of architecture. The distributor 16 is divided into two parts, each generally repeated with the same number of planetary gears. The injectors 17a lubricate the gear teeth, and the arms 17b lubricate the bearings 8. The oil is supplied to the injector 17a and exits through the end 17c to lubricate the gear teeth. The oil is also supplied to each arm 17b and flows through the supply mouth 17d of the bearing 8. The oil then flows through the shaft 13a into one or more buffer zones 13b and then out through ports 13c to lubricate the bearings 8 of the satellites.

[0073] The satellite carrier 13 in Figure 2 is formed from a single piece in the example shown.

[0074] In figures 3 to 5, the elements already described above are designated by the same references plus one hundred.

[0075] Figures 3 to 5 represent a particular satellite carrier technology 113, this satellite carrier comprising a cage 120 and a cage carrier 122 connected by ball joints.

[0076] The cage 120 comprises two radial annular discs or walls 136, 138 which are parallel to each other and perpendicular to the X axis, as well as a cylindrical wall 140 which extends between the external peripheries of these discs walls 136, 138.

[0077] The cylindrical wall 140 is of the double-skinned type and comprises an outer skin 140a interrupted by openings 143 and an inner skin 140b interrupted by the same openings 143. The outer skin 140a, separated by five openings 143, forms five outer brackets, and the inner skin 140b, separated by five openings 143, forms five inner brackets. Each pair of lower and upper brackets forms a clevis to receive the finger 182 of the cage holder 122. In other words, the brackets of each pair define a recess 180 for receiving a finger 182 of the cage holder 122. The brackets provide the structural connection between the walls 136 and 138. Oblong openings 180a are made in at least one of the walls 136 and 138 to allow the finger 182 to pass between the inner and outer brackets. These 180a lights open into the 180 housing units.

[0078] The cage 120 thus comprises an annular row of housings 180. These housings 180 receive the axial fingers 182 which are integral with an annular wall 182a substantially radial to the cage holder 122. The wall 182a is located at an axial end of the cage holder 122. The fingers 182 extend axially from the wall 182a and are engaged by axial translation in the housings 180.

[0079] Each finger 182 includes, substantially in its middle, a mounting ring 184 for the ball joint 186 intended to be traversed by a cylindrical pin 188 carried by the cage 120.

[0080] The ring 184 has a substantially radial orientation with respect to the X-axis. It has a generally cylindrical shape. The cage 120 and the ball joint 186 have a thickness, measured in a radial direction with respect to the X-axis, which is less than the inter-bridge distance or the radial thickness of the oblong slot 180a, so that they can be engaged in this housing concurrently with the support finger 182 for these parts.

[0081] Each housing 180 is traversed by a pin 188 which has a substantially radial orientation with respect to the X-axis. Each pin 188 comprises a cylindrical body 188a connected at an axial end, here radially internal, to an external annular collar 188b. The pin 188 is engaged by radial translation from the inside through radial holes in the bridges, its collar 188b being designed to bear radially against a flat face 191 of the outer bridge of the cage 120. After insertion of the pin 188 into the holes in the bridges, until the collar 188b bears against the outer bridge, the collar 188b is fixed to this bridge, for example by screwing.

[0082] Figure 6 shows a detail of the disks or walls 136, 138 of the planet carrier 113. In these figures, it can be seen that each of the walls 136, 138 includes first orifices 192, 194 centered respectively on the Y axes of rotation of the planets of the gearbox. In the example shown, there are five orifices 192, 194 on each of the walls 136, 138.

[0083] The invention proposes an improvement for a mechanical gearbox for an aircraft turbomachine.

[0084] As in the examples described above, the mechanical reducer 10 according to the invention comprises:

[0085] - a solar 11 centered on a central axis X,

[0086] - a corona 14 centered on the central axis X and extending around the solar 11,

[0087] - satellites 12 guided in rotation by bearings 8 centered on bearing axes Y which are parallel to the central axis X, the satellites 12 being meshed with the solar 11 and the crown 14, and

[0088] - a satellite carrier.

[0089] The satellite carrier is preferably of the monobloc type as illustrated in Figure 2, but could alternatively be of the cage and cage carrier type as illustrated in Figures 3 to 6. The preceding descriptions in relation to Figures 2 to 6 can therefore be used to illustrate and describe the invention.

[0090] Figures 7 and 8 illustrate one embodiment of a satellite carrier 213 according to the invention.

[0091] The satellite carrier 213 includes a cage 220 formed from a single piece in which the solar array and the satellites and their bearings are intended to be mounted.

[0092] The cage 220 is formed in one piece with a cage holder 222 which has a portion-of-a-tree shape and may include external grooves for coupling to another tree.

[0093] Cage 220 includes:

[0094] - a first disk 236 centered on the X axis, called the first axis or central axis, and extending perpendicularly to this X axis, this first disk 236 having first bearing orifices 292 centered respectively on the Y axes, called bearing axes or second axes, which are parallel to the X axis and arranged around this X axis,

[0095] - a second disk 238 centered on the X axis and parallel and at a distance from the disk 236, this second disk 238 having second bearing ports 294 which are respectively centered on the Y axes, and

[0096] - bridges 296 which extend between the discs 236, 238 and connect them together, these bridges 296 being formed in one piece with the discs 236, 238, and the bridges being separated circumferentially from each other by openings 243 intended to be crossed by the satellites in view of their meshing with the crown.

[0097] The first disc 236 is for example a front or upstream disc, and the second disc 238 is for example a rear or downstream disc, by reference to the position of the reducer in the turbomachine and to the flow of gases in the turbomachine.

[0098] The first disk 236 is preferably the disk connected to the cage carrier 222. The ports 292, 294 are used to mount the satellites, and in particular the satellite guidance bearings, in the satellite carrier 213. The bearings 8 have longitudinal ends 8a, 8b which are housed in these ports 292, 294 (Figures 9-11). The bearings 8 are plain (hydrodynamic) or rolling bearings, for example.

[0099] The peculiarity of the cage 220 of figures 7 and 8 is that it has around the central axis X an annular row of lights 300 which are formed at least in part in one of the disks, such as the first disk 236 for example, and which extend in a radial direction.

[0100] The lights 300 extend radially from the outer periphery of cage 220 where they open radially outwards next to the openings 243, to the inner periphery of cage 220.

[0101] Each of these lights 300 axially and locally separates the first disk 236 into two skins 236a, 236b, respectively internal and external, at the level of each of the satellites 8, as illustrated in figures 8 to 11. The internal skin 236a is located on the inner side of the cage 220 and includes an internal portion 292a of one of the first bearing orifices 292, and the external skin 236b is located on the outer side of the cage 220 and includes an external portion 292b of this first bearing orifice 292.

[0102] The first longitudinal end 8a of each of the bearings 8 is mounted without clearance in the internal portion 292a of one of the first bearing holes 292 and with radial clearance J, relative to the corresponding bearing axis Y, in the external portion 292b of this first bearing hole 292. This configuration is illustrated in Figures 10 and 11, which illustrate the invention. In contrast, Figure 9 relates to a configuration that does not illustrate the invention insofar as the first longitudinal end 8a of each of the bearings 8 is not mounted in an external portion 292b of the corresponding first bearing hole 292.

[0103] The radial clearance can be oriented in one or more radial directions with respect to the corresponding Y bearing axis, and can be oriented in particular directions with respect to the central X axis. For example, the J clearances can be oriented in radial and diametrically opposite directions with respect to each of the Y axes, which correspond to circumferential directions with respect to the X axis.

[0104] The first longitudinal end 8a of each of the bearings 8 preferably includes a first cylindrical section 302 mounted without play in the internal portion 292a of the first corresponding bearing orifice 292, this internal portion 302 preferably comprising a first internal cylindrical surface 304.

[0105] The first longitudinal end 8a of each of the bearings 8 preferably comprises a second cylindrical section 306 mounted with clearance J in the external portion 292b of the corresponding first bearing bore 292. This external portion 306 may include a second internal cylindrical surface 308. Alternatively, this external portion 306 may include a second non-cylindrical internal surface 308. The second internal surface 308 may, for example, have a generally elliptical or oblong shape.

[0106] Advantageously, the second internal surface 308 and / or the second section 306 is / are covered with an anti-wear coating to optimize the service life of the assembly.

[0107] Preferably, the first section 302 has a first radial thickness E1 which is greater than a second radial thickness E2 of the second section 306, each of these radial thicknesses E1, E2 being measured with respect to the corresponding bearing axis Y.

[0108] In the example shown in the drawings, we can see that the outlet of each of the lights 300 at the outer periphery of the cage 220 has a general U shape (figures 7 and 8).

[0109] This U-shaped form includes a central and straight part 300a formed in the first disk 236 and extending in a plane Q1 perpendicular to the central axis X, and two lateral parts 300b, 300c formed respectively in two bridges 296.

[0110] The lateral parts 300b, 300c of each of the lights 300 open onto the inner periphery of the bridges 296.

[0111] Each of the bridges 296 may include on its inner periphery a single orifice 297 into which the inner peripheries of the lateral parts 300a, 300c of two adjacent lumens 300 open. This opening may have a general O-shape, as seen in Figure 7.

[0112] The lateral parts 300b, 300c are perpendicular to the median part 300a and extend respectively in two planes Q2, Q3 passing through the central axis X.

[0113] The central portion 300a preferably has a width L1, or axial dimension, particularly its maximum, which is less than a width L2, or circumferential dimension, particularly its maximum, of each of the lateral portions 300b, 300c. The width L1 is measured in the axial direction, while the width L2 is measured circumferentially with respect to the central axis X. The central portion 300a may have a circumferential length that is greater than the circumferential dimension of an opening 243.

[0114] Figure 7 shows that each of the bridges 296 can have a general T-shape due to the lateral parts 300b, 300c of the lights 300. Each of the bridges 296 comprises a part 296a of greater circumferential width located on the side of the second disk 238, and a part 296b of lesser circumferential width located on the side of the first disk 236.

[0115] The narrower portion 296b of each of the 296 bridges has a width L4, or circumferential dimension, that is at least 1 / 3 of a width L3, or circumferential dimension, of the wider portion. Widths L3 and L4 are measured circumferentially with respect to the central axis X.

[0116] Each of the bridges 296 may include, on the side of the first disc 236, a V-shaped notch 298. This notch 298 is formed in the portion 296b of smallest circumferential width of each of the bridges 296. Each notch 298 preferably has a symmetrical shape with respect to a plane passing through the central axis X and the middle of the bridge 296. Each notch 298 flares axially on the side opposite the second disc 238.

[0117] The first longitudinal ends 8a of the bearings 8 preferably have a length M1 greater than that M2 of the second longitudinal ends 8b of these bearings 8, contrary to the configuration of figure 9 where it is rather the opposite.

[0118] In the example shown, which is not limiting, the second bearing holes 294 of the second disk 238 have diameters D1 larger than those D2 of the first bearing holes 292 (Figures 10 and 11). This is because the second bearing holes 294 accommodate mounting covers 310 for the second longitudinal ends 8b of the bearings 8. These second longitudinal ends 8b are engaged in holes in the covers 310, which are themselves engaged in the second bearing holes 294 of the second disk 238. The holes in the covers 310 can have a diameter D3 equal to the diameter D2 of the first bearing holes 292.

Claims

DEMANDS 1. Mechanical gearbox (10) for an aircraft turbomachine (1), this gearbox comprising: - a solar (11) centered on a central axis (X), - a corona (14) centered on the central axis (X) and extending around the solar (11), - satellites (12) guided in rotation by bearings (8) centered on bearing axes (Y) which are parallel to the central axis (X), the satellites (12) being meshed with the solar element (11) and the corona (14), and - a satellite carrier (213) comprising a cage (220) formed in one piece and in which are mounted the solar array (11) and the satellites (12) and their bearings (8), the cage (220) comprising: - a first disk (236) centered on the central axis (X) and extending perpendicularly to this central axis (X), this first disk (236) having first bearing orifices (292) centered respectively on the bearing axes (Y) and which receive first longitudinal ends (8a) of the bearings (8), - a second disk (238) centered on the central axis (X) and extending parallel and axially at a distance from the first disk (236), this second disk (238) having second bearing ports (294) which are respectively centered on the bearing axes (Y) and which receive second longitudinal ends (8b) of the bearings (8), and - bridges (296) extending between the first and second discs (236) and connecting them, the bridges (296) being circumferentially separated from each other by openings (243) through which the satellites (12) pass for their engagement with the ring (14), characterized in that the cage (220) comprises around the central axis (X) an annular row of lights (300) which are formed at least partly in the first disc (236) and which extend radially from the external periphery of the cage (220) where they open radially outwards next to said openings (243) to the internal periphery of the cage (220), each of these lights (300) locally separating the first disk (236) into two skins (236a, 236b), respectively internal and external, at the level of each of the satellites (12), the internal skin (236a) being located on the internal side of the cage (220) and comprising an internal portion (292a) of one of the first bearing orifices (292), and the external skin (236b) being located on the external side of the cage (220) and comprising an external portion (292b) of this first bearing orifice (292), and in that the first longitudinal end (8a) of each of the bearings (8) is mounted without play in the internal portion (292a) of one of the first bearing orifices (292), and with radial play (J), vis-à-vis the corresponding bearing axis (Y), in the external portion (292b) of this first bearing orifice (292).

2. Reducer (10) according to claim 1, in which the first longitudinal end (8a) of each of the bearings (8) comprises a first cylindrical section (302) mounted without play in the internal portion (304) of one of the first bearing orifices (292), this internal portion (302) comprising a first internal cylindrical surface (304).

3. Reducer (10) according to claim 2, wherein the first longitudinal end (8a) of each of the bearings (8) comprises a second cylindrical section (306) mounted with clearance (J) in the external portion (292b) of one of the first bearing orifices (292), this external portion (292b) comprising a second internal cylindrical surface (308).

4. Reducer (10) according to claim 2, wherein the first longitudinal end (8a) of each of the bearings (8) comprises a second cylindrical section (306) mounted with clearance (J) in the external portion (292b) of one of the first bearing ports (292), this external portion (292b) comprising a second non-cylindrical internal surface (308).

5. Reducer (10) according to claim 4, wherein the second internal surface (308) has a general elliptical or oblong shape.

6. Reducer (10) according to claim 4 or 5, wherein the second internal surface (308) and / or the second section (306) is / are covered with an anti-wear coating.

7. Reducer (10) according to any one of claims 3 to 6, wherein the first section (302) has a first radial thickness (E1) which is greater than a second radial thickness (E2) of the second section (306), each of these radial thicknesses (E1, E2) being measured with respect to the corresponding bearing axis (Y).

8. Reducer (10) according to any one of the preceding claims, wherein the outlet of each of the lights (300) at the outer periphery of the cage (220) has a general U-shape.

9. Reducer (10) according to claim 8, wherein the U-shaped form comprises a central and straight part (300a) formed in the first disk (236) and extending in a plane (Q1) perpendicular to the central axis (X), and two lateral parts (300b, 300c) formed respectively in two bridges (296).

10. Reducer (10) according to claim 9, wherein the lateral parts (300b, 300c) are perpendicular to the median part (300a) and extend respectively in two planes (Q2, Q3) passing through the central axis (X).

11. Reducer (10) according to claim 9 or 10, wherein the middle part (300a) has a width (L1) or axial dimension which is less than a width (L2) or circumferential dimension of each of the lateral parts (300b, 300c).

12. Reducer (10) according to any one of claims 9 to 11, wherein each of the bridges (296) has a general T-shape due to the lateral parts (300b, 300c) of the slots (300), and comprises a circumferential part (296a) of greater width (L3) located on the side of the second disc (238), and a circumferential part (296b) of lesser width (L4) located on the side of the first disc (236).

13. Reducer (10) according to claim 12, wherein the narrower portion (296b) of each of the bridges (296) has a width (L4) or circumferential dimension that is at least 1 / 3 of a width (L3) or circumferential dimension of the wider portion (296b).

14. Reducer (10) according to any one of the preceding claims, wherein the first longitudinal ends (8a) of the bearings (8) have a length (M1) greater than that (M2) of the second longitudinal ends (8b) of these bearings (8).

15. Reducer (10) according to any one of the preceding claims, wherein the cage (220) is formed in one piece with a cage carrier (222) which has a shaft portion shape and may include external splines for coupling to another shaft.

16. Turbomachine (1), in particular for aircraft, comprising a reduction gear (10) according to any one of the preceding claims.

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