Planetary carrier for a reduction gear of an aircraft turbomachine

Description

Technical field of the invention

[0001] The present invention relates in particular to a planet carrier for a speed reducer of an aircraft turbomachine. Technical approval plan

[0002] The state of the art includes in particular documents FR-A1-2 987 416, FR-A1-2 853 382, ​​FR-A1-3 041 054, FR-A1-3 052 213, FR-A1-3 073 915, FR-A1-3 084 428, US-A-5,466,198, DE-U1-20 208 102232, EP-A1-4 108 899, EP-A1- 4 108 900 and EP-A1- 1 945 970.

[0003] The role of a mechanical reducer is to modify the speed ratio and torque between an input shaft and an output shaft of the drive mechanism via a transmission mechanism.

[0004] 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's purpose is to transform the so-called fast rotation speed of a power turbine shaft into a slower rotation speed for the shaft driving the fan.

[0005] Such a gearbox comprises a central pinion, called a sun gear, a crown gear, and pinions called planet gears, which are meshed between the sun gear and the crown gear. The planet gears are held by a frame called a planet carrier. The sun gear, the crown gear, and the planet carrier are planet 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 equally distributed over the same operating diameter around the axis of the planet gears. These axes are parallel to the longitudinal axis of the turbomachine.

[0006] There are several gearbox architectures. In the state of the art of double-flow turbomachinery, gearboxes are of the planetary or epicyclic type. In other similar applications, there are so-called differential or "compound" architectures. On a planetary gearbox, the planet carrier is fixed and the crown constitutes the output shaft of the device which rotates in the opposite direction to the sun. On an epicyclic gearbox, the crown is fixed and the planet carrier constitutes the output shaft of the device which rotates in the same direction as the sun. On a differential gearbox, no element is fixed in rotation. The crown rotates in the opposite direction to the sun and the planet carrier.

[0007] Gearboxes can be composed of one or more meshing stages. This meshing is ensured in different ways such as by contact, friction or even by magnetic field. There are several types of contact meshing such as with straight or herringbone teeth.

[0008] The planet carrier can be a single piece or in the form of a cage and a cage holder. The principle of this second type of cage and cage holder planet carrier is to maintain the cage in its plane of symmetry in order to balance the recovery of forces on either side of each satellite. The cage comprises an internal cavity in which the sun gear, the satellites and the guide bearings of these satellites are housed. The sun gear comprises internal splines for coupling to a first shaft of the turbomachine and the cage holder comprises a tubular portion comprising external splines for coupling to another shaft.

[0009] The connection of the cage to the cage holder is generally rigid. Alternatively, a technology may be envisaged in which the cage is connected to the cage holder by “flexible” connections, such as described in document FR-A1-2 853 382. In such a case, the cage holder comprises an annular row of axial fingers which carry first connection elements. These first connection elements cooperate with second connection elements mounted in housings of the cage to form the flexible connections between the cage holder and the cage, which allow at least one or two degrees of freedom.

[0010] It has already been proposed to make these flexible connections with ball joints, the fingers carrying ball joints crossed by cylindrical pins extending into the housings of the cage.

[0011] Mounting the satellites in the cage is sometimes not possible either from the inside or the outside of the cage, requiring the cage to be cut into several pieces in order to mount the satellites before reassembling the cage parts.

[0012] Under load, the cage parts each take up a portion of the load. The assembly method of the cage parts must allow the transmission of this load to the connections with the cage carrier, and also the resistance to this load. In addition, the guide bearings of the satellites are carried by the cage and must be perfectly positioned after the parts are assembled to ensure proper operation of the reducer.

[0013] The state of the art further includes documents US-A-5,466,198 and DE-U1-20 2018 102232. In document US-A-5,466,198, the planet carrier comprises a cage whose walls are connected by bridges. The cage comprises two parts each comprising a wall and half of the bridges. The connecting plane of these parts is a median plane of the cage and the planet carrier, i.e. a plane which is located in the middle of the cage and passes through the middle of the satellites and the solar.

[0014] The present invention proposes an improvement which provides a simple, effective and economical solution to at least some of the problems mentioned above. Summary of the invention

[0015] The invention relates to a planet carrier for a speed reducer of an aircraft turbomachine, this planet carrier comprising: a cage holder with a main axis and comprising a coupling portion centered on this axis and which has axial cage support fingers distributed around the axis, a cage centered on the axis and comprising two radial annular walls connected to each other by bridges distributed around the axis, the bridges being located at the external periphery of the walls and delimiting with the walls an internal cavity of the cage, the bridges comprising or defining axial housings in which the fingers are mounted, the fingers being connected to the bridges by connections allowing at least one degree of freedom, one of the walls comprising axially through openings which are axially aligned with axially through openings of the other of the walls, characterized in that the cage comprises two parts: a first part comprising one of the walls and the bridges, these bridges projecting axially on one face of this wall and comprising first axial ends connected to this face and second free axial ends, and a second part comprising the other of the walls, this wall comprising a face on which the free ends of the bridges are applied, and in that the two parts of the cage are fixed together by fixing means which pass through the wall of the second part and are inserted into fixing holes of the bridges.

[0016] The attachment of the parts of the planet carrier cage is therefore carried out by clamping the bridges of one of the parts directly to the other of the parts insofar as the second part can be considered as forming or comprising a fixing flange to the bridges of the first part. This attachment allows the transmission of loads in operation. The means of fixing the parts of the cage are advantageously sized to resist this load transmission.

[0017] The mounting openings for the satellite bearings are precisely axially aligned and the method of fixing the cage parts ensures this correct positioning and thus the correct operation of the reducer.

[0018] The fact that the bridges are carried by one of the walls and not divided into two halves carried respectively by the two walls, is particularly advantageous for several reasons. First of all, each of the bridges is formed from a single piece and a single block, which guarantees its integrity and its mechanical strength in operation. Furthermore, the connecting plane of the parts of the cage and therefore the plane of transmission of forces between these parts, is offset to one side of the cage, which is less likely to penalize the operation of the reducer and in particular to alter the meshing of the satellites in operation. In addition, this allows the fixing holes formed in the bridges to be optionally tapped to directly receive the fixing means by screwing (without the need for nuts). This is not possible in the prior art because the bridge halves do not necessarily have sufficient length for the tapping of their fixing holes.

[0019] The present invention is compatible of a single-stage or multi-stage reducer; of a planetary, epicyclic or differential reducer; of straight, helical or herringbone teeth; of any type of satellite bearings, whether composed of rolling elements, hydrodynamic bearings, etc.

[0020] The planet carrier according to the invention may comprise the following features, taken in combination according to the dependent claims: at least one of the parts of the cage comprises centering members for the other of the parts, in order to ensure centering of the parts relative to each other and on the axis; the centering members comprise curved edges which are carried by one of the parts and which extend around the axis, these curved edges cooperating with curved surfaces of the other of the parts; the curved edges are protrusions which extend axially in projection; the first part comprises centering members which are located on the free ends of the bridges, at their radially internal and / or external ends; the second part comprises centering members which are located on said face of its wall;the free end of each of the bridges comprises a bearing face on the aforementioned face of the wall of the second part, the housing of each bridge opening onto this bearing face, and said fixing orifices of the bridges being distributed around the opening of this housing; the wall of the second part comprises axial holes which pass through the wall and are aligned with the housings of the bridges, the wall of the second part comprising axial orifices which are crossed by said fixing means and which are distributed around these holes; the first part is located on the side of the coupling portion of the cage holder; -- said curved edges are capable of cooperating by axial sliding or radial support with the curved surfaces; the fixing means are screws and the fixing holes are tapped to receive the screws by screwing. ;

[0021] The invention also relates to a speed reducer for an aircraft turbomachine, this reducer having a main axis and comprising: a planet carrier as described above, a sun gear extending into the internal cavity of the cage and centered on the axis, satellites arranged in the internal cavity around the axis and the sun gear and meshed with the sun gear, these satellites being centered and guided by bearings whose axial ends are mounted in the aforementioned openings in the walls, and a ring gear arranged around the axis and the cage and meshed with the satellites.

[0022] The invention further relates to a turbomachine, in particular for an aircraft, comprising a reduction gear as described above. Brief description of the figures

[0023] Other characteristics and advantages will emerge from the following description of a non-limiting embodiment of the invention with reference to the appended drawings in which: [ Fig. 1 ] there figure 1 is a schematic axial sectional view of a turbomachine using the invention; [ Fig. 2 ] there figure 2 is a schematic axial sectional view of an epicyclic gear reducer; [ Fig. 3 ] there figure 3 is a schematic perspective view of a cage of a reducer planet carrier; [ Fig. 4 ] there figure 4 is a schematic axial sectional view of a cage and a cage holder of planet carriers; [ Fig. 5 ] there Figure 5 is a detail view of the figure 4 ; [ Fig. 6 ] there figure 6 is a partial schematic view similar to that of the Figure 5 and illustrating a first embodiment of a satellite carrier according to the invention; [ Fig. 7 ] there figure 7 is a schematic exploded perspective view of the planet carrier of the figure 6 ; [ Fig. 8 ] there figure 8is a schematic perspective view of one of the parts of a planet carrier according to an alternative embodiment of the invention; [ Fig. 9 ] there figure 9 is a schematic perspective view of the other parts of the planet carrier according to the same embodiment variant. Detailed description of the invention

[0024] There figure 1 describes a turbomachine 1 which comprises, in a conventional manner, 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 form with it a high-pressure (HP) body. The low-pressure compressor 1a and the low-pressure turbine 1e are connected by a low-pressure shaft 3 and form with it a low-pressure (LP) body.

[0025] The blower S is driven by a blower shaft 4 which is connected to the LP shaft 3 by means of a reducer 10. This reducer is generally of the planetary or epicyclic type.

[0026] Although the following description concerns a planetary or epicyclic type reducer, it also applies to a mechanical differential in which its three essential components, namely the planet carrier, the crown and the sun gear, are mobile in rotation, the rotation speed of one of these components depending in particular on the difference in speeds of the other two components.

[0027] The reducer 10 is positioned in the upstream part of the turbomachine. A fixed structure comprising schematically, here, an upstream part 5a and a downstream part 5b which composes the motor casing or stator 5 is arranged so as to form an enclosure E surrounding the reducer 10. This enclosure E is here closed upstream by seals at the level of a bearing allowing the fan shaft 4 to pass through, and downstream by seals at the level of the passage of the LP shaft 3.

[0028] There figure 1shows a part of a reducer 10 which can take the form of different architectures depending on whether certain parts are fixed or rotating. At the input, the reducer 10 is connected to the LP shaft 3, for example via splines 7. Thus, the LP shaft 3 drives a planetary pinion called the sun gear 11. Conventionally, the sun gear 11, whose axis of rotation coincides with the X axis of the turbomachine 1, drives a series of pinions called satellites 12, which are equally distributed over the same diameter around the axis of rotation X. This diameter is equal to twice the operating center distance between the sun gear 11 and satellites 12. The number of satellites 12 is generally defined between three and seven for this type of application.

[0029] All of the satellites 12 are held by a frame called a planet carrier 13. Each satellite 12 rotates around its own Y axis, and meshes with the crown 14.

[0030] At the output of reducer 10, we have: o in an epicyclic configuration, the set of planet gears 12 rotates the planet carrier 13 around the axis X of the turbomachine. The ring gear 14 is fixed to the engine casing or stator 5 via a ring gear carrier 15 and the planet carrier 13 is fixed to the fan shaft 4. ∘ in a planetary configuration, the set of planet gears 12 is held by a planet carrier 13 which is fixed to the engine casing or stator 5. Each planet gear 12 drives the ring gear 14 which is connected to the fan shaft 4 via a ring gear carrier 15.

[0031] Each satellite 12 is mounted to rotate freely using a bearing 8, for example of the rolling or hydrodynamic type. Each bearing 8 is mounted on one of the axes 13a of the planet carrier 13 and all the axes are positioned relative to each other using one or more structural frames of the planet carrier 13. There is a number of axes and bearings equal to the number of satellites 12.

[0032] In the example shown, the crown 14 is separated into two half-crowns and comprises: o a front half-crown 14a consisting of a rim 14aa and a fixing half-flange 14ab. On the rim 14aa is the front helix of the gear teeth. This front helix meshes with that of the satellite 12 which meshes with that of the sun gear 11. o a rear half-crown 14b consisting of a rim 14ba and a fixing half-flange 14bb. On the rim 14ba is the rear helix of the gear teeth. This rear helix meshes with that of the satellite 12 which meshes with that of the sun gear 11.

[0033] The half-clamp 14ab of the front crown 14a and the half-clamp 14bb of the rear crown 14b form the crown mounting flange 14c. The crown 14 is fixed to the crown carrier 15 by assembling the crown mounting flange 14c and the crown carrier mounting flange 15a using a bolted assembly for example.

[0034] The arrows of the figure 1describe the oil routing in the reducer 10. The oil arrives in the reducer 10 from the stator part 5 in the distributor 16 by different means which will not be specified in this view because they are specific to one or more types of architecture. The distributor 16 is separated into two parts, generally each repeated by the same number of satellites. The injectors 17a have the function of lubricating the teeth, and the arms 17b have the function of lubricating the bearings 8. The oil is brought towards the injector 17a to exit through the end 17c in order to lubricate the teeth. The oil is also supplied to each arm 17b and circulates via the supply opening 17d of the bearing 8. The oil then circulates through the axis 13a in one or more buffer zones 13b and then exits through orifices 13c in order to lubricate the bearings 8 of the satellites.

[0035] In the figures 3 to 5, the elements already described in the above are designated by the same references increased by one hundred.

[0036] THE figures 3 to 5 represent a particular technology of planet carrier 113, this planet carrier comprising a cage 120 and a cage carrier 122 connected by flexible connections here with ball joints.

[0037] The cage 120 comprises two radial annular 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 walls 136, 138.

[0038] The cylindrical wall 140 is here of the double-skin type and comprises an external skin 140a interrupted by the slots 143 and an internal skin 140b interrupted by the same slots 143. In the example shown, which is not limiting, the external skin 140a separated by five slots 143 forms five external or external bridges 140a1, and the internal skin 140b separated by five slots 143 forms five internal or internal bridges 140b1. Each pair or couple of internal and external bridges 140a1, 140b1 form a yoke to accommodate one of the fingers 182 of the cage holder 122. In other words, the bridges 140a1, 140b1 of each pair define between them a housing 180 for receiving a finger 182 of the cage holder 122. The bridges 140a1, 140b1 of each pair are aligned radially and define between them this housing.

[0039] Alternatively, the cylindrical wall 140 could be single-skinned and each of the bridges 140a1, 140b1 could be hollowed out to form one of said housings 180.

[0040] The bridges 140a1, 140b1 provide the structural connection between the walls 136 and 138. The housings 180 open onto the walls 136 and 138, the fingers 182 being engaged in the housings 180 by the openings in the wall 136 in the example shown.

[0041] The cage 120 thus comprises an annular row of housings 180. These housings 180 receive the axial fingers 182 secured to a substantially radial annular wall 182a of the cage holder 122. The wall 182a is located at an axial end of the cage holder 122. The cage holder 122 comprises a tubular portion 122a which comprises means for coupling to a shaft, and for example to the fan shaft 4. These coupling means, not shown, are for example external splines.

[0042] The fingers 182 extend axially from the wall 182a and are engaged by axial translation in the housings 180. Each finger 182 comprises, substantially in its middle, a ring 184 for mounting the ball joint 186 intended to be crossed by a cylindrical pin 188 carried by the cage 120.

[0043] The ring 184 has a substantially radial orientation relative to the axis X. It has a generally cylindrical shape. The cage 120 and the ball joint 186 have a thickness, measured in a radial direction relative to the axis X, which is less than the inter-bridge distance or the radial thickness of the oblong slot 180, so as to be able to be engaged in this housing concomitantly with the finger 182 supporting these parts.

[0044] Each housing 180 is crossed by a pin 188 which has a substantially radial orientation relative to the axis X. 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 here engaged by radial translation from the inside through radial orifices 141, 143 of the bridges 140a1, 140b1 and of the ball joint 186, its collar 188b being intended to come into radial support on the external bridge 140a1 of the cage 120 in the example shown. After insertion of the pin 188 into the orifices of the bridges, until the collar 188b is pressed against the external bridge 140a1, the collar 188b is fixed to this bridge for example by screwing.

[0045] The walls 136, 138 define between them and with the bridges 140a1, 140b1 an internal cavity of the cage which is configured to receive the solar and the satellites of the reducer.

[0046] At their centers, the walls 136, 138 include apertures 190 aligned with the axis for mounting the solar. Around this aperture 190, each of the walls 136, 138 includes apertures 192 for mounting the ends of the guide bearings of the satellites which are inserted into the cavity by the lights 143.

[0047] The mounting of the solar and satellites in a single-piece satellite carrier cage as shown in figures 3 to 5 is not always possible and the invention provides a solution to this problem with a planet carrier cage which is formed by assembling two parts.

[0048] In the following description, the elements already described in the above are designated by the same references increased by another hundred.

[0049] THE figures 6 And 7 show an embodiment of a cage 220 and its parts 220a, 220b for a planet carrier 213 according to the invention. The figure 6 shows in part this planet carrier 213 which is part of a speed reducer for an aircraft turbomachine.

[0050] The preceding description, relating to the turbomachine 1, the reducer 10, and the planet carrier 113 applies to the planet carrier 213 and the reducer of the present invention.

[0051] The planet carrier 213 comprises a cage 220 and a cage carrier 222 connected by links which allow at least one or two degrees of freedom and which are for example ball joints, as mentioned above. The cage carrier 222 is similar to the cage carrier 112 described above and differs from it for example by the number of its fingers 282 which is three in the case of the cage carrier 222, against five in the case of the cage carrier 122.

[0052] The pin connections 288 and ball joints 286 may be similar to those described above.

[0053] The cage holder 222 comprises a tubular portion 222a which comprises means for coupling to a shaft, and for example to the fan shaft 4. These coupling means, not shown, are for example external splines.

[0054] The cage 220 comprises two radial annular walls 236, 238 which are parallel to each other and perpendicular to the X axis, as well as a cylindrical wall 240 which extends between the external peripheries of these walls 236, 238.

[0055] The cylindrical wall 240 is here of the double-skin type and comprises an outer skin 240a interrupted by the slots 243 and an inner skin 240b interrupted by the same slots 243. In the example shown, which is not limiting, the outer skin 240a separated by three slots 243 forms three outer or external bridges 240a1, and the inner skin 240b separated by three slots 243 forms three inner or internal bridges 240b1. Each pair or pair of inner and outer bridges 240a1, 240b1 forms a yoke for receiving one of the fingers 282 of the cage holder 222. In other words, the bridges 240a1, 240b1 of each pair define between them a housing 280 for receiving a finger 282 of the cage holder 222.

[0056] Alternatively and as mentioned above, the cylindrical wall 240 could be of the single-skin type and the housings 280 would then be hollowed out or formed in the bridges.

[0057] The bridges provide the structural connection between the walls 236 and 238. Elongated or oblong shaped slots are made in or between the bridges 240a1, 240b1 to receive the fingers 282.

[0058] The wall 236 located on the side of the cage holder 222 comprises an external lateral face 236a and an internal lateral face 236b which faces the other wall 238. This other wall 238 comprises an internal lateral face 238b which faces the wall 236, and an external lateral face 238a. The housings 280 pass axially through the cage 220 and open onto the faces 236a, 238a. The walls 236, 238 comprise axially passing openings 290 which are axially aligned with each other and on the axis X.

[0059] The walls 236, 238 comprise axially passing through openings 292 which are axially aligned with axially passing through openings 292 of the other of the walls. These openings 292 are distributed around the axis X and are intended to receive the axial ends of the bearings (not shown) for guiding the satellites of the reducer, which may be plain bearings or rolling bearings for example.

[0060] As is clearly visible in the figures 6 And 7 , the cage 220 comprises a first part 220a and a second part 220b which are fixed together by clamping.

[0061] The first part 220a comprises the wall 236 and the bridges 240a1, 240b1, and in particular all of the bridges. These bridges 240a1, 240b1 project axially from the face 236b of the wall 236 and comprise first axial ends 293 connected to this face and second free axial ends 294.

[0062] The second part 220b comprises the wall 238 whose face 238b is applied axially to the free ends 294 of the bridges 240a1, 240b1.

[0063] The free ends 294 of the bridges 240a1, 240b1 each comprise a radial face onto which the housings 280 open. These faces of the bridges 240a1, 240b1 thus comprise outlets 280b of the housings 280. These housings 280 are partly formed in the wall 236 which for this purpose comprises through openings 280a aligned with the outlets of the housings 280. The transverse shapes and dimensions of the openings 280a are therefore similar to those of the housings 280.

[0064] The fixing means are screws 299 which are visible at the figure 6 The screws are mounted through through holes 295 of the wall 238, on the side of the face 238a, and are screwed into tapped holes 296 of the free ends 294 of the bridges 240a1, 240b1.

[0065] As seen in the drawings, the orifices 295 are distributed around the openings 280b. Their number is between 5 and 30 per pair of bridges 240a1, 240b1 and preferably between 10 and 20 per bridge. A portion of the orifices 295 is located radially outside the outlets 280b and another portion of the orifices 295 is located radially inside these outlets 280b.

[0066] Similarly, the tapped holes 296 are distributed around the openings 280a formed in the wall a. Their number is equal to the number of the orifices 295.

[0067] It is also noted that the connecting plane of the parts 220a, 220b is offset relative to the median plane of the cage 220 which passes at the level of the axes of the pins 288.

[0068] Preferably, the tapped holes 296 extend from the free ends 294 of the bridges to before this median plane, as visible in the figure 6 .

[0069] When assembling the cage 220, the parts 220a, 220b are brought axially closer to each other until they are in contact with each other. The holes 295 of the part 220b must be aligned with the tapped holes 294 of the part 220a. To ensure precise centering of the parts 220a, 220b relative to each other, at least one of the parts may comprise centering members configured to cooperate with the other of the parts.

[0070] Preferably, the centering members comprise curved edges 297 which are carried by one of the parts and which extend around the X axis, these curved edges 297 being configured to cooperate with curved surfaces 298 of the other of the parts.

[0071] In the example shown in figures 6 And 7, the curved edges 297 are carried by the part 220a and are protrusions which extend axially in projection at the level of the free ends 294 of the bridges 240a1, 240b1, and more particularly at the level of the radially external ends of the external bridges 240a1.

[0072] Each of the external bridges 240b1 thus comprises a curved rim 297 projecting axially oriented on the side of the other part 220b. Each of these rims 297 is intended to cooperate by axial sliding with a complementary surface 298 of the part 220b and its wall 238.

[0073] In the example shown, each of the rims 297 has an angular extent around the X axis of between 20 and 70°, and preferably between 30 and 50°. Each of the surfaces 298 has an angular extent around the X axis of between 20 and 70°, and preferably between 30 and 50°.

[0074] In the embodiment shown in figures 8 And 9, the curved edges 297 are carried by the part 220b and project from its face 238b.

[0075] These edges 297 are intended to cooperate by axial sliding with complementary surfaces 298 of the free ends 294 of the bridges 240a1, 240b1, and more particularly at the level of the radially internal ends of the internal bridges 240b1.

[0076] In the example shown, each of the edges 297 has an angular extent around the X axis of between 10 and 60°, and preferably between 20 and 40°. Each of the surfaces 298 has an angular extent around the X axis of between 10 and 60°, and preferably between 20 and 40°.

[0077] In operation, the curved edges 297 are configured to cooperate by radial support with the curved surfaces 298 to allow, if necessary, part of the transmission of forces in the radial direction between the parts 220a, 220b. A major part of these forces is transmitted via the screws 299.

[0078] In yet another variant not shown, centering members could be carried by the two parts 220a, 220b or at least one of the parts of the cage 220 could comprise two types of rims 297 such as those of the variant embodiments of the figures 6 , 7 And 8 , 9 .

Claims

1. A planet carrier (213) for a speed reducer (10) of an aircraft turbomachine (1), this planet carrier (213) comprising: - a cage carrier (222) with a main axis (X) and comprising a coupling segment (222a) centred on this axis (X) and which has axial cage support fingers (282) distributed around the axis (X), - a cage (220) centred on the axis (X) and comprising two radial annular walls (236, 238) connected to each other by bridges (240a1, 240b1) distributed around the axis (X), the bridges (240a1, 240b1) being located at the external periphery of the walls (236, 238) and delimiting with the walls (236, 238) an internal cavity of the cage (220), the bridges (240a1, 240b1) comprising or defining axial housings (280) in which the fingers (282) are mounted, the fingers (282) being connected to the bridges (240a1, 240b1) by connections allowing at least one degree of freedom, one of the walls (236) comprising axially through openings (292) which are axially aligned with axially through openings (292) of the other of the walls, characterised in that the cage (220) comprises two parts (220a, 220b): - a first part (220a) comprising one of the walls (236) and the bridges (240a1, 240b1), these bridges (240a1, 240b1) projecting axially from a face (236a) of this wall (236) and comprising first axial ends (293) connected to this face (236a) and second free axial ends (294), and - a second part (220b) comprising the other of the walls (238), this wall (238) comprising a face (238a) to which the free ends (294) of the bridges (240a1, 240b1) are applied, and in that the two parts (220a, 220b) of the cage (220) are attached together by attachment means (299) which pass through the wall (238) of the second part (220b) and are inserted in attachment holes (296) in the bridges (240a1, 240b1).

2. The planet carrier (213) according to claim 1, wherein at least one of the parts (220a, 220b) of the cage (220) comprises members for centring the parts, in order to ensure a centring of the parts with respect to each other and on the axis (X).

3. The planet carrier (213) as claimed in claim 2, wherein the centring members comprise curved edges (297) which are carried by one of the parts (220a, 220b) and which extend around the axis (X), these curved edges (297) cooperating with curved surfaces (298) of the other of the parts.

4. The planet carrier (213) as claimed in claim 3, wherein the curved edges (297) are protuberances which project axially.

5. The planet carrier (213) as claimed in claim 3 or 4, wherein said curved edges (297) are suitable to axially engage by sliding or to radial abutment with the curved surfaces.

6. The planet carrier (213) according to one of claims 2 to 5, wherein the first part (220a) comprises centring members which are located on the free ends (294) of the bridges (240a1, 240b1), at their radially internal and / or external ends.

7. The planet carrier (213) according to one of claims 2 to 6, wherein the second part (220b) comprises centring members which are located on said face (238b) of its wall (238).

8. The planet carrier (213) according to one of the preceding claims, wherein the free end (294) of each of the bridges (240a1, 240b1) comprises a face bearing on the aforementioned face (238b) of the wall (238) of the second part (220b), the housing (280) of each bridge (240a1, 240b1) opening onto this bearing face, and said orifices (296) for attaching the bridges (240a1, 240b1) being distributed around the opening of this housing (280).

9. The planet carrier (213) according to one of the preceding claims, wherein the wall (238) of the second part (220b) comprises axial holes which pass through the wall (238) and are aligned with the housings (280) of the bridges (240a1, 240b1), the wall (238) of the second part (220b) comprising axial orifices (295) through which the attachment means (299) pass and which are distributed around these holes.

10. The planet carrier (213) according to one of the preceding claims, wherein the first part (220a) is located on the side of the coupling segment (222a) of the cage carrier (222).

11. The planet carrier (213) according to one of the preceding claims, wherein the attachment means are screws and the attachment holes are tapped to receive the screws by screwing.

12. A speed reducer (10) for an aircraft turbomachine (1), this reducer (10) having a main axis and comprising: - a planet carrier (213) according to one of the preceding claims, - a sun gear (11) located in the internal cavity of the cage (220) and centred on the axis (X), - planet gears (12) arranged in the internal cavity around the axis (X) and the sun gear (11) and meshed with the sun gear (11), these planet gears (12) being centred and guided by bearings (8), the axial ends of which are mounted in the aforementioned openings (292) in the walls, and - a ring gear (14) arranged around the axis (X) and the cage (220) and meshed with the planet gears (12).

13. A turbomachine (1), in particular for an aircraft, comprising a reducer (10) according to the preceding claim.