CROWN GEAR FOR A MECHANICAL REDUCTION GEAR ON AN AIRCRAFT TURBOMACHINE

Abstract

A ring gear (9) for a mechanical gearbox (6) of an aircraft turbomachine (1), comprising two independent half-rings (9a, 9b), each having an external half-flange (9ab, 9bb), the external half-flanges (9ab, 9bb) of the two half-rings (9a, 9b) being fixed to each other by screws passing through orifices (9e) in the half-flanges (9ab, 9bb), oil passages being located between the half-flanges (9ab, 9bb), characterized in that it further comprises an oil passage ring (30) which is independent of the half-rings (9a, 9b) and which is interposed between the half-flanges (9ab, 9bb) of the half-rings (9a, 9b), the ring (30) having orifices (30e) aligned with the orifices (9e) of the half-flanges (9ab, 9bb) for the passage of said screws, and in that said passages are formed in said ring (30). Abbreviated figure: figures 7a

Description

Title of the invention: CROWN GEAR FOR A MECHANICAL REDUCER OF AN AIRCRAFT TURBOMACHINE Technical field of the invention

[0001] The invention relates to a ring gear for a mechanical gearbox of an aircraft turbomachine, as well as a mechanical gearbox comprising such a ring gear. Technical background

[0002] The state of the art includes in particular the documents WO-A1-2010 / 092263, FR-A1-2 987 416 and FR-A1-3 041 054.

[0003] 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.

[0004] New generations of turbofan engines, particularly those with a high bypass ratio, include a mechanical gearbox to drive the shaft of a fan. Typically, the purpose of the gearbox is to transform the high rotational speed of the power turbine shaft into a slower rotational speed for the fan-driving shaft.

[0005] 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 a 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, equally spaced on the same operating diameter around the axis of the planet gears. These axes are parallel to the longitudinal axis of the turbomachine.

[0006] Several gearbox architectures exist. In the state of the art of turbofan engines, gearboxes are of the planetary or epicyclic type. In other similar applications, there are so-called differential or "compound" architectures. - 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. - 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. - On a differential gearbox, no element is fixed in rotation. The ring rotates in the opposite direction to the solar and satellite carrier.

[0007] Reducers can be composed of one or more meshing stages. This meshing is achieved in various ways such as by contact, by friction, or by magnetic field.

[0008] There are several types of contact meshing such as with straight or herringbone teeth.

[0009] The operation of gearboxes requires a particularly high oil flow rate to ensure the lubrication and cooling of their mechanical components. However, this type of gearbox has drawbacks related to its lubrication, and in particular to the removal of the lubricating oil.

[0010] In document FR-A1-3 084 427, the Applicant proposed means for evacuating lubricating oil which include an annular row of oil passages extending radially through the flange of the crown and configured to allow oil to flow radially outwards from this flange.

[0011] The crown comprises two half-crowns which have half-flanges assembled to form the crown flange. These half-flanges have through holes for mounting screws or bolts for fixing the half-flanges.

[0012] The oil passages include lunules formed in radial bearing faces of the half-flanges and extending radially over the entire height of these half-flanges.

[0013] The formation of these oil passages requires the machining of the lunules in the half-flanges of the half-crowns, during a complex and relatively costly operation.

[0014] The present invention proposes an improvement to this technology, which is simple, efficient and economical. Summary of the invention

[0015] To this end, the invention proposes a ring gear for a mechanical gearbox of an aircraft turbomachine, this ring gear having an annular shape around an axis and comprising internal annular teeth oriented towards the axis and an external annular flange oriented radially outwards from the axis, the ring gear comprising two independent half-rings, each comprising a portion of the internal teeth and an external half-flange, the external half-flanges of the two half-rings together forming the flange of the ring gear and being fixed to each other by screws parallel to the axis and passing through aligned orifices in the half-flanges, oil passages being oriented radially with respect to the axis being located between the half-flanges and regularly distributed around the axis, characterized in that it further comprises an oil passage ring that is independent of the half-rings and that is interposed between the half-flanges of the half-crowns,the ring having orifices aligned with the orifices of the half-flanges for the passage of said screws, and in that said oil passages are formed in said ring.

[0016] The invention thus proposes to form the oil passages through the crown, in A ring is inserted between the half-flanges of the half-crowns. This eliminates the need to create passages within the half-flanges, making them simpler and more economical to manufacture. The ring is designed for oil drainage and is sized and engineered to perform this function.

[0017] The solution proposed below is compatible with single-stage or multi-stage gearboxes. It is compatible with epicyclic, planetary, or differential gearboxes. It is compatible with spur, helical, or herringbone gears. It is compatible with all types of planet carriers, whether monobloc or cage-and-cage type. It is compatible with all types of planetary bearings, whether composed of rolling elements, hydrodynamic bearings, etc.

[0018] The crown according to the invention may comprise one or more of the following features, taken individually or in combination with each other: - the oil passages are formed by channels formed inside the ring, lunules or slits formed on sides of the ring, and / or alveolar or lattice portions of the ring; it is understood that the alveolar or lattice portions of the ring include open cells which communicate with each other to allow the passage of oil between the cells and through these portions; - the ring comprises a first annular face bearing on one of the half-flanges, and a second annular face bearing on the other of the half-flanges, the orifices of the ring opening onto these first and second faces, the ring further comprising a radially internal annular edge and a radially external annular edge; - the internal channels are formed in the middle of the ring, away from its first and second faces, and open onto the inner and outer edges of the ring; - the lunules or slits are formed on at least one of the first and second faces of the ring; - the lunules or slits extend over the entire radial dimension of the ring; - the ring's openings are formed in rigid blocks that are distributed around the axis and which are joined together by an annular alveolar or lattice structure of the ring, the alveolar or lattice portions of this structure located between the blocks forming said oil passages; - the blocks are all identical and have a diamond shape for example; - Danneau_int is between 0.9.Dbride_int and l.l.Dbride_int and Danneau_ext is between 0.9.Dbride_ext and l.l.Dbride_ext, Danneau_int and Danneau_ext being respectively the internal and external diameters of the ring, and Dbride_int and Dbride_ext being respectively the internal and external diameters of the crown flange.

[0019] The present invention also relates to a mechanical reducer for an aircraft tur-bomachine, comprising a ring as described above, a sun centered on the axis of the ring and surrounded by the ring, and satellites mounted between the sun and the ring and meshed with the sun and the ring. Brief description of the figures

[0020] 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:

[0021] [Fig-1] [Fig.1] is a schematic axial cross-sectional view of a turbomachine aircraft,

[0022] [Fig.2] [Fig.2] is a partial schematic axial cross-sectional view of a mechanical reducer,

[0023] [Fig.3] [Fig.3] is a partial schematic axial cross-sectional view of a mechanical reducer,

[0024] [Fig.4] [Fig.4] is a schematic cross-sectional and perspective view of the reducer of [Fig.3],

[0025] [Fig.5] [Fig.5] is a partial schematic view of a ring of the reducer of [Fig.3],

[0026] [Fig.6] [Fig.6] is a partial schematic view of a half-flange of a half-crown of the reducer of [Fig.3],

[0027] [Fig.7a] [Fig.7a] is a schematic half-view in axial section of a crown according to an embodiment of the invention,

[0028] [Fig.7b-7c] Figures 7b and 7c are views similar to that of [Fig.7a] and illustrate other embodiments of the invention,

[0029] [Fig.8] [Fig.8] is a schematic perspective view of a ring according to a first embodiment,

[0030] [Fig.9a] [Fig.9a] is another schematic perspective view of the ring of [Fig.8],

[0031] [Fig.9b] [Fig.9b] is a larger scale view of part of [Fig.9a],

[0032] [Fig. 10a] [Fig. 10a] is a schematic perspective view of a ring according to a second embodiment,

[0033] [Fig. 10b] [Fig. 10b] is a larger scale view of part of [Fig. 10a],

[0034] [Fig.lia] [Fig.lia] is a schematic perspective view of a ring along a third embodiment,

[0035] [Fig. 11b] [Fig. 11b] is a larger scale view of part of [Fig. 11a]. Detailed description of the invention

[0036] Figure 1 describes a turbomachine 1 which conventionally comprises a fan S, a low-pressure compressor 1a, a high-pressure compressor 1b, an annular combustion chamber 1e, a high-pressure turbine Id, a low-pressure turbine 1e, and an exhaust nozzle Ih. The high-pressure compressor 1b and the high-pressure turbine Id 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.

[0037] The blower S is driven by a blower shaft 4 which is connected to the BP shaft 3 by means of a reducer 6. This reducer is generally of the planetary or epi-cycloidal type.

[0038] Although the following description relates to a planetary or epi-cycloidal 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 rotational speed of one of these components depending in particular on the difference in speeds of the other two components.

[0039] The reducer 6 is positioned in the front part of the turbomachine. A fixed structure schematically comprising, here, an upstream part 5a and a downstream part 5b which make up the motor or stator housing 5 is arranged to form an enclosure E surrounding the reducer 6. This enclosure E is here closed upstream by seals at the level of a bearing allowing the passage of the blower shaft 4, and downstream by seals at the level of the passage of the BP shaft 3.

[0040] Figure 2 shows part of a gearbox 6 which can take the form of different architectures depending on whether certain parts are fixed or rotating. At the input, the gearbox 6 is connected to the shaft BP 3, for example via splines 7a. Thus, the shaft BP 3 drives a planetary gear called the sun gear 7. Conventionally, the sun gear 7, whose axis of rotation coincides with the X-axis of the turbomachine, drives a series of gears called planet gears 8, which are equally spaced on the same diameter around the X-axis of rotation. This diameter is equal to twice the operating center distance between the sun gear 7 and the planet gears 8. The number of planet gears 8 is generally defined between three and seven for this type of application.

[0041] The set of satellites 8 is held by a frame called a satellite carrier 10. Each satellite 8 rotates around its own Y axis, and meshes with the ring 9.

[0042] At the output of the reducer, we have: • In an epicycloidal configuration, the set of satellites 8 drives in rotation of the planet carrier 10 around the X axis of the turbomachine. The ring gear 9 is fixed to the motor housing or stator 5 via a ring carrier 12 and the planet carrier 10 is fixed to the blower shaft 4. • In a planetary configuration, the set of satellites 8 is held by a satellite carrier 10 which is fixed to the motor or stator housing 5. Each satellite 8 drives the ring 9 which is connected to the blower shaft 4 via a ring carrier 12.

[0043] Each satellite 8 is mounted to rotate freely by means of a bearing 11, for example, a roller bearing or a hydrostatic bearing. Each bearing 11 is mounted on one of the axes 10b of the satellite carrier 10, and all the axes are positioned relative to each other by means of one or more structural frames 10a of the satellite carrier 10. There is a number of axes and bearings equal to the number of satellites. For reasons of operation, assembly, manufacturing, inspection, repair, or replacement, the axes 10b and the frame 10a may be separated into several parts.

[0044] The teeth of a reducer can be separated into several helices.

[0045] The crown 9 is separated into two half-crowns 9a, 9b: • a front half-crown 9a consisting of a rim 9aa and a mounting flange half 9ab. On the rim 9aa is the front helix of the reduction gear teeth. This front helix meshes with that of the satellite 8, which meshes with that of the solar 7. • a rear half-crown 9b consisting of a rim 9ba and a mounting flange half 9bb. The rear helix of the reduction gear teeth is located on the rim 9ba. This rear helix meshes with that of the satellite 8, which meshes with that of the solar 7.

[0046] The mounting bracket 9ab of the front half-crown 9a and the mounting bracket 9bb of the rear half-crown 9b form the mounting bracket 9c of the crown 9. The crown 9 is attached to the crown carrier 12 by joining the mounting bracket 9c of the crown and the mounting bracket 12a of the crown carrier using, for example, a bolted assembly. In what follows, a half-bracket may be referred to as a bracket.

[0047] The arrows in [Fig. 2] describe the oil flow in the gearbox 6. The oil enters the gearbox 6 from the stator section 5 into the distributor 13 by various means, which will not be specified in this view because they are specific to one or more types of architecture. The distributor 13 is divided into two parts, each generally repeated with the same number of planetary gears. The injectors 13a lubricate the gear teeth, and the arms 13b lubricate the bearings 11. The oil is supplied to the injector 13a and exits through the end 13c to lubricate the gear teeth. The oil is also supplied to each arm 13b and circulates via the supply mouth 13d of the bearing 11. The oil then circulates through the shaft 10b into one or more buffer zones 10c and then exits through orifices lOd to ​​lubricate the bearings 11 of the satellites.

[0048] In the examples shown in Figures 3 and 4, each axis 10b is surrounded by two bearings 17a, 17b, which are roller bearings in the example shown. The bearings 17a, 17b are coaxial and arranged side by side, each bearing being located in a median plane PI, P2 passing substantially through the median plane of a gear or helix 8d of the satellite 8 and through the median plane of a gear or helix 9d of a half-ring 9a, 9b. The planes PI and P2 are parallel to each other and perpendicular to the X and Y axes. The number of bearings 17a, 17b may differ from the example shown. It does not necessarily depend on the number of helices 8d, 9d.

[0049] Each satellite 8 has an internal bearing raceway. To reduce the precise machining area to the required size, this internal cylindrical surface is divided into several raceways of reduced axial width, the number of which is equal to the number of bearings 17a, 17b. This allows for an annular oil recovery groove 8e between the raceways, reduces the mass because the satellite is subjected to less stress in this area, and simplifies the manufacturing process for components requiring very high precision because several raceways are machined independently of each other, and the total high-precision surface area is smaller with the grooves between each raceway. An annular row of radial holes 19 is formed at the bottom of this groove 8e and allows, during operation, the flow of lubricating oil from the bearings to an annular space E2 located between the two half-rings 9a, 9b.

[0050] The flange 12a of the crown carrier 12 is applied axially to one side of the flange 9c, namely the upstream side in the example shown. The crown carrier 12 is axially centered on the crown 9 by means of a cylindrical flange 12ab located on the outer periphery of the flange 12a (Figures 3 and 4). Once positioned, the crown carrier 12 extends around the crown 9 (or the half-crown 9a in our example), and the area delimited between these two parts defines the annular space El for oil circulation.

[0051] An annular oil catch can 22 surrounds the half-ring 9b and includes an annular flange 22a for mounting on the flange 9c of the ring 9. The flange 22a is applied axially to one side of the flange 9c, namely the downstream side in the example shown. The oil catch can 22 is axially centered on the ring 9 by means of a cylindrical rim 22ab located on the outer periphery of the flange 22a ([Fig. 4]). The area delimited between the catch can 22 and the ring 9 defines the annular space E3 for oil circulation.

[0052] To ensure that it remains in position, the flanges 9ab, 9bb of the crown 9 and the flanges 12a, 22a of the crown carrier 12 and the receptacle 22 include respec tively an annular row of through holes 9e, 12b and 22b. These through holes serve as passages for fastening means 21 of the screw-nut type or similar.

[0053] Once the crown 9, the crown carrier 12, and the collector 22 are assembled, their flanges applied to each other, the orifices 9e, 12b and 22b receive the fastening means 21 to ensure that the three elements which now form the crown assembly are held in position.

[0054] The ring gear assembly forms a fairing for the reduction gear 6. Although not sealed, the assembly's function is to capture as much oil as possible to limit its recirculation within the motor, whether fixed or moving, depending on the type of reduction gear. The oil is thus collected at three internal locations within the ring gear assembly, namely the annular spaces E1, E2, and E3, and then discharged into the annular space E4 (Figures 4 and 8), located radially outside the flanges 12a, 9c, and 22a.

[0055] The first oil passages are here formed by a first annular row of passages or, as in our example, of substantially radial lunules 25 formed in the flange 9c of the ring 9. The lunules 25 of the first row are made at a distance from the passage holes 9e of the fastening means 21.

[0056] The lunules 25 are in fluidic communication, at their radially internal ends, with the space E2, and at their axially external ends with oil outlet notches 27, 27' provided on the cylindrical rims 12ab, 22ab located at the external periphery of the flanges 12a, 22a ([Fig.4]).

[0057] Second oil passages are further formed by annular rows of passages or, as in our example, substantially radial lunules 28, 28' formed in the radial bearing surfaces of the flanges 12a, 22a ([Fig. 4]). The lunules 28, 28' are made at a distance from the passage holes 12b, 22b of the fastening means 21 and communicate with holes 29 provided at the bottom of the lunules 25 of the flanges 9ab, 9bb.

[0058] The oil flowing through the orifices lOd of the axis 10b of the planet carrier 10 (arrows fl) lubricates the bearings 17a, 17b and must then flow radially outward from them. This is also the case for the lubricating oil of the gearbox gears. The gearbox lubricating oil can follow several paths as illustrated by arrows f2 to f5.

[0059] In the case shown in figures 5 and 6, the oil evacuation lunules 25 through the flange 9c are formed directly in the radial faces supporting the half-flanges 9ab, 9bb of the half-crowns 9a, 9b.

[0060] The invention proposes an improvement to this technology, embodiments of which are shown in figures 7a to 7c and detailed in the following figures.

[0061] Generally, the crown 9 has an annular shape around the X axis and includes an internal annular toothing 9d oriented towards the X axis and an external annular flange 9c oriented radially outwards from the X axis.

[0062] The crown 9 comprises two half-crowns 9a, 9b independent of each other and each comprising a part of the internal teeth 9d and an external half-flange 9ab, 9bb.

[0063] The external half-flanges 9ab, 9bb of the two half-crowns 9a, 9b together form the flange 9c of the crown 9 and are fixed to each other by fastening means 21 of the screw-nut type or similar which are parallel to the axis X and which pass through aligned orifices 9e of the half-flanges 9ab, 9bb.

[0064] Oil passages are located between the half-flanges 9ab, 9bb and regularly distributed around the X axis. These oil passages are oriented radially with respect to the X axis for the evacuation of the lubricating oil from the reducer radially outwards.

[0065] According to the invention, the crown 9 further comprises an oil passage ring 30 which is independent of the half-crowns 9a, 9b and which is intercalated between the half-flanges 9ab, 9bb of the half-crowns 9a, 9b.

[0066] The ring 30 has orifices 30e aligned with the orifices 9e of the half-flanges 9ab, 9bb for the passage of the fastening means 21.

[0067] The aforementioned passages are formed in this ring 30 and figures 7a to 7c show three variants of the embodiment of the ring 30 and of these passages.

[0068] The passages can be formed:

[0069] - by channels 32 formed inside the ring 30 as illustrated in the [Fig.7a], and / or

[0070] - by alveolar or lattice portions 34 of the ring 30 as illustrated in figure 7b, and / or

[0071] - by crescents 36 or slits formed on sides of the ring 30 as is illustrated in figure 7c.

[0072] In all these embodiments, it is observed that the ring 30 preferably comprises a first annular face 30a bearing on one of the half-flanges 9ab, and a second annular face 30b bearing on the other of the half-flanges 9bb. The orifices 30e of the ring 30 open onto these faces 30a, 30b.

[0073] The ring 30 further comprises a radially internal annular edge 30c and a radially external annular edge 30d.

[0074] Danneau_int and Danneau_ext are defined respectively as the internal and external diameters of the ring 30, which can be measured at the edges 30c and 30d, respectively.

[0075] The internal diameters are further defined by Dbride_int and Dbride_ext respectively and external of the 9c bridle of the crown 9 (and of each of the half bridles 9ab, 9bb).

[0076] Preferably, Danneau_int is between 0.9.Dbride_int and l.l.Dbride_int and Danneau_ext is between 0.9Dbride_ext and l.lDbride_ext. This means that the ring 30 preferably has radial dimensions close to those of the flange 9c, or even identical to those of the flange 9c, as can be seen in the drawings.

[0077] Reference is now made to figures 8, 9a and 9b which illustrate a more concrete example of the realization of a ring 30 having lunes 36 or slits formed on sides of the ring 30, as in figure 7c.

[0078] The lunules 36 or slits are formed on at least one of the first and second faces 30a, 30b of the ring 30. In the example shown, they are formed on only one of these faces 30a, 30b. The number of lunules 36 is equal to the number of orifices 30e. Each lunule 36 is located between two adjacent orifices 30e and each orifice 30e is located between two adjacent lunules 36.

[0079] In the example shown, the lunules 36 or slits extend over the entire radial dimension of the ring 30 and thus open onto the edges 30c, 30d of the ring 30.

[0080] Each of the lunules 36 can have a general parallelepiped shape as in the example shown and have an elongated shape in the radial direction.

[0081] The lunules 36 of the ring 30 can be made by machining, for example. Their dimensions and number depend in particular on the volume of oil to be evacuated during operation.

[0082] Reference is now made to figures 10a and 10b which illustrate a more concrete example of the realization of a ring 30 comprising alveolar or lattice portions 34, as in figure 7b.

[0083] The orifices 30e of the ring are preferably formed in rigid blocks 38 which are distributed around the axis X and which are joined together by an annular alveolar or lattice structure 40 of the ring 30.

[0084] The alveolar or lattice portions 34 of this structure 40 comprise open cells that communicate with each other to allow the passage of oil between the cells and through these portions. The alveolar or lattice portions 34 are located between the blocks 38 and thus form the aforementioned passages.

[0085] The blocks 38 can all be identical and have a rhombus shape, for example, as in the example shown. Due to this rhombus shape, each of the portions 34 in the example shown has a convergent shape and then a divergent shape as it moves radially outwards from the axis.

[0086] The number of blocks 38 is preferably equal to the number of orifices 30e. Each portion 34 is arranged between two adjacent orifices 30e and therefore two blocks 38, and each orifice 30e and each block 38 is arranged between two adjacent portions 34.

[0087] The blocks 38 can extend over only a part of the radial dimension of ring 30 or over the entire radial extent of ring 30.

[0088] The ring 30, and in particular its structure 40 and / or its blocks 38, can be produced by additive manufacturing. With this configuration, the ring 30 can also have a function of separating air from oil, the passage of oil through the structure 40 facilitating this separation.

[0089] Reference is now made to figures 1a and 11b which illustrate a more concrete example of the realization of a ring 30 having channels 32 formed inside the ring 30, as in [Fig.7a].

[0090] In the example shown, the internal channels 32 are formed in the middle of the ring 30, at a distance from its faces 30a, 30b. The channels 32 open onto the edges 30c, 30d of the ring 30.

[0091] The channels 32 can have any shape in cross-section and for example oval as in the example shown.

[0092] The number of channels 32 is preferably equal to the number of orifices 30e. Each channel 32 is arranged between two adjacent orifices 30e, and each orifice 30e is arranged between two adjacent channels 32.

[0093] The channels 32 of the ring 30 can be made by machining, for example. Their dimensions and number depend in particular on the volume of oil to be evacuated during operation.

Claims

Demands

1. A ring gear (9) for a mechanical gearbox (6) of an aircraft turbomachine (1), said ring gear (9) having an annular shape about an axis (X) and comprising an internal annular toothing (9d) oriented towards the axis (X) and an external annular flange (9c) oriented radially outwards from the axis (X), the ring gear (9) comprising two independent half-rings (9a, 9b) each comprising a portion of the internal toothing (9d) and an external half-flange (9ab, 9bb), the external half-flanges (9ab, 9bb) of the two half-rings (9a, 9b) together forming the flange (9c) of the ring gear (9) and being fixed to each other by screws which are parallel to the axis (X) and which pass through aligned orifices (9e) of the half-flanges (9ab, 9bb), oil passages oriented radially with respect to the axis (X) being located between the half-flanges (9ab, 9bb) and regularly distributed around the axis (X),characterized in that it further comprises an oil passage ring (30) which is independent of the half-crowns (9a, 9b) and which is interposed between the half-flanges (9ab, 9bb) of the half-crowns (9a, 9b), the ring (30) having orifices (30e) aligned with the orifices (9e) of the half-flanges (9ab, 9bb) for the passage of said screws, and in that said oil passages are formed in said ring (30).

2. Crown (9) according to claim 1, wherein the oil passages are formed by channels (32) formed inside the ring (30), lunules (36) or slots formed on sides of the ring (30), and / or alveolar or lattice portions (34) of the ring (30).

3. Crown (9) according to claim 1 or 2, wherein the ring (30) comprises a first annular face (30a) bearing on one of the half-flanges (9ab), and a second annular face (30b) bearing on the other of the half-flanges (9bb), the orifices (30e) of the ring (30) opening onto these first and second faces (30a, 30b), the ring (30) further comprising a radially internal annular edge (30c) and a radially external annular edge (30d).

4. Crown (9) according to claims 2 and 3, wherein the internal channels (32) are formed in the middle of the ring (30), at a distance from its first and second faces (30a, 30b), and open onto the internal and external edges (30c, 30d) of the ring (30).

5. Crown (9) according to claims 2 and 3, wherein the lunules (36) or slots are formed on at least one of the first and second faces (30a, 30b) of the ring (30).

6. Crown (9) according to claim 5, wherein the lunules (36) or slots extend over the entire radial dimension of the ring (30).

7. Crown (9) according to claims 2 and 3, wherein the orifices (30e) of the ring (30) are formed in rigid blocks (38) which are distributed around the axis (X) and which are joined together by an annular structure (40) alveolar or lattice of the ring (30), the alveolar or lattice portions (34) of this structure (40) located between the blocks (38) forming said oil passages.

8. Crown (9) according to claim 7, wherein the blocks (38) are all identical and have a diamond shape, for example.

9. Crown (9) according to any one of the preceding claims, wherein Danneau_int is between 0.9.Dbride_int and l.l.Dbride_int and Danneau_ext is between 0.9.Dbride_ext and l.l.Dbride_ext, Danneau_int and Danneau_ext being respectively the internal and external diameters of the ring (30), and Dbride_int and Dbride_ext being respectively the internal and external diameters of the flange (9c) of the crown (9).

10. Mechanical reducer (6) for an aircraft turbomachine (1), comprising a ring (9) according to any one of the preceding claims, a sun (7) centered on the axis (X) of the ring (9) and surrounded by the ring (9), and satellites (8) mounted between the sun (7) and the ring (9) and meshed with the sun (7) and the ring (9).

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