PLAIN BEARING FOR A SATELLITE OF A MECHANICAL REDUCTION GEARBOX OF AN AIRCRAFT TURBOMACHINE

Abstract

Plain bearing (110) for a satellite of a mechanical gearbox (6) of a turbomachine (1), particularly an aircraft, this plain bearing (110) being formed in one piece and comprising: - a hollow cylindrical body (20b) which includes an axis (Y) and which internally defines a cavity (10c) for receiving oil, - an annular wall (20a) which extends around the axis (Y) and the hollow body (20b) and which includes an external cylindrical guide surface (25a), - an annular web (20c) which extends around the axis (Y), between the body (20b) and the wall (20a), characterized in that it includes at least one annular row of relief holes (122) in said web (20c), these holes (122) being regularly distributed around the axis (Y). Figure for the abbreviation: Figure 6

Description

Title of the invention: PLAIN BEARING FOR A SATELLITE OF A MECHANICAL REDUCER OF AN AIRCRAFT TURBOMACHINE Technical field of the invention

[0001] The present invention relates to the field of mechanical reducers for turbomachines, particularly aircraft. Technical background

[0002] The state of the art includes in particular documents FR-A1-3 071 022, FR-Al-3 095 252, FR-A1-3 071 024 and FR-A1-3 071 023.

[0003] The role of a mechanical reducer is to modify the speed and torque ratio between the input axis and the output axis of a 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 (also called a "fan"). Usually, the reducer aims to transform the so-called fast rotation speed of the shaft of a power turbine into a slower rotation speed for the shaft driving the fan.

[0005] Such a reducer comprises a central pinion, called a sun gear, a crown gear and pinions called satellites, which are engaged between the sun gear and the crown gear. The satellites are held by a frame called a planet carrier. The sun gear, the crown gear and the planet carrier are planetary gears because their axes of revolution coincide with the longitudinal axis X of the turbomachine. The satellites each have a different axis of revolution Y, they are equally distributed over the same operating diameter around the axis of the planetary gears. These Y axes are parallel to the longitudinal axis X.

[0006] There are several gearbox architectures. In the state of the art of dual-flow turbomachines, the gearboxes are of the planetary or epicyclic type. In other similar applications, there are so-called differential or "compound" architectures.

[0007] - On a planetary reducer, the planet carrier is fixed and the crown constitutes the output shaft of the device which rotates in the opposite direction of the solar.

[0008] - On an epicyclic reducer, the crown is fixed and the planet carrier constitutes the output shaft of the device which rotates in the same direction as the solar.

[0009] - On a differential reducer, no element is fixed in rotation. The crown rotates in the opposite direction of the solar and the satellite carrier.

[0010] The reducers can comprise one or more meshing stages. This meshing is ensured in different ways such as by contact, by friction or even by magnetic fields. There are several types of contact meshing such as straight or herringbone teeth.

[0011] A reducer must be lubricated and supplying lubricating oil to the rotating components of a reducer can be problematic. The oil is generally supplied to the reducer by a lubricating oil distributor.

[0012] The satellites are guided in rotation by bearings which are lubricated. The bearings may be composed of rolling elements (ball bearings, roller bearings, tapered roller bearings, etc.) or may be plain or hydrodynamic bearings. In the latter case, each satellite is rotatably mounted on and around a plain bearing, which is supplied with oil and which is configured to form an oil film between the outer periphery of the bearing and the inner periphery of the satellite. For this purpose, in the current technique, each satellite comprises an inner cylindrical surface which extends around an outer cylindrical surface of the bearing and which delimits with the latter an annular space for forming the oil film. This space is supplied with oil by oil passage orifices which are formed in the bearing and extend from the outer cylindrical surface to an inner cavity of the bearing which is supplied with oil by the aforementioned distributor.

[0013] The present application relates to a reducer whose satellites are guided by plain bearings of this type.

[0014] A plain bearing of the prior art has a shape which gives it a good compromise between sufficient rigidity to guide the satellites and sufficient flexibility to absorb part of the forces transmitted by the teeth of the satellites and avoid transmitting all of these forces to the planet carrier.

[0015] However, a plain bearing of the prior art has disadvantages related to its mass. Plain bearings are mass elements of the reducer, the number of which is generally between three and seven. In addition to having an impact on the mass of the turbomachine, these bearings orbit around the axis of the sun gear, which causes many harmful consequences such as unbalance, high amplitude vibrations and radial forces on the planet carrier, which can generate misalignments between the sun gear, the satellites and the ring gear. An orbiting bearing shears the oil, which causes losses, in particular friction losses of the bearing in the area where the oil film breaks.Hot oil cannot be evacuated through the lightly loaded side of the bearing and this hot oil not evacuated from the first rotation tends to heat the cold oil coming out of the oil passage holes, which prevents the bearing from evacuating the calories correctly.

[0016] The present invention provides a simple, effective and economical improvement for reducing the mass of a plain bearing for a mechanical reducer. Summary of the invention

[0017] The invention relates to a plain bearing for a satellite of a mechanical reducer of a turbomachine, in particular of an aircraft, this plain bearing being formed from a single piece and comprising:

[0018] - a hollow cylindrical body which comprises an axis and which internally defines a cavity intended to receive oil,

[0019] - an annular wall which extends around the axis and the hollow body and which comprises an external cylindrical guide surface,

[0020] - an annular core which extends around the axis, between the body and the wall, and which connects the body to the wall, this annular core having a length along the axis which is less than a length of the wall so that the wall delimits around the body an annular space in front of the core and an annular space behind the core, and

[0021] - oil passage holes formed in the body, the core and the wall and extending from the cavity to the guide surface,

[0022] characterized in that it comprises at least one annular row of lightening holes in said core, these holes being regularly distributed all around the axis.

[0023] The invention thus proposes to provide lightening holes in the plain bearing. The holes thus have a lightening function and this is preferably the only function of these holes. They are therefore configured to lighten, and therefore reduce the mass, of the plain bearing. The holes are located in a specific location of the plain bearing, namely its core. They are regularly distributed around the axis so that their arrangement around this axis does not meet particular criteria such as the distribution of the load around the plain bearing for example. In the prior art cited above, it has already been proposed to make holes in the core of the plain bearing. However, these holes do not have the same function and are not distributed regularly around the axis of the bearing.

[0024] The solution proposed below is compatible with an epicyclic, planetary or differential reducer. It is compatible with any type of planet carrier, whether monobloc or cage-carrier / cage type. It is compatible with a single-stage or multi-stage reducer. It is compatible with straight, helical or herringbone teeth.

[0025] The reducer according to the invention may comprise one or more of the following characteristics, taken in isolation from one another, or in combination with one another:

[0026] — the lightening holes are only made in said core;

[0027] — the lightening holes all have an essentially axial orientation, that is to say parallel or almost parallel to said axis; • the core comprises a single annular row of lightening holes which pass through the entire length of the core and open into said spaces; • the core comprises a first annular row of blind lightening holes which are formed on a first side of the core, front or rear, and which open into a first of said spaces, and a second annular row of blind lightening holes which are formed on a second opposite side of the core and which open into a second of said spaces; • the holes have a constant section along their entire length; • the holes have a section that varies along their length, each of the holes comprising for example at least two or three sections having different diameters; • the holes have a diameter D2 between 0.01.DI and 0.1.Dl, DI being the diameter of the guide surface; • the holes have a diameter D2 between 0.008.L3 and 0.1.L3, L3 being the length of the bearing measured along the axis; • the holes have a circular, oblong or elliptical cross-section; • the holes are parallel to the axis or inclined at a maximum angle of + / -10° per relation to this axis.

[0028] The invention also relates to a mechanical reducer for a turbomachine, in particular an aircraft one, this reducer comprising:

[0029] - a solar having an axis of rotation,

[0030] - a crown that extends around the solar,

[0031] - satellites which are meshed with the sun and the crown and which are each mounted on a plain bearing according to one of the preceding claims, the plain bearings being fixed to a planet carrier, and

[0032] - a lubricating oil distributor which is configured to supply oil to the cavities of said bearings.

[0033] The invention further relates to a turbomachine, in particular for an aircraft, comprising a mechanical reducer as described above. Brief description of the figures

[0034] 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:

[0035] [Fig.l] [Fig.l] is a schematic axial sectional view of a turbomachine using the invention,

[0036] [Fig.2] [Fig.2] is a partial axial sectional view of a mechanical reducer,

[0037] [Fig.3] [Fig.3] is a view similar to that of [Fig.2] and representing a mode of production of a mechanical reducer,

[0038] [Fig.4] [Fig.4] is a perspective view of a satellite plain bearing of the reducer of [Fig.3],

[0039] [Fig.5] [Fig.5] is a cross-sectional view of the plain bearing of [Fig.4],

[0040] [Fig.6] [Fig.6] is seen similar to that of [Fig.5] and illustrating a mode of rea construction of a plain bearing according to the invention,

[0041] [Fig.7] [Fig.7] is an axial sectional view of the plain bearing of [Fig.6],

[0042] [Fig.8] [Fig.8] is an axial sectional view of an alternative embodiment of a bearing smooth according to the invention,

[0043] [Fig.9] [Fig.9] is an axial sectional view of another alternative embodiment of a plain bearing according to the invention, and

[0044] [Fig. 10] [Fig. 10] is an axial sectional view of another alternative embodiment of a plain bearing according to the invention. Detailed description of the invention

[0045] [Fig.l] 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 1c 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 1c are connected by a low-pressure shaft 3 and form with it a low-pressure (LP) body.

[0046] The blower S is driven by a fan shaft 4 which is driven to the LP shaft 3 by means of a reducer 6. This reducer 6 is generally of the planetary or epicyclic type.

[0047] The following description, which is not limiting, concerns a reducer of the epicyclic type, the planet carrier s and the sun gear of which are mobile in rotation, the crown of the reducer being fixed in the frame of reference of the motor.

[0048] The reducer 6 is positioned in the upstream part of the turbomachine. In the present application, the expressions upstream and downstream refer to the general flow of gases in the turbomachine, along its axis of elongation or rotation of its rotors. 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 6. 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.

[0049] [Fig.2] shows an epicyclic reducer 6. At the input, the reducer 6 is connected to the BP shaft 3, for example by means of internal splines 7a. Thus, the BP shaft 3 drives a planetary pinion called the sun gear 7. Conventionally, the sun gear 7, whose axis of rotation is the same as that of the turbomachine X, drives a series of pinions called satellites 8, 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 7 and the satellites 8. The number of satellites 8 is generally defined between three and seven for this type of application.

[0050] All of the satellites 8 are held by a chassis called a satellite carrier 10. Each satellite 8 rotates around its own Y axis, and meshes with the crown 9.

[0051] At the output we have: In this epicyclic configuration, the set of satellites 8 rotates the planet carrier 10 around the axis X of the turbomachine. The crown is fixed to the engine casing or stator 5 via a crown carrier 12 and the planet carrier 10 is fixed to the fan shaft 4. In another planetary configuration, the set of planet gears 8 is held by a planet carrier 10 which is fixed to the engine casing or stator 5. Each planet gear drives the crown which is attached to the fan shaft 4 via a crown carrier 12.

[0052] Each satellite 8 is mounted to rotate freely using a bearing, which is a plain bearing 11 or hydrodynamic bearing in the context of the present invention. Each plain bearing 11 is fixed to the planet carrier 10 and the plain bearings 11 are distributed around the X axis and centered on the Y axes. There is a number of plain bearings 11 equal to the number of satellites. For reasons of operation, assembly, manufacturing, control, repair or replacement, the plain bearings 11 and the frame 10a of the planet carrier 10 can be separated into several parts.

[0053] For the same reasons cited above, the teeth of a reducer can be separated into several helices each having a median plane P. In our example, we detail the operation of a reducer with several helices with a crown separated into two half-crowns: An upstream half-crown 9a consisting of a rim 9aa and a fixing half-flange 9ab. On the rim 9aa is the upstream helix of the gear teeth. This upstream helix meshes with a helix of the toothing 8d of the satellite 8 which meshes with a helix of the toothing 7a of the sun gear 7. A downstream half-crown 9b consisting of a rim 9ba and a half-fixing flange 9bb. On the rim 9ba is the downstream helix of the reduction gear teeth. This downstream helix meshes with a helix of the 8d toothing of the satellite 8 which meshes with a helix of the 7a toothing of the sun gear 7.

[0054] If the helix widths vary between the sun 7, the satellites 8 and the crown 9 at Because of the tooth overlaps, they are all centered on a median plane P for the upstream propellers and on another median plane P for the downstream propellers. In the case of a double-row roller bearing, each row of rolling elements is also preferably, but not necessarily, centered on two median planes.

[0055] The fixing half-flange 9ab of the upstream crown 9a and the fixing half-flange 9bb of the downstream crown 9b form the fixing flange 9c of the crown. The crown 9 is fixed to a crown carrier by assembling the fixing flange 9c of the crown and the fixing flange 12a of the crown carrier using a bolted assembly for example.

[0056] The arrows in [Fig.2] describe the routing of the oil in the reducer 6. The oil arrives in the reducer 6 from the stator part 5 in a distributor 13 by different means which will not be specified in this view because they are specific to one or more types of architecture. The distributor 13 comprises injectors 13a and arms 13b. The injectors 13a have the function of lubricating the teeth and the arms 13b have the function of lubricating the bearings. The oil is brought towards the injector 13a to exit through the end 13c in order to lubricate the teeth. The oil is also supplied to the arm 13b and circulates via the supply opening 13d of the bearing 11. The oil then circulates through the plain bearing 11 in one or more cavities 10c and then exits through orifices 10d in order to lubricate the satellites.

[0057] Figures 3 to 5 represent an exemplary embodiment of a mechanical reducer 6 and in particular of one of its plain bearings 11.

[0058] The plain bearing 11 of each satellite 8 comprises:

[0059] - a hollow cylindrical body 20b which comprises an axis X and which internally defines a 10c cavity intended to receive oil,

[0060] - an annular wall 20a which extends around the axis Y and the hollow body 20b and which comprises an external cylindrical guide surface 25a,

[0061] - an annular core 20c which extends around the Y axis, between the body 20b and the wall 20a, and which connects the body 20b to the wall 20a, this annular core 20c having a length along the Y axis which is less than a length of the wall 20a so that the wall 20a delimits around the body 20b an annular space 21a in front of the core 20c and an annular space 21b behind the core 20c, and

[0062] - oil passage orifices 10d formed in the body 20b, the core 20c and the wall 20a and extending from the cavity 10c to the guide surface 25a.

[0063] The spaces 21a, 21b have a general U-shaped section whose opening opens out in the axial direction. This configuration makes it possible to give a certain flexibility to the bearing 11, at each of its axial ends.

[0064] The cavity 10c of the body 20b can be closed by a partition 20d and has an axial end open on the opposite side to receive oil supplied by the distributor oil (not shown). The partition 20d and the body 20b thus define the cavity 10c for receiving the lubricating oil.

[0065] In the example shown, the orifices 10d are three in number, even if this number is not limiting. They each have a generally elongated and cylindrical shape. They are aligned and regularly spaced in a plane M passing through the axis Y of the bearing H ([Fig.4]).

[0066] Figures 4 and 5 show that the radially external ends of the orifices 10d can open into the same groove 23 formed on the surface 25a of the bearing. This groove 23 has a generally elongated shape and extends substantially in the plane M.

[0067] As shown in [Fig. 5], the plain bearing 11 can be considered as comprising or consisting of two angular sectors 24, 25 extending around the Y axis, namely a first sector 24 for forming an oil film and a second sector 25 for breaking the oil film.

[0068] Preferably, the first sector 24 has an angular extent greater than or equal to that of the second sector 25. The first sector 24 may have an angular extent of between 180° and 270°, and the second sector 25 may have an angular extent of between 90° and 180°.

[0069] The first sector 24 comprises a portion 25al of the external surface 25 which is configured to delimit with an internal cylindrical surface 8a of the bearing 8 a circumferential space for receiving oil and forming an oil film.

[0070] The orifices 10d and the groove 23 are here located at a circumferential end of the sector 24. The oil conveyed by the orifices 10d is thus intended to flow circumferentially over the entire extent of the first sector 24. The direction of rotation of the satellite 8 on the plain bearing 11 is chosen to ensure the formation of the oil film and is indicated by the arrow F1 in [Fig.5].

[0071] The second sector 25 comprises a portion 25a2 of the external surface 25 which comprises a bath 26 for breaking the oil film formed on the sector 24.

[0072] The tub 26 has a generally elongated shape in the circumferential direction and advantageously extends over the entire circumferential extent of the sector 25. It is open radially outwards and is defined radially inwards by a bottom surface 26a which is curved around the axis Y.

[0073] The tub 26 is axially delimited by two side walls 26b, 26c which extend in the circumferential direction around the axis Y and which form the second peripheral surface 25a. The tub 26 is further delimited by two circumferential end walls 26d, one of which is located near the conveying pipes 10d.

[0074] Oil discharge pipes 27 are formed in the bearing 11 and extend between the bathtub 26 and the spaces 21a, 21b. These pipes 27 extend here parallel to the Y axis and comprise a first series which open into the bottom of the space 21a and onto one of the lateral surfaces of the bathtub 26. This first series of pipes is formed in the core 20c. Another series of pipes 27 passes through the wall 26c and opens into the bottom of the space 21b and onto the other lateral surface of the bathtub 26. This second series of pipes is formed in the core 20c.

[0075] The pipes 27 are located in the vicinity of the bottom surface 26a of the bathtub 26 and are here distributed over the entire circumferential extent of the bathtub.

[0076] The oil film which forms on the surface 24a of the first sector 24 is intended to be broken at the level of the bath 26 which will collect the oil from this film and evacuate it through the pipes 27. This oil, heated by the shearing and friction, will therefore not risk in turn heating the oil which will be conveyed through the orifices 10d. The risk of mixing between the hot oil and the cold oil is therefore reduced or even prevented, which significantly improves the lubrication of the reducer and therefore the efficiency of the reducer.

[0077] Figures 6 and 7 illustrate a first embodiment of a plain bearing 110 according to the invention.

[0078] This bearing 111 is similar to a plain bearing 11 of the prior art insofar as it comprises:

[0079] - a hollow cylindrical body 20b which comprises an axis X and which internally defines a 10c cavity intended to receive oil,

[0080] - an annular wall 20b which extends around the Y axis and the hollow body 20b and which comprises an external cylindrical guide surface 25a,

[0081] - an annular core 20c which extends around the Y axis, between the body 20b and the wall 20a, and which connects the body 20b to the wall 20a, this annular core 20c having a length L2 along the axis X which is less than a length L1 of the wall 20a so that the wall 20a delimits around the body 20b an annular space 21a in front of the core 20c and an annular space 21b behind the core 20c, and

[0082] - oil passage orifices 10d formed in the body 20b, the core 20c and the wall 20a and extending from the cavity 10c to the guide surface 25a.

[0083] The particularity of the plain bearing 110 according to the invention is that it further comprises at least one annular row of lightening holes 122 in said core 20c, these holes 122 being regularly distributed all around the Y axis.

[0084] These holes 122 have a lightening function and therefore do not have the same function as the oil evacuation pipes 27 of the plain bearing 11 of FIGS. 3 to 5. Furthermore, these holes 122 are regularly distributed around the Y axis, which is not the case for the pipes 27. This means that the arrangement of the holes 122 does not depend on the location of the load (arrow F2 to 1 a [Fig. 6]) on the plain bearing 110 as a function operation.

[0085] A plain bearing 110 without ducts 27 can be equipped with lightening holes 122 as in the example shown, but it is important to note that a plain bearing 110 equipped with ducts 27 can also comprise lightening holes 122 within the meaning of the invention.

[0086] In the example shown, the core 20c comprises a single annular row of lightening holes 122 which pass through the entire length L2 of the core 20c and open into the spaces 21a, 21b.

[0087] The number of holes 122 is between 5 and 30, and is 10 in the example shown.

[0088] The holes 122 have a constant section over their entire length in the example shown. They have a diameter D2 between 0.0LDI and 0.LDI, DI being the diameter of the guide surface 25a. This diameter D2 can be between 0.008.L3 and 0.1.L3, L3 being the length of the bearing 110 measured along the Y axis.

[0089] The holes 122 have a circular, oblong or elliptical cross-section. They are parallel to the Y axis or inclined at a maximum angle of + / -10° relative to this Y axis.

[0090] In the embodiment variant of [Fig.8], the core 20c comprises a first annular row of blind lightening holes 122 which are formed on a first side of the core 20c and which open into a first of said spaces 21a, and a second annular row of blind lightening holes 122 which are formed on a second side of the core 20c and which open into a second of said spaces 21b.

[0091] In the embodiment variant of [Fig. 9], the holes 122 differ from those of [Fig. 7] in that their cross-section varies along their length. Each of the holes 122 comprises, for example, five sections 122a, 122b, 122c having different diameters, namely a middle section 122a of diameter D3, two end sections 122c of diameter D5, and two other intermediate sections 122b each arranged respectively between the middle section 122a and one of the end sections 122c. These intermediate sections 122b have a diameter D4, with D3 <D4<D5.

[0092] In the embodiment variant of [Fig. 10], the holes 122 differ from those of [Fig. 9] in that their cross-section varies along their length. Each of the holes 122 comprises, for example, three sections 122i, 122j, 122k having different diameters, namely a middle section 122j of diameter D7 and two end sections 122i, 122k of respective diameters D6 and D8. The middle section 122j is between the end sections 122i, 122k, with D6 <D7<D8. Le tronçon d’extrémité 122k de plus grand diamètre D8 débouche dans l’espace 21a, 21b correspondant.

[0093] The present invention also relates to a reducer 6 as described above, which comprises this type of plain bearing 110, as well as a turbomachine 1 as illustrated in [Fig.l] comprising such a reducer 6.

Claims

Claims

1. Plain bearing (110) for a satellite of a mechanical reducer (6) of a turbomachine (1), in particular of an aircraft, this plain bearing (110) being formed in one piece and comprising: - a hollow cylindrical body (20b) which comprises an axis (Y) and which internally defines a cavity (10c) intended to receive oil, - an annular wall (20a) which extends around the axis (Y) and the hollow body (20b) and which comprises an external cylindrical guide surface (25a), - an annular core (20c) which extends around the axis (Y), between the body (20b) and the wall (20a), and which connects the body (20b) to the wall (20a), this annular core (20c) having a length (L2) along the axis (Y) which is less than a length (L1) of the wall (20a) so that the wall (20a) delimits around the body (20b) an annular space (21a) in front of the core (20c) and an annular space (21b) behind the core (20c), and - oil passage orifices (10d) formed in the body (20b),the core (20c) and the wall (20a) and extending from the cavity (10c) to the guide surface (25a), characterized in that it comprises at least one annular row of lightening holes (122) in said core (20c), these holes (122) being regularly distributed all around the axis (Y).,

2. Plain bearing (110) according to claim 1, wherein the core (20c) comprises a single annular row of lightening holes (122) which pass through the entire length (L2) of the core (20c) and open into said spaces (21a, 21b).

3. A plain bearing (110) according to claim 1, wherein the core (20c) comprises a first annular row of blind lightening holes (122) which are formed on a first side of the core (20c), front or rear, and which open into a first of said spaces (21a), and a second annular row of blind lightening holes (122) which are formed on a second opposite side of the core (20c) and which open into a second of said spaces (21b).

4. Plain bearing (110) according to one of claims 1 to 3, in which the holes (122) have a constant section over their entire length.

5. Plain bearing (110) according to one of claims 1 to 3, in which the holes (122) have a section which varies along their length, each of the holes (122) comprising for example at least two or three sections (122a, 122b, 122c, 122i, 122j, 122k) having different diameters.

6. Plain bearing (110) according to one of the preceding claims, in which the holes (122) have a diameter D2 between 0.01.DI and 0.1.Dl, DI being the diameter of the guide surface.

7. Plain bearing (110) according to one of the preceding claims, in which the holes have a diameter D2 between 0.008.L3 and 0.1.L3, L3 being the length of the bearing (110) measured along the axis (Y).

8. Plain bearing (110) according to one of the preceding claims, in which the holes (122) have a circular, oblong or elliptical shape in section.

9. Plain bearing (110) according to one of the preceding claims, in which the holes (122) are parallel to the axis (Y) or inclined at a maximum angle of + / -10° relative to this axis (Y).

10. Mechanical reducer (6) for a turbomachine (1), in particular for an aircraft, this reducer comprising: - a sun gear (7) having an axis of rotation (X), - a ring gear (9) which extends around the sun gear (7), - satellites (8) which are meshed with the sun gear (7) and the ring gear (9) and which are each mounted on a plain bearing (110) according to one of the preceding claims, the plain bearings (110) being fixed to a planet carrier (10), and - a lubricating oil distributor (13) which is configured to supply oil to the cavities (10c) of said bearings.

11. Turbomachine (1), in particular for an aircraft, comprising a mechanical reducer (6) according to claim 10.

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