FR3139870A1 - TRANSMISSION ASSEMBLY FOR AN AIRCRAFT TURBOMACHINE MECHANICAL REDUCER - Google Patents

Abstract

Transmission assembly for a mechanical reduction gear (6) of an aircraft turbomachine (1), this assembly comprising: - a planet carrier (10), - bearing bodies (10b) each comprising two coaxial tubular walls, respectively external ( 20a) and internal (20b), which are connected together by a veil (20c), and which are fixed to the planet carrier (10), and - satellites (8) mounted around the external tubular walls (20a) of the bodies bearing (10b), and capable of rotating around the second axes (Y) with respect to the bearing bodies (20b), characterized in that the sails (20c) of the bearing bodies (10b) are located in a first plane (H1) perpendicular to the first axis (X) which is at an axial distance from a second plane (H2) perpendicular to the first axis (X) and passing through the middles of the external tubular walls (20a). Figure for abstract: Figure 4

Description

TRANSMISSION ASSEMBLY FOR AN AIRCRAFT TURBOMACHINE MECHANICAL REDUCER Technical field of the invention

The present invention relates to a transmission assembly for a mechanical gearbox of an aircraft turbomachine.

Technical background

The state of the art includes in particular documents FR-B1-3 066 792, FR-B1-3 071 023, FR-B1-3 098 562 and FR-B1-3 101 129.

The role of a mechanical gearbox is to modify the speed and torque ratio between the input axis and the output axis of a mechanical system.

New generations of dual-flow turbomachines, particularly those with a high dilution ratio, include a mechanical reduction gear to drive the shaft of a fan (also called a “fan”). Usually, the purpose of the reduction gear is 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.

Such a reduction gear includes a central pinion, called a solar, a crown and pinions called satellites, which are engaged between the solar and the crown. The satellites are held by a frame called a satellite carrier. The solar, the crown and the satellite carrier are planetary because their axes of revolution coincide with the longitudinal axis X of the turbomachine. The satellites each have a different axis of revolution equally distributed over the same operating diameter around the axis of the planetary gears. These axes are parallel to the longitudinal axis X.

There are several reducer architectures. In the state of the art of double-flow turbomachines, the reduction gears 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 solar.

- On an epicyclic gearbox, the ring gear 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 crown rotates in the opposite direction of the solar and the satellite carrier.

Reducers can be made up of 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, helical or chevron teeth.

Reducers can be made up of one or more meshing stages. This meshing is ensured in different ways such as by contact, by friction or even by magnetic fields.

A satellite can include one or two meshing stages. In the present application, the term “stage” or “teeth” means a series of meshing teeth with a series of complementary teeth. A tooth can be internal or external. A single-stage satellite comprises teeth which can be straight, helical or chevron-shaped and whose teeth are located on the same diameter. This toothing cooperates with both the solar and the crown.

A double-stage satellite comprises two teeth or two sets of teeth which are located on different diameters. A first tooth cooperates with the solar and a second tooth cooperates with the crown.

There are two planet carrier technologies, one-piece planet carriers and planet carriers which feature a cage and a cage carrier connected together by flexible links.

The satellites are guided in rotation by bearings which are formed or carried by bearing bodies fixed to the planet carrier. The bearings can be plain or hydrodynamic bearings, rolling bearings, etc.

One of the problems with a gearbox of this type concerns the transmission of forces during operation and the risk of misalignment of the satellites.

These misalignments reduce the lifespan of the gearbox because they create unwanted overloads on the teeth and on the satellite bearings. To reduce these misalignments, several solutions exist such as the use of a planet carrier in the form of a cage and cage carrier rather than in a single piece, the use of a floating ring gear, etc.

In a planet carrier, the forces applied to the planet carriers are transmitted by the bearing bodies to the planet carrier. The configuration of the planet carrier does not ensure a resumption of these forces in a centered manner by these forces, because of the presence of the crown. The balancing of forces must therefore be achieved by the geometry of the planet carrier or the bearing bodies. However, the planet carrier is a complex part with few spaces available to accommodate this particular geometry.

The invention provides a solution to this problem in a simple, effective and economical manner.

The invention relates to a transmission assembly for a mechanical gearbox of an aircraft turbomachine, this assembly comprising:

- a satellite carrier which extends around a first axis,

- bearing bodies distributed around the first axis and defining second axes parallel to the first axis, each bearing body comprising two coaxial tubular walls, respectively external and internal, which extend at least in part around the other and which are connected together by a web, the bearing bodies being fixed to said first wall via their internal tubular walls, and

- satellites mounted around the external tubular walls of the bearing bodies, and able to rotate around the second axes with respect to the bearing bodies,

characterized in that the sails of the bearing bodies are located in a first plane perpendicular to the first axis which is at an axial distance from a second plane perpendicular to the first axis and passing through the middles of the external tubular walls.

The invention thus proposes to compensate for the misalignment of the satellite carrier by the misalignment of the bearing bodies of the satellites. For this, the connecting webs of the tubular walls of the bearing bodies are not aligned with the middles of the external tubular walls of these bodies, and are thus not aligned with the middles of the satellites. This configuration makes it possible to favor the deformation of the bearing bodies in a direction which is opposite to the direction of deformation generally encountered, so as to counterbalance this usual deformation and to reduce or even prevent the resulting misalignments of the teeth of the satellites.

The solution proposed below is compatible with a single-stage or multi-stage reducer. It is compatible with a so-called epicyclic, planetary or differential gearbox. It is also compatible with straight, helical or chevron teeth. It is compatible with any type of planet carrier, and in particular with a one-piece planet carrier. It is also compatible with any type of bearing, whether composed of rolling elements, a hydrodynamic bearing, etc.

• la paroi tubulaire interne de chacun des corps de palier comprend une unique extrémité longitudinale de fixation au porte-satellites, et en particulier à une première paroi du porte-satellites ;
• l’extrémité longitudinale de la paroi tubulaire interne est engagée dans un logement du porte-satellites, et en particulier de la première paroi, et/ou est appliquée axialement contre le porte-satellites, et en particulier la première paroi, et est fixée au porte-satellites, et en particulier à cette première paroi, par des vis ou des systèmes vis-écrou ;
• l’extrémité longitudinale de la paroi tubulaire interne comprend une bride annulaire de fixation au porte-satellites et en particulier à la première paroi ;
• la paroi tubulaire externe de chacun des corps de palier définit un espace interne, l’extrémité longitudinale de la paroi tubulaire interne qui est fixée au porte-satellites, et en particulier à la première paroi, étant située à l’extérieur de cet espace, et l’extrémité longitudinale opposée de cette paroi tubulaire interne étant située à l’intérieur de cet espace ;
• l’extrémité longitudinale de la paroi tubulaire interne, qui est opposée à celle fixée au porte-satellites, et en particulier à la première paroi, est située dans ledit premier plan ;
• le porte-satellites comprend une première et une seconde paroi annulaire parallèles entre elles à la première paroi et à distance axiale l’une de l’autre, les corps de palier s’étendant entre ces première et seconde parois, et la paroi tubulaire interne de chacun des corps de palier comprenant deux extrémités longitudinales opposées de fixation respectivement à ces première et seconde paroi ;
• les parois tubulaires interne et externe et le voile de chacun des corps de palier sont formés d’une seule pièce ;
• la paroi tubulaire externe et le voile de chacun des corps de palier sont formés d’une seule pièce, le voile étant fixé sur la paroi tubulaire interne du corps de palier ;
• les voiles des corps de palier sont situés à distance axiale des extrémités longitudinales des parois tubulaires externes des corps de palier ;
• le voile de chacun des corps de palier a une étendue angulaire autour du second axe du corps de palier, qui est inférieure à 250°, et de préférence inférieure à 200° ;
• les corps de palier sont positionnés autour du premier axe de sorte que leurs voiles soient tous orientés de la même façon et du côté d’un corps de palier adjacent ;
• le voile de chacun des corps de palier présente en section transversale deux surfaces incurvées dont les concavités sont opposées l’une à l’autre ;
• la paroi tubulaire interne de chacun des corps de palier comprend une surface externe tronconique dont une extrémité de plus grand diamètre est située du côté de ladite première paroi ;

The assembly according to the invention may comprise one or more of the following characteristics, taken in isolation from each other, or in combination with each other:

• the internal tubular wall of each of the bearing bodies comprises a single longitudinal end for attachment to the planet carrier, and in particular to a first wall of the planet carrier;
• the longitudinal end of the internal tubular wall is engaged in a housing of the planet carrier, and in particular of the first wall, and/or is applied axially against the planet carrier, and in particular the first wall, and is fixed to the satellite carrier, and in particular to this first wall, by screws or screw-nut systems;
• the longitudinal end of the internal tubular wall comprises an annular flange for fixing to the planet carrier and in particular to the first wall;
• the external tubular wall of each of the bearing bodies defines an internal space, the longitudinal end of the internal tubular wall which is fixed to the planet carrier, and in particular to the first wall, being located outside this space, and the opposite longitudinal end of this internal tubular wall being located inside this space;
• the longitudinal end of the internal tubular wall, which is opposite to that fixed to the planet carrier, and in particular to the first wall, is located in said first plane;
• the planet carrier comprises a first and a second annular wall mutually parallel to the first wall and at an axial distance from one another, the bearing bodies extending between these first and second walls, and the internal tubular wall each of the bearing bodies comprising two opposite longitudinal ends for fixing respectively to these first and second walls;
• the internal and external tubular walls and the wall of each of the bearing bodies are formed in one piece;
• the outer tubular wall and the wall of each of the bearing bodies are formed in one piece, the wall being fixed on the internal tubular wall of the bearing body;
• the sails of the bearing bodies are located at an axial distance from the longitudinal ends of the external tubular walls of the bearing bodies;
• the web of each of the bearing bodies has an angular extent around the second axis of the bearing body, which is less than 250°, and preferably less than 200°;
• the bearing bodies are positioned around the first axis so that their sails are all oriented in the same way and on the side of an adjacent bearing body;
• the web of each of the bearing bodies has in cross section two curved surfaces whose concavities are opposite each other;
• the internal tubular wall of each of the bearing bodies comprises a frustoconical external surface of which one end of larger diameter is located on the side of said first wall;

-- the frustoconical surface of the internal tubular wall has a length along the second axis, which represents at least 50% of a maximum length of this internal tubular wall;

-- the outer tubular wall of each of the bearing bodies comprises thinned longitudinal ends;

-- the internal tubular wall of each of the bearing bodies comprises two opposite longitudinal ends having different external diameters.

-- the satellite carrier is in one piece or is of the cage and cage carrier type;

-- the external tubular wall of each of the bearing bodies has an external cylindrical surface configured to form a smooth bearing for guiding the corresponding satellite;

-- the external tubular wall of each of the bearing bodies has an external cylindrical surface configured to form one or more rolling tracks for guiding rolling elements of the corresponding satellite;

-- the internal tubular wall has a length along the second axis, which is less than that of the external tubular wall;

-- the web has an axial length or thickness which represents less than 50% of a maximum length of the external tubular wall;

-- the satellite carrier comprises at least a first annular wall.

The present invention also relates to a mechanical reduction gear for a turbomachine, in particular an aircraft, comprising an assembly according to one of the preceding claims, a solar mounted in the satellite carrier and meshed with the satellites, and a ring gear mounted around the carrier. satellites and meshed with the satellites.

The invention further relates to a turbomachine, in particular for an aircraft, comprising at least one assembly or a reduction gear as described above.

Brief description of the figures

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:

there is a schematic view in axial section of an aircraft turbomachine,

there is a partial schematic view in axial section of a mechanical reducer,

there is a schematic perspective view and axial section of a bearing body and a satellite of a mechanical reduction gear,

there is a schematic partial sectional view of a bearing body according to one embodiment of the invention,

there is a schematic front view of the bearing body of the ,

there is a schematic front view of an assembly according to the invention,

there is a partial schematic view in perspective and in axial section of the entire ,

Figures 8a and 8b are views similar to that of and representing alternative embodiments of the invention,

Figures 9a and 9b are views similar to that of and representing other alternative embodiments of the invention,

Figures 10a and 10b are views similar to that of and representing alternative embodiments of the invention.

Detailed description of the invention

There 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 a nozzle of exhaust 1 hour. The high pressure compressor 1b and the high pressure turbine 1d are connected by a high pressure shaft 2 and with it form a high pressure body (HP). The low pressure compressor 1a and the low pressure turbine 1e are connected by a low pressure shaft 3 and with it form a low pressure body (LP).

The fan S is driven by a fan shaft 4 which is rotated with the BP shaft 3 by means of a reduction gear 6. This reduction gear 6 is generally of the planetary or epicyclic type.

Although the following description concerns a planetary or epicyclic type reducer, it also applies to a mechanical differential in which the three components, which are the planet carrier, the crown and the solar, are movable in rotation, the speed rotation of one of these components depending in particular on the difference in speed of the two other components.

The reduction gear 6 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 makes up the motor casing or stator 5 is arranged so as to form an enclosure E surrounding the reduction gear 6. This enclosure E is here closed upstream by seals at the level of a bearing allowing the crossing of the fan shaft 4, and downstream by joints at the level of the crossing of the BP shaft 3.

There shows a reducer 6 which can take the form of different architectures depending on whether certain parts are fixed or rotating. At the input, the reducer 6 is connected to the BP shaft 3, for example via internal splines 7a. Thus the BP shaft 3 drives a planetary pinion called the solar 7. Conventionally, the solar 7, whose axis of rotation coincides with that of the turbomachine same diameter around the axis of rotation .

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

• dans une configuration épicycloïdale, l’ensemble des satellites 8 entraine en rotation le porte-satellite 10 autour de l’axe X de la turbomachine. La couronne est fixée au carter moteur ou stator 5 via un porte-couronne 12 et le porte-satellites 10 est fixé à l’arbre de soufflante 4.
• dans une configuration planétaire, l’ensemble des satellites 8 est maintenu par un porte-satellites 10 qui est fixé au carter moteur ou stator 5. Chaque satellite entraine la couronne qui est rapportée à l’arbre de soufflante 4 via un porte-couronne 12.

As an output we have:

• in an epicyclic configuration, all of the satellites 8 rotate the planet carrier 10 around the axis X of the turbomachine. The ring gear is fixed to the motor casing or stator 5 via a ring gear holder 12 and the planet carrier 10 is fixed to the fan shaft 4.
• in a planetary configuration, all of the satellites 8 are held by a planet carrier 10 which is fixed to the motor casing or stator 5. Each satellite drives the ring gear which is attached to the fan shaft 4 via a ring gear carrier 12 .

Each satellite 8 is mounted to rotate freely using a bearing 11, for example of the rolling or hydrodynamic plain bearing type. In the case of a plain bearing, the bearing 11 comprises a bearing body 10b and the bearing bodies 10b of the different plain bearings are positioned relative to each other and are carried by walls 10a1, 10a2 of the planet carrier 10 .

The walls 10a1, 10a2 have an annular shape and are perpendicular to the axis

There is a number of bearings 11 equal to the number of satellites 8. For reasons of operation, assembly, manufacturing, control, repair or replacement, the bearings 11 (and in particular the bearing bodies 10b) and the walls 10a1, 10a2 can be separated into several pieces.

• une demi-couronne amont 9a constituée d’une jante 9aa et d’une demi-bride de fixation 9ab. Sur la jante 9aa se trouve l’hélice amont de la denture du réducteur. Cette hélice amont engrène avec celle du satellite 8 qui engrène avec celle du solaire 7.
• une demi-couronne aval 9b constituée d’une jante 9ba et d’une demi-bride de fixation 9bb. Sur la jante 9ba se trouve l’hélice aval de la denture du réducteur. Cette hélice aval engrène avec celle du satellite 8 qui engrène avec celle du solaire 7.

For the same reasons cited above, the 8d teeth of a gearbox can be separated into several helices each having a median plane P. In our example, we detail the operation of a gearbox with several helices with a crown separated into two halves. crowns:

• an upstream half-crown 9a consisting of a rim 9aa and a half-fixing flange 9ab. On rim 9aa is the propeller upstream of the gearbox teeth. This upstream propeller meshes with that of satellite 8 which meshes with that of solar 7.
• a downstream half-crown 9b consisting of a rim 9ba and a half-fixing flange 9bb. On rim 9ba is the downstream propeller of the gearbox teeth. This downstream propeller meshes with that of satellite 8 which meshes with that of solar 7.

If the propeller widths vary between the solar 7, the satellites 8 and the crown 9 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 .

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

The arrows of the describe the routing of the oil in the reducer 6. The oil arrives in the reducer 6 from the stator part 5 in the 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 is separated into two parts generally each repeated with the same number of satellites. The injectors 13a have the function of lubricating the teeth and the arms 13b have the function of lubricating the bearings 11. The oil is brought towards injectors 13a to exit through ends 13c in order to lubricate the teeth of the satellites with oil 8, from the solar 7 and also from the crown 9. The oil is also brought towards the arm 13b and circulates via the supply mouth 13d of the bearing body 10b in an internal cavity 10c of the latter. The oil then circulates in this cavity 10c to supply oil passage orifices 10d to an external cylindrical guiding surface of the corresponding satellite.

There shows a more concrete example of producing a plain bearing and its bearing body 10b for a gearbox satellite 8.

The bearing body 10b comprises two coaxial tubular walls 20a, 20b which extend one around the other and which are interconnected by an annular web 20c.

The internal tubular wall 20b has its two axial ends 20b1, 20b2 which are fixed to the walls 10a1, 10a2 of the planet carrier 10 and which are open to define the aforementioned supply mouth 13d, in order to receive oil supplied by the distributor (not shown). The internal wall 20b thus defines the cavity 10c for receiving the lubricating oil.

The outer tubular wall 20a has a length or axial dimension measured along the Y axis, which is close to that of the wall 20b. The wall 20a comprises an external cylindrical surface 20aa which is configured to delimit with an internal cylindrical surface 8a of the bearing 8 an annular space for receiving oil and forming an oil film with a view to forming the hydrodynamic bearing.

The web 20c has a smaller axial length or thickness measured in the same way, so that the axial ends of the walls 20a, 20b delimit between them annular grooves 21a, 21b. This configuration makes it possible to give a certain flexibility to the bearing body 10b, at each of its axial ends.

The bearing body 10b comprises orifices 10d for the passage of lubricating oil from the cavity 10c to the external periphery of the support 10b, and in particular to the surface 20aa. In the example shown, these orifices 10d are formed in the internal wall 20b, the core 20c and finally the external wall 20a.

Cavity 10c is supplied with oil continuously during operation. This oil enters the cavity 10c then is conveyed through the orifices 10d to the surface 20aa. The centrifugal forces applied to the planet carrier and to the bodies 10b in operation are sufficient to ensure this oil circulation.

There shows a first embodiment of the invention.

The invention relates to an assembly comprising a planet carrier 10 and satellites 8 which are mounted on bearing bodies 10b fixed to the planet carrier.

There shows only a bearing body 10b in axial section, that is to say in section in the plane passing through the Y axis which is parallel to the X axis (cf. ).

The satellite carrier 10 can be in one piece or of the cage and cage carrier type. These two types of satellite carriers will not be described in detail because they are well known to those skilled in the art.

The satellite carrier 10 of the assembly according to the invention may comprise a single annular wall, called first wall 10a1. This wall 10a1 extends around the axis .

Alternatively, the planet carrier 10 could comprise two annular walls, called respectively first and second walls 10a1, 10a2. These walls 10a1, 10a2 would be parallel and at a distance from each other and would define between them a space for housing the solar 7, the satellites 8 and the bearings 11 of the latter.

The satellites 8 are for example of the type of those represented in . They can include one or two teeth for example. They can be guided on the bearing bodies 10b by a film of oil or by rolling elements, as mentioned in the above.

The bearing bodies 10b are distributed around the X axis, called the first axis, and define the Y axes, called second axes.

Each bearing body 10b comprises two coaxial tubular walls, respectively external 20a and internal 20b, which extend at least partly around each other and which are connected together by an annular web 20c.

In the embodiment of the , the web 20c of the bearing body 10b is located in a first plane H1 perpendicular to the axes X, Y which is at an axial distance from a second plane H2 perpendicular to the first axis H1 and passing through the middle of the outer tubular wall 20a. It is this offset which makes it possible to promote the deformation of the bearing body 10b, and in particular of its external wall 20a, according to at least one of the arrows F1 and F2, and thus to compensate for the deformations of the planet carrier 10 in opposite directions.

In the example shown, the outer tubular wall 20a comprises a smooth outer cylindrical surface 20aa intended to form the oil film guiding the rotation of the satellite 8. The opposite longitudinal ends of the outer wall 20a are thinned.

The external wall 20a defines an internal space E.

The web 20c has in cross section two curved surfaces 20c1, 20c2 whose concavities are opposite each other.

The web 20c has a minimum length L2 or minimum thickness, measured along the axis Y, which represents less than 50%, and preferably less than 30%, of the length L1 of the external wall 20a measured along the same axis.

As is visible in the , the web 20c is preferably non-continuous over 360° around the Y axis. On the contrary, it has an angular extent around this Y axis, which is less than 250°, and preferably less than 200°. This angular extent is of the order of 180° in the example shown.

The internal tubular wall 20b comprises a single longitudinal end 20b1 for attachment to the first wall 10a1 of the planet carrier 10. The bearing body 10b is therefore fixed cantilevered on the planet carrier 10.

The internal wall 20b is partly housed inside the external wall 20a and therefore in the space E. Its longitudinal end 20b1 for fixing to the wall 10a1 of the satellite carrier 10 is located outside the space E. and comprises an external cylindrical surface 20ba which is for example configured to be housed in a housing 10ab of complementary shape to the first wall 10a1.

The rest of the internal wall 20b comprises an external frustoconical surface 20bb whose side of larger diameter is located on the side of the end 20b1, and whose side of smaller diameter is located on the side of the web 20c and is connected to this sail 20c.

The internal wall 20b has a length L3 less than or equal to that L1 of the external wall 20a.

The bearing body 10b may comprise one or more orifices or internal conduits 23 for the passage of lubricating oil, in particular up to the surface 20aa.

Figures 6 and 7 show an embodiment of an assembly according to the invention.

In this exemplary embodiment, the planet carrier 10 is of the cage and cage carrier type.

Furthermore, in this example, the outer tubular wall 20a of each bearing body 10b defines rolling paths or tracks 20cc for rolling elements such as rollers. The satellite guide bearings are therefore rolling bearings.

The veil 20c includes conduits 23 for lubricating oil passage.

Figures 8a and following show alternative embodiments of the invention.

In Figures 8a and 8b, each of the bearing bodies 10b is formed in one piece.

We see in Figure 8a that the end 20b1 of the internal wall 20b is engaged in the housing 10ab of the first wall 10a1 of the planet carrier 10. The external cylindrical surface 20ba of this end 20b1 is surrounded by an internal cylindrical surface of the housing 10ab. The end 20b1 of the internal wall 20b further comprises an end surface 20dd which is perpendicular to the axis Y and which is applied against a bottom of the housing 10ab.

This end surface 20dd comprises orifices 24 which are aligned with orifices 25 of the first wall 10a1 for mounting fastening elements of the screw type or screw-nut systems (not shown).

In the variant of Figure 8b, the end 20b1 of the internal wall 20b is applied axially against the first wall 10a1 and comprises a radially external annular flange 26 (vis-à-vis the axis Y) which is tightened against this first wall 10a1 via fixing elements of the screw type or screw-nut systems (not shown).

In Figures 9a and 9b, each of the bearing bodies 10b is formed of two parts. The outer tubular wall 20a and the web 20c of each bearing body 10b are formed in one piece, and the inner wall 20b forms another piece. The web 20c is fixed to the end 20b2 of the internal wall 20b which is opposite its end 20b1 for fixing to the first wall 10a1. For this, the web 20c comprises a radially internal annular flange 27 (vis-à-vis the axis Y) which is tightened against this end 20b2 by means of fixing elements of the screw type or screw-nut systems ( not shown).

In Figures 10a and 10b, it is the two longitudinal ends 20b1, 20b2 of the internal wall 20b of each bearing body 10b which are fixed to the planet carrier 10, and in particular to the first and second walls 10a1, 10a2 mentioned above.

The internal wall 20b has a length L3 which is here greater than that L1 of the external wall 20a. The two ends 20b1, 20b2 of the internal wall 20b are here located outside the space E and each comprise an external cylindrical surface 20ba, intended for example to be engaged in a housing 10ab of the first or second wall 10a1, 10a2.

The longitudinal end of the internal wall 20b located on the side of the wall 20c has here a diameter D1 which is smaller than the diameter D2 of the opposite longitudinal end of the wall 20b. Between these two ends, the internal wall 20b has a frustoconical surface 20bb.

The gains brought by the invention are in particular:

- a reduction in the mass of the gearbox due to the reduction in the size of the planet carrier,

- a reduction in satellite misalignment,

- etc.

Claims (16)

Transmission assembly for a mechanical reduction gear (6) of an aircraft turbomachine (1), this assembly comprising:
- a satellite carrier (10) which extends around a first axis (X),
- bearing bodies (10b) distributed around the first axis (X) and defining second axes (Y) parallel to the first axis (X), each bearing body (10b) comprising two coaxial tubular walls, respectively external (20a) and internal (20b), which extend at least partly around each other and which are connected together by a web (20c), the bearing bodies (20b) being fixed to said first wall (10a1 ) via their internal tubular walls (20b), and
- satellites (8) mounted around the external tubular walls (20a) of the bearing bodies (10b), and capable of rotating around the second axes (Y) with respect to the bearing bodies (20b),
characterized in that the webs (20c) of the bearing bodies (10b) are located in a first plane (H1) perpendicular to the first axis (X) which is at an axial distance from a second plane (H2) perpendicular to the first axis ( X) and passing through the middles of the external tubular walls (20a). Assembly according to claim 1, in which the internal tubular wall (20b) of each of the bearing bodies (10b) comprises a single longitudinal end (20b1) for fixing to the planet carrier (10). Assembly according to claim 2, in which the longitudinal end (20b1) of the internal tubular wall (20b) is engaged in a housing (10ab) of the planet carrier (10) and/or is applied axially against the planet carrier ( 10), and is fixed to the planet carrier (10) by fixing means, in particular screws or screw-nut systems. Assembly according to claim 2 or 3, in which the longitudinal end (20b1) of the internal tubular wall (20b) comprises an annular flange (26) for fixing to the planet carrier (10). Assembly according to one of claims 2 to 4, in which the external tubular wall (20a) of each of the bearing bodies (10b) defines an internal space (E), the longitudinal end (20b1) of the internal tubular wall ( 20b) which is fixed to the planet carrier (10) being located outside this space (E), and the opposite longitudinal end of this internal tubular wall (20b) being located inside this space (E ). Assembly according to one of claims 2 to 5, in which the longitudinal end (20b1) of the internal tubular wall (20b), which is opposite to that fixed to the planet carrier (10), is located in said first plane ( H1). Assembly according to claim 1, in which the planet carrier (10) comprises a first and a second annular wall (10a1, 10a2) parallel to each other and at an axial distance from one another, the bearing bodies (10b) extending between these first and second walls (10a1, 10a2), and the internal tubular wall (20b) of each of the bearing bodies (10b) comprising two opposite longitudinal ends (20b1, 20b2) for fixing respectively to these first and second wall (10a1, 10a2). Assembly according to one of the preceding claims, in which the internal and external tubular walls (20a, 20b) and the web (20c) of each of the bearing bodies (10b) are formed in one piece. Assembly according to one of claims 1 to 7, in which the outer tubular wall (20a) and the web (20c) of each of the bearing bodies (10b) are formed in one piece, the web (20c) being fixed on the inner tubular wall (20b) of the bearing body (10b). Assembly according to one of the preceding claims, in which the sails (20c) of the bearing bodies (10b) are located at an axial distance from the longitudinal ends of the external tubular walls (20a) of the bearing bodies (10b). Assembly according to one of the preceding claims, in which the web (20c) of each of the bearing bodies (10b) has an angular extent around the second axis (Y) of the bearing body (10b), which is less than 250° , and preferably less than 200°. Assembly according to the preceding claim, in which the bearing bodies (10b) are positioned around the first axis (X) so that their sails (20c) are all oriented in the same way and on the side of a bearing body (10b). ) adjacent. Assembly according to one of the preceding claims, in which the web (20c) of each of the bearing bodies (10b) has in cross section two curved surfaces (20c1, 20c2) whose concavities are opposite each other. Assembly according to one of the preceding claims, in which the internal tubular wall (20b) of each of the bearing bodies (10b) comprises a frustoconical external surface (20bb) of which one end of larger diameter is located on the side of said first wall (10a1). Mechanical reducer (6) of a turbomachine, in particular of an aircraft, comprising an assembly according to one of the preceding claims, a solar (7) mounted in the planet carrier (10) and meshed with the satellites (8), and a crown (9) mounted around the planet carrier (10) and meshed with the planets (8). Turbomachine (1), in particular for aircraft, comprising at least one assembly according to one of claims 1 to 14 or a mechanical reduction gear (6) according to the preceding claim.