MECHANICAL REDUCER FOR AIRCRAFT TURBOMACHINE

Abstract

Mechanical reducer (60') for a turbomachine (1), in particular for an aircraft, this reducer comprising: - a sun gear (70), - a ring gear (90), - satellites (80) which are carried by a planet carrier (100) and which are meshed with the sun gear (70) and the ring gear (90), - hydrodynamic bearings (81') for guiding the rotation of the satellites (80), each of the satellites (80) being guided by two hydrodynamic bearings (81') independent of each other and arranged on either side of said plane (H), the two hydrodynamic bearings (81') for guiding each of the satellites (80) being located around a sleeve (86) of the satellite (80) and on either side of a web (88) of the satellite (80). Figure for the abstract: Figure 6

Description

Title of the invention: MECHANICAL REDUCER FOR AIRCRAFT TURBO-MACHINE 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 WO-A1-2010 / 092263, FR-A1-2 987 416, FR-A1-3 008 462, FR-A1-3 008 463, FR-A1-3 041 054 FR-A1-3 095 251 and FR-A1-3 116,096.

[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 mechanical system.

[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 and are equally distributed over the same operating diameter around the axis of the planetary gears. These 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 be composed of one or more meshing stages. This meshing is ensured in different ways such as by contact, by friction or even by magnetic fields.

[0011] In the present application, the term "stage" or "teeth" means a series of teeth meshing with a series of complementary teeth. A toothing can be internal or external.

[0012] A satellite can comprise one or two meshing stages. A single-stage satellite comprises a toothing which can be straight, helical or herringbone and whose teeth are located on the same diameter. This toothing cooperates with both the sun gear and the crown.

[0013] A double-stage satellite comprises two sets of teeth or two series of teeth which are located on different diameters. A first set of teeth cooperates with the sun gear and a second set of teeth cooperates with the crown.

[0014] Furthermore, each satellite is centered and guided in rotation around an axis by a bearing which is carried by the planet carrier. There are several bearing technologies for this application and the present application relates more specifically to the use of hydrodynamic bearings for guiding the satellites in a mechanical reducer.

[0015] In the present application, the term "hydrodynamic bearing" means a bearing comprising a body engaged in a satellite and around which is located a film of pressurized oil. In the state of the art, a satellite hydrodynamic bearing comprises a cylindrical body comprising an external cylindrical surface which extends inside an internal cylindrical surface of the satellite. The film of pressurized oil is interposed between these surfaces and makes it possible to avoid contact between these surfaces.

[0016] One of the disadvantages of this type of reducer is linked to the relatively large axial dimension of the satellites which take up significant loads generated by the transmission of torque at the level of the gears, as well as by the centrifugal effects applied to the satellites in the case of an epicyclic reducer. The bearings which support the satellites and guide them in rotation are therefore loaded and there is little space to integrate them without considerably increasing the size of the reducer.

[0017] It would be possible to use rolling element bearings as bearings. However, the bearings have a load capacity which does not allow them to be placed under the teeth of the satellites, it is then necessary to place them outside the satellites to give them a sufficient diameter, which considerably increases the size of the reducer.

[0018] From the point of view of space requirements, it is therefore preferable to use plain bearings or hydrodynamic bearings which have higher load capacities. This makes it possible to place the bearings under the teeth of the satellite, i.e. in a space of small diameter and axially long. A hydrodynamic bearing is generally supplied with oil from its middle and this oil is evacuated from its axial ends. It is easy to design a long bearing which extends over the entire length of the satellite. Such a bearing has a load capacity greater than the minimum required and requires a high oil flow rate since this flow rate depends, among other things, on the length of the bearing. This type of bearing also generates significant power losses. However, to have an efficient reducer, the required oil flow rate and power losses must be as low as possible.

[0019] The applicant has already proposed a solution to the problem of size, which consists of guiding each of the satellites by two hydrodynamic bearings independent of each other and arranged on either side of a median plane.

[0020] The invention proposes an improvement to this technology, which makes it possible to further improve the axial size of a mechanical reducer. Summary of the invention

[0021] The invention relates to a mechanical reducer for a turbomachine, in particular an aircraft, this reducer comprising:

[0022] - a solar having an axis of rotation,

[0023] - a crown that extends around the solar,

[0024] - satellites which are carried by a satellite carrier and which are meshed with the sun and the crown, each satellite comprising a first toothing having a first average diameter for meshing with the sun, and a second toothing having a second average diameter, different from the first average diameter, for meshing with the crown, the first and second toothings of each satellite having a symmetry with respect to a plane perpendicular to said axis and passing substantially through the middle of the satellite, the first toothing being cut in two by said plane or comprising two series of teeth arranged axially on either side of said plane, and the second toothing comprising two series of teeth arranged axially on either side of said plane and the first toothing, each of the satellites comprising a cylindrical sleeve and an annular web extending substantially radially outwards from the middle of this sleeve, the teeth of the second toothing being located at the axial ends of the sleeve,and the first toothing or teeth of the first toothing being located at the external periphery of the veil, ,

[0025] - hydrodynamic bearings for guiding the rotation of the satellites, these hydrodynamic bearings hydrodynamic bearings being configured to be supplied with oil and to form oil films for guiding the satellites, each of the satellites being guided by two hydrodynamic bearings independent of each other and arranged axially on either side of said plane,

[0026] characterized in that the two hydrodynamic guide bearings of each of the satellites are located around the sleeve of the satellite and axially on either side of the satellite web.

[0027] The invention proposes to guide each satellite by two hydrodynamic bearings. The guide bearings of the same satellite are at a distance and independent of each other. It is therefore understood that these bearings are shorter than a single guide bearing of a satellite, and also use less oil in operation due to their smaller axial dimension. The required oil flow rates are then considerably reduced, because the lengths of the bearings can be calculated to have exactly the load capacity required to take up the meshing forces and the centrifugal effects. In addition, by being spaced apart, the two bearings are much less sensitive to possible misalignments than a single bearing running the length of the satellite.

[0028] The particularity of the hydrodynamic bearings is that they are located outside the sleeve of each satellite and not inside this sleeve, as in the prior art. They are also arranged axially on either side of the web of each satellite. This makes it possible to use guide bearings of larger diameter compared to those of the prior art, and thus to improve the guidance of the satellites. The increase in the diameter of the bearings allows a reduction in their axial dimension without this having an impact on the extent of the guide surfaces of the satellites and on the quality of the guidance.

[0029] The invention thus makes it possible to reduce the axial size of the bearings, of the planet carrier comprising or carrying these bearings, and therefore of the reducer in general. This also makes it possible to improve the reliability of the reducer and to reduce the vibration levels within it.

[0030] 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: • said two hydrodynamic guide bearings of each of the satellites are located respectively radially in line with the first toothing or the series of teeth of the first toothing; • each of the two hydrodynamic guide bearings of each of the satellites is located axially between the first toothing or a series of teeth of the first toothing, and one of the series of teeth of the second toothing; • each of the two hydrodynamic guide bearings of each of the satellites cooperates with an internal cylindrical surface of the satellite web and / or with an external cylindrical surface of the satellite sleeve; • said internal cylindrical surface and / or said external cylindrical surface is capable of forming an oil film; • said internal cylindrical surface and said external cylindrical surface are arranged radially in line with each other;

[0031] — said two hydrodynamic guide bearings of each of the satellites each cooperate with an internal cylindrical surface of the external periphery of the veil, and in particular of a cylindrical rim of this veil; • said internal cylindrical surface has a diameter greater than a maximum diameter of the sleeve, or even also said second average diameter; • said internal cylindrical surface extends radially under one of the series of teeth of the first toothing and along an axial extent which represents between 30% and 70% of an axial extent of this series of teeth;

[0032] — said two hydrodynamic guide bearings of each of the satellites each cooperate with an external cylindrical surface of the sleeve;

[0033] — said external cylindrical surface of the sleeve has a diameter greater than said second average diameter and corresponding for example to a maximum diameter of the sleeve;

[0034] - said external cylindrical surface of the sleeve is located at a maximum diameter of the sleeve; • said external cylindrical surface of the sleeve extends radially under one of the series of teeth of the first toothing and along an axial extent which represents between 100% and 200% of an axial extent of this series of teeth; • said internal cylindrical surface and / or the external cylindrical surface is / are supplied with oil by lubrication channels formed in the planet carrier;

[0035] — the lubrication channels pass through the two hydrodynamic bearings; • said two hydrodynamic guide bearings of each of the satellites are formed in a single piece with the satellite carrier; • said two hydrodynamic guide bearings of each of the satellites respectively comprise two cylindrical bodies which are arranged around the sleeve of the satellite, axially on either side of the satellite web, and which are carried by the planet carrier; • said two hydrodynamic guide bearings of each of the satellites are supplied with oil by channels formed in the satellite carrier and / or in the cylindrical bodies; • the external periphery of the web comprises through oil discharge openings located axially on either side of said plane and preferably axially between the series of teeth of the first toothing;

[0036] — each of the satellites is guided by two or four oil films.

[0037] The invention further relates to a turbomachine, in particular for an aircraft, comprising a mechanical reducer as described above. Brief description of the figures

[0038] 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:

[0039] [Fig-1] [Fig.l] is a schematic axial sectional view of a turbomachine using the invention,

[0040] [Fig.2] [Fig.2] is a partial axial sectional view of a mechanical reducer,

[0041] [Fig.3] [Fig.3] is another partial axial sectional view of a reducer mechanical, and illustrates the art prior to the present invention,

[0042] [Fig.4] [Fig.4] is a schematic view in axial section and in perspective of a double-stage symmetrical mesh reducer, and also illustrates the prior art to the present invention,

[0043] [Fig.5] [Fig.5] is another schematic view in axial section of the reducer of the [Fig.4] ;

[0044] [Fig.6] [Fig.6] is a partial schematic view in axial section of a reducer according to one embodiment of the invention, and more particularly shows a satellite guided by hydrodynamic bearings carried by a satellite carrier;

[0045] [Fig.7] [Fig.7] is a partial schematic view in axial section of a reducer according to an alternative embodiment of the invention, and more particularly shows a satellite guided by hydrodynamic bearings carried by a satellite carrier;

[0046] [Fig.8] [Fig.8] is a partial schematic view in axial section of a reducer according to another variant embodiment of the invention, and shows more particularly a satellite guided by hydrodynamic bearings carried by a satellite carrier;

[0047] [Fig.9] [Fig.9] is a partial schematic view similar to that of [Fig.6] and representing the oil supply to the hydrodynamic bearings, and the oil removal from these bearings;

[0048] [Fig. 10] [Fig. 10] is a schematic view similar to that of [Fig.7] and representing the oil supply to the hydrodynamic bearings, and the evacuation of oil from these bearings;

[0049] [Fig. 11] [Fig. 11] is a schematic view similar to that of [Fig.8] and representing the oil supply to the hydrodynamic bearings, and the evacuation of oil from these bearings;

[0050] [Fig. 12] [Fig. 12] is a schematic axial sectional view of a reducer according to another variant embodiment of the invention, and shows more particularly a satellite guided by hydrodynamic bearings integrated in a satellite carrier;

[0051] [Fig. 13] [Fig. 13] is a partial schematic perspective view of a reducer according to the invention; and

[0052] [Fig. 14] [Fig. 14] is a partial schematic perspective view of a satellite for a reducer according to the invention. Detailed description of the invention

[0053] [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.

[0054] The blower S is driven by a fan shaft 4 which is driven by the LP shaft 3 by means of a reducer 6. This reducer 6 is generally of the planetary or epicyclic type.

[0055] The following description concerns a reducer of the epicyclic type, the planet carrier 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.

[0056] The reducer 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 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.

[0057] [Fig.2] shows an epicyclic reducer 6. At the input, the reducer 6 is connected to the LP shaft 3, for example via internal splines 7a. Thus, the LP shaft 3 drives a planetary pinion called the sun gear 7. Conventionally, the sun gear 7, whose axis of rotation coincides with 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.

[0058] The set of satellites 8 is held by a chassis called a planet carrier 10. Each satellite 8 rotates around its own Y axis, and meshes with the crown 9.

[0059] 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 attached to the fan shaft 4. • In another planetary configuration, all of the planet gears 8 are held by a planet gear carrier 10 which is fixed to the engine casing or stator 5. Each planet gear 8 drives the crown wheel which is attached to the fan shaft 4 via a crown wheel carrier 12. • In another differential configuration, all of the satellites 8 are held by a planet carrier 10 which is connected to a first fan shaft 5. Each satellite 8 drives the crown which is connected to a second counter-rotating fan shaft 4 via a crown carrier 12.

[0060] Each satellite 8 is mounted to rotate freely using a bearing 11, for example of the rolling bearing or hydrodynamic bearing type. Each bearing 11 is mounted on one of the axes 10b of the planet carrier 10 and all the axes are positioned relative to each other using one or more structural frames 10a of the planet carrier 10. There are a number of axes 10b and bearings 11 equal to the number of satellites. For reasons of operation, assembly, manufacturing, control, repair or replacement, the axes 10b and the frame 10a can be separated into several parts.

[0061] For the same reasons cited above, the teeth of a satellite can be separated into several helices or teeth each having a median plane P, P'. In our example, we detail the operation of a reducer in which each satellite comprises two series of chevron teeth cooperating with a crown separated into two half-crowns: • An upstream half-crown 9a consisting of a rim 9aa and a half-fixing flange 9ab. On the rim 9aa is the front propeller meshing with a propeller of the toothing 8d of each satellite 8. The propeller of the toothing 8d also meshes with that of the sun 7. • A downstream half-crown 9b consisting of a rim 9ba and a half-fixing flange 9bb. On the rim 9ba is the rear propeller meshing with a propeller of the toothing 8d of each satellite 8. The propeller of the toothing 8d also meshes with that of the sun 7.

[0062] If the helix widths vary between the sun gear 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 teeth and on another median plane P' for the downstream teeth.

[0063] [Fig.2] thus illustrates the case of a single-stage gear reducer, i.e. the same toothing 8d of each satellite 8 cooperates with both the sun gear 7 and the crown wheel 9. Even if the toothing 8d comprises two series of teeth, these teeth have the same average diameter and form a single toothing called a chevron.

[0064] 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.

[0065] 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 to the injector 13a to exit through the end 13c in order to lubricate the teeth. The oil is also brought to the arm 13b and circulates via the supply mouth 13d of the bearing. The oil then circulates through the shaft in one or more buffer zones 10c and then exits through the orifices 10d to lubricate the satellite bearings.

[0066] [Fig. 3] shows another example of a reduction gear architecture, called a double meshing stage, in which each satellite 8 comprises two separate teeth 8d1, 8d2 configured to cooperate respectively with the crown 9 and the sun gear 7.

[0067] In this [Fig.3], the elements already described in the above are designated by the same references.

[0068] The toothing 8dl for meshing with the crown 9 has an average diameter denoted D2 and is located in a median plane P. The toothing 8d2 for meshing with the sun 7 has an average diameter denoted DI and is located in another median plane P'. The median planes P, P' are parallel to each other and perpendicular to the axis X. The diameter D2 is less than the diameter DI. Finally, each toothing 8dl, 8d2 here comprises a single helix.

[0069] As mentioned above, this “double stage” architecture generates significant moments at the level of the satellites 8 in particular because this double stage has asymmetrical teeth.

[0070] Figures 4 and 5 show a reducer 60 with double symmetrical teeth, which makes it possible to solve the aforementioned problem.

[0071] This reducer 60 comprises:

[0072] - a solar 70 having an axis of rotation X,

[0073] - a crown 90 which extends around the solar and which is configured to be stationary in rotation around the X axis, and

[0074] - satellites 80 which are meshed with the sun 70 and the crown 90 and which are held by a planet carrier 100 which is configured to be rotatable around the X axis.

[0075] The plane H is defined as being a median plane perpendicular to the X axis and passing substantially in the middle of the reducer 60 ([Fig.5]).

[0076] The sun gear 70 comprises internal splines 70a for coupling with the LP shaft 30 as well as external teeth 70b for meshing with the planet gears 80. The teeth 70b have two series of axially adjacent teeth in a chevron pattern, separated from each other by an annular groove 72 oriented radially outwards. The teeth 70b are symmetrical with respect to the plane H, their teeth being located on either side of the plane H which passes through the groove 72.

[0077] The crown 90 is formed by two independent rings 90a, 90b and comprises a toothing which is separated into two series of teeth 90dl, 90d2 in a chevron pattern carried respectively by the two rings.

[0078] The rings 90a, 90b are arranged symmetrically with respect to the plane H which therefore extends between these rings. The rings are connected and fixed to a crown carrier 120 by means of annular connecting flanges 122. The flanges 122 are independent of one another, each flange having in axial half-section a general S-shape providing it with a certain radial flexibility by elastic deformation in operation.

[0079] Each ring 90a, 90b extends around the axis X and is fixed to the corresponding flange 122 by its external periphery. Its internal periphery comprises one of the teeth 90dl, 90d2.

[0080] The crown carrier 120 has a generally annular shape around the axis X and more particularly biconical. It thus comprises a first upstream section or on the left in the drawing, with an upstream end of smaller diameter, and a downstream end of larger diameter which is connected to the upstream end of larger diameter of the other section, downstream or on the right in the drawing. The larger diameter ends of the sections are therefore connected to each other, and their smaller diameter ends form the axial ends of the crown carrier.

[0081] The upstream end of the crown carrier 120 extends around the planet carrier 100 or a shaft connected to this planet carrier, and is centered and guided in rotation on the planet carrier or the shaft by means of at least one bearing 124. In the same way, the downstream end of the crown carrier 120 extends around the planet carrier 100 or a shaft connected to this planet carrier, and is centered and guided in rotation on the planet carrier or the shaft by means of at least one other bearing 126.

[0082] As is the case with the crown 90, the crown carrier 120 has a symmetry with respect to the plane H which cuts the crown carrier in its middle and therefore passes through the ends of larger diameter of the aforementioned sections.

[0083] Each satellite 80 comprises a first toothing 82 of average diameter DI for meshing with the sun gear 70, and a second toothing 84 of average diameter D2, different from DI and in particular less than D1, for meshing with the crown. 90. The average diameters are measured from the Y axis of each satellite and each represent the average between the maximum diameter and the minimum diameter of a tooth of this satellite.

[0084] Each satellite 80 comprises a cylindrical sleeve 86 and an annular web 88 extending substantially radially outwards from the middle of this sleeve 86. The toothing 84 is separated into two series of chevron teeth 84dl, 84d2 which are located respectively on the axial ends of the sleeve 86. The toothing 82 comprises two series of chevron teeth 82dl, 82d2 which are located at the external periphery of the web 88 and which are separated from each other by an annular groove 89 opening radially outwards relative to the axis Y.

[0085] The teeth 82 are crossed in their middle by the plane H which passes through the groove 89, the teeth 82dl, 82d2 therefore being arranged on either side of the plane H. The teeth 84dl, 84d2 are also arranged symmetrically with respect to the plane H.

[0086] The toothing 82 and the external periphery of the web 88 have an axial dimension which is less than the axial distance between the rings 90a, 90b, as well as between the flanges 122, so that each satellite 80 can freely rotate in the crown carrier 120 and between the rings 90a, 90b and the flanges 122.

[0087] In the variant illustrated in [Fig. 14], the first toothing 82 of each of the satellites 80 could comprise a single series of teeth, for example axial, which extend over the entire axial extent of the external periphery of the web, without interruption. This series of teeth would then be cut in two by the aforementioned plane H.

[0088] Each of the satellites 80 is guided in rotation by a hydrodynamic bearing 81 which comprises a cylindrical body 81a which passes through the satellite 80, and in particular its sleeve 86, and which is configured to form a film of guide oil inside the satellite.

[0089] The body 81a of a bearing 26 extends along the Y axis and comprises at its longitudinal ends extensions 81b housed in orifices forming seats of the planet carrier 100.

[0090] The body 81a is generally tubular and comprises an internal oil circulation bore which generally communicates with oil supply conduits to an external cylindrical surface of the body for the purpose of forming the oil film between this surface and an internal cylindrical surface of the satellite 80.

[0091] In the example shown which illustrates the prior art, the hydrodynamic bearing and the oil film extend over the entire length or axial dimension of the satellite 80.

[0092] The present invention proposes an improvement to this technology, embodiments of which are shown in Figures 6 to 8.

[0093] The reducer 60' of each of Figures 6 to 8 includes all of the features described above in relation to Figures 3, 4 and 5 in the provided that they are not contrary to or do not contradict what follows.

[0094] The references used in Figures 6 to 8 and already used in Figures 3, 4 and 5 therefore designate identical or similar elements.

[0095] In each of these reducers, the satellite 80 is of the double meshing stage type and comprises a tubular sleeve 86 connected by a web 88 to a first external toothing 82, the sleeve 86 itself being equipped with a second toothing 84.

[0096] The first toothing 82 has an average diameter D1 and meshes with the sun gear (not shown), and the second toothing 84 has an average diameter D2, different from DI and in particular less than D1, and meshes with the crown (not shown). The average diameters D1 and D2 are measured from the Y axis of each satellite 80 and represent the average between the maximum diameter and the minimum diameter of a toothing of this satellite.

[0097] The toothing 84 is separated into two series of teeth 84dl, 84d2, here in a herringbone pattern, which are located respectively on the axial ends of the sleeve 86. The toothing 82 comprises two series of teeth 82dl, 82d2, here also in a herringbone pattern, which are located at the external periphery of the web 88 and which are separated from each other by an annular groove 89 opening radially outwards relative to the axis Y.

[0098] The teeth 82 are crossed in their middle by the plane H which passes through the groove 89, the teeth 82dl, 82d2 therefore being arranged on either side of the plane H. The teeth 84dl, 84d2 are also arranged symmetrically with respect to the plane H.

[0099] Each of the satellites 80 is guided in rotation by two hydrodynamic bearings 81' which are independent of each other and arranged on either side of the plane H. The two hydrodynamic bearings 81' are located around the sleeve 86 of the satellite 80, and on either side of the web 88 of the satellite 80.

[0100] The following description concerns a satellite 80 and its hydrodynamic guide bearings 81' but it is understood that it applies to all the satellites 80 and hydrodynamic bearings 81' of the reducer 60'.

[0101] Advantageously, the bearings 81' are located respectively in line with the series of teeth 82d1, 82d2 of the first toothing 82, as can be seen in the drawings.

[0102] Also advantageously, the bearings 81' are located between the series of teeth 84d1, 84d2 of the second toothing 84.

[0103] The bearings 81' can each cooperate with an internal cylindrical surface and / or an external cylindrical surface of the satellite 80.

[0104] In the embodiment of [Fig.6], the bearings 81' each cooperate with an internal cylindrical surface 92 of the external periphery of the web 88, and in particular of a cylindrical rim 88a of this web 88. The web 88 comprises at its external periphery two cylindrical rims 88a, which extend axially on either side of the veil 88 and on each side of the plane H. The series of teeth 82dl, 82d2 of the first toothing 82 are located on the external periphery of these flanges 88a, and the internal surfaces 92 are located on the internal periphery of these flanges 88a.

[0105] In the example shown, the internal surfaces 92 each have a diameter D3 greater than a maximum diameter D4 of the sleeve 86 and than the second average diameter D2. D3 is also less than D1.

[0106] The internal surfaces 92 each extend under one of the series of teeth 82dl or 82d2 of the first toothing 82 and each have an axial extent L3 which represents between 80% and 100% of an axial extent L1 of this series of teeth 82dl or 82d2.

[0107] In the example shown, the bearings 81' respectively comprise two cylindrical bodies 81a' which are located around the sleeve 86 of the satellite 80, on either side of the web 88 of the satellite 80, and which are carried by the planet carrier 100.

[0108] Each of the bodies 81a' comprises an external cylindrical surface which cooperates with the corresponding internal surface 92 and which forms with this surface a thin annular space for forming a guide oil film.

[0109] Each of the bodies 81a' is housed in an orifice of the planet carrier 100, which is centered on the Y axis and is axially crossed by the sleeve 86 of the satellite 80.

[0110] In the example shown, each of the bodies 81a' has an internal diameter D5 which is significantly greater than the maximum external diameter D4 of the sleeve 86 and thus does not cooperate with the sleeve.

[0111] In the embodiment of [Fig.7], the bearings 81' each cooperate with an external cylindrical surface 93 of the sleeve 86.

[0112] In the example shown, the external surfaces 94 each have a diameter D4 which is greater than the second average diameter D2 and which is for example equal to the maximum diameter D4 of the sleeve. D4 is also less than DL

[0113] The external surfaces 94 each extend under one of the series of teeth 82dl or 82d2 of the first toothing 82 and each have an axial extent L4 which represents between 100% and 200% of an axial extent L1 of this series of teeth 82dl or 82d2. L4 can represent between 80 and 120% of L2 which is the axial extent of the second toothing 84.

[0114] In the example shown, the bearings 81' respectively comprise two cylindrical bodies 81a' which are located around the sleeve 86 of the satellite 80, on either side of the web 88 of the satellite 80, and which are carried by the planet carrier 100.

[0115] Each of the bodies 81a' comprises an internal cylindrical surface which cooperates with the corresponding external surface 94 and which forms with this surface a thin annular space for forming a guide oil film.

[0116] Each of the bodies 81a' is housed in an orifice of the planet carrier 100, which is centered on the Y axis and is axially crossed by the sleeve 86 of the satellite 80.

[0117] In the example shown, each of the bodies 81a' has an external diameter D6 which is close to the first average diameter D1.

[0118] In the embodiment of [Fig.8], the bearings 81' each cooperate with an internal cylindrical surface 92 of the external periphery of the web 88 and with an external cylindrical surface 93 of the sleeve 86.

[0119] More particularly, the bearings 81' each cooperate with an internal cylindrical surface 92 of a cylindrical rim 88a of this web 88. The web 88 has at its external periphery two cylindrical rims 88a, which extend axially on either side of the web 88 and on each side of the plane H. The series of teeth 82d1, 82d2 of the first toothing 82 are located on the external periphery of these rims 88a, and the internal surfaces 92 are located on the internal periphery of these rims 88a.

[0120] In the example shown, the internal surfaces 92 each have a diameter D3 greater than a maximum diameter D4 of the sleeve 86 and than the second average diameter D2. D3 is also less than DL

[0121] The internal surfaces 92 each extend under one of the series of teeth 82dl or 82d2 of the first toothing 82 and each have an axial extent L3 which represents between 30% and 70% of an axial extent L1 of this series of teeth 82dl or 82d2.

[0122] In the example shown, the external surfaces 94 each have a diameter D4 which is greater than the second average diameter D2 and which is for example equal to the maximum diameter D4 of the sleeve. D4 is also less than DL

[0123] The external surfaces 94 each extend under one of the series of teeth 82dl or 82d2 of the first toothing 82 and each have an axial extent L4 which represents between 100% and 200% of an axial extent L1 of this series of teeth 82dl or 82d2. L4 can represent between 80 and 120% of L2 which is the axial extent of the second toothing 84.

[0124] In the example shown, the bearings 81' respectively comprise two cylindrical bodies 81a' which are located around the sleeve 86 of the satellite 80, on either side of the web 88 of the satellite 80, and which are carried by the planet carrier 100.

[0125] Each of the bodies 81a' comprises an outer cylindrical surface which cooperates with the corresponding inner surface 92 and which forms with this surface a thin annular space for forming a first guide oil film, and each of the bodies 81a' further comprises an inner cylindrical surface which cooperates with the corresponding outer surface 94 and which forms with this surface a thin annular space for forming a second guide oil film.

[0126] Each of the bodies 81a' is housed in an orifice of the planet carrier 100, which is centered on the Y axis and is axially crossed by the sleeve 86 of the satellite 80.

[0127] In the example shown, each of the bodies 81a' has an external diameter D6 which is close to the first average diameter DL

[0128] Figures 9 to 11 show the circulation of the oil in the embodiments of Figures 6 to 8, and in particular the supply of oil to the bearings 81' and the surfaces 92, 94, as well as the evacuation of the oil.

[0129] The arrows F1 show the circulation of the oil for supplying the bearings 81' and in particular the surfaces 92, 94. For this, channels are formed in the bodies 81a' and are themselves connected to other supply channels for example.

[0130] The arrows F2 show the evacuation of the oil from the bearings 81', in particular from the surfaces 92, 94. For this, the external periphery of the web 88 may comprise through oil evacuation openings located on either side of the plane H and between the series of teeth 82d1, 82d2 of the first toothing 84.

[0131] In the embodiment variant of [Fig. 12], the bearings 81' each cooperate with an internal cylindrical surface 92 of the external periphery of the web 88, and in particular of a cylindrical rim 88a of this web 88, as in [Fig.6].

[0132] The variant of [Fig. 12] differs from the embodiment of [Fig. 6] essentially in that the bearings 81' are here integrated into the planet carrier s 100.

[0133] This variant makes it possible to visualize oil circulation and supply channels 96, which are formed in the bearings 81', as well as the aforementioned openings 98 formed in the external periphery of the web 88 for the purpose of discharging the oil.

[0134] [Fig. 13] is an exemplary embodiment of a mechanical reducer 60' comprising hydrodynamic bearings 81' for guiding the satellites as described above in relation to figures 6 to 12. The crown of the reducer 60' is not shown but may be similar to that of [Fig.5].

[0135] The reducer 60' has an overall shape which better fits the conical shape defined by the air stream of the engine, so there is less loss of space in the integration of the reducer.

[0136] Similarly, the planet carrier 100, which accommodates the hydrodynamic bearings 81' supporting the satellites 80, is therefore much shorter, since the distance between the hydrodynamic bearings 81' decreases. The planet carrier 100 therefore becomes less heavy and less bulky.

Claims

Claims

1. Mechanical reducer (60') for a turbomachine (1), in particular for an aircraft, this reducer comprising: - a sun (70) having an axis (X) of rotation, - a crown (90) which extends around the sun (70), - satellites (80) which are carried by a satellite carrier s (100) and which are meshed with the sun (70) and the crown (90), each satellite (80) comprising a first toothing (82) having a first average diameter for meshing with the sun (70), and a second toothing (84) having a second average diameter, different from the first average diameter, for meshing with the crown (90), the first and second toothings (82, 84) of each satellite (80) having a symmetry with respect to a plane (H) perpendicular to said axis (X) and passing substantially through the middle of the satellite (80), the first toothing (82) being cut in two by said plane (H) or comprising two series of teeth (82dl, 82d2) arranged axially on either side of said plane (H), and the second toothing (84) comprising two series of teeth (84dl,84d2) arranged axially on either side of said plane (H) and of the first toothing (82), each of the satellites (80) comprising a cylindrical sleeve (86) and an annular web (88) extending substantially radially outwards from the middle of this sleeve (86), the teeth (84dl, 84d2) of the second toothing (84) being located at the axial ends of the sleeve (86), and the first toothing (82) or the teeth (82dl, 82d2) of the first toothing (82) being located at the external periphery of the web (88), - hydrodynamic bearings (81') for guiding the rotation of the satellites (80), these hydrodynamic bearings (81') being configured to be supplied with oil and to form oil films for guiding the satellites (80), each of the satellites (80) being guided by two hydrodynamic bearings (81') independent of each other and arranged axially on either side of said plane (H) characterized in that the two hydrodynamic bearings (81') for guiding each of the satellites (80) are located around the sleeve (86) of the satellite (80) and axially on either side of the web (88) of the satellite (80).

2. Mechanical reducer (60') according to claim 1, in which said two hydrodynamic bearings (81') for guiding each of the satellites (80) are located respectively radially in line with the first toothing (82) or the series of teeth (82dl, 82d2) of the first toothing (82).

3. Mechanical reducer (60') according to claim 1 or 2, in which each of the two hydrodynamic bearings (81') for guiding each of the satellites (80) is located axially between the first toothing (82) or a series of teeth (82dl, 82d2) of the first toothing (82), and one of the series of teeth (84dl, 84d2) of the second toothing (84).

4. Mechanical reducer (60') according to one of the preceding claims, in which each of the hydrodynamic guide bearings (81') of each of the satellites (80) cooperates with an internal cylindrical surface (92) of the web (88) of the satellite (80) and / or with an external cylindrical surface (94) of the sleeve (86) of the satellite (80).

5. Mechanical reducer (60') according to claim 4, wherein said internal cylindrical surface (92) and / or said external cylindrical surface (94) is capable of forming an oil film.

6. Mechanical reducer (60') according to claim 4 or 5, wherein said internal cylindrical surface (92) and said external cylindrical surface (94) are arranged radially in line with each other.

7. Mechanical reducer (60') according to one of claims 4 to 6, wherein said internal cylindrical surface (92) has a diameter (D3) greater than a maximum diameter (D4) of the sleeve (86).

8. Mechanical reducer (60') according to one of claims 4 to 7, wherein said internal cylindrical surface (92) extends radially under one of the series of teeth (82dl, 82d2) of the first toothing (82) along an axial extent (L3) which represents between 30% and 70% of an axial extent (Ll) of this series of teeth (82dl, 82d2).

9. Mechanical reducer (60') according to one of claims 4 to 8, wherein said external cylindrical surface (94) of the sleeve (86) is located at a maximum diameter (D4) of the sleeve (88).

10. Mechanical reducer (60') according to one of claims 4 to 9, in which said external cylindrical surface (94) of the sleeve (86) extends radially under one of the series of teeth (82dl, 82d2) of the first toothing (82) and along an axial extent (L4) which represents between 100% and 200% of an axial extent (Ll) of this series of teeth (82dl, 82d2).

11. Mechanical reducer (60') according to one of claims 4 to 10, wherein said internal cylindrical surface (92) and / or the external cylindrical surface (94) is / are supplied with oil by lubrication channels- fication (96) formed in the planet carrier (100), preferably the lubrication channels (96) passing through the two hydrodynamic bearings (81').

12. Mechanical reducer (60') according to one of claims 1 to 11, in which said two hydrodynamic bearings (81') for guiding each of the satellites (80) are formed in a single piece with the planet carrier (100).

13. Mechanical reducer (60') according to one of claims 1 to 11, in which said two hydrodynamic bearings (81') for guiding each of the satellites (80) respectively comprise two cylindrical bodies (81a') which are arranged around the sleeve (86) of the satellite (80), axially on either side of the web (88) of the satellite (80), and which are carried by the planet carrier (100).

14. Mechanical reducer (60') according to one of the preceding claims, in which the external periphery of the web (88) comprises through oil discharge openings (98) located axially on either side of said plane (H) and preferably axially between the series of teeth (82dl, 82d2) of the first toothing (82).

15. Turbomachine (1), in particular for an aircraft, comprising a mechanical reducer (60') according to one of the preceding claims.