Aircraft twin-propeller turbine engine

Abstract

The invention relates to a twin-propeller turbine engine (101) for an aircraft, this turbine engine (101) having a main axis (X) and comprising: - a first propeller (S1); - a second propeller (S2); - a gas generator comprising a power transmission mechanism, a first shaft (104a) for rotating the first propeller (S1) about the main axis (X) and a second shaft (104b) for rotating the second propeller (S2) about the main axis (X), characterised in that the power transmission mechanism is a mechanical differential (160).

Description

[0001] DESCRIPTION

[0002] TITLE: AIRCRAFT TURBOMACHINE WITH DOUBLE PROPULSION PROPELLER

[0003] Technical field of the invention

[0004] The present invention relates to the field of twin-propeller propulsion turbomachines for an aircraft.

[0005] Technical background

[0006] The state of the art includes in particular documents W0-A1 -2010 / 092263, US-B2-11,492,979, FR-A1-2 987 416, FR-A1 -3 008 462, FR-A1-3 008 462 and FR-A1 -3 041 054.

[0007] An aircraft turbomachine generally includes a propulsion propeller called a fan, which is rotated by a shaft of a gas generator to generate thrust to propel the aircraft.

[0008] Double propeller propulsion turbomachines are also known, for example of the Open Rotor type. The propellers are driven by shafts of the gas generator and can be co-rotating or counter-rotating, i.e. they can rotate in the same direction or in opposite directions around the same axis. The propellers can be located upstream or downstream of the gas generator.

[0009] Furthermore, it is known to use a power transmission mechanism, generally of the mechanical reducer type, in an aircraft turbomachine.

[0010] The role of a mechanical reducer is to modify the speed and torque ratio between the input shaft and the output shaft of a mechanical system.

[0011] New generations of dual-flow turbomachines, particularly those with a high bypass ratio, include a mechanical reducer to drive the fan shaft. Typically, the reducer's purpose is to transform the so-called fast rotation speed of a power turbine shaft into a slower rotation speed for the shaft driving the fan.

[0012] Such a reducer comprises a central pinion, called a sun gear, a crown gear and pinions called planet gears, which are meshed between the sun gear and the crown gear. The planet gears are held by a frame called a planet carrier. The sun gear, the crown gear and the planet carrier are planet gears because their axes of revolution coincide with the main or longitudinal axis X of the turbomachine. The planet gears each have a different axis of revolution and are equally distributed over the same operating diameter around the axis of the planet gears. These axes are parallel to the longitudinal axis X.

[0013] There are several gearbox architectures. In the state of the art of double-flow turbomachinery, gearboxes are of the planetary or epicyclic type. In other similar applications, there are so-called differential or "compound" architectures.

[0014] - 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 to the solar.

[0015] - 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.

[0016] - On a differential reducer, no element is fixed in rotation. The crown rotates in the opposite direction to the sun and the planet carrier.

[0017] Gearboxes can be composed of one or more meshing stages. This meshing is ensured in different ways such as by contact, friction or even magnetic fields.

[0018] In this application, the term "stage" means a toothing which is configured to be meshed with a complementary toothing. A toothing can be internal or external.

[0019] A satellite can have one or two meshing stages. A single-stage satellite has a toothing that 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.

[0020] A double-stage satellite consists of two sets of teeth that are located on different diameters. One set of teeth cooperates with the sun gear and a second set of teeth cooperates with the crown gear.

[0021] Each of the teeth of a satellite can comprise a single series of teeth or two independent series of teeth, that is to say at an axial distance from each other. A satellite has already been proposed whose meshing teeth with the sun comprise two series of teeth arranged on either side of a median plane of the satellite, and whose meshing teeth with the crown also comprise two series of teeth arranged on either side of this plane, the two teeth of each satellite having different diameters.

[0022] A double-stage gear reducer has the advantage of having a higher reduction ratio than a single-stage gear reducer of the same size. However, a disadvantage of this type of reducer is the moment generated in the planet gears by differences in forces applied to the planet gear stages.

[0023] The invention proposes a power transmission mechanism solution, which is particularly suitable for the rotational drive of the propulsion propellers of a turbomachine.

[0024] Summary of the invention

[0025] The invention relates to a twin-propeller propulsion turbomachine for an aircraft, this turbomachine having a main axis and comprising:

[0026] - a first propulsion propeller,

[0027] - a second propulsion propeller,

[0028] - a gas generator comprising a power transmission mechanism, a first drive shaft for rotating the first propeller around the main axis, and a second drive shaft for rotating the second propeller around the main axis, characterized in that the power transmission mechanism is a mechanical differential which comprises:

[0029] - a solar centered on the main axis and coupled with a gas generator shaft,

[0030] - a crown centered on the main axis and coupled to said first shaft,

[0031] - a planet carrier centered on the main axis and coupled to said second shaft, and

[0032] - satellites which are carried by the satellite carrier and which are meshed with the sun and the crown, each satellite having an axis of rotation parallel to the main axis and comprising a first meshing toothing with a toothing of the sun, and a second meshing toothing with a toothing of the crown, the first toothing of each satellite comprising two series of teeth which are axially spaced from each other and which are arranged on either side of a median plane of the satellite which is perpendicular to the axis of this satellite, the second toothing of each satellite comprising two series of teeth which are axially spaced from each other and which are arranged on either side of said median plane and series of teeth of the first toothing.

[0033] The invention therefore uses a mechanical differential as a power transmission mechanism, that is to say a mechanism in which all the elements (among the solar, the crown and the planet carrier) are mobile in rotation. The particularity of this differential is that its satellites are double-stage, which allows for a high reduction ratio.

[0034] The invention is notably compatible

[0035] • a multi-stage reducer;

[0036] • straight or herringbone teeth.

[0037] The turbomachine 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:

[0038] - the first toothing of each satellite has a diameter greater than that of the second toothing of the satellite; - the toothing of the sun comprises two series of teeth which are axially spaced from each other and which mesh respectively with the two series of teeth of the first toothing of each satellite;

[0039] - the crown gear teeth comprise two sets of teeth which are axially spaced from each other and which mesh respectively with the two sets of teeth of the second gear teeth of each satellite;

[0040] - the crown has an upstream half-crown and a downstream half-crown, the half-crowns being symmetrical and being arranged on either side of the series of teeth of the first toothing of each satellite;

[0041] - the propellers are counter-rotating;

[0042] - the first toothing of each satellite and the toothing of the sun gear are of the straight or herringbone type;

[0043] - the second toothing of each satellite and the toothing of the crown are herringbone;

[0044] - the satellites are guided by plain bearings of the satellite carrier;

[0045] - the satellite carrier comprises a single-piece cage, in which the satellites are housed;

[0046] - the first shaft extends around the second shaft and is guided in rotation around this second shaft by at least one bearing;

[0047] - the first shaft comprises a cylindrical portion which is connected to the crown by a crown carrier, the crown carrier comprising a cylindrical wall surrounding at least part of the crown and a frustoconical portion connecting the first shaft to the cylindrical wall, the cylindrical portion of the first shaft having a diameter less than the diameter of the cylindrical wall of the crown carrier or even less than the external diameter of the planet carrier;

[0048] - the cylindrical portion of the first shaft is formed in a single piece with the truncated and cylindrical walls of the crown carrier; - the second shaft comprises a cylindrical portion which is connected to a disc of the planet carrier, and which is for example formed in a single piece with this disc or with the planet carrier;

[0049] - each of the satellites is guided in rotation by a hydrodynamic bearing which comprises a cylindrical body which passes through the satellite, this body extending along the axis of rotation of the satellite and comprising at its longitudinal ends extensions housed in orifices forming seats of the satellite carrier;

[0050] -- the crown is the only crown of the differential;

[0051] -- the differential has no fixed crown.

[0052] Brief description of the figures

[0053] 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:

[0054] [Fig.1] Figure 1 is a schematic axial sectional view of a turbomachine,

[0055] [Fig.2] Figure 2 is a partial axial sectional view of a mechanical reducer,

[0056] [Fig.3] Figure 3 is another partial axial sectional view of a mechanical reducer, and illustrates the art prior to the present invention,

[0057] [Fig. 4] Figure 4 is a schematic axial sectional and perspective view of a double-stage symmetrical meshing reducer, and also illustrates the art prior to the present invention,

[0058] [Fig.5] Figure 5 is another schematic axial sectional view of the reducer of Figure 4;

[0059] [Fig.6] Figure 6 is a very schematic partial axial sectional view of a mechanical differential according to the invention,

[0060] [Fig.7] Figure 7 is a very schematic partial axial sectional view of a turbomachine according to the invention, [Fig.8] Figure 8 is a schematic perspective and axial sectional view of a differential for a turbomachine according to an embodiment of the invention, and

[0061] [Fig.9] Figure 9 is a schematic axial sectional view of one of the satellites of the differential of Figure 8.

[0062] Detailed description of the invention

[0063] Figure 1 describes a turbomachine 1 which comprises a gas generator comprising, in a conventional manner, a fan S, a low pressure compressor 1 a, a high pressure compressor 1 b, an annular combustion chamber 1 c, a high pressure turbine 1 d, a low pressure turbine 1 e and an exhaust nozzle 1 h. The high pressure compressor 1 b and the high pressure turbine 1 d are connected by a high pressure shaft 2 and form with it a high pressure (HP) body. The low pressure compressor 1 a and the low pressure turbine 1 e are connected by a low pressure shaft 3 and form with it a low pressure (LP) body.

[0064] The blower S is driven by a blower 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.

[0065] The following description concerns an epicyclic type reducer, the planet carrier and the sun gear of which are mobile in rotation, the crown of the reducer being fixed in the motor reference frame.

[0066] 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.

[0067] Figure 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.

[0068] The set of satellites 8 is held by a frame called a satellite carrier 10. Each satellite 8 rotates around its own Y axis, and meshes with the crown 9.

[0069] At the output, we have:

[0070] ■ In this epicyclic configuration, the set of planet gears 8 drives the planet carrier 10 in rotation around the axis X of the turbomachine. The ring gear is fixed to the engine casing or stator 5 via a ring gear carrier 12 and the planet carrier 10 is fixed to the fan shaft 4.

[0071] ■ In another planetary configuration, all of the planet gears 8 are held by a planet carrier 10 which is fixed to the engine casing or stator 5. Each planet gear 8 drives the crown which is attached to the fan shaft 4 via a crown carrier 12.

[0072] ■ 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 9 which is secured to the fan shaft 4 via the crown carrier 12.

[0073] Each planet gear 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 planet gears. For reasons of operation, assembly, manufacturing, control, repair or replacement, the axes 10b and the frame 10a can be separated into several parts. For the same reasons mentioned above, the teeth of a planet gear 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 planet gear comprises two series of chevron teeth cooperating with a crown separated into two half-crowns:

[0074] ■ An upstream half-crown 9a consisting of a rim 9aa and a fixing half-flange 9ab. On the rim 9aa is the upstream helix meshed with a helix of the toothing 8d of each satellite 8. The helix of the toothing 8d also meshes with that of the sun 7.

[0075] ■ A downstream half-crown 9b consisting of a rim 9ba and a half-fixing flange 9bb. On the rim 9ba is the downstream helix meshing with a helix of the toothing 8d of each satellite 8. The helix of the toothing 8d also meshes with that of the sun 7.

[0076] 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.

[0077] Figure 2 thus illustrates the case of a single-stage gear reducer 6, 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.

[0078] The half-clamp 9ab of the upstream crown 9a and the half-clamp 9bb of the downstream crown 9b form the crown mounting flange 9c. The crown 9 is fixed to a crown carrier by assembling the crown mounting flange 9c and the crown carrier mounting flange 12a using a bolted assembly for example.

[0079] The arrows in Figure 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 in order to lubricate the satellite bearings.

[0080] Figure 3 shows another example of the architecture of the reducer 6, called double meshing stage, in which each satellite 8 comprises two separate teeth 8d 1 , 8d2 configured to cooperate respectively with the crown 9 and the sun gear 7.

[0081] In this figure 3, the elements already described in the above are designated by the same references.

[0082] The toothing 8d 1 meshing with the crown 9 has an average diameter noted D2 and is located in a plane P. The toothing 8d2 meshing with the sun 7 has an average diameter noted D1 and is located in another plane P'. The planes P, P' are parallel to each other and perpendicular to the axis X. The diameter D2 is less than the diameter D1. Finally, each toothing 8d1, 8d2 here comprises a single helix or series of teeth.

[0083] 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.

[0084] Figures 4 and 5 show a 60 reducer with double symmetrical teeth, which makes it possible to solve the above problem.

[0085] This 60 reducer includes:

[0086] - a solar 70 having an axis of rotation X,

[0087] - a crown 90 which extends around the sun 70 and which is configured to be immobile in rotation around the X axis, and - 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 mobile in rotation around the X axis.

[0088] The plane H is defined as being a median plane perpendicular to the X axis and passing substantially through the middle of the reducer 60 (figure 5).

[0089] The solar 70 comprises internal splines 70a for coupling with the BP shaft 30 as well as external teeth 70b for meshing with the satellites 80. The teeth 70b have two series of 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.

[0090] The crown 90 is formed by two independent rings 90a, 90b and comprises a toothing 90d which is separated into two series of teeth 90d1, 90d2 in a chevron pattern carried respectively by the two rings.

[0091] 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.

[0092] Each ring 90a, 90b extends around the X axis and is fixed to the corresponding flange 122 by its outer periphery. Its inner periphery comprises one of the series of teeth 90d1, 90d2.

[0093] As is the case with the crown 90, the crown carrier 120 has symmetry with respect to the plane H.

[0094] Each satellite 80 has a first toothing 82 of average diameter D1 for meshing with the sun gear 70, and a second toothing 84 of average diameter D2, different from D1 and in particular less than D1, for meshing with the crown 90. The average diameters are measured from the Y axis of each satellite 80 and each represent the average between the maximum diameter and the minimum diameter of a toothing of this satellite.

[0095] 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 84d1, 84d2 which are located respectively on the axial ends of the sleeve 86. The toothing 82 comprises two series of chevron teeth 82d1, 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.

[0096] The teeth 82 are crossed in their middle by the plane H which passes through the groove 89, the teeth 82d1, 82d2 therefore being arranged on either side of the plane H. The teeth 84d1, 84d2 are also arranged symmetrically with respect to the plane H.

[0097] The teeth 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.

[0098] 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.

[0099] The body 81 a of a bearing 81 extends along the Y axis and comprises at its longitudinal ends extensions 81 b housed in orifices forming seats of the planet carrier 100.

[0100] The body 81 a is generally tubular and comprises an internal oil circulation cavity which generally communicates with first oil supply pipes to an external cylindrical surface of the body 81 a for the purpose of forming the oil film between this surface and an internal cylindrical surface of the satellite 80.

[0101] Figures 6 and 7 illustrate the general principle of the invention. Figure 6 shows a power transmission mechanism, which is no longer a mechanical reducer, but a mechanical differential 160. A mechanical differential 160 has a sun gear 70, a crown wheel 90 and a planet carrier 100 which are all rotatable.

[0102] Figure 6 shows the differential 160 alone and Figure 7 shows a turbomachine 101 comprising this differential 160.

[0103] The turbomachine 101 is similar to that of figure 1 so the preceding description in relation to figure 1 applies to the turbomachine 1 of figure 7. The particularity of the turbomachine 101 of figure 7 is that it comprises two propulsion propellers S1, S2, which are here coaxial, counter-rotating and mounted upstream of the gas generator.

[0104] The differential 160 of figures 6 and 7 includes:

[0105] - a solar 70 which has an axis of rotation centered on the main axis X of the turbomachine 101,

[0106] - a crown 90 which extends around the solar 70 and the X axis,

[0107] - satellites 80 which are meshed with the sun 70 and the crown 90, and

[0108] - a planet carrier 100 which has an axis of rotation coincident with the X axis and which carries bearings 81 for guiding the rotation of the satellites 80 around Y axes parallel to the X axis and distributed around this X axis.

[0109] The solar 70 is coupled to a shaft of the gas generator, which here is the low pressure shaft 3.

[0110] The crown 90 is coupled to a first shaft 104a for driving in rotation a first of the two propulsion propellers S1.

[0111] The planet carrier 100 is coupled to a second shaft 104b for driving the rotation of the second propulsion propeller S2.

[0112] In the example shown, the propeller S1 connected to the ring gear 90 is located downstream of the propeller S2 connected to the planet carrier 100. The shaft 104a extends around the shaft 104b and is guided in rotation on this shaft 104b by at least one or more bearings 200. The shaft 104a is further guided in rotation by one or more bearings 202 carried by a support 204 secured to a stator casing 206 of the turbomachine. This stator casing 206 extends around the differential 160 and is secured to another support 208 which carries one or more bearings 210 for guiding the rotation of the low-pressure shaft 3.

[0113] The propellers S1, S2 rotate around the same axis which is the X axis of the turbomachine 101.

[0114] Each satellite 80 has a Y axis of rotation parallel to the X axis and comprises a first toothing 82 for meshing with the sun gear 70, and a second toothing 84 for meshing with the crown 90.

[0115] The first toothing 82 of each satellite 80 comprises two series of teeth 82d1, 82d2 which are axially spaced from each other and which are arranged on either side of the median plane H of the satellite 80 (figures 8 and 9).

[0116] The second toothing 84 comprises two series of teeth 84d1, 84d2 which are axially spaced from each other and which are arranged on either side of the median plane H and separated from each other by the first toothing 82. The series of teeth 84d1, 84d2 of the second toothing 84 are thus arranged on either side of the first toothing 82.

[0117] The median plane H is perpendicular to the Y axis of the satellite 80 and can be a plane of symmetry of this satellite 80.

[0118] The first toothing 82 of each satellite 80 has a diameter D1 which is here greater than the diameter D2 of the second toothing 84 of the satellite 80. It can thus be seen that the satellites 80 of figures 8 and 9 are similar to those of figures 4 and 50. The preceding description therefore applies to these satellites 80.

[0119] In the example shown, each of the satellites 80 is formed from a single piece.

[0120] In Figures 8 and 9 which illustrate a more concrete embodiment of the invention, it can be seen that the toothing 70b of the sun gear 70 is formed by two series of teeth 70b1, 70b2 which are axially spaced from each other and which mesh respectively with the two series of teeth 82d1, 82d2 of the first toothing 82 of each satellite 80.

[0121] The crown 90 comprises a toothing 90d formed by two series of teeth 90d1, 90d2 which are axially spaced from each other and which mesh respectively with the two series of teeth 84d1, 84d2 of the second toothing 84 of each satellite 80.

[0122] Crown 90 is separated into two half-crowns:

[0123] ■ an upstream half-crown 190a consisting of a rim 190aa and a fixing half-flange 190ab. On the rim 190aa is the first series of teeth 90d1 of the toothing 90d which is meshed with one of the series of teeth 84d1 of the second toothing 84 of each satellite 80;

[0124] ■ a downstream half-crown 190b consisting of a rim 190ba and a fixing half-flange 190bb. On the rim 190ba is the second series of teeth 90d2 of the toothing 90d which is meshed with the other of the series of teeth 84d2 of the second toothing 84 of each satellite 80.

[0125] The two half-crowns 190a, 190b are symmetrical with respect to the plane H and are located on either side of the series of teeth 82d1, 82d2 of the first toothing 82 of each satellite 80.

[0126] The half-flanges 190ab, 190bb are fixed together to form the flange of the crown 90 and are also fixed to a flange of a crown carrier 120 connected to the drive shaft 104a of the propeller S1.

[0127] In the example shown, the shaft 104a comprises a cylindrical portion 104a1 which is connected to the crown 90 by the crown carrier 120. The crown carrier 120 comprises a cylindrical wall 120a which surrounds at least a portion of the crown 90, and in particular the half-crown 190a, and a frustoconical portion 120b connecting the first shaft 104a to the cylindrical wall 120a. The frustoconical wall 120b therefore widens downstream in the example shown.

[0128] The cylindrical portion 104a1 has a diameter D3 smaller than the diameter D4 of the cylindrical wall 120a or even smaller than the external diameter D5 of the planet carrier 100, as in the example shown. The cylindrical portion 104a1 of the first shaft 104a is preferably formed in a single piece with the frustoconical and cylindrical walls 120a, 120b of the crown carrier 120.

[0129] The shaft 104b comprises a cylindrical portion 104b1 which is connected to the disc 100a of the planet carrier 100, and which is for example formed in a single piece with this disc 100a or with the planet carrier 100. The portion 104b1 has a diameter D6 less than D3.

[0130] Alternatively, the crown 90 could also be formed from a single piece.

[0131] The series of teeth 82d1, 82d2, 70b1, 70b2 of the teeth 82, 70b are here in chevron or straight. The series of teeth 84d1, 84d2, 90d1, 90d2 of the teeth 84, 90 are here in chevron.

[0132] The planet carrier 100 comprises a cage delimited by two discs 100a connected by bridges 100b.

[0133] Cylindrical bodies 81a extend between the discs 100a and are fixed to these discs. The cylindrical bodies 81a are distributed around the X axis and define the Y axes. These bodies 81a respectively pass through the satellites 80 for the purpose of guiding them.

[0134] The satellites 80 are respectively centered and guided in rotation by smooth bearings on these cylindrical bodies 81 a.

[0135] Each of the bodies 81 a extends along the Y axis and comprises at its longitudinal ends extensions 81 b housed in orifices forming seats of the planet carrier 100.

[0136] Each body 81a is generally tubular and includes an internal oil circulation cavity which generally communicates with oil supply lines to an external cylindrical surface of the body 81a for the formation of the plain bearings.

[0137] The use of symmetrical double-stage 80 satellites limits the occurrence of moments on the bearings.

[0138] The cage formed by the discs 100a and the bridges 100b can also be formed in a single piece, as in the example shown. In a variant embodiment of the invention, not shown, the propellers could be located downstream of the turbomachine or at least in different positions than those illustrated in Figure 7. The differential according to the invention is adapted to provide high reduction ratios, for example greater than 5. It benefits from limited radial size, which facilitates its integration into a turbomachine. The turbomachine is preferably a double-flow turbomachine.

Claims

CLAIMS 1. Double propeller turbomachine (101) for propulsion of an aircraft, this turbomachine (101) having a main axis (X) and comprising: - a first propulsion propeller (S1), - a second propulsion propeller (S2), - a gas generator comprising a power transmission mechanism, a first shaft (104a) for driving the first propeller (S1) in rotation around the main axis (X), and a second shaft (104b) for driving the second propeller (S2) in rotation around the main axis (X), characterized in that the power transmission mechanism is a mechanical differential (160) which comprises: - a solar (70) centered on the main axis (X) and coupled with a shaft (3) of the gas generator, - a crown (90) centered on the main axis (X) and coupled to said first shaft (104a), - a planet carrier (100) centered on the main axis (X) and coupled to said second shaft (104b), and - satellites (80) which are carried by the planet carrier (100) and which are meshed with the sun (70) and the crown (90), each satellite (80) having an axis (Y) of rotation parallel to the main axis (X) and comprising a first toothing (82) for meshing with a toothing of the sun (70), and a second toothing (84) for meshing with a toothing of the crown (90), the first toothing (82) of each satellite (80) comprising two series of teeth (82d1, 82d2) which are axially spaced from each other and which are arranged on either side of a median plane (H) of the satellite which is perpendicular to the axis (Y) of this satellite (80), the second toothing (84) of each satellite (80) comprising two series of teeth (84d1, 84d2) which are axially spaced from each other and which are arranged on either side of said median plane (H) and series of teeth (82d1, 82d2) of the first dentition (82).

2. Turbomachine (101) according to the preceding claim, in which the first toothing (82) of each satellite (80) has a diameter (D1) greater than that of the second toothing (84) of the satellite (80).

3. Turbomachine (101) according to claim 1 or 2, in which the toothing (70b) of the sun gear (70) comprises two series of teeth (70b1, 70b2) which are axially spaced from each other and which mesh respectively with the two series of teeth (82d1, 82d2) of the first toothing (82) of each satellite (80).

4. Turbomachine (101) according to one of the preceding claims, in which the toothing (90d) of the crown (90) comprises two series of teeth (90d1, 90d2) which are axially spaced from one another and which mesh respectively with the two series of teeth (84d1, 84d2) of the second toothing (84) of each satellite (80).

5. Turbomachine (101) according to one of the preceding claims, in which the crown (90) has an upstream half-crown (190a) and a downstream half-crown (190b), the half-crowns (190a, 190b) being symmetrical and being arranged on either side of the series of teeth (82d1, 82d2) of the first toothing (82) of each satellite (80).

6. Turbomachine (101) according to one of the preceding claims, in which the propellers (S1, S2) are counter-rotating.

7. Turbomachine (101) according to one of the preceding claims, in which the first toothing (82) of each satellite (80) and the toothing (70b) of the sun (70) are of the straight or herringbone type.

8. Turbomachine (101) according to one of the preceding claims, in which the second toothing (84) of each satellite (80) and the toothing (90d) of the crown (90) are herringbone.

9. Turbomachine (101) according to one of the preceding claims, in which the satellites (80) are guided by plain bearings of the satellite carrier (100).

10. Turbomachine (101) according to one of the preceding claims, in which the planet carrier (100) comprises a single-piece cage, in which the satellites (80) are housed.

11. Turbomachine (101) according to one of the preceding claims, in which the first shaft (104a) extends around the second shaft (104b) and is guided in rotation around this second shaft (104b) by at least one bearing.

12. Turbomachine (101) according to one of the preceding claims, in which the first shaft (104a) comprises a cylindrical portion (104a1) which is connected to the crown (90) by a crown carrier (120), the crown carrier (120) comprising a cylindrical wall (120a) surrounding at least a portion of the crown (90) and a frustoconical portion (120b) connecting the first shaft (104a) to the cylindrical wall (120a), the cylindrical portion (104a1) of the first shaft (104a) having a diameter (D3) less than the diameter (D4) of the cylindrical wall (120a) of the crown carrier (120) or even less than the external diameter (D5) of the planet carrier (100).

13. Turbomachine (101) according to the preceding claim, in which the cylindrical portion (104a1) of the first shaft (104a) is formed in a single piece with the frustoconical and cylindrical walls (120a, 120b) of the crown carrier (120).

14. Turbomachine (101) according to one of the preceding claims, in which the second shaft (104b) comprises a cylindrical portion (104b1) which is connected to a disc (100a) of the planet carrier (100), and which is for example formed in a single piece with this disc (100a) or with the planet carrier (100).

15. Turbomachine (101) according to one of the preceding claims, in which 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), this body (81a) extending along the axis of rotation (Y) of the satellite and comprising at its longitudinal ends extensions (81b) housed in orifices forming seats of the planet carrier (100).

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