Moving ring gear for a mechanical reduction gear of an aircraft

Abstract

The invention relates to a moving ring gear (109, 209a) for a splash-lubricated mechanical reduction gear (106, 206), in particular for an aircraft, this ring gear (109, 209a) having an annular shape about a longitudinal axis (X) and comprising: - an annular body (130); and - an inner toothing (132), characterised in that it further comprises, on the outer periphery of the body (130), an annular row of oil scoops (136), these scoops (136) being distributed around the longitudinal axis (X) and projecting from an outer annular surface (134) of the body (130).

Description

[0001] DESCRIPTION

[0002] TITLE: MOVING CROWN FOR A MECHANICAL AIRCRAFT REDUCER

[0003] Technical field of the invention

[0004] The present invention relates to a movable crown for an aircraft mechanical reducer, and in particular for an aircraft turbomachine or for a drive system for a wheel of an aircraft landing gear.

[0005] Technical background

[0006] The state of the art includes in particular documents FR-A1 -3 025 780, FR- B1 -3 066 792, FR-B1 -3 071 023, FR-3 072 749, FR-A1 -3 095 243, FR-B1 - 3 098 562, FR-B1 -3 101 129, US-A-4,864,893 and US-B2-10,807,467.

[0007] 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.

[0008] New generations of dual-flow turbomachines, particularly those with a high bypass ratio, include a mechanical reducer to drive the shaft of a fan. Typically, the reducer is used 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.

[0009] A system for driving a wheel of a landing gear may further comprise a mechanical reducer, as proposed by the Applicant in document EP-A1-3 882 136.

[0010] 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 axis of the turbomachine or the wheel of a landing gear. The planet gears each have a different axis of revolution equally distributed over the same operating diameter around the axis of the planet gears. These axes are parallel to the longitudinal axis X.

[0011] There are several gearbox architectures. In the state of the art, gearboxes are planetary or epicyclic. In other similar applications, there are so-called differential or "compound" architectures.

[0012] - 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.

[0013] - 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.

[0014] - On a differential reducer, no element is fixed in rotation. The crown rotates in the opposite direction to the sun and the planet carrier.

[0015] 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. There are several types of contact meshing such as straight, helical or herringbone teeth.

[0016] 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.

[0017] A satellite may comprise one or two meshing stages. In the present application, the term "stage" or "toothing" means a series of meshing teeth with a series of complementary teeth. A toothing may be internal or external. A single-stage satellite comprises a toothing which may 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. A double-stage satellite comprises two toothings or two series of teeth which are located on different diameters. A first toothing cooperates with the sun gear and a second toothing cooperates with the crown gear.

[0018] There is also a configuration, called Wolfrom, in which the satellites are double-stage and have a first toothing that cooperates with the sun and a crown, and a second toothing that cooperates with a second crown. The reducer thus comprises two crowns, one of which is fixed and the other mobile.

[0019] A mechanical reducer must be lubricated to ensure its operation and also to evacuate the calories generated during operation. For this, lubricating oil is used.

[0020] There are two technologies for lubricating a mechanical reducer.

[0021] The first technology involves lubricating the gearbox using oil jets. The jets are supplied with oil and spray oil onto the gears, i.e., the teeth of the sun gear, the planet gears, and the crown(s). This oil is then drained and recovered for recycling.

[0022] Another technology is to use an oil splash reducer. The oil is permanently present in the reducer, which includes a sealed enclosure for retaining this oil. The oil level in the reducer enclosure is such that at least part of the planet gears, the planet carrier, and the crown gear(s) splash in the oil, i.e. are permanently bathed in the oil.

[0023] In a splash reducer, due to gravity, the oil flows and is stored in the lower part of the housing and the reducer. Therefore, the teeth located in the lower part are immersed in oil while the teeth in the upper part are not immersed in oil. During operation, the rotating elements contained in the housing rotate at high speeds and carry the oil. The oil tends to be centrifuged and form an oil ring inside the housing. One of the problems with a mechanical splash reducer is ensuring that all its gears are well lubricated.

[0024] The invention provides a simple, effective and economical solution to this problem.

[0025] Summary of the invention

[0026] The invention relates to a movable crown for a mechanical splash reducer, in particular for an aircraft, this crown having an annular shape around a longitudinal axis and comprising:

[0027] - an annular body, and

[0028] - internal teeth, characterized in that it further comprises at the external periphery of the body an annular row of oil scoops, these scoops being distributed around said longitudinal axis and projecting from an external annular surface of the body.

[0029] As mentioned above, during operation, an oil ring forms around the reducer and in particular around the movable crown if the rotation speeds are sufficient. The invention makes it possible, on the one hand, to promote the formation of this oil ring at lower rotation speeds and, on the other hand, to direct the flow of oil towards points requiring lubrication. The invention makes it possible to force the oil to move and, for example, to redirect it towards gears or bearings to be lubricated in the reducer. For this purpose, the crown comprises oil scoops on its periphery.

[0030] The solution proposed below is compatible with a single-stage or multi-stage reducer. It is compatible with a planetary, differential or Wolfrom type reducer. It is also compatible with straight, helical or herringbone teeth. It is compatible with any type of planet carrier, and in particular with a single-piece planet carrier. It is also compatible with any type of bearing, whether it is composed of rolling elements, a hydrodynamic bearing, etc. It is compatible with the use of the crown and the reducer in a double-flow turbomachine, for example for driving a fan or a propeller. It is also compatible with the use of the crown and the reducer in a system for driving a wheel of a landing gear.

[0031] The crown according to the invention may comprise one or more of the following features, taken in isolation from one another, or in combination with one another: body.

[0032] - the number of scoops is between 2 and 50;

[0033] - each of the scoops has a generally elongated shape;

[0034] - each of the scoops is fixed and comprises an elongation axis which is parallel to said longitudinal axis or which is inclined relative to this longitudinal axis;

[0035] - each of the scoops is mounted to rotate freely around a radial axis relative to said longitudinal axis, each of the scoops being configured to orient itself automatically according to the direction of rotation of the crown around said longitudinal axis and in contact with oil;

[0036] - the crown includes stops intended to limit the rotational travel of each of the scoops around their radial axis;

[0037] - the stops are formed by an annular rib projecting from said external annular surface of the body;

[0038] - each of the scoops comprises a first longitudinal portion in the form of a point or tapered, which extends over more than 30% of a length of the scoop, and a second longitudinal portion which is opposite the first portion and which is also in the form of a point or tapered, this second portion extending over more than 30% of said length;

[0039] - each of the scoops includes lateral sides which are flat or which are concavely curved;

[0040] - the scoops extend over an axial dimension measured along said longitudinal axis, which represents between 50 and 150%, and preferably between 80 and 120%, of an axial dimension of the internal teeth measured along the same axis;

[0041] -- the scoops are located outside the teeth and surround the teeth; -- each of the scoops can have a straight or alternatively curved shape, along their axis of elongation;

[0042] -- the pivoting stroke of each of the scoops is for example between 10 and 180°, and preferably between 60 and 120°;

[0043] - the external annular surface on which the scoops protrude is cylindrical, the scoops being directly located on this cylindrical surface.

[0044] The present invention also relates to a mechanical splash reducer, in particular for an aircraft, this reducer comprising:

[0045] - a mobile solar system rotating around a longitudinal axis,

[0046] - a first crown as described below, mounted around the solar and said longitudinal axis,

[0047] - satellites mounted between the sun and the crown and meshed with the sun and the crown, these satellites having axes of rotation parallel to said axis and being carried by a satellite carrier, and

[0048] - a sealed enclosure in which the solar, the first ring, the satellites and the planet carrier are located, this enclosure containing oil so that at least a portion of the first ring, the satellites and the planet carrier splashes in this oil, the first ring being rotatable about said longitudinal axis so that the oil scoops of this ring drive oil during rotation of the ring. In a Wolfrom or differential configuration, the planet carrier is rotatable about the longitudinal axis. In a planetary configuration, the planet carrier is fixed with respect to the longitudinal axis.

[0049] Advantageously, the satellites are double-stage and comprise a first stage meshed with the first crown and the sun, and a second stage meshed with a second crown which is fixed with respect to said longitudinal axis.

[0050] The invention further relates to a turbomachine or a system for driving a landing gear wheel, in particular an aircraft wheel, comprising at least one crown or mechanical reducer as described above.

[0051] Brief description of the figures

[0052] 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:

[0053] [Fig.1] Figure 1 is a schematic axial sectional view of an aircraft turbomachine,

[0054] [Fig.2] Figure 2 is a partial schematic view in axial section of a planetary mechanical reducer with oil jets,

[0055] [Fig.3] Figure 3 is a partial schematic view in axial section of a planetary mechanical splash reducer,

[0056] [Fig.4] Figure 4 is a partial schematic view in axial section of a Wolfrom mechanical splash reducer,

[0057] [Fig.5] Figure 5 is a partial schematic perspective view of a mobile crown according to a first embodiment of the invention,

[0058] [Fig.6] Figure 6 is a view similar to that of Figure 5 and illustrates the operation of the reducer and the rotation of the crown,

[0059] [Fig.7] Figure 7 is a view similar to that of Figure 5 and illustrates an alternative embodiment of the invention,

[0060] [Fig.8] Figure 8 is a larger-scale schematic view of part of the crown of Figure 7,

[0061] [Fig.9a-9b] Figures 9a and 9b are views similar to that of Figure 8 and illustrate another alternative embodiment of the invention, the scoop having a first position around its pivot axis, [Fig.10a-1 Ob] Figures 10a and 10b are other views of the alternative embodiment of Figures 9a and 9b, the scoop having a second position around its pivot axis, and

[0062] [Fig.11] Figure 11 is a schematic perspective view of a wheel of an aircraft landing gear and a drive system for this wheel.

[0063] Detailed description of the invention

[0064] Figure 1 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 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 1e are connected by a low-pressure shaft 3 and form with it a low-pressure (LP) body.

[0065] The blower S is driven by a blower shaft 4 which is rotated with the LP shaft 3 by means of a reducer 6. This reducer 6 can be of the planetary, epicyclic or Wolfrom type for example.

[0066] Although the following description concerns a planetary or epicyclic type reducer, it also applies to a mechanical differential in which the three components, namely the planet carrier, the crown wheel and the sun gear, are mobile in rotation, the rotation speed of one of these components depending in particular on the difference in speeds of the other two components. It also applies to the particular case of a double-stage reducer of the Wolfrom type.

[0067] 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.

[0068] Figure 2 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 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 is the same as that of the turbomachine X, drives a series of pinions called satellites 8, which are 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.

[0069] The set of satellites 8 is held by a satellite carrier 10. Each satellite 8 rotates around its own Y axis, and meshes with the crown 9.

[0070] At the output we have:

[0071] ■ in an epicyclic configuration, the set of satellites 8 rotates the planet carrier 10 around the axis X of the turbomachine. The crown is fixed to the engine casing or stator 5 via a crown carrier 12 and the planet carrier 10 is fixed to the fan shaft 4.

[0072] ■ in a 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 drives the crown wheel which is attached to the fan shaft 4 via a crown wheel carrier 12.

[0073] Each satellite 8 is mounted to rotate freely using a bearing 11, for example of the rolling bearing 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 X. They are axially spaced from each other and receive between them the bearings 11, the satellites 8 and the solar 7.

[0074] There are 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 parts.

[0075] For the same reasons mentioned above, the 8d toothing of a reducer can be separated into several helices, each having a median plane P. In our example, we detail the operation of a multi-helix reducer with a crown separated into two half-crowns:

[0076] ■ an upstream half-crown 9a consisting of a rim 9aa and a fixing half-flange 9ab. On the rim 9aa is the upstream helix of the gear teeth. This upstream helix meshes with that of the satellite 8 which meshes with that of the solar 7.

[0077] ■ a downstream half-crown 9b consisting of a rim 9ba and a half-fixing flange 9bb. On the rim 9ba is the downstream helix of the gear teeth. This downstream helix meshes with that of the satellite 8 which meshes with that of the solar 7.

[0078] If the propeller 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 propellers and on another median plane P for the downstream propellers.

[0079] 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.

[0080] Alternatively, the flange 9c of the crown 9 could be replaced by splines. 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 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 by 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 to injectors 13a to exit through ends 13c in order to lubricate with oil the teeth of the satellites 8, the sun 7 and also the crown 9. The oil is also brought to 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 guide surface of the corresponding satellite.

[0081] The reducer 6 in Figure 2 is thus a reducer of the type with oil jets or injectors.

[0082] On the contrary, the present invention relates to a splash type reducer, two examples of which are illustrated in Figures 3 and 4.

[0083] In Figure 3, the reducer 106 is a splash planetary reducer, that is to say that its ring gear 109 is movable and its planet carrier 110 is fixed. As seen in this figure, the reducer 106 is enclosed in a sealed enclosure Q.

[0084] The enclosure Q may be formed by one or more annular casings 120, 122 assembled together. Sealing is ensured by seals 124 or the like which are, for example, located:

[0085] - between the casing 120, 122 of the enclosure Q and the solar 107 or the shaft secured to the solar or coupled with the solar,

[0086] - between the crown 109 or the crown carrier 112 and the casing 120, 122 of the enclosure Q.

[0087] When stopped, the oil H1 contained in the enclosure Q is located in the lower part of the reducer 106 and in particular of the enclosure Q. A part of the crown 109, the satellites 108 and the planet carrier 110 bathe or splash in this oil. In operation, a ring of oil H2 forms inside the enclosure Q, all around the axis X.

[0088] In Figure 4, the reducer 206 is a Wolfrom splash reducer, that is, it comprises two crowns 209a, 209b, namely a movable crown 209a and a fixed crown 209b. As seen in this figure, the reducer 206 is also enclosed in a sealed enclosure Q.

[0089] The satellites 208 are double-stage and comprise a first stage 208a meshed with the first ring 209a and the sun gear 207, and a second stage 208b meshed with a second ring 209b which is fixed with respect to said longitudinal axis X.

[0090] The enclosure Q may be formed by one or more annular casings 220, 222 assembled together. The fixed crown 209b is here fixed to the casing(s) 220, 222 of the enclosure Q, and in particular interposed between two casings 220, 222 of the enclosure Q.

[0091] The seal is ensured by annular seals 225 or similar which are for example located:

[0092] - between the casing 220, 222 of the enclosure Q and the solar 207 or the shaft secured to the solar or coupled with the solar,

[0093] - between the casing 220, 222 of the enclosure Q and the movable crown 209a, and

[0094] - between the mobile crown 209a and the solar 207 or the shaft secured to the solar or coupled with the solar,

[0095] There may also be seals between the planet carrier 210 and the solar 207 or the shaft secured to the solar or coupled with the solar, as well as between this solar 207 or this shaft and the movable crown 209a or the element secured in rotation to the movable crown.

[0096] The rotating mobile elements are guided by rolling bearings 224 which are for example located:

[0097] - between the casing 220, 222 of the enclosure Q and the movable crown 209a,

[0098] - between the housing 220, 222 of the enclosure and the planet carrier 210, - between the planet carrier 20 and the satellites 208, and

[0099] - between the mobile crown 209a and the solar 207 or the shaft secured to the solar or coupled with the solar.

[0100] When stopped, the oil H1 is located in the lower part of the reducer 206 and in particular of the enclosure Q. A part of the crowns 209a, 209b, the satellites 208 and the planet carrier 210 are immersed or splashed in this oil. In operation, a ring of oil H2 forms inside the enclosure Q, all around the axis X.

[0101] The present invention relates to a movable crown 109, 209a for an aircraft mechanical reducer 106, 206. Insofar as the crown 109, 209a is movable, the reducer 6 can be of the planetary, differential or Wolfrom type. Furthermore, this reducer 106, 206 can be used in a turbomachine 1 such as that illustrated in FIG. 1, for driving a fan S, or in another context such as in a system for driving a wheel for an aircraft landing gear (see FIG. 11).

[0102] It should be noted that the crown 109, 209a according to the invention may be the only crown of the reducer 106, as in a planetary reducer 109. Alternatively, the reducer 206 could comprise two crowns including a movable crown 209a according to the invention, and a fixed crown 209b, or two movable crowns according to the invention.

[0103] Figures 5 and 6 illustrate a first embodiment of a crown 109, 209a according to the invention, and Figures 7 to 10 illustrate alternative embodiments of this crown 109, 209a.

[0104] The crown 109, 209a is preferably metallic. Its main material is therefore a metal alloy.

[0105] The crown 109, 209a has an annular shape around the X axis and comprises:

[0106] - an annular body 130, - an internal toothing 132, for example at the internal periphery of the body 130. The body 130 of the crown is not entirely shown. The body 130 may have a general L-shape in axial section and comprise a cylindrical wall 130a, one end of which is connected to a flange (as in figure 3) or to a radial or frustoconical wall 130b (as in figure 4).

[0107] In the example shown, the toothing 132 projects from an internal cylindrical surface 134 of the wall 130a.

[0108] The wall 130b can be used to fix the crown 109, 209a to an element which must be driven in rotation around the X axis. In the case of Figure 3, this is the crown carrier 112 which is connected to a fan propeller for example. In the case of Figure 4, this is for example a drive shaft of the wheel rim.

[0109] The particularity of this crown 109, 209a is that it further comprises oil scoops 136 at the external periphery of the body 130.

[0110] The crown 109, 209a comprises an annular row of these oil scoops 136 which are distributed around the axis X and which project from the external cylindrical surface 134 of the body 130.

[0111] It can be seen in the drawings that the scoops 136 are located outside the toothing 132 and surround this toothing 132.

[0112] The number of scoops 136 is for example between 2 and 50.

[0113] Each of the scoops 136 preferably has a generally elongated shape.

[0114] Each of the scoops 136 may have a rectilinear shape or alternatively a curved shape, along their elongation axis Z.

[0115] Each of the scoops 136 comprises a first longitudinal end 136a and a second longitudinal end 136b. The end 136a may be located in a plane perpendicular to the axis X, which passes through a longitudinal end 132 of the toothing 132 or even through a free longitudinal end 130c of the body 130.

[0116] The scoops 136 may extend over an axial dimension L1 measured along the axis X, which represents between 50 and 150%, and preferably between 80 and 120%, of an axial dimension L2 of the teeth 130 measured along the same axis.

[0117] Depending on the configurations, each of the scoops 136 is fixed and its elongation axis Z is parallel to the longitudinal axis X (see figures 7 and 8) or is inclined relative to this longitudinal axis X (see figures 5 and 6).

[0118] Each of the scoops 136 may include side flanks 136c that are flat (see Figures 5 and 6) or that are concave curved (see Figures 7 and 8). Having scoops 136 with concave or hollow sides allows more oil to be carried away during operation.

[0119] According to another configuration illustrated in figures 9a to 10b, each of the scoops 136 is mounted to rotate freely around a radial axis F relative to the axis X. Each of the scoops 136 is then configured to orient itself automatically according to the direction of rotation of the crown 109, 209a around the axis X and in contact with oil.

[0120] Figures 9a to 10b illustrate the same oil scoop 136 in two distinct positions. In Figures 9a and 9b, the scoop 136 is in a first position, and in Figures 10a and 10b, the scoop 136 is in a second position. The pivoting travel of the scoop 136 around the axis F is for example between 10 and 180°, and preferably between 60 and 120°. This travel is delimited by stops present on the body 130 of the crown 109, 209a and intended to limit the rotation travel of each of the scoops 136 around their radial axis F.

[0121] In the example shown, the stops are formed by an annular rib 138 projecting from the external annular surface 134 of the body 130.

[0122] Each of the scoops 136 may comprise a first longitudinal portion 140 in the form of a point or tapered, which extends over more than 30% of a length L1 ' of the scoop 136 (measured along its elongation axis Z), and a second longitudinal portion 142 which is opposite the first portion 140 and which is also in the form of a point or tapered, this second portion 142 extending over more than 30% of the length L1 . The operation of the crown 109, 209a according to the invention is similar regardless of its embodiment. This operation is schematically represented in FIG. 6.

[0123] At start-up and during operation, the crown 109, 209a rotates around the X axis and its lower part is immersed in the oil H1 present in the reducer 106, 206 or arranged all around the reducer in its enclosure. The scoops 136 of the crown 109, 209a force the oil to move (arrows T) and direct this oil in a predetermined direction, for example towards gears to be lubricated. The gearing to be lubricated is for example that between the satellites and the fixed crown in the context of a Wolfrom type reducer.

[0124] Alternatively, the scoops 136 could simply collect oil from the lower part and bring it to the upper part. Once at the top, the oil could trickle down onto the elements requiring lubrication.

[0125] When the scoops 136 are fixed, as in the embodiments of FIGS. 5 and 8, the scoops 136 are oriented according to the direction of rotation of the crown 109, 209a.

[0126] When the scoops 136 are movable, as in the embodiment variant of figures 9a to 10b, the scoops 136 are automatically oriented according to the direction of rotation of the crown 109, 209a and in contact with the oil. This solution makes it possible to carry a larger quantity of oil, in comparison with the oil driven in rotation by the teeth. It is then better distributed in the reducer towards the stations to be lubricated.

[0127] Figure 11 shows a system 310 for driving at least one wheel 312 of an aircraft landing gear 314.

[0128] The wheel 312 comprises a rim 316 which has an axis of rotation X. Conventionally, this rim 316 has a generally tubular or disc shape and carries a tire 318 at its periphery. The system 310 comprises an electric motor 320 and a mechanical transmission system 322 between a shaft of the motor 320 and the rim 316 of the wheel 312.

[0129] In the example shown, the motor 320 and the system 322 each have a generally annular shape and are centered on the X axis. They are arranged next to each other and the system 322 is installed between the motor 320 and the rim 316. A part of the system 322, or even also a part of the motor 320, could be housed in the rim 16 to reduce the size of the system 310. The motor 320 and the system 322 can be protected by an external cylindrical cover 326 projecting on one side of the rim 316 or the tire 318.

[0130] The mechanical transmission system 322 comprises a mechanical reducer 328 similar to the reducer 106, 206 described above and including a crown 109, 209a within the meaning of the invention.

Claims

CLAIMS 1. Movable crown (109, 209a) for a mechanical reducer (106, 206) with splashing, in particular for an aircraft, this crown (109, 209a) having an annular shape around a longitudinal axis (X) and comprising: - an annular body (130), - an internal tooth (132), and - an annular row of oil scoops (136) at the outer periphery of the body (130), these scoops being distributed around said longitudinal axis (X), characterized in that the scoops (136) have a generally elongated shape and project from an outer annular surface (134) of the body (130), each of the scoops (136) comprising an elongation axis (Z) which is parallel or inclined relative to said longitudinal axis (X).

2. Crown (109, 209a) according to claim 1, in which the number of scoops (136) is between 2 and 50.

3. Crown (109, 209a) according to claim 1 or 2, in which each of the scoops (136) is fixed.

4. Crown (109, 209a) according to claim 1 or 2, in which each of the scoops (136) is mounted to rotate freely around a radial axis (F) relative to said longitudinal axis (X).

5. Crown (109, 209a) according to claim 4, in which it comprises stops intended to limit the rotational travel of each of the scoops (136) around their radial axis (F).

6. Crown (109, 209a) according to claim 5, in which the stops are formed by an annular rib (138) projecting on said external annular surface (134) of the body (130).

7. Crown (109, 209a) according to one of the preceding claims, in which each of the scoops (136) comprises a first longitudinal portion (140) in the form of a point or tapered, which extends over more than 30% of a length (L1 ') of the scoop, and a second longitudinal portion (142) which is opposite the first portion and which is also in the form of a point or tapered, this second part (142) extending over more than 30% of said length (L1 ').

8. Crown (90) according to one of the preceding claims, in which each of the scoops (136) comprises lateral flanks (136c) which are flat or which are concavely curved.

9. Crown (90) according to one of claims 1 to 3, in which the scoops (136) extend over an axial dimension (L1) measured along said longitudinal axis (X), which represents between 50 and 150%, and preferably between 80 and 120%, of an axial dimension (L2) of the internal toothing (132) measured along the same axis (X).

10. Crown (90) according to one of the preceding claims, in which the external annular surface (134) on which the scoops (136) project is cylindrical, the scoops (136) being directly located on this cylindrical surface (134).

11. Mechanical splash reducer (106, 206), in particular for an aircraft, this reducer (106, 206) comprising: - a solar (107, 207) mobile in rotation around a longitudinal axis (X), - a first crown (109, 209a) according to one of the preceding claims, mounted around the solar (107, 207) and said longitudinal axis (X), - satellites (108, 208) mounted between the sun gear (107, 207) and the crown gear (90) and meshed with the sun gear and the crown gear, these satellites (108, 208) having axes of rotation (Y) parallel to said axis (X) and being carried by a planet carrier (110, 210), and - a sealed internal enclosure (Q) in which the solar (107, 207), the first crown (109, 209a), the satellites (108, 208) and the satellite carrier (110, 210) are located, this enclosure (Q) containing oil (H1, H2) so that at least a part of the first crown (109, 209a), the satellites (108, 208) and the satellite carrier (110, 210) splashes in this oil (H1, H2), the first crown (109, 209a) being movable in rotation about said longitudinal axis (X) so that the oil scoops (136) of this crown (109, 209a) carry oil when rotating the crown (109, 209a).

12. Reducer (206) according to claim 11, wherein the satellites (208) are double-stage and comprise a first stage (208a) meshed with the first crown (209a) and the sun gear (207), and a second stage (208b) meshed with a second crown gear (209b) which is fixed with respect to said longitudinal axis (X).

13. Turbomachine (1), in particular for an aircraft, comprising at least one crown (109, 209a) according to one of claims 1 to 10 or a mechanical reducer (106, 206) according to claim 11 or 12.

14. Drive system (310) for a wheel (312) of landing gear (314), in particular for an aircraft, comprising at least one crown (109, 209a) according to one of claims 1 to 10 or a mechanical reducer (106, 206) according to claim 11 or 12.

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