DRIVE DEVICE FOR AT LEAST ONE WHEEL OF AN AIRCRAFT LANDING GEAR

Abstract

A device (10) for driving at least one wheel (12) of an aircraft landing gear (14), this device (10) comprising: - at least one landing gear wheel (12), - an electric motor (20) comprising a shaft (30), - a mechanical transmission system (22) between the motor shaft (20) and the wheel rim (16), this mechanical transmission system (22) comprising a mechanical reduction gear (28) which includes: - two-stage meshing planet gears (34) having a first set of teeth (34a) and a second set of teeth (54a), - a fixed sun gear (32) which is meshed with one of the first and second sets of teeth (34a, 54a), - a movable sun gear (56) which is meshed with the other of the first and second sets of teeth (54a, 34a), and - a movable ring gear (38) which is meshed with one or the other of the first and second gears (34a, 54a). Figure for the abbreviation: Figure 6

Description

Title of the invention: DEVICE DRIVE OF AT LEAST ONE WHEEL OF AN AIRCRAFT LANDING GEAR Technical field of the invention

[0001] The present invention relates to a drive device for at least one wheel of an aircraft landing gear. Technical background

[0002] An aircraft includes landing gear equipped with wheels for moving the aircraft on the ground on a tarmac. This taxiing, also called taxiing, can be achieved by propelling the aircraft using its turbomachinery.

[0003] To limit fuel consumption and environmental impact, it is known to perform this taxiing electrically. Electric taxiing is achieved by driving the wheels of a landing gear with an electric motor.

[0004] The present application proposes an improvement to existing technologies and thus relates to an electric motor device for driving at least one wheel of an aircraft landing gear.

[0005] A solution consisting of using a reducer to transmit the power of an electric motor to a wheel of a landing gear was proposed by the Applicant in document EP-A1-3 882 136.

[0006] 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.

[0007] In the distant field of aircraft turbomachinery, it is known to use a mechanical reducer to ensure power transmission between two rotating mechanical shafts.

[0008] There are many types of reducers, for example differential, planetary, epicyclic, intermediate line, series reduction stage, etc.

[0009] In the state of the art of turbofan engines, gearboxes are of the planetary or epicyclic type. Such a gearbox comprises a central pinion, called the sun gear, a ring gear, and gears called planet gears, which mesh between the sun gear and the ring gear. The planet gears are held by a frame called the planet carrier. The sun gear, ring gear, and planet carrier are planetary because their axes of revolution coincide with the longitudinal axis of the turbomachine. The planet gears each have a different axis of revolution, equally spaced on the same operating diameter around the axis of the planet gears. These axes are parallel to the longitudinal axis of the turbomachine.

[0010] There are several gearbox architectures. In other similar applications, there are so-called differential or "compound" architectures.

[0011] - On a planetary gearbox, the planet carrier is fixed and the ring gear constitutes the output shaft of the device which rotates in the opposite direction to the solar.

[0012] - On an epicyclic reducer, the ring gear is fixed and the planet carrier constitutes the output shaft of the device which rotates in the same direction as the solar panel.

[0013] - On a differential reducer, no element is fixed for rotation. The ring rotates in the opposite direction to the solar panel and the satellite carrier.

[0014] Reducers can be composed of one or more meshing stages. This meshing is achieved in different ways such as by contact, by friction or by magnetic fields.

[0015] In this application, the term "stage" or "toothing" means at least one series of meshing teeth with at least one series of complementary teeth. A toothing may be internal or external.

[0016] A satellite may comprise one or two gear stages. A single-stage satellite comprises teeth that may be straight, helical, or chevron-shaped, and whose teeth are located on the same diameter. These teeth cooperate with both the sun gear and the crown gear.

[0017] A two-stage satellite comprises two sets of teeth located on different diameters. A first set of teeth cooperates with the sun gear and a second set of teeth generally cooperates with the crown gear.

[0018] A double-stage gear reducer has the advantage of having a higher reduction ratio than a single-stage gear reducer of the same size.

[0019] In the context of a drive system for at least one landing gear wheel, the use of an electric motor and a gearbox to drive the wheel generates significant space constraints. The gearbox's outer diameter is limited by the wheel rim size, and its inner diameter is severely constrained by the wheel hub diameter. Furthermore, the use of an electric motor, which typically rotates at high speeds, necessitates a gearbox with a high reduction ratio to provide an output speed that matches the low rotational speed of the wheel. Epicyclic and planetary gear sets of current technology cannot achieve these levels of reduction within such a compact footprint.

[0020] The invention proposes a solution to at least some of these problems, which is simple, effective and economical. Summary of the invention

[0021] The invention relates to a drive device for at least one wheel of an aircraft landing gear, this device comprising:

[0022] - at least one landing gear wheel, this wheel comprising a rim having a axis of rotation,

[0023] - an electric motor comprising a shaft,

[0024] - a mechanical transmission system between the engine shaft and the rim, this mechanical transmission system including a mechanical reducer,

[0025] characterized in that the mechanical reducer comprises:

[0026] - two-stage meshing satellites which are distributed around the axis and which are carried by a mobile satellite carrier rotating around the axis, each of these satellites having a first set of teeth and a second set of teeth,

[0027] - a fixed solar element which is centered on the axis and which includes external teeth meshed with one of the first and second gears, this fixed solar element being configured to be fixed to at least one stator of the device,

[0028] - a movable solar element which is centered on the axis and which includes external teeth meshed with the other of the first and second gears, this solar element being driven in rotation around the axis by the motor shaft, and

[0029] - a movable crown which is centered on the axis and which has internal teeth meshed with one or the other of the first and second teeth, this crown being rotationally fixed to the rim around the axis.

[0030] The invention thus proposes a drive device for at least one wheel of an aircraft landing gear, which is equipped with a dual independent solar gear reducer. One of the solar gears is fixed and the other is rotatable. It is therefore understood that the rotatable solar gear forms an input (of torque) to the reducer, the output of the reducer being formed by the ring gear, which is also rotatable. The planet carrier is also rotatable. It can rotate freely and therefore be independent of any rotor of the electric motor.

[0031] The invention is compatible with a multi-stage gearbox as mentioned above. It is also compatible with a gearbox whose planet carrier is rotatable, such as epicyclic or differential gearboxes. It is also compatible with gears of any type (spur, helical, herringbone, etc.). Furthermore, the invention is compatible with a planet carrier of the monobloc type or of the cage and cage type. These different types of gearboxes are well known to those skilled in the art. The solution proposed below is compatible with any type of planetary bearing, whether composed of rolling elements, a hydrodynamic bearing, etc.

[0032] The device according to the invention may comprise one or more of the following features, taken individually or in combination with each other: • the teeth of the mobile solar element and the mobile crown are meshed with the same teeth of each of the satellites; • the satellites are of the double-stage type with symmetrical meshing, the first set of teeth being crossed by a median plane and being located between two series of teeth of the second set of teeth, the median plane being perpendicular to said axis and being a plane of symmetry of the first set of teeth and the series of teeth of the second set of teeth; • the teeth of the mobile solar element are meshed with the first set of teeth of each of the satellites; • the teeth of the fixed solar element are meshed with the sets of teeth of the second set of teeth of each of the satellites; • the fixed solar element comprises a first part having a series of teeth meshed with one of the series of teeth of the second set of teeth of each of the satellites, and a second part having a series of teeth meshed with the other of the series of teeth of the second set of teeth of each of the satellites; • the first part is connected to a stator of the electric motor, and the second part is connected to another stator of the device; • each of the first and second parts includes an annular fixing flange; • the teeth of the movable crown are meshed with the first teeth of each of the satellites; • the teeth of the movable crown are meshed with the sets of teeth of the second set of teeth of each of the satellites; • the first set of teeth comprises two series of teeth symmetrical with respect to the median plane. Brief description of the figures

[0033] Other features and advantages will become apparent from the following description of a non-limiting embodiment of the invention with reference to the accompanying drawings in which:

[0034] [Fig-1] [Fig.1] is a schematic perspective view of a train wheel aircraft landing gear and a drive device for this wheel,

[0035] [Fig.2] [Fig.2] is a partial axial cross-sectional view of a mechanical reducer,

[0036] [Fig. 3] [Fig. 3] is another partial axial cross-sectional view of a reducer mechanical,

[0037] [Fig.4] [Fig.4] is a schematic axial cross-sectional and perspective view of a double-stage reducer with symmetrical gearing,

[0038] [Fig. 5] [Fig. 5] is another schematic axial cross-sectional view of the reducer of the [Fig.4];

[0039] [Fig.6] [Fig.6] is a very schematic axial cross-sectional view of a device training according to an embodiment of the invention,

[0040] [Fig.7] [Fig.7] is a schematic perspective and axial section view of a device according to the embodiment of [Fig.6];

[0041] [Fig.8] [Fig.8] is a view similar to that of [Fig.6] and illustrates a variant of implementation of the device;

[0042] [Fig.9] [Fig.9] is a view similar to that of [Fig.6] and illustrates another alternative implementation of the device;

[0043] [Fig. 10] [Fig. 10] is a view similar to that of [Fig. 6] and illustrates another alternative implementation of the device. Detailed description of the invention

[0044] Fig. 1 shows a drive device 10 for at least one wheel 12 of an aircraft landing gear 14.

[0045] The wheel 12 has a rim 16 which has an axis of rotation X. In a conventional manner, this rim 16 has a general tubular or disc shape and carries a tire 18 on its periphery.

[0046] The device 10 includes an electric motor 20 and a mechanical transmission system 22 between a shaft of the motor 20 and the rim 16 of the wheel 12.

[0047] In the example shown, the motor 20 and the system 22 each have a generally annular shape and are centered on the X-axis. They are arranged side by side, and the system 22 is installed between the motor 20 and the rim 16. Part of the system 22, or even part of the motor 20, could be housed in the rim 16 to optimize the size of the device 10. The motor 20 and the system 22 can be protected by an external cylindrical cover 26 projecting from one side of the rim 16 or the tire 18.

[0048] The mechanical transmission system 22 includes a mechanical reducer 28, examples of which are illustrated in figures 2 to 5.

[0049] Figure 2 shows an epicyclic gearbox 28. At the input, the gearbox 28 is connected to a shaft 30, for example via internal splines 32b. Thus, the shaft 30 drives a planetary gear called the sun gear 32. Conventionally, the sun gear 32 drives a series of gears called planet gears 34, which are equally spaced around the same diameter around the X-axis of rotation of the sun gear 32. This diameter is equal to twice of the operating center distance between the solar 32 and the satellites 34. The number of satellites 34 is generally defined between three and seven.

[0050] The set of satellites 34 is held by a frame called satellite carrier s 36. Each satellite 34 rotates around its own Y axis, and meshes with a ring 38.

[0051] The output we have: • In this epicyclic configuration, the set of satellites 34 drives the satellite carrier 36 in rotation around the X axis. The ring 38 is fixed to a stator via a ring carrier 40 and the satellite carrier 36 is fixed to another shaft 42. • In another planetary configuration, the set of satellites 34 is held by a satellite carrier 36 which is fixed to a stator. Each satellite drives the ring gear 38 which is connected to the shaft 42 via a ring gear carrier 40. • In another differential configuration, the set of satellites 34 is held by a satellite carrier 36 which is connected to the shaft 30. Each satellite 34 drives the ring 38 which is brought to the shaft 42 via a ring carrier 40.

[0052] Each satellite 34 is mounted to rotate freely by means of a bearing 44, for example, a roller bearing or hydrodynamic bearing. Each bearing 44 is mounted on one of the axes 36b of the satellite carrier 36, and all the axes 36b are positioned relative to each other by means of one or more structural frames 36a of the satellite carrier 36. There is a number of axes 36b and bearings 44 equal to the number of satellites 34. For reasons of operation, assembly, manufacturing, inspection, repair, or replacement, the axes 36b and the frame 36a may be separated into several parts.

[0053] For the same reasons mentioned above, the teeth 34a of a satellite 34 can be separated into several helices or teeth, each having a median plane P, P'. In the example shown, each satellite 34 comprises two sets of chevron teeth cooperating with a ring 38 separated into two half-rings: • An upstream ring 38a consisting of a rim 38aa and a half-flange for fixing 38ab. On the rim 38aa is the front helix meshed with a helix of the teeth 34a of each satellite 34. The helix of the teeth 34a also meshes with that of the solar 32. • A downstream ring 38b consisting of a rim 38ba and a half-flange for fixing 38bb. On the rim 38ba is the rear helix meshed with a helix of the teeth 34a of each satellite 34. The helix of the teeth 34a also meshes with that of the solar 32.

[0054] If the helix widths vary between the solar 32, the satellites 34 and the crown 38 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.

[0055] Fig. 2 thus illustrates the case of a single-stage gear reducer, that is to say, the same toothing 34a of each satellite 34 cooperates with both the solar 32 and the ring 38. Even though the toothing 34a comprises two sets of teeth, these teeth have the same average diameter and form a single toothing called a chevron.

[0056] The mounting half-flange 38ab of the upstream ring 38a and the mounting half-flange 38bb of the downstream ring 38b form the mounting flange 38c of the crown. The crown 38 is fixed to the crown carrier 40 by assembling the mounting flange 38c of the crown 38 and a mounting flange 40a of the crown carrier 40 using a bolted assembly, for example.

[0057] Fig. 3 shows another example of a reducer architecture, called a double-stage geared reducer, in which each satellite 34 comprises two separate gears 34al, 34a2 configured to cooperate respectively with the crown 38 and the sun 32.

[0058] In this [Fig.3], the elements already described above are designated by the same references.

[0059] The meshing teeth 34al with the ring gear 38 have an average diameter denoted D2 and are located in a median plane P. The meshing teeth 34a2 with the sun gear 32 have an average diameter denoted DI and are located in another median plane P'. The median planes P and P' are parallel to each other and perpendicular to the X-axis. The diameter D2 is smaller than the diameter DI. Finally, each meshing tooth 34al, 34a2 comprises a single helix.

[0060] Figures 4 and 5 show a symmetrical double-toothed reducer 28, which comprises:

[0061] - a solar 32 having an axis of rotation X,

[0062] - a crown 38 which extends around the solar element 32 and which is configured to be stationary, rotating around the X-axis, and

[0063] - satellites 34 which are meshed with the solar 32 and the corona 38 and which are held by a satellite carrier 36 which is configured to be mobile in rotation around the X axis.

[0064] We define the plane H as a median plane perpendicular to the axis X and passing substantially through the middle of the reducer 28 ([Fig.5]).

[0065] The solar element 32 comprises internal splines 32b for coupling with the shaft 30 and external teeth 32a for meshing with the satellites 34. The teeth 32a have two sets of adjacent chevron teeth, separated from each other by an annular groove 46 oriented radially outwards. The teeth 32a are symmetrical with respect to plane H, its teeth being located on either side of plane H which passes through groove 46.

[0066] The crown 38 is formed by two independent rings 38a, 38b and includes a toothing which is separated into two series of chevron teeth 38dl, 38d2 carried respectively by the two rings.

[0067] The rings 38a, 38b are arranged symmetrically with respect to the plane H, which therefore extends between these rings. The rings 38a, 38b are connected and fixed to a ring carrier 40 by means of connecting annular flanges 48. The flanges 48 are independent of each other, each flange having a general S-shaped axial cross-section providing it with a certain radial flexibility through elastic deformation during operation.

[0068] Each ring 38a, 38b extends around the X axis and is fixed to the corresponding flange 48 by its outer periphery. Its inner periphery includes one of the teeth 38d1, 38d2.

[0069] The crown carrier 40 has a generally annular shape around the X-axis and, more specifically, a biconical shape. It thus comprises a first upstream or left-hand section 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 right-hand 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 40.

[0070] The upstream end of the crown carrier 40 extends around the planet carrier 36 or a shaft 42 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 50. In the same way, the downstream end of the crown carrier 40 extends around the planet carrier 36 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 52.

[0071] As is the case with the crown 38, the crown carrier 40 has a symmetry with respect to the plane H which cuts the crown carrier 40 in its middle and therefore passes through the ends of the largest diameter of the aforementioned sections.

[0072] Each satellite 34 has a first tooth 34a of average diameter DI for meshing with the solar 32, and a second tooth 54aa of average diameter D2, different from DI and in particular less than Dl, for meshing with the ring 38. The average diameters are measured from the Y axis of each satellite 34 and represent the average between the maximum diameter and the minimum diameter of a tooth of this satellite.

[0073] Each satellite 34 comprises a cylindrical sleeve 58 and an annular sail 60 extending substantially radially outwards from the middle of this sleeve 58. The toothing 54aa is separated into two series of chevron teeth 54al, 54a2 which are located respectively on the axial ends of the sleeve 58. The toothing 34a comprises two series of chevron teeth 34al, 34a2 which are located on the outer periphery of the web 60 and which are separated from each other by an annular groove 55 opening radially outwards with respect to the Y axis.

[0074] The tooth 34a is crossed in its middle by the plane H which passes through the groove 55, the teeth 34al, 34a2 being therefore arranged on either side of the plane H. The teeth 54al, 54a2 are also arranged symmetrically with respect to the plane H.

[0075] The teeth 34a and the outer periphery of the veil 60 have an axial dimension which is less than the axial distance between the rings 38a, 38b, as well as between the flanges 48, so that each satellite 34 can freely rotate in the crown carrier 40 and between the rings 38a, 38b and the flanges 48.

[0076] Each of the satellites 34 is guided in rotation by a hydrodynamic bearing 44 which includes a cylindrical body 44a which passes through the satellite 34, and in particular its sleeve 58, and which is configured to form a guiding oil film inside the satellite.

[0077] The body 44a of a bearing 44 extends along the Y axis and includes at its longitudinal ends extensions 44b housed in orifices forming seats for the planet carrier 36.

[0078] The body 44a is generally tubular and includes an internal oil circulation bore which generally communicates with oil supply channels 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 34.

[0079] The present invention proposes, in a reduced size, to increase the reduction ratio of a mechanical reducer within the framework of a device 10 for driving at least one wheel of an aircraft landing gear, as illustrated in [Fig.1].

[0080] The reducer 28 of the device 10 according to the invention comprises all the features described above in relation to figures 3, 4 and 5 insofar as they are not contrary or do not contradict what follows.

[0081] The references used in Figures 6 and following and already used in Figures 3, 4 and 5 therefore designate identical or similar elements.

[0082] Figures 6 to 10 illustrate embodiments of a reducer 28 according to the invention, which comprises:

[0083] - 34 double-stage meshing satellites which are distributed around the X-axis and which are carried by a rotating satellite carrier 36 around the X-axis, each of these satellites 34 having a first set of teeth 34a and a second set of teeth 54a,

[0084] - a fixed solar 32 which is centered on the X-axis and which includes an external toothing 32a meshed with one of the first and second teeth 34a, 54a, this solar element 32 being configured to be fixed to at least one stator of the device 10,

[0085] - a movable solar 56 which is centered on the X axis and which includes external teeth 56a meshed with the other of the first and second gears 34a, 54a, this solar 56 being mobile in rotation around the X axis, and

[0086] - a movable crown 38 which is centered on the X axis and which has teeth internal 38d meshed with one or the other of the first and second teeth 34a, 54a, this crown 38 being mobile in rotation around the X axis.

[0087] In the context of the present invention, the solar 56 is coupled with the shaft 30 of the electric motor 20. The crown 38 is coupled to the shaft 42 of the rim or to the rim 16 directly.

[0088] In the example shown, each of the satellites 34 is meshed with the solar elements 32, 56 and the ring gear 38 and comprises a first external toothing 34a with a mean diameter Dl, and a second external toothing 54a with a mean diameter D2, different from Dl. In the example shown, Dl is greater than D2. Alternatively, the toothing 34a and 54a could have equal diameters Dl and D2 and different numbers of teeth, so as to have different modules.

[0089] Reference 44a designates the cylindrical body of the hydrodynamic guidance bearing of each satellite 34, as mentioned above.

[0090] The satellite carrier 36 can be supported by any bearing with the solar 56 or the crown 38. It can also be completely free without support and simply balanced by the satellites 34.

[0091] In the embodiment shown in Figures 6 and 7, the toothed gear 34a of diameter Dl of each satellite 34 meshes with the toothed gear 56a of the sun gear 56 and the toothed gear 38d of the movable ring 38. The toothed gears 56a, 34a, and 38d are thus in the same plane PI perpendicular to the X-axis.

[0092] The toothing 54a of diameter D2 of each satellite 34 is meshed with the solar 32.

[0093] In the example shown, the satellites 34 are of the two-stage type symmetrical meshing, as in figures 4 and 5, that is to say that the first tooth 34a is crossed by a median plane H and is located between two series of teeth 54a1, 54a2 of the second tooth 54a. The median plane H is perpendicular to the X axis and is a plane of symmetry of the first tooth 34a and the series of teeth 54a1, 54a2 of the second tooth 54a.

[0094] The first dentition 34a may further comprise two sets of teeth symmetrical with respect to the median plane H, as described previously with reference to Figures 4 and 5.

[0095] In the example shown, the fixed solar 32 comprises a first part 58 having a series of teeth 32al meshed with one of the series of teeth 54a2 of the second toothing 54 of each of the satellites 34, and a second part 60 having a series of teeth 32a2 meshed with the other of the series of teeth 54al of the second toothing 54a of each of the satellites 34.

[0096] The first part 58 can be connected to a stator of the electric motor 20.

[0097] The second part 60 can be connected to another stator of the device 10.

[0098] Each of the first and second parts 58, 60 may include an annular fixing flange 58a, 60a visible in [Fig.7].

[0099] In the embodiment of [Fig.8], the satellites 34 are of the double-stage meshing type but not symmetrical, as in [Fig.3].

[0100] The toothing 34a of diameter DI of each satellite 34 is meshed with the toothing 38d of the crown 38.

[0101] The toothing 54a of diameter D2 of each satellite 34 is meshed with the toothing 32a of the fixed solar 32.

[0102] The toothing 34a of diameter DI of each satellite 34 is meshed with the toothing 56a of the movable solar 56.

[0103] The teeth 34a, 56a and 38d are therefore located in the same plane PI perpendicular to the X axis.

[0104] The solar element 32 can be connected to a stator of the electric motor 20.

[0105] The variant embodiment of [Fig.9] differs from the embodiment of Figures 6 and 7 essentially in that the teeth 38d of the crown 38 comprise two sets of teeth 38dl, 38d2 which are respectively meshed with the sets of teeth 54a2, 54a1 of the solar 32, and in particular with the two parts 60, 58 of this solar 32.

[0106] The tooth series 54al of each of the satellites 34, as well as the tooth series 32a2 and 38dl, are located in a plane PI perpendicular to the X axis.

[0107] The tooth series 54a2 of each of the satellites 34, as well as the tooth series 32al and 38d2, are located in a plane P2 perpendicular to the X axis.

[0108] The toothing 34a of diameter DI of each satellite 34 is meshed with the toothing 56a of the solar 56, and these toothings 34a, 56a are located in the median plane of symmetry H.

[0109] The variant embodiment of [Fig. 10] differs from the embodiment of [Fig. 8] essentially in that the teeth 38d of the crown 38 are meshed with the teeth 54a of diameter D2 of each satellite 34. The teeth 32a of the fixed solar element 32 are also meshed with the teeth 54a of each satellite 34. These teeth 38d and 32a are located in a plane PI perpendicular to the X axis.

[0110] The toothing 34a of diameter DI of each satellite 34 is meshed with the toothing 56a of the movable solar 56.

[0111] This invention makes it possible to obtain a significant reduction ratio in a limited space compared to other more conventional architectures (epicyclic or planetary train).

[0112] Furthermore, symmetrizing the satellites eliminates the tilting moments in the gearbox. This therefore allows us to: - reduce the forces that need to be absorbed by the satellite bearings (compared to a non-symmetrical architecture), - reduce the size of the satellite tiers (compared to a non-symmetrical architecture), - increase efficiency (compared to a non-symmetrical architecture), - reduce the size (compared to an epicyclic or planetary gear train), and - reduce the mass (compared to an epicyclic or planetary gear train).

Claims

Demands

1. A device (10) for driving at least one wheel (12) of an aircraft landing gear (14), said device (10) comprising: - at least one landing gear wheel (12), this wheel (12) having a rim (16) having an axis of rotation (X), - an electric motor (20) having a shaft (30), - a mechanical transmission system (22) between the shaft of the motor (20) and the rim (16), this mechanical transmission system (22) comprising a mechanical reducer (28), characterized in that the mechanical reducer (28) comprises: - two-stage meshing planetary gears (34) which are distributed around the axis (X) and which are carried by a planetary carrier (36) movable in rotation about the axis (X), each of these planetary gears (34) having a first set of teeth (34a) and a second set of teeth (54a), - a fixed solar element (32) which is centered on the axis (X) and which includes an external toothing (32a) meshed with one of the first and second toothings (34a, 54a),- a fixed solar element (32) configured to be fixed to at least one stator of the device (10), - a movable solar element (56) which is centered on the axis (X) and which includes an external toothing (56a) meshed with the other of the first and second toothings (54a, 34a), this solar element (56) being driven in rotation about the axis (X) by the shaft (30) of the motor (20), and - a movable ring gear (38) which is centered on the axis (X) and which includes an internal toothing (38d) meshed with one or the other of the first and second toothings (34a, 54a), this ring gear (38) being rotationally fixed to the rim (16) about the axis (X).

2. Device (10) according to claim 1, wherein the teeth (56a, 38d) of the movable solar (56) and of the movable ring (38) are meshed with the same teeth (34a) of each of the satellites (34).

3. Device (10) according to any one of the preceding claims, wherein the satellites (34) are of the double-stage type with symmetrical meshing, the first toothing (34a) being crossed by a median plane (H) and being located between two sets of teeth (54al, 54a2) of the second toothing (54a), the median plane (H) being perpendicular to said axis (X) and being a plane of symmetry of the first toothing (34a) and of the sets of teeth (54al, 54a2) of the second toothing (54).

4. Device (10) according to claim 3, wherein the teeth (56a) of the mobile solar (56) are meshed with the first teeth (34a) of each of the satellites (34).

5. Device (10) according to claim 3 or 4, wherein the teeth (32a) of the fixed solar (32) are meshed with the sets of teeth (54al, 54a2) of the second teeth (54a) of each of the satellites (34).

6. Device (10) according to claim 5, in which the fixed solar (32) comprises a first part (58) having a series of teeth (32al) meshed with one of the series of teeth (54a2) of the second toothing (54a) of each of the satellites (34), and a second part (60) having a series of teeth (32a2) meshed with the other of the series of teeth (54al) of the second toothing (54a) of each of the satellites (34).

7. Device (10) according to claim 6, wherein the first part (58) is connected to a stator of the electric motor (20), and the second part (60) is connected to another stator of the device (10).

8. Device (10) according to claim 6 or 7, wherein each of the first and second parts (58, 60) comprises an annular fixing flange (58a, 60a).

9. Device (10) according to any one of claims 3 to 7, wherein the teeth (38d) of the movable ring (38) are meshed with the first teeth (34a) of each of the satellites (34).

10. Device (10) according to any one of claims 3 to 7, wherein the teeth (38d) of the movable crown (38) are meshed with the sets of teeth (54al, 54a2) of the second teeth (54) of each of the satellites (34).

11. Device (10) according to any one of claims 3 to 10, wherein the first toothing (34a) comprises two sets of teeth symmetrical with respect to the median plane (H).

Images