REDUCER GEAR FOR AN AIRCRAFT

Abstract

A reduction gear (10), particularly for an aircraft, this reduction gear (10) comprising: - a rotating sun gear (26) about a first axis (A), - a ring gear (28) mounted about the axis (A) and the sun gear (26), - satellites (30) interposed between the sun gear (26) and the ring gear (28) and meshed with the sun gear (26) and the ring gear (28), - a satellite carrier (32) carrying mounting fingers (62) for the satellites (30), these fingers extending along second axes (B) parallel to the first axis (A), - bearings (60) for guiding the satellites (30) on the fingers, these bearings (60) being traversed by the fingers (62) and interposed between the satellites (30) and the fingers (62), characterized in that it further comprises axial retaining elements for the satellites (30) on the fingers (62), these elements comprising pairs (80, 82) of magnets (80a, 80b, 82a, 82b). Figure for the abbreviation: Figure 4

Description

Title of the invention: REDUCER FOR AN AIRCRAFT Technical field of the invention

[0001] The present invention relates to a reduction gear, in particular for an aircraft, as well as to an aircraft comprising such a reduction gear. The aircraft is, for example, of the VTOL type (which is the acronym for the Anglo-Saxon expression Vertical Take-Off and Landing), that is to say, an aircraft with vertical take-off and landing. Technical Downstream Plan

[0002] The state of the art includes in particular documents FR-A1-2 987 416, FR-Al-2 853 382, ​​FR-A1-3 041 054, FR-A1-3 073 915, FR-A1-3 084 428.

[0003] The role of a mechanical reducer is to modify the speed ratio and torque between the input shaft and the output shaft of a mechanism.

[0004] New generations of turbofan engines, particularly those with a high bypass ratio, include a mechanical gearbox to drive the shaft of a fan. Typically, the purpose of the gearbox is to transform the high rotational speed of the power turbine shaft into a slower rotational speed for the fan-driving shaft.

[0005] Such a reduction gear comprises a central pinion, called the sun gear, a ring gear, and pinions called planet gears, which mesh between the sun gear and the ring gear. The planet gears are held by a frame called a planet carrier. The sun gear, ring gear, and planet carrier are planetary gears 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.

[0006] Several gearbox architectures exist. In the state of the art of turbofan engines, gearboxes are of the planetary or epicyclic type. In other similar applications, there are so-called differential or "compound" architectures.

[0007] - on a planetary reducer, the planet carrier is fixed and the ring constitutes the output shaft of the device which rotates in the opposite direction to the solar.

[0008] - 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.

[0009] - 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.

[0010] Gear reducers can be composed of one or more meshing stages. This meshing is achieved in various ways, such as by contact, friction, or magnetic field. There are several types of contact meshing, such as with straight or herringbone teeth.

[0011] In practice, the planetary gears of a gearbox are guided in rotation by bearings through which physical fingers or shafts pass, these fingers being carried by the planetary carrier. The planetary gears are therefore mounted on the bearings which are themselves mounted on the fingers, the fingers being aligned on the aforementioned axes of revolution.

[0012] Guide bearings can be of different types and, for example, plain or rolling. In the case of rolling bearings, the bearings can include balls, rollers, or needles, for example.

[0013] In certain configurations, it is necessary to provide axial stops at the axial ends of the satellites to prevent them from contacting the satellite carrier. This is particularly the case in a VTOL aircraft where the gearbox can be positioned so that its longitudinal axis is vertical. In this position, the satellites tend to slide on the bearings or fingers and move downwards due to gravity. To prevent the satellites from rubbing against the satellite carrier, an axial stop is mounted between each axial end of the satellite and the carrier. This axial stop can be implemented using a bearing. This issue also arises in a horizontal configuration where the satellites are free to move axially.

[0014] The disadvantage of this solution is the need for lubrication of the stop necessary for its proper functioning.

[0015] The present invention proposes a solution to this problem, which is simple, effective and economical. Summary of the invention

[0016] The invention relates to a gearbox, in particular for an aircraft, this gearbox comprising:

[0017] - a mobile solar element rotating around a first axis,

[0018] - a crown mounted around the axis and the solar element,

[0019] - satellites intercalated between the solar system and the corona and meshed with the solar system and the crown,

[0020] - a satellite carrier on which satellite mounting fingers are mounted, these fingers extending along secondary axes parallel to the first axis,

[0021] - satellite guidance bearings on the fingers, these bearings being traversed by the fingers and interspersed between the satellites and the fingers,

[0022] characterized in that it further comprises axial retention elements for the satellites on the fingers, these elements comprising:

[0023] - a first pair of magnets mounted at a first axial end of each satellite, the first pair of magnets having initial repulsive faces mounted opposite each other, these first repulsive faces having the same magnetic pole so that the magnets repel each other, and

[0024] - a second pair of magnets mounted at a second axial end of each satellite opposite the first axial end of each satellite, and the second pair of magnets having two second repulsive faces mounted opposite each other, these second repulsive faces having the same magnetic pole so that the magnets repel each other.

[0025] The invention differs from the prior art, in particular, in that it does not provide an axial stop for axially locking the satellites onto the mounting fingers. An axial stop means that the axial locking of the satellites is achieved by means of a stop, i.e., by physical contact. On the contrary, in the invention, the satellites are held axially without contact, by means of magnetic retaining elements. This is made possible by the use of magnets, and in particular pairs of magnets. Each pair of magnets comprises two magnets arranged so that their facing faces have the same pole. For example, the two magnets in each pair have their North poles facing each other or their South poles facing each other. The magnets in each pair thus function to repel each other and prevent any contact between them, and therefore between the satellite and the satellite holder.

[0026] The present invention is compatible with: - of a single-stage or multi-stage reducer; - of straight, helical or chevron teeth; - of any type of reducer: planetary, epicycloidal, differential; - of any type of one-piece satellite carrier or of the cage and cage carrier type; - of all types of satellite guidance bearings, such as rolling element bearings or hydrodynamic.

[0027] The reducer according to the invention may comprise one or more of the following features, taken individually or in combination with each other; these features having, in particular, the advantage of making the geared motor more compact: • the magnets in each pair of magnets each have a general ring shape and are mounted around the fingers; • Each pair of magnets is axially interposed between the satellite carrier and an axial end of a finger that is opposite the satellite carrier

[0028] — each pair of magnets is axially intercalated between the axial end of the satellite and satellite carrier, and in particular between the axial end of the satellite and a radial wall of the satellite carrier s;

[0029] - each pair of magnets is further axially intercalated between an axial end of a satellite bearing and the satellite carrier or between an axial end of a satellite bearing and an axial end of a finger;

[0030] — each pair of magnets is further axially intercalated between an end axial of the satellite bearings and the satellite carrier; • the magnets in each pair of magnets are each of identical dimensions; • the magnets in the pairs of magnets each have identical dimensions; • the magnets in each pair of magnets have an outer diameter greater than one minimum internal diameter of each satellite, and less than a maximum external diameter of each satellite; • in each of the magnets is in the form of a washer; • each of the magnets is a permanent magnet or an electromagnet; • the reducer is a geared motor and also includes an electric motor;

[0031] — the magnets are made of Neodymium or Samarium-Cobalt;

[0032] — the air gap between the magnets of each pair is between 1 and 2 mm; this The range of values ​​may depend in particular on the mass of the satellites.

[0033] The invention also relates to a geared motor comprising a reducer as described above and an electric motor in which the electric motor drives or is driven by the reducer and preferably extends around the planet carrier.

[0034] The invention further relates to an aircraft comprising an aircraft, for example of the VTOL type, comprising a reducer or geared motor as described above, in particular for driving a propulsion propeller. Brief description of the figures

[0035] 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:

[0036] [Fig-1] [Fig.1] is a schematic perspective and axial section view of a reducer;

[0037] [Fig.2] [Fig.2] is a schematic axial cross-sectional view of the reducer of [Fig.1];

[0038] [Fig.3] [Fig.3] is a schematic axial cross-sectional view of a gearbox satellite, and in particular its guide bearing and axial stops;

[0039] [Fig. 4] [Fig. 4] is a schematic axial cross-sectional view of a gearbox satellite, and in particular of its guide bearing and axial retaining elements; and

[0040] [Fig.5] [Fig.5] is a larger scale view of part of [Fig.4] and shows a pair of magnets of a retaining element. Detailed description of the invention

[0041] Fig. 1 illustrates an embodiment of a reducer 10 according to the invention, this reducer being particularly suitable for use in an aircraft.

[0042] The aircraft is, for example, of the VTOL type, i.e., vertical takeoff and landing. The reduction gear 10 can, for example, be used to drive the propulsion propeller or one of the propulsion propellers of the aircraft.

[0043] In the example shown, the reducer 10 is a geared motor 10, so the expressions reducer and geared motor will be used to refer to the same thing in what follows.

[0044] The gearbox or geared motor 10 comprises an electric motor 12 and a mechanical gearbox 14. Reference numeral 12 refers more specifically to the active parts of the electric motor, the motor's power electronics not being shown here. In the remainder of this description, the electric motor 12 will refer more specifically to the active parts of the motor.

[0045] The electric motor 12 has an annular shape and is aligned on a first axis A, which is a common axis with the mechanical reducer 14.

[0046] The electric motor 12 comprises a rotor 16 and a stator 18. In the example shown, the rotor 16 is located inside the stator 18.

[0047] The rotor 16 includes an annular row of permanent magnets 20. These magnets 20 can be separated from each other by spacers 22. The number of magnets 20 can be greater than 20 or 30 for example.

[0048] The stator 18 may include an annular row of windings (not shown) which are formed by winding around cores 24. The number of cores 24 is, for example, equal to the number of permanent magnets 20.

[0049] In the example shown, which is not limiting, the mechanical reducer 14 is of the planetary type, that is to say, it includes a movable ring and a fixed planet carrier.

[0050] The mechanical reducer 14 includes a solar 26 movable in rotation around the axis A, a ring 28 movable in rotation around this axis A, and satellites 30 intercalated between the solar 26 and the ring 28 and meshed with the solar 26 and the ring 28.

[0051] The satellites 30 are carried by a satellite carrier 32 which is here fixed.

[0052] In the example shown, the solar element 26 has a general L or C shape in axial section and comprises:

[0053] - an internal cylindrical wall 26a which includes or carries external teeth 33,

[0054] - a radial annular wall 26b extending from the internal cylindrical wall 26a outwards,

[0055] - and possibly an external cylindrical wall 26c which extends around the wall internal cylindrical 26a and which is connected to the external periphery of the radial wall 26b.

[0056] As can be seen in the example shown, the rotor 16 is directly fixed to the outer periphery of the radial wall 26b or to the outer cylindrical wall 26c, or the stator 18 is directly supported by the outer periphery of the radial wall 26b or by the outer cylindrical wall 26c.

[0057] It can be seen in the drawings that the rotor 16 can extend around the teeth 33 of the solar 26.

[0058] The solar 26 and in particular its outer wall 26c can have a length L1 or dimension along the axis A which is greater than or equal to a length L2 or dimension along the axis A of the toothing 33 of the solar 26.

[0059] Advantageously, the geared motor 10 includes a first bearing 34 for guiding the solar 26, which is mounted between the solar 26 and the satellite carrier s 32, and a second bearing 36 for guiding the solar 26, which is mounted between the solar 26 and the ring 28.

[0060] The first bearing 34 preferably has a diameter DI greater than that D2 of the teeth 33 of the solar 26, and the second bearing 36 has a diameter D3 less than that D2 of the teeth 33 of the solar 26.

[0061] In the example shown, the first bearing 34 is supported by the radial wall 26b, and the second bearing 36 is located inside the internal cylindrical wall 26c.

[0062] In the example also shown, the crown 28 has, in axial section, a general L or C shape and comprises:

[0063] - an external cylindrical wall 28a which includes or carries internal teeth 38,

[0064] - a radial annular wall 28b extending from the external cylindrical wall 28a inward,

[0065] - and possibly an internal cylindrical wall 28c which extends inside the external cylindrical wall 28a and which is connected to the internal periphery of the radial wall 28b.

[0066] The rotor 16 can extend at least partially around the internal teeth 38 of the crown 28.

[0067] The geared motor 10 further includes an output shaft 50 in the example shown, which is coupled by splines 40 to the inner periphery of the radial wall 28b or to the inner cylindrical wall 28c.

[0068] As in the example shown, the satellite carrier 32 is fixed to a housing 42 of the geared motor 10.

[0069] The stator 18 of the motor 12 can be fixed directly to the housing 42 or carried directly by the housing 42.

[0070] The housing 42 may have a general L or C shape in axial section and comprise:

[0071] - an external cylindrical wall 42a,

[0072] - a radial annular wall 42b extending from the outer cylindrical wall towards the interior,

[0073] - and possibly an internal cylindrical wall 42c which extends inside the external cylindrical wall 42a and which is connected to the internal periphery of the radial wall 42b.

[0074] The geared motor 10 may include a bearing 44 for guiding the output shaft 50, this bearing 44 being mounted between the output shaft 50 and the inner periphery of the radial wall 42b or the inner cylindrical wall 42c of the housing 42.

[0075] The satellite carrier 32 can be fixed to the radial wall 42b of the housing 42, as in the example shown.

[0076] Conventionally, each of the satellites 30 is guided by a bearing 60 which is traversed by a finger 62 carried by the satellite carrier 32. The satellites 30 are therefore mounted on guide bearings 60 which are themselves mounted on fingers 62. The bearings 60 are for example rolling bearings and in particular roller, ball or needle bearings but could alternatively be plain bearings.

[0077] The satellites 30 are thus guided in rotation around second axes B, which are parallel to the axis A and generally regularly distributed around the axis A.

[0078] Fig. 3 is a larger scale view of a satellite 30, its guide bearing 60, here with needle bearings, and its mounting finger 62 on the satellite carrier 32.

[0079] To prevent the satellite 30 from coming into contact with the satellite carrier 32 and rubbing against it, it would be possible to provide axial stops 70 between the satellites 30 and the satellite carrier 32. In practice, these axial stops 70 would be in the form of bearing stops, and for example ball stops as in the example shown.

[0080] However, these thrust bearings 70 would need to be continuously lubricated during operation of the reducer 10 to ensure their proper functioning. Furthermore, since each of the thrust bearings 70 comprises two bearing rings 70a, 70b between which balls 70c are mounted, this solution would also be disadvantageous in terms of axial dimensions and mass.

[0081] The present invention proposes a solution to this problem, one embodiment of which is illustrated in figures 4 and 5.

[0082] The invention proposes to provide axial retaining elements for the satellites 30 on the fingers 62, at the axial ends of each satellite 30.

[0083] The figures show the axial retention of a satellite 30 and it will be understood that the invention applies in the same way to all the satellites 30 of the reducer 10.

[0084] A first pair of magnets 80 is mounted at an axial end of the satellite 30. The magnets 80a, 80b of this first pair 80 have faces 80al, 80b facing the same magnetic pole so that the magnets 80a, 80b repel each other.

[0085] A second pair of magnets 82 is mounted at the opposite axial end of the satellite 30. The magnets 82a, 82b respectively have faces 82al, 82b facing the same magnetic pole so that the magnets 82a, 82b repel each other (arrow Fl in [Fig.4].)

[0086] As in the example shown, the magnets 80a, 80b, 82a, 82b of each pair of magnets each have a general annular shape and are mounted around the fingers 62. They can, for example, be in the form of washers, the lateral annular faces of which are preferably flat.

[0087] The magnets are preferably permanent magnets, for example made of Neodymium or Samarium-Cobalt.

[0088] The repulsive force generated by the magnets 80a, 80b, 82a, 82b of each pair 80a, 82 allows them to be separated from each other by an air gap J, J' which is for example between 1 and 2 mm. This range of values ​​may notably depend on the mass of the satellites.

[0089] This repulsive force depends, for example, on the mass of the satellites and the acceleration of the aircraft. For example, for a 2kg satellite undergoing a vertical acceleration of 5kg, the force of the magnet would be greater than 2 9.81 x 5 = 98.IN.

[0090] Preferably, each pair of magnets 80, 82 is axially interposed between the axial end of the satellite 30 and the satellite carrier 32, and in particular between the axial end of the satellite 30 and a radial wall 32a of the satellite carrier. This radial wall 32a may include a mounting hole 84 for an axial end of the finger 62, as in the example shown.

[0091] Each pair of magnets 80, 82 can also be axially intercalated between an axial end of the bearing 60 of the satellite 30 and the satellite carrier 32.

[0092] Magnets 80a, 80b preferably have identical dimensions.

[0093] Magnets 82a, 82b preferably have identical dimensions.

[0094] The magnets 80a, 80b, 82a, 82b may also have identical dimensions as in the example shown.

[0095] Advantageously, the magnets 80a, 80b, 82a, 82b have an external diameter H1 greater than a minimum internal diameter Hmin of each satellite 30 and less than a maximum external diameter Hmax of each satellite 30.

[0096] The present invention offers several advantages, including:

[0097] - the magnetic retaining elements do not require lubrication and the sup Lubrication pressure in this area simplifies lubrication and reduces the mass of the reducer;

[0098] - the retaining elements have no rotating parts in contact, they cannot therefore it does not wear out through friction, which increases its reliability;

[0099] - the retaining elements prevent friction between the satellites and the carrier satellites, which reduces overall gearbox losses and therefore improves its efficiency; etc.

Claims

Demands

1. A reduction gear (10) for an aircraft, said reduction gear (10) comprising: - a rotating sun gear (26) about a first axis (A), - a ring gear (28) mounted about the axis (A) and the sun gear (26), - satellites (30) interposed between the sun gear (26) and the ring gear (28) and meshed with the sun gear (26) and the ring gear (28), - a satellite carrier (32) on which mounting fingers (62) for the satellites (30) are mounted, these fingers extending along second axes (B) parallel to the first axis (A), - bearings (60) for guiding the satellites (30) on the fingers (62), these bearings (60) being traversed by the fingers (62) and interposed between the satellites (30) and the fingers (62), characterized in that it further comprises axial retention elements for the satellites (30) on the fingers (62), these elements comprising: - a first pair (80) of magnets (80a, 80b) mounted at a first axial end of each satellite (30), the first pair (80) of magnets (80a,80b) comprising first repulsive faces (80al, 80bl) mounted opposite each other, these first repulsive faces having the same magnetic pole so that the magnets (80a, 80b) repel each other, and - a second pair (82) of magnets (82a, 82b) mounted at a second axial end of each satellite (30) opposite the first axial end of each satellite (30), the second pair (82) of magnets (82a, 82b) comprising two second repulsive faces (82a1, 82b1) mounted opposite each other, these second repulsive faces having the same magnetic pole so that the magnets (82a, 82b) repel each other.

2. Reducer (10) according to claim 1, wherein the magnets (80a, 80b, 82a, 82b) of each pair of magnets (80, 82) each have a general annular shape, preferably have a washer shape, and are mounted around the fingers (62).

3. Reducer (10) according to claim 1 or 2, wherein each pair of magnets (80, 82) is axially intercalated between the planet carrier (32) and an axial end of a finger (62) which is opposite the planet carrier (32).

4. Reducer (10) according to claim 3, wherein each pair of magnets (80, 82) is further axially intercalated between an end axial of a satellite bearing (60) (30) and the satellite carrier (32) or between an axial end of a satellite bearing (60) (30) and an axial end of a finger (62).

5. Reducer (10) according to any one of the preceding claims, wherein the magnets (80a, 80b, 82a, 82b) of each pair of magnets (80, 82) each have identical dimensions.

6. Reducer (10) according to any one of the preceding claims, wherein the magnets (80a, 80b, 82a, 82b) of each pair of magnets (80, 82) have an external diameter (Hl) greater than a minimum internal diameter (Hmin) of each satellite (30), and less than a maximum external diameter (Hmax) of each satellite (30).

7. Reducer (10) according to any one of the preceding claims, wherein in each of the magnets (80a, 80b, 82a, 82b) is a permanent magnet or an electromagnet.

8. Geared motor comprising a reducer (10) according to any one of the preceding claims and an electric motor (12), wherein the electric motor (12) drives or is driven by the reducer (10) and preferably extends around the planet carrier (32).

9. Aircraft comprising a geared motor according to the preceding claim or a reducer (10) according to any one of claims 1 to 8 for driving a propulsion propeller.

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