Reduction gearset for an aircraft

Abstract

A reduction gearset (10), in particular for an aircraft, this reduction gearset (10) comprising: - a sun gear (26) rotatable about a first axis (A), - a ring gear (28) mounted about the axis (A) and the sun gear (26), - planet pinions (30) inserted between the sun gear (26) and the ring gear (28) and meshing with the sun gear (26) and the ring gear (28), - a planet carrier (32) which carries fingers (62) for mounting the planet pinions (30), these fingers extending along second axes (B) parallel to the first axis (A), - bearings (60) for guiding the planet pinions (30) on the fingers, these bearings (60) having the fingers (62) passing through them and being inserted between the planet pinions (30) and the fingers (62), characterized in that it further comprises axial-retention elements for axially retaining the planet pinions (30) on the fingers (62), these elements comprising pairs (80, 82) of magnets (80a, 80b, 82a, 82b).

Description

[0001] DESCRIPTION

[0002] TITLE: REDUCER FOR AN AIRCRAFT

[0003] Technical field of the invention

[0004] The present invention relates to a reducer, in particular for an aircraft, as well as to an aircraft comprising such a reducer. The aircraft is for example of the VTOL type (which is the acronym for the English expression Vertical Take-Off and Landing), that is to say an aircraft with vertical take-off and landing.

[0005] Technical approval plan

[0006] The state of the art includes in particular documents FR-A1 -2 987 416, FRAI -2 853 382, ​​FR-A1 -3 041 054, FR-A1 -3 073 915, FR-A1 -3 084 428, FRAI -3 084 428, US-A1 -2021 / 215234 and EP-B1 -3 707 408.

[0007] 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.

[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's purpose is to transform the so-called fast rotation speed of a power turbine shaft into a slower rotation speed for the shaft driving the fan.

[0009] 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 longitudinal axis of the turbomachine. 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 of the turbomachine. There are several reducer architectures. In the state of the art of double-flow turbomachines, the reducers are of the planetary or epicyclic type. In other similar applications, there are architectures called differential or "compound".

[0010] - 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.

[0011] - 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.

[0012] - on a differential reducer, no element is fixed in rotation. The crown rotates in the opposite direction to the sun and the planet carrier.

[0013] Gearboxes can be composed of one or more meshing stages. This meshing is ensured in different ways such as by contact, friction or even by magnetic field. There are several types of contact meshing such as with straight or herringbone teeth.

[0014] In practice, the satellites of a reducer are guided in rotation by bearings which are crossed by fingers or physical axes, these fingers being carried by the planet carrier. The satellites are therefore mounted on the bearings which are themselves mounted on the fingers, the fingers being aligned on the aforementioned axes of revolution.

[0015] Guide bearings can be of different types, for example, plain or rolling bearings. In rolling bearings, the bearings can include balls, rollers, or needles, for example.

[0016] In some configurations, it is necessary to provide axial stops at the axial ends of the satellites, to prevent the satellites from coming into contact with the planet carrier. This is particularly the case in a VTOL type aircraft in which the reduction gear 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 under the effect of gravity. To prevent the satellites from rubbing on the satellite carrier, an axial stop is mounted between each axial end of the satellite and the planet carrier. This axial stop can be achieved by a rolling thrust bearing. This problem is also true in a horizontal configuration where the satellites are free to move axially. The disadvantage of this solution is the need for lubrication of the stop necessary for its proper operation.

[0017] The present invention provides a solution to this problem, which is simple, effective and economical.

[0018] Summary of the invention

[0019] The invention relates to a reducer, in particular for an aircraft, this reducer comprising:

[0020] - a mobile solar system rotating around a first axis,

[0021] - a crown mounted around the axis and the sun,

[0022] - satellites interposed between the sun and the crown and meshed with the sun and the crown,

[0023] - a satellite carrier on which satellite mounting fingers are mounted, these fingers extending along second axes parallel to the first axis,

[0024] - bearings for guiding the satellites on the fingers, these bearings being crossed by the fingers and interposed between the satellites and the fingers, characterized in that it further comprises elements for axially retaining the satellites on the fingers, these elements comprising:

[0025] - a first pair of magnets mounted at a first axial end of each satellite, the first pair of magnets comprising first repulsion faces mounted opposite each other, these first repulsion faces having the same magnetic pole so that the magnets repel each other, and

[0026] - 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 comprising two second repulsion faces mounted opposite each other, these second repulsion faces having the same magnetic pole so that the magnets repel each other.

[0027] The invention differs from the prior art in particular by the fact that it does not propose an axial stop to axially lock the satellites on the mounting fingers. An axial stop means that the axial stopping of the satellites is achieved by a stop, that is to say by physical contact. On the contrary, in the invention, the satellites are retained axially without contact, by means of retaining elements of the magnetic type. This is made possible by the use of magnets and in particular pairs of magnets. Each pair of magnets comprises two magnets which are arranged so that their facing faces have the same pole. For example, the two magnets of each pair have their North pole facing each other or their South pole facing each other. The magnets of each pair thus have the function of repelling each other and avoiding any contact between them and therefore between the satellite and the planet carrier.

[0028] The present invention is compatible:

[0029] - a single-stage or multi-stage reducer;

[0030] - straight, helical or herringbone teeth;

[0031] - any type of reducer: planetary, epicyclic, differential;

[0032] - any type of single-piece or cage and cage-holder type planet carrier;

[0033] - any type of satellite guide bearings, such as rolling elements or hydrodynamic.

[0034] The reducer according to the invention may comprise one or more of the following characteristics, taken in isolation from one another, or in combination with one another; these characteristics having in particular the advantages of making the geared motor more compact:

[0035] - the magnets of each pair of magnets each have a generally annular shape and are mounted around the fingers; - each pair of magnets is interposed axially between the planet carrier and an axial end of a finger which is opposite the planet carrier

[0036] -- each pair of magnets is interposed axially between the axial end of the satellite and the planet carrier, and in particular between the axial end of the satellite and a radial wall of the planet carrier;

[0037] - each pair of magnets is further interposed axially between an axial end of a satellite bearing and the planet carrier or between an axial end of a satellite bearing and an axial end of a finger;

[0038] -- each pair of magnets is further interposed axially between an axial end of the satellite bearings and the planet carrier;

[0039] - the magnets in each pair of magnets each have identical dimensions;

[0040] - the magnets of the pairs of magnets each have identical dimensions;

[0041] - the magnets of each pair of magnets have an external diameter greater than a minimum internal diameter of each satellite, and less than a maximum external diameter of each satellite;

[0042] - in each of the magnets is in the form of a washer;

[0043] - each of the magnets is a permanent magnet or an electromagnet;

[0044] - the reducer is a geared motor and also includes an electric motor;

[0045] -- the magnets are made of Neodymium or Samarium-Cobalt;

[0046] -- the air gap between the magnets of each pair is between 1 and 2 mm; this range of values ​​may in particular depend on the mass of the satellites. 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.

[0047] The invention further relates to an aircraft comprising an aircraft, for example of the VTOL type, comprising a reduction gear or a geared motor as described above, in particular for driving a propulsion propeller. Brief description of the figures

[0048] 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:

[0049] [Fig. 1] Figure 1 is a schematic perspective and axial sectional view of a reducer;

[0050] [Fig.2] Figure 2 is a schematic axial sectional view of the reducer of Figure 1;

[0051] [Fig.3] Figure 3 is a schematic axial sectional view of a reducer satellite, and in particular of its guide bearing and its axial stops

[0052] I

[0053] [Fig.4] Figure 4 is a schematic axial sectional view of a reduction gear satellite, and in particular of its guide bearing and its axial retaining elements; and

[0054] [Fig.5] Figure 5 is an enlarged view of a portion of Figure 4 and shows a pair of magnets of a retainer.

[0055] Detailed description of the invention

[0056] Figure 1 illustrates an embodiment of a reducer 10 according to the invention, this reducer being particularly suitable for use in an aircraft.

[0057] 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.

[0058] In the example shown, the reducer 10 is a geared motor 10, so the expressions reducer and geared motor will be used to designate the same thing in the following.

[0059] The reducer or geared motor 10 comprises an electric motor 12 and a mechanical reducer 14. The reference 12 more particularly designates the active parts of the electric motor, the power electronics of the motor not being shown here. In the remainder of the description, the electric motor 12 will more specifically designate the active parts of the motor.

[0060] 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.

[0061] 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.

[0062] The rotor 16 comprises 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.

[0063] The stator 18 may comprise 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.

[0064] In the example shown, which is not limiting, the mechanical reducer 14 is of the planetary type, that is to say that it comprises a movable crown and a fixed planet carrier.

[0065] The mechanical reducer 14 comprises a sun gear 26 movable in rotation around the axis A, a crown 28 movable in rotation around this axis A, and satellites 30 interposed between the sun gear 26 and the crown 28 and meshed with the sun gear 26 and the crown 28.

[0066] The satellites 30 are carried by a satellite carrier 32 which is fixed here.

[0067] In the example shown, the solar 26 has a general L or C shape in axial section and comprises:

[0068] - an internal cylindrical wall 26a which comprises or carries an external toothing 33,

[0069] - a radial annular wall 26b which extends from the internal cylindrical wall 26a towards the outside,

[0070] - and possibly an external cylindrical wall 26c which extends around the internal cylindrical wall 26a and which is connected to the external periphery of the radial wall 26b. As seen in the example shown, the rotor 16 is directly fixed to the external periphery of the radial wall 26b or to the external cylindrical wall 26c, or the stator 18 is directly carried by the external periphery of the radial wall 26b or by the external cylindrical wall 26c.

[0071] It can be seen in the drawings that the rotor 16 can extend around the teeth 33 of the sun 26.

[0072] The sun 26 and in particular its external wall 26c may 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 teeth 33 of the sun 26.

[0073] Advantageously, the geared motor 10 comprises a first bearing 34 for guiding the sun gear 26, which is mounted between the sun gear 26 and the planet carrier 32, and a second bearing 36 for guiding the sun gear 26, which is mounted between the sun gear 26 and the ring gear 28.

[0074] The first bearing 34 preferably has a diameter D1 greater than that D2 of the teeth 33 of the sun 26, and the second bearing 36 has a diameter D3 less than that D2 of the teeth 33 of the sun 26.

[0075] In the example shown, the first bearing 34 is carried by the radial wall 26b, and the second bearing 36 is located inside the internal cylindrical wall 26c.

[0076] In the example also shown, the crown 28 has a general L or C shape in axial section and comprises:

[0077] - an external cylindrical wall 28a which comprises or carries an internal toothing 38,

[0078] - a radial annular wall 28b which extends from the external cylindrical wall 28a inwards,

[0079] - 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.

[0080] The rotor 16 may extend at least partly around the internal toothing 38 of the crown 28. The geared motor 10 further comprises an output shaft 50 in the example shown, which is coupled by splines 40 to the internal periphery of the radial wall 28b or to the internal cylindrical wall 28c.

[0081] As in the example shown, the planet carrier 32 is fixed to a casing 42 of the geared motor 10.

[0082] The stator 18 of the motor 12 may be attached directly to the housing 42 or carried directly by the housing 42.

[0083] The casing 42 may have a general L or C shape in axial section and comprise:

[0084] - an external cylindrical wall 42a,

[0085] - a radial annular wall 42b which extends from the external cylindrical wall inwards,

[0086] - 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.

[0087] The geared motor 10 may comprise a bearing 44 for guiding the output shaft 50, this bearing 44 being mounted between the output shaft 50 and the internal periphery of the radial wall 42b or the internal cylindrical wall 42c of the casing 42.

[0088] The planet carrier 32 can be fixed to the radial wall 42b of the casing 42, as in the example shown.

[0089] Conventionally, each of the satellites 30 is guided by a bearing 60 which is crossed by a finger 62 carried by the planet 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.

[0090] 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. Figure 3 is a larger scale view of a satellite 30, its guide bearing 60, here with needles, and its finger 62 for mounting on the satellite carrier 32.

[0091] To prevent the satellite 30 from coming into contact with the planet carrier 32 and rubbing against it, it would be possible to provide axial stops 70 between the satellites 30 and the planet carrier 32. In practice, these axial stops 70 would be in the form of rolling stops, for example ball stops as in the example shown.

[0092] However, these stops 70 should be continuously lubricated during operation of the reducer 10 to ensure their proper functioning. Furthermore, each of the stops 70 comprising two bearing rings 70a, 70b between which balls 70c are mounted, this solution would also be penalizing in terms of axial size and mass.

[0093] The present invention provides a solution to this problem, one embodiment of which is illustrated in Figures 4 and 5.

[0094] The invention proposes to provide axial retention elements for the satellites 30 on the fingers 62, at the axial ends of each satellite 30. 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.

[0095] 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 respectively comprise faces 80a1, 80b1 facing the same magnetic pole so that the magnets 80a, 80b repel each other.

[0096] A second pair of magnets 82 is mounted at the opposite axial end of the satellite 30. The magnets 82a, 82b respectively have faces 82a1, 82b1 facing the same magnetic pole so that the magnets 82a, 82b repel each other (arrow F1 in FIG. 4.) As in the example shown, the magnets 80a, 80b, 82a, 82b of each pair of magnets each have a generally annular shape and are mounted around the fingers 62. They may, for example, be in the form of washers, the lateral annular faces of which are preferably flat.

[0097] The magnets are preferably permanent magnets, for example made of Neodymium or Samarium-Cobalt.

[0098] 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 in particular depend on the mass of the satellites.

[0099] This repulsive force depends, for example, on the mass of the satellites and the acceleration of the aircraft. For example, for a 2 kg satellite undergoing a vertical acceleration of 5 kg, the force of the magnet would be greater than 2 x 9.81 x 5 = 98.1 N.

[0100] Preferably, each pair of magnets 80, 82 is interposed axially between the axial end of the satellite 30 and the planet carrier 32, and in particular between the axial end of the satellite 30 and a radial wall 32a of the planet carrier. This radial wall 32a may comprise an orifice 84 for mounting an axial end of the finger 62, as in the example shown.

[0101] Each pair of magnets 80, 82 can further be interposed axially between an axial end of the bearing 60 of the satellite 30 and the planet carrier 32.

[0102] The magnets 80a, 80b preferably have identical dimensions.

[0103] The magnets 82a, 82b preferably have identical dimensions.

[0104] The magnets 80a, 80b, 82a, 82b may further have identical dimensions as in the example shown.

[0105] 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.

[0106] The present invention provides several advantages including:

[0107] - magnetic retaining elements do not require lubrication and the elimination of lubrication in this area allows for simplified lubrication and a reduction in the mass of the reducer; - the retaining elements have no rotating parts in contact, so they cannot wear out due to friction, which increases its reliability;

[0108] - the retaining elements prevent friction between the satellites and the planet carrier, which reduces the overall losses of the reducer and therefore improves its efficiency; etc.

Claims

CLAIMS 1. Reducer (10) for an aircraft, this reducer (10) comprising: - a solar (26) mobile in rotation around a first axis (A), - a crown (28) mounted around the axis (A) and the sun (26), - satellites (30) interposed between the sun (26) and the crown (28) and meshed with the sun (26) and the crown (28), - a planet carrier (32) on which are mounted fingers (62) for mounting 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 (62), these bearings (60) being crossed by the fingers (62) and interposed between the satellites (30) and the fingers (62), characterized in that it further comprises elements for axially retaining 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 repulsion faces (80a1, 80b1) mounted opposite each other, these first repulsion 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 repulsion faces (82a1, 82b1) mounted opposite each other, these second repulsion faces having the same magnetic pole so that the magnets (82a, 82b) repel each other.

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

3. Reducer (10) according to claim 1 or 2, in which each pair of magnets (80, 82) is interposed axially 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, in which each pair of magnets (80, 82) is further axially interposed between an axial end of a bearing (60) of a satellite (30) and the planet carrier (32) or between an axial end of a bearing (60) of a satellite (30) and an axial end of a finger (62).

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

6. Reducer (10) according to one of the preceding claims, in which the magnets (80a, 80b, 82a, 82b) of each pair of magnets (80, 82) 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).

7. Reducer (10) according to 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), in which 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 7 for driving a propulsion propeller.

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