CROWN GEAR FOR AN AIRCRAFT MECHANICAL REDUCER

Abstract

A ring gear (90) for an aircraft mechanical gearbox (6), said ring gear (90) having an annular shape around an axis (X) and comprising: - internal teeth (92) on its inner periphery, - an external annular flange or splines (94) on its outer periphery, and - an annular web (96) extending between the internal teeth (92) and the external flange or splines (94), characterized in that the web (96) comprises an annular row of arms (98) distributed around said axis (X), these arms (98) connecting the internal teeth (92) to the external flange or splines (94) and being formed in one piece with the internal teeth (92) and the external flange or splines (94). Figure for the abbreviation: Figure 3

Description

Title of the invention: CROWN FOR A MECHANICAL AIRCRAFT REDUCER Technical field of the invention

[0001] The present invention relates to a ring gear 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. Technical background

[0002] 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-B1-3 098 562 and FR-B1-3 101 129.

[0003] 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.

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

[0006] 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 axis of the turbomachine or landing gear wheel. 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 X.

[0007] Several gearbox architectures exist. In the state of the art, gearboxes are of the planetary or epicyclic type. In other similar applications, there are so-called differential or "compound" architectures.

[0008] - 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.

[0009] - 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.

[0010] - 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.

[0011] 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 fields. There are several types of contact meshing, such as with spur, helical, or herringbone teeth.

[0012] Reducers can be composed of one or more meshing stages. This meshing is achieved in various ways such as by contact, by friction or by magnetic fields.

[0013] A satellite may comprise one or two gear stages. In this application, "stage" or "gear" means a series of meshing teeth with a series of complementary teeth. A gear may be internal or external. A single-stage satellite comprises a gear that may be straight, helical, or chevron-shaped, and whose teeth are located on the same diameter. This gear cooperates with both the sun gear and the crown gear.

[0014] A two-stage satellite comprises two sets of teeth or two series of teeth which are located on different diameters. A first set of teeth cooperates with the sun gear and a second set of teeth cooperates with the crown gear.

[0015] There is also a configuration, called Wolfrom, in which the satellites are double-staged and comprise a first set of teeth that cooperate with the sun gear and a ring gear, and a second set of teeth that cooperate with a second ring gear. The reduction gear thus comprises two ring gears, one of which is fixed and the other movable.

[0016] In order to add flexibility to a reducer, a classic solution is to fix the fixed ring of the reducer by means of a ring carrier having a "bellows" shape, as described by patent FR-B1-3 072 749. This solution is however difficult to integrate into a confined space.

[0017] Other solutions have been developed to enable the crown gear to absorb vibrations, consisting of integrating springs or elastomer pads into the crown. However, these solutions do not adequately withstand the meshing forces without causing significant deformation of the crown gear teeth. Furthermore, the low stiffness of the pads precludes their use in high-power applications.

[0018] The invention makes it possible to provide a solution to at least some of these problems, in a simple, efficient and economical way. Summary of the invention

[0019] The invention relates to a ring gear for an aircraft mechanical gearbox, this ring gear having an annular shape around an axis and comprising:

[0020] - an internal dentition at its inner periphery,

[0021] - an external flange or annular groove(s) at its outer periphery, and

[0022] - an annular veil extending between the internal teeth and the flange or the grooves extreme(s),

[0023] characterized in that the sail comprises an annular row of arms which are distributed around said axis, these arms connecting the internal teeth to the flange or the extreme splines and being formed in one piece with the internal teeth and the flange or the extreme splines.

[0024] The invention makes it possible to introduce flexibility into the ring gear and therefore into the gearbox, while maintaining a compact size. This is made possible by integrating this flexibility into the ring gear web, between its teeth and its flange or splines. This flexibility is generated by arms that resemble the spokes of a bicycle wheel, for example. These arms absorb the meshing forces through tensile or compressive work, while allowing radial flexibility through bending work.

[0025] The solution proposed below is compatible with single-stage or multi-stage gearboxes. It is compatible with epicyclic, planetary, differential, or Wolfrom-type gearboxes. It is also compatible with spur, helical, or herringbone gears. It is compatible with all types of planet carriers, and in particular with a one-piece planet carrier. Furthermore, it is compatible with all types of bearings, whether composed of rolling elements, hydrodynamic bearings, etc. It is compatible with the use of the ring gear and gearbox in a turbofan engine, for example, to drive a fan or a propeller. It is also compatible with the use of the ring gear and gearbox in a landing gear wheel drive system.

[0026] The crown according to the invention may comprise one or more of the following features, taken individually or in combination with each other: • the arms are separated from each other by spaces, or delimit spaces between them; • each or at least a part of said spaces has a general parallelepiped, trapezoidal, triangular, or rhomboid shape; • said spaces are formed by circular or oblong openings; • the veil comprises a first annular row of orifices located on a first circumference, and a second annular row of orifices located on a second circumference whose diameter is greater than that of the first circumference, the orifices of the first row being located circumferentially between the orifices of the second row; • said spaces are empty; • said spaces are filled by blocks made of a different material than the main material of the crown, and for example in polymer; • the arms are inclined obliquely with respect to a radial direction and have an inclination orientation in the same circumferential direction;

[0027] — the arms are all oriented in the same way; • a first set of arms is oriented in a first way, and a second set of arms is oriented in a second way, different from the first way; • the arms of the first set are crossed with the arms of the second set;

[0028] — the arms are all inclined with respect to rays said axis; • the arms are all located in the same plane perpendicular to said axis; • the number of arms is greater than 2, for example greater than 5 or 10, of Preference is greater than 20, and more preferably between 20 and 100; this number depends for example on the diameter of the crown.

[0029] The present invention also relates to a mechanical gearbox for an aircraft, this gearbox comprising:

[0030] - a mobile solar element rotating around an axis,

[0031] - a crown as described above, mounted around the solar element and said axis, and

[0032] - satellites mounted between the solar system and the corona and meshed with the solar system and the crown, these satellites having axes of rotation parallel to said axis.

[0033] The invention further relates to a turbomachine or a landing gear wheel drive system, in particular of an aircraft, comprising at least one ring gear or mechanical reducer as described above. Brief description of the figures

[0034] 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:

[0035] [Fig-1] [Fig.1] is a schematic axial cross-sectional view of a turbomachine aircraft,

[0036] [Fig.2] [Fig.2] is a partial schematic axial cross-sectional view of a mechanical reducer,

[0037] [Fig.3] [Fig.3] is a schematic front view of a crown according to a first embodiment of the invention,

[0038] [Fig.4] [Fig.4] is another schematic perspective view of the crown of [Fig.3],

[0039] [Fig. 5] [Fig. 5] is a partial schematic perspective view of the crown of the [Fig.3],

[0040] [Fig.6] [Fig.6] is a view similar to that of [Fig.5] and illustrates a variant of realization of the invention,

[0041] [Fig.7] [Fig.7] is a view similar to that of [Fig.5] and illustrates another variant embodiment of the invention,

[0042] [Fig.8] [Fig.8] is a view similar to that of [Fig.5] and illustrates another variant embodiment of the invention,

[0043] [Fig.9] [Fig.9] is a view similar to that of [Fig.5] and illustrates another variant embodiment of the invention,

[0044] [Fig. 10] [Fig. 10] is a schematic perspective view of an aircraft landing gear wheel and a drive system for that wheel. Detailed description of the invention

[0045] Figure 1 describes a turbomachine 1 which conventionally comprises a fan S, a low-pressure compressor 1a, a high-pressure compressor 1b, an annular combustion chamber 1e, a high-pressure turbine Id, a low-pressure turbine 1e, and an exhaust nozzle Ih. The high-pressure compressor 1b and the high-pressure turbine Id are connected by a high-pressure shaft 2 and together form a high-pressure (HP) housing. The low-pressure compressor 1a and the low-pressure turbine 1e are connected by a low-pressure shaft 3 and together form a low-pressure (LP) housing.

[0046] The blower S is driven by a blower shaft 4 which is driven in rotation with the BP shaft 3 by means of a reducer 6. This reducer 6 is generally of the planetary or epicycloidal type.

[0047] Although the following description relates to a planetary or epicyclic type gearbox, it also applies to a mechanical differential in which the three components—the planet carrier, the ring gear, and the sun gear—are free to rotate, the rotational speed of one of these components depending, in particular, on the difference in speeds of the other two components. It also applies to the specific case of a two-stage Wolfrom-type gearbox.

[0048] The reducer 6 is positioned in the upstream part of the turbomachine. A fixed structure schematically comprising, here, an upstream part 5a and a downstream part 5b which make up the motor or stator housing 5 is arranged 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 passage of the blower shaft 4, and downstream by seals at the level of the passage of the BP shaft 3.

[0049] Figure 2 shows a gearbox 6 which can take the form of different architectures depending on whether certain parts are fixed or rotating. At the input, the gearbox 6 is connected to the shaft BP 3, for example via internal splines 7a. Thus, the shaft BP 3 drives a planetary gear called the sun gear 7. Conventionally, the sun gear 7, whose axis of rotation coincides with that of the turbomachine X, drives a series of gears called planet gears 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 planet gears 8. The number of planet gears 8 is generally defined between three and seven for this type of application.

[0050] 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 ring 9.

[0051] The output we have: • In an epicyclic configuration, the set of satellites 8 drives the planet carrier 10 in rotation around the X-axis of the turbomachine. The ring gear is fixed to the motor or stator housing 5 via a ring carrier 12 and the planet carrier 10 is fixed to the fan shaft 4. • In a planetary configuration, the set of satellites 8 is held by a satellite carrier 10 which is fixed to the motor or stator housing 5. Each satellite drives the ring which is brought to the blower shaft 4 via a ring carrier 12.

[0052] Each satellite 8 is mounted to rotate freely by means of a bearing 11, for example of the rolling 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 supported by walls 10a1, 10a2 of the satellite carrier 10.

[0053] The walls lOal, 10a2 have an annular shape and are perpendicular to the X axis. They are at an axial distance from each other and receive between them the bearings 11, the satellites 8 and the solar 7.

[0054] There is a number of bearings 11 equal to the number of satellites 8. For reasons of operation, assembly, manufacture, 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.

[0055] For the same reasons mentioned above, the teeth 8d of a gearbox can be separated into several helices, each having a median plane P. In our example, we detail the operation of a multi-helix gearbox with a ring gear separated into two half-ring gears: • an upstream half-crown 9a consisting of a rim 9aa and a mounting half-flange 9ab. The upstream helix of the gear teeth is located on the rim 9aa. reduction gear. This upstream helix meshes with that of satellite 8 which meshes with that of solar 7. • a downstream half-crown 9b consisting of a rim 9ba and a mounting flange half 9bb. On the rim 9ba is the downstream helix of the reduction gear teeth. This downstream helix meshes with that of the satellite 8, which meshes with that of the solar 7.

[0056] If the helix widths vary between the solar 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 helices and on another median plane P for the downstream helices.

[0057] The mounting half-flange 9ab of the upstream crown 9a and the mounting half-flange 9bb of the downstream crown 9b form the mounting flange 9c of the crown. The crown 9 is fixed to a crown carrier by assembling the mounting flange 9c of the crown and the mounting flange 12a of the crown carrier using, for example, a bolted assembly.

[0058] Alternatively, the flange 9c of the crown 9 could be replaced by grooves.

[0059] The arrows in [Fig.2] describe the flow of oil into reducer 6. Oil enters the gearbox 6 from the stator section 5 and the distributor 13 via various means, which will not be detailed in this view as they are specific to one or more types of architecture. The distributor is generally divided into two parts, each typically repeated with the same number of planet gears. Injectors 13a lubricate the gear teeth, and arms 13b lubricate the bearings 11. Oil is supplied to injectors 13a and exits through ends 13c to lubricate the gear teeth of the planet gears 8, the sun gear 7, and the ring gear 9. Oil is also supplied to arm 13b and flows through the feed port 13d of the bearing body 10b into an internal cavity 10c within the latter. The oil then circulates in this cavity 10c to supply oil passage orifices lOd to ​​an external cylindrical surface for guiding the corresponding satellite.

[0060] The present invention relates to a ring gear for a mechanical aircraft gearbox 6. This gearbox 6 may be of the type described above or of another type, for example, a two-stage gearbox of the Wolfrom type. Furthermore, this gearbox 6 may 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 wheel drive system for an aircraft landing gear (see [Fig. 10]).

[0061] It should be noted that the ring according to the invention may be the only ring of the reducer 6, and may be a fixed or movable ring. Alternatively, the reducer 6 could comprise two rings according to the invention. One of these rings could be fixed and the other could be movable. The two rings could in besides being fixed or mobile. As an example, each of these two crowns could be considered as a half-crown as illustrated in [Fig.2], the two crowns (or half-crowns) then being fixed together and to a crown holder by their flanges or grooves.

[0062] Figures 3 to 5 illustrate a first embodiment of a 90 crown according to the invention, and figures 6 and following illustrate variant embodiments of this 90 crown.

[0063] The crown 90 is preferably metallic. Its main material is therefore a metallic alloy.

[0064] The crown 90 of figures 3 to 5 has an annular shape around the X axis and comprises:

[0065] - an internal dentition 92 at its internal periphery,

[0066] - an external flange or annular groove(s) 94 at its external periphery, and

[0067] - an annular veil 96 extending between the internal teeth 92 and the external flange or the groove(s) 94.

[0068] The particularity of this crown 90 is that its veil 96 includes an annular row of arms 98 which are distributed around the axis X, these arms connecting the internal teeth 92 to the flange or the splines 94 and being formed in one piece with the internal teeth 92 and the flange or the splines 94.

[0069] The toothing 92 is straight in the example shown but could alternatively be helical.

[0070] In the example shown, the flange 94 includes a plurality of axial holes 100 for the passage of fasteners such as screws or bolts. These holes 100 are formed in radially external lugs 102 of the flange 94. These lugs 102 are distributed around the X-axis. Alternatively, the holes 100 could be formed in a continuous annular wall of the flange 94.

[0071] The flange or the splines 94 is / are located in a plane H which is perpendicular to the axis X and which passes through the middle of the toothing 92 in the example shown.

[0072] The arms 98 preferably extend in this plane H.

[0073] In the embodiment shown in Figures 3 to 5, the arms 98 are regularly distributed around the X-axis and are spaced apart. They all have the same orientation and are inclined in the same direction with respect to radii to the X-axis. The angle α of inclination of each arm is, for example, between 20 and 70°.

[0074] In the case where the satellites meshed with the ring 90 rotate in the direction of arrow Fl, each of the arms 98 would undergo tensile work in a direction aligned with the extension axis of that arm 98 (arrow Fl 1 - [Fig. 5]). In the In the case where the satellites meshed with the ring gear 90 rotate in the direction of arrow F2, each of the arms 98 would be subjected to a compressive force along a direction aligned with the extension axis of that arm (arrow F21 - [Fig. 5]). Furthermore, the web 96, and therefore the ring gear 90, exhibits flexibility in the radial direction along arrow F3.

[0075] The arms 98 define between them spaces 104 which are empty and here have a general parallelepiped shape.

[0076] Each of the arms 98 includes a first radially external end for connection to the flange or the splines 94, and a second radially internal end for connection to the teeth 92. These ends can be enlarged in relation to the rest of the arm and in particular to the middle part of the arm, as can be seen in [Fig.5].

[0077] Generally, due to the spaces 104 created between the arms 98, these arms can be oversized to resist the forces in operation, without significantly impacting the mass of the crown 90. This oversizing can be done for example in a direction parallel to the X axis, the arms 98 having for example a width in this direction which is greater than the width of a crown web of the prior art.

[0078] Furthermore, the arms 98 can have any shape in cross-section and for example square, rectangular, round, elliptical, etc. This cross-sectional shape can also vary along the axis of extension of the arm 98.

[0079] The variant embodiment of [Fig.6] differs from the previous embodiment in that a series, and for example half, of the arms 98, 98a is oriented in a first way, and a second series, and for example half, of the arms 98, 98b is oriented in a second way, different from the first way.

[0080] Arms 98, 98a are for example inclined at a positive angle +[3 with respect to rays to the X axis, and arms 98, 98b are for example inclined at a negative angle -|3 with respect to rays to the X axis.

[0081] The arms 98 define between each other spaces 104 which are empty and here have a general trapezoidal shape. A first series of trapezoids have their small bases located outside their large bases, and the other series of trapezoids, arranged between the trapezoids of the first series, have their small bases located inside their large bases.

[0082] The ends of the arms 98 are also enlarged.

[0083] The variant embodiment of [Fig.7] differs from the previous embodiment in that the arms 98, 98a of the first series are interlaced with the arms 98, 98b of the second series.

[0084] The arms 98 define between themselves spaces 104, 106 which are empty and here have general triangular and rhombic shapes. A pair of intersecting arms 98a, 98b together delimit two triangular spaces 106 located respectively inside and outside arms 98a, 98b. Two pairs of adjacent arms 98a, 98b delimit between themselves a rhombus-shaped space 104.

[0085] The variant embodiment of [Fig.8] differs from previous embodiments in that the empty spaces 104 between the arms 98 are formed by circular orifices 108a, 108b.

[0086] The veil 96 comprises a first annular row of orifices 108a located on a first circumference, and a second annular row of orifices 108b located on a second circumference whose diameter is greater than that of the first circumference, the orifices 108a of the first row being located between the orifices 108b of the second row.

[0087] The variant embodiment of [Fig. 9] differs from the first embodiment in that the spaces 104 are filled with blocks 110 made of a material different from the main material of the crown, and which are, for example, made of polymer. The polymer is, for example, chosen from: polyetheretherketone, polyamide, polyimide, bismaleimide, epoxy, phenoplasts (e.g., polystyrene), polyesters, polyurethanes, silicone rubbers, nylons, copolymers, polymer blends, etc.

[0088] The blocks 110 can be designed to take up part of the meshing forces, and thus reduce the cross-section of the arms 98 for the purpose of mass saving.

[0089] The spaces 104, 106 between the arms 98 of the other embodiment variants of figures 6 to 8 could also be filled with similar blocks 110.

[0090] The number of arms 98 of the crown 90 is, for example, greater than 2, 5, or 10, preferably greater than 20, and more preferably between 20 and 100. This number depends in particular on the level of load on the teeth 92 of the crown 90 during operation. A lightly loaded crown 90 will have fewer arms 98 than a more heavily loaded crown during operation. Similarly, the inclination of the arms 98 will depend on the load on the crown 90 and the desired flexibility.

[0091] Fig. 10 shows a drive system 210 for at least one wheel 212 of an aircraft landing gear 214.

[0092] The wheel 212 has a rim 216 which has an axis of rotation X. In a conventional manner, this rim 216 has a general tubular or disc shape and carries a tire 218 on its periphery.

[0093] The system 210 includes an electric motor 220 and a mechanical transmission system 222 between a shaft of the motor 220 and the rim 216 of the wheel 212.

[0094] In the example shown, the motor 220 and the system 222 each have a generally annular shape and are centered on the X-axis. They are arranged side by side, and the system 222 is installed between the motor 220 and the rim 216. Part of the system 222, or even part of the 220 engine, could be housed in the rim 16 to reduce the bulk of system 210. The engine 220 and system 222 can be protected by an external cylindrical cover 226 projecting on one side of the rim 216 or tire 218.

[0095] The mechanical transmission system 222 includes a mechanical reducer 228 similar to the reducer 6 described above.

Claims

Demands

1. Crown (90) for an aircraft mechanical reducer (6, 228), said crown (90) having an annular shape around an axis (X) and comprising: - an internal toothing (92) at its internal periphery, - an external annular flange or splines (94) at its external periphery, and - an annular web (96) extending between the internal toothing (92) and the external flange or splines (94), characterized in that the web (96) comprises an annular row of arms (98) which are distributed around said axis (X), these arms (98) connecting the internal toothing (92) to the external flange or splines (94) and being formed in one piece with the internal toothing (92) and the external flange or splines (94).

2. Crown (90) according to claim 1, wherein the arms (98) are separated from each other by spaces (104, 106), or delimit spaces (104, 106) between each other.

3. Crown (90) according to claim 2, wherein each or at least a part of said spaces (104, 106) has a general parallelepiped, trapezoidal, triangular, or rhomboid shape.

4. Crown (90) according to claim 2, wherein said spaces are formed by circular or oblong orifices (108a, 108b).

5. Crown (90) according to claim 4, wherein the veil (96) comprises a first annular row of orifices (108a) located on a first circumference, and a second annular row of orifices (108b) located on a second circumference whose diameter is greater than that of the first circumference, the orifices (108a) of the first row being located circumferentially between the orifices (108b) of the second row.

6. Crown (90) according to any one of claims 2 to 5, wherein said spaces (104, 106) are empty.

7. Crown (90) according to any one of claims 2 to 5, wherein said spaces (104) are filled by blocks (110) made of a material different from the main material of the crown, and for example of polymer.

8. Crown (90) according to any one of claims 1 to 7, wherein the arms (98) are inclined obliquely with respect to a direction radial and exhibit an inclination orientation in the same circumferential direction.

9. Crown (90) according to any one of claims 1 to 8, wherein a first set of arms (98a) is oriented in a first way, and a second set of arms (98b) is oriented in a second way, different from the first way.

10. Crown (90) according to claim 9, wherein the arms (98a) of the first series are interlaced with the arms (98b) of the second series.

11. Crown (90) according to any one of claims 1 to 10, wherein the arms (98) are all located in the same plane (P) perpendicular to said axis (X).

12. Crown (90) according to any one of claims 1 to 11, wherein the number of arms (98) is greater than 2, for example greater than 5 or 10, preferably greater than 20, and more preferably between 20 and 100.

13. Mechanical reducer (6, 228) for an aircraft, said reducer (6, 228) comprising: - a solar (7) movable in rotation about an axis, - a ring (90) according to one of the preceding claims, mounted around the solar (7) and said axis (X), and - satellites (8) mounted between the solar (7) and the ring (90) and meshed with the solar and the ring, these satellites (8) having axes of rotation (Y) parallel to said axis (X).

14. Turbomachine (1), in particular aircraft, comprising at least one ring gear (90) according to any one of claims 1 to 12 or a mechanical reducer (6, 228) according to claim 13.

15. A system (210) for driving a wheel (212) of a landing gear (214), in particular of an aircraft, comprising at least one ring gear (90) according to any one of claims 1 to 12 or a mechanical reducer (228) according to claim 13.

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