Planet carrier for a mechanical reduction gearbox of a turbo engine of an aircraft

Description

Technical field of the invention

[0001] The present invention relates to the field of mechanical reducers for turbomachinery, in particular aircraft, and in particular reducers equipped with double-stage geared satellites. Technical background

[0002] The state of the art includes in particular documents WO-A1-2010 / 092263, FR-A1-2 987 416, FR-A1-3 011 901, FR-A1-3 041 054, FR-A1-3 058 493, US-A1-2010 / 292044, US-A1-2018 / 051798 and US-A1-2013 / 184120.

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

[0004] Newer generations of turbofan engines, particularly those with a high bypass ratio, incorporate a mechanical gearbox to drive the fan shaft. Typically, the gearbox's purpose is to transform the high rotational speed of the power turbine shaft into a slower rotational speed for the fan 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 the planet carrier. The sun gear, ring gear, and planet carrier are planetary gears because their axes of revolution coincide with the longitudinal X-axis of the turbomachine. The planet gears each have a different axis of revolution and are evenly spaced on the same operating diameter around the axis of the planet gears. These axes are parallel to the longitudinal X-axis.

[0006] Several gearbox architectures exist. In state-of-the-art turbomachinery, gearboxes are of the planetary or epicyclic type. In other similar applications, differential or compound architectures exist. In a planetary gearbox, the planet carrier is fixed, and the ring gear forms the output shaft of the device, rotating in the opposite direction to the sun gear. In an epicyclic gearbox, the ring gear is fixed, and the planet carrier forms the output shaft of the device, rotating in the same direction as the sun gear. In a differential gearbox, no element is fixed for rotation. The ring gear rotates in the opposite direction to both the sun gear and the planet carrier.

[0007] Gearboxes can consist of one or more meshing stages. This meshing is achieved in various ways, such as by contact, friction, or magnetic fields.

[0008] In this application, the terms "stage" or "toothing" refer to a series of interlocking teeth with a series of complementary teeth. A toothing can be internal or external.

[0009] A satellite can have one or two gear stages. A single-stage satellite has teeth that can be straight, helical, or chevron-shaped, with teeth on the same diameter. These teeth cooperate with both the sun gear and the crown gear.

[0010] A two-stage satellite comprises two sets of teeth or two series of teeth located on different diameters. One set of teeth cooperates with the sun gear and a second set of teeth cooperates with the crown gear.

[0011] There are two satellite carrier technologies: monobloc satellite carriers and satellite carriers that consist of a cage and a carrier cage connected together by flexible links.

[0012] The present invention relates to monobloc type satellite carriers. A satellite carrier of this type comprises a cage formed in one piece with a portion of shaft.

[0013] The cage comprises two annular flanges connected by material bridges, these material bridges defining satellite reception housings between themselves and with the flanges. The flanges have mounting holes for the axial ends of the satellite guidance bearings. These holes are commonly called "reception holes".

[0014] One of the problems with this type of gearbox concerns the transmission of forces during operation and the risk of planet gear misalignment. In a one-piece planet carrier, the forces applied to the planets are transmitted via the bearings to the carrier flanges. The planet carrier's configuration does not allow for the centered distribution of these forces due to the presence of the ring gear. Therefore, the balancing of forces must be achieved through the planet carrier's geometry. However, the planet carrier is a complex component with limited space available to accommodate this specific geometry.

[0015] The invention provides a solution to this problem in a simple, efficient and economical way. Summary of the invention

[0016] The invention relates to a satellite carrier according to claim 1.

[0017] The invention thus proposes to locally reduce the thickness of the first flange, around each of its openings, in order to increase its flexibility (or reduce its stiffness). The first flange therefore has, around its openings, a stiffness lower than the stiffness of the second flange, around the openings of this second flange. The thinning, and therefore the reduction in flexibility, is carried out on the first flange and not on the second flange, that is to say, on the side where the load is transferred by the shaft portion of the planet carrier. Advantageously, the flexibility of the first flange is compensated by the rigidity of the shaft portion so that the overall stiffnesses on both sides of each bearing are substantially identical and therefore balanced.

[0018] Thinning can be achieved by machining the first flange, for example.

[0019] To achieve optimum stiffness, the thickness around each of the openings of the first flange must be as small as possible, but a minimum of material is necessary to ensure the transmission of the forces passing through and to limit the stresses.

[0020] This invention is compatible with: of a single stage or double stage reducer; of a planetary, epicyclic or differential reducer; of a one-piece planet carrier; of any type of toothing (straight, helical or herringbone); of hydrodynamic and / or rolling element bearings.

[0021] The satellite carrier according to the invention may comprise, in accordance with the claims, one or more of the following features, taken individually or in combination with each other: the first flange comprises a first face situated on the side of said portion of tree, and a second face situated on the side of the second flange, at least the first face and / or the second face having said two or three grooves; it is thus understood that the grooves extending around an orifice can be situated on one or both faces of the first flange, the grooves formed on the first face and / or the second face have different diameters, said grooves are three in number and comprise two grooves which are situated on one of the first and second faces and which extend around each other and have diameters D1 and D3 respectively, and a groove situated on the other of the first and second faces and which has a diameter D2 between D1 and D3;The grooves of diameters D1, D2 and D3 thus extend around the same orifice, where each groove has a generally curved or semi-circular shape in section, the thinning reduces by at least 50% the thickness of the first flange, each of the first orifices has an internal diameter which is less than the internal diameter of each of the second orifices, said portion of shaft includes an external toothing.

[0022] The present invention further relates to a mechanical reducer for an aircraft turbomachine, this reducer comprising a satellite carrier as described above, satellites which are housed in said housings and which are guided by bearings whose axial ends are engaged in said first and second orifices, and a solar which is housed in the cage and which is meshed with the satellites.

[0023] The present invention further relates to an aircraft turbomachine comprising a satellite carrier or a reduction gear as described above. Brief description of the figures

[0024] 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: [ Fig.1 ] there figure 1 is a schematic axial cross-sectional view of an aircraft turbomachine, [ Fig. 2 ] there figure 2 is a partial axial view of a mechanical reducer, [ Fig.3 ] there figure 3 is an axial cross-sectional view of a mechanical reducer equipped with double-stage meshing satellites, and illustrates the prior art of the invention, [ Fig. 4 ] there figure 4 is a perspective view of the planet carrier of the gearbox of the figure 3 , [ Fig. 5 ] there figure 5is a partial axial view of a planet carrier and a mechanical reducer according to an embodiment of the invention, [ Fig. 6 ] there figure 6 is an axial cross-sectional and perspective view of a satellite carrier according to an embodiment of the invention; and [ Fig. 7a-7b ] THE figures 7a and 7b are views similar to that of the figure 6 and show the satellite carrier of the figure 6 associated respectively with a single-stage satellite and a dual-stage satellite. Detailed description of the invention

[0025] There figure 1This describes a turbomachine 1 which conventionally comprises a rotation shaft X, a fan S, a low-pressure compressor 1a, a high-pressure compressor 1b, an annular combustion chamber 1c, a high-pressure turbine 1d, a low-pressure turbine 1e, and an exhaust nozzle 1h. The high-pressure compressor 1b and the high-pressure turbine 1d are connected by a high-pressure shaft 2 and together form a high-pressure (HP) unit. 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) unit.

[0026] The blower S is driven by a blower shaft 4 which is driven to the BP shaft 3 by means of a reducer 6. This reducer 6 is generally of the planetary or epicycloidal type.

[0027] The following description relates to a planetary type reducer in which the ring gear is mobile in rotation.

[0028] The gearbox 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 gearbox 6. This enclosure E is 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.

[0029] There figure 2Figure 6 shows a reduction gear that can take on different forms depending on whether certain parts are fixed or rotating. At the input, the reduction gear 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. Typically, the sun gear 7, whose axis of rotation coincides with that of the turbomachine X, drives a series of gears called sun gears 8, which are evenly spaced on 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 sun gears 8. The number of sun gears 8 is generally defined between three and seven for this type of application.

[0030] The set of satellites 8 is held by a frame called the satellite carrier 10. Each satellite 8 rotates around its own Y axis, and meshes with the ring 9. ▪ In this planetary configuration, the set of satellites 8 is held by a satellite carrier 10 which is fixed to the motor housing or stator 5. Each satellite drives the ring which is brought to the blower shaft 4 via a ring carrier 12.

[0031] Each satellite 8 is mounted to rotate freely using a bearing 11, for example, a roller bearing or hydrodynamic bearing. Each bearing 11 is mounted on one of the axes 10b of the satellite carrier 10, and all the axes are positioned relative to each other using one or more structural frames 10a of the satellite carrier 10. There is a number of axes 10b and bearings 11 equal to the number of satellites. For operational, assembly, manufacturing, inspection, repair, or replacement purposes, the axes 10b and the frame 10a may be separated into several parts.

[0032] For the same reasons mentioned above, the teeth of a gearbox can be separated into several helices, each with a median plane P. In the example shown, the ring gear is separated into two half-rings: ▪ An upstream half-crown 9a consisting of a rim 9aa and a mounting flange half 9ab. The upstream helix of the reduction gear teeth is located on the rim 9aa. This upstream helix meshes with that of the satellite gear 8, which meshes with that of the solar gear 7. ▪ A downstream half-crown 9b consisting of a rim 9ba and a mounting flange half 9bb. The downstream helix of the reduction gear teeth is located on the rim 9ba. This downstream helix meshes with that of the satellite gear 8, which meshes with that of the solar gear 7.

[0033] The mounting half-flange 9ab of the upstream sprocket 9a and the mounting half-flange 9bb of the downstream sprocket 9b form the mounting flange 9c of the sprocket. The sprocket 9 is fixed to a sprocket carrier by assembling the mounting flange 9c of the sprocket and the mounting flange 12a of the sprocket carrier using, for example, a bolted assembly.

[0034] The arrows of the figure 2The diagram describes the oil delivery within the gearbox 6. Oil enters the gearbox 6 from the stator section 5 via a distributor 13 by 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 sections, each typically repeated with the same number of planetary gears. Injectors 13a lubricate the gear teeth, and arms 13b lubricate the bearings. Oil is supplied to injector 13a and exits through end 13c to lubricate the gear teeth. Oil is also supplied to arm 13b and flows through the bearing's supply port 13d. The oil then flows through the shaft in one or more buffer zones 10c and exits through ports 10d to lubricate the planetary gear bearings.

[0035] THE figures 3 And 4represent a 6-speed gearbox for an aircraft turbomachine according to prior art.

[0036] The reducer 6 includes a planet carrier 10 which is configured to be mobile in rotation around the X axis and which is of the monobloc type, i.e. formed from a single piece.

[0037] This satellite carrier 10 includes a cage 14 and a shaft portion 15.

[0038] The portion of the shaft 15 has a general tubular shape and is elongated along the X axis and includes a free longitudinal end, here on the left in the drawings, and an opposite longitudinal end for connection to the cage 14.

[0039] The shaft portion 15 includes an external gear 15a for meshing, for example with a blower.

[0040] The cage 14 has two annular flanges 14a, 14b which are parallel and spaced apart and extend perpendicularly to the X axis. The flanges 14a, 14b have a general circular shape and are centered on the X axis.

[0041] The flange 14a, called the first flange, on the left in the drawing, is connected to the shaft portion 15. The other flange 14b is called the second flange.

[0042] The flanges 14a, 14b are connected to each other by material bridges 16 which define between themselves and with the flanges housings 18 configured to receive the satellites 8. The housings 18 open radially outwards at the external periphery of the cage 14, and also open radially inwards by passing through an internal tubular wall 20 of the cage 14. The material bridges 16 can be solid or partially hollow.

[0043] The wall 20 extends around the X axis, from the first flange 14a towards the second flange 14b. Here it extends substantially in the axial continuation of the portion of shaft 15. This wall 20 internally delimits a space 22 for housing the solar element 7.

[0044] This space 22 comprises two adjacent parts. The first part 22a is surrounded by the wall 20 which includes an internal cylindrical surface 22a for mounting a bearing 23 for guiding one end of the solar element 7. The second part 22b, located at the openings of the housings 18, receives the opposite end of the solar element 7, which includes an external toothed gear 7b for meshing with the satellites 8. The solar element 7 further includes an internal toothed gear 7a for coupling to a shaft, for example, of a turbine.

[0045] Each housing unit 18 comprises a first part 18a, located on the side of the first flange 14a, and a second part 18b, located on the side of the second flange 14b. Housing units 18 open onto the outer periphery of shaft 14, at the level of its two parts 18a and 18b, and onto the inner periphery of shaft 14, at the level of the second part 18b only.

[0046] The flanges 14a, 14b include aligned mounting holes 24 for the satellites 8 and in particular for the plain bearings 26 of these satellites 8. Each bearing 26 has a general cylindrical shape which extends parallel to the X axis and whose longitudinal ends include extensions 26a housed in the holes 24 forming seats.

[0047] As is known, each bearing 26 may include an internal oil circulation bore 26b which generally communicates with oil supply channels to the external cylindrical surface 26c of the bearing for the purpose of forming an oil film on this surface 26c.

[0048] The satellites 8 are here of the double-stage meshing type and each comprise a tubular body 8a equipped with a first external toothing 28 and connected by a web 30 to a second external toothing 32.

[0049] The teeth 28, 32 are arranged next to each other and more particularly are located respectively in two planes perpendicular to the X axis.

[0050] The first tooth 28, located on the left in the drawings, is situated on the side of the first flange 14a and therefore at the level of the first part 18a of the housing. As can be seen in the figure 3 , this toothing 28 is meshed with the crown 9.

[0051] The second toothing 32, located on the right in the drawings, is situated on the side of the second flange 14b and therefore at the level of the second part 18b of the housing. As can be seen in the figure 3 , this toothing 32 is meshed with the toothing 7b of the solar 7.

[0052] As we can see at the figure 3 , the material bridges 16 extend radially, between the housings 18, from the wall 20 and the inner periphery of the flanges 14a, 14b to the outer periphery of the flanges.

[0053] In this type of planet carrier, it is important to ensure the transfer of forces during operation between the turbine and the planet carrier. The forces are initially transmitted through the shaft section 15 and then to the upstream flange 14a. They then pass through the upstream flange 14a to transmit through the bearings 26 and the planets 8. This transmission of forces via one of the flanges risks causing the planets 8 to tilt and therefore misalignment between their teeth 28, 32 and those of the sun gear 7 and the ring gear 9.

[0054] The invention proposes to remedy this problem by means of a satellite carrier, a first embodiment of which is illustrated in the figure 5 and of which variants are illustrated in figures 7 , 8a and 8b.

[0055] The following description concerns the characteristics of the planet carrier according to the invention. This planet carrier is intended to be mounted in a mechanical gearbox of the aforementioned type, which will not be described in detail hereafter. The preceding description, made in relation to the figures 1 to 4 can thus be used to describe a reducer comprising a planet carrier according to the invention.

[0056] The 110 satellite carrier of the figure 5 is of the monobloc type, that is to say, formed from a single piece.

[0057] This satellite carrier 110 includes a cage 114 and a shaft portion 115.

[0058] The portion of shaft 115 has a general tubular shape and is elongated along the X axis and includes a free longitudinal end, here on the left in the drawings, and an opposite longitudinal end for connection to the cage 114.

[0059] The shaft portion 115 includes an external gear 115a for meshing, for example with a blower shaft.

[0060] The cage 114 has two annular flanges 114a, 114b which are parallel and spaced apart and extend perpendicularly to the X axis. The flanges 114a, 114b have a general circular shape and are centered on the X axis.

[0061] The flange 114a, called the first flange, on the left in the drawing, is connected to the shaft portion 115. The other flange 114b is called the second flange.

[0062] The flanges 114a and 114b are connected to each other by material bridges 116, which define housings 118 between themselves and with the flanges. These housings are configured to receive the satellites 8. The housings 118 open radially outwards at the outer periphery of the cage 114, and also radially inwards. The material bridges 116 may be solid or partially hollow.

[0063] The flanges 114a, 114b include aligned mounting holes 124a, 124b for the satellites 8 and, in particular, for the plain bearings 26 of these satellites 8. Each bearing 26 has a generally cylindrical shape extending parallel to the X-axis and whose longitudinal ends include extensions 26a housed in the holes 124, forming seats or recesses. The holes 124a of the first flange 14a are called the first holes, and the holes 124b of the second flange 14b are called the second holes.

[0064] As is known, each bearing 26 may include an internal oil circulation bore as mentioned above.

[0065] The satellites 8 are here of the single-stage meshing type and each comprise a tubular body 8a equipped with external teeth 28 intended to mesh with the crown (not shown) and the solar (also not shown).

[0066] According to the invention, the first flange 114a has at least one thinning 134 around each of the first orifices 124a. This thinning 134 defines a minimum thickness E1 of material in the axial direction which is less than a minimum thickness E2 of the second flange 114b around each of the second orifices 114b.

[0067] In the example shown, which is not limiting, the first flange 114a is double-walled and comprises two parallel walls 114a1 and 114a2, respectively a first wall 114a1 and a second wall 114a2, which are connected together by an annular web 136 at their outer peripheries. The first wall 114a1 is connected by material bridges 116 to the second flange 114b and includes the thinning 134. The second wall 114a2 is connected to the shaft portion 115.

[0068] Note: R0 is the internal diameter of the shaft portion 115, R1 the internal diameter of the first wall 114a1 or of the first flange 114a, R2 the external diameter of the first wall 114a1 or of the first flange 114a, R3 the internal diameter of the second wall 114a2, R4 the external diameter of the second wall 114a2, R5 the average or external diameter of the ferrule 136, R6 the internal diameter of the flange 114b, R7 the external diameter of the flange 114b.

[0069] These radii are measured with respect to the X-axis.

[0070] Preferably, R2, R4, R5 and R7 are close, similar or identical.

[0071] Preferably, R1 and R6 are close, similar, or identical.

[0072] Preferably, R0 and R3 are close, similar, or identical.

[0073] Preferably, R1 and R6 are close, similar, or identical.

[0074] Preferably, R1 is less than R3 and / or R0.

[0075] Preferably, R6 is less than R3 and / or R0.

[0076] The orifices 124a and 124b have diameters H1 and H2, respectively. In the example shown, these diameters are close, similar, or identical. These diameters are measured with respect to the Y-axis.

[0077] In a preferred embodiment of the invention, the thinning 134 comprises at least one groove 138, and preferably two or three coaxial grooves, extending around each of the orifices 124a.

[0078] The first flange 114a, and in particular its wall 114a2, comprises a first face 140a located on the side of the portion of the shaft, and a second face 140b located on the side of the second flange 114b.

[0079] In the example shown, face 140a has a groove 138 of diameter D2 and face 140b has a groove 138 of diameter D1. The diameters D1 and D2 are different and D1 is in particular smaller than D2 here.

[0080] Each groove 138 has a general curved or semi-circular shape in section.

[0081] Each groove 138 generates a reduction in the thickness of the first flange 114a, and in particular of the wall 114a1, which is preferably greater than or equal to 50%. In other words, E1 ≤ 0.5E3, where E3 is the average thickness of the rest of the flange 114a. Similarly, preferably E1 ≤ 0.5E2.

[0082] The formation, for example by machining, of the grooves 138 on the two faces 140a, 140b of the wall 114a1 and the fact that they have different diameters D1, D2 induces an S-shaped or bellows-shaped cross-section of the part of the flange 114a that extends around each orifice 124a.

[0083] There figure 6 illustrates a variant embodiment of the satellite carrier 110 in which the flange 114a is here equipped with three thinning grooves.

[0084] One of the faces of the wall 114a1, here face 140b, includes two grooves 138 which extend around each other and have diameters D1 and D3 respectively, and the other face 140a includes a groove 138 having a diameter D2 between D1 and D3.

[0085] Furthermore, in this variant, it is observed that the orifices 124a, 124b of the flanges have different diameters H1, H2. In particular, the orifices 124a of the first flange 114a each have an internal diameter H1 that is smaller than the internal diameter H2 of each of the orifices 124b of the second flange 114b.

[0086] This makes it possible to stiffen the edge of the orifice 124b opposite to the flexibility to increase its stiffness and to favour a small diameter for the orifice 124a in order to maximize the machinable area for the grooves 138.

[0087] THE figures 7a and 7bshow that the satellite carrier 110 according to the invention, whatever its embodiment, can be associated with single or double stage satellites 8.

[0088] The invention offers several advantages, including: Easy-to-implement solution in a constrained space; measurable and configurable gain in flexibility; improved centrality of forces on a monobloc satellite carrier.

Claims

1. A planet carrier (110) for a mechanical gearbox (6) of a turbomachine (1), in particular for an aircraft, this planet carrier having a main axis (X) and comprising a cage (114) formed in a single piece with a shaft portion (115) centred on the axis (X), the cage comprising two annular flasks (114a, 114b) extending around the axis (X), one of which, referred to as first flask (114a), is connected to said shaft portion (115), and the other, referred to as second flask (114b), is connected to the first flask by bridges of material (16) distributed around the axis (X), said bridges of material (116) defining between them and with the flasks (114a, 114b), housings (118) configured to receive planet gears (8), the first and second flasks (114a, 114b) comprising respectively first and second orifices (124a, 124b) for mounting the planet gears (8) which are oriented axially and which open into said housings (118), the first flask (114a) comprising a thinning (134) around each of the first orifices (124a), the thinning (134) defining a minimum thickness of material (E1) in the axial direction which is less than a minimum thickness (E2) of the second flask (114b) around each of the second orifices (124b), characterised in that the thinning (134) comprises two or three coaxial gorges (138) extending around each of said first orifices (124a), and in that the first flask (114a) is double-walled and comprises two parallel walls, respectively a first wall (114a1) and a second wall (114a2) which are connected together by an annular web (136) at the level of their external peripheries, the first wall (114a1) being connected by the material bridges (116) to the second flask (114b) and comprising said at least one thinning (134), and said second wall (114a2) being connected to said shaft portion (115).

2. The planet carrier (110) according to claim 1, wherein the first flask (114a) comprises a first face (140a) located on the side of said shaft portion (115), and a second face (140b) located on the side of the second flask (114b), at least the first face (140a) and / or the second face (140b) comprising said two or three gorges (138).

3. The planet carrier (110) according to claim 2, wherein the gorges (138) formed on the first face and / or the second face (140a, 140b) have different diameters (D1, D2, D3).

4. The planet carrier (110) according to claim 2 or 3, wherein said gorges (138) are three and comprise two gorges (138) which are located on one of the first and second faces (140b) and which extend around each other and have diameters D1 and D3 respectively, and one gorge (138) located on the other of the first and second faces (140a) and which has a diameter D2 between D1 and D3.

5. The planet carrier (110) according to any of the preceding claims, wherein each gorge (138) has a generally curved or semi-circular cross-sectional shape.

6. The planet carrier (110) according to any of the preceding claims, wherein the thinning (134) reduces a thickness of the first flask (114a) by at least 50%.

7. The planet carrier (110) according to one of the preceding claims, wherein each of the first orifices (124a) has an internal diameter (H1) which is smaller than the internal diameter (H2) of each of the second orifices (124b).

8. The planet carrier (110) according to any of the preceding claims, wherein said shaft portion (115) comprises an external toothing (115a).

9. A mechanical gearbox (6) for an aircraft turbomachine, this gearbox comprising a planet carrier (110) according to one of claims 1 to 8, planet gears (8) which are housed in said housings (118) and which are guided by bearings (126) whose axial ends are engaged in said first and second orifices (124a, 124b), and a sun gear (7) which is housed in the cage and which is meshed with the planet gears (8).

10. An aircraft turbomachine (1) comprising a planet carrier (110) according to one of claims 1 to 8 or a gearbox (6) according to claim 9.