TURBOMACHINE COMPRISING A SPEED REDUCER HAVING MOUNTING FLANGES COUPLED BY A GEARED COUPLING.

Abstract

The invention comprises a speed reducer for an aircraft turbomachine (1) with longitudinal axis X, the speed reducer comprising an outer ring gear (24) and a ring carrier (26) fixed to the outer ring gear (24) which has a first mounting flange (25) extending radially outwards and fixed to a second mounting flange (27) of the ring carrier by means of fasteners (40). According to the invention, the turbomachine comprises an axial toothed coupling comprising a first set of teeth (29, 47) engaging with a second set of complementary teeth (32, 44), a portion of the first mounting flange comprising a portion of the toothed coupling, the fasteners being arranged to clamp the first and second mounting flanges and circumferentially hold each axial tooth of the first set of teeth between two axial teeth (29, 32) of the second set of complementary teeth.Figure for the abbreviation: Figure 4.

Description

Title of the invention: TURBOMACHINE COMPRISING A SPEED REDUCER HAVING FLANGES OF FIXINGS COUPLED BY A GEARED COUPLING. Scope of the invention

[0001] The present invention relates to the general field of aeronautics. It relates in particular to a mechanical speed reducer with mounting flanges coupled at least by a toothed coupling. Technical background

[0002] 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.

[0003] 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.

[0004] 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 X of the turbomachine. The planet gears each have a different axis of revolution and are equally spaced on the same operating diameter around the axis of the planetary gears. These axes are parallel to the longitudinal axis X.

[0005] 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. • 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 sun. • On an epicyclic reducer, the ring is fixed and the planet carrier constitutes the output shaft of the device which rotates in the same direction as the sun. • On a differential gearbox, no element is fixed in rotation. The ring rotates in the opposite direction to the solar and satellite carrier.

[0006] Reducers can be composed of one or more gear stages. This The meshing is ensured in different ways such as by contact, by friction or even by magnetic fields.

[0007] There are several types of contact meshing such as with straight, helical or chevron teeth.

[0008] Figure 1 shows a speed reducer IA with an epicyclic gear. The speed reducer IA comprises a fixed ring gear 2A connected to a fixed housing or stator 3A of the turbomachine via a ring carrier 4A. The speed reducer IA includes planet gears 5A that drive a planet carrier 6A. The latter is fixed to the fan shaft and is free to rotate about the longitudinal axis of the turbomachine. The ring gear 2A includes a first mounting flange 7A extending radially outwards and fixed to a second mounting flange 8A of the ring carrier 4A by means of a bolted connection. The mounting flanges 7A and 8A each comprise a surface, and these surfaces are pressed together by the bolts 9A of the bolted connection.

[0009] Torque transmission is achieved by friction between these surfaces and is limited to the same mounting diameter. Increasing the diameter of the mounting flanges could be a solution to increase torque transmission capacity. However, on the one hand, the number of screws that can be mounted on these flanges may be limited, and on the other hand, this could directly impact the diameter of the speed reducer and its integration into the already limited space of the turbomachine. Furthermore, the 4A sprocket carrier has a gooseneck that may obstruct access to the bolts of the bolted connection.

[0010] Furthermore, the crown carrier may include bellows to center the crown and to connect the crown 2A to the housing in such a way as to limit overloads due to the movement and misalignment of various components in the turbomachine. The crown carrier is therefore complex to manufacture and assembly can be tedious.

[0011] There is a need to resolve all or part of the aforementioned drawbacks. Summary of the invention

[0012] The objective of the present invention is to provide a simple and economical solution for increasing the transmission capacity of torque to the stator of the turbomachine.

[0013] We achieve this objective in accordance with the invention by means of a speed reducer for a turbomachine, in particular for aircraft, having a longitudinal axis X, the speed reducer comprising a sun pinion, planet gears, an outer ring gear, and a ring carrier fixed to the outer ring gear, the planet gears meshing on one side with the sun pinion and on the other with the outer ring gear, and the outer ring gear having a first mounting flange extending radially outwards and being fixed to a second mounting flange of the crown carrier by fastening elements, the first fastening flange and the second fastening flange forming a fastening assembly and in that the fastening assembly includes at least one coupling with axial teeth comprising a first series of axial coupling teeth intended to engage with a second series of complementary axial coupling teeth, the fastening elements being arranged so as to clamp the first and second fastening flanges together and to circumferentially hold each tooth of the first series of axial coupling teeth between two teeth of the second series of complementary axial coupling teeth.

[0014] Thus, this solution makes it possible to achieve the aforementioned objective. In particular, this coupling allows for a significant torque transfer (an increase of approximately 50%) over large average diameters. The torque transfer is achieved through friction between the teeth, which provide larger contact surfaces. Furthermore, the fastening of the mounting flanges by fasteners allows for the application of the axial force required in this type of coupling to press at least the two mounting flanges together. The toothed coupling allows for a reduction in fasteners of approximately 90%, resulting in a weight saving and simplified assembly. The reliability of such a configuration is increased.

[0015] The speed reducer also includes one or more of the following features, taken alone or in combination:

[0016] - the outer crown is formed of a front half-crown and a rear half-crown rear, the front half-crown comprising a front radial half-flange and the rear half-crown comprising a rear radial half-flange, the front radial half-flange and the rear radial half-flange forming the first fixing flange, the rear radial half-flange of the rear half-crown being connected to the second fixing flange by a toothed coupling by axial coupling teeth, the rear radial half-flange of the rear half-crown comprising the first set of axial coupling teeth and the second fixing flange comprising the second set of complementary axial coupling teeth.

[0017] - the outer crown is formed of a front half-crown and a rear half-crown rear, the front half-crown comprising a front radial half-flange and the rear half-crown comprising a rear radial half-flange, the front radial half-flange and the rear radial half-flange forming the first fixing flange, the front and rear radial half-flanges being connected to each other by a coupling with axial teeth, one of the front and rear radial half-flanges comprising the first set of axial coupling teeth and the other of the front and rear radial flanges comprising the second set of complementary axial coupling teeth.

[0018] - the first fixing flange and the second fixing flange comprise respec tivement of the first and second axial fixing orifices through which the fixing members pass, the first and second axial fixing orifices being arranged circumferentially around the longitudinal axis.

[0019] - the fastening elements include axial screws or axial bolts passing through the first and second fixing holes.

[0020] - several teeth of the first or second series of axial coupling teeth are arranged between two first or second circumferentially adjacent fixing holes around the longitudinal axis, the number of first or second fixing holes being between 5 and 10.

[0021] - the crown holder includes a bellows.

[0022] - the first flange and the second flange each comprise axial teeth of fixings which are traversed by fixing holes intended to receive fixing elements.

[0023] - the axial fixing teeth have, on the one hand, a tooth height measured ra- dialement vis-à-vis the longitudinal axis, and on the other hand, a tooth width measured in a transverse direction to the tooth height, the width of each of the axial fixing teeth being greater than the tooth width of the axial coupling teeth.

[0024] - the axial coupling teeth extend over the entire radial height of the first and second fixing brackets.

[0025] - one of the front and rear half-crowns comprises a leg extending along the longitudinal axis and intended to be housed in a recess of complementary shape to the other of the front and rear half-crowns.

[0026] - - the ring is connected to a housing of the turbomachine and is fixed in rotation relative to the longitudinal axis,

[0027] — the ring is connected to a shaft of the turbomachine and is rotationally mobile around the longitudinal axis.

[0028] The invention also relates to a turbomachine, in particular for aircraft, having a longitudinal axis X and a speed reducer as above.

[0029] The invention further relates to an aircraft equipped with such a turbomachine. Brief description of the figures

[0030] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent upon reading the following detailed explanatory description, of embodiments of the invention given by way of purely illustrative and non-limiting examples, with reference to the accompanying schematic drawings in which:

[0031] Figure [1] represents a mechanical reducer of a turbomachine according to art previous;

[0032] Figure [Fig.2] represents an example of a turbomachine according to the invention;

[0033] Fig. 3 is a detailed view of an example of a speed reducer according to the invention;

[0034] Figure 4 shows, in perspective, an example of coupling between two organs of a speed reducer according to the invention;

[0035] Fig. 5 is a perspective view of an example of a crown according to the invention;

[0036] Figure 6 is a perspective view of an example of a crown holder according to the invention;

[0037] Figure 7 is an axial cross-sectional view at the level of a toothed coupling between a crown and a crown holder according to the invention;

[0038] The [Fig.8] is an axial cross-sectional view at the level of a bolted connection between a crown and a crown carrier according to the invention;

[0039] Figure [Fig. 9] is a perspective view of another embodiment of an ac toothed coupling between flanges of a component of a speed reducer according to the invention;

[0040] Fig. 10 is a perspective and detail view of Fig. 9;

[0041] Figure 11 is an axial cross-sectional view of another embodiment of an ac coupling between two speed reduction elements and the turbomachine according to the invention;

[0042] Fig. 12 represents in perspective the engagement of the teeth of the coupling according to Fig. 11;

[0043] [Fig.13] is a perspective and detail view of [Fig.12]. Detailed description of the invention

[0044] Fig. 1 shows an axial cross-sectional view of a mechanical speed reducer intended to equip a turbomachine and which has already been described previously.

[0045] Figure 2 represents a turbomachine 1 with longitudinal axis X. The turbomachine 1 The illustrated example is a twin-flow turbomachine intended for mounting on an aircraft. Of course, the turbomachine could be a single-flow turbojet or a turboprop equipped with a single unfaired propeller or a pair of counter-rotating, unfaired propellers, known as an "open rotor." The invention may be applicable to other fields in which a mechanical speed reducer is used.

[0046] In the present invention, the terms "upstream" and "downstream" are defined with respect to the gas flow in the turbomachine and here along the longitudinal axis X and to the [Fig.1] from left to right.

[0047] The turbomachine 1 comprises, in a conventional manner and from upstream to downstream, a A blower S, a low-pressure compressor 1a, a high-pressure compressor 1b, an annular combustion chamber 2, a high-pressure turbine 3a, a low-pressure turbine 3b, and an exhaust nozzle 4. The high-pressure compressor 1b and the high-pressure turbine 3a are connected by a high-pressure shaft 5 and together form a high-pressure (HP) unit. The low-pressure compressor 1a and the low-pressure turbine 3b are connected by a low-pressure shaft 6 and together form a low-pressure (LP) unit.

[0048] The blower S is enclosed by a blower housing 7 carried by an external nacelle 8. The blower S generates, from an airflow F entering the blower, a primary airflow which flows in a primary channel 9 opening into the exhaust nozzle 4 and a secondary airflow which flows in a secondary channel 10, around the primary channel 9, opening into an ejection nozzle 11.

[0049] The blower S is driven by a blower shaft 12 which is driven to the low pressure shaft 6 for example by means of a reducer 20. The latter is generally of the planetary or epicycloidal type.

[0050] In the present embodiment, the turbomachine is equipped with a speed reducer 20 formed of a gear train and known by the English acronym RGB for "Reduction Gear Box".

[0051] The gearbox 20 is positioned in the upstream part of the turbomachine, following the flow of the turbomachine's gases. A fixed structure 13, schematically comprising an upstream part 13a and a downstream part 13b, forms the motor housing 16 or stator and is arranged to form an enclosure 14 surrounding the gearbox 20. The motor housing 16 can, for example, be the inlet housing of the turbomachine. A lubricant mist is present in the enclosure 14. This enclosure 14 is advantageously, but not exclusively, closed upstream by seals at an upstream bearing 15 allowing passage of the fan shaft 12, and downstream by seals at the point where the low-pressure shaft 6 passes through.

[0052] With reference to [Fig. 3], the speed reducer 20 is here of the epicyclic type. It comprises three components: a sun gear 21, planet gears 22, and a planet carrier 23, which are rotatable. The rotational speed of one of these components depends, in particular, on the difference in speeds between the other two components.

[0053] At the input, the reducer 20 is connected to the low-pressure shaft 6, for example, via splines 39. These splines advantageously extend parallel to the longitudinal axis X. Thus, the low-pressure shaft 6 drives the solar 21 (or internal planetary gear). Conventionally, the solar 21, whose axis of rotation coincides with that of the longitudinal axis X of the turbomachine, drives the satellites 22, which are evenly distributed over the same diameter around the longitudinal axis of rotation. X. This diameter is equal to twice the operating center-to-center distance between the solar array and the satellites. The number of satellites is generally defined as between three and seven for this type of application.

[0054] Advantageously, the solar 21 is rotationally fixed to the low pressure shaft 6 and the satellite carrier 23 is rotationally fixed to the blower shaft 12.

[0055] The set of satellites 22 is held by a frame called a satellite carrier 23. Each satellite 22 rotates around its own axis. Each satellite 22 meshes with an external ring gear 24 (or external planetary gear).

[0056] The outer ring 24 is fixed or immobile in rotation with respect to the longitudinal axis X.

[0057] At the output, the set of satellites 22 drives the planet carrier 23 in rotation around the X-axis of the turbomachine. The outer ring 24 is fixed to a housing of the turbomachine or stator (such as the housing 16) via a ring carrier 26 described later. The planet carrier is fixed and rotationally fixed to the fan shaft 12.

[0058] According to an alternative not shown, the speed reducer 20 comprises a planetary gear. In this case, the input of the speed reducer 20 is coupled to the low-pressure shaft 6, while the output of the speed reducer 20 is coupled to the blower shaft 12. In particular, the outer ring gear 24 is rotationally fixed to the blower shaft 12 about the longitudinal axis X. The planet gears, for example five in number, are carried by the planet carrier 23, which in this case is fixedly mounted. The planet carrier 23 is fixed to the housing 16. Thus, each of the planet gears 22 has teeth that mesh with those of the sun pinion 21, in the form of a gear wheel, and with the outer ring gear 24, which has internal teeth. In operation, the solar pinion 21 is driven in rotation by the low pressure shaft 6 according to a first rotation speed.The satellites 22 are driven in rotation by the solar pinion 21 around their axis at a second rotational speed. The outer ring 24, which meshes with the satellites 22, is driven in rotation around the longitudinal axis X and drives the blower shaft 12. The outer ring 24 rotates at a third rotational speed and in a direction opposite to that of the solar pinion 21.

[0059] In the case of a planetary or epicyclic gearbox, each planet 22 is mounted to rotate freely by means of a bearing (not shown), for example, a roller bearing or hydrodynamic bearing. Generally, a hydrodynamic bearing is supplied with "low" pressures (usually less than 10 bar). The rotation of the bearing allows the oil wedge to be pressurized and the planets and bearings to separate. Each bearing is mounted on one of the shafts of the planet carrier 23, and all the shafts are positioned relative to each other by means of one or more structural frames of the satellite carrier 23. Each satellite 22 meshes with external teeth of the solar 21 and internal teeth of the outer ring 24. The internal teeth of the outer ring 24 can be straight (parallel to the longitudinal axis), helical or chevron.

[0060] There is a number of shafts and bearings equal to the number of satellites. For reasons of operation, assembly, manufacturing, control, repair or replacement, the shafts and the chassis may be separated into several parts.

[0061] For the same reasons mentioned above, the teeth of a reducer 20 can be separated into several helices.

[0062] Still referring to [Fig.3], the outer ring 24 is separated into two half-rings 24a, 24b: • A front half-crown 24a consisting of a rim 24aa and a front radial mounting half-flange 24ab. The front helix of the reduction gear teeth is located on the rim 24aa. This front helix meshes with that of the satellite 22, which meshes with that of the solar 21. • A rear half-crown 24b consisting of a rim 24ba and a rear radial mounting half-flange 24bb. The rear helix of the reduction gear teeth is located on the rim. This rear helix meshes with that of the satellite 22, which meshes with that of the solar 21.

[0063] The mounting half-flange 24ab of the front half-crown 24a and the mounting half-flange 24b of the rear half-crown 24b form a first mounting flange 25 of the crown. The mounting flange 25 is annular and is oriented radially outwards.

[0064] Of course, the outer ring 24 can be formed in one piece. In this case, the outer ring 24 comprises a (single) first annular fixing flange 25 which extends radially outwards.

[0065] The outer ring 24 of the planetary type reducer 20 can have this same configuration in two half-rings or be formed from a single piece (made of material).

[0066] With further reference to [Fig. 3], a ring carrier 26 connects the outer ring 24 to the housing 16 of the turbomachine. The ring carrier 26 transfers the torque from the speed reducer 20 to the turbomachine housing. Advantageously, the ring carrier 26 is annular and centered on the axis of the turbomachine. To this end, the ring carrier 26 includes at a first end 26a a second mounting flange 27. In this example, the latter extends radially inward. Alternatively, the second mounting flange 27 of the ring carrier 26 extends radially outward.

[0067] The crown carrier 26 advantageously comprises at a second end 26b a connecting flange 43 which is intended to be fixed to a stator fixing part (such as the housing 16) of the turbomachine.

[0068] Advantageously, the gear carrier 26 includes flexible means 28 configured to, on the one hand, limit overloads in the turbomachine due to the movement of certain components thereof and / or the speed reducer 20, and on the other hand, obtain a uniform and stable distribution of dynamic loads. In the present example, the flexible means 28 include at least one bellows. The gear carrier 26 includes a portion equipped with several bellows.

[0069] With reference to Figures 4, 5, and 6, the first mounting flange 25 of the crown 24 cooperates with the second mounting flange 27 of the crown carrier 26. The first mounting flange 25 and the second mounting flange 27 form a fastening assembly. Advantageously, the mounting flange 27 of the crown carrier 26 and the mounting flange 25 of the crown 24 are coupled to each other by a curvic coupling. Such a configuration offers, on the one hand, a greater load-bearing capacity than flanges that are screwed on, and on the other hand, a weight reduction by reducing the number of fastening means.

[0070] The "curvic coupling" type toothed coupling is applicable between the flanges of the fixed parts, namely the ring 24 and the ring carrier 26 of the epicyclic type speed reducer, but also between the flanges of the moving parts, namely the ring 24 and the ring carrier 26 of the planetary type speed reducer.

[0071] The gear coupling must take into account the forces to be transmitted, the evacuation of lubricant from the speed reducer generally located at the flange of the ring gear 24, and the attachment of the flanges of one or more components of the reducer or turbomachine. More specifically, there must be sufficient teeth for the transmission of forces while leaving space for the bores or holes intended for the evacuation of lubricant and the fastening elements between the parts.

[0072] With reference to [Fig. 5], the ring (or two half-rings) 24 comprises a revolution axis A which is coaxial with the axis of the turbomachine. The first mounting flange 25 extends radially from a radially external surface 24c. The opposite internal radial surface comprises helices 35 which mesh with the teeth of the satellites 22.

[0073] With reference to Figures 4 to 6, the first mounting flange 25 of the crown 24 comprises a first set of teeth 29 (visible more precisely in [Fig. 4]). Following the illustrated example, the teeth 29 are evenly distributed around the longitudinal axis X. As can also be seen in this example, the teeth 29 extend along the longitudinal axis projecting from a first radial face 30 of the first mounting flange 25. In particular, in the case of the two half-crowns, the mounting half-flange 24bb comprises the first radial face 30 provided with the teeth 29. The first radial face 30 delimits the bottom of the hollows located between each tooth 29.

[0074] Advantageously, but not exclusively, each axial coupling tooth 29 extends radially along the entire height of the first mounting flange 25. Advantageously, the teeth 29 are straight. Of course, the teeth 29 could have another shape, such as, for example, trapezoidal.

[0075] Advantageously, but not exclusively, the first mounting flange 25 comprises holes 31, each having an axis parallel to the longitudinal axis. The holes 31 are regularly spaced around the longitudinal axis. The number of holes is less than the number of teeth 29. The holes 31 are arranged between a predetermined number of teeth 29. According to an advantageous feature, the number of holes is between 5 and 10. In the illustrated example, there are seven holes 31 positioned between seven sets of teeth. For example, there are fourteen teeth in each set of teeth 29.

[0076] With reference to [Fig. 6], the second mounting flange 27 of the crown carrier 26 comprises a second set of axial coupling teeth 32 complementary to the first set of teeth 29. The teeth 29 and complementary teeth 32 are oriented opposite each other. The teeth are specifically designed to engage with each other. In this way, the complementary teeth 32 are arranged around the longitudinal axis and extend axially outward from a radial face 33 of the second mounting flange 27 of the crown carrier 26. In other words, the teeth 29 and complementary teeth 32 extend along the longitudinal axis (they are axial teeth). The complementary teeth 32 also extend over the entire height of the second mounting flange 27.

[0077] The teeth and complementary teeth 32 are arranged in contact with each other to transmit a torque to the stator of the turbomachine (in the case where the speed reducer is epicyclic).

[0078] On [Fig.4] in particular, in the present example, each tooth 29 and complete tooth The element 32 comprises two sections 34a, 34b extending along the longitudinal axis and in contact with each other. The sections 34a, 34b are connected by a face 34c defined in a plane perpendicular to the longitudinal axis. The sections 34a, 34b have the same length along the longitudinal axis in this example.

[0079] As can also be seen in Figures 4 and 6, the second mounting flange 27 of the crown carrier 26 includes second holes 36 which pass through its wall on either side along the longitudinal axis. The axial second holes 36 are intended to cooperate with the first holes 31 of the crown 24. In the installed position, the first and second holes 31, 36 are opposite each other. The number of second holes is identical to the number of first holes. 31.

[0080] According to yet another advantageous feature, each orifice 36 passes through a retaining tooth 48 as illustrated precisely in [Fig. 6]. The first and / or second retaining flange(s) 25, 27 comprise retaining teeth 48. The retaining teeth 48 are evenly distributed around the longitudinal axis X. Each retaining tooth has a tooth height measured radially with respect to the longitudinal axis. Each retaining tooth 48 has a circumferential width that is greater than that of the complementary coupling teeth 32. In other words, the width of the retaining tooth is measured transversely to the tooth height. The width of each retaining tooth 48 is adapted according to the dimensions of the retaining members described below.The fixing teeth can be received in recesses of complementary shape and formed in either of the first and second fixing flanges.

[0081] The first and second openings 31, 36 are designed to allow the passage of fasteners 40. In other words, the first and second axial openings 31, 36 are traversed by the fasteners 40. The fasteners 40 are advantageously, but not exclusively, threaded elements of the screw-nut type. Of course, the fasteners 40 can be any threaded element cooperating with a clamping element or any other suitable element that allows for easy assembly and disassembly without damage to the parts fitted thereto.

[0082] The fastening members 40 are arranged to clamp the first and second flanges 25, 27 and to circumferentially hold each axial tooth of the first set of teeth between axial teeth of the second set of complementary teeth. Advantageously, the fastening members 40 comprise screws 41 that extend axially and apply an axial force to clamp the two fastening flanges and engage the teeth.

[0083] The screws 41 each extend between adjacent complementary teeth 29, 32 in the circumferential direction.

[0084] In [Fig.7] we see that face 34c of a tooth from the first series of the The first fixing flange 25 is in contact with the first radial face 30 of the second fixing flange 27. We also see that the radial height of the second fixing flange 27 is equal to the radial height of the first fixing flange 25. In a limiting manner, the second fixing flange 27 has a height greater than that of the first fixing flange.

[0085] Still on [Fig. 7], the half-crown 24b includes a leg 37 that extends parallel to the longitudinal axis X. In the present example, the leg 37 is annular. This leg is nested in a correspondingly shaped recess 38 formed in the front half-crown 24a. The recess 38 is made at the level of a ra- The internal radial surface 24da of the front half-crown 24a is oriented towards the longitudinal axis. Advantageously, the recess 38 has a height approximately (plus or minus 10 mm) equal to the height of the tab 37. The height is measured along the radial axis. Advantageously, the internal radial surface 24da has a continuous surface with an internal radial surface 24db of the rear half-crown 24b (and of the tab 37). This facilitates the assembly of the half-crowns and ensures their correct positioning relative to each other. Alternatively, the recess 38 can be formed at the level of the internal radial surface 24db of the rear half-crown 24b and the tab carried by the front half-crown 24a.

[0086] In [Fig.8] we see a screw 41 (in dashed line) which passes through the first and second holes 31, 36 respectively of the first and second fixing flanges 25, 27. The head 41a of the screw is pressed against a downstream face 49 (opposite to the radial face 30) of the second fixing flange 27. A nut 42 (shown in dashed line) enabling the screw to tighten the flanges 25, 27 is mounted on the threaded shank of the screw 41 on the side of the first fixing flange 25.

[0087] The number of fastening elements 40 is identical to the number of the first and second holes, respectively. With the toothed coupling, it is not necessary to have a large number of screws that could increase the mass of the assembly. Compared to conventional prior art fastening flanges secured with numerous screws, the toothed coupling reduces the number of screws required by approximately 90%.

[0088] For assembly, simply engage the teeth 29 and complementary teeth 32 of the two flanges and fix the flanges 25, 27 with the screws 41 and nuts 42. The screws remain easily accessible for disassembly and assembly as there are no additional parts covering them.

[0089] Figures 9 to 10 illustrate an embodiment of the arrangement of a toothed coupling. This embodiment differs from that previously presented in that the toothed coupling with axial coupling teeth is arranged between the two half-flanges 24ab, 24bb of the outer ring 24. The rear half-flange 24bb comprises a first series of axial coupling teeth, hereinafter referred to as internal teeth 44, which extend from a first internal face 45 along the longitudinal axis X. The first internal face 45 extends in a radial plane. The first internal face 45 is opposite a second internal face 46 of the front half-flange 24ab. The front half-flange 24ab comprises a second series of complementary axial coupling teeth, referred to as complementary internal teeth 47 to the internal teeth 44, which extend from the second internal face 46.Of course, the front half bridle 24ab can include the teeth and the rear half bridle 24bb can include the teeth. complementary. The internal teeth 44 and complementary internal teeth 47 can extend over the entire height or part of the height of the flanges. As in the first embodiment, on the one hand the internal teeth 44 engage between the complementary teeth 47 so as to create a coupling with axial teeth and on the other hand the fastening members 40 allow the front and rear half-flanges 24ab, 24bb to be clamped and each internal tooth 44 to be circumferentially held between complementary teeth 47.

[0090] Advantageously, the internal teeth 44 and complementary internal teeth 47 are straight, but they could be trapezoidal in shape. In this embodiment, the mounting flange 27 is toothless. We understand that the radial face 33 of the second mounting flange 27 is substantially flat and / or smooth.

[0091] Such a configuration offers increased force transfer between the ring flanges and allows the ring diameter to be kept to a minimum, thus avoiding impacting the mass of the speed reducer. It should be noted that the teeth facilitate the assembly of the two ring halves, and in particular the flange halves, because the teeth interlock naturally. This toothed coupling is also more reliable and extends the ring's service life by reducing friction.

[0092] Figures 11 to 13 illustrate yet another embodiment of the arrangement of at least one geared coupling with axial coupling teeth comprising a first series of axial coupling teeth intended to engage with a second series of complementary axial coupling teeth. In this embodiment, there is a geared coupling between the half-flanges 24ab, 24bb of the crown 24 and a geared coupling between the flange of the crown 24 and the mounting flange 27 of the crown carrier 26. In particular, the second mounting flange 27 comprises the complementary teeth 32 which engage between the teeth 29 of the rear half-flange 24bb of the crown 24 and the internal teeth 44 of the half-flange 24bb engage between the complementary internal teeth 47 of the half-flange 24ab. Such a configuration allows for the multiplication of the forces that pass between the different flanges.It is possible to increase torque transmission capacity without affecting the diameter of the individual components. The coupling between the crown gear and the crown gear holder is also more reliable (less friction and less wear).

Claims

Demands

1. Speed ​​reducer (20) for a turbomachine (1), in particular for aircraft, having a longitudinal axis X, the speed reducer comprising a sun pinion (21), planet gears (22), an outer ring gear (24) and a ring carrier fixed to the outer ring gear (24), the planet gears (22) meshing on one side with the sun pinion (21) and on the other side with the outer ring gear (24), and the outer ring gear (24) having a first mounting flange (25) extending radially outwards and being fixed to a second mounting flange (27) of the ring carrier (26) by fastening members (40), the first mounting flange (25) and the second mounting flange (27) forming a fastening assembly characterized in that the fastening assembly comprises at least one coupling with axial coupling teeth comprising a first series of axial coupling teeth (29, 44,47) engaging with a second series of complementary axial coupling teeth (32, 47, 44), the fastening members (40) being arranged so as to clamp the first and second fastening flanges (25, 27) together and to circumferentially hold each tooth of the first series of axial coupling teeth (32) between two teeth of the second series of complementary axial coupling teeth (44).

2. Speed ​​reducer (20) according to claim 1, characterized in that the outer ring (24) is formed of a front half-ring (24a) and a rear half-ring (24b), the front half-ring (24a) comprising a front radial half-flange (24ab) and the rear half-ring (24b) comprising a rear radial half-flange (24bb), the front radial half-flange (24ab) and the rear radial half-flange (24bb) forming the first mounting flange (25), the rear radial half-flange (24bb) of the rear half-ring (24b) being connected to the second mounting flange (27) by a gear coupling with axial coupling teeth, the rear radial half-flange (24bb) of the rear half-ring (24b) comprising the first set of axial coupling teeth (29) and the second flange of attachment (27) comprising the second series of complementary axial coupling teeth (32).

3. Speed ​​reducer (20) according to any one of the preceding claims, characterized in that the outer ring (24) is formed of a front half-ring (24a) and a rear half-ring (24b), the half- front crown (24a) comprising a front radial half-flange (24ab) and the rear half-crown (24b) comprising a rear radial half-flange (24bb), the front radial half-flange (24ab) and the rear radial half-flange (24bb) forming the first fixing flange (25), the front and rear radial half-flanges (24ab, 24bb) being connected to each other by a coupling with axial teeth, one of the front and rear radial half-flanges (24ab, 24bb) comprising the first series of axial coupling teeth (44, 47) and the other of the front and rear radial flanges (24ab, 24bb) comprising the second series of complementary axial coupling teeth (44, 47).

4. Speed ​​reducer (20) according to any one of the preceding claims, characterized in that the first mounting flange (25) and the second mounting flange (27) respectively comprise first and second axial mounting holes (31, 36) through which the fastening members (40) pass, the first and second axial mounting holes (31, 36) being arranged circumferentially around the longitudinal axis V

5. A. Speed ​​reducer (20) according to the preceding claim, characterized in that the fastening members (40) comprise axial screws (41) or axial bolts passing through the first and second fastening holes (31, 36).

6. Speed ​​reducer (20) according to claim 4 or 5, characterized in that several teeth of the first or second series of axial coupling teeth (32, 44) are arranged between two first or second mounting holes (31, 36) circumferentially adjacent around the longitudinal axis X, the number of first or second mounting holes (31, 36) being between 5 and 10.

7. Speed ​​reducer (20) according to any one of the preceding claims, characterized in that the crown carrier (26) includes a bellows.

8. Speed ​​reducer (20) according to any one of the preceding claims, characterized in that the first flange (25) and the second flange (27) each comprise axial fixing teeth (48) which are traversed by fixing orifices (31, 36) receiving fixing members (40).

9. Speed ​​reducer (20) according to the preceding claim, characterized in that the axial fixing teeth (48) have, on the one hand, a tooth height measured radially with respect to the longitudinal axis X, and on the other hand, a tooth width measured in a direction transverse to the tooth height, the width of each of the axial fixing teeth being greater than the tooth width of the axial coupling teeth (32, 44).

10. Speed ​​reducer (20) according to any one of the preceding claims, characterized in that the axial coupling teeth (29, 32, 44, 47) extend over the entire radial height of the first and second fixing flanges (25, 27).

11. Speed ​​reducer (20) according to claim 2 or 3 or any one of claims 4 to 10 when dependent on claims 2 or 3, characterized in that one of the front and rear half-rings (24a, 24b) comprises a lug (37) extending along the longitudinal axis and housed in a recess (38) of complementary shape to the other of the front and rear half-rings (24a, 24b).

12. Turbomachine (1), in particular for aircraft, having a longitudinal axis X, and comprising a speed reducer (20) according to any one of the preceding claims.

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