MECHANICAL REDUCER FOR A TURBOMACHINE

Abstract

The invention relates to a mechanical gearbox comprising a sun gear, a ring gear, sun gears, and a ring carrier. The sun gear is one component of the gearbox, along with the ring gear and the ring carrier. Another annular element comprises a primary flange (B1) for attachment to a secondary flange (B2) of the other component of the gearbox by means of screws. The primary flange includes first bearing faces (B10) configured to bear against corresponding second bearing faces (B20) of the secondary flange, and first ramp faces (B12) configured to bear against second ramp faces (B22) of the secondary flange. A torque transmitted by the ring gear in a second direction (D2) causes an axial separation of the flanges (B1, B2) from each other and a tensile force on screws configured to break when this tensile force exceeds a predetermined threshold. Figure 12b is shown in the abstract.

Description

Title of the invention: MECHANICAL REDUCER FOR A TURBOMACHINE Scope of the invention

[0001] The present invention relates to the field of mechanical reducers for a turbomachine in particular of aircraft, as well as a turbomachine comprising such a mechanical reducer. 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 meshing stages. This meshing is achieved in various ways such as by contact, by friction or by magnetic fields.

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

[0008] During operation, a failure of a satellite bearing (hydrodynamic or roller type) can cause the gearbox and fan to seize. This can lead to an increase in turbomachine drag and impair aircraft maneuverability.

[0009] To prevent such a blockage of the gearbox, it was proposed in document FRAI-3 066 004 to form the ring gear from two half-rings, the ring gear being designed to disengage from the planet gear when the planet gear exerts a disengagement force on each half-ring gear with an amplitude exceeding a predetermined value. To this end, this document proposes integrating a fusible thrust bearing connected both to the ring carrier and to one of the half-ring gears designed to break under the disengagement force, the amplitude of which corresponds to a blockage of a turbomachine component (such as a planet gear bearing blockage) and the axial force applied to the ring gear is directed outwards from the gearbox. However, this design can be complex to implement, particularly due to the additional components that must be assembled within the gearbox.

[0010] In this context, it is interesting to overcome the disadvantages of the prior art, by proposing a solution allowing the rotation of a blower to be maintained during a blockage of a mechanical reducer of a turbomachine (resulting for example from a failure of a satellite bearing or of a satellite for example). Summary of the invention

[0011] The present invention proposes a simple and economical solution to at least some of the aforementioned problems.

[0012] To this end, the invention relates to a mechanical gearbox for a turbomachine, in particular for aircraft, this gearbox comprising: - a solar system having a first axis of rotation A, - a crown extending around the solar element and said first axis A, the crown comprising two annular half-crowns which are fixed to each other respectively by first and second annular flanges, - satellites which are arranged around the first axis A, between the solar system and the corona, and which are meshed with the solar system and the corona, these satellites each having a second axis B of rotation parallel to the first axis A and being held by a mobile satellite carrier rotating around said first axis A, - a crown carrier having a general annular shape around the first axis A, the crown carrier comprising a third annular flange for fixing to the first and second flanges, and a fourth annular flange for fixing to a fifth annular flange of another annular element extending around the first axis A, said first, second and third flanges being tightened axially against each other by first screws parallel to the first axis, and said fourth and fifth flanges being tightened axially against each other by second screws parallel to the first axis.

[0013] According to the invention, one of the flanges, called the primary flange, among the first, second and third flanges, or among the fourth and fifth flanges, comprises first bearing faces which are distributed around the first axis A and first ramp faces which are distributed around the first axis A,

[0014] the first bearing faces being configured to cooperate by tangential bearing with corresponding second bearing faces of another of said flanges, called secondary flange, which is axially supported against the primary flange, so as to transmit a torque transmitted by the ring in a first direction DI around the first axis A, and

[0015] the first ramp faces being configured to cooperate with second ramp faces of said secondary flange so that a torque transmitted by the crown in a second direction D2 around the first axis A, opposite to the first direction Dl, causes an axial separation of the flanges from each other and a tensile force on the first and / or second screws which are configured to break when this tensile force is greater than a predetermined threshold.

[0016] The invention thus proposes modifying the gear carrier to maintain the rotation of a turbomachine fan during a blockage of a gearbox component (for example, a satellite bearing or the satellite itself). To this end, the gear carrier incorporates first bearing faces cooperating with second bearing faces and first ramp faces cooperating with second ramp faces on the primary and secondary flanges.

[0017] Thus, in normal operation of the mechanical reducer, the first bearing and ramp faces are, on the one hand, in circumferential contact with their corresponding secondary bearing and ramp faces, and on the other hand, the primary and secondary flanges are axially tightened by screws. This maintains the connection between the primary and secondary flanges. Furthermore, this configuration allows the transmission of a torque from the ring gear along a first direction Dl around the first axis A.

[0018] In abnormal operation of the mechanical reducer (for example, in the event of failure of the satellite bearing(s) or the satellite itself), the bearing faces are in circumferential contact and the first and second ramp faces are able to move axially apart from each other (in particular by cam effect) when the torque transmitted by the ring gear exceeds a predetermined threshold and along a second direction D2 around the first axis A, opposite to the first direction D1. Indeed, the The direction of torque transmission from the crown gear to the crown gear carrier reverses, for example, during a planetary gear bearing failure. This reversal of the torque transmission direction generates additional stresses on the ramp faces, which in turn cause tensile forces on the screws. When these tensile forces exceed a predetermined threshold (for example, during a planetary gear bearing failure), they cause the ramp faces to separate axially and also break the screws, thus severing the connection between the primary and secondary flanges. This allows the primary and secondary flanges to be disconnected first. The rotation of the failed planetary gear(s) remains blocked.In this way, the solar power directly drives the satellite carrier and / or the corona through the blocked satellite(s), so that the fan (connected to the satellite carrier and / or the corona, for example, via a drive shaft) of the turbine can continue to rotate.

[0019] Consequently, in the event of a satellite blockage (for example, during a satellite bearing failure), the fan blockage is prevented. This limits the problems of turbomachine drag on the aircraft wings and the resulting impairment of aircraft maneuverability.

[0020] The first and second ramp faces thus provide a mechanical fuse function (in abnormal operation described above) while allowing a rigid system when the satellites are not blocked (in normal operation).

[0021] The mechanical reducer also includes one or more of the following features, taken alone or in combination:

[0022] - the primary flange comprises an annular row of first axial teeth which are axially engaged between second axial teeth of the secondary flange, to form a dog clutch connection between the primary and secondary flanges;

[0023] - the first and second axial teeth of each of the primary and secondary flanges are regularly distributed around said first axis A;

[0024] - the first and second axial teeth of each of the primary and secondary flanges are identical;

[0025] - first and second axial teeth of each of the primary and secondary flanges include respectively the said first and second support faces on a first side, and the said first and second ramp faces on a second side, opposite to the first side;

[0026] - each of the primary and secondary flanges comprises a number of teeth including between 25 and 50;

[0027] - the first and second axial teeth each have a generally parallel shape piped;

[0028] - the first axial teeth of the primary flange, respectively of the flange secondary, each include a radial face perpendicular to said first axis A and extending between the bearing face and the ramp face of this first tooth, this radial face being configured to bear axially between the second axial teeth of the secondary flange, respectively of the primary flange;

[0029] - the first and / or second screws pass through first orifices formed in the first teeth of the primary flange, respectively of the secondary flange, and of the second orifices formed between the second teeth of the secondary flange, respectively of the primary flange;

[0030] - each of the first and second ramp faces has an angle of inclination per relative to a plane passing through said first axis A, which is between 5° and 75°;

[0031] - the first and second axial teeth each have an extent around the first axis A which is between 5° and 10°;

[0032] - said first support faces are located in planes passing through the first axis A;

[0033] — the other annular element is a turbomachine stator or a drive shaft (such as a turbomachine blower shaft).

[0034] The invention further relates to a turbomachine, in particular for aircraft, comprising a mechanical reducer according to one of the features of the invention.

[0035] The invention further relates to an aircraft equipped with such a turbomachine. Brief description of the figures

[0036] 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:

[0037] Fig. 1 is a schematic half axial cross-sectional view of an example of a turbomachine according to the invention;

[0038] Figure 2 is a schematic half-view in axial cross-section of an example of a reducer epicycloidal type mechanics of the turbomachine of [Fig.1];

[0039] The [Fig.3] is a schematic half axial cross-sectional view of an example of a differential type mechanical reducer of the turbomachine of the [Fig.1];

[0040] Figure 4 schematically represents in perspective a primary flange and a flange secondary of the mechanical reducer of the [Fig.2] or 3;

[0041] Fig. 5 schematically represents an enlarged and perspective view of the primary flange of Fig. 4;

[0042] Figure 6 schematically represents an enlarged perspective view of the flange secondary of the [Fig.4];

[0043] Fig. 7 schematically represents a first example of a dog clutch connection between the primary and secondary flanges of the mechanical reducer of Fig. 2 or 3;

[0044] Fig. 8 schematically represents a second example of a dog clutch connection between the primary and secondary flanges of the mechanical reducer of Fig. 2 or 3;

[0045] Fig. 9 schematically represents a third example of a dog clutch connection between the primary and secondary flanges of the mechanical reducer of Fig. 2 or 3;

[0046] The [Fig. 10] is a schematic half view in axial section illustrating the different possibilities of dog clutch connection in the mechanical reducer of the [Fig.2];

[0047] Fig. 1a schematically represents normal operation of the mechanical reducer of Fig. 2 or 3;

[0048] The [Fig. 11b] schematically represents an abnormal operation of the mechanical reducer of the [Fig.2] or 3;

[0049] The [Fig. 12a] is a partial schematic axial cross-sectional view of a dog clutch connection between the primary and secondary flanges of the mechanical reducer of the [Fig.2] or 3, in normal operation;

[0050] Fig. 12b is a partial schematic axial cross-sectional view of the dog clutch link of Fig. 12a in abnormal operation.

[0051] Elements having the same functions in the different implementations have the same references in the figures. Detailed description of the invention

[0052] By convention, in the following description, the terms "longitudinal" and "axial" refer to the orientation of structural elements extending along a longitudinal axis (such as that of a turbomachine). The terms "radial" or "vertical" refer to the orientation of structural elements extending in a direction perpendicular to the longitudinal axis. The terms "interior" and "exterior," and "internal" and "external," are used with reference to positioning relative to the longitudinal axis. Thus, a structural element extending along the longitudinal axis has an interior face facing the longitudinal axis and an exterior surface opposite its interior surface.

[0053] Similarly, by convention in the present application, the terms "upstream" and "downstream" are defined with respect to the direction of gas flow in the turbomachine.

[0054] Fig. 1 shows a partial axial cross-sectional view of a turbomachine 1, in particular of an aircraft, with longitudinal axis X which includes a mechanical reducer 3.

[0055] The turbomachine 1 shown is a turbofan engine intended for mounting on an aircraft. Of course, the turbomachine could be a single-flow turbojet engine or a turboprop engine equipped with a single unfaired propeller or a A pair of counter-rotating, unfaired propellers, known by the English term "open rotor". The invention may be applied to other fields in which a mechanical speed reducer is used.

[0056] The turbomachine 1 comprises, in a conventional manner and from upstream to downstream, a fan S, a low-pressure compressor Ia, a high-pressure compressor 1b, an annular combustion chamber le, a high-pressure turbine Id, a low-pressure turbine le, and an exhaust nozzle If. The high-pressure compressor 1b and the high-pressure turbine Id are connected by a high-pressure shaft Ibd and together form a high-pressure (HP) housing. The low-pressure compressor Ia and the low-pressure turbine le are connected by a low-pressure shaft lae and together form a low-pressure (LP) housing.

[0057] The blower S is enclosed by a blower housing 2s carried by an external nacelle 2. The blower S generates, from an airflow F entering the blower, a primary airflow which flows in a primary vein VI opening into the exhaust nozzle If and a secondary airflow which flows in a secondary vein V2, around the primary vein VI, opening into an ejection nozzle 2f of the nacelle 2.

[0058] The blower S is driven by a blower shaft 1s which is driven to the low pressure shaft lae by means of a mechanical reducer 3. The mechanical reducer 3 can be of epicyclic or differential type.

[0059] In the present embodiment, the turbomachine 1 is equipped with the mechanical reducer 3 formed of a gear train and known by the English acronym RGB for "Reduction Gear Box".

[0060] The mechanical gearbox 3 is positioned in the upstream part of the turbomachine 1, following the flow of the turbomachine's gases. A fixed structure 4, schematically comprising an upstream part 4a and a downstream part 4b, forms a turbomachine stator 5 (or housing) and is arranged to form an enclosure 40 surrounding the mechanical gearbox 3. The stator 5 can, for example, be the turbomachine's inlet housing. A lubricant mist is present in the enclosure 40. This enclosure 40 is advantageously, but not exclusively, closed upstream by seals at an upstream bearing P allowing passage of the fan shaft 1s, and downstream by seals at the point where the low-pressure shaft 1e passes through.

[0061] With reference to [Fig. 2], the mechanical reducer 3 is here of the epicyclic type. It comprises three components: a sun gear 31, planet gears 32, and a planet carrier 33, which are rotatable. The rotational speed of one of these components depends, in particular, on the difference in speeds between the other two components.

[0062] At the input, the mechanical reducer is connected to the low-pressure shaft lae, for example via splines. Thus, the low-pressure shaft lae drives the solar 31 (or internal planetary gear). Typically, the solar 31, whose first axis of rotation A coincides with that of the longitudinal axis X of the turbomachine, drives the satellites 32, which are evenly distributed around the same diameter of the first A. This diameter is equal to twice the operating center distance between the solar and the satellites. The number of satellites is generally defined between three and seven for this type of application.

[0063] The solar 31 is rotationally fixed to the low pressure shaft lae and the satellite carrier 33 is rotationally fixed to the blower shaft 1s.

[0064] The set of satellites 32 is held by a frame called a satellite carrier 33. Each satellite 32 rotates around its own second axis of rotation B. Each second axis B is parallel to the first axis A. Each satellite 32 meshes with a ring 35 (or external planetary gear).

[0065] The crown 35 is preferably fixed or immobile in rotation with respect to the first axis A.

[0066] The mechanical reducer 3 may include an annular deflector 6 extending around the first axis A. This deflector 6 may be fixed to the ring 35 and configured to convey oil exiting radially to the outside of the ring by centrifugal effects.

[0067] At the output of the epicyclic reducer, the set of satellites 32 drives the planet carrier 33 in rotation around the first axis A. The ring 35 is fixed to the stator 5 via a ring carrier 36. The planet carrier 33 is fixed and rotationally fixed to the blower shaft 1s.

[0068] Although the preceding description relates to an epicycloidal type reducer, it also applies to a differential type reducer in which the three components (satellite carrier, crown and sun) are mobile in rotation, the rotational speed of one of these components depending in particular on the difference in speeds of the other two components.

[0069] Consequently, and alternatively, the mechanical reducer 3 can be of the differential type. In this case, the input of the mechanical reducer 3 of the turbomachine 1 of [Fig. 1] can be coupled to the low-pressure shaft 1ae, while the output of the mechanical reducer 3 can be coupled to the blower shaft 1s. In particular, at least one of the planet carrier 33 and / or the ring gear 35 is rotationally fixed to the blower shaft 1s about the first axis A.

[0070] In the operating differential mechanical reducer 3, the solar element 31 is driven by the low-pressure shaft lae at a first speed. The satellites 32 are driven in rotation by the solar element 31 around their second axis B at a second rotational speed.

[0071] Figure 3 illustrates a non-limiting configuration of the differential mechanical reducer 3, in which the set of satellites 32 drives the planet carrier 33 in rotation about the first axis A, which can be connected to a first component of the turbomachine. The planet carrier 33 rotates at a third speed. The ring gear 35 can be connected to the fan shaft 1s. The ring gear 35, which is meshed with the satellites 32, is driven in rotation about the first axis A and drives the fan shaft 1s. The ring gear 35 rotates at a fourth speed and in a direction opposite to that of the solar element 31.

[0072] In the case of the epicyclic or differential mechanical reducer 3, each planet 32 ​​is mounted to rotate freely by means of a bearing 34, 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 33, and all the shafts are positioned relative to each other by means of one or more structural frames of the planet carrier 33. Each planet 32 ​​meshes with external teeth of the sun gear 31 and internal teeth of the ring gear 35. The internal teeth of the ring gear 35 can be straight (parallel to the longitudinal axis) or herringbone.

[0073] 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.

[0074] For the same reasons mentioned above, the teeth of a reducer 3 can be separated into several helices.

[0075] Still referring to [Fig.2], the crown 35 is separated into two half-crowns 35a, 35b: - a semi-annular ring, called the "front" ring, 35a, consisting of a rim 35aa and a first annular mounting flange 35ab (hereafter referred to as the first flange). The front helix of the reduction gear teeth is located on the rim 35aa. This front helix meshes with that of the satellite 32, which meshes with that of the solar 31. - a semi-annular ring, called the "rear" ring, 35b, consisting of a rim 35bb and a second annular mounting flange 35ba (hereafter referred to as the second flange). The rear helix of the reduction gear teeth is located on the rim. This rear helix meshes with that of the satellite 32, which meshes with that of the solar 31.

[0076] The first 35ab and second 35ba flanges extend radially outwards.

[0077] In one embodiment (not illustrated), the first flange 35ab of the front ring and the second flange 35ba of the rear ring can form a single mounting flange 350 of the ring 35. This mounting flange 350 is annular and extends radially outwards.

[0078] With further reference to [Fig. 2] or [Fig. 3], the epicyclic or differential mechanical reducer 3 comprises a ring carrier 36. The ring carrier 36 is annular and centered on the first axis A. For this purpose, the ring carrier 36 includes a third annular mounting flange 362 (hereafter referred to as the third flange) for the ring gear 35, in particular for the second flange 35ba (or the mounting flange 350), using, for example, a bolted mounting. This third flange 362 can extend radially inward. Alternatively, the third flange 362 can extend radially outward. The ring carrier 36 includes a fourth annular mounting flange 364 (hereafter referred to as the fourth flange). This fourth flange 364 can extend radially outward. Alternatively, the fourth flange 364 extends radially inwards.

[0079] The crown holder 36 may include an annular portion 366 suitable for connecting the third bridle 362 and the fourth bridle 364. The third and fourth bridles 362, 364 and the annular portion may be one piece (i.e. made from a single piece of material).

[0080] Advantageously, the gear carrier 36 may include flexible means (not shown in the figures) configured to, on the one hand, limit the overloads in the turbomachine due to the movement of certain components thereof and / or of the mechanical gearbox 3, and on the other hand, obtain a uniform and stable distribution of the dynamic loads. The flexible means may include at least one bellows. The gear carrier 36 may include a portion equipped with several bellows.

[0081] With reference to [Fig. 2], the ring carrier 36 can connect the ring gear 35 to the stator 5 of the turbomachine, for example, in the configuration of the epicyclic mechanical gearbox 3. Thus, the fourth flange 364 can be designed to be fixed to an annular flange 50 for mounting the stator 5, for example, by means of a bolted assembly. The ring carrier 36 allows the torque from the mechanical gearbox 3 to be transferred to the stator 5 of the turbomachine.

[0082] With reference to [Fig.3], the crown carrier can connect the crown 35 to the blower shaft 1s. Thus, the fourth flange 364 can be intended to be fixed to an annular fixing flange of the blower shaft 1s, using a bolted mounting for example.

[0083] As an alternative to the mechanical reducer 3 of [Fig. 3], the ring carrier can connect the ring gear 35 to a second component of the turbomachine (not shown in the figures). The second component can be one of the upstream or downstream propellers of an unshrouded turbomachine. The fourth flange 364 can be designed to be fixed to an annular mounting flange of the second turbomachine component, for example by means of a bolted assembly.

[0084] The turbomachine stator 5, the fan shaft 1s and / or the second tur- The machine can generally correspond to an "other annular element" E of this application. Thus, the annular mounting flange(s) of the stator 5, the blower shaft 1s, and the second component form (or form) a fifth annular mounting flange(s) Eo (hereafter referred to as the fifth flange). In this way, the fourth flange 364 of the sprocket carrier 36 is connected to the fifth flange Eo of the other element E, for example, by means of a bolted assembly.

[0085] In the case of the epicyclic or differential mechanical reducer 3, the first 35ab, second 35ba and third 362 flanges are axially clamped against each other by first screws 72 parallel to the first axis A. The fourth 364 and fifth Eo flanges are axially clamped against each other by second screws 74 parallel to the first axis A.

[0086] The mechanical reducer 3 may comprise one or more flanges called primary flange(s) B1 and one or more secondary flange(s) B2 which are axially supported against the corresponding primary flange B1. The primary flange B1 may be at least one of the flanges among the first 35ab, second 35ba and third 362 flanges (or among the fourth 364 and fifth Eo flanges). The secondary flange B2 thus corresponds to the fixing flange (i.e., among the first 35ab, second 35ba, third 362, fourth 364 and fifth Eo flanges) to the primary flange B1.

[0087] Figure 4 illustrates, without limitation, an example of an embodiment of a primary flange BL

[0088] The primary flange Bl may include an annular row of first axial teeth TL

[0089] The first axial teeth Tl can be distributed around the first axis A.

[0090] The first axial teeth Tl can be identical to each other.

[0091] The primary flange Bl may comprise a number of first axial teeth Tl between 25 and 50.

[0092] The first axial teeth Tl can each have a general parallelepiped shape.

[0093] The first axial teeth Tl can each have a first angular range [3Di around the first axis A. This first angular range [3Di can be between 1° and 10°.

[0094] Fig. 5 illustrates, in a non-limiting manner, an example of the realization of a secondary flange B2.

[0095] The second flange B2 may include second axial teeth T2.

[0096] The second axial teeth T2 can be distributed around the first axis A.

[0097] The second axial teeth T2 can be identical to each other.

[0098] The second flange B2 may comprise a number of second axial teeth T2 between 25 and 50.

[0099] The second axial teeth T2 can each have a general parallelepiped shape.

[0100] The second axial teeth T2 can each have a second angular extent [3D2] around the first axis A. This second angular extent [3D2] can be between 1° and 10°.

[0101] One of the features of the invention is that the primary flange B1 includes first bearing faces and first ramp faces, and that the secondary flange B2 includes second bearing faces and second ramp faces.

[0102] As illustrated in Figures 4 and 5, the first and second support faces are distributed around the first axis A. The first support faces can be located in planes passing through the first axis A. The second support faces can be located in planes passing through the first axis A.

[0103] The first and second ramp faces can also be distributed around the first axis A.

[0104] In particular, the first axial teeth Tl of the primary flange B1 may include the first bearing faces B10 on a first side and the first ramp faces B12 on a second side which is opposite to the first side.

[0105] The first faces of ramps B12 can each be inclined at a first angle of inclination aBi2 with respect to a plane passing through the first axis A. This first angle of inclination aBi2 can be between 5° and 75°. As an example, the first angle of inclination aBi2 is approximately 25°.

[0106] The first axial teeth Tl can each include a first radial face B14. These first radial faces B14 are perpendicular to the first axis A. Each of the first radial faces B14 extends between the first bearing face B10 and the first ramp face B12 of the corresponding first tooth Tl.

[0107] According to the configuration of [Fig.4], the first radial faces B14 can each include a first orifice B18. These first orifices B18 are configured to receive at least part of the first 72 or the second 74 screws.

[0108] The primary flange B1 may include first hollow faces B16. Each first hollow face B16 may extend between a first bearing face B10 and a first ramp face B12. Each first hollow face B16 may be located between two adjacent first radial faces B14. In other words, each first hollow face B16 may be located between two adjacent first axial teeth T1.

[0109] In an alternative not illustrated, the first orifices B18 may be provided in the first hollow faces B16, instead of the first radial faces B14 (or between two adjacent first axial teeth T1), for example in the case of the second orifices B28 aligned with the first orifices B18 are provided in the second radial faces support B24 of the secondary flange B2.

[0110] The first hollow faces B16 can each have a third angular extent [3Bi6] around the first axis A. This third angular extent [3Bi6] can be between 1° and 10°. The first angular extent [3Di] can be identical or different from the third angular extent [3Bi6].

[0111] The second axial teeth T2 of the secondary flange B2 may include the second bearing faces B20 on a first side and the second ramp faces B22 on a second side which is opposite to the first side.

[0112] The second faces of ramps B22 can each be inclined at a second angle of inclination aB22 with respect to a plane passing through the first axis A. This second angle of inclination aB22 can be between 5° and 75°. As an example, the second angle of inclination aB22 is approximately 25°.

[0113] The second axial teeth T2 can each include a second radial face B24. These second radial faces B24 are perpendicular to the first axis A. Each of the second radial faces B24 extends between the second bearing face B20 and the second ramp face B22 of the corresponding second tooth T2.

[0114] The secondary flange B2 may include secondary hollow faces B26. Each secondary hollow face B26 may extend between a secondary bearing face B20 and a secondary ramp face B22. Each secondary hollow face B26 may be located between two adjacent secondary radial faces B24. In other words, each secondary hollow face B26 may be located between two adjacent secondary axial teeth T2.

[0115] According to the configuration of [Fig. 5], second holes B28 can be formed between the second axial teeth T2. In particular, these second holes B28 are provided in each of the second hollow faces B24. These second holes B28 are configured to receive at least part of the first 72 or the second 74 screws.

[0116] In an alternative not illustrated, the second orifices B28 can be provided in the second radial faces B24, instead of the second hollow faces B24, for example in the case where the first orifices B18 aligned with the second orifices B28 are provided in the first hollow faces B14 of the primary flange Bl.

[0117] The second hollow faces B26 can each have a fourth angular extent [3B26] around the first axis A. This fourth angular extent [3B26] can be between 1° and 10°. The second angular extent [3D2] can be identical or different from the fourth angular extent [3B26].

[0118] The primary and secondary flanges Bl, B2 are configured to be axially supported against each other.

[0119] To this end, the first bearing faces B10 are configured to cooperate by bearing in a tangential direction with the corresponding second bearing faces B20 of the secondary flange B2. The first ramp faces B12 are configured to cooperate with second faces of B22 ramp.

[0120] The first and second axial teeth T1, T2 may be complementary to each other. The first and second angular extents [3Di, [3D2] may be identical or different. The first and second inclination angles aBi2, aB22 may be identical or different.

[0121] Thus, advantageously, the first axial teeth T1 can be engaged axially between the second axial teeth T2 to form a dog clutch link between the primary flanges B1 and secondary flanges B2.

[0122] Figures 6 to 8 schematically illustrate, in a non-limiting manner, the different possibilities and positions of dog clutch connections in the mechanical reducer 3. For example, the mechanical reducer 3 may include at least one or more of the following dog clutch connections: - a first dog clutch connection L1 between the first and second flanges 35ab, 35ba ( [Fig.6]), - a second dog clutch connection L2 between one of the first and second flanges 35ab, 35ba and the third 362 flanges ([Fig.7]), and - a third dog clutch link L3 between the fourth and fifth flanges 364, Eo ( [Fig.8]), in which one of the flanges forms the primary flange B1 and the other of the flanges forms the secondary flange B2 which have been described above with reference in particular to figures 4 and 5.

[0123] Fig. 9 illustrates an example of a 3-epicycloidal mechanical reducer that can include these three dog clutch links L1, L2 and L3.

[0124] The differential mechanical reducer 3 may also include at least one of the dog clutch links L1, L2 and L3.

[0125] We will now describe the operation of the mechanical reducer 3 of the invention with reference to figures 10a, 10b, 1ia and 11b.

[0126] According to the invention, the first bearing faces B10 of the primary flange B1 are configured to cooperate by bearing in a tangential direction with the corresponding second bearing faces B20 of the secondary flange B2, which is axially supported against the primary flange B1, so as to transmit a torque transmitted by the ring 35 in a first direction DI around the first axis A.

[0127] The first radial faces B14 of the primary flange B1 can be configured to bear axially between the second axial teeth T2 of the secondary flange B2, in particular on the second hollow faces B26.

[0128] Alternatively, the second radial faces B24 of the secondary flange B2 can be configured to bear axially between the first axial teeth Tl of the primary flange Bl, in particular on the first hollow faces B16.

[0129] According to the invention, the first ramp faces B12 of the primary flange B1 are configured to cooperate with second ramp faces B22 of the secondary flange B2, so that a torque transmitted by the ring 35 in a second direction D2 around the first axis A, opposite to the first direction D1, causes, on the one hand, an axial separation of the primary and secondary flanges B1, B2 from each other, and on the other hand, a tensile force on the screws 72, 74 which are configured to break when this tensile force is greater than a predetermined threshold.

[0130] The term "predetermined threshold" means the moment when the torque transmitted by the ring 35 to the ring carrier 36 is along the first direction D1 in normal operation of the mechanical reducer 3. For example, this predetermined threshold is exceeded when the ring carrier 36 is subjected to a torque along the second direction D2, in particular in the event of failure of the satellite bearing 34.

[0131] Figures 10a and 11a schematically represent the normal operation of the mechanical reducer 3, and in particular the forces exerted on each of the components of the mechanical reducer 3 (illustrated by simple arrows in the figures). As described above with reference to the mechanical reducer 3 of [Fig. 2] or [Fig. 3], the rotation of the solar element 31 (driven by the low-pressure shaft 1ae) rotates the satellites 32 inside the ring 35, which is either stationary or rotating. The rotation of the satellites 32 rotates either the satellite carrier 33 or the ring 5, so as to rotate the blower S via the blower shaft 1s. The rotating satellites 32 transmit an axial force to the ring 35, which is directed outwards from the mechanical reducer. The crown 35 in turn transmits a torque to the crown carrier 36 along the first direction Dl around the first axis A.In this first torque transmission direction Dl (illustrated by double arrows in the figures), the first bearing and ramp faces B10, B12 are, on the one hand, circumferentially supported respectively by the corresponding secondary bearing and ramp faces B20, B22, and on the other hand, the primary and secondary flanges Bl, B2 are axially tightened by screws 72, 74. This maintains a robust connection between the primary and secondary flanges Bl, B2. The first and second bearing faces B10, B20 allow the torque transmitted by the ring 35 to be absorbed.

[0132] Figures 10b and 11b schematically represent the abnormal operation of the mechanical reducer 3, and in particular the forces exerted on each of the components of the mechanical reducer. For example, in the event of failure of the planetary bearing(s) 34, the direction of torque transmission from the ring gear 35 to the ring carrier 36 is reversed. Thus, the ring gear 35 transmits torque to the ring carrier 36 in the second direction D2 around the first axis A. This second direction D2 (illustrated by double arrows in Figures 10b and 11b) of Torque transmission can generate additional forces (illustrated by dashed arrows in [Fig. 11b]) on the first and second faces of ramps B12, B22, which cause tensile forces on the first and / or second screws 72, 74. When these tensile forces exceed the predetermined threshold (for example, a satellite bearing failure), they cause the ramp faces B12, B22 to move axially apart and also lead to the failure of these screws 72, 74, thereby breaking the connection between the primary and secondary flanges B1, B2. This allows the connection between the primary and secondary flanges B1, B2 to be separated (for example, the half-rings 35a, 35b, the ring 35, 35a, 35b and the ring carrier 36 and / or between the ring carrier 36 and the other element E). The rotation of the failed satellite(s) remains blocked.In this way, the solar 31 allows the satellite carrier 33 or the ring 35 to be driven directly into rotation through the blocked satellite(s) 32, to rotate the blower S (via the blower shaft 1s).

Claims

Claims

1. Mechanical reducer (3) for a turbomachine (1), in particular an aircraft, this reducer comprising: - a solar (31) having a first axis of rotation (A), - a crown (35) which extends around the sun and said first axis (A), the crown comprising two annular half-crowns which are fixed to each other respectively by first and second annular flanges (35ab, 35ba), - satellites (32) which are arranged around the first axis (A), between the sun and the crown, and which are meshed with the sun (31) and the crown (35), these satellites (32) each having a second axis (B) of rotation parallel to the first axis (A) and being held by a planet carrier (33) movable in rotation around said first axis (A), - a crown carrier (36) having a generally annular shape around the first axis (A), the crown carrier (36) comprising a third annular fixing flange (362) to the first and second flanges (35ab, 35ba), and a fourth annular fixing flange (364) to a fifth annular flange (Eo) of another annular element extending around the first axis (A), said first, second and third flanges (35ab, 35ba, 362) being clamped axially against each other by first screws (72) parallel to the first axis (A),and said fourth (364) and fifth (Eo) flanges being axially clamped against each other by second screws (74) parallel to the first axis, characterized in that one of the flanges, called primary flange (Bl), among the first, second and third flanges (35ab, 35ba, 362), or among the fourth and fifth flanges (362, Eo), comprises first bearing faces (B 10) which are distributed around the first axis (A) and first ramp faces (B 12) which are distributed around the first axis (A), the first bearing faces (B10) being configured to cooperate by bearing in a tangential direction with corresponding second bearing faces (B20) of another of said flanges, called secondary flange (B2), which is in axial bearing against the primary flange (B1), so as to transmit a torque transmitted by the crown (35) in a first direction (D1) around the first axis (A), and the first ramp faces (B 12) being configured to cooperate with second ramp faces (B22) of said secondary flange (B2) so that a torque transmitted by the crown (35) in a second direction (D2) around the first axis (A), opposite to the first direction (Dl), causes an axial separation of the flanges (Bl, B2) from each other and a tensile force on the first and / or second screws (72, 74) which are configured to break when this tensile force is greater than a predetermined threshold.

2. Reducer according to claim 1, characterized in that the primary flange (Bl) comprises an annular row of first axial teeth (Tl) which are axially engaged between second axial teeth (T2) of the secondary flange (B2), to form a dog connection (Ll, L2, L3) between the primary and secondary flanges (Bl, B2).

3. Reducer according to claim 2, characterized in that the first and second axial teeth (Tl, T2) of each of the primary and secondary flanges (Bl, B2) are regularly distributed around said first axis (A).

4. Reducer according to claim 2 or 3, characterized in that the first and second axial teeth (Tl, T2) of each of the primary and secondary flanges (Bl, B2) are identical.

5. Reducer according to any one of claims 2 to 4, characterized in that the first and second axial teeth (T1, T2) of each of the primary and secondary flanges (B1, B2) respectively comprise said first and second bearing faces (B10, B20) on a first side, and said first and second ramp faces (B12, B22) on a second side, opposite the first side.

6. Reducer according to any one of claims 1 to 5, characterized in that each of the primary and secondary flanges (B1, B2) comprises a number of teeth between 25 and 50.

7. Reducer according to any one of claims 2 to 6, characterized in that the first and second axial teeth (T1, T2) each have a generally parallelepiped shape.

8. Reducer according to any one of claims 2 to 7, characterized in that the first axial teeth (T1) of the primary flange (B1), respectively of the secondary flange (B2), each comprise a radial face (B14, B24) perpendicular to said first axis (A) and extending between the bearing face (B10, B20) and the ramp face (B12, B22) of this first tooth (T1), this radial face (B14, B24) being configured to bear axially between the second axial teeth (T2) of the secondary flange (B2), respectively of the primary flange (Bl).

9. Reducer according to any one of claims 2 to 8, characterized in that the first (72) and / or second (74) screws pass through first orifices (B 18) formed in the first teeth (Tl) of the primary flange (Bl), respectively of the secondary flange (B2), and second orifices (B28) formed between the second teeth (T2) of the secondary flange (B2), respectively of the primary flange (Bl).

10. Reducer according to any one of the preceding claims, characterized in that each of the first and second ramp faces (B 12, B22) has an angle of inclination (aBi2, «1222) relative to a plane passing through said first axis (A), which is between 5° and 75°.

11. Reducer according to any one of claims 2 to 10, characterized in that the first and second axial teeth (Tl, T2) each have an angular extent (|3Ti, |3T2) around the first axis (A) which is between 5° and 10°.

12. Reducer according to any one of the preceding claims, characterized in that said first bearing faces (B 10) are located in planes passing through the first axis (A).

13. Turbomachine, in particular for an aircraft, comprising a mechanical reducer according to any one of the preceding claims.

Images