ASSEMBLY FOR AN AIRCRAFT TURBOMACHINE PROPELLER

Abstract

Assembly for an aircraft turbomachine propeller (10), this assembly comprising a variable-pitch blade (14), a blade pitch control system (76) comprising a sleeve (80) engaged in a metal body (102) forming the blade root, and a tie rod (120) passing through the sleeve (80) and the metal body (102) to connect the blade to the control system (76) and pre-stress the metal body (102). Figure for the abbreviation: Figure 4

Description

Title of the invention: ASSEMBLY FOR AN AIRCRAFT TURBOMACHINE PROPELLER Technical field of the invention

[0001] The present invention relates to the field of aircraft turbomachinery and in particular to the propulsion propellers of these turbomachinery which have variable pitch blades. Technical background

[0002] The state of the art includes in particular the documents FR-A1-3 017 163, FR-Al-3 080 322 and WO-A1-2022 / 018353.

[0003] An aircraft turbomachine propeller can be shrouded, as is the case of a fan for example, or unshrouded as is the case of an open-rotor type architecture for example.

[0004] A propeller comprises blades which may have variable pitch. The turbomachine then comprises a mechanism for modifying the pitch angle of the blades in order to adapt the thrust generated by the propeller according to the different phases of flight.

[0005] The design of a propeller blade involves several disciplines whose objectives are generally conflicting. It must allow for optimal aerodynamic performance (i.e., provide thrust while maximizing efficiency), guarantee the blade's mechanical strength (i.e., withstand the mechanical stresses resulting from static and dynamic loads), while limiting mass and acoustic signature. In particular, improving the propeller's aerodynamic performance tends toward an increase in the BPR (Bypass Ratio), which translates into an increase in its external diameter and therefore the blade span. However, increasing the BPR goes hand in hand with reducing the FPF (Fan Pressure Ratio). Consequently, a pitch control system (variable-pitch blade) is generally required for the propeller to be operable throughout its entire flight envelope.

[0006] There are several technologies for attaching a variable pitch propeller blade and several technologies for controlling the angular pitch of such a propeller blade.

[0007] A propeller generally comprises a hub which carries blade retention systems and controls for the angular pitch of its blades. The hub has a generally annular or polygonal shape around a first axis which is the longitudinal axis of the turbomachine, and includes orifices distributed around this first axis in which the blade roots and the aforementioned systems are housed.

[0008] Each of these orifices has a substantially radial orientation with respect to the first axis and receives guide bearings for the foot of a blade around a second radial axis relative to the first axis, and which is a shimming axis for the corresponding blade.

[0009] Each propeller blade comprises a blade connected by a strut to a foot that is centered on the blade's pitch axis. The blade can be formed by a metal body and a fibrous preform obtained by weaving fibers in three dimensions and embedded in a polymer matrix. The preform forms the blade, and the metal body forms the foot and strut, as well as a spar that extends into the blade along the pitch axis.

[0010] The foot of each blade is mounted in one of the hub's bores and in the bearings of that bore, and is retained in that bore by a retaining system. Each foot is also associated with a system for controlling its angular positioning.

[0011] The metallic body thus becomes an integral part of the blade and makes it possible to create a mechanical interface with the bearings allowing the variable pitching of the blade.

[0012] In the event of a blade loss, its density is such that it imparts significant energy to the debris. The energy of debris released onto an unshielded propeller is a fundamental element to optimize, as the debris can impact the aircraft fuselage. It is therefore a key factor in fuselage armoring, impacting the aircraft's mass and thus the overall performance of the engine / aircraft combination.

[0013] The invention provides a solution to at least some of the problems of the prior art and aims to optimize safety in the event of blade loss, particularly in a non-cased architecture. Summary of the invention

[0014] The invention relates to an assembly for an aircraft turbomachine propeller, this assembly comprising a variable-pitch blade and a control system for the pitch of this blade,

[0015] the blade comprising a blade connected by a strut to a foot which is centered on a blade alignment axis, this blade being formed by a metallic body and a fibrous preform obtained by weaving fibers in three dimensions and embedded in a polymer matrix, the preform forming the blade, the metallic body forming the foot and strut as well as a spar which extends in the blade along the alignment axis, the metallic body further comprising an internal recess which is centered on the alignment axis and which opens axially at an end of the body opposite the blade,

[0016] the control system comprising a sleeve engaged by translation along the alignment axis inside said recess, this sleeve comprising external splines configured to be engaged in internal splines of the body,

[0017] characterized in that it further comprises a tie rod extending along the alignment axis and passing through the sleeve and the recess, this tie rod comprising a first one end located on the side of the blade, which is axially supported on the spar in the direction of the foot, and a second end located on the opposite side of the blade, which is threaded and receives a nut which is axially supported on the socket in the direction of the blade, the nut being tightened so as to apply a compressive stress to the body.

[0018] The invention thus proposes to associate a tie rod with the metal body of the blade, and in particular with its spar. This tie rod has the particularity of connecting the spar, and therefore the blade, to the blade's control system. It is therefore understood that, in the event of breakage of the metal body, for example, the tie rod still ensures the connection of the blade to the control system, which then retains the blade.

[0019] The tie rod can thus be considered as an integral part of the blade and is preferably joined to the rest of the blade during the manufacture of this blade.

[0020] The assembly according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0021] - the tie rod comprises two coaxial sections of different diameters, the section of the largest diameter being located on the blade side and having a shoulder for support on an internal span of the spar;

[0022] - the section with the largest diameter is prismatic and has a shoulder prismatic support on an internal bearing surface of complementary shape to the spar; the prismatic shape (in the shape of a right prism) prevents the tie rod from rotating around its axis when tightening the nut;

[0023] — the section with the smallest diameter is cylindrical;

[0024] - the nut is engaged inside the socket and bears against an internal rim of the socket;

[0025] - the tie rod passes through an opening in the longeron which extends from said recess to a cavity in the spar which is located inside the blade;

[0026] - the control system includes a connecting arm which is connected to the socket and includes a remote link axis from the alignment axis;

[0027] — the tie rod is made of metal or composite material.

[0028] The present invention further relates to a propeller for an aircraft turbomachine, this propeller comprising:

[0029] - a hub extending around a first axis and having distributed orifices around this first axis, each of these orifices having a substantially radial orientation with respect to said first axis and passing through said hub,

[0030] - assemblies according to one of the preceding claims, the feet of the blades being respectively engaged in the hub orifices and the alignment axis of each of the blades extending substantially radially with respect to said first axis,

[0031] - guide bearings for the blade feet in the hub orifices around said alignment axes, and

[0032] - systems for retaining the blade feet in the hub openings along of said alignment axes.

[0033] Advantageously, the foot of each of the blades is configured to be engaged in the corresponding hole of the hub by translation along the alignment axis of that blade, radially from the outside to the inside with respect to said first axis, inside the external and internal bearings, the foot of each of the blades comprising:

[0034] + a stop configured to bear against the alignment axis on the external bearing to retain the blade radially inwards relative to the first axis,

[0035] + an annular groove extending around the mounting axis and oriented radially outwards relative to this alignment axis, the groove being located radially inside the stop with respect to said first axis, and

[0036] and wherein the retention system for the base of each of the blades comprises:

[0037] + a ring, preferably sectorized, configured to be engaged in the groove of the foot of dawn, and

[0038] + an annular screw-nut assembly comprising an internal screw including a thread external, and an external nut having an internal thread for screwing onto the external thread of the internal screw, the internal screw being configured to be mounted around the foot, between the stop and the groove, and to bear in the direction of the shim axis on the ring on the side opposite the blade, and the external nut being configured to bear in the direction of the shim axis on the internal bearing on the blade side of the blade in order to retain the blade radially outwards with respect to the first axis.

[0039] The invention thus proposes a relatively simple configuration of the system that ensures the retention of the blade root in the hub opening. On the blade side, the blade root comprises a stop that bears directly or indirectly on the external bearing, which is advantageously mounted prior to the insertion of the root into the hub opening. On the side opposite the blade, the blade root comprises a groove in which a ring, preferably segmented, is fitted. The simple butting of the ring with the lateral walls of the groove, in the direction of the alignment axis, is sufficient to ensure the retention of the ring in the groove. This ring can advantageously form an additional stop for the blade root, which is then fitted onto the root. The blade root further comprises a receiving area for the screw-nut assembly, which can, for example, be in the form of an external cylindrical surface.This screw-nut assembly has the advantage of serving a dual purpose and requiring only a limited number of parts. The internal screw slides around the foot and engages with the ring, ensuring radial outward retention of the foot relative to the first axis. This can also allow... The ring is axially immobilized in the groove along the alignment axis, and even radially locked in the groove relative to this axis. The external nut is screwed onto the internal screw and engages with the internal bearing. The blade root is thus held by the external and internal bearings, via the thrust bearing on one side, and via the ring and the screw-nut assembly on the other.

[0040] The number of parts of the foot retention system is therefore relatively limited insofar as it may only include three parts, namely the ring and the two parts of the screw-nut assembly.

[0041] The propeller according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0042] — the ring is divided into two pieces and comprises two half-rings; - the ring comprises an inner periphery housed in the groove and an outer periphery located outside the groove and on which the internal screw bears;

[0043] — the inner periphery of the ring has an annular rim located on the side of the blade which is intended to cooperate by pressing against the internal screw to prevent the ring from accidentally coming out of the groove;

[0044] — the internal screw includes an annular rim which is located on the side opposite the blade and which extends around the outer periphery of the ring to prevent the ring from accidentally coming out of the throat;

[0045] — the internal screw and the external nut each comprise a series of oriented teeth radially outwards relative to the alignment axis;

[0046] — the series of teeth of the external nut is located on the side of the blade of the vane, and the series the teeth of the internal screw are located on the opposite side to the blade of the blade; - the propeller also includes an internal annular cover which is mounted around the foot and covers at least part of the internal bearing and / or the screw-nut assembly; - the internal hood comprises a first axial end, located on the blade side, which is axially supported on the internal bearing in the direction of the blade, and a second axial end, located on the opposite side, which is axially supported on the control system in a direction opposite to the blade; - the second end of the hood is axially interposed between the control system and an axial end of the metal body; - the second end of the hood is deformable by crushing between the control system and an axial end of the metal body;

[0047] — the inner hood comprises at least two teeth which are configured to cooperate by engaging with the series of teeth of the screw-nut assembly in order to im- mobilize in rotation around the alignment axis;

[0048] — the inner cover has its outer periphery which is supported in the direction of the axis of shimming on the hub, for example via an annular joint;

[0049] — the inner hood includes an internal cylindrical centering surface which is configured to cooperate with a complementary external cylindrical surface of the internal bearing, and for example of an internal ring of this internal bearing;

[0050] — the centering surface is located on the inner periphery of an internal annular sail of the inner hood, this veil comprising through orifices for the passage of fluid and in particular lubricating oil for the bearings; - the base of each of the blades includes an internal recess which opens radially inwards with respect to the first axis and which has internal grooves extending around the pitch axis, the propeller further comprising a pitch control system which is associated with the base of each of the blades, the control system comprising an eccentric of which a bushing is engaged by translation in the direction of the pitch axis inside the recess, this bushing having external grooves configured to be engaged in the internal grooves of the base;

[0051] — the stop at the foot of each of the blades is in direct contact with the external bearing, or is supported on the external bearing by means of an external annular cover which is mounted around the foot and which at least partially covers the external bearing;

[0052] — the outer cover has its inner periphery which is clamped between the stop and the bearing external, and its external periphery which is supported in the direction of the alignment axis on the hub, for example by means of an annular joint; - the external bearing includes an outer ring which bears in the direction of the shim axis and on the side opposite the blade on a stop located in the orifice of the hub, and / or the internal bearing includes an outer ring which bears in the direction of the shim axis and on the side of the blade on a stop located in the orifice of the hub; - the external bearing includes an internal ring which bears in the direction of the shim axis and on the side opposite the blade on a spacer mounted around the foot and in the orifice of the hub, and / or the internal bearing includes an internal ring which bears in the direction of the shim axis and on the side of the blade on a stop on the foot of the blade or on the aforementioned spacer;

[0053] — the inner ring of the outer bearing is supported on the spacer via of an adjustable shim, and / or the inner ring of the inner bearing is supported on the stop or on the spacer by means of an adjustable shim;

[0054] — the bearings have internal diameters that increase radially from the inside outwards with respect to said first axis; thus, the internal diameter of the bearing (radially) internal has an internal diameter that is smaller than the internal diameter of the (radially) external bearing;

[0055] — the screw-nut assembly is mounted on an external cylindrical surface of the foot;

[0056] — the bearings are rolling bearings, for example ball or roller bearings; the rollers that can be conical.

[0057] The present invention also relates to a turbomachine, in particular for aircraft, comprising at least one assembly or at least one propeller as described above.

[0058] The present invention finally relates to a method for detecting a failure in a propeller as described above, in which it comprises the following steps:

[0059] a) rupture of the metal body or ring,

[0060] b) displacement of the blade radially outwards relative to the first axis,

[0061] c) retention of this blade by its tie rod and the control system which bears, via the retention system and the internal bearing, on the hub, and

[0062] d) detection of imbalance related to displacement.

[0063] Advantageously, the movement of the blade causes the second end of the hood to be crushed between the control system and the axial end of the metal body. Brief description of the figures

[0064] 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:

[0065] [Fig-1] [Fig.1] is a schematic axial cross-sectional view of a helix for a tur aircraft engine,

[0066] [Fig.2] [Fig.2] is a larger-scale view of part of [Fig.1] and shows the foot of a blade mounted in an opening in a propeller hub,

[0067] [Fig.3] [Fig.3] is an even larger scale view of part of [Fig.2] and blade foot retention and control systems,

[0068] [Fig.4] [Fig.4] is a view similar to that of [Fig.2] and illustrating a mode of realization of the invention,

[0069] [Fig.5] [Fig.5] is a larger scale view of part of [Fig.4],

[0070] [Fig.6] [Fig.6] is a view similar to that of [Fig.4] and illustrating a de failure of the propeller, and in particular a break in the metal body of one of its blades, and

[0071] [Fig.7] [Fig.7] is a view similar to that of [Fig.4] and illustrating a de propeller failure and in particular a breakage of a retaining ring on one of its blades. Detailed description of the invention

[0072] Fig. 1 shows a propeller 10 for an aircraft turbomachine, this propeller 10 being shrouded or unshrouded.

[0073] The propeller 10 comprises a hub 12 and blades 14 carried by this hub 12.

[0074] The hub 12 has a generally annular or polygonal shape and extends around a first axis not shown.

[0075] In [Fig.1], one of the blades 14 of the propeller 10 is visible and the hub 12 is seen in axial section, the cutting plane passing through the first axis of the hub 12.

[0076] The hub 12 has orifices 12a distributed around the first axis, each of these orifices 12a having a substantially radial orientation with respect to this first axis. Each orifice 12a passes radially through the hub 12, that is to say, each orifice 12a opens radially outwards and radially inwards respectively.

[0077] The blades 14 each comprise a blade 16 and a foot 18. The feet 18 of the blades 14 are respectively engaged in the orifices 12a of the hub 12.

[0078] The blade 16 has an aerodynamic profile and comprises an intrados 16a and an extrados (not visible) which are connected by a leading edge 16c and a trailing edge 16d, the terms upstream and downstream referring to the flow of gases around the blade 16 in operation.

[0079] The blade 16 has an upper end which is free, called the apex, and a lower end which is connected to the foot 18.

[0080] The blade 14 can be made of composite material using an injection molding process called RTM (Resin Transfer Molding). This process involves preparing a fibrous preform by three-dimensional weaving, then placing this preform in a mold and injecting a polymerizable resin, such as an epoxy resin, which will impregnate the preform. After polymerization and hardening of the blade 16, its leading edge 16c is generally reinforced by a metal shield 20 that is attached, for example, by bonding.

[0081] The shield 20 can be made of titanium or titanium alloy, stainless steel, steel, aluminum, nickel, etc. The lower surface 16a or even the upper surface of the blade 16 can be covered with a polyurethane film 22 for erosion protection, or even with a heating mat allowing the blade to be de-iced.

[0082] A denotes the axis of extension of the blade 14 and the blade 16, and in particular the axis of adjustment of the blade 14, that is to say the axis around which the angular position of the blade 14 is adjusted. It is generally also a radial axis which therefore extends along a radius with respect to the first axis.

[0083] As can be seen more clearly in [Fig. 2], the foot 18 is hollow and includes an internal recess 18a in the example shown. The foot 18 has an elongated shape and tubular, its internal recess 18a being closed on the side of the blade 16 and open on the side opposite the blade 16.

[0084] The recess 18a of the foot 18 allows to reduce its mass, the shape and dimensions of the foot 18 being optimized to ensure good mechanical support of the blade 14 in operation.

[0085] The foot 18 has in its recess 18a internal grooves 24 which are configured to allow coupling of the foot 18 with a control system for the blade pitching around its pitching axis A (figures 2 and 3).

[0086] The grooves 24 extend around the axis A. In the example shown, they are located between two internal cylindrical surfaces 26a, 26b of the recess 18a, located respectively radially outside and inside the grooves 24 with respect to the first axis.

[0087] The foot 18 of the blade 14 further includes at its radially internal free end (opposite the first axis), an annular surface 26c which extends in a plane perpendicular to the axis A.

[0088] The foot 18 of the blade 14 includes one or more stops 28, 30. The stop or each stop 28, 30 has an annular shape and extends around the axis A and radially outwards with respect to this axis A.

[0089] In the example shown, the stop 28 is formed in projection at a radially external end of the foot 18 opposite the first axis, substantially at the level of the closed end of the recess 18a.

[0090] The stop 30 is formed in projection on a median part of the foot 18 opposite the first axis, located between the stop 28 and the free end of the foot 18.

[0091] The foot 18 of the blade 14 further includes an annular groove 32 which opens radially outwards and which is here formed in the vicinity of the free end of the foot 18.

[0092] Between the stop 28 and the groove 32, and more particularly between the stop 30 and the groove 32, the foot 18 comprises an external cylindrical surface 34a.

[0093] The foot 18 of the blade 14 comprises several external cylindrical centering surfaces SI, S2 and S3 in the example shown. The surfaces SI, S2 and S3 have decreasing diameters D1, D2 and D3 and are distributed along the axis A, radially from the outside to the inside with respect to the first axis.

[0094] The SI surface of largest diameter Dl is located between the stops 28, 30.

[0095] The surface S2 of intermediate diameter D2 is located between the stop 30 and the surface 34a.

[0096] The surface S3 of smaller diameter D3 is located between the groove 32 and the free end of the foot 18, and more particularly between the groove 32 and an external thread 34b of the foot 18. The thread 34b has a diameter smaller than that of the surface 34a.

[0097] The stop 28 is located at the radially external end of the surface SI with respect to the first axis. The stop 30 is located at the radially external end of the surface S2 with respect to the first axis.

[0098] The hub 12 may include annular fixing flanges 36 at each of its axial ends, as can be seen in [Fig.2].

[0099] In the example shown, each of the orifices 12a of the hub 12 includes stops 38, 40, 42, 44.

[0100] Each stop 38, 40, 42, 44 has an annular shape and extends around the axis A and radially inwards with respect to this axis A.

[0101] The stops 38, 40, 42, 44 are respectively arranged one after the other along the alignment axis A. There is thus a radially external stop 38, a radially internal stop 44 and two intermediate stops 40, 42.

[0102] The stop 38 has a larger diameter than the stop 40, and the stop 44 has a larger diameter than the stop 42.

[0103] The intermediate stops 40, 42 allow to accommodate bearings 46, 48 of guide of the feet 18 of the blades 14.

[0104] The bearings 46, 48 are here two in number and are mounted in the opening 12a of the hub, arranged radially one outside the other. The bearing located radially on the outside is thus designated as the external bearing 46, and the bearing located radially on the inside as the internal bearing 48.

[0105] The bearings 46, 48 are mounted inside the orifice 12a bearing axially (opposite the axis A) on the intermediate stops 40, 42. The bearings 46, 48 are mounted around the foot 18, and in particular around the surfaces SI and S2, bearing axially (opposite the axis A) on the stops 28, 30.

[0106] Advantageously, an intermediate piece is provided between the bearing 48 and the blade root 18, and in particular between the inner ring of the bearing 48 and the surface S2. This is a press-fitted sleeve on the blade root 18, which allows for a harder material than that (for example, titanium) of the root 18 as the bearing surface. Indeed, the inner ring of the bearing 48 cannot have a significant shrink fit on its axis because it is displaced during preloading. Therefore, to avoid a efretting phenomenon (material tearing that would result in a crack initiation on the blade root), this hard intermediate piece can be added.

[0107] The external bearing 46 is configured to be engaged in the orifice 12a from the outside of the hub 12, by moving it radially from the outside to the inside, until it comes to rest on the stop 40. The bearing 46 is here a ball bearing with angular contact and it is its outer ring that bears against the stop 40.

[0108] The internal bearing 48 is configured to be engaged in the orifice 12a from the inside of the hub, by moving it radially from the inside to the outside, until to come to rest on the stop 42. The bearing 48 is here a ball bearing, and in particular a double row ball bearing, and with angular contact and it is its outer ring which bears on the stop 42.

[0109] As can be seen in Figures 2 and 3, the foot 18 of the blade 14 is configured to be engaged in the orifice 12a by translation along the axis A, radially from the outside to the inside with respect to the first axis, inside the bearings 46, 48, until the thrust bearing 28 bears axially (with respect to the axis A) on the bearing 46, and in particular its inner ring, and the thrust bearing 30 bears axially (with respect to the axis A) on the bearing 48, and in particular its inner ring. The bearings 46, 48, and in particular their inner rings, are then mounted on the surfaces S1 and S2.

[0110] It is therefore understood that the external bearing 46 has an internal diameter greater than the internal diameter of the internal bearing 48 to allow the mounting of the foot 18 in the orifice 12a, insofar as the bearings 46, 48 are mounted prior to the foot 18 in the example shown.

[0111] The stop 28 of the foot 18 can bear directly (along axis A) on the external bearing 46 and in particular its inner ring. In the example shown, the stop 28 bears on the external bearing 46 by means of an external annular cover 50 which is mounted around the foot and which at least partially covers the external bearing 46.

[0112] This outer cover 50 has its inner periphery clamped between the stop 28 and the outer bearing 46, and in particular its inner ring. The outer periphery of the cover 50 bears in the direction of axis A on an annular seal 52 interposed between this outer periphery of the cover 50 and the hub 12, and in particular the stop 38. This assembly allows rotation of the cover relative to the hub during the rotation of the blade root.

[0113] The stop 30 of the foot 18 can bear directly (along axis A) on the internal bearing 48 and in particular its inner ring. In the example shown, the stop 30 bears on the internal bearing 48 by means of an adjustable shim 54.

[0114] An internal annular cover 56 can also be mounted around the foot 18 and cover at least part of the internal bearing 48.

[0115] The inner cover 56 has its outer periphery which is supported in the direction of the axis A on an annular joint 58 interposed between this outer periphery of the cover 56 and the hub 12, and in particular the stop 44. This assembly allows a rotation of the cover relative to the hub, during the rotation of the blade foot.

[0116] The hood 56 has its inner periphery which is radially supported with respect to the axis A on the foot 18, in the vicinity of its free end, either directly or via an annular seal 60, on an external cylindrical surface S3, as illustrated in the drawing.

[0117] In the example shown, the internal hood 56 includes at least two teeth 62, 64 oriented radially towards the axis A.

[0118] The inner cover 56 may further include an internal cylindrical centering surface 56a which is configured to cooperate with a complementary external cylindrical surface of the inner bearing 48, and for example of the inner ring of this bearing. This surface 56a may be located on the inner periphery of an internal annular web of the cover 56. This web may include through ports 65 for the passage of fluid and in particular lubricating oil for the bearings 46, 48 ([Fig. 3]).

[0119] The foot 18 is retained in the orifice 12a of the hub 12 by a retention system which essentially comprises a ring 66 and a screw-nut assembly 68. It is this screw-nut assembly 68 which allows a preload to be applied to the foot of the blade.

[0120] The ring 66 is mounted around the foot 18 of the blade and extends around the axis A. The ring 66 is sectorized and therefore comprises ring sectors arranged circumferentially end to end around the axis A. The number of sectors is not limited and can be reduced to two. The ring 66 then comprises two half-rings.

[0121] Alternatively, the ring could be continuous and not segmented. It could then include a slot to allow elastic deformation of the ring by separating its longitudinal ends.

[0122] The ring 66 is configured to be engaged in the groove 32 of the foot 18. It is understood that it is the sectorization of the ring 66 which allows its mounting in the groove 32. The ring 66 comprises an inner periphery housed in the groove 32 and an outer periphery intended to remain outside the groove 32 to form an axial stop (with respect to the axis A).

[0123] The screw-nut assembly 68 comprises an internal screw 68a and an external nut 68b. The internal screw 68a has an external thread 68al and an internal cylindrical surface 68a2 which is intended to cooperate by sliding with the surface 34a of the foot during the mounting and positioning of the assembly 68 on the foot.

[0124] The external nut 68b has an internal thread 68bl for screwing onto the external thread 68al of the internal screw 68a.

[0125] Positioning (by simple sliding) the internal screw 68a on the foot 18 allows it to be moved axially (relative to the axis A) on the foot 18 and positioned along the axis A. The screw 68a is able to bear in the direction of the axis A on the ring 66 on the side opposite the blade 16.

[0126] Screwing / unscrewing the external nut 68b allows it to be moved axially (with respect to axis A) on the internal screw 68a and to be positioned along axis A. The external nut 68b is able to bear in the direction of axis A on the internal bearing 48, and in particular on its inner ring, on the side of the blade 16.

[0127] The double support of the screw-nut assembly 68, respectively on the ring 66 and the bearing 48, and the screwing of the external nut 68b onto the internal screw 68a, allows a certain preload to be applied to the foot 18 of the blade by the retaining system.

[0128] The internal screw 68a includes an annular rim 70 which is located on the opposite side to the blade 16 and which extends around the outer periphery of the ring 66 to prevent the ring 66 from accidentally coming out of the groove 32.

[0129] The screw 68a and the nut 68b each comprise a series of teeth 72, 74 oriented radially outwards with respect to the axis A and configured to cooperate with the teeth 62, 64 of the inner cover 56 in order to immobilize the assembly 68 in rotation around the axis A.

[0130] The series of teeth 74 of the external nut 68b is located on the blade side

[0131] 16 and is configured to cooperate with tooth 64 of hood 56. The series of teeth 72 of the internal screw 68a is located on the opposite side to the blade 16 and is configured to cooperate with the tooth 62 of the hood 56.

[0132] In the example shown, the set of teeth 72 has an external diameter smaller than that of the set of teeth 74.

[0133] The propeller 10 further comprises a blade pitch control system 76, which is associated with the blade's foot 18. The propeller 10 therefore includes as many control systems 76 as there are blades 14 of this propeller.

[0134] Each control system 76 includes an eccentric 78 of which a sleeve 80 is engaged by translation along the axis A inside the recess 18a of the foot 18, radially from the inside to the outside with respect to the first axis.

[0135] The sleeve 80 has external grooves 82 configured to be engaged in the internal grooves 24 of the foot 18.

[0136] The sleeve 80 further comprises external cylindrical centering surfaces 80a, 80b cooperating with the surfaces 26a, 26b of the recess 18a when the sleeve 80 is inserted into the recess 18a. These surfaces 80a, 80b are located on either side of the grooves 82 along the axis A.

[0137] In the example shown, the socket 80 also includes an external annular rim 84 ([Fig.3]).

[0138] A threaded ring 86 is screwed onto the thread 34b of the foot, at its free end, and includes an internal annular rim 86a which bears in the direction of the axis A on the external rim 84 of the bushing 80, and in the direction of the blade 16 to retain the bushing 80 in the recess 18a of the foot 18.

[0139] The threaded ring 86 bears in the direction of axis A on the inner periphery of the inner cover 56, either directly or via an adjustment shim 88.

[0140] The threaded ring 86 may include a series of teeth 90 extending radially outwards with respect to the axis A, to allow the ring 86 to be engaged with a tool for screwing and unscrewing the ring.

[0141] Figures 4 and following illustrate an embodiment of the invention. The elements visible in these drawings and already described above are designated by the same references. The preceding description made in relation to figures 1 to 3 can therefore be used to describe at least part of the invention.

[0142] A first peculiarity of the propeller comes from the assembly formed by the blade 14 and its control system 76.

[0143] The blade 14 comprises a blade 16 connected by a strut 100 to a foot 18

[0144] which is centered on the alignment axis A of the blade 14.

[0145] The blade 14 is formed by a metallic body 102 and a fibrous preform 104 obtained by weaving fibers in three dimensions and embedded in a polymeric matrix.

[0146] The preform 104 forms the blade 16.

[0147] The metal body 102 forms the foot 18 and Péchasse 100 as well as a spar 106 which extends in the blade 16 along the alignment axis A.

[0148] The metal body 102 further includes the internal recess 18a which is centered on the alignment axis A and which opens axially at one end of the body 102 and of the foot 18 opposite the blade 16.

[0149] In the example shown, the recess 18a comprises a first portion 18al located on the side of the blade 16, which has in axial section a general elliptical shape and is elongated along the pitching axis A, and a second portion 18a2 located on the opposite side of the blade 16, which has a general cylindrical shape.

[0150] An annular shoulder 110 is located in the recess 18a, at the junction of portions 18al and 18a2. Portion 18a2 includes internal grooves 24. The recess 18a includes surfaces 26a, 26b similar to those described above, surface 26a being formed by the shoulder 110.

[0151] The spar 106 includes an opening 112 which extends towards the blade 16, along axis A, from the recess 18a. The opening 112 therefore opens into the recess 18a. This opening 112 extends into a cavity 114 of the spar 106 which preferably has a transverse dimension greater than that of the opening 112.

[0152] In the case where the orifice 112 and the cavity 114 each have a general cylindrical shape, the cavity 114 would preferably have an internal diameter U1 greater than that U2 of the orifice 112.

[0153] At the junction between the orifice 112 and the cavity 114, the spar 106 includes an internal cylindrical bearing surface 116.

[0154] As in the example shown, the orifice 112 and the recess 18a, or even the cavity 114, are preferably aligned and centered on the alignment axis A.

[0155] In the example shown, it can be seen that the recess 18a is formed in the foot 14 and that the orifice 112 extends at the level of Péchasse 100 and into the blade 16. The cavity 114 is located at the level of the blade 16.

[0156] It is also noted that the first part of the recess 18al is located at hub level 12, while orifice 112 is located radially outside the hub and the second portion 18a2 of the recess is located radially inside the hub.

[0157] The control system 76 includes a sleeve 80 engaged by translation along the alignment axis A inside the recess 18a, and more particularly in its second portion 18a2.

[0158] The sleeve 80 has external grooves 82 configured to be engaged in the internal grooves 24 of the body 102.

[0159] In the example shown, the control system 76 and in particular the bushing 80 also includes an external annular rim 84.

[0160] The control system 76 or its eccentric 78 may further include a linking arm 76a which is connected to the bushing 80 and includes a linking axis B at a distance from, and for example parallel to, the alignment axis A.

[0161] The assembly according to the invention further includes a tie rod 120 which can be an integral part of the blade 14.

[0162] The tie rod 120 extends along the shim A and passes through the bushing 80 and the recess 18a.

[0163] The tie rod 120 has a first end 120a located on the side of the blade 16, which is axially supported on the spar 106 and therefore the body 102 in the direction of the foot 18.

[0164] The tie rod 120 has a second end 120b located on the opposite side to the blade 16, which includes a thread 122 and which receives a nut 124. This nut 124 is axially supported on the sleeve 80 in the direction of the blade 16 and is advantageously tightened so as to apply a compressive stress to the body 102.

[0165] The tie rod 120 can be entirely metallic. Alternatively, it could be made of composite material.

[0166] In the example shown, it can be seen that the nut 124 bears against a shoulder 80c of the sleeve 80. It can also be seen that the nut 124 may have a coupling tooth 126 to allow a tightening / loosening tool to engage with this nut. This tooth 126 is located on the side opposite the blade 16.

[0167] The nut 124 can be engaged inside the sleeve 80 as in the example shown.

[0168] Tightening the nut 124 alone may be sufficient to apply the aforementioned compressive stress, this stress being for example in the order of three to four tonnes.

[0169] In the example shown, it can be seen that the tie rod 120 passes successively through the socket 80, and therefore the portion 18a2 of the recess 18a, and also passes through the portion 18al of the recess 18a and the orifice 112.

[0170] In the example shown, in the tight-fitting position illustrated in [Fig. 4], the external cylindrical surfaces 80a, 80b of the sleeve 80 cooperate by centering with the surfaces 26a, 26b of the recess 18a when the sleeve 80 is inserted into the recess 18a. The external splines 82 of the sleeve 80 are engaged in the internal splines 24 of the foot 18. The external rim 84 of the sleeve is preferably axially offset from the annular surface 26c of the foot 18 located at its radially internal free end, unlike the previous case in Figures 1 to 3. There is thus axial clearance in this area, between the rim 84 and the end of the foot 18.

[0171] As in the example shown, the tie rod 120 may comprise two coaxial sections 120c, 120d of different diameters, the larger diameter section 120c being located on the side of the blade 16 and comprising said end 120a which includes a shoulder 127 bearing on the internal span 116 of the spar 106.

[0172] Preferably, the larger diameter section 120c is prismatic and its shoulder 127 is prismatic and bears on the bearing 116 which is also prismatic to ensure anti-rotation of the tie rod 120 during its use.

[0173] The smaller diameter 120d section can be cylindrical.

[0174] The smaller diameter section 120d includes the end 120b and the thread 122.

[0175] As regards the hub 12 and the bearings 46, 48, they are similar to those described in the above.

[0176] As regards the foot retention system, the ring 66 and the screw-nut assembly 68 are also similar, and cooperate as indicated above with the bearing 48 and the foot 18.

[0177] The external annular cover 50 is similar to that described above.

[0178] The internal annular cover 130 of the retention system differs from the cover 56 described in the above essentially by the following characteristics.

[0179] The inner cover 130 is more clearly visible in [Fig. 5]. Its outer periphery or outer end 130a bears in the direction of axis A on an annular seal 58 interposed between this outer periphery of the cover 56 and the hub 12, and in particular the thrust bearing 44 or the bearing 48. This assembly allows rotation of the cover relative to the hub, during the rotation of the blade root.

[0180] The hood 130 has its inner periphery or inner end 130b which is radially supported with respect to the axis A on the foot 18, and in particular on its surface 26c, either directly or via an annular wedge 138 as illustrated in the drawing.

[0181] This internal end 130b is engaged in the aforementioned game J and is thus axially intercalated between the free end of the foot 18 and the annular rim 84 of the control system 76.

[0182] As can be seen more clearly in [Fig. 5], this internal end 130b is of axially compressible preference, that is to say that it has a capacity for plastic deformation in the axial direction, that is to say along the alignment axis A.

[0183] In the example shown, this deformation capacity is obtained by a particular shape of the end 130b which includes two annular support pads, respectively internal 132 and external 134, connected together by a frustoconical web 136. The internal pad 132 is supported on the free end of the foot 18 (and therefore its surface 26c), for example by the wedge 138, in the direction of the blade 16. The external pad 134 is supported on the rim 84, in the opposite direction to the blade 16.

[0184] In the unconstrained, non-free state, the web 136 is frustoconical and the pads 132, 134 are at distinct axial positions along the axis A, i.e., they are axially separated from each other. In the compressed and deformed state, the web 136 becomes planar and the pads 132, 134 are in the same plane as the web 136, which is perpendicular to the axis A.

[0185] Figures 6 and 7 show two distinct cases of propeller failure and illustrate a method according to the invention for detecting this failure.

[0186] The process comprises the following steps:

[0187] a) rupture of the metal body 102 or of the ring 66,

[0188] b) displacement of the blade 14 radially outwards with respect to the first axis (of rotation of the propeller),

[0189] c) retention of this blade 14 by its tie rod 120 and the control system 76 which bears, via the retention system and the internal bearing 48, on the hub 12,

[0190] d) detection of imbalance related to displacement, for example by at least one vibration sensor.

[0191] Figure 6 illustrates the first scenario of step a), i.e., the case where the metal body 102 breaks. In this figure, a break 140 of the metal body 102 occurs at the bottom of the groove 32 receiving the ring 66. In this case, due to the centrifugal forces in operation, the blade 14 is stressed radially outwards and is held by the tie rod 120 and the control system 76. The holding forces can reach nearly thirty tonnes and are absorbed by the hub 12, these forces being transmitted through the ring 66, the screw-nut assembly 68 and the internal bearing 48 in the example shown (see Arrow Fl). The breakage of the metal body 102 causes the reduction of the aforementioned clearance J and the crushing of the end 130b of the hood 130 between the control system 76 and the end of the foot 18, and in particular between the rim 84 and the surface 26c.

[0192] Figure 7 illustrates the second scenario of step a), that is, the case where it is the ring 66 that breaks. In this figure, after the breakage 142 of the ring 66, it is split in two, its inner peripheral part mounted in the groove 32 being dissociated of its external peripheral part located outside the throat 32.

[0193] In this case, due to the centrifugal forces in operation, the blade 14 is stressed radially outwards and is held by the tie rod 120 and the control system 76. The retention forces can reach nearly thirty tons and are taken up by the hub 12, these forces passing through the hood 130 and the internal bearing 48 in the example shown (see Arrow F2).

[0194] In yet another variant not shown, the bearings 46, 48 could be angular contact rolling bearings such as tapered roller bearings.

[0195] The present invention makes it possible to provide emergency force paths in the event of a break in part of the blade, so as not to release the most massive parts of this blade.

[0196] The invention thus makes it possible to minimize the mass of the freed blade part, which makes it possible to minimize the mass of the armor to be installed on the aircraft, to the benefit of the performance of the engine / aircraft couple.

[0197] The integration of the assembly according to the invention was carried out in the environment of the already existing parts, by optimizing their geometry and using the few spaces available (no impact on the overall volume of the blade foot and on the hub ratio of the motor).

Claims

Demands

1. Assembly for an aircraft turbomachine propeller (10), said assembly comprising a variable-pitch blade (14) and a blade pitch control system (76), the blade (14) comprising a blade (16) connected by a strut (100) to a foot (18) which is centered on a blade pitch axis (A), this blade (14) being formed by a metal body (102) and a fibrous preform (104) obtained by weaving fibers in three dimensions and embedded in a polymer matrix, the preform (104) forming the blade (16), the metal body (102) forming the foot (18) and strut (100) as well as a spar (106) which extends into the blade (16) along the pitch axis (A), the metal body (102) further comprising an internal recess (18a) which is centered on the alignment axis (A) and which opens axially at one end of the body (102) opposite the blade (16),the control system (76) comprising a sleeve (80) engaged by translation along the shim axis (A) inside said recess (18a), this sleeve (80) having external splines (82) configured to engage in internal splines (24) of the body, characterized in that it further comprises a tie rod (120) extending along the shim axis (A) and passing through the sleeve (80) and the recess (18a), this tie rod (120) having a first end (120a) located on the side of the blade (16), which bears axially on the spar (106) in the direction of the root (18), and a second end (120b) located on the side opposite the blade (16), which is threaded and receives a nut (124) which bears axially on the sleeve (80) in the direction of the blade (16), the nut (124) being tightened so as to apply a compressive stress to the body (102).

2. Assembly according to claim 1, wherein the tie rod (120) comprises two coaxial sections (120c, 120d) of different diameters, the section (120c) of larger diameter being located on the side of the blade (16) and having a shoulder (127) bearing on an internal bearing surface (116) of the spar (106).

3. Assembly according to claim 2, wherein the larger diameter section (120c) is prismatic and has a prismatic shoulder (127) bearing on an internal bearing surface (116) of complementary shape to the spar (106).

4. Assembly according to any one of the preceding claims, wherein the nut (124) is engaged inside the sleeve (80) and bears against an internal rim (84) of the sleeve (80).

5. Assembly according to any one of the preceding claims, wherein the tie rod (120) passes through an orifice (112) of the spar (106) which extends from said recess (18a) to a cavity (114) of the spar which is located inside the blade (16).

6. Assembly according to any one of the preceding claims, wherein the control system (76) comprises a linking arm (76a) which is connected to the bushing (80) and includes a linking shaft (B) at a distance from the shim shaft (A).

7. Propeller (10) for an aircraft turbomachine, said propeller (10) comprising: - a hub (12) extending about a first axis and having orifices (12a) distributed about this first axis, each of these orifices (12a) having a substantially radial orientation with respect to said first axis and passing through said hub (12), - assemblies according to any one of the preceding claims, the feet (18) of the blades (14) being respectively engaged in the orifices (12a) of the hub (12) and the spar axis (A) of each of the blades (14) extending substantially radially with respect to said first axis, - bearings (46, 48) for guiding the feet (18) of the blades (14) in the orifices (12a) of the hub (12) about said spar axes (A), and - retaining systems for the feet (18) of the blades (14) in the orifices (12a) of the hub (12) along said staking axes (A).

8. Propeller (10) according to the preceding claim, wherein the foot (18) of each of the blades (14) is configured to be engaged in the corresponding orifice (12a) of the hub (12) by translation along the alignment axis (A) of this blade (14), radially from the outside in with respect to said first axis, within the outer and inner bearings (46, 48), the foot of each of the blades (14) comprising: + a stop (28) configured to bear against the outer bearing (48) in the direction of the alignment axis (A) in order to retain the blade (14) radially inward with respect to the first axis, + an annular groove (32) extending around the alignment axis (A) and oriented radially outward with respect to this alignment axis (A), the groove (32) being located radially at the inside of the stop (28) opposite said first axis, and and wherein the retention system for the foot (18) of each of the blades (14) comprises: + a ring (66), preferably sectored, configured to be engaged in the groove (32) of the foot (18) of the blade (14), and + an annular screw-nut assembly (68) comprising an internal screw (68a) having an external thread (68al), and an external nut (68b) having an internal thread (68b 1) for screwing onto the external thread (68al) of the internal screw (68a), the internal screw (68a) being configured to be mounted around the foot (18), between the stop (28) and the groove (32), and to bear in the direction of the shim axis (A) on the ring (66) on the side opposite the blade (16), and the external nut (68b) being configured to bear in the direction of the shim axis (A) on the internal bearing (48) on the blade side (16) of the blade (14) in order to retain the blade (14) radially outwards with respect to the first axis.

9. Propeller (10) according to claim 8, wherein the ring (66) comprises an inner periphery housed in the groove (32) and an outer periphery located outside the groove (32) and on which the internal screw (68a) bears.

10. Propeller (10) according to claim 8 or 9, wherein it further comprises an internal annular cover (56) which is mounted around the foot (18) and covers at least in part the internal bearing (48) and / or the screw-nut assembly (68).

11. Propeller (10) according to the preceding claim, wherein the inner cowling (130) comprises a first axial end (130a), located on the side of the blade (16), which is axially supported on the inner bearing (48) in the direction of the blade, and a second axial end (130b), located on the opposite side, which is axially supported on the control system (76) in a direction opposite to the blade (16).

12. Propeller (10) according to the preceding claim, wherein the second end (130b) of the hood (130) is axially intercalated between the control system (76) and an axial end of the metal body (102).

13. Propeller (10) according to claim 11 or 12, wherein the second end (130b) of the hood (130) is deformable by crushing between the control system (76) and an axial end of the metal body (102).

14. Turbomachine, in particular for aircraft, comprising at least one assembly according to any one of claims 1 to 6, or a propeller (10) according to one of the demands 7 to 13.

15. A method for detecting a failure in a propeller according to any one of claims 7 to 13, wherein it comprises the following steps: a) rupture of the metal body (102) or of the ring (66), b) displacement of the blade (14) radially outwards with respect to the first axis, c) retention of this blade (14) by its tie rod (120) and the control system (76) which bears through the retention system and the internal bearing (48) on the hub (12), and d) detection of the imbalance related to the displacement.

16. A method according to claim 15, the propeller (10) being as defined in claim 13, wherein the movement of the blade (14) causes the second end (130b) of the hood (130) to be crushed between the control system (76) and the axial end of the metal body (102).

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