Aircraft turbine with variable pitch propeller blades

Abstract

The invention relates to an assembly for an aircraft turbomachine, comprising a propeller blade (10) having a root (14) extending from an upper end connected to a blade (12) of the blade (10) to a free lower end (28), the root (14) having a protruding section referred to as a "spherical portion (32)", and a system (34) for angularly setting the pitch of the blade (10), a system (34) for angularly setting the pitch of a blade (10) comprises a cup (58) delimited radially by an annular wall (58a) and comprising a lower bottom closed by a bottom wall (58b), and an upper opening (58c) through which a ball (32) is intended to be inserted axially into the cup (58), the bottom wall (58b) comprising a projection (200), the projection (200) being arranged in the cup (58). The protrusion engages the free end (28) of the root (14) in a recess (202) having a complementary shape.

Description

Technical Field

[0001] The present invention relates to the field of aircraft turbomachines and in particular to propulsion propellers of these turbomachines comprising variable pitch blades. Background Art

[0002] The background art includes documents US Pat. No. 2-8,753,088 and DE-C-921 788.

[0003] An aircraft turbine propeller may be ducted, such as in the case of a fan, or unducted, such as in the case of an open rotor architecture.

[0004] The propeller comprises blades which may be variable pitch. The turbine therefore comprises a mechanism enabling the pitch angle of the blades to be varied in order to adapt the thrust generated by the propeller to the different flight phases.

[0005] The design of propeller blades involves multiple rules with often conflicting objectives. The propeller blades must be designed so as to obtain the best aerodynamic performance (i.e. provide thrust while maximizing efficiency) and to ensure the mechanical strength of the blades (i.e. withstand the mechanical constraints resulting from static and dynamic loads) while limiting mass and acoustic signature. In particular, an improvement in the aerodynamic performance of the propeller tends to increase the By Pass Ratio (BPR), which translates into an increase in the outer diameter of the propeller and, therefore, into an increase in the span of the blades.

[0006] At the same time, in some turbine architectures, the engine is started with a very open pitch, known as feathering. In fact, this starting position enables the power to be consumed by torque, which ensures mechanical safety by ensuring a low propeller speed. More precisely, according to simple considerations, the power is proportional to the product of speed and torque. However, the torque increases with the angle of incidence, which can be increased by the pitch. In fact, those skilled in the art of aerodynamics understand that the resultant force generated on the blade profile is approximately perpendicular to the chord and can be decomposed into two components: namely the thrust along the axis of the engine and the blade drag in the plane of the propeller. Therefore, as the pitch of the blade increases, the resultant force is displaced towards the propeller plane, thereby increasing the drag of the aerodynamic profile and reducing the thrust.

[0007] Thus, in the case of feathered start, the thrust produced by the propeller is zero, the torque is maximum, and the speed is minimum. However, the incidence becomes so high that the blade is subjected to a turbulent, high-lift aerodynamic flow that produces a strong vibration excitation. This excitation is broadband due to the small eddies in the lift region, but is also strong at certain specific frequencies due to the large Karman recirculation that causes significant oscillations in the aerodynamic forces. In particular, in large chord and large span blades that produce a lot of drag, the forces are strong even at low speeds.

[0008] In the current state of the art, it is common practice to attach the blade to its support with attachments known as broaches. The blade comprises a root having a generally dovetail shape and intended to engage in a form-fitting manner in a pocket of the support, which pocket is usually made by broaching.

[0009] However, this type of fixing does have its disadvantages. In particular, aerodynamic forces can cause the root of the blade to move rigidly in the groove of the root, similar to a ball joint, resulting in friction damage of the blade and the wedge inserted between the root and the bottom of the groove in just a few cycles. Therefore, for propeller blades with variable pitch, wide chord and large span, pin-type fasteners are not a feasible solution.

[0010] In documents FR-A1-3 112 819 and FR-A1-3 112 820, the applicant proposes a type of spherical fastener. The blade is equipped with a suitable root to limit the risk of spherical engagement. The particular feature of the root of the blade is a convex section, which ensures optimal retention of the blade along the axis of the blade. Compared with pin-type fasteners, this technique reduces premature wear of the blade during flight phases that could excite vibration modes of the blade. In addition, the blade root is very advantageous in terms of overall dimensions and aerodynamic profile refinement.

[0011] The blade is part of an assembly which also includes a system for angularly tilting the blade around a so-called pitch axis. The pitch system comprises a cup comprising an annular wall extending around the axis, a lower bottom closed by a bottom wall and an upper opening through which a ball is intended to be inserted into the cup.

[0012] The bottom wall is designed to cooperate with the free end of the root in a form-fitting manner so that the cup is secured against rotation relative to the root about the axis.

[0013] In the above-mentioned document, the free end of the root comprises a protrusion which engages in a recess in the bottom wall of the cup. This protrusion is bulky and represents a significant mass of the blade, which therefore has an influence on the operating behavior of the blade.

[0014] The present invention is an improvement on the technology, which is simple, effective and economical. Summary of the invention

[0015] The invention provides an assembly for an aircraft turbomachine, comprising a propeller blade and a system for angularly setting the pitch of the blade about an axis known as the pitch axis.

[0016] The blade has a root extending from an upper end connected to the blades of the blade to a free lower end, the root having a convex section called a "bulb".

[0017] The system for angularly setting the pitch of a blade comprises a cup-shaped portion radially delimited by an annular wall extending around the pitch axis, the cup-shaped portion comprising a lower bottom and an upper opening, the lower bottom being closed by the bottom wall, the ball being intended to be inserted axially into the cup-shaped portion through the upper opening, the bottom wall being configured to cooperate in a form-fitting manner with the free end of the root so that the cup-shaped portion is secured against rotation relative to the root around the pitch axis,

[0018] Characterized in that the bottom wall comprises a projection which extends along the pitch axis and which engages in a recess of complementary shape to the free end of the root.

[0019] The invention therefore proposes to do the opposite of the prior art configuration and to provide a recess in the free end of the spherical root and thus a protrusion on the bottom of the cup. This is particularly advantageous because the invention reduces the footprint of the root and, in particular, the weight. As a result, the mass of the blade is reduced, which has a positive effect on the operating behavior of the blade, in particular under the action of centrifugal forces.

[0020] The assembly according to the invention may include one or more of the following features, which may be employed independently of one another or in combination with one another:

[0021] - the recess and the protrusion are eccentric with respect to the pitch axis;

[0022] - the recess and the protrusion are centered on the pitch axis;

[0023] - a recess is formed in the metallic material portion of the root;

[0024] - a recess is formed in the composite material portion of the root;

[0025] - the cross-sectional shapes of the recesses and protrusions are selected from ellipse, star, cross and polygon;

[0026] - the cross section of the bulb is circular and convex about the pitch axis;

[0027] - the bulb is connected to the blade by a strut, the cross section of which is smaller than the cross section of the bulb;

[0028] - the cross section of the protrusion is smaller than the cross section of the bulb;

[0029] - The cross section of the protrusion is smaller than the cross section of the strut.

[0030] The invention also relates to an aircraft turbomachine comprising an assembly as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Other features and advantages of the present invention will become apparent from the following detailed description and for understanding of the description reference is made to the accompanying drawings, in which:

[0032] [ Figure 1 ] Figure 1 is a schematic perspective view of a propeller blade for an aircraft turbine.

[0033] [ Figure 2 ] Figure 2 yes Figure 1 and showing the root of the blade,

[0034] [ Figure 3 ] Figure 3 is along Figure 4 A cross-sectional view of the section plane Pb in FIG. 1 shows the shape and position of the free lower end of the root relative to the pitch axis,

[0035] [ Figure 4 ] Figure 4 It is shown Figure 1 Axial cross-sectional view of the root of a blade of , which root is fixed in the cup of the pitch system of an assembly according to the prior art,

[0036] [ Figure 5 ] Figure 5 is with Figure 4 A similar view, and showing an axial section of an assembly according to one embodiment of the invention,

[0037] [ Figure 6 ] Figure 6 is with Figure 5 A similar view and showing an axial section of an assembly according to an alternative embodiment of the invention, and

[0038] [Fig. 7a to Fig. 7i] Fig. 7a to Fig. 7i are highly schematic views of blade root protrusions and illustrate a number of variations of the invention. DETAILED DESCRIPTION

[0039] In the following description, elements having the same structure or similar function will be referred to by the same reference numerals.

[0040] In the remainder of the description, an axial orientation from the bottom (close to the root of the blade) to the top (close to the free end of the blade) along the pitch axis "A" of the blade is adopted in a non-limiting manner. A radial direction from the inside (close to the pitch axis) to the outside extending orthogonally to the pitch axis is also adopted.

[0041] Figure 1 A blade 10 is shown for a propeller of an aircraft turbomachine, the propeller being of the ducted or unducted type.

[0042] Bucket 10 includes blades 12 connected to a root 14 .

[0043] The blade 12 has an aerodynamic profile and comprises a pressure side 12a and a suction side 12b connected by an upstream leading edge 12c and a downstream trailing edge 12d, the terms “upstream” and “downstream” referring to the flow of gas around the blade 12 in operation.

[0044] The blade 12 has a free upper end, called the apex, and a lower end connected to a root 14 .

[0045] In the example shown, the blade 10 is made of composite material by an injection method known as Resin Transfer Molding (RTM) method. This method consists in preparing a fiber preform 18 by three-dimensional weaving, then arranging the preform in a mold and injecting a polymerizable resin (for example epoxy resin) which will impregnate the preform. After the blade 12 has been cured and hardened, the leading edge 12c of the blade is usually reinforced by a metal sheath 20 which is fitted and attached, for example, by gluing.

[0046] The blade 10 comprises a spar 22. The spar 22 comprises a portion forming a web of the blade 12. The portion of the spar 22 forming a web of the blade 12 is intended to be inserted into the preform 18 before the resin is injected. The spar 22 also comprises a portion extending on the opposite side of the apex of the blade 12 to form the root 14.

[0047] The spar 22 is preferably made of a composite material, for example a 3D woven carbon fiber reinforced epoxy organic matrix composite material having warp yarns oriented primarily radially and weft yarns oriented primarily according to the chord of the blade 12 at the aerodynamic duct height.

[0048] Alternatively, the spar may also be formed from a more mechanically favorable combination of different organic matrix composite materials (thermoset, thermoplastic or elastomeric) reinforced with long fibers (carbon, glass, aramid, polypropylene) in a variety of fiber arrangements (woven, woven, knitted, unidirectional fiber arrangements).

[0049] Although not shown, the blade 12 may be hollow or solid and include an inner cavity filled with a foam or honeycomb type filler material that is mounted around the spar 22 and covered with a shell of an organic matrix composite material to increase the impact resistance of the blade 12 .

[0050] The sheath 20 may be titanium or titanium alloy, stainless steel, steel, aluminum, nickel, etc. The inner arc surface 12a or the outer arc surface 12b of the blade 12 may be covered with a polyurethane film to prevent erosion.

[0051] The root 14 here has no metal annular sleeve surrounding it.

[0052] The axis "A" is the axis of elongation of the blade 10 and the blades 12 and in particular the pitch axis "A" of the blade 10, i.e. the axis about which the angular position of the blade 10 is adjusted. The axis "A" is also generally a radial axis, which therefore extends along a radius relative to the axis of rotation of the propeller with which the blade 10 is equipped.

[0053] The root 14 has Figure 2 The root 14 basically consists of three parts:

[0054] a free lower end 28 positioned opposite the blade 12,

[0055] - an upper support 30 located on one side of the blade 12, and

[0056] A convex section, called “bulb” 32 , situated between the free end 28 and the support 30 .

[0057] In the example shown, the free end 28 has a substantially parallelepiped shape. Figure 3 It can be seen that the free end 28 is offset from the pitch axis "A" to achieve keying or positioning, which will be explained in more detail below.

[0058] Reference Figure 4 , Pb is defined as a transverse plane, ie a plane perpendicular to the pitch axis "A", passing approximately through the middle of the free end 28 and measured along the pitch axis "A". This plane Pb is called the bottom plane or lower plane. Figure 3The cross-sectional shape of the free end 28 in this plane Pb is shown. This section, referred to as the lower section, has a value or surface area (eg maximum value) denoted Sb and is generally rectangular in shape in the example shown.

[0059] As will be described further below, the free end 28 is configured to cooperate with a system 34 for angularly setting the pitch of the blade 10 .

[0060] Refer again Figure 2 The support 30 has a relatively complex shape that makes it possible to provide a transition between the root 14 and the spar portion 22 forming the core of the blade 12. The support 30 schematically comprises:

[0061] - two lateral sides 30a, 30b, respectively situated on the side of the pressure side 12a and on the side of the suction side 12b of the blade 12, which converge towards each other and towards the apex of the blade 12 along the pitch axis "A", and

[0062] Two edges, respectively an upstream edge 30 c and a downstream edge 30 d , which, on the contrary, diverge from one another along the pitch axis “A” and towards the apex of the blade 12 .

[0063] Reference Figure 4 , Ph is defined as a transverse plane passing through the pillar 30 (particularly the lower end of the pillar 30). This plane Ph is called the high plane or upper plane. In this plane, the pillar 30 can have a non-circular cross-sectional shape, such as oval, oblong, square or rectangular. This section, called the high section, has a value or surface area (e.g., maximum value) denoted as Sh.

[0064] The bulbous portion 32 has a generally convex or domed shape that extends about the pitch axis "A".

[0065] Pm is defined as the middle plane passing through the bulb 32 and in particular in the portion of the largest cross section of the bulb, which is hereinafter referred to as the middle cross section denoted Sm. This plane Pm is called the median plane. In this plane, the cross section of the bulb 32 may have a circular shape, but this cross section is not restrictive.

[0066] It will be appreciated that plane Pm is located between planes Pb and Ph. The maximum cross-sectional dimension of the bulbous portion 32 decreases from plane Pm (Sm) to plane Ph and from plane Pm toward plane Pb. Therefore, it will be appreciated that Sm is greater than Sb and Sh. Furthermore, in the example shown, Sh is greater than Sb.

[0067] The blade 10 is intended to be mounted in an angular pitch system 34 which enables the angular position of the blade to be varied about a pitch axis “A” relative to a hub 36 of the propeller.

[0068] To this end, the pitch system 34 comprises bearings 54, 56. The number of bearings 54, 56 is two here, and they are a lower bearing 54 and an upper bearing 56, respectively.

[0069] The bearings 54, 56 are of the ball rolling type. In the example shown, the bearings 54, 56 have different diameters, and the balls of the bearings 54, 56 also have different diameters.

[0070] The lower bearing 54 extends generally between planes Pm and Pb and thus extends around the lower portion of the spherical portion 32. The lower bearing 54 has a smaller diameter than the upper bearing 56 and the balls of the lower bearing have a larger diameter than the balls of the upper bearing 56.

[0071] The lower bearing 54 is also in oblique contact. In the example shown, the bearing point or bearing surface of the balls on the raceways of the rings 54a, 54b of the balls is located on a frustoconical surface S1 extending along the pitch axis "A" and having its largest diameter on the side of the apex of the blade 10.

[0072] The upper bearing 56 extends substantially between the planes Pm and Ph and therefore extends around the upper part of the spherical portion 32. The upper bearing 56 is also angular contact. In the example shown, the bearing point or bearing surface of the balls on the raceways of the rings 56a, 56b of balls is located on a frustoconical surface S2 extending along the pitch axis "A" and having its largest diameter on the side of the free end of the root 14 of the blade 10.

[0073] Figure 4 An example of an angular pitch system 34 is shown.

[0074] The pitch system 34 comprises a cup 58. The cup 58 comprises an annular wall 58a extending around the pitch axis "A". The annular wall 58a radially delimits the inner volume of the cup 58. The inner volume of the cup 58 is closed downwardly by a bottom wall 58b extending opposite the free end 28 of the root 14. The cup 58 has an opening 58c at the upper axial end of the cup, which is radially delimited by the upper end edge of the annular wall 58a. The free end 28 of the root 14 and the bulbous portion 32 are intended to be inserted axially into the cup 58 through the upper opening 58c.

[0075] The annular wall 58a and the bottom wall 58b are formed integrally.

[0076] The bottom wall 58 b is configured to cooperate in a form-fitting manner with the free end 28 of the root 14 , so that the cup 58 is rotationally fixed to the root 14 about the pitch axis “A”, constituting the pivot of the associated blade 10 .

[0077] In the present case, it will be appreciated that the bottom wall 58b comprises a recess 60 having a non-circular and in particular rectangular cross section and configured to receive the free end 28, such as Figure 3 and Figure 4 As shown. Figure 2 It can be seen that the recess 60 is eccentric relative to the pitch axis "A" in a similar manner to the free end 28. This eccentricity enables positioning and keying when the root 14 is inserted and mounted in the cup 58, wherein only one engagement position of the free end 28 in the recess 60 is possible.

[0078] The recess 60 is located on the upper or inner surface of the bottom wall 58 b of the cup 58 , which is therefore located inside the cup 58 and oriented on one side of the root 14 .

[0079] The angular pitch system 34 generates a torque at the root 14 of the blade 10 that counteracts the torque generated by aerodynamic and centrifugal forces. Advantageously, the free end 28 is inserted directly into the recess 60 without interposing a mating element to directly force the root 14 to rotate. This provides a more direct force path, with the torque being applied directly to the root 14. The dimensions of the lower section are strictly smaller than the maximum dimension of the middle section to limit the circumferential overall dimension to this height.

[0080] The location of the middle extension (largest radial section of the spherical part 32) between the two bearings 54, 56 is very advantageous in terms of the overall radial dimensions, since part of the height of the bearing surface between the middle section and the high section is located inside the cup 58, contrary to the prior art with broaching attachments integrated in the pivot. This helps to reduce the overall radial dimensions of the angular pitch system 34.

[0081] This makes it possible to reduce the diameter of the lower bearing 54 situated below the middle section. Thus, the root 14 of the blade 10 can be integrated lower along the pitch axis "A", which significantly reduces the theoretical hub ratio associated with the integration of the root 14. It is known to those skilled in the art that a low hub ratio improves the performance of the engine, in particular because it is more compact and therefore lighter. This last point is a very important advantage of this technical solution compared to competitors, which traditionally propose barrels with a cylindrical outer shape.

[0082] The bottom wall 58b includes a lower surface or outer surface, which is located on the opposite side of the root 14 and includes a cylindrical extension 62, which extends along the pitch axis "A" and includes an external thread or external straight spline 64, which is used to rotationally connect the angular pitch system 34 with a pitch changing mechanism, which is not shown and is common to different angular pitch systems 34 and blades 10 of the propeller.

[0083] like Figure 4 As can be seen, the cup 58 is designed to support the bearings 54 , 56 , which ensure the centering and guidance of the cup 58 about the pitch axis “A” relative to the hub 36 of the turbine.

[0084] The bearings 54, 56 may form part of the pitch system 34. In particular, at least one of the guide bearings may have an inner ring of the guide bearing integrated into the cup 58.

[0085] This is also the case for the lower bearing 54, which has its inner ring 54a integrated into the cup 58. In practice, this means that the cup 58 comprises, at its outer periphery, a raceway 54aa on which the balls of the lower bearing 54 roll directly. The raceway comprises an annular surface with a concave curved cross section. The raceway is located at the lower end of the cup 58 and the annular wall 58a. The outer ring 54b of the lower bearing 54 is attached to the hub 36, for example by shrink fitting. Furthermore, advantageously, the cup 58 is designed to apply a preload to the lower bearing 54.

[0086] The outer ring 56b of the upper bearing 56 is attached to the hub 36, for example by shrink fitting. The inner ring 56a of the upper bearing engages on and around the free upper end of the cup 58 and of the annular wall 58a. This end of the annular wall 58a comprises an outer cylindrical surface 76 for mounting the inner ring 56a and an outer thread for screwing on a nut 78 intended to be axially supported on the inner ring 56a to keep it axially clamped on an outer cylindrical shoulder 80 of the cup 58.

[0087] In order to retain the root 14 axially in the cup 58, in particular to resist centrifugal forces, an annular retaining toothing 82 is provided which extends in the cup 58 around the ball 32. The retaining toothing 82 is connected to the cup 58 to at least limit axial displacement relative to the cup 58 towards the opening 58c.

[0088] The retaining toothed ring 82 has an annular bearing surface 84 oriented toward the bottom of the cup 58. The bearing surface 84 is intended to limit the passage cross section of the opening 58c of the cup 58 to prevent the root 14 from being removed through the opening 58c by obstructing the ball 32. More specifically, the bearing surface 84 is intended to be in axial contact with the upper surface 86 of the ball 32 to block the axial displacement of the ball 32 toward the upper opening 58c.

[0089] It is also important to firmly attach the root 14 in the cup 58 to prevent any rotation of the blade 10 relative to the cup 58 during its use. To this end, the angular pitch system 34 comprises a lower seat 88 formed by a face turned towards the opening 58 c of the cup 58, by means of which the root 14 is supported axially in the cup 58 in the direction of the bottom.

[0090] The seat 88 is a separate component from the retaining ring gear 82. At least one of the seat 88 and / or the retaining ring gear 82 is mounted axially movable in translation relative to the cup 58 by means of at least one clamping mechanism 90, so that the ball 32, here made of composite material, is clamped axially between the seat 88 and the bearing surface 84 of the retaining ring gear 82. This makes it possible to prevent axial play between the bearing surface 84 and the blade 10.

[0091] In order for such an axial play not to occur, the spherical portion 32 is clamped between the seat 88 and the bearing surface 84 of the retaining ring gear 82 with a sufficiently high prestress to exceed the maximum axial force that may be applied to the blade 10 during operation of the propeller, for example of the order of tens of kilonewtons, whatever the operating conditions of the propeller.

[0092] The retaining ring gear 82 is made of a metal material, such as steel, titanium, or a titanium alloy (eg, TA6V).

[0093] The seat 88 is made of a metal material such as steel, titanium or a titanium alloy (eg TA6V).

[0094] In order to ensure that the bucket 10 is axially retained in the cup 58 without play, the bearing surface 84 of the retaining ring gear 82 is in direct contact with the spherical portion 32 without the interposition of an insert. In particular, the bearing surface 84 of the retaining ring gear 82 has a shape complementary to the upper surface 86 of the spherical portion 32 to distribute the force over a large area of ​​the spherical portion 32.

[0095] In order to simultaneously enable the root 14 to be radially retained in the cup 58, the upper surface 86 of the bulb 32 has a substantially frustoconical shape and the bearing surface 84 has a complementary shape. The bearing surface 84 extends, for example, substantially from the midplane to the opening 58c of the cup 58. Thus, under the effect of centrifugal forces, the root 14 becomes radially centered in the bearing surface 84. Thus, this shape makes it possible to provide a stable position of the blade 10 relative to the pitch axis "A" during the rotation of the propeller.

[0096] Compared to a broaching attachment, the surface area of ​​the bearing surface 84 is maximized by utilizing the entire circumference of the bottom of the blade 10. In a broaching attachment, only two different surfaces of the root 14 of the blade 10, located on the pressure side and the suction side respectively, are supported on the bearing surface, while the surfaces of the root 14 of the blade 10 located on the leading edge and the trailing edge are free. Furthermore, compared to a broaching attachment, the height of the bearing surface in the direction of the pitch axis "A" is much greater, which also contributes to a significant increase in the surface area of ​​this bearing surface. Such a large bearing surface enables a reduction in the contact pressure under all operating conditions.

[0097] The inner diameter of the retaining toothed ring 82 measured at the upper end of the bearing surface 84 is substantially smaller than the diameter of the middle cross section of the spherical part 32. In order to enable the retaining toothed ring to be arranged around the spherical part 32 in a simple manner, the retaining toothed ring 82 is made of a plurality of sections. Figure 4 Two of the plurality of segments 82a, 82b are shown. The segments 82a, 82b are evenly distributed around the pitch axis "A".

[0098] These segments 82a, 82b may be in circumferential contact with one another, such that the bearing surface 84 has a continuous annular shape.

[0099] In a variant described in detail below, the segments 82 a , 82 b are circumferentially spaced apart from one another, so that the bearing surface 84 has an annular shape having a discontinuity between the two segments 82 a , 82 b .

[0100] The root 14 is supported on the seat 88 by the lower surface 92 of the bulb 32. The seat 88 is thus in the form of an annular support surface extending around the pitch axis "A". In particular, the seat 88 conforms to the lower surface 92 opposite the bulb 32, in particular making it possible to reduce the contact pressure between the seat 88 and the bulb 32. The seat 88 is in direct contact with the root 14, which is here made of composite material.

[0101] In order to enable the bottom of the root 14 to be centered in the cup 58, the lower surface 92 of the ball 32 in contact with the seat 88 has a generally frustoconical shape (here a convex frustoconical shape), and the seat 88 has a complementary shape. Thus, the root 14 is not only axially supported toward the bottom of the cup 58, but is also held radially in place in the cup 58.

[0102] Alternatively, the seat abuts against the lower surface of the free end of the root.

[0103] exist Figure 4 In the example shown, the seat 88 is supported by at least one additional part in the cup 58. The seat 88 is thus inserted between the root 14 and the cup 58. The seat 88 is mounted so as to be movable in translation by means of at least one clamping mechanism 90.

[0104] Here, the seat 88 is formed by the upper surface of an integrally made ring 94. The seat 88 is intended to be supported on the lower annular surface of the spherical portion 32. In this regard, the seat 88 has a continuous annular shape centered on the pitch axis "A".

[0105] The ring 94 bearing the seat 88 is mounted axially supported towards the bottom of the cup 58 by means of a clamping ring 96 belonging to the clamping mechanism 90 . The clamping ring 96 surrounds the seat 88 .

[0106] The clamping ring 96 has an outer peripheral edge 98 which is supported on an annular shoulder surface 100 of the cup 58. The shoulder surface 100 extends radially inwardly from the annular wall 58a and towards the opening 58c. The shoulder surface is located slightly above the median plane Pm.

[0107] The clamping ring 96 is intended to cooperate with the ring 94 to clamp the seat 88 axially upwards on the ball 32 by virtue of the ring being supported on the shoulder surface 100. To this end, the clamping ring 96 is fixed in axial displacement to an internal thread screwed onto a complementary external thread made on the outer surface of the ring 94.

[0108] In order to enable the seat 88 to be clamped on the ball 32 by turning the clamping ring 96 , the external thread or one of the external threads is blocked from rotating relative to the cup 58 .

[0109] As a non-limiting example, this refers to an internal thread. In this respect, the clamping ring 96 is fixed against rotation relative to the cup 58 in particular by nesting complementary shapes between the clamping ring 96 and the cup 58, for example by means of a plate or a pin.

[0110] exist Figure 4 In the example shown, the external thread is made integrally with the seat 88 .

[0111] In a variant that is not shown, the external thread is formed by a ring that is fitted to the annulus and is axially fixed to the seat. The ring is for example rotatably mounted around the annulus.

[0112] Furthermore, a retaining toothed ring 82 is fitted to the cup 58. The retaining toothed ring is made of a plurality of different segments 82a, 82b, which are intended to be axially connected to the cup 58 by means of a dog clutch. To facilitate the insertion of the segments 82a, 82b, the retaining toothed ring 82 is made of at least three segments, Figure 4 Only two of the at least three segments are shown.

[0113] Thus, each segment 82a, 82b comprises at least one external claw tooth 102 configured to cooperate with a complementary internal claw tooth 104 of the annular wall 58a of the cup 58. For example, the external claw teeth 102 each have an angular extension of between about 20° and 30° around the pitch axis "A".

[0114] The internal claw teeth 104 of the cup 58 are evenly spaced around the pitch axis "A". In the non-limiting example shown there are six internal claw teeth. For example, each of the internal claw teeth has an angular extension between about 20° and 30° around the pitch axis "A".

[0115] The external claw teeth 102 are complementary to the internal claw teeth 104 and are configured to cooperate with these internal claw teeth 104 by claw engagement. Claw engagement is a well-known mounting method in the aerospace field and will be described in more detail below.

[0116] When installing the assembly formed by the blade 10 and the pitch system 34, the ring 94 carrying the seat 88 is first inserted into the cup 58 through the upper opening 58c of the cup. The ring 94 is pre-tightened with the clamping ring 96 of the ring so that the seat 88 occupies its lowest position in the cup 58 when the ring 96 is pressed against the shoulder surface 100. The ring 94 and the clamping ring 96 of the ring are positioned so that the edge 98 of the clamping ring 96 is supported on the shoulder surface 100 of the cup 58.

[0117] Then, the root 14 is inserted with its free end 28 through the upper opening 58c of the cup 58. The root 14 is positioned so that the ball 32 bears on the seat 88.

[0118] Then, the segments 82a, 82b of the retaining tooth ring 82 are inserted into the cup 58 through the upper opening 58c of the cup. This insertion is facilitated by the seat 88 being in the lowest position of the seat. This provides sufficient space for the external claw teeth 102 to be inserted between the internal claw teeth 104 without being hindered by the ball 32.

[0119] The external claw teeth 102 of the segments 82a, 82b are arranged to coincide axially with the angled spaces between the internal claw teeth 104. Then, the external teeth 102 of each segment 82a, 82b are inserted axially downward into these spaces to be below the level of the internal claw teeth 104. Finally, the segments 82a, 82b are rotated about the pitch axis "A" until the external claw teeth 102 are axially aligned with the internal claw teeth 104. Thus, the segments 82a, 82b of the retaining gear ring 82 are limited in axial displacement toward the opening 58c by the contact of the external claw teeth 102 of the segments with the internal claw teeth 104 of the cup 58.

[0120] Subsequently, the clamping mechanism 90 is operated so that the seat 88 can be clamped axially on the ball 32. This has the effect of raising the root 14 relative to the cup 58 towards the upper opening 58c of the cup, until the ball 32 is axially supported on the bearing surface 84 of the retaining toothed ring 82. The clamping force is thus transmitted from the seat 88 to the ball 32, then from the ball 32 to the retaining toothed ring 82, and from the retaining toothed ring 82 to the cup 58 via the claw teeth 102, 104. A reaction force is generated between the clamping ring 96 and the cup 58 by the shoulder surface 100. The root 14 is therefore in direct contact only with the bearing surface 84 of the retaining toothed ring 82 and the seat 88 of the ring 94.

[0121] In order to actuate the clamping mechanism 90, a spacing is left angularly between at least two segments 82a, 82b of the retaining toothed ring 82, so that a clamping tool (not shown) can be inserted through the upper opening 58c. Here, clamping is performed by a tool comprising at least one pinion inserted into the cup 58. The pinion is intended to mesh with an external toothing 106 carried by the periphery of the seat 88. The external toothing 106 is here arranged just above the clamping ring 96.

[0122] Figure 5 A first embodiment of the invention is shown, in which elements already described above are referred to with the same reference numerals.

[0123] The bottom wall 58 b is configured to cooperate in a form-fitting manner with the free end 28 of the root 14 , so that the cup 58 is rotationally fixed to the root 14 about the pitch axis “A”, constituting the pivot of the associated blade 10 .

[0124] exist Figure 5In the illustrated embodiment, the bottom wall 58b includes a protrusion 200 configured to engage the free end 28 of the root in a recess 202 of complementary shape.

[0125] In the example shown, it can be seen that the protrusion 200 and the recess 202 are offset from the axis A, thereby enabling keying during installation.

[0126] Figure 6 The bottom wall 58 b comprises a protrusion 200 configured to engage the free end 28 in a recess 202 of complementary shape, the protrusion 200 and the recess 202 being centered on the axis A.

[0127] The recess 202 may be formed in a metallic material portion of the root 14, for example in a metallic insert of the root or in the end of the spar 22 when the spar 22 is made of metal. Alternatively, the recess 202 may be formed in a composite material portion of the root 14, in particular in the spar 22.

[0128] Preferably, the cross section of the protrusion 200 is smaller than the cross sections of the bulbous portion 32 and the pillar 30. The cross section of the pillar 30 is smaller than the cross section of the bulbous portion 32.

[0129] 7 a to 7 i show different possible cross-sectional shapes of the recess 202 and the protrusion 200 .

[0130] In FIG. 7 a , the shape is oval or elliptical, for example with two flat sides diametrically opposite about the axis A. In FIG.

[0131] In FIG. 7 b , the shape is a star, wherein one or more legs of the star are replaced by a rectangular portion.

[0132] In FIG. 7c , the shape is shown as a star.

[0133] In FIG. 7 d , the shape is star-shaped, but this star has an internal cross section that varies along the axis A and in particular decreases.

[0134] In FIGS. 7e to 7g , the shape is polygonal, more precisely, in FIG. 7e , the shape is sun-shaped, in FIG. 7f , the shape is hexagonal, and in FIG. 7g , the shape is square.

[0135] In FIG. 7h , the shape is circular or elliptical.

[0136] And, the shape is the same as in Figure 7i, but where the ends of the legs are identical in pairs.

[0137] The recess 202 may be made by machining the root 14 or may be obtained directly from the mold without any special reworking.

Claims

1. An assembly for an aircraft turbomachine, comprising a propeller blade (10) and a system (34) for angularly setting the pitch of the blade (10) about an axis called the pitch axis (A), The blade (10) has a root (14) extending from an upper end connected to a blade (12) of the blade (10) to a free lower end (28), the root (14) having a convex section called a "bulb (32)", The system (34) for angularly setting the pitch of the blade (10) comprises a cup (58) radially delimited by an annular wall (58a) extending around the pitch axis (A), the cup (58) comprising a lower bottom and an upper opening (58c), the lower bottom being closed by a bottom wall (58b), the spherical portion (32) being intended to be axially inserted into the cup (58) through the upper opening, the bottom wall (58b) being configured to cooperate in a form-fitting manner with the free end (28) of the root (14) so ​​that the cup (58) is secured against rotation relative to the root (14) around the pitch axis (A), It is characterized in that The bottom wall (58b) comprises a protrusion (200) extending along the pitch axis (A) and engaging to the free end (28) of the root (14) in a recess (202) of complementary shape.

2. The assembly according to claim 1, characterized in that The recess (202) and the protrusion (200) are eccentric relative to the pitch axis (A).

3. The assembly according to claim 1, characterized in that The recess (202) and the protrusion (200) are centered about the pitch axis (A).

4. The assembly according to any one of claims 1 to 3, characterized in that The recess (202) is formed in a metallic material portion of the root (14).

5. The assembly according to any one of claims 1 to 3, characterized in that The recess (202) is formed in a composite material portion of the root (14).

6. Assembly according to any one of the preceding claims, characterized in that The cross-sectional shapes of the recess (202) and the protrusion (200) are selected from an ellipse, a star, a cross and a polygon.

7. Assembly according to any one of the preceding claims, characterized in that The cross section of the protrusion (200) is smaller than the cross section of the spherical portion (32).

8. Assembly according to any one of the preceding claims, characterized in that The bulb (32) is connected to the blade (12) via a support (30) having a cross-section smaller than that of the bulb (32).

9. Assembly according to the preceding claim, characterized in that The cross-section of the protrusion (200) is smaller than the cross-section of the pillar (30).

10. Assembly according to any one of the preceding claims, characterized in that The bulb (32) has a circular and convex cross-section that completely surrounds the pitch axis (A).

11. Assembly according to any one of the preceding claims, characterized in that The bulb (32) is connected to the blade (12) via a support (30) having a cross-section smaller than that of the bulb (32).

12. Assembly according to the preceding claim, characterized in that The cross-section of the protrusion (200) is smaller than the cross-section of the pillar (30).

13. Assembly according to any one of the preceding claims, characterized in that The cross section of the protrusion (200) is smaller than the cross section of the spherical portion (32).

14. An aircraft turbomachine comprising an assembly according to any one of the preceding claims.

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