An aircraft turbine engine including variable pitch propeller blades

Abstract

A system (34) for controlling the pitch of a propeller blade (10) of a turboprop engine of an aircraft is disclosed, characterized in that it comprises a cup (58) comprising an annular wall (58a) extending around an axis (A) serving as an axis of pitch setting of the blade, and a bottom wall (58b) configured to cooperate in a shape-matched manner with a free end (28) of said root (14), so as to prevent the cup (58) from rotating with respect to the root (14) around the axis (A), and a fixing ring (52, 52') configured to be mounted inside the cup (58) and to cooperate with the root (14) and with the annular wall (58a) of the cup (58), respectively, so as to ensure the axial retention of the root (14) in the cup (58).

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aircraft turbine engines, in particular to the propulsive propellers of these turbine engines comprising variable-pitch blades. BACKGROUND

[0002] The prior art includes documents FR-A1-3017163, US-A1-1,573,000, US-A-2,017,505 and FR-A1-3080322.

[0003] Aircraft turbine engine propellers can be ducted (for example in the case of fans) or non-ducted (for example in the case of open-rotor structures).

[0004] The propellers comprise blades whose pitch is variable. The turbine engine then comprises a mechanism that makes it possible to vary the pitch angle of the blades, thereby adapting the thrust produced by the propeller to different phases of flight.

[0005] The design of a propeller blade involves several disciplines whose objectives are generally in conflict. This design must make it possible to achieve optimal aerodynamic performance (i.e. to provide thrust while maximizing efficiency), guarantee the mechanical strength of the blade (i.e. to withstand the mechanical constraints resulting from static and dynamic loads), while limiting the mass and acoustic signature. In particular, the improvement of the aerodynamic performance of a propeller tends to increase the By Pass Ratio (BPR), which translates into an increase in the outer diameter of the propeller, and thus in the span of the blades.

[0006] At the same time, in some turbine engine structures, the engine is started with a very open pitch (called feathered). Indeed, this start position makes it possible for the power to be consumed by the torque, which ensures the safety of the machine by guaranteeing a low propeller speed. More precisely, according to a simple consideration, the power is proportional to the product of the speed and the torque. However, the torque increases with the increase in the angle of attack, where the angle of attack can be increased by the pitch. Indeed, the skilled person in the field of aerodynamics understands that, in a first approximation, the resultant force on a blade profile is perpendicular to the chord, which can be decomposed into two components: a thrust along the engine axis and a drag of the blade in the plane of the propeller. Thus, as the pitch of the blades increases, the resultant force shifts towards the plane of the propeller, increasing the drag of the aerodynamic profile and reducing the thrust.

[0007] Thus, in the case of a feathered start, the propeller generates zero thrust, the torque is maximum and the speed is minimum. However, the angle of attack becomes so high that the blades are subjected to a highly lifted aerodynamic flow that is turbulent, generating strong vibratory excitations. This excitation is broadband due to the small vortices of the lifting area, and it is strong at certain specific frequencies due to the large amount of Karman recirculation, which causes the aerodynamic forces to oscillate significantly. In particular, on large chord and large span blades, which generate a large amount of drag, these forces are large even if the speed is not high.

[0008] In the current technology, it is common practice to attach the blades to their support by means of an attachment piece, called a brochee attachment piece. The blade comprises a root having a generally dovetail shape and intended to engage in a matching shape in a slot cavity of the support, which is generally manufactured by broaching.

[0009] For blades with a brochee attachment piece, this aerodynamic force is so strong that it can cause rigid solid movements of the blade root in its slot cavity, similar to rotations. During feathered start, the reduced speed of the fan makes it impossible to generate sufficient centrifugal force to prevent these movements caused by the aerodynamic forces. This results in frictional damage to the blade and to the shims inserted between the root and the bottom of the slot cavity in just a few cycles. For the same reason, this problem can occur in the case of windmill training after engine failure, since variable-pitch blades are generally equipped with a feathering system.

[0010] In addition, at higher rotation speeds, strong vibratory excitations also occur on unducted structures, due to the effect of the installation of the engine on the aircraft and the direction of the upstream infinite flow. Indeed, the unducted engine is affected by the ground and the fuselage, which, depending on the engine azimuth angle, cause distortions in the feed, the flow rate of the propeller. This results in a vibratory response of the propeller blades at the first engine orders IN, 2N and 3N (possibly higher). On the other hand, in the absence of an inlet sleeve, the direction of the air flowing through the blades is not parallel to the engine shaft. This sideslip angle induces forces called "IP" that induce a vibratory response of the propeller blades at the engine order IN. Similarly, these forces IP can also occur during the climb or approach phases of the aircraft when the air flows through the blades at an angle of attack. These high rotation speed vibratory excitations can cause the same frictional damage as described above if the attachment piece of the blade is not suitable.

[0011] For all these reasons, the brochee attachment piece is not a viable solution for variable-pitch, large chord and large span propeller blades.

[0012] There is therefore a need for an attachment technique of variable-pitch propeller blades that makes it possible to limit the rotation of the blades during all the flight phases that can excite blade vibration modes. SUMMARY

[0013] According to a first aspect, the application relates to a variable-pitch propeller blade for aeronautical turbomachines, said blade comprising a blade connected to a root comprising a main body housed in an annular barrel extending around a pitch axis of the blade,

[0014] characterized in that said main body comprises:

[0015] - a free end located on the side opposite the blade, configured to cooperate with a system for controlling the pitch of the blade, and comprising a cross section called low section having a non-circular shape and a value Sb,

[0016] - a strut located on the side of the blade, comprising a cross section called high section having a value Sh, and

[0017] - a bulb located between the free end and the strut, comprising a cross section called intermediate section having a maximum value Sm greater than Sh and Sb,

[0018] and in that said barrel is connected to said main body and covers and adapts to at least part of the bulb and of the strut, said barrel having a shape that is crosswise complementary to the bulb at the intermediate section and to the strut at the high section.

[0019] In the present application, a cross section is defined as a section perpendicular to the pitch axis of the blade. The bulb is a convex or dome-shaped portion, i.e. in this case the bulb comprises a convexity or dome extending around the pitch axis.

[0020] The application thus proposes a blade equipped with an improved root particularly adapted to limit the risk of the above-mentioned rotation.

[0021] The uniqueness of the blade root is particularly associated with the combination of a bulb of large cross section enabling optimal retention of the blade along its axis, and a strut of smaller cross section limiting the risk of aerodynamic perturbation of the air flow flowing through the blade and close to its root during operation.

[0022] Compared to current broached connectors, the present invention makes it possible to limit premature wear of the blade during the flight phases that can excite the vibration modes of the blade. In addition, the blade root is very advantageous in terms of overall size and aerodynamic profile fineness.

[0023] The blade according to the invention can comprise one or more of the following features, used alone or in combination with each other:

[0024] - the low section is eccentric with respect to the pitch axis;

[0025] - the low section is elliptical, oblong, rectangular, square, etc.

[0026] - the intermediate section has a circular shape; alternatively, the intermediate section has a non-circular shape, such as elliptical, oblong, rectangular, square, etc.

[0027] - the high section has a non-circular shape;

[0028] - the high section is elliptical, oblong, rectangular, square, etc.

[0029] - the barrel is made of two shell halves, mounted and attached to the main body, the shell halves being joined at a joining plane passing through the pitch axis;

[0030] - the barrel is glued to the main body;

[0031] - at least one shrink-fit ring is mounted around the shell halves, to keep the shell halves fastened against the main body, the shrink-fit ring extending around the pitch axis;

[0032] - a lower shrink-fit ring is mounted on the low cylindrical surface of the barrel and extends around at least part of the free end of the main body;

[0033] - an upper shrink-fit ring is mounted on the high cylindrical surface of the barrel and extends around part of the bulb of the main body;

[0034] - a claw-shaped joining ring extends around the pitch axis and is captive mounted around the strut between the bulb and the blade, the claw-shaped joining ring comprising external claw-shaped teeth configured to cooperate with the system;

[0035] - the claw-shaped joining ring is configured to be mounted on the high cylindrical surface of the barrel.

[0036] The invention also relates to an assembly comprising a blade as described above and a system for controlling the pitch setting of this blade, wherein the system comprises at least two rolling guide bearings, which extend around the pitch axis.

[0037] Advantageously, the first guide bearing is located between the low section and the intermediate section or at the junction between the free end of the body and the bulb, and the second guide bearing is located between the intermediate section and the high or at the junction between the bulb and the strut.

[0038] Preferably, said first guide bearing extends at least partially around said lower shrink-fit ring, and said second guide bearing extends at least partially around said upper shrink-fit ring.

[0039] The guide bearings receive the mechanical action resulting from the aerodynamic and centrifugal forces exerted on the paddle during operation. The lower bearing can be configured to ensure the centrifugal retention of the paddle, and the upper bearing can be configured to receive the bending moment resulting from the aerodynamic and centrifugal forces. The distance between the bearings along the pitch axis generates a sufficient lever action to prevent the paddle from rotating at any stage of flight.

[0040] Advantageously, the system comprises a cup extending around the pitch axis and interposed between the barrel and the guide bearings, the cup comprising a bottom wall extending transversely to the axis, and the bottom wall having a recess for receiving the free end of the body, the recess having at said low section a shape complementary in section to the free end.

[0041] Preferably, said cup comprises internal claw teeth configured to cooperate with external claw teeth of said claw engagement ring.

[0042] The invention also relates to a turbomachine, in particular for an aircraft, comprising at least one paddle as described above or at least one assembly as described above. According to a second aspect, the invention relates to a system for controlling the pitch setting of a propeller paddle of a turbomachine of an aircraft, characterized in that it comprises:

[0043] - a cup comprising an annular wall extending around an axis serving as a pitch axis of the paddle, the annular wall comprising a lower axial end closed by a bottom wall and comprising an upper axial end which is open and configured so that the root of the paddle is mounted within the cup, the bottom wall being configured to cooperate in a shape-matched manner with the free end of the root so that the cup is rotationally fixed to the root around the axis, and

[0044] - a fixing ring extending around the axis and configured to surround the root, the fixing ring being configured to be mounted within the cup and to cooperate respectively with the root and the annular wall of the cup to ensure the axial retention of the root within the cup.

[0045] The present invention thus proposes a system particularly adapted to facilitate the mounting and dismounting of a propeller blade.

[0046] The system according to the invention can comprise one or more of the following features, used separately or in combination with each other:

[0047] - the system further comprises:

[0048] - a lower rolling guide bearing extending around the axis and mounted around a lower portion of the annular wall,

[0049] - an upper rolling guide bearing extending around the axis and mounted around an upper portion of the annular wall;

[0050] - at least one of the guide bearings integrates its inner ring into the cup.

[0051] - at least one of the guide bearings is angularly contacted;

[0052] - the bottom wall comprises a recess having a non-circular cross-section and configured to receive a free end of a root of the blade.

[0053] - the recess is eccentric with respect to the pitch axis;

[0054] - the system further comprises an elastically deformable member extending around the pitch axis and mounted within the cup, the member being axially supported on the bottom wall and configured to axially bias the root of the blade towards the outside of the cup;

[0055] - the fixing ring is a clawed engagement ring comprising external clawed teeth configured to cooperate with complementary internal clawed teeth of the annular wall of the cup;

[0056] - the system further comprises a locking ring and an annular snap ring, the locking ring being configured to axially engage between the internal and external clawed teeth to prevent rotation of the clawed engagement ring within the cup, and the annular snap ring being mounted within the cup to axially block the locking ring within the cup;

[0057] - the cross-section of the fixing ring is wedge-shaped and the ring is configured to be biased axially outwards from the cup under the effect of centrifugal force during operation, and to keep the blade root axially clamped by a wedge effect.

[0058] The present application also relates to an assembly comprising the aforementioned system and a variable-pitch propeller blade, said blade comprising a blade connected to a root, said root comprising a body housed in an annular barrel, said annular barrel extending around a pitch axis of the blade.

[0059] The present application also relates to a turbine engine, in particular for an aircraft, comprising at least one system as described above or at least one assembly as described above.

[0060] The present application finally relates to a method for mounting the aforementioned assembly, wherein said method comprises the following steps:

[0061] by inserting the root of the blade into the cup of the system in a direction parallel to the pitch axis,

[0062] by engaging the free end of the root in a recess in the bottom wall of the cup to rotationally fix the cup to the root of the blade, and

[0063] by engaging a fixing ring, which is pre-mounted or provided around the root of the blade, in the cup and mounting said ring in the cup and on the root of the blade to ensure the axial retention of the root in the cup.

[0064] Advantageously, during said steps a) and / or b), the root of the blade is supported on the elastically deformable member and compresses the elastically deformable member in the axial direction.

[0065] Preferably, during said step c), the fixing ring is mounted into the cup by a claw engagement. BRIEF DESCRIPTION OF DRAWINGS

[0066] Further features and advantages will become apparent from the following description of non-limiting embodiments of the application, with reference to the appended drawings, in which:

[0067] [ Figure 1 ] Figure 1 is a schematic perspective view of a propeller blade for a turbine engine of an aircraft and shows the present application,

[0068] [ Figure 2 ] Figure 2 is an enlarged view of a part of Figure 1 and shows the root of the blade,

[0069] [ Figure 3 ] Figure 3 is a schematic perspective view of a partial exploded view of the root of the blade of Figure 1 ,

[0070] [ Figure 4 ] Figure 4 isFigure 1 a schematic perspective view of the blade root body in

[0071] [ Figure 5 ] Figure 5 is a further schematic axial sectional view of the blade root and of the guide bearing of Figure 1 , the sectional plane extending transversely to the chord of the blade vane,

[0072] [ Figure 6 ] Figure 6 is a schematic axial sectional view of the blade root of Figure 1 , the sectional plane extending transversely to the chord of the blade vane,

[0073] [ Figure 7 ] Figure 7 is a further schematic cross-sectional view along the line VII-VII of Figure 5 ,

[0074] [ Figure 8 ] Figure 8 is a schematic axial sectional view of the blade root of Figure 1 , and an embodiment of a system for controlling the pitch setting of the blade according to the invention,

[0075] [ Figure 9 ] Figure 9 is a schematic perspective view of the cup of the system in Figure 8 ,

[0076] [ Figure 10 ] Figure 10 is a schematic perspective view of the claw-shaped engagement ring of the system in Figure 8 ,

[0077] [ Figure 11 ] Figure 11 is a schematic perspective view of the locking ring of the system in Figure 8 ,

[0078] [ Figure 12 ] Figure 12 is a schematic perspective view of the blade root and of a partial axial section of the system in Figure 8 , and shows a first mounting step,

[0079] [ Figure 13 ] Figure 13 is a schematic perspective view of the blade root and of a partial axial section of the system in Figure 8 , and shows a second mounting step,

[0080] [ Figure 14 ] Figure 14 is a schematic perspective view of the blade root and of a partial axial section of the system in Figure 8a schematic perspective view of a partial axial section of the blade root and of the system, and showing a third mounting step,

[0081] [ Figure 15 ] Figure 15 is Figure 8 a schematic perspective view of a partial axial section of the blade root and of the system, and showing a fourth mounting step,

[0082] [ Figure 16 ] Figure 16 is Figure 8 a schematic perspective view of a partial axial section of the blade root and of the system, and showing a fifth mounting step,

[0083] [ Figure 17 ] Figure 17 is Figure 8 a schematic perspective view of a partial axial section of the blade root and of the system, and showing a sixth mounting step, and

[0084] [ Figure 18 ] Figure 18 is Figure 1 a schematic axial section view of the blade root, and of an alternative embodiment of the system for controlling the pitch setting of the blade according to the application. DETAILED DESCRIPTION

[0085] Figure 1 A blade 10 of a propeller for aeronautical turbomotors is shown, which is either ducted or unducted.

[0086] The blade 10 comprises a blade 12 connected to a root 14.

[0087] The blade 12 has an aerodynamic profile and comprises a camber 12a and a deck 12b connected by an upstream leading edge 12c and a downstream trailing edge 12d, the terms “upstream” and “downstream” referring to the gas flow around the blade in operation.

[0088] The blade 12 has a free upper end, known as tip, and a lower end connected to the root 14.

[0089] In the example shown, the blade 10 is made of composite material by means of an injection method known as Resin Transfer Molding (RTM). This method comprises the preparation of a fibrous preform 18 by three-dimensional weaving, which is then placed in a mould and a polymerizable resin, for example an epoxy resin, is injected, which will impregnate the preform. After curing and hardening of the blade 12, its leading edge 12c is usually reinforced by a metal sheath 20, which is mounted and attached, for example by gluing.

[0090] The blade 10 here comprises a spar 22 comprising a part forming the core of the blade 12 and intended to be inserted into the preform 18 before resin injection, and a part extending from the side opposite the tip of the blade 14 to form a part of the root 14, referred to as the main body 24.

[0091] The spar 22 is preferably made of 3D woven carbon fiber reinforced epoxy organic matrix composite, with the warp direction oriented mainly radially and the weft oriented mainly along the blade chord at the aerodynamic envelope height. However, the spar can also be a component made of a different organic matrix composite (thermoset, thermoplastic or elastomer) reinforced with long fibers (carbon, glass, aramid, polypropylene) in different fiber arrangements (woven, braided, knitted, unidirectional) that are more mechanically advantageous.

[0092] Although not shown, the blade 12 can be hollow or solid and comprise an internal cavity filled with a foam or honeycomb type filler. This filler is mounted around the spar 22 and covered with a skin of organic matrix composite to increase the impact resistance of the blade.

[0093] The shroud 20 can be of titanium or titanium alloy, stainless steel, steel, aluminum, nickel, etc. The concave 12a or even the convex 12b of the blade 12 can be covered with a polyurethane film to prevent erosion.

[0094] The root 14 essentially comprises two parts, namely the main body 24 and an annular cylinder 26 extending around the main body and the blade axis A.

[0095] The axis A is the elongation axis of the blade 10 and of the blade 12, in particular the pitch axis of the blade, i.e. the axis around which the angular position of the blade is adjusted. This axis is also generally the radial axis and thus extends radially from the rotation axis of the propeller equipped with this blade.

[0096] The main body 24 of the root 14 has a particular shape best seen in Figures 3 to 7 .

[0097] The main body 24 essentially comprises three parts:

[0098] - a free end 28 located on the side opposite the blade 12,

[0099] - a strut 30 located on the blade side, and

[0100] - a bulb 32 located between the free end and the strut.

[0101] In the example shown, the free end 28 has a substantially parallelepiped shape. As in Figure 7As can be seen, the end 28 is offset from the axis A to implement a détrompage or indexage, which will be explained in more detail below.

[0102] Pb is defined as a transverse plane, i.e. a plane perpendicular to the axis A, which plane Pb passes approximately through the middle of the end 28, measured along the axis A. This plane Pb is referred to as a low plane or lower plane. Figure 7 The cross-sectional shape of the end 28 in this plane Pb is shown. This cross-section, referred to as a low cross-section, has a value or surface area (e.g. maximum value) denoted Sb, and is generally rectangular in the example shown.

[0103] As will also be described below, the end 28 is configured to cooperate with a system 34 for controlling the pitch setting of the blade.

[0104] The strut 30 has a relatively complex shape, and can be considered to comprise:

[0105] - two lateral flanks 30a, 30b, which are located on one side of the intrados 12a and extrados 12b of the blade 12 respectively, the two lateral flanks converging towards each other along the axis A and in the direction of the tip of the blade 12 (see Figure 4 and Figure 6 ), and

[0106] - two edges, which are respectively an upstream edge 30c and a downstream edge 30d, the two edges diverging from each other along the axis A and in the direction of the tip of the blade 12 (see Figure 4 and Figure 5 ).

[0107] Ph is defined as a transverse plane passing through the strut 30, in particular the lower end of the strut. This plane Ph is referred to as a high plane or upper plane. In this plane, the strut can have a non-circular shape in cross-section, for example an elliptical, oblong, square or rectangular shape. This cross-section, referred to as a high cross-section, has a value or surface area (e.g. maximum value) denoted Sh.

[0108] The bulb 32 has a generally convex or dome shape, which convexity or dome extends around the axis A.

[0109] Pm is defined as a median plane passing through the bulb 32, in particular in the part of maximum cross-section of the bulb 32, denoted Sm. This plane Pm is referred to as an average plane. In this plane, the bulb 32 can have a circular shape in cross-section, although this is not limiting.

[0110] It is understood that the plane Pm is situated between the planes Pb and Ph. The cross section of the bulb 32 decreases from the plane Pm (Sm) to the plane Ph and from the plane Pm to the plane Pb. It is thus understood that Sm is greater than Sb and Sh. Moreover, in the example shown, Sh is greater than Sb.

[0111] As seen in Figure 3 The barrel 26 is made in two shell halves 26a, 26b which are mounted and attached to the body 24, for example one shell half on the concave side 12a of the blade and the other shell half on the convex side 12b of the blade 12. The shell halves 26a, 26b are thus joined at a joining plane which passes through the axis A and extends substantially parallel to the chord of the blade 12.

[0112] The barrel 26 is preferably attached to the body 24 by gluing. The glue extends between the barrel and the body around the axis A.

[0113] The barrel 26 is preferably metallic (steel, titanium or a titanium alloy such as TA6V). The glue is for example an epoxy glue filled with thermoplastic or elastomeric masses or reinforced by a fabric. This gluing method is particularly suitable because the contact surface area between the cavity of the barrel and the body, which can be composite, is large. The presence of a glue joint is advantageous because it makes it possible to correct slight shape defects. The glue joint also makes it possible to prevent friction at the metal / composite interface, thereby increasing the service life of the paddle.

[0114] Several possibilities are envisaged for fitting the barrel 26 onto the body 24. A first possibility is to deliberately leave a gap between the two shell halves 26a, 26b once they have been fitted, so that the pressure can be applied appropriately when the glue joint is cured. The curing stage can be carried out in an autoclave, in which the entire paddle is in a vacuum bag. However, it is also possible to perform this operation in a press. However, the drawback of leaving a gap between the two shell halves 26a, 26b is that the positioning of the two shell halves is less controlled and it is therefore necessary to rework the outer surface. A second possibility is to fit the shell halves around the body with one shell half against the other, without any existing gap. This strategy is possible, for example, by machining a blank which has been cut into two parts and which is held together during the machining operation, so as to ensure the geometry of the outer surface once the shell halves have been reassembled. This makes it possible to control the positioning and geometry of the outer surface of the barrel 26 without the need for additional machining after gluing. In either case, it is possible to consider positioning pins or stops to ensure the relative position of the shell halves of the barrel.

[0115] However, the presence of an adhesive joint between the body and the barrel is not mandatory, although it is very advantageous. Alternatively, a prestressed washer (or spring) can be used between the barrel and the composite body in order to push the body radially against the bearing surface of the barrel. The geometry of the barrel can also be used to slightly "clamp" the body when the two shell halves of the barrel are mounted around the bulb. In this case, it is the deformation of the barrel that creates the prestress. Therefore, a tool must be provided to maintain this position before final assembly.

[0116] As can be seen in Figure 5 and Figure 6 , the barrel 26 covers and fits at least part of the bulb 32 and of the strut 30, and has a shape that is complementary in section to the bulb 32 at the intermediate section Sm and to the strut 30 at the high section Sh.

[0117] More particularly, in the example shown, the barrel 26 comprises three parts,

[0118] - a lower end 36, which is generally annular in shape (see Figures 5 to 7 ), and which extends at and around the free end 28 of the root,

[0119] - an upper end 38, which extends at the plane Ph and comprises two lateral lips 40 that are applied to the flanks 30a, 30b of the strut 30, and

[0120] - an intermediate part 42, which is applied to the bulb 32 and closely fits the shape of the bulb.

[0121] The lips 40 are supported on the flanks 30a, 30b of the strut 30 and make it possible to stiffen the root 14 of the blade and to increase its resistance to torsion about the pitch axis A.

[0122] Furthermore, the lips described above make it possible to absorb energy in the event of an impact on the blade 10, for example ingestion of a bird. Fillets can be present on these lips in order to prevent local wear or damage to the body.

[0123] The inner surface of the barrel 26 that is in contact with the body 24 serves as a bearing surface. The bearing surface is maximized by using the entire circumference of the blade bottom, compared with a broached attachment. In a broached attachment, only two different surfaces of the blade root, respectively on the soffit and on the intrados, are supported on the bearing surface, while the surfaces of the blade root on the leading edge and on the trailing edge are free. The height of the bearing surface in the radial direction is also much greater, compared with a broached attachment, which also contributes to a significant increase in the surface area of the bearing surface. This large support surface makes it possible to reduce the contact pressure under all operating conditions.

[0124] The barrel 26 comprises two cylindrical surfaces 44, 46a for mounting shrink-fit rings 48, 50. The shrink-fit rings 48, 50 make it possible to hold the shell halves 26a, 26b fastened to each other and to the main body 24. The shrink-fit rings 48, 50 extend around the axis A.

[0125] The surface 44 is located on the lower end 36 and is oriented radially outward with respect to the axis A. This surface receives by shrink-fit a ring 48 which is engaged from below and axially supported on a cylindrical bearing surface located at the junction of the end 36 and the intermediate portion 42 of the barrel 26.

[0126] The surface 46a is located on the intermediate portion 42 and is oriented radially outward with respect to the axis A. This surface receives by shrink-fit a ring 50 which is engaged from above and axially supported on a cylindrical bearing surface located in the vicinity of the plane Pm.

[0127] It can be seen that the surface 46a is located immediately adjacent to a cylindrical surface 46b for receiving a fixing ring 52, as will be described below.

[0128] In the example shown, the surfaces 44, 46a and the rings 48, 50 have different diameters. The diameter of the surface 46a is greater than that of the surface 44, and therefore the diameter of the ring 50 is greater than that of the ring 48.

[0129] The surfaces 46a, 46b can have the same or different diameters. For example, the surface 46b can have a diameter slightly smaller than that of the surface 46a. This is particularly the case in the event that the ring 50 should be mounted with a predetermined radial clearance with respect to this surface 46b.

[0130] From Figure 5 and Figure 6 It can be seen that the ring 50 is located between the planes Ph and Pm, and the ring 48 is located between the planes Pm and Ps.

[0131] Figure 5 and Figure 6 The positions of the rings 48, 50 and the planes Pm, Ph, Ps with respect to the rolling bearings 54, 56 are also shown, the rolling bearings 54, 56 extending around the axis A and the root 14.

[0132] The bearings 54, 56 are two in number here and are respectively a lower bearing 54 and an upper bearing.

[0133] The bearings 54, 56 are of the ball rolling type. In the example shown, these bearings have different diameters, and the balls of these bearings also have different diameters.

[0134] The bearing 54 extends substantially between the planes Pm and Pb and thereby around the lower portion of the bulb 32. It also extends around the ring 48. This bearing 54 has a smaller diameter than the other bearing 56 and its balls have a larger diameter than the balls of the other bearing 56.

[0135] The bearing 54 is also angularly contacted. In the example shown, the support points or surfaces of the balls on the raceways of its rings 54a, 54b are located on a frustoconical surface S1 which extends along the axis A and whose largest diameter is located on the side of the blade tip.

[0136] The bearing 56 extends substantially between the planes Pm and Ph and thereby around the upper portion of the bulb 32. It also extends around the ring 50. The bearing 56 is also angularly contacted. In the example shown, the support points or surfaces of the balls on the raceways of its rings 56a, 56b are located on a frustoconical surface S2 which extends along the axis A and whose largest diameter is located on the side of the free end of the blade root.

[0137] The position of the median section between the two bearings 54, 56 is very advantageous in terms of radial overall dimensions, since a portion of the height of the bearing surface between the median section and the high section is located inside the cup 58, unlike the prior art with a broached connection integrated in the pivot. This contributes to reducing the radial overall dimensions of the control system 34.

[0138] Figures 8 to 17 A first embodiment of the system, in particular of the fixing ring 52, is shown, and Figure 18 An alternative embodiment of the system and of the ring is shown.

[0139] The system 34 comprises a cup 58 comprising an annular wall 58a extending around the axis A. This wall 58a comprises a lower axial end closed by a bottom wall 58b and an upper axial end which is open and is configured so as to enable the root 14 of the blade to be mounted inside the cup.

[0140] The bottom wall 58b is configured to cooperate in a shape-matched manner with the free end of the root 14 and thereby with the end 28 of the body 24, so as to make the cup rotationally fixed to the root around the axis.

[0141] In this case, it is understood that the bottom wall 58b comprises a recess 60 having a non-circular, in particular rectangular, cross section and configured to receive the end 28 Figure 8 ) of the body 24. As Figure 5As shown, the recess 60 is eccentric with respect to the axis A in a similar manner as the end portion 28 (see Figure 7 ). This eccentricity enables a turning and rotational adjustment when inserting and mounting the root portion into the cup 58, so that only one engagement position of the end portion 28 in the recess 60 is possible.

[0142] The recess 60 is located on the upper or inner surface of the bottom wall 58b of the cup 58, so it is located inside the cup and oriented towards the root portion.

[0143] The system 34 generates a torque at the blade root portion that counteracts the torsional moment generated by the aerodynamic and centrifugal forces. The end portion 28 of the root portion 14 can be enclosed in the barrel 26 like the rest of the body 24 of the root portion 14. In this case, this end portion 28 will also have a non-circular shape to limit its rotation. However, to directly limit the rotation of the body, it is advantageous, as mentioned above, to make this end portion of the body protrude from the barrel. This provides a more direct force path, so that the torsional moment is applied directly to the body. The low cross-section is strictly smaller than the maximum dimension of the intermediate cross-section, to limit the overall circumference dimension at this height. As a result, the overall circumference dimension of the barrel at this height is also smaller than at the intermediate cross-section. This makes it possible to reduce the diameter of the lower bearing located below the intermediate cross-section. Thus, the blade root portion can be integrated radially lower, which greatly reduces the theoretical hub ratio associated with the integration of the root portion. It is known to the person skilled in the art that a low hub ratio improves the performance of the engine, in particular because the engine is more compact and therefore lighter. This last point is a very important advantage of this technical solution compared to competitors, who generally propose barrels with a cylindrical external shape.

[0144] The bottom wall 58b comprises a lower or outer surface located on the opposite side of the root portion 14 and comprising a cylindrical extension 62 extending along the axis A and comprising an external thread or external straight spline 64 for the rotational coupling of the system with a pitch change mechanism, not shown, and common to the different systems 34 and blades 10 of the propeller.

[0145] An elastically deformable member 66, such as a helical spring, extends around the axis A and is mounted inside the cup 58. This member 66 is axially supported on the upper surface of the bottom wall 58b, on the outer periphery of this surface in the example shown, and is configured to axially bias the blade root portion towards the outside of the cup, i.e. towards the side of the blade tip.

[0146] The member 66 is supported on a cylindrical support surface 68 of the barrel 26. In the example shown, the member 66 is centred by engaging its upper end on and around a cylindrical edge 70 of the barrel and by engaging its lower end on and around a cylindrical edge 72 of the cup at the outer periphery of the bottom wall 58b.

[0147] The member 66 extends here around the shrink-fit ring 48.

[0148] As can be seen in Figure 8 The cup 58 is designed to support the bearings 54, 56 which ensure the centring and guiding of the cup around the axis A, relative to the housing 74 or to the fixed structure of the turbine engine, as can be seen in

[0149] The bearings 54, 56 can be part of a control system. In particular, at least one of the guide bearings can integrate its inner ring into the cup.

[0150] This is the case for the lower bearing 54, the inner ring 54a of which is integrated into the cup 58. In practice, this means that the cup comprises at its outer periphery a raceway 54aa on which the balls of the bearing 54 roll directly. This raceway comprises an annular surface with a concave curved section. This raceway is located at the lower end of the cup and of the wall 58a. The outer ring 54b of the bearing 54 is attached, for example by shrink fitting, to the housing 74. Furthermore, the cup 58 is advantageously designed to exert a prestress on the bearing 54.

[0151] The outer ring 56b of the bearing 56 is attached, for example by shrink fitting, to the housing 74. The inner ring 56a of the bearing 56 engages on and around the free upper end of the cup 58 and of the wall 58a. This end of the wall 58a comprises an outer cylindrical surface 76 for mounting the inner ring 56a and an outer thread for screwing on a nut 78 for axially supporting on the inner ring 56a to keep it axially tightly against an outer cylindrical shoulder 80 of the cup 58.

[0152] The wall 58a of the cup further comprises at its inner periphery a part configured to cooperate with the aforementioned fixing ring 52.

[0153] The fixing ring 52 extends around the axis A and is configured to be mounted around the root 14. This fixing ring 52 is configured to be mounted inside the cup and to cooperate with the annular wall 58a of the cup 58 and with the root 14 respectively, to ensure the axial retention of the root inside the cup.

[0154] In Figures 8 to 17In the embodiment of FIG. 1, the retaining ring 52 is a crabbing ring that includes external crabbing teeth 84 configured to cooperate with complementary internal crabbing teeth 82 of the annular wall 58a of the cup 58.

[0155] The teeth 82 of the cup 58 are best seen in Figure 9 . These teeth are evenly spaced about the axis A. In the non-limiting example shown there are six teeth. Each of these teeth has, for example, an angular extent of between about 20° to 30° about the axis A.

[0156] Each tooth 82 includes at its inner periphery a circumferentially oriented groove 86 relative to the axis A. The grooves 86 of the teeth 82 form discontinuous valleys about the axis A.

[0157] The crabbing ring is best seen in Figure 10 . The teeth 84 of the crabbing ring are regularly spaced about the axis A. In the non-limiting example shown there are six teeth. Each of these teeth has, for example, an angular extent of between about 20° to 30° about the axis A.

[0158] The teeth 84 are complementary to the teeth 82 and cooperate with these teeth by crabbing. Crabbing is a mounting method well known in the aviation field and will be explained by reference to the Figures 12 to 17 .

[0159] The ring 52 includes an internal cylindrical surface 52a for cooperating by sliding with the aforementioned surface 76 of the cup 58.

[0160] The ring 52 includes a second set of teeth 88 extending axially upward on the side of the tip of the blade 10. These teeth 88 are also regularly spaced about the axis A. In the example shown there are six such teeth. These teeth can be staggered relative to the teeth 84, i.e. the circumferential spacing between the teeth 88 and the teeth 84 is axially aligned. As a non-limiting example, the teeth 88 each have an angular extent of between about 10° to 20° about the axis A.

[0161] Each tooth 88 includes at its inner periphery a circumferentially oriented groove 90 relative to the axis A. The grooves 90 of the teeth 88 form discontinuous valleys about the axis A.

[0162] Figure 11 A locking ring 92 is shown configured to axially engage between the crabbing teeth 82, 84 to prevent rotation of the ring 52 within the cup 58.

[0163] The ring 92 includes rails 94 (in the non-limiting example shown, there are six rails 94) for engaging in the intertooth spaces extending between the teeth 82 and 84. It will be appreciated, therefore, that these rails 94 have a shape complementary to that of the spaces, and are regularly spaced around the axis A.

[0164] In the example shown, the rails 94 are secured to one another by bridges 96 extending circumferentially between the rails 94. There are five bridges 96, and each bridge 96 extends between two adjacent rails 94. The two rails 94 are deliberately not connected together by a bridge, so that the ring 92 is open. This can simplify assembly when installing the ring in the system 34, by allowing the rails to be moved away from or towards one another.

[0165] Each rail 94 includes a groove 98 at its inner periphery, oriented circumferentially with respect to the axis A. The grooves 98 of the rails 94 form a discontinuous valley around the axis A.

[0166] The system also includes a ring snap ring 100, visible in Figure 17 .

[0167] The snap ring 100 is installed in the cup 58 to axially block the locking ring 92 in the cup 58. The snap ring 100 can also be split or open to facilitate its installation, and is used to engage in the grooves 86 of the teeth 82 of the cup and in the grooves 98 of the rails 94 of the ring 92 when the grooves 86, 98 are both located in the same plane perpendicular to the axis A and circumferentially arranged with respect to one another to form a complete valley around the axis A (see Figure 16 and Figure 17 ).

[0168] Reference is now made to Figures 12 to 17 , Figures 12 to 17 a method for installing an assembly formed by the paddle 10 shown in Figure 1 and the system 34 shown in Figure 8 .

[0169] In a first step shown in Figure 12 , the root 14 of the paddle 10 is engaged in the cup 58 of the system 34 by axial translation along the axis A until the end 28 of the root body 24 engages in the recess 60 of the cup 58. As can be seen in the figures, the shrink-fit ring has been snap-fitted around the strut 30 of the root body. Although not shown in this figure, the member 66( Figure 8 ) is compressed when the root 14 is inserted into the cup 58.

[0170] In a second step shown in Figure 12 and Figure 13In the second step shown, the shrink fit ring is angularly positioned about the axis A so that its teeth 84 are aligned with the spaces between the teeth 82 of the cup. Then, the ring 52 is axially translated displaced within the cup 58 until the ring 52 engages on the surface 46b of the barrel 26 and the teeth 84 are just below the teeth 82, as shown. Figure 13 The grooves 90 provided on the teeth can be used to grip the ring 52 by a suitable tool.

[0171] In Figure 13 and Figure 14 the third step shown, the ring 52 is angularly rotated displaced about the axis A so that the teeth 82, 84 are axially aligned with each other. This angular displacement is about 25° to 30° due to the angular extension of the teeth in the example shown. The teeth 88 can be used to grip the ring 52 and rotate it by the aforementioned tool. The member 66 (not shown) biases the root axially outwardly from the cup so that the teeth 84 axially support on the teeth 82. Thus, the root is axially retained within the cup and the system 34. In operation, the centrifugal forces exerted on the paddle are transmitted to the cup 58 through the teeth 82, 84, which are directly received by the bearing 54, wherein the inner ring 54a of the bearing 54 is integrated into the cup 58.

[0172] In Figure 15 and Figure 16 the fourth step shown, the ring 92 is angularly positioned about the axis A so that its slides 94 are aligned with the spaces between the teeth 82, 84. Then, the ring 92 is axially translated displaced within the cup 58 until the slides 94 engage in these spaces. Then, the bridges 96 can be supported on the teeth 84 of the ring 52. Thus, the ring 92 prevents any rotation of the ring 52 within the cup 58.

[0173] In Figure 17 the last step shown, the snap ring 100 engages in the grooves 86, 98 which are circumferentially aligned with each other. The snap ring 100 prevents the accidental disassembly of the ring 92.

[0174] It is understood that the disassembly of the paddle is performed by executing the steps described above in the reverse order. It is also understood that one of the essential steps for the installation and disassembly of the root is the fixation of the ring 52. This ring 52 can be manipulated from the outside of the turbine engine, which is particularly advantageous during maintenance operations. By disassembling and removing a minimum number of parts, the paddle can be disassembled and removed from the propeller.

[0175] Referring to Figure 18 , Figure 18An alternative embodiment of a retaining ring 52' is shown. The ring 52' is wedge-shaped in cross section and is configured to be biased axially outwardly from the cup 58 under centrifugal force during operation and to maintain the blade root 14 axially clamped by the wedge effect.

[0176] In the example shown, the axial semi-cross section of the ring 52' is substantially trapezoidal and comprises a lower surface 102 and two lateral surfaces, respectively an inner lateral surface 104 and an outer lateral surface 106. The surfaces 102 to 106 are annular and extend around the axis A.

[0177] A ring 52 ′ surrounds the root 14 and engages inside the cup, and this ring 52 ′ is supported axially on the shrink-fit ring 50 by its surface 102 , here by means of a washer 108 .

[0178] The outer surface 106 of the ring cooperates, by support and axial sliding, with a complementary ring 110 mounted inside the cup and around the ring 52 ′.

[0179] The ring 52 ′ is segmented and is formed by a plurality of segments arranged at a circumferential distance from one another around the axis A. By way of example, there are six segments evenly distributed around the axis A.

[0180] Finally, the nut 112 is screwed onto the internal thread of the upper end of the cup 58 and cooperates with the inner surface 104 of the ring 52 ′ by support and axial sliding.

[0181] The tightening and tightening of the nut 112 causes an axial displacement of the segments of the ring 52' bearing on the washer 108 and a radial biasing of these segments against the complementary-shaped ring 110. Any mounting play is then eliminated.

[0182] The barrel 26 comprises a cylindrical shoulder 114 which bears against a complementary cylindrical shoulder 116 of the cup 58, here at the junction between the middle portion 42 and the lower end of the barrel 26. The advantages of this variant are in particular the reception of the centrifugal forces to achieve retention of the blade, and also the replacement of the previously described member 66 by applying a direct prestress between the barrel 26 (and therefore the root 14 of the blade) and the inner ring 54a of the bearing 54.

[0183] Other variant embodiments not shown are possible, including:

[0184] The shell halves 26a, 26b of the cylinder 26 can be mounted to the main body 24 by bolting, riveting, welding, etc.;

[0185] • The adhesive used to connect the barrel 26 to the body 24 can be an epoxy adhesive, but it can also be an elastomeric or thermoplastic adhesive. A non-stick film can also be used to enable relative movement while limiting wear due to friction;

[0186] • Still on the problem of the barrel / body interface, the various technical solutions in the proposed solutions (gluing, pre-stressing through gaskets or springs, pre-stressing through the geometry of the barrel) can also be combined together; these solutions can be combined regardless of the presence of a gap between the two parts of the barrel;

[0187] • Although less advantageous, the radial position of the bearing used to ensure the centrifugal retention of the paddle can be opposite to that of the bearing used to absorb the bending moment, which is generated by the aerodynamic and centrifugal forces.

Claims

1. A system (34) for controlling the pitch setting of a propeller blade (10) of an aircraft turbine engine, characterized in that The system comprises: a cup (58) comprising an annular wall (58a) extending about an axis (A) serving as the pitch axis of the blade, the annular wall (58a) comprising a lower axial end closed by a bottom wall (58b) and an upper axial end, the upper axial end being open and configured such that the root (14) of the blade (10) fits inside the cup (58), the bottom wall (58b) being configured to cooperate in a form-fitting manner with the free end (28) of the root (14) such that the cup (58) is rotationally fixed to the root (14) about the axis (A), and - a fixing ring (52, 52') extending around the axis (A) and configured to be mounted around the root (14), the fixing ring (52, 52') configured to be mounted inside the cup (58) and to cooperate with the annular wall (58a) of the root (14) and the cup (58), respectively, to ensure axial retention of the root (14) inside the cup (58).

2. The system (34) of claim 1, wherein: The system further comprises: a lower rolling guide bearing (54) extending around said axis (A) and mounted around a lower portion of said annular wall (58a), - an upper rolling guide bearing (56) extending around said axis (A) and mounted around an upper portion of said annular wall (58a).

3. The system (34) of claim 2, wherein: At least one of the lower rolling guide bearing (54) and the upper rolling guide bearing (56) has an inner ring (54a, 56a) integral with the cup (58).

4. The system (34) according to claim 2 or 3, wherein: At least one of the lower rolling guide bearing (54) and the upper rolling guide bearing (56) is in angular contact.

5. The system (34) according to any one of claims 1 to 3, wherein: The bottom wall (58b) includes a recess (60) having a non-circular cross-section and configured to receive the free end (28) of the root (14) of the blade (10).

6. The system (34) of claim 5, wherein: The recess (60) is eccentric relative to the pitch axis (A).

7. The system (34) according to any one of claims 1 to 3, wherein: The system also includes an elastically deformable member (66) extending about the pitch axis (A) and mounted within the cup (58), the elastically deformable member (66) being axially supported on the bottom wall (58b) and configured to axially bias the root (14) of the blade (10) toward the exterior of the cup (58).

8. The system (34) according to any one of claims 1 to 3, wherein: The retaining ring (52) is a claw-engaging ring including external claw teeth (84) configured to cooperate with internal claw teeth (82) of the annular wall (58a) of the cup (58), the external claw teeth (84) being complementary to the internal claw teeth (82).

9. The system (34) of claim 8, wherein: The system also includes a locking ring (92) and an annular snap ring (100), wherein the locking ring (92) is configured to axially engage between the inner claw teeth (82) and the outer claw teeth (84) to prevent rotation of the claw engagement ring (52) within the cup (58), and the annular snap ring (100) is mounted within the cup (58) to axially block the locking ring (92) within the cup (58).

10. The system (34) according to any one of claims 1 to 3, wherein: The fixing ring (52') is wedge-shaped in cross section and is configured to be biased axially toward the outside of the cup (58) under the action of centrifugal force during operation and to keep the root (14) of the blade axially clamped by a wedge effect.

11. An assembly comprising a system (34) according to any one of claims 1 to 10 and a variable pitch propeller blade (10), the blade (10) comprising a blade (12) connected to a root (14), the root (14) comprising a body (24) housed in an annular cylinder (26) extending around the pitch axis (A) of the blade.

12. A turbine engine for an aircraft, comprising at least one system (34) according to any one of claims 1 to 10 or an assembly according to claim 11.

13. A method for installing an assembly according to claim 11, wherein: The method comprises the following steps: a) inserting the root (14) of the blade (10) into the cup (58) of the system (34) by displacing the blade (10) in a direction parallel to the pitch axis (A), b) engaging the free end (28) of the root (14) in a recess (60) in the bottom wall (58b) of the cup (58) to rotationally secure the cup (58) to the root (14) of the blade (10), and c) engaging the fixing ring (52, 52') previously mounted or arranged around the root (14) of the blade (10) in the cup (58) and installing the fixing ring (52, 52') in the cup (58) and on the root (14) of the blade (10) to ensure axial retention of the root (14) in the cup (58).

14. The method of claim 13, the system (34) being as defined in claim 6 and further comprising an elastically deformable member (66), wherein During steps a) and / or b), the root (14) of the blade (10) is supported on the elastically deformable member (66) and axially compresses the elastically deformable member.

15. The method according to claim 13 or 14, the system (34) being a system as defined in claim 8 or 9, wherein: During step c), the fixing ring (52) is mounted in the cup (58) by means of claw engagement.

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