FR3112820A1 - AIRCRAFT TURBOMACHINE WITH VARIABLE-PITCHED PROPELLER BLADE - Google Patents

Abstract

System (34) for controlling the angular setting of a propeller blade (10), for an aircraft turbine engine, characterized in that it comprises: - a bowl (58) comprising an annular wall (58a) s' extending around an axis (A) intended to be a wedging axis of the blade, and a bottom wall (58b) configured to cooperate by complementarity of shapes with a free end (28) of said root (14) in such a way so that the bowl (58) is integral in rotation with the foot (14) around said axis (A), and - an immobilization ring (52, 52') which is configured to be mounted inside the bowl (58) and to cooperate respectively with the foot (14) and the annular wall (58a) of the bowl (58) in order to ensure the axial retention of the foot (14) in the bowl (58). Figure for abstract: Figure 8

Description

AIRCRAFT TURBOMACHINE COMPRISING VARIABLE-PITCHED PROPELLER BLADE

Technical field of the invention

The present invention relates to the field of aircraft turbomachines and in particular the propulsion propellers of these turbomachines which include variable-pitch blades.

Technical background

The state of the art includes in particular documents FR-A1-3 017 163 and FR-A1-3 080 322.

An aircraft turbomachine propeller can be shrouded, as is the case with a fan for example, or not shrouded, as is the case with an architecture of the open-rotor type for example.

A propeller includes blades which can be variable pitch. The turbomachine then comprises a mechanism making it possible to modify the pitch angle of the blades in order to adapt the thrust generated by the propeller according to the different phases of flight.

The design of a propeller blade involves several disciplines whose objectives are generally antagonistic. It must allow optimal aerodynamic performance (i.e. provide thrust while maximizing efficiency), guarantee mechanical strength of the blade (i.e. withstand the mechanical stresses resulting from static and dynamic loads ) while limiting the mass as well as the acoustic signature. In particular, the improvement in the aerodynamic performance of the propeller tends towards an increase in the BPR ( By Pass Ratio ), which results in an increase in its external diameter and therefore in the span of the blades.

At the same time, on certain turbomachine architectures, the engine start is performed at a very open, so-called feathered, timing. Indeed, this starting position allows the power to be consumed by the torque, which ensures machine safety by guaranteeing low propeller speeds. More precisely, according to simple considerations, power is proportional to the product of rpm and torque. However, the torque increases with the angle of attack which can be increased via the setting. Indeed, those skilled in the art of aerodynamics understand that the resulting force on a blade profile is, as a first approximation, perpendicular to the chord and can be broken down into two components: the thrust along the engine axis and the drag of the blade. in the plane of the helix. Thus, with the increase in the pitch of the blades, the resulting force moves towards the propeller plane, which has the effect of increasing the drag of the aerodynamic profile and reducing the thrust.

Therefore, in the case of a feather start, the thrust generated by the propeller is zero, the torque is maximum and the rpm minimum. However, the angle of attack becomes so great that the blades then undergo a strongly separated turbulent aerodynamic flow which generates a strong vibratory excitation. This excitation is both broadband due to the small vortices of the separated zone, but also intense on certain particular frequencies due to the large recirculations of Karman which cause the aerodynamic force to oscillate significantly. In particular, on wide chord and large span blades which generate a lot of drag, this effort is intense although the RPM is not high.

In the current technique, it is common to fix a blade to its support by a so-called broached attachment. The blade comprises a foot which has a general dovetail shape and which is intended to be engaged by complementarity of shapes in a cell of the support, this cell being conventionally made by broaching.

For a blade with pinned attachment, this aerodynamic force is so intense that it can cause movements of the rigid solid of the blade root in its cell which are similar to swiveling. Indeed, during a feathered start, the reduced speed of the fan does not make it possible to generate a centrifugal force sufficient to prevent these movements induced by the aerodynamic force. This results in damage by friction of the blade and of the spacer inserted between the foot and the bottom of the cell, in just a few cycles. For the same reasons, this problem may arise in a situation of freewheeling (or “ windmilling ”) following an engine failure because variable-pitch blades are generally equipped with a feathering system.

In addition, intense vibrational excitation can also occur at much higher rotational speeds on unducted architectures due to engine installation effects on the aircraft and the direction of the infinite flow upstream. Indeed, a non-ducted engine is subject to the influence of the ground and the fuselage, which causes a distortion in the power supply to the propeller, in flow velocity, depending on the engine azimuths. This leads to a vibratory response of the propeller blades on the first engine orders 1N, 2N and 3N (possibly more). On the other hand, in the absence of an air intake sleeve, the direction of the air flowing through the blades is not parallel to the motor axis. This sideslip angle leads to so-called “1P” forces which cause a vibratory response of the propeller blades on the 1N engine command. In a similar way, these 1P forces can also appear during the phases of climbs or approach of the aircraft because the air flows through the blades with an angle of incidence. These vibratory excitations at high rotational speeds can cause the same damage by friction mentioned above if the blade attachment is not suitable.

For all of these reasons, the pinned attachment is not a viable solution for variable-pitch, wide-chord, large-span propeller blades.

There is therefore a need for a technology for attaching a variable-pitch propeller blade which makes it possible to limit the swiveling of the blade during all the phases of flight which are likely to excite the vibration modes of the 'dawn.

According to a first aspect, the invention relates to a propeller blade with variable pitch, for an aircraft turbomachine, this blade comprising a blade connected to a root, the root comprising a body housed in an annular shaft which extends around a blade setting axis,

characterized in that the body comprises:

- a free end located on the side opposite the blade, this free end being configured to cooperate with a system for controlling the pitch of the blade, and comprising a cross section, called the low section, which has a non-circular shape and a value sb,

- a stilt located on the side of the blade, this stilt comprising a cross section, called the high section, which has a value Sh, and

- a bulb located between the free end and the stilt, this bulb comprising a cross section, called the middle section, which has a maximum value Sm which is greater than Sh and Sb,

and in that the barrel is fixed to the body and covers and hugs at least a part of the bulb and of the stilt, the barrel having a shape complementary in section to the bulb, at the level of said middle section, and to the stilt , at said upper section.

In the present application, by cross-section is meant a section perpendicular to the pitch axis of the blade. Bulb is understood to mean a swollen or domed part, i.e. comprising a bulge or a bulge which extends around the wedging axis in the case in point.

The invention thus proposes a blade equipped with an improved foot particularly suitable for limiting the risks of swiveling mentioned above.

The particularity of the root of the blade is linked in particular to the combination of a bulb of large cross-section which allows optimum retention of the blade along its axis, and of a butt of smaller cross-section which limits the risk of aerodynamic disturbance of the air flow crossing the blade and flowing close to its root in operation.

Compared to the current pinned attachment, the invention makes it possible to limit the premature wear of the blade during the flight phases which are likely to excite the vibration modes of the blade. Furthermore, the blade root is very advantageous in terms of size and thinness of the aerodynamic profile.

The blade according to the invention may comprise one or more of the following characteristics, taken separately from each other, or in combination with each other:

- the lower section is eccentric with respect to the wedging axis;

-- the bottom section has oval, oblong, rectangular, square, etc. ;

- the middle section has a circular shape; alternatively, the middle section has a non-circular shape and for example oval, oblong, rectangular, square, etc. ;

- the upper section has a non-circular shape;

-- the high section has oval, oblong, rectangular, square, etc. ;

- the barrel is made of two half-shells attached and fixed to the body, the half-shells being joined at a joint plane which passes through said wedging axis;

- the barrel is glued to the body;

- at least one hooping ring is mounted around the half-shells to keep them tight against the body, this hooping ring extending around the wedging axis;

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

- an upper shrink ring is mounted on a high cylindrical surface of the barrel, and extends around part of the bulb of the body;

- a dog clutch ring extends around the setting axis and is mounted captive around the stilt, between the bulb and the blade, this dog clutch ring comprising external dog clutch teeth configured to cooperate with said system;

- the dog clutch ring is configured to be mounted on the upper cylindrical surface of the barrel.

The present invention also relates to an assembly comprising a blade as described above and a system for controlling the timing of this blade, in which the system comprises at least two rolling guide bearings, which extend around the axis gap.

Advantageously, a first guide bearing is located between the lower and middle sections or at the junction between the free end and the bulb of the body, and a second guide bearing is located between the middle and upper sections or at the junction between the bulb and stilt.

Preferably, the first guide bearing extends at least partially around the lower shrink ring, and the second guide bearing extends at least partially around the upper shrink ring.

The guide bearings take up the mechanical actions resulting from the aerodynamic and centrifugal forces applied to the blade in operation. The lower bearing can be configured to ensure the retention of the centrifugal blade and the upper bearing can be configured to ensure the absorption of bending moments resulting from aerodynamic and centrifugal forces. The distance between the bearings, along the pitch axis, generates a sufficient lever arm to prevent the blade from rotating, whatever the phase of flight.

Advantageously, the system comprises a bowl extending around the wedging axis and inserted between the barrel and the guide bearings, this bowl comprising a bottom wall which extends transversely to the axis and which has a recess of reception of the free end of the body, this recess having a shape complementary in section to this free end, at the level of said lower section.

Preferably, the bowl comprises internal dog teeth configured to cooperate with the external dog teeth of said dog clutch ring.

The present invention also relates to a turbomachine, in particular for an aircraft, comprising at least one blade or at least one assembly as described above.

According to a second aspect, the invention relates to a system for controlling the angular pitch of a propeller blade, for an aircraft turbine engine, characterized in that it comprises:

- a bowl comprising an annular wall extending around an axis intended to be a wedging axis of the blade, this annular wall comprising a lower axial end closed by a bottom wall, and an upper axial end open and configured to allow the mounting of a root of the blade inside the bowl, the bottom wall being configured to cooperate by complementarity of shapes with a free end of said root so that the bowl is integral in rotation with the foot around said axis, and

- an immobilization ring which extends around said axis and which is configured to be mounted around the foot, this immobilization ring being configured to be mounted inside the bowl and to cooperate respectively with the foot and the wall ring of the bowl to ensure axial retention of the foot in the bowl.

The invention thus proposes a system particularly suitable for facilitating the assembly and disassembly of a propeller blade.

The system according to the invention may comprise one or more of the following characteristics, taken separately from each other, or in combination with each other:

- the system also includes:

- a lower rolling guide bearing extending around said axis and mounted around a lower part of the annular wall,

- an upper rolling guide bearing extending around said axis and mounted around an upper part of the annular wall;

- at least one of the guide bearings has its internal ring which is integrated into said bowl.

- at least one of the guide bearings is in angular contact;

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

- the recess is eccentric with respect to the wedging axis;

- the system further comprises an elastically deformable member extending around the wedging axis and mounted inside the bowl, this member bearing axially on the bottom wall and being configured to axially urge the foot of the vane out of the bowl;

- the immobilization ring is a dog clutch ring which comprises external dog teeth configured to cooperate with internal dog teeth complementary to the annular wall of the bowl;

- the system further comprises a locking ring and an annular ring, the locking ring being configured to be engaged axially between the internal and external teeth of the dog clutch to prevent rotation of the dog clutch ring inside the bowl, and the annular ring being mounted in the bowl to axially block the locking ring in the bowl;

- the immobilisation ring has a wedge-shaped cross-section and is configured, under the effect of centrifugal forces in operation, to be axially biased towards the outside of the bowl and to hold the blade root axially tight by effect corner.

The present invention also relates to an assembly comprising a system as described above and a variable-pitch propeller blade, this blade comprising a blade connected to a root, the root comprising a body housed in an annular shaft which extends around a blade setting axis.

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

The present invention finally relates to a method for assembling an assembly as described above, in which it comprises the steps of:

a) insertion of the root of the blade inside the bowl of the system, by moving the blade in a direction parallel to the pitch axis,

b) engagement of a free end of the root in a recess in the bottom wall of the bowl so as to secure the bowl in rotation with the root of the blade, and

c) engagement of the immobilization ring, previously mounted or present around the root of the blade, in the bowl and mounting of this ring in the bowl and on the root of the blade so as to ensure the axial retention of the root in the bowl.

Advantageously, during steps a) and/or b), the root of the blade bears against the elastically deformable member and compresses it axially.

Preferably, during step c), the immobilizing ring is mounted in the bowl by dog clutching.

Brief description of figures

Other characteristics and advantages will emerge from the following description of a non-limiting embodiment of the invention with reference to the appended drawings in which:

Figure 1 is a schematic perspective view of a propeller blade for an aircraft turbine engine, and illustrates the present invention,

figure 2 is a view on a larger scale of part of figure 1 and shows the root of the blade,

Figure 3 is a schematic perspective view with partial exploded view of the root of the blade of Figure 1,

Figure 4 is a schematic perspective view of the body of the root of the blade of Figure 1,

FIG. 5 is another schematic view in axial section of the root of the blade of FIG. 1 and of guide bearings, the section plane extending along a chord of the blade of the blade,

FIG. 6 is a diagrammatic view in axial section of the root of the blade of FIG. 1 and of the guide bearings, the section plane extending transversely to the chord of the blade of the blade,

Figure 7 is another schematic sectional view along line VII-VII of Figure 5,

FIG. 8 is a diagrammatic view in axial section of the root of the blade of FIG. 1 and of an embodiment of a system according to the invention for controlling the angular setting of this blade,

Figure 9 is a schematic perspective view of a bowl of the system of Figure 8,

Figure 10 is a schematic perspective view of a clutch ring of the system of Figure 8,

Figure 11 is a schematic perspective view of a locking ring of the system of Figure 8,

FIG. 12 is a schematic view in perspective and in partial axial section of the root of the blade and of the system of FIG. 8, and shows a first assembly step,

FIG. 13 is a schematic view in perspective and in partial axial section of the root of the blade and of the system of FIG. 8, and shows a second assembly step,

FIG. 14 is a schematic view in perspective and in partial axial section of the root of the blade and of the system of FIG. 8, and shows a third assembly step,

FIG. 15 is a schematic view in perspective and in partial axial section of the root of the blade and of the system of FIG. 8, and shows a fourth assembly step,

FIG. 16 is a schematic view in perspective and in partial axial section of the root of the blade and of the system of FIG. 8, and shows a fifth assembly step,

FIG. 17 is a schematic view in perspective and in partial axial section of the root of the blade and of the system of FIG. 8, and shows a sixth assembly step, and

FIG. 18 is a diagrammatic view in axial section of the root of the blade of FIG. 1 and of an alternative embodiment of a system according to the invention for controlling the angular setting of this blade.

Detailed description of the invention

FIG. 1 shows a blade 1 for a propeller of an aircraft turbomachine, this propeller being ducted or not ducted.

The dawn 10 comprises a blade 12 connected to a foot 14.

The blade 12 has an aerodynamic profile and comprises a lower surface 12a and a lower surface 12b which are connected by an upstream leading edge 12c and by a downstream trailing edge 12d, the terms upstream and downstream referring to the flow of gases around of the blade in operation.

The blade 12 has an upper end which is free, called tip, and a lower end which is connected to the foot 14.

In the example shown, the blade 10 is made of composite material by an injection process called the RTM process (acronym for Resin Transfer Molding ). This method consists in preparing a fibrous preform 18 by three-dimensional weaving and then in placing this preform in a mold and injecting a polymerizable resin therein, such as an epoxy resin, which will impregnate the preform. After polymerization and hardening of the blade 12, its leading edge 12c is generally reinforced by a metal shield 20 attached and fixed, for example by gluing.

The blade 10 here comprises a spar 22 which comprises a part forming a core of the blade 12 and which is intended to be inserted into the preform 18 before the injection of resin, and a part which extends from the side opposite the tip of the blade 14 to form part of the foot 14, called the body 24.

The spar 22 is preferably made of a composite material with an epoxy organic matrix reinforced with 3D woven carbon fibers with the warp direction mainly oriented radially and the weft mainly oriented along the chord of the blade at the height of the aerodynamic vein. However, the spar can also be a mechanically more advantageous assembly of different composite materials with an organic matrix (thermosetting, thermoplastic or elastomer) reinforced with long fibers (carbon, glass, aramid, polypropylene) according to several fiber arrangements (woven, braided, knitted, unidirectional).

Although not shown, the blade 12 can be hollow or solid and includes an internal cavity filled with a filling material of the foam or honeycomb type. This filler material is installed around the spar 22 and it is covered with a skin of organic matrix composite material to increase the resistance of the blade to impact.

The shield 20 can be titanium or titanium alloy, stainless steel, steel, aluminum, nickel, etc. The intrados 12a or even the extrados 12b of the blade 12 can be covered with a polyurethane film for erosion protection.

The foot 14 essentially comprises two parts, namely this body 24 and an annular shaft 26 which extends around the body and an axis A of the blade.

The axis A is an axis of elongation of the blade 10 and of the blade 12 and in particular a pitch axis of the blade, that is to say the axis around which the angular position of the dawn is adjusted. It is generally also a radial axis which therefore extends along a radius relative to the axis of rotation of the propeller equipped with this blade.

The body 24 of the foot 14 has a particular shape best seen in Figures 3 to 7.

The body 24 essentially comprises three parts, namely:

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

- a stilt 30 located on the side of the blade, and

- a bulb 32 located between the free end and the stilt.

The free end 28 has a generally parallelepipedal shape in the example shown. As can be seen in Figure 7, this end 28 is off-axis or offset relative to axis A to achieve keying or indexing, as will be explained in more detail below.

We define Pb as a transverse plane, that is to say a plane perpendicular to the axis A, passing substantially through the middle of the end 28, measured along the axis A. This plane Pb is called plane low or lower. FIG. 7 shows the shape in section of the end 28 in this plane Pb. This section, called the lower section, has a value or an area, for example maximum, denoted Sb and has a generally rectangular shape in the example represented.

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

The stilt 30 has a relatively complex shape and can be considered to include:

- two lateral flanks 30a, 30b, located respectively on the side of the intrados 12a and the extrados 12b of the blade 12, which converge towards each other along the axis A and in the direction of the top of the blade 12 (see figures 4 and 6), and

- two edges, respectively upstream 30c and downstream 30d, which on the contrary diverge from each other along the axis A and in the direction of the top of the blade 12 (cf. figures 4 and 5).

We define Ph as a transverse plane passing through the stilt 30, and in particular its lower end. This Ph plane is called the high or superior plane. In this plane, the stilt can have a non-circular cross-section and for example oval, oblong, square or rectangular. This section, called the upper section, has a value or an area, for example maximum, denoted Sh.

The bulge 32 has a generally swollen or domed shape, this bulge or bulge extending all around the axis A.

Pm is defined as a median plane passing through the bulb 32, and in particular in its part of greatest cross-section, which is denoted Sm. This Pm plane is called the mean plane. In this plane, the bulb 32 can have a circular section in section although this section is not limiting.

It is understood that the plane Pm is located between the planes Pb and Ph. The cross section of the bulb 32 decreases from the plane Pm (Sm) to the plane Ph, as well as from the plane Pm, to the plane Pb. that Sm is greater than Sb and Sh. Moreover, in the example represented, Sh is greater than Sb.

The barrel 26 is made of two half-shells 26a, 26b, as can be seen in Figure 3, which are attached and fixed to the body 24, for example one on the side of the intrados 12a of the blade and the the other on the side of the extrados 12b of the blade 12. The half-shells 26a, 26b are thus joined at a joint plane which passes through the axis A and which extends substantially parallel to a chord of blade 12.

Barrel 26 is advantageously fixed to body 24, preferably by gluing. The glue extends between the barrel and the body, all around the A axis.

The barrel 26 is preferably metallic (steel, titanium or titanium alloy such as TA6V). The glue is for example an epoxy glue charged with thermoplastic or elastomeric nodules or reinforced with a fabric. This assembly process by bonding is particularly suitable due to the large contact surface between the cavity of the barrel and the body, which can be composite. The presence of a glue joint is advantageous because it makes it possible to compensate for slight defects in shape. The glue joint also prevents friction at the metal/composite interface and therefore increases the life of the blade.

Several possibilities are envisaged for attaching the barrel 26 to the body 24. A first possibility is to deliberately leave a clearance between the two half-shells 26a, 26b of the barrel 26 once attached so as to properly apply the pressure during the polymerization of the glue joint. The polymerization phase can be done in an autoclave with the entire blade inside a vacuum tank. But, it is also possible to carry out this operation in press. However, the disadvantage of leaving a clearance between the two half-shells 26a, 26b is less control over their positioning and therefore having to carry out a re-machining of the outer surface. A second possibility is to bring the half-shells against each other around the body with no existing play. This strategy is possible, for example by machining a blank already cut into two parts and held together during the machining operation in order to ensure the geometry of the external surfaces once the half-shells are reassembled. This makes it possible to control the positioning and the geometry of the outer surface of the barrel 26 without the need for additional machining after bonding. In all cases, positioning pins or stops can be considered to ensure the relative position of the half-shells of the barrel.

The presence of a glue joint between the body and the barrel is however not mandatory although it is very advantageous. An alternative is to use preload washers (or springs) between the shaft and the composite body in order to push the body radially and press it against the shaft bearing surfaces. You can also play on the geometry of the barrel to ensure that the body is slightly "pinched" when the two half-shells of the barrel are attached around the bulb. In this case, it is the deformation of the shaft that generates a prestress. It is therefore necessary to provide tools to maintain this position before final assembly.

As can be seen in Figures 5 and 6, the shaft 26 covers and hugs at least a part of the bulb 32 and of the stilt 30, and has a complementary shape in section of the bulb 32, at the level of the middle section Sm, and of the stilt 30, at the level of the upper section Sh.

More specifically, the barrel 26 comprises three parts in the example shown,

- a lower end 36 which has a generally annular shape (see figures 5-7) and which extends at and around the free end 28 of the foot,

- an upper end 38 which extends at the level of the plane Ph and which comprises two lateral lips 40 applied to the sides 30a, 30b of the stilt 30, and

- A middle part 42 applied to the bulb 32 and closely matching its shape.

The lips 40 rest on the sides 30a, 30b of the stilt 30 and make it possible to stiffen the root 14 of the blade and to reinforce its resistance to torsion around the wedging axis A.

They also make it possible to absorb energy in the event of an impact on the blade 10, such as for example the ingestion of a bird. Fillets may be present on these lips to prevent wear or local damage to the body.

The internal surfaces of the barrel 26 which are in contact with the body 24 serve as bearing surfaces. Compared to a broached attachment, the bearing surface is maximized by exploiting the entire circumference of the bottom of the blade. On a broached attachment, only two distinct surfaces of the blade root, respectively located on the lower surface and on the upper surface, bear against bearing surfaces, whereas the surfaces of the blade root located on the leading edge and on the leakage are free. Still in comparison with a broached attachment, the height of the bearing surfaces in the radial direction is much greater, which also contributes to considerably increasing their surface. This large bearing surface makes it possible to reduce the contact pressure whatever the case of operation.

The barrel 26 comprises two cylindrical surfaces 44, 46a for mounting shrink rings 48, 50. The shrink rings 48, 50 make it possible to hold the half-shells 26a, 26b tight against each other and on the body 24 The shrinking rings 48, 50 extend around the axis A.

The surface 44 is located on the lower end 36 and is oriented radially outwards with respect to the axis A. It receives the ring 48 by shrinking which is engaged from the bottom and bears axially on a cylindrical surface located at the junction of the end 36 and the middle part 42 of the barrel 26.

The surface 46a is located on the middle part 42 and is oriented radially outwards with respect to the axis A. It receives the ring 50 by shrinking which is engaged from the top and bears axially on a cylindrical surface located near of the PM plane.

It can be seen that the surface 46a is located just next to a cylindrical surface 46b which is intended to receive an immobilizing ring 52, as will be described below.

The surfaces 44, 46a, as well as the rings 48, 50, have different diameters in the example shown. Surface 46a has a larger diameter than surface 44 and therefore ring 50 has a larger diameter than ring 48.

The surfaces 46a, 46b can have identical or different diameters. The surface 46b can for example have a diameter slightly smaller than that of the surface 46a. This is particularly the case where the ring 50 should be mounted with a predetermined radial play with respect to this surface 46b.

Figures 5 and 6 show that the ring 50 is located between the Ph and Pm planes, and that the ring 48 is located between the Pm and Ps planes.

Figures 5 and 6 also show the position of the rings 48, 50 and the planes Pm, Ph, Ps with respect to rolling bearings 54, 56 which extend around the axis A and the foot 14.

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

The bearings 54, 56 are of the ball bearing type. In the example shown, they have different diameters and their balls also have different diameters.

The bearing 54 extends substantially between the planes Pm and Pb and therefore around a lower part 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 those of the other bearing 56.

The bearing 54 is also in oblique contact. In the example shown, the bearing points or surfaces of the balls on the raceways of their 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 dawn summit.

The bearing 56 extends substantially between the planes Pm and Ph and therefore around an upper part of the bulb 32. It also extends around the ring 50. The bearing 56 is also in oblique contact. In the example shown, the bearing points or surfaces of the balls on the raceways of their 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 foot of the dawn.

The position of the middle section between the two bearings 54, 56 is very advantageous in terms of radial size because part of the bearing height between the middle section and the upper section is located inside the bowl 58, unlike the state of the art on broached attachments integrated into a pivot. This contributes to reducing the radial size of the control system 34.

Figures 8 to 17 illustrate a first embodiment of the system and in particular of the immobilization ring 52, and Figure 18 illustrates an alternative embodiment of the system and of this ring.

The system 34 comprises a bowl 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 open upper axial end configured to allow mounting from the 14 foot of the dawn inside the bowl.

The bottom wall 58b is configured to cooperate by complementarity of shapes with the free end of the foot 14, and therefore with the end 28 of the body 24, so that the bowl is integral in rotation with the foot around the 'axis.

In the present case, it is understood that the bottom wall 58b comprises a recess 60 having a non-circular cross-section, and in particular rectangular, and configured to receive the end 28 (FIG. 8). As can be seen in FIG. 5, this recess 60 is eccentric with respect to axis A in a similar way to end 28 (cf. FIG. 7). This eccentricity allows indexing and keying when inserting and mounting the foot in the bowl 58, only one position of engagement of the end 28 in the recess 60 being possible.

The recess 60 is located on an upper or inner face of the bottom wall 58b of the bowl 58, which is therefore located inside the bowl and oriented towards the side of the foot.

System 34 generates a torque at the blade root which opposes the twisting moment resulting from aerodynamic forces and centrifugal forces. The end 28 of the foot 14 could be enveloped in the barrel 26, like the rest of the body 24 of the foot 14. In this case, the latter would also have a non-circular shape in order to constrain its rotation. However, it is advantageous to let this end of the body come out of the barrel, as mentioned above, in order to directly constrain the rotation of the body. This results in a more direct force path, with the torque applied directly to the body. The lower section has dimensions strictly smaller than the maximum dimension of the middle section in order to limit the circumferential bulk at this height. As a result, the shaft also has a smaller circumferential bulk at this height than at the middle section. This makes it possible to reduce the diameter of the lower bearing which is located under the middle section. Therefore, the blade root can be integrated lower radially, which greatly reduces the theoretical hub ratio associated with the integration of the root. However, the person skilled in the art knows 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 the technical solution compared to the competition which conventionally offers drums with a cylindrical external shape.

The bottom wall 58b comprises a lower or outer face, which is located on the side opposite the foot 14, and which comprises a cylindrical extension 62 extending along the axis A and comprising an external thread or external rectilinear splines 64 for the rotational coupling of the system with a pitch change mechanism which is not illustrated and which is common to the various systems 34 and blades 10 of the propeller.

An elastically deformable member 66, such as a coil spring, extends around the axis A and is mounted inside the bowl 58. This member 66 bears axially on the upper surface of the bottom wall 58b, at the outer periphery of this surface in the example shown, and is configured to axially urge the root of the blade towards the outside of the bowl, that is to say on the side of the tip of the blade.

The member 66 is supported on a cylindrical surface 68 of the barrel 26. In the example shown, the member 66 is centered by engagement of its upper end on and around a cylindrical rim 70 of the barrel, and by engagement of its lower end on and around a cylindrical flange 72 of the bowl located at the outer periphery of the bottom wall 58b.

The member 66 here extends around the shrink ring 48.

As seen in Figure 8, the bowl 58 is designed to support the bearings 54, 56 which ensure the centering and guidance of the bowl around the axis A vis-à-vis a housing 74 or a fixed structure of the turbomachine.

The bearings 54, 56 can be part of the control system. In particular, at least one of the guide bearings may have its inner ring which is integrated into the bowl.

This is the case here of the lower bearing 54 which has its internal ring 54a integrated into the bowl 58. In practice, this means that the bowl comprises a raceway 54aa at its outer periphery on which the ball bearings of the bearing 54 roll directly. raceway comprises an annular surface with a concave curved section. This raceway is here located at the lower end of the bowl and of the wall 58a. The outer ring 54b of the bearing 54 is fixed to the casing 74, for example by shrink fitting. Furthermore, the bowl 58 is advantageously designed to apply a prestress to the bearing 54.

The outer ring 56b of the bearing 56 is fixed to the casing 74, for example by shrink fitting. Its inner ring 56a is engaged on and around the free upper end of bowl 58 and wall 58a. This end of the wall 58a comprises an outer cylindrical surface 76 for mounting the inner ring 56a as well as an outer thread for screwing a nut 78 intended to bear axially on the inner ring 56a to hold it axially tight against a shoulder external cylindrical 80 of the bowl 58.

The wall 58a of the bowl further comprises at its inner periphery means configured to cooperate with the immobilization ring 52 mentioned above.

The immobilization ring 52 extends around the axis A and is configured to be mounted around the foot 14. This immobilization ring 52 is configured to be mounted inside the bowl and to cooperate respectively with the foot 14 and the annular wall 58a of the bowl 58 in order to ensure the axial retention of the foot in the bowl.

In the embodiment of Figures 8 to 17, this immobilization ring 52 is a dog clutch ring which comprises external dog teeth 84 configured to cooperate with internal dog teeth 82 complementary to the annular wall 58a of the bowl 58.

The teeth 82 of the bowl 58 are better visible in Figure 9. These teeth are regularly spaced around the axis A. They are six in number in the non-limiting example shown. For example, they each have an angular extension around the axis A, comprised between approximately 20 and 30°.

Each of the teeth 82 comprises at its inner periphery a groove 86 oriented circumferentially with respect to the axis A. The grooves 86 of the teeth 82 form a discontinuous groove around the axis A.

The dog clutch ring is better visible in Figure 10. Its teeth 84 are regularly spaced around the axis A. They are six in number in the non-limiting example shown. For example, they each have an angular extension around the axis A, comprised between approximately 20 and 30°.

The teeth 84 are complementary to the teeth 82 and are configured to cooperate by interconnection with these teeth. Dog clutching is a method of assembly well known in the aeronautical field and which will be illustrated by FIGS. 12 to 17 illustrating an assembly method.

The ring 52 comprises an internal cylindrical surface 52a intended to cooperate by sliding with the aforementioned surface 76 of the bowl 58.

The ring 52 comprises a second series of teeth 88, which extend axially upwards, on the side of the tip of the blade 10. These teeth 88 are also regularly spaced around the axis A. They are six in number. in the example shown. They can be arranged in staggered rows vis-à-vis the teeth 84, that is to say that the teeth 88 are aligned axially with the circumferential spaces located between the teeth 84. By way of non-limiting example, the teeth 88 each have an angular extension around the axis A, comprised between approximately 10 and 20°.

Each of the teeth 88 comprises at its inner periphery a groove 90 oriented circumferentially with respect to the axis A. The grooves 90 of the teeth 88 form a discontinuous groove around the axis A.

Figure 11 shows a locking ring 92 which is configured to be axially engaged between dog teeth 82, 84 to prevent rotation of ring 52 within bowl 58.

This ring 92 comprises pads 94, here six in number in the non-limiting example shown, intended to be engaged in the inter-tooth spaces extending between the teeth 82 and 84. It is therefore understood that these pads 94 have shapes complementary to those of these spaces and are regularly spaced around the axis A.

In the example shown, the pads 94 are secured to each other by bridges 96 extending circumferentially between the pads 94. The bridges 96 are five in number and each extend between two adjacent pads 94. Two of the pads 94 are deliberately not connected together by a bridge so that the ring 92 is open. This can simplify assembly by spacing or bringing these pads closer to each other when mounting the ring in the 34 system.

Each of the pads 94 comprises at its inner periphery a groove 98 oriented circumferentially with respect to the axis A. The grooves 98 of the pads 94 form a discontinuous groove around the axis A.

The system further comprises an annular ring 100 which is only visible in Figure 17.

The ring 100 is mounted in the bowl 58 to axially block the locking ring 92 in the bowl 58. The ring 100 can also be split or opened to facilitate its assembly and is intended to be engaged in the grooves 86 of the teeth 82 of the bowl as well as the grooves 98 of the pads 94 of the ring 92, when these grooves 86, 98 are all located in the same plane perpendicular to the axis A and are arranged circumferentially with respect to each other to form a complete groove around of axis A (see figures 16 and 17).

Reference is now made to Figures 12 to 17 which illustrate a method of mounting the assembly formed by a blade 10 as shown in Figure 1 and a system 34 as shown in Figure 8.

In the first step illustrated in FIG. 12, the root 14 of the blade 10 is engaged in the bowl 58 of the system 34 by axial translation along the axis A, until the end 28 of the body 24 of the foot engages in the recess 60 of the bowl 58. As can be seen in the drawing, the hooping ring is already mounted captive around the stilt 30 of the body of the foot. Although it is not represented in this figure, the member 66 (figure 8) is compressed during the insertion of the foot 14 in the bowl 58.

In the second step illustrated by Figures 12 and 13, the shrinking ring is positioned angularly around the axis A so that its teeth 84 are aligned with the spaces located between the teeth 82 of the bowl. The ring 52 is then moved in axial translation inside the bowl 58 until the ring 52 is engaged on the surface 46b of the barrel 26 and the teeth 84 are located just below the teeth 82, as illustrated in Figure 13. The grooves 90 provided on the teeth can be used to grip the ring 52 by a suitable tool.

In the third step illustrated by Figures 13 and 14, the ring 52 is moved in rotation around the axis A so that these teeth 82, 84 are aligned axially with each other. Due to the angular extension of the teeth in the example shown, this angular displacement is here of the order of 25-30°. The teeth 88 can be used to grip the ring 52 and its rotation by the aforementioned tool. The member 66, not shown, axially urges the foot towards the outside of the bowl, which causes the axial support of the teeth 84 on the teeth 82. The foot is thus maintained axially inside the bowl and the system 34 In operation, the centrifugal forces applied to the blade are transmitted by the teeth 82, 84 to the bowl 58, these forces being taken up directly by the bearing 54 whose inner ring 54a is integrated into the bowl 58.

In the fourth step illustrated by Figures 15 and 16, the ring 92 is positioned angularly around the axis A so that its pads 94 are aligned with the spaces located between the teeth 82, 84. The ring 92 is then moved in axial translation inside the bowl 58 until the pads 94 are engaged in these spaces. The bridges 96 can then rest on the teeth 84 of the ring 52. The ring 92 thus prevents any rotation of the ring 52 inside the bowl 58.

In the last step illustrated by Figure 17, the rod 100 is engaged in the grooves 86, 98 aligned circumferentially with each other. Ring 100 prevents accidental dismantling of ring 92.

It is understood that the dismantling of the blade is carried out by carrying out the aforementioned steps in the reverse order. It is also understood that one of the essential steps in the assembly and disassembly of the foot concerns the immobilization ring 52. This ring 52 can be manipulated from outside a turbomachine, which is particularly advantageous during a maintenance operation. . A blade can be disassembled and removed from the propeller by dismantling and removing a minimum number of parts.

Reference is made to FIG. 18 which illustrates an alternative embodiment of the immobilization ring 52'. This ring 52' has a wedge-shaped cross-section and is configured, under the effect of centrifugal forces in operation, to be axially biased outwards from the bowl 58 and to hold the blade root 14 axially tight by effect corner.

In the example shown, the ring 52 'has in axial half-section a generally trapezoidal shape and comprises a lower surface 102 and two side surfaces, respectively internal 104 and external 106. The surfaces 102-106 are annular and extend around of the A axis.

The ring 52' is engaged around the foot 14 and in the bowl and bears axially by its surface 102 on the hooping ring 50, here via a washer 108.

The outer surface 106 of the ring cooperates by bearing and axial sliding with a complementary ring 110 mounted inside the bowl and around the ring 52'.

The ring 52' is sectorized and formed of several sectors arranged around the axis A with a certain circumferential distance from each other. By way of non-limiting example, the sectors are six in number and regularly distributed around the axis A.

Finally, a nut 112 is screwed onto an internal thread of the upper end of the bowl 58 and cooperates by bearing and axial sliding with the internal surface 104 of the ring 52'.

The screwing and tightening of the nut 112 causes both an axial displacement of the sectors of the ring 52 'bearing on the washer 108, and a radial stress of these sectors against the ring 110 of complementary shape. Any mounting clearance is then removed.

Shaft 26 comprises a cylindrical shoulder 114 resting against a complementary cylindrical shoulder 116 of bowl 58, here at the junction between the middle part 42 and the lower end of shaft 26. The advantage of this variant is in particular to take up the efforts centrifuges in order to retain the blade but also to replace the aforementioned member 66 by directly applying a prestress between the barrel 26 and therefore the root 14 of the blade, and the inner ring 54a of the bearing 54.

Other embodiments not shown are possible, including:

• the half-shells 26a, 26b of the shaft 26 can be attached to the body 24 by bolting, riveting, welding, etc. ;
• the glue connecting the barrel 26 to the body 24 can be an epoxy glue but it can also be an elastomer or a thermoplastic glue. It is also possible to use a non-stick film to leave the possibility of relative movement by limiting wear by friction;
• Still with regard to the shaft/body interface, several technical solutions can also be combined together from those proposed (gluing, prestressing by washers or springs, prestressing by the geometry of the shaft); these solutions can be combined independently of the existence of a clearance between the two parts of the barrel;
• although this is less advantageous, the radial position of the bearing ensuring the centrifugal retention of the blade can be reversed with the radial position of the bearing which ensures the absorption of bending moments resulting from aerodynamic and centrifugal forces.

Claims (15)

System (34) for controlling the angular setting of a propeller blade (10), for an aircraft turbine engine, characterized in that it comprises:
- a bowl (58) comprising an annular wall (58a) extending around an axis (A) intended to be a wedging axis of the blade, this annular wall (58a) comprising a lower axial end closed by a bottom wall (58b), and an open upper axial end configured to allow mounting of a foot (14) of the blade (10) inside the bowl (58), the bottom wall (58b) being configured to cooperate by complementarity of shapes with a free end (28) of said foot (14) so that the bowl (58) is integral in rotation with the foot (14) around said axis (A), and
- an immobilization ring (52, 52') which extends around said axis (A) and which is configured to be mounted around the foot (14), this immobilization ring (52, 52') being configured to be mounted inside the bowl (58) and to cooperate respectively with the foot (14) and the annular wall (58a) of the bowl (58) in order to ensure the axial retention of the foot (14) in the bowl (58 ). A system (34) according to claim 1, wherein it further comprises:
- a lower rolling guide bearing (54) extending around said axis (A) and mounted around a lower part of the annular wall (58a),
- an upper rolling guide bearing (56) extending around said axis (A) and mounted around an upper part of the annular wall (58a). System (34) according to the preceding claim, in which at least one of the guide bearings (54, 56) has its inner ring (54a, 56a) which is integrated with said bowl (58). A system (34) according to claim 2 or 3, wherein at least one of the guide bearings (54, 56) is angular contact. System (34) according to one of the preceding claims, in which the bottom wall (58b) comprises a recess (60) having a non-circular cross-section and configured to receive the free end (28) of the foot (14) of dawn (10). System (34) according to the preceding claim, in which the recess (60) is eccentric with respect to the wedging axis (A). System (34) according to one of the preceding claims, in which it further comprises an elastically deformable member (66) extending around the wedging axis (A) and mounted inside the bowl (58), this member (66) bearing axially on the bottom wall (58b) and being configured to axially urge the root (14) of the blade (10) towards the outside of the bowl (58). System (34) according to one of the preceding claims, in which the immobilizing ring (52) is a dog clutch ring which comprises external dog teeth (84) configured to cooperate with internal teeth (82) of complementary dog dog of the annular wall (58a) of the bowl (58). System (34) according to the preceding claim, in which it further comprises a locking ring (92) and an annular snap ring (100), the locking ring (92) being configured to be axially engaged between the internal teeth (82 ) and outer (84) dog clutch to prevent rotation of the dog clutch ring (52) inside the bowl (58), and the annular ring (100) being mounted in the bowl (58) to axially block the locking ring (92) in the bowl (58). System (34) according to one of Claims 1 to 7, in which the locking ring (52') has a wedge-shaped cross-section and is configured, under the effect of centrifugal forces in operation, to be biased axially towards the outside of the bowl (58) and to hold the blade root (14) axially tight by wedge effect. Assembly comprising a system (34) according to one of the preceding claims and a variable-pitch propeller blade (10), this blade (10) comprising a blade (12) connected to a root (14), the root (14 ) comprising a body (24) housed in an annular barrel (26) which extends around an axis (A) for wedging the blade. Turbomachine, in particular aircraft, comprising at least one system (34) according to one of Claims 1 to 10 or an assembly according to the preceding claim. A method of assembling an assembly according to claim 11, in which it comprises the steps of:
a) inserting the root (14) of the blade (10) inside the bowl (58) of the system (34), by moving the blade (10) in a direction parallel to the setting axis ( AT),
b) engagement of a free end (28) of the foot (14) in a recess (60) of the bottom wall (58b) of the bowl (58) so as to secure the bowl (58) in rotation with the foot ( 14) dawn (10), and
c) engagement of the immobilization ring (52, 52'), previously mounted or present around the root (14) of the blade (10), in the bowl (58) and mounting of this ring (52, 52' ) in the bowl (58) and on the root (14) of the blade (10) so as to ensure the axial retention of the root (14) in the bowl (58). Method according to Claim 13, the system (34) being as defined in Claim 6, in which, during steps a) and/or b), the root (14) of the blade (10) bears on the member (66) and compresses it axially. A method according to claim 13 or 14, the system (34) being as defined in claim 8 or 9, wherein during step c) the retaining ring (52) is mounted in the bowl (58) by dogging.