Fan module with variable-pitch blades

Abstract

The invention relates to a fan module (1) with variable-pitch blades for a propulsion assembly of longitudinal axis (X), the module comprising a system (22) for changing the pitch of the blades that comprises an actuator and a balancing system comprising a first ring (110) and a second ring (120), each rotatably movable about the longitudinal axis (X), each ring supporting balance weights at the periphery, the weights being configured to balance the balancing system (100) for a reference pitch of the blades, and wherein the balancing system is secured to the mobile body (27) of the actuator and configured in such a way that a movement of the mobile body (27) of the actuator modifying the pitch of the blades causes a counter-rotating simultaneous rotation of the first and second rings of the balancing system.

Description

[0001] DESCRIPTION

[0002] TITLE OF THE INVENTION: VARIABLE PITCH BLADE FAN MODULE

[0003] TECHNICAL FIELD

[0004] The present invention relates to a variable-pitch fan module for a propulsion unit, and more specifically to a balancing system adapted to such a fan.

[0005] PRIOR ART

[0006] The technical background includes documents FR-A1-3 066 559 and USAI -2012 / 0 070 292.

[0007] A fan equipped with variable pitch blades (known by the English acronym VPF for "Variable Pitch Fan") makes it possible to adjust the pitch (and more precisely the pitch angle) of the blades according to the flight parameters, and thus to optimize the operation of the fan, and generally of the propulsion system in which such a fan is integrated. As a reminder, the pitch angle of a blade corresponds to the angle, in a longitudinal plane perpendicular to the axis of rotation of the blade, between the chord of the blade and the plane of rotation of the fan.

[0008] It is known to have pitch change systems adapted to propulsion units or turbomachines generally comprising a ducted fan or an unducted propeller equipped with variable pitch moving blades.

[0009] In the category of turbomachines with at least one unducted propeller, also called "open rotor" or "unducted fan", there are those with a single unducted propeller and a rectifier comprising several stator blades (known by the English acronym USF for "Unducted Single Fan").

[0010] An open rotor type turbine engine mainly comprises, inside a fixed cylindrical casing carried by the structure of the aircraft, a coaxial gas generator part and a propulsion part. The gas generator part can be arranged upstream or downstream of the propulsion part. The terms upstream and downstream are defined in relation to the circulation of gases in the turbine engine. The propulsion part comprises at least one propeller driven in rotation by a turbine, in particular a low pressure turbine, of the gas generator part via a reduction gear, for example, with epicyclic gear trains. In certain cases, the propulsion part can comprise two coaxial and counter-rotating propellers, respectively upstream and downstream, which are driven, in rotation opposite to each other, by the turbine of the gas generator via the reduction gear. The propeller or propellers extend substantially radially with respect to the transmission shaft with a longitudinal axis outside the casing.

[0011] Generally, the or each propeller comprises a substantially cylindrical rotating casing carrying an outer polygonal ring hub rotatably received around the longitudinal axis in the stator of the turbomachine. The ring comprises radial cylindrical housings distributed on its periphery around the longitudinal axis. Shafts with radial axes, perpendicular to the longitudinal axis of the turbomachine, secured to the roots of the blades are received in the housings of the polygonal rings and also pass through radial passages of the cylindrical casing.

[0012] To enable the turbine engine to operate optimally in the various flight phases encountered, the propeller blades can rotate in the radial housings of the polygonal rings. To do this, they are rotated around their respective pivot axes, called the pitch axis, by a suitable system that allows the pitch of the blades to be varied during flight, i.e. the pitch of the propellers.

[0013] This system for changing the pitch of the propeller blades covers an angular range of rotation between two extreme positions, namely an extreme position called thrust reversal or "reverse" for which the blades protrude for example by 30° the plane transverse to the axis of the turbine engine (the direction of advance of the aircraft) to participate in the braking of the aircraft, in the manner of conventional thrust reversers, and an extreme position called "feathering" for which the blades are then retracted as much as possible relative to the direction of advance, for example, in the event of engine failure or during a failure (or breakdown) of the blade pitch control device (for example a failure of a hydraulic actuator) so that the latter offer the least resistance (drag) possible.

[0014] Generally, a propeller blade pitch change system includes a control device and a linkage mechanism connecting the control device to each propeller blade to provide the desired angular pivoting of the blades.

[0015] In addition, a passive feathering system is provided to compensate for a failure of the hydraulic system or the cylinder. Feathering of the blades is generally carried out via counterweights. Usually, the counterweights are placed on the root of each blade and are potentially very heavy depending on the available space and come to load centrifugally and therefore increase the constraints of the root of the blades and the bearings of the root of the blades already under heavy stress.

[0016] Various solutions have been proposed for changing the pitch of fan blades and feathering the blades on open rotor or other turboshaft engines.

[0017] For example, document FR 3 066 559 discloses a blade pitch change system comprising a single annular cylinder arranged on a fixed casing or internal stator relative to the fan hub and a connecting mechanism comprising a transfer bearing, better known by the English acronym LTB for "Load Transfer Bearing", fixed on one side to the moving part of the cylinder and cooperating, on the other side, with a means of connecting the mechanism to the blades of the rotating hub, such that the load transfer bearing of the rotationally driven mechanism transmits the translational movement of the moving part of the fixed cylinder, by means of connecting the rotating mechanism to change the orientation of the propeller blades. This pitch change system further comprises a blade feathering device comprising counterweights with a lever mechanism arranged in the rotating reference frame, connected to the outer ring of the load transfer bearing by a connecting rod.The use of counterweights with a lever mechanism acting on the cylinder makes it possible to multiply the force and take advantage of an empty space to reduce the mass of the counterweights and not stress the base of the blades. Having a linear actuator in a fixed reference frame makes it easier to supply oil and reduce the rotating masses.

[0018] However, after assembly, the lever feathering device and therefore the engine requires balancing at the production end. This balancing is typically done by installing balancing weights on the fan disc at the upstream cone. This balancing compensates for the residual unbalance of the fan. It is based on the assumption that this residual unbalance is always the same regardless of the engine's operating point. Therefore, compensating for this residual unbalance on the ground is sufficient to balance the fan in all engine operating modes.

[0019] This assumption is no longer valid in the case of a variable-pitch fan or propeller. Indeed, changing the pitch of the fan blades or propeller blades changes the position of their center of gravity, which, particularly for wide-chord blades / blades, is not exactly on the pivot axis. This results in an unbalance resulting from the bladed wheel, which varies with the pitch. If this variation is too significant, it is then impossible to guarantee acceptable engine balancing at all operating points. However, poor engine balancing can lead to discomfort linked to cabin vibrations, or even excessive loads.

[0020] The objective of the present invention is thus to propose a blower module making it possible to overcome at least some of these drawbacks.

[0021] SUMMARY OF THE INVENTION

[0022] To this end, the invention relates to a variable-pitch fan module for a longitudinal axis propulsion unit, said module comprising:

[0023] - a casing rotating around the longitudinal axis and carrying the blades, and

[0024] - a system for changing the pitch of the blades comprising a control device and a connecting mechanism, the control device comprising an annular actuator centered on the longitudinal axis having a fixed body attached to the rotating casing and a movable body movable relative to the fixed body, the movable body being coupled to a synchronization ring of the connecting mechanism, said synchronization ring being connected to the blades and configured to be driven in rotation about the longitudinal axis by the movable body so as to change the pitch of the blades.

[0025] According to the invention, the module comprises a balancing system comprising a first ring and a second ring each movable in rotation around the longitudinal axis, each ring supporting balancing weights at the periphery, the weights being configured to balance the balancing system for a reference setting of the blades, and the balancing system is integral with the movable body of the actuator and configured in such a way that a movement of the movable body of the actuator modifying the setting of the blades causes a simultaneous counter-rotating rotation of the first and second rings of the balancing system.

[0026] The invention thus proposes a balancing system integrated into the variable-pitch fan module allowing it to be balanced at all engine operating points.

[0027] Such a balancing system advantageously makes it possible to install an initial compensatory unbalance in the reference setting position of the blades and to vary this compensatory unbalance as a function of the variation in the blade setting angle. Thus, this compensatory unbalance compensates for the unbalance resulting from the bladed wheel which varies with the setting at any operating point. For this purpose, the balancing system according to the invention comprises two counter-rotating rings whose simultaneous rotation in opposite directions is guided by the mechanical movement of the movable body of the control device of the blade setting change system.

[0028] Although the unbalance correction is passive since there is no feedback loop, it adapts to the different blade pitches.

[0029] The blower module according to the invention may comprise one or more of the following features, taken in isolation from one another or in combination with one another in all technically possible combinations:

[0030] - the movable body of the actuator is movable in translation relative to the fixed body and in which the balancing system is configured so that a translation of the movable body of the actuator modifying the pitch of the blades causes a simultaneous counter-rotating rotation of the first and second rings of the balancing system;

[0031] - the balancing system is configured so that the first crown and the second crown of the balancing system are each axially locked;

[0032] - the first crown is extended by a first cylindrical tube comprising a first helical groove having a first pitch;

[0033] - the second crown is extended by a second cylindrical tube surrounding the first cylindrical tube and comprising a second helical groove having a second pitch opposite the first pitch;

[0034] - the balancing system comprises a pin and a third cylindrical tube coaxial with the first and second cylindrical tubes and surrounding the first and second cylindrical tubes, the third cylindrical tube being integral with the mobile body and having a through-orifice, the pin being housed integrally in the through-orifice of the third cylindrical tube and being inserted into the first and second helical grooves;

[0035] - the first step and the second step have an absolute value substantially equal to the ratio of a translational displacement of the moving part to the variation in the pitch of the blades corresponding to the displacement;

[0036] - the balancing weights of the first crown are heavier than the balancing weights of the second crown;

[0037] - the balancing system includes several different sets of balancing weights for the first crown and for the second crown;

[0038] - each of the rings has a predetermined number of balancing weights and each balancing weight has an angular position on the periphery of the first ring or the second ring, a material and a mass, the number of balancing weights, their angular positions, their materials and their masses depending on the characteristics of the blades of the fan module;

[0039] - the characteristics of the fan module blades include the radial, tangential and axial weight-moments of the blades.

[0040] The invention also relates to a longitudinal axis propulsion assembly comprising at least one variable-pitch fan module according to the invention and as described previously.

[0041] BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The present invention will be better understood and other details, characteristics and advantages of the present invention will appear more clearly on reading the description of a non-limiting example which follows, with reference to the appended drawings in which:

[0043] - figure 1 is an axial (or longitudinal) half-sectional view of a fan module comprising a balancing system and a blade feathering device, in a first position corresponding to a blade feathering position, along an axial plane passing through the axis of rotation of a fan blade;

[0044] - figure 2 is an axial (or longitudinal) half-sectional view of the module of figure 1 in a second position corresponding to a reverse position, that is to say without failure of the control device;

[0045] - figure 3 is an exploded schematic perspective view of an embodiment of a balancing system equipping a fan module according to the invention;

[0046] - Figure 4 is a schematic perspective view of the balancing system of Figure 3 assembled;

[0047] - figure 5 is a schematic top view of the balancing system of figure 4 corresponding to a reference setting of the blades of the fan module according to the invention;

[0048] - Figure 6 is a schematic front view of the balancing system of Figure 5 for the reference setting;

[0049] - Figure 7 is a schematic front view of the fan blades and illustrating the radial and tangential moment weights for the reference setting; - Figure 8 is a schematic view of a blade and its tangential and axial moment weights for the reference setting;

[0050] - figure 9 is a schematic top view of the balancing system of figure 4 corresponding to a setting different from the reference setting of the blades of the fan module according to the invention;

[0051] - figure 10 is a schematic front view of the balancing system of figure 5 after modification of the blade setting;

[0052] - Figure 11 is a schematic front view of the fan blades and illustrating the radial and tangential moment weights after modification of the blade pitch;

[0053] - figure 12 is a schematic view of a blade and its tangential and axial moment weights after modification of the blade pitch;

[0054] - figure 13 schematically represents an enlarged view of the balancing system of the fan module of figure 1 showing a first variant of axial locking of the crowns of the balancing system;

[0055] - figure 14 illustrates a second variant embodiment of the axial locking of the balancing system; and

[0056] - figure 15 illustrates a second variant embodiment of the axial locking of the balancing system.

[0057] Elements having the same functions in different implementations have the same references in the figures.

[0058] In the figures, scales and proportions are not strictly respected, for the purposes of illustration and clarity.

[0059] In the description and the claims, the terminology axial, radial and transverse will be adopted without limitation with reference to the trihedron A, R, T indicated in the figures.

[0060] DESCRIPTION OF EMBODIMENTS

[0061] The invention applies to a propulsion unit intended to be mounted on an aircraft. The aircraft comprises a fuselage and at least two wings extending on either side of the fuselage along the axis of the fuselage. At least one propulsion unit is mounted, for example, under each wing. The propulsion unit may be a turbojet, for example a propulsion unit equipped with a ducted fan (turbofan) or a turboprop, for example a propulsion unit equipped with an unducted propeller ("open rotor", "USF" for "Unducted Single Fan" or "UDF" for "Unducted Fan"). Of course, the invention applies to other types of propulsion units, for example comprising two coaxial and counter-rotating propellers. Generally speaking and in the remainder of the description, the term "fan" is used to designate either a fan or a propeller.

[0062] In Figures 1 and 2, a fan 1 of a propulsion unit 2 with a longitudinal axis X is shown. The fan 1 comprises a rotating casing or rotor 3 movable around the axis X relative to a fixed casing. The rotor 3 carries a series of variable-pitch blades 5. The fan 1 is here placed upstream of the engine part of the propulsion unit 2 which comprises, for example, successively from upstream to downstream, a gas generator and a power turbine which drives the rotor 3 of the fan 1 via a speed reducer. By convention, in the present application, the terms “upstream” and “downstream” are defined relative to the direction of circulation of the gases in the fan 1 (or propulsion unit 2).Likewise, by convention in the present application, the terms “internal” and “external”, “interior” and “exterior” are defined radially relative to the longitudinal (or axial) axis X of the propulsion assembly 2, which is in particular the axis of rotation of the rotors of the compressors and turbines of the gas generator.

[0063] The rotating casing 3 comprises an internal annular shaft centered on the X axis which, in operation, is driven by the power turbine via the speed reducer. The rotating casing 3 further comprises a ring 16 for supporting the blades 5.

[0064] More specifically, each blade 5 comprises a foot, for example in the form of a bulb-shaped attachment, this foot being secured to a pivot 18 mounted in a housing 19 of a base 20 projecting from the ring 16 in a mobile manner in rotation about a substantially radial axis Y via two rolling bearings. The rolling bearings placed in each housing 19 are generally lubricated with grease.

[0065] The fan comprises a system 22 for changing the pitch of the blades 5 or a system for setting the blades 5 around their Y axis, and more precisely the setting angle of the blades 5 which corresponds for a blade 5 to the angle, in a longitudinal plane perpendicular to the Y axis, between the chord of the blade 5 and the plane of rotation of the fan 1.

[0066] The blades 5 are positioned in the flag position in Figure 1. In the flag position, the pitch angle is positive and generally equal to 90°. This position of the blades 5 makes it possible to limit the resistance (drag) generated by the latter.

[0067] The blades 5 are positioned in the reverse thrust position in Figure 2.

[0068] According to the embodiment illustrated in the figures and in particular figures 1 and 2, the pitch change system 22 of the blades 5 comprises a linear annular control device or actuator 23, centered on the X axis, common to all the blades 5 and a connecting mechanism 24 connected to each blade 5, this connecting mechanism 24 making it possible to transform the linear movement initiated by the actuator 23 into a rotational movement of the corresponding blade 5.

[0069] More precisely, the linear actuator 23 comprises a fixed annular body 25 attached to an annular support (centered on X) of the rotor 3 by means of fixing screws 89, it is therefore arranged in the rotating frame linked to the rotor. In other words, the fixed body 25 is integral in rotation with the rotor 3. The linear actuator 23 further comprises a movable body 27, the latter being movable in translation relative to the fixed body 25 along the axis X in the example illustrated in particular in FIGS. 1 and 2. Advantageously, the linear actuator 23 is hydraulic. Preferably, the actuator 23 is a hydraulic cylinder comprising a fixed cylinder integral with the shaft of the rotor 3 forming the fixed body 25 of the actuator and a rod forming the movable body 27 of the actuator.

[0070] The connecting mechanism 24 of the pitch change system 22 further comprises a synchronization ring 34 secured to the movable body 27 of the actuator 23. In particular, a ferrule 81 makes it possible to fix the synchronization ring 34 to the movable body 27 of the actuator via screws 82. The synchronization ring 34 is centered on the longitudinal axis X and is intended to drive the setting of blades 5 simultaneously.

[0071] The connecting mechanism 24 for transforming the linear movement of the actuator into a rotational movement of the blade 5 further comprises, for each blade 5, a connecting rod 35. One of the ends of the connecting rod 35 is mounted so as to rotate freely along a substantially radial axis D with the synchronization ring 34 via a yoke and the other end is mounted so as to rotate freely with an eccentric 36 connected to the pivot 18 which orients the root of the corresponding blade 5 via, for example, a splined connection. The axis D is offset relative to the rotational axis Y of the blade 5. The connecting rod 35 and the eccentric 36 make it possible to multiply the force required to adjust the setting of the corresponding blade 5.

[0072] The linear movement of the movable body 27 of the actuator 23 makes it possible to synchronize the timing of all the blades 5 via in particular the synchronization ring 34.

[0073] The fan 1 also comprises a feathering device 38 for the blades 5, in particular in the event of failure (or breakdown) of the pitch change device 22, and for example a failure in the hydraulic supply of the linear actuator 23. As a reminder, the flag position corresponds to a positive setting generally substantially equal to 90°. The feathering device 38 comprises at least one mechanism 39 comprising a lever 40 articulated by a pivot connection 80 around an axis E, called the articulation axis, fixed relative to the rotor 3. The articulation axis E is here rectilinear and perpendicular to the axis X. The lever 40 has a first end 41 and a second end 42. A flyweight 43 is integral with the first end 41 and the second end 42 is coupled to the synchronization ring 34 via a connecting rod 60.The weight 43 is capable, under the centrifugal effect, of being moved into a position (see figure 1) in which the synchronization ring 34 imposes a flag position on the blades 5. The mechanisms 39 of the feathering device 38 are distributed angularly in a regular manner around the axis X. Thus, all of the weights 43 form an annular row centered on the longitudinal axis X and spaced angularly in a regular manner.

[0074] According to the embodiment illustrated in Figures 1 and 2, for each mechanism 39, the lever 40 has a V shape in axial section. Each lever 40 comprises two arms spaced angularly and connected at the level of the articulation of the lever at A, a first arm 44 supporting the weight 43 and a second 45 coupled to the synchronization ring 34 via the connecting rod 60. The two arms 44, 45 are fixed relative to each other. The length of the first branch 44 is greater than the length of the second branch 45, approximately twice as long in the present case. This length ratio makes it possible to multiply the force provided by each weight 43, and in other words to minimize their mass, and more generally, the mass of all the weights 43.

[0075] The lever 40 is articulated relative to the rotating casing at A by a pivot connection, preferably formed by a needle bearing or by two ball bearings. Advantageously, the distance between the articulation axis A of the lever 40 and the longitudinal axis X is greater than or equal to the distance between a radially inner edge of the synchronizing ring and the longitudinal axis X, the radially inner edge allowing attachment to the movable body 27 of the actuator by means of the ferrule 81.

[0076] The second end 42 of the lever 40 and an upstream axial end of the connecting rod 60 are coupled by a first ball joint around an axis B. Similarly, a downstream axial end of the connecting rod 60 is articulated in a yoke of the synchronization ring 34 preferably by a second ball joint around an axis C.

[0077] When the propulsion unit 2 is operating normally (no failure), the feathering device 38 is subordinate to the pitch change system 22 of the blades 5, and more precisely to the linear actuator 23. It is noted that when the blades 5 are in the “thrust reversal” position, the weights 43 of the mechanisms 39 of the feathering device 38 of the blades 5 are close to the longitudinal axis X of the rotor 3 as illustrated in FIG. 2.

[0078] In the event of a failure (need to position the blades 5 in the flag position), for example a failure in the hydraulic supply of the linear actuator 23, the system 22 for setting the blades 5 then becomes subordinate to the feathering device 38, and more precisely the weights 43 which, under the centrifugal effect, find themselves further away from the longitudinal axis X of the rotor 3 as illustrated in FIG. 1, to impose a flag position on the blades 5.

[0079] The lever counterweight mechanism thus acts on the cylinder which is kinematically linked with the blade actuation mechanism. The number of lever counterweights is thus independent of the number of blades. The lever counterweight mechanism imposes the direction of the flag position on the pitch actuation kinematics.

[0080] According to the invention, the blower module further advantageously comprises a balancing system 100 which will be described in detail with reference to the figures. In particular, figures 3 and 4 schematically and respectively represent an exploded view of an embodiment of the balancing system 100 and a partially transparent assembled view thereof.

[0081] The balancing system 100 comprises a first crown 110 and a second crown 120. The first crown 110 is rotatable about the longitudinal axis X. Similarly, the second crown 120 is rotatable about the longitudinal axis X.

[0082] The first crown 110 extends radially between an inner edge 112A of radius R1A and an outer peripheral edge 112B of radius R1B. Of course, the radius R1B is greater than the radius R1A. Furthermore, the first crown 110 extends axially between an upstream face 114 and a downstream face 116, preferably parallel to each other. The first crown 110 has a thickness E1 defined as the distance in the axial direction A (parallel to the longitudinal axis X) between the upstream face 114 and the downstream face 116 of the first crown 110.

[0083] Similarly, the second crown 120 extends radially between an inner edge 122A of radius R2A and an outer peripheral edge 122B of radius R2B. Of course, the radius R2B is greater than the radius R2A. In addition, the second crown 120 extends axially between an upstream face 124 and a downstream face 126. In addition, the radius R2A of the inner edge 122A of the second crown 120 is greater than the radius R1A of the inner edge 112A of the first crown 110.

[0084] Advantageously and as illustrated in particular in FIG. 4, the second crown 120 further comprises an external annular rim 128. This external annular rim 128 extends axially from the upstream face 124 of the second crown 120 towards the upstream, that is to say in a direction parallel to the axis of rotation of the second crown 120 over a length L in the axial direction A (parallel to the longitudinal axis X).

[0085] Furthermore, the outer annular flange 128 extends radially between an inner annular surface 128A of radius R3A and an outer annular surface 128B of radius R3B. Of course, the radius R3B is greater than the radius R3A.

[0086] Preferably, the outer annular surface 128B of the annular rim 128 is the upstream extension of the outer peripheral edge 122B of the second crown 120. In other words, the radius R3B of the outer annular surface 128B is equal to the radius R2B of the outer peripheral edge 122B.

[0087] Preferably, the radius R3A of the internal annular surface 128A of the annular rim 128 is greater than the radius R1B of the external peripheral edge 112B of the first crown 110. As a result, the first crown 110 can advantageously be housed inside an open cavity 131 of the second crown 120 delimited axially downstream by the upstream face 124 of the second crown 120 and radially by the annular rim 128 of the second crown 120 and more precisely by its internal annular surface 128A. This advantageously makes it possible to limit the size of the balancing system 100.

[0088] In the example illustrated in the figures, the length L of the annular rim 128 is less than the thickness E1 of the first crown 110. However, as a variant, the length L of the annular rim 128 may be equal to or greater than the thickness E1 of the first crown 110.

[0089] For example, the first and second crowns 110, 120 have a diameter between 10 cm and 50 cm.

[0090] The first ring 110 comprises several orifices 119, through or not, distributed angularly around the periphery of the first ring, preferably in a regular manner. Thus, the orifices 119 are arranged close to the outer peripheral edge 112B. In other words, the orifices 119 are closer to the outer peripheral edge 112B of radius R1B than to the inner edge 112A of radius R1A of the first ring 110. The orifices 119 of the first ring 110 are intended to receive balancing weights. In operation, some of the orifices 119 of the first ring actually house balancing weights 130A while others are empty as detailed below.

[0091] For example, the first crown 110 has between 10 and 100 orifices 119.

[0092] The second ring 120 comprises several orifices 129, through or not, distributed angularly around the periphery of the second ring, preferably in a regular manner. Thus, the orifices 129 are arranged close to the outer peripheral edge 122B. In other words, the orifices 129 are closer to the outer peripheral edge 122B of radius R2B than to the inner edge 122A of radius R2A of the second ring 120. Preferably, the orifices 129, through or not, are provided in the outer annular rim 128 between the inner annular surface 128A of radius R3A and the outer annular surface 128B of radius R3B.

[0093] The orifices 129 of the second crown 120 are intended to receive balancing weights 130B. In operation, as for the first crown 110, some of the orifices 129 of the second crown actually house balancing weights while others are empty as detailed below.

[0094] For example, the second crown 120 has between 10 and 100 orifices 129.

[0095] Thus, the balancing system 100 comprises balancing weights 130 supported by the first ring 110 and the second ring 120. More precisely, balancing weights 130A are housed in one or more orifices 119 of the first ring 110 and balancing weights 130B are housed in one or more orifices 129 of the second ring 120. The balancing weights 130 are for example screws, nuts, locking screws or other dedicated masses whose mass is known and calibrated.

[0096] For example, the mass of each balance weight 130 is between 5 g and 25 g.

[0097] Advantageously, the balancing system 100 comprises several different sets of balancing weights for the first ring 110 and for the second ring 120. In the same set of balancing weights, some balancing weights 130 may have the same mass or all different masses or all identical masses. Similarly, in the same set of balancing weights, some balancing weights 130 may be made of the same material or all different materials or all identical materials. Two separate sets of balancing weights may differ from each other by at least one of the parameters of the weights, for example the mass of the weights or the materials of the weights.

[0098] The weights supported by the first ring 110 and the second ring 120 are configured to balance the balancing system for a reference setting of the blades as will be described in detail later.

[0099] For this purpose, the first ring 110 has a predetermined number N1 of balancing weights 130A each having a predetermined mass and a material constituting it. Each balancing weight 130A is arranged on the periphery of the first ring 110 at a predetermined angular position. Similarly, the second ring 120 has a predetermined number N2 of balancing weights 130B each having a predetermined mass and a material constituting it. Each balancing weight 130B is arranged on the periphery of the second ring 120 at a predetermined angular position.

[0100] The number N1 of balancing weights 130A, their respective angular positions on the first ring 110, their materials and their masses and the number N2 of balancing weights 130B, their respective angular positions on the second ring 120, their materials and their masses depend on characteristics of the blades of the fan module to be balanced and in particular for a reference setting of the blades. In particular, all of the above parameters: the number N1 of balancing weights 130A, their respective angular positions on the first ring 110, their materials and their masses and the number N2 of balancing weights 130B, their respective angular positions on the second ring 120, their materials and their masses depend in particular on the radial, tangential and axial weight-moments of the blades of the fan module used during their distribution when assembling the module.

[0101] Preferably, the balancing weights 130A of the first ring 110 are heavier than the balancing weights 130B of the second ring. More precisely, the assembly formed of the balancing weights 130A supported by the first ring 110 has a mass greater than that of the assembly formed of the balancing weights 130B supported by the second ring 120, preferably by a ratio equal to the ratio of the installation radii of the orifices 129 of the second ring 120 to that of the orifices 119 of the first ring 110.

[0102] The balancing capacity of such a balancing system 100 according to the invention varies between 20,000 cmxg and 100,000 cmxg. According to the invention, the balancing system 100 is integral with the movable body 27 of the actuator and configured so that a movement of the movable body 27 of the actuator modifying the pitch of the blades causes a simultaneous counter-rotating rotation of the first and second rings of the balancing system.

[0103] Preferably, and as illustrated in the figures and described previously, the movable body 27 of the actuator is movable in translation relative to the fixed body 25. In this case, the balancing system 100 is configured so that a translation of the movable body 27 of the actuator modifying the pitch of the blades causes a simultaneous counter-rotating rotation of the first ring 110 and the second ring 120 of the balancing system.

[0104] For this purpose, and as illustrated in particular in Figures 3 and 4, the first ring 110 extends downstream by a first cylindrical tube 140. The first cylindrical tube 140 is coaxial with the first ring 110. In other words, the first cylindrical tube 140 has the same axis of revolution as the first ring 110, coincident with the longitudinal axis X of the fan module when the latter is equipped with the balancing system 100. The first cylindrical tube 140 extends radially between an internal annular surface 140A of radius R4A and an external annular surface 140B of radius R4B. Of course, the radius R4B is greater than the radius R4A.

[0105] Preferably, the inner annular surface 140B of the first cylindrical tube 140 is the downstream extension of the inner edge 112A of the first crown 110. In other words, the radius R4A of the outer annular surface 140A is equal to the radius R1A of the inner edge 112A of the first crown.

[0106] The first cylindrical tube 140 comprises a first helical groove 142 passing through having a first pitch P1. By passing through, it is meant that it opens on the one hand onto the internal annular surface 140A and on the other hand onto the external annular surface 140B. The first helical groove 142 extends over the entire length of the first cylindrical tube 140 in the axial direction A.

[0107] In addition, the second ring 120 extends downstream by a second cylindrical tube 150, that is to say in the direction opposite to the annular rim 128. The second cylindrical tube 150 is coaxial with the second ring 120. In other words, the second cylindrical tube 150 has the same axis of revolution as the second ring 120, coincident with the longitudinal axis X of the fan module when the latter is equipped with the balancing system 100. The second cylindrical tube 150 extends radially between an internal annular surface 150A of radius R5A and an external annular surface 150B of radius R5B. Of course, the radius R5B is greater than the radius R5A.

[0108] The second cylindrical tube 150 is shaped to house and at least partially surround the first cylindrical tube 140. As a result, the radius R5A of the inner annular surface 150A of the second cylindrical tube 150 is greater than the radius R4B of the outer annular surface 140B of the first cylindrical tube 140.

[0109] Preferably, the internal annular surface 150B of the second cylindrical tube 150 is the downstream extension of the internal edge 122A of the second crown 120. In other words, the radius R5A of the external annular surface 150A is equal to the radius R2A of the internal edge 122A of the second crown 120.

[0110] The second cylindrical tube 150 comprises a second helical groove 152 passing through having a second pitch P2. By passing through, it is meant that it opens on the one hand onto the internal annular surface 150A and on the other hand onto the external annular surface 150B of the second cylindrical tube 150. The second helical groove 152 extends over the entire length of the second cylindrical tube 150 in the axial direction A.

[0111] The second step P2 is opposite to the first step P1. In other words, they have the same absolute value but opposite signs.

[0112] Advantageously, the first step P1 and the second step P2 have an absolute value substantially equal to the ratio of a translational displacement of the mobile part 27 to the variation in the pitch of the blades corresponding to the displacement.

[0113] Furthermore, the balancing system 100 comprises a pin 160 and a third cylindrical tube 170. The third cylindrical tube 170 is coaxial with the first and second cylindrical tubes 140, 150. In other words, the third cylindrical tube 170 has the same axis of revolution as the second cylindrical tube 150 and the first cylindrical tube 140, that is to say coincident with the longitudinal axis X of the fan module when the latter is equipped with the balancing system 100.

[0114] The third cylindrical tube 170 extends radially between an inner annular surface 170A of radius R7A and an outer annular surface 170B of radius R7B. Of course, the radius R7B is greater than the radius R7A.

[0115] The third cylindrical tube 170 is shaped to house and at least partially surround the first cylindrical tube 140 and the second cylindrical tube 150. As a result, the radius R7A of the inner annular surface 170A of the third cylindrical tube 170 is greater than the radius R5B of the outer annular surface 150B of the second cylindrical tube 150.

[0116] The third cylindrical tube 170 is integral with the movable body 27 of the actuator. The third cylindrical tube 170 has a through orifice 172 shaped to receive the pin 160.

[0117] The pin 160 is housed securely in the through-hole 172 of the third cylindrical tube 170 and also inserted into the first helical groove 142 of the first cylindrical tube 140 and into the second helical groove 152 of the second cylindrical tube 150. The first helical groove 142 of the first cylindrical tube 140 and the second helical groove 152 of the second cylindrical tube 150 each form a cam for the pin 160.

[0118] As a result, the pin 160 is configured to cooperate with the first and second helical grooves 142, 152. Indeed, during the translation of the mobile body 27, the pin 160 forces the first cylindrical tube 140 and the second cylindrical tube 150 mounted collinearly and without the possibility of translation to pivot, and consequently the first crown 110 and the second crown 120 to pivot as well.

[0119] Figures 5 to 8 and 9 to 12 respectively illustrate the principle of unbalance correction by the balancing system according to the invention.

[0120] More specifically, figures 5 to 8 relate to a situation in which the orientation of the blades is according to a predetermined setting called reference setting.

[0121] Whereas figures 9 to 12 relate to a situation in which the orientation of the blades is according to another setting corresponding to an orientation at 90° to that of the reference setting.

[0122] Figures 5 and 9 each represent a schematic top view of the balancing system corresponding respectively to the reference setting and to the 90° setting. Figures 6 and 10 each illustrate a schematic front view of the balancing system of Figures 5 and 9 respectively.

[0123] Figures 7 and 11 are schematic front views of the fan blades illustrating the radial and tangential moment weights for the reference pitch and the 90° pitch respectively. Figures 8 and 12 illustrate the orientation of a blade and its tangential and axial moment weights for the reference pitch and the 90° pitch respectively.

[0124] For the reference setting taken as an arbitrary reference (figures 5 to 8), balancing weights 130 are placed on each of the two rings in phase opposition and so as to compensate for their respective unbalance (figure 6): the system is balanced. The unbalance resulting from the first ring 110 is shown diagrammatically by the arrow F1 while the unbalance resulting from the second ring 120 is shown diagrammatically by the arrow F2 which is opposite the arrow F1.

[0125] Knowing the characteristics of the blades, in particular their radial PMR, tangential PMT and axial PMA weight-moments, used during their distribution during assembly, it is possible to determine the angular position on each ring and the number or type of balancing weights to be installed on each ring. The balancing weights are chosen on the one hand so that their unbalance is exactly compensated for at the reference setting and on the other hand so that the sum of their unbalances is equal to the variation of the tangential unbalance generated by a 90° setting of the blades' setting with respect to the reference setting.

[0126] With reference to figures 9 to 12, starting from this initial pitch configuration, a change in the pitch of the blades relative to the reference pitch (figures 5-8) causes a variation in the tangential component PMT* in the radial-tangential plane. During the translation of the mobile body 27 according to the arrow F in figure 9 following the change in pitch of the blades, the pin 160 forces the first cylindrical tube 140 and the second cylindrical tube 150 mounted collinearly and without the possibility of translation to pivot, and consequently the first crown 110 and the second crown 120 to also pivot in the opposite direction shown diagrammatically respectively by the arrows Q1 and Q2.

[0127] The reverse pitches of the helicoids ensure that the first and second rings 110, 120 rotate in opposite directions relative to each other. The balancing weights 130A of the first ring 110 generate a resulting unbalance shown diagrammatically by the arrow F1 * while the unbalance resulting from the balancing weights 130B of the second ring 120 is shown diagrammatically by the arrow F2 *. These two unbalances no longer compensate each other: the arrows F1 * and F2 * are no longer opposed. On the contrary, their unbalances add up and are oriented on the bisector of the unbalance of each of the rings. This orientation is constant regardless of the angle of rotation of the rings relative to their reference position corresponding to the reference setting, only its amplitude changes.Thus, this unbalance component makes it possible to compensate for the unbalance component appearing by the pivoting of the blades and schematized by the resulting deflection of the sum of the radial PMR* and tangential PMT* weight-moments of the blades in this setting. The axial component PMA* also varies, however its effect is negligible on the driving vibrations compared to the variation of the PMT* component. Figures 13 to 15 illustrate different variants for achieving axial locking of the crowns of the balancing system while allowing their counter-rotating rotation. Figures 13 to 15 are enlarged views of the fan module of Figure 1 detailing the balancing system.

[0128] As indicated previously, the two crowns 110, 120 are movable in rotation around the longitudinal axis X of the balancing system (and of the fan module) while being blocked axially.

[0129] According to the variant illustrated in Figure 13, at least two rolling bearings 180A and 180B, preferably ball bearings, are arranged between the first cylindrical tube 140 and the second cylindrical tube 150 at each end of the first cylindrical tube 140 and the second cylindrical tube 150. Similarly, at least two rolling bearings 180C and 180D, preferably ball bearings, are arranged between the first cylindrical tube 140 and the fixed body 25 of the annular actuator. In the example illustrated, the fixed body 25 of the linear actuator extends axially upstream to support the bearings. The two rolling bearings 180C and 180D are arranged between the first cylindrical tube 140 and this extension 182 of the fixed body of the actuator, in particular of the cylinder.

[0130] In addition, at least one annular seal 184 is arranged between the radially outer surface 150B of the second cylindrical tube 150. The seal(s) 184 are oil seals shaped to isolate the enclosures on either side of the movable actuator. Three seals 184 are visible in the illustrated example.

[0131] This variant has the advantage of being very robust to deformations and stress increases if the balancing system is loaded.

[0132] According to the variant illustrated in Figure 14, at least one rolling bearing 280, preferably a ball bearing, is arranged between the first cylindrical tube 140 and the fixed body 25 of the annular actuator. In the example illustrated, the fixed body 25 of the linear actuator extends axially upstream to support the bearing(s). In the example illustrated, the bearing 280 is arranged between the first cylindrical tube 140 and this extension 282 of the fixed body of the actuator, in particular of the jack.

[0133] In addition, the first cylindrical tube 140 extends from its downstream end radially inward to form a first internal annular rim 148. This first internal annular rim 148 forms an axial stop against the rolling bearing 280. In addition, the second cylindrical tube 150 also extends from its downstream end radially inward to form a second internal annular rim 158. This second internal annular rim 158 therefore extends substantially parallel to the first internal annular rim 148 of the first cylindrical tube 140. In addition, a first needle stop 284 is arranged downstream of the second internal annular rim 158 and more precisely between the second internal annular rim 158 and the movable body 27 of the actuator. In the illustrated example, the movable body 27 of the linear actuator extends radially outward to form a bearing surface for the first needle stop 284.This extension bears the numerical reference 286 in Figure 14. This first needle stop 284 forms an axial stop for the second internal annular rim 158 of the second cylindrical tube 150 of the second crown 120.

[0134] A second needle stop 288 is arranged downstream of the first internal annular rim 148 and upstream of the second internal annular rim 158 and more precisely between the second internal annular rim 158 and the first internal annular rim 148. This second needle stop 288 forms an axial stop for the first internal annular rim 148 of the first cylindrical tube 140 of the first crown 110.

[0135] Additionally, at least one seal 184 is arranged between the radially outer surface 150B of the second cylindrical tube 150. The seal(s) 184 are oil seals shaped to isolate the enclosures on either side of the movable actuator.

[0136] In the variant illustrated in Figure 15, as for the variant illustrated in Figure 14, the first cylindrical tube 140 extends from its downstream end radially inwards to form a first internal annular rim 148. In addition, the second cylindrical tube 150 also extends from its downstream end radially inwards to form a second internal annular rim 158. This second internal annular rim 158 therefore extends substantially parallel to the first internal annular rim 148 of the first cylindrical tube 140.

[0137] The variant of Figure 15 differs from that of Figure 14 in that the rolling bearing 280 between the first cylindrical tube 140 and the second cylindrical tube 150 is replaced by a plain bearing. For this purpose, the third cylindrical tube 170 of the balancing system 100 extends from its downstream end radially inward to form a third internal annular rim 174 to a radially internal U-shaped end 176. This third internal annular rim 174 therefore extends substantially parallel to the first internal annular rim 148 of the first cylindrical tube 140 and to the second internal annular rim 158 of the second cylindrical tube 150.

[0138] More precisely, the radially inner end 176 in the shape of an II comprises an axial portion 178 axially extending the third inner annular rim 174 upstream and a transverse portion 179 radially extending the axial portion 178 outwards. Thus, the third cylindrical tube 170 of the balancing system 100 extends successively and continuously from its downstream end radially inwards to form the third inner annular rim 174 then axially upstream to form the axial portion 178 then radially outwards to form the transverse portion 179. The transverse portion 179 therefore extends parallel to the third inner annular rim 174 and upstream of it.

[0139] The first internal annular rim 148 of the first cylindrical tube 140 and the second internal annular rim 158 of the first cylindrical tube 150 are held axially between the third internal annular rim 174 and the transverse portion 179.

[0140] A rolling bearing 380, preferably a ball bearing, is arranged between the transverse portion 179 and the first internal annular rim 148 of the first cylindrical tube 140.

[0141] In addition, a first needle stop 382 is arranged downstream of the second inner annular rim 158 and more precisely between the second inner annular rim 158 and the third inner annular rim 174. A second needle stop 384 is arranged downstream of the first inner annular rim 148 and upstream of the second inner annular rim 158 and more precisely between the second inner annular rim 158 and the first inner annular rim 148.

[0142] In addition, the balancing system comprises a first plain bearing 380A arranged between the first cylindrical tube 140 and the second cylindrical tube 150, preferably at the axial end of the first cylindrical tube 140 and the second cylindrical tube 150 closest respectively to the first crown 110 and the second crown 120.

[0143] A second plain bearing 380B is arranged between the second cylindrical tube 150 and the third cylindrical tube 170, preferably at the axial end of the second cylindrical tube 150 furthest from the second ring 120. Of course, alternatively, the first plain bearing 380A may be arranged at the axial end of the second cylindrical tube 150 furthest from the second ring 120 while the second plain bearing 380B is arranged at the axial end of the second cylindrical tube 150 closest to the second ring 120.

[0144] In addition, at least one seal 184 is arranged between the radially outer surface 170B of the third cylindrical tube 170 and the movable body 27 of the annular actuator. The seal(s) 184 are oil seals shaped to isolate the enclosures on either side of the movable actuator. For example, three seals are illustrated in FIG. 15.

[0145] The invention as described above makes it possible to provide a passive balancing means, adjusted when the blades / vanes are mounted and making it possible, by means of a mechanical movement, to correct the variations in unbalance caused by the variations in pitch of the blades / vanes.

[0146] It should be noted that the examples illustrated in the figures are in no way limiting; the blade pitch change system according to the invention could, for example, be incorporated into the rotor of a propeller of a turboprop or even into the rotor of each of the two propellers of a turbomachine comprising two counter-rotating propellers, better known by the English term "Open Rotor". In the definition of the invention, the term "fan" also covers the propeller or propellers of such turbomachines.

[0147] Furthermore, in the examples illustrated in the figures, the cylinder body is connected to the rotor (in the rotating frame of reference) and the cylinder rod, which is fixed to the fixed frame of reference connected to the casing, is movable in translation relative to the cylinder body, the synchronizing ring being connected to the cylinder rod. However, the invention could also be applied to a system in which the cylinder body would be fixed to the synchronizing ring and movable in translation relative to the cylinder rod. Thus, depending on the configuration of the cylinder, the entire feathering device is supported by a casing connected directly to the cylinder or to the structure of the engine.

[0148] Such a balancing system applies more generally to any turbomachine comprising a blade pitch control device. In particular, the invention also applies to a blade pitch change system comprising a single annular cylinder arranged on a fixed casing and a connecting mechanism comprising a transfer bearing or whose linear actuator is an electric cylinder.

[0149] Furthermore, although in the description, the first and second cylindrical tubes each comprise a single helical groove and the balancing system comprises a single pin to be inserted into these two grooves, the balancing system can be generalized so that each of the first and second cylindrical tubes comprises several helical grooves distributed regularly thereon and that the balancing system comprises as many pins to be inserted into the grooves as there are pairs of helical grooves, each pair being formed of a groove in the first tube and a groove in the second tube with opposite pitches.

Claims

CLAIMS 1. Fan module (1) with variable pitch blades for a propulsion unit with a longitudinal axis (X), said module comprising: - a rotating casing (3) around the longitudinal axis (X) and carrying the blades (5), and - a system for changing the pitch (22) of the blades comprising a control device (23) and a connecting mechanism (24), the control device comprising an annular actuator centered on the longitudinal axis (X) having a fixed body (25) attached to the rotating casing and a movable body (27) movable relative to the fixed body, the movable body being coupled to a synchronization ring (34) of the connecting mechanism, said synchronization ring being connected to the blades (5) and configured to be driven in rotation about the longitudinal axis (X) by the movable body so as to change the pitch of the blades;the module being characterized in that it comprises a balancing system (100) comprising a first crown (110) and a second crown (120) each movable in rotation around the longitudinal axis (X), each crown (110, 120) supporting balancing weights at the periphery, the weights being configured to balance the balancing system for a reference setting of the blades, and in that the balancing system is integral with the movable body (27) of the actuator and configured so that a movement of the movable body (27) of the actuator modifying the setting of the blades causes a simultaneous counter-rotating rotation of the first and second crowns (110, 120) of the balancing system.; 2. Fan module according to claim 1, in which the movable body (27) of the actuator is movable in translation relative to the fixed body (25) and in which the balancing system (100) is configured so that a translation of the movable body (27) of the actuator modifying the pitch of the blades causes a simultaneous counter-rotating rotation of the first and second rings (110, 120) of the balancing system.

3. Blower module according to claim 2, wherein the balancing system (100) is configured such that the first ring (110) and the second ring (120) of the balancing system are each axially locked.

4. Blower module according to any one of claims 1 to 3, in which: - the first crown (110) is extended by a first cylindrical tube (140) comprising a first helical groove (142) having a first pitch; - the second crown (120) is extended by a second cylindrical tube (150) surrounding the first cylindrical tube (140) and comprising a second helical groove (152) having a second pitch opposite the first pitch (P1); - the balancing system (100) comprises a pin (160) and a third cylindrical tube (170) coaxial with the first and second cylindrical tubes (140, 150) and surrounding the first and second cylindrical tubes, the third cylindrical tube (170) being integral with the mobile body (27) and having a through orifice (172), the pin (160) being housed integrally in the through orifice (172) of the third cylindrical tube (170) and being inserted into the first and second helical grooves (142, 152).

5. Fan module according to claim 4, in which the first pitch and the second pitch have an absolute value substantially equal to the ratio of a translational displacement of the movable part (27) to the variation in the pitch of the blades corresponding to the displacement.

6. Blower module according to any one of the preceding claims, wherein the balance weights (130A) of the first ring (110) are heavier than the balance weights (130B) of the second ring (120).

7. Blower module according to any one of the preceding claims, in which the balancing system (100) comprises several different sets of balancing weights for the first ring (110) and for the second ring (120).

8. Fan module according to any one of the preceding claims, in which each of the rings (110, 120) has a predetermined number of balancing weights (130) and each balancing weight (130) has an angular position at the periphery of the first ring (110) or the second ring (120), a material and a mass, the number of balancing weights, their angular positions, their materials and their masses depending on characteristics of the blades of the fan module.

9. Fan module according to the preceding claim, in which the characteristics of the blades (5) of the fan module include the radial, tangential and axial weight-moments of the blades.

10. Propulsion assembly (2) with longitudinal axis (X) comprising at least one fan module (1) with variable-pitch blades according to any one of the preceding claims.

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