WO2025040865A1 - Variable-pitch vane of a stationary vane assembly of a turbine engine - Google Patents

Abstract

The invention relates to a variable-pitch vane (13) comprising a vane root (21), a connector (23) carrying the vane root (21) and a hub (25), wherein the vane root (21), the connector (23) and the hub (25) are configured to be pivotably mounted so as to pivot about a pitch axis Y of the vane (13), and wherein the connector (23) is coupled to the hub (25) via a torque transmission system (29) that is configured to transmit a friction torque between the hub (25) and the connector (23), and to allow relative pivoting of the connector (23) and of the hub (25) about the pitch axis Y when the transmitted torque exceeds a predetermined value. The invention also relates to a stationary vane assembly (11) comprising at least one such vane (13), a turbine engine (1) comprising at least one such stationary vane assembly (11), and an aircraft (100) comprising at least one such turbine engine (1).

Description

DESCRIPTION

TITLE: VARIABLE PITCHING BLADE OF A STATIC BLADE OF A TURBOMACHINE

TECHNICAL AREA

The present application relates to the field of turbomachines. The present application relates in particular to a variable-pitch blade of a static blade of a turbomachine, a static blade of a turbomachine, in particular an unducted rectifier of a turbomachine, comprising at least one such blade, a turbomachine comprising at least one such static blade, as well as an aircraft comprising at least one such turbomachine. The invention applies in particular to the unducted rectifier of a turbomachine.

STATE OF THE ART

Turbomachines comprising at least one unducted propeller are known by the English term “open rotor”, “propfan” or “unducted fan”. Such turbomachines may comprise two unducted and contra-rotating propellers (known by the English acronym CROR for “Contra-Rotating Open Rotor”) or a single unducted propeller (known by the English term “unducted single fan”) and a rectifier formed by a static vane whose blades are known by the English acronym OGV for “Outlet Guide Vane”, which is arranged downstream of the unducted propeller. Such a rectifier has the function of straightening the aerodynamic flow at the outlet of the propeller of the turbomachine. The propellers may be placed at the rear of the gas generator (or engine) so as to be of the pusher type or at the front of the gas generator so as to be of the tractor type. These turbomachines are turboprops that differ from turbojets by the use of a propeller outside the nacelle (unducted) instead of an internal fan. This makes it possible to increase the bypass ratio very significantly without being penalized by the mass of the casings or nacelles intended to surround the blades of the propeller or fan.

The stator blades are generally installed on a casing which carries the separation nozzle of the primary flow and the secondary flow circulating respectively in a primary vein and around the inlet casing. Unlike the upstream propeller of a USF type turbomachine, the stator blades are fixed in rotation relative to the axis of rotation of the upstream propeller.

The blades of the static blading are advantageously variable-pitch. For this purpose, each stator blade is pivotally mounted along a pitch axis, each blade root being connected to a pitch change system mounted in the turbomachine. The variable-pitch blades can thus be pivoted during operation of the turbomachine. The The integration zone of the foot and the pivot of the blade is an area strongly constrained by the presence of numerous pieces of equipment around them.

Furthermore, in such turbomachines where weight savings are sought, the variable-pitch blades are preferably made of a composite material comprising a fiber reinforcement embedded in an organic matrix. Thus, in recent turbomachines, large-dimension blades are increasingly frequently made of composite materials with an organic matrix, because these materials allow a significant weight saving with equivalent mechanical properties, or a mechanical gain for an equivalent weight, or both a weight saving and a mechanical gain. The blades of such blades are for example made by laminating two-dimensional fiber reinforcements subsequently densified by resin, or more recently by three-dimensional weaving of a single preform which will subsequently be densified.

When designing and manufacturing composite blades, it is necessary to take into account the blade's resistance to ingestion. For bird risk, certification requirements vary depending on the size of the turbomachine and in particular the diameter of the fan or propeller. These requirements impose impact conditions, i.e. a projectile mass representing a bird impacting the blade, at a certain speed, corresponding to the forward speed of the aircraft at the time of impact. In some cases, it is possible to admit a limited level of damage, which allows the aircraft either to continue its mission or flight without problem, or to land on the tarmac and be repaired. In all cases, the safety of passengers, flight personnel and the populations overflown must be guaranteed. Thus, these requirements are, while certainly restrictive, absolutely essential.

In the case of admissible damage, it must be identifiable with certainty during a ground control inspection. The damage can be located either in the aerodynamic part (in the vein area) or at the attachment level (under the vein). The part under the vein is hidden by a platform that reconstructs the vein to improve the aerodynamics of the turbomachine, this part of the blading is therefore not visible without disassembly.

On conventional shrouded architectures, the design of current rotating blades does not allow any damage at the blade root before the blade breaks. The breakage thus occurs primarily in the blade, i.e. in the visible aerodynamic part, which solves the problem of controlling blade damage.

However, a blade, rotating (fan blade, propeller) or static (OGV), in its design, can present both a naturally high resistance in its blade-forming part, due to the aerodynamic volume, manufacturing tolerances (minimum thickness) and the properties of the materials used, and a naturally low resistance in its foot part, which is located under the vein and is thus not visible unless disassembly is carried out. The low resistance of the foot part results for example from the shape imposed by external needs (such as assembly and disassembly constraints, an external interface constraint), by the available space (generating an integration constraint), and by the dimensions and properties of the materials used (manufacturing constraints).

In this case, the critical area, i.e. the area in which damage can occur, for example during ingestion, is located outside the aerodynamic vein, and is therefore in an area that is not visible unless disassembly is carried out. However, such disassembly is not easy and cannot therefore be carried out regularly, for example during ground control inspection operations.

Document FR 3 132 126 A1 discloses in particular an aircraft engine comprising blades fixed to the casing. Document US 7 112 040 B2 discloses in particular a device for guiding a blade with a variable pitch angle. Document US 2023/257105 A1 discloses in particular a system for controlling the angular pitch of a propeller blade for an aircraft turbomachine. Document US 4 047 840 A discloses in particular shock-absorbing blade supports for blades with a variable pitch angle. Document US 2017/313404 A1 discloses in particular a propeller for an aircraft turbomachine comprising emergency means for setting the blade incidence.

PRESENTATION OF THE INVENTION

An aim of the present application is to remedy the aforementioned drawbacks, by proposing a variable-pitch blade for a static blade of a turbomachine, aiming to avoid a breakage of the blade outside the aerodynamic vein during ingestion while simplifying the control inspection operations.

For this purpose, the invention proposes, according to a first aspect, a variable-pitch blade of a static blade of a turbomachine, the blade comprising a blade root, a fastener supporting the blade root, and a hub, in which the blade root, the fastener and the hub are configured to be pivotally mounted about a blade pitch axis, the fastener being coupled to the hub via a torque transmission system, the torque transmission system being configured to transmit a torque by friction between the hub and the fastener, and being configured to allow relative pivoting of the fastener and the hub about the pitch axis when the torque transmitted by the torque transmission system exceeds a predetermined value. Thus, by introducing such a torque transmission system between the attachment and the hub, the transmission of rotational forces relative to the timing axis is ensured by friction, i.e. by rubbing contact. The maximum transmissible torque can be set such that the attachment and the hub pivot relative to each other, among other words slide against each other, during an ingestion with an energy level that can cause damage to the blades in a non-visible area, more precisely under the vein. In other words, the torque transmissible between the attachment and the hub is limited by the torque transmission system to the predetermined value. The torque transmissible by friction is thus dimensioned in particular for this case of high-energy ingestion. Furthermore, thanks to the torque transmission system, the energy resulting from an impact of an external element with the blade, for example in the case of ingestion, can be at least partially dissipated. The relative pivoting of the attachment and the hub about the timing axis also makes it possible to detect potential damage without requiring the blade to be disassembled from the static blading following ingestion.

According to a second aspect, the invention proposes a static blading of a turbomachine comprising at least one blade conforming to the first aspect.

According to a third aspect, the invention proposes a turbomachine comprising static blading in accordance with the second aspect.

According to a fourth aspect, there is provided an aircraft comprising at least one turbomachine according to the third aspect.

The invention is advantageously and optionally supplemented by the following characteristics, taken alone or in any of their technically possible combinations:

- The hub is configured to be actuated in rotation by a static blade actuation mechanism. Thus, the blade timing is achieved in a simple manner.

- The blade foot is fixed on the clip.

- The blade root, the attachment and the hub are pivotally mounted around a blade setting axis.

- The blade comprises a vane extending longitudinally from the blade root along the pitch axis.

- Static vaning is an unshrouded rectifier.

- The static blading includes a casing. - The hub is pivotally mounted on the static blade housing around the timing axis.

- At least one bearing is arranged between the hub and the static blade housing. This ensures that the hub pivots relative to the housing in a simple and safe manner.

- The timing axis is a radial axis of a static blade casing.

- The static blading casing has at least one vein panel. Thus, the aerodynamics of the static blading are improved.

- The blade extends through a vein of the static blading.

- The torque transmission system is reversible. Thus, the torque is transmissible not only from the hub to the attachment but also from the attachment to the hub.

- The static blading comprises an actuating mechanism, the hub being actuated in rotation by the actuating mechanism. The static blading thus comprises an actuating mechanism for modifying the pitch angle of the at least one blade of the blading in order to adapt the performance of the turbomachine to the different flight phases.

- The torque transmission system comprises an axial clamping member along the setting axis, the axial clamping member axially clamping the fastener and the hub together. Thus, the adjustment of the predetermined value is made possible in a simple manner. In other words, the maximum transmissible torque is adjustable by the axial clamping member.

- The axial clamping member performs axial tightening by screwing. Axial tightening is thus performed simply and safely.

- The axial clamping member comprises a screw. Axial clamping is thus carried out simply and safely.

- The screw extends axially along the setting axis.

- The screw passes through the hub, preferably through a through hole, and is screwed into the fastener. Axial tightening is thus achieved particularly simply and safely.

- The screw passes through the fastener, preferably through a through hole, and is screwed into the hub. Axial tightening is thus achieved particularly simply and safely.

- The axial clamping member includes a spring washer. The predetermined value can thus be adjusted simply and safely.

- The predetermined value is dependent on the axial tightening of the axial clamping member.

- The torque transmission system is formed by at least one surface of the attachment and at least one surface of the hub, which are in frictional contact to transmit a torque by friction between the hub and the attachment. Thus, the friction transmission is achieved simply.

- The torque transmission system has at least one friction lining. Thus, the transmissible torque can be increased. - One end of the attachment is truncated, and is housed in a truncated housing of the hub.

- A truncated surface of the end of the fastener is in frictional contact with a truncated surface of the truncated housing to transmit a torque by friction between the hub and the fastener. Thus, the torque transmission system is realized in a particularly simple manner.

- The truncated end of the attachment is distant from the blade root and is shaped to widen towards the blade root. Thus, the assembly of the blade on the static blading is simplified.

- The truncated hub housing is shaped to widen towards the blade root. This simplifies the assembly of the blade on the static blading.

- The end of the attachment is truncated according to the wedging axis.

- The hub housing is truncated according to the timing axis.

- The torque transmission system comprises at least a first attachment disc and at least a second hub disc.

- Each first attachment disc and the attachment form a sliding connection between them along the wedging axis.

- Each second hub disc and the hub form a sliding connection between them along the timing axis.

- At least one first attachment disc and at least one second hub disc are in frictional contact with each other to transmit a torque by friction between the hub and the attachment. Thus, the torque transmission system is particularly compact.

- Each first attachment disc and each second hub disc are stacked alternately on top of each other along the timing axis. Thus, the transmissible torque can be increased while limiting the space requirement of the torque transmission system.

- A friction lining is arranged on at least one element selected from the group formed by the attachment, the hub, the at least one first attachment disc, the at least one second hub disc. Thus, the transmissible torque can be increased.

- The attachment comprises a first angular stop and the hub comprises a second angular stop, the first angular stop and the second angular stop being angularly offset by a predetermined value about the setting axis, in the absence of angular offset between the attachment and the hub resulting from a relative pivoting of the attachment and the hub about the setting axis. Thus, excessive relative pivoting of the attachment and the hub, and consequently of the blade, is avoided. Such excessive pivoting could disrupt the overall aerodynamics of the turbomachine or excessively increase the forces supported by the static blading.

- The first angular stop and the second angular stop are in contact with each other when a predetermined angular offset is present between the fastener and the hub. This allows for a simple adjustment of the relative pivot limit of the attachment and hub.

- The attachment has a notch. This makes it particularly easy to adjust the relative pivot limit of the attachment and the hub.

- Each end of the notch forms a first angular stop. Thus, an adjustment of the relative pivot limit of the attachment and the hub is carried out in a particularly simple manner.

- The hub has a pin, which is inserted into the notch of the attachment. Thus, an adjustment of the relative pivot limit of the attachment and the hub is carried out in a particularly simple manner.

- The pin forms the second angular stop. Thus, an adjustment of the relative pivot limit of the attachment and the hub is carried out in a particularly simple manner.

- The blade includes a visual indicator, which indicates the presence of an angular offset between the attachment and the hub resulting from a relative pivoting of the attachment and the hub about the pitch axis. Thus, in particular when the aircraft is on the ground, such a visual indicator makes it possible to easily detect a variation in the pitch of the blade, for example of a few degrees, resulting from a relative pivoting of the attachment and the hub about the pitch axis.

- The visual indicator comprises a first indicator element fixed relative to the attachment, and a second indicator element fixed relative to the static blade casing. The visual indicator is thus produced in a simple manner.

- The first indicator element is placed on a platform fixed to the blade foot. Thus, a visual check can be carried out simply, especially on the ground.

- The second indicator element is arranged on a vein panel of the static blade casing. Thus, a visual check can be carried out simply, especially on the ground.

- According to a predetermined angular setting of the blade, in the absence of angular offset between the attachment and the hub resulting from a relative pivoting of the attachment and the hub about the setting axis, the first indicator element is aligned with the second indicator element. Thus, the detection of an absence of variation in the blade setting is particularly simple.

- The predetermined angular setting of the blade corresponds to the setting of the blade when the turbomachine is stopped. Thus, ground detection is facilitated.

- The turbomachine further comprises a shrouded fan or an unshrouded propeller, a compression section and a turbine section, the static blading being at least one of the following bladings: a shrouded fan stator, an unshrouded propeller stator, a compression section stator, a turbine section distributor. DESCRIPTION OF FIGURES

Other characteristics, aims and advantages of the invention will emerge from the detailed description below, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings, given as non-limiting examples and in which:

[Fig. 1] is a schematic view of an example of an aircraft comprising at least one turbomachine according to one embodiment;

[Fig. 2] is a schematic view, in axial and partial section, of an example of a USF type turbomachine comprising a single unducted propeller and a fixed blade, for example an unducted rectifier, comprising at least one blade according to one embodiment;

[Fig. 3] is a schematic sectional view of an exemplary embodiment of a blade according to a first embodiment;

[Fig. 4] is a schematic sectional view of an exemplary embodiment of a blade conforming to a variant of the first embodiment;

[Fig. 5] represents two schematic and partial top views of an exemplary embodiment of a static blading comprising at least one blade conforming to a variant of the first embodiment, in which the blade is in two different operating modes;

[Fig. 6] is a schematic sectional view of an exemplary embodiment of a blade according to a second embodiment.

Throughout the figures, similar elements are designated by identical references.

DETAILED DESCRIPTION

Figure 1 represents an aircraft 100 comprising at least one turbomachine 1, in this example two turbomachines 1. Each turbomachine 1 can be mounted on the aircraft 100 via a pylon.

As shown in FIG. 2, the at least one turbomachine 1 conventionally comprises at least one fan or at least one propeller 3, a compression section 5, a combustion chamber 7, a turbine section 9 downstream of the combustion chamber 7, and an exhaust casing. Furthermore, the at least one turbomachine 1 comprises at least one static (i.e. non-rotating) blade 11, whether it is a static rectifier blade 11 of a fan or a propeller 3, a static rectifier blade 11 of the compression section 5 or a static distributor blade 11 of the turbine section 9. For example, as shown in FIG. 2, the turbomachine 1 is a USF type turboprop comprising an unducted propeller 3, in which case the static blading 11 is an unducted rectifier and extends downstream of the propeller 3. In another example, the turbomachine 1 may be a turbojet comprising a ducted fan, in which case the static blading 11 corresponds to a ducted rectifier extending downstream of the fan.

In the present application, upstream and downstream are defined relative to the direction of flow of the gases through the static blade 11. The axis X is called the axis of rotation of the rotor of the propeller 3 (respectively, of the fan). The axial direction corresponds to the direction of the X axis and a radial direction is a direction orthogonal to this X axis and passing the X axis. Furthermore, the circumferential (or tangential) direction corresponds to a direction orthogonal to the X axis and not passing through the X axis. Unless otherwise specified, internal and external are used in reference to a radial direction such that the internal part or face of an element is closer to the X axis than the external part or face of the same element.

The static blading 11 thus comprises a blade 13 or several blades 13. The static blading 11 also comprises a casing 15 fixedly mounted relative to a casing 17 of the turbomachine 1. It is therefore non-rotating. Each blade 13 of the static blading 11 extends substantially radially relative to the axis X.

A blade 13 is thus defined relative to the axis X of the rotor associated with the static blade 2 (whether it is the axis of rotation of the fan or the propeller 3 for a fan rectifier, the axis of rotation of the compressor rotor for a compression section rectifier 5 or the axis of rotation of the turbine rotor for a turbine section distributor 9 on which it is intended to be mounted.

The blade 13 has variable pitch. The blade 13 is thus pivotally mounted about a pitch axis Y on the static blade 11. The static blade 2 thus comprises an actuating mechanism 19 making it possible to modify the pitch angle of the blade 13 of the static blade 11 in order to adapt the performance of the turbomachine 1 to the different flight phases.

In a first embodiment, shown in FIG. 3, the blade 13 comprises a blade root 21, a fastener 23 and a hub 25. The blade root 21, the fastener 23 and the hub 25 are configured to be pivotally mounted about a setting axis Y of the blade 13. In this example, the blade root 21, the fastener 23 and the hub 25 are pivotally mounted about the setting axis Y of the blade 13. Thus, the hub 25 is pivotally mounted on the casing 15 of the static blade 11 about the setting axis Y. The blade 13 also comprises a vane 27 extending longitudinally from the vane root 21 along the pitch axis Y. Thus, for example, the pitch axis Y is a radial axis of the casing 15 of the static vane 11. In other words, the pitch axis Y extends radially relative to the axis X. The vane 27 has an aerodynamic profile and is placed in an air flow when the turbomachine 1 is operating. Thus, the vane 27 extends through a vein of the static vane 11. For example, the vane 27 and the vane root 21 are made in one piece, from a composite material comprising a fibrous reinforcement densified by a polymer matrix, the fibrous reinforcement comprising, for example, glass fibers.

The attachment 23 carries the blade root 21. In other words, the blade root 21 is fixed to the attachment 23. The attachment 23 is coupled to the hub 25 via a torque transmission system 29.

The hub 25 is rotatably mounted relative to the casing 17 of the static blading 11. For this, at least one bearing 31 is arranged between the hub 25 and the casing 17 of the static blading 11. In this example, two bearings 31 are arranged between the hub 25 and the casing 17 of the static blading 11. The hub 25 is configured to be actuated in rotation by the actuating mechanism 19 of the static blading 11. Such a rotational actuation thus makes it possible to adjust the pitch angle of the blade 13. Thus, the hub 25 is actuated in rotation by the actuating mechanism 19.

The torque transmission system 29 is configured to transmit a torque by friction between the hub 25 and the attachment 23. The torque transmission system 29 is reversible. Thus, the torque is transmissible not only from the hub 25 to the attachment 23, but also from the attachment 23 to the hub 25. Thus, the timing of the blade 13 is achieved in all normal operating phases of the aircraft, in particular the different flight phases.

The torque transmission system 29 is also configured to allow relative pivoting of the attachment 23 and the hub 25 about the setting axis Y. Such pivoting is thus permitted when the torque transmitted by the torque transmission system 29 exceeds a predetermined value. The predetermined maximum value is set such that the attachment and the hub pivot relative to each other during ingestion with an energy level that can cause damage to the blade 13, or more generally to the static blading 11, in a non-visible area, more precisely under the vein.

The torque transmission system 29 comprises an axial clamping member 33 along the setting axis Y. The axial clamping member 33 axially clamps the fastener 23 and the hub 25 together. For example, the axial clamping member 33 performs the axial clamping by screwing. For example, the axial clamping member 33 comprises a screw and a spring washer. In this example, the screw extends axially along the setting axis Y. In a first possibility of this example, the screw passes through the hub 25, preferably through a through hole, and is screwed into the fastener 23. In a second possibility of this example, the screw passes through the fastener 23, preferably through a through hole, and is screwed into the hub 25. In a third possibility of this example, the clamping member 33 is fixed to the hub 25 such as for example for the case of the screw of the clamping member 33, the torque (screw; hub 25) being in one piece and the screw being screwed into the fastener 23. In a fourth possibility of this example, the clamping member 33 is fixed to the fastener 23 such as for example for the case of the screw of the fastener 23, the torque (screw; fastener 23) being in one piece and the screw being screwed into the hub 25.

In this example, the predetermined value is dependent on the axial tightening of the axial tightening member 33. Thus, the predetermined value can be set in a simple manner, by means of the tightening carried out by the axial tightening member 33.

The torque transmission system 29 is also formed by at least one surface SA of the attachment 23 and by at least one surface SM of the hub 25, which are in rubbing contact to transmit a torque by friction between the hub 25 and the attachment 23.

Optionally, the torque transmission system 29 comprises at least one friction lining. For example, a friction lining is arranged on the surface SA of the attachment 23 and/or on the surface SM of the hub 25.

In this example, one end 35 of the attachment 23 is frustoconical, and is housed in a frustoconical housing 37 of the hub 25. The end 35 of the attachment 23 is frustoconical along the setting axis Y, and the housing 37 of the hub 25 is frustoconical along the setting axis Y. The frustoconical end 35 of the attachment 23 is distant from the blade root 21 and formed widening in the direction of the blade root 21. Similarly, the frustoconical housing 37 of the hub 25 is formed widening in the direction of the blade root 21. In order to allow the transmission of torque by friction, the surface SA is a frustoconical surface of the end 35 of the attachment 23, and the surface SM is a frustoconical surface of the frustoconical housing 37. Thus the surface SA is in rubbing contact with the surface SM to transmit a torque by friction between the hub 25 and the attachment 23.

According to a variant of the first embodiment, shown in FIG. 4, the attachment 23 comprises a first angular stop 39 and the hub 25 comprises a second angular stop 41. The first angular stop 39 and the second angular stop 41 are angularly offset by a predetermined value around the setting axis Y, in the absence of angular offset between the attachment 23 and the hub 25 resulting from a relative pivoting of the attachment 23 and the hub 25 around the setting axis Y.

A relative pivoting of the attachment 23 and the hub 25 about the wedging axis Y takes place when the torque transmitted by the torque transmission system 29 exceeds the predetermined value. In such a case, the first angular stop 39 and the second stop angular 41 pivot relatively to each other and are in contact with each other when a predetermined angular offset is present between the attachment 23 and the hub 25.

In this example, the attachment 23 comprises a notch 43. Each angular end of the notch 43 thus forms a first angular stop 39. The hub 23 comprises a pin 45, which is inserted into the notch 43 of the attachment 23. The pin 45 thus forms the second angular stop 41.

According to another variant of the first embodiment, shown in FIG. 5, the blade 13 comprises a visual indicator 47. Such a visual indicator 47 indicates the presence of an angular offset between the attachment 23 and the hub 25 resulting from a relative pivoting of the attachment 23 and the hub 25 around the setting axis Y.

For this, the visual indicator 47 comprises a first indication element 49 fixed relative to the attachment 23, and a second indication element 51 fixed relative to the casing 15 of the static blade 11.

For example and as shown in FIG. 5, seen from the left, according to a predetermined angular setting of the blade 13, in the absence of angular offset between the attachment 23 and the hub 25 resulting from a relative pivoting of the attachment 23 and the hub 25 about the setting axis Y, the first indicator element 49 is aligned with the second indicator element 51. In this example, the predetermined angular setting of the blade 13 corresponds to the setting of the blade 13 when the turbomachine 1 is stopped. Thus, the second indicator element 51 forms a visual reference. Such a visual reference makes it possible to easily visualize an offset relative to the first indicator element 49, as shown in FIG. 5, seen from the right, during a relative pivoting of the attachment 23 and the hub 25 about the setting axis Y, for example following ingestion.

For example, the first indicator element 49 is arranged on a platform 53 fixed on the blade root 21. In this example, the platform 53 is such that a peripheral edge of the platform 53 is circular. For example, the casing 15 of the static blade 11 comprises at least one vein panel 55, the second indicator element 51 being arranged on the vein panel 55. In this example, the platform 53 is flush with the vein panel 55.

Figure 6 schematically represents a blade 13 according to a second embodiment. This blade 13 according to this second embodiment is similar to the blade 13 previously described in the first embodiment, the similar elements being designated by the same references, but is distinguished from the blade 13 previously described in the first embodiment mainly in that the torque transmission system 29 comprises at least one first attachment disk 57 and at least one second disk hub 59. Thus, at least one first attachment disc 57 and at least one second hub disc 59 are in rubbing contact with each other to transmit a torque by friction between the hub 25 and the attachment 23.

On the one hand, each first attachment disk 57 and the attachment 23 form a sliding connection between them along the wedging axis Y. For example, the attachment 23 has a longitudinal section along the wedging axis Y in the shape of a T, each first attachment disk 57 being slidable in the base of the T forming the attachment 23. On the other hand, each second hub disk 59 and the hub 25 form a sliding connection between them along the wedging axis Y. For example, the sliding connection between two elements is produced by a rib of the first element engaged in a notch of the second element, and this in a sliding manner along the wedging axis Y.

In this example, the torque transmission system 29 comprises from two to six first attachment discs 57, preferably four first attachment discs 57, and the torque transmission system 29 comprises from two to six second hub discs 59, preferably four second hub discs 59. Each first attachment disc 57 and each second hub disc 59 are stacked alternately on top of each other along the Y-axis.

In this example, the axial clamping member 33 axially clamps the fastener 23 and the hub 25 together by means of an end disc 61. The end disc 61 is housed in the hub 25 at a distance from the fastener 23 along the setting axis Y. The end disc 61 is in contact, preferably rubbing, with a second hub disc 59. In this example, the hub 25 has an end 63 in the form of a disc, which is interposed between the fastener 23 and a first fastener disc 57. Thus, the hub 25, the at least one first fastener disc 57 and the at least one second hub disc 59 are axially compressed by the axial clamping member 33 between the fastener 23 and the end disc 61.

Optionally, the torque transmission system 29 comprises at least one friction lining. For example, a friction lining is arranged on at least one element chosen from the group formed by the attachment 23, the hub 25, the at least one first attachment disk 57, the at least one second hub disk 59.

The variants of the first embodiment, the first embodiment and the second embodiment can be combined with each other in any technically possible combination.

Claims

1 . Variable-pitch blade (13) of a static blade (11) of a turbomachine (1), the blade (13) comprising: a blade root (21), an attachment (23) carrying the blade root (21), and a hub (25), in which the blade root (21), the attachment (23) and the hub (25) are configured to be pivotally mounted about a setting axis (Y) of the blade (13), characterized in that the attachment (23) is coupled to the hub (25) via a torque transmission system (29), the torque transmission system (29) being configured to transmit a torque by friction between the hub (25) and the attachment (23), and being configured to allow relative pivoting of the attachment (23) and the hub (25) about the setting axis (Y) when the torque transmitted by the transmission system torque (29) exceeds a predetermined value. 2. Blade (13) according to claim 1, in which the torque transmission system (29) comprises an axial clamping member (33) along the setting axis (Y), the axial clamping member (33) axially clamping the attachment (23) and the hub (25) between them. 3. Blade (13) according to any one of claims 1 to 2, in which the torque transmission system (29) is formed by at least one surface (SA) of the attachment (23) and by at least one surface (SM) of the hub (25), which are in rubbing contact to transmit a torque by friction between the hub (25) and the attachment (23). 4. Blade (13) according to claim 3, in which one end (35) of the attachment (23) is frustoconical and is housed in a frustoconical housing (37) of the hub (25), a frustoconical surface (SM) of the end (35) of the attachment (23) being in frictional contact with a frustoconical surface (SA) of the frustoconical housing (37) to transmit a torque by friction between the hub (25) and the attachment (23). 5. Blade (13) according to any one of claims 1 to 4, in which the torque transmission system (29) comprises at least one first attachment disk (57) and at least one second hub disk (59), each first attachment disk (57) and the attachment (23) forming a sliding connection between them along the setting axis (Y), and each second hub disk (59) and the hub (25) forming a sliding connection between them along the setting axis (Y), at least one first attachment disc (57) and at least one second hub disc (59) being in frictional contact with each other to transmit a frictional torque between the hub (25) and the attachment (23). 6. Blade (13) according to any one of claims 1 to 5, in which the attachment (23) comprises a first angular stop (39) and the hub (25) comprises a second angular stop (41), the first angular stop (39) and the second angular stop (41) being angularly offset by a predetermined value around the setting axis (Y), in the absence of angular offset between the attachment (23) and the hub (25) resulting from a relative pivoting of the attachment (23) and the hub (25) around the setting axis (Y). 7. Blade (13) according to any one of claims 1 to 6, which comprises a visual indicator (47), which indicates the presence of an angular offset between the attachment (23) and the hub (25) resulting from a relative pivoting of the attachment (23) and the hub (25) around the setting axis (Y). 8. Static vane (11) of a turbomachine (1) comprising at least one blade (13) according to any one of claims 1 to 7, in which the blade root (21), the attachment (23) and the hub (25) are pivotally mounted around a setting axis (Y) of the blade (13). 9. Turbomachine (1) comprising at least one static blading (11) according to claim 8. 10. Aircraft (100) comprising at least one turbomachine (1) according to claim 9.