Thrust reverter comprising an improved system for translationally actuating a movable structure of the reverter

Abstract

The invention relates to a thrust reverser (30) for an aircraft propulsion unit, the reverser comprising a movable structure (29) translationally movable relative to a fixed structure (18) between an advanced forward thrust position and a retracted reverse thrust position, the reverser comprising an actuation system (70) for moving the movable structure, the actuating system consists of one or more actuators (70a, 70bl, 70b2), each actuator comprising an actuating member (72) capable of translational movement and centered on an actuating axis (74), the two movable reverser fairings being arranged symmetrically with respect to each other in a first median plane (P1) of the reverser. According to the invention, in said one or more actuators of the actuation system (70), an eccentric actuator (70a) is provided, the actuation axis (74) of which is circumferentially offset with respect to the first median plane (P1).

Description

Technical Field

[0001] The invention relates to the field of nacelles and thrust reversers for aircraft propulsion units and more particularly to a system for translationally actuating a movable structure of a reverser. Background Art

[0002] Thrust reversers are devices that deflect the air flow across the propulsion unit forward to shorten the landing distance and limit the use of the brakes on the landing gear.

[0003] The cascade reversers currently used in the aviation sector comprise deflection cascades integrated into a fixed or movable structure of the reverser. The movable structure of the reverser comprises one or more movable reverser cowls and is mounted translationally relative to the fixed structure between an advanced forward thrust position and a retracted reverse thrust position.

[0004] In order to deflect at least a portion of the secondary flow towards the cascades in the retracted reverse thrust position, the reverser is usually equipped with a rotating baffle which, when deployed, at least partially closes the secondary flow path. In a known manner, this forces the air of the secondary flow radially outwards towards the cascades, which then generate the reverse thrust air flow forward. The baffle is usually pivotally mounted on a radially inner wall of a movable reverser cowl, which defines the secondary flow path radially to the outside.

[0005] In order to ensure the translational movement of the moving part, the reverser comprises an actuation system generally consisting of a plurality of actuators distributed circumferentially.

[0006] In order to limit the mass and cost of the inverter and thus to reduce harmful emissions (CO, CO2, NO x In order to help reduce the impact of the aircraft on the environment, it is possible to consider reducing the number of actuators within the actuation system while ensuring the required functionality in normal operating mode and in the event of failure of one or more actuators. In particular, these actuators ensure the restoration of the aerodynamic forces exerted on the movable reverser fairing, in particular during the thrust reversal phase.

[0007] Usually, in order to ensure that the force is uniformly restored by the actuator, when the propulsion unit is intended to be suspended under the wing of the aircraft, the actuator is symmetrically arranged relative to the middle plane of the reverser (usually the vertical longitudinal middle plane). Reducing the number of actuators can result in one of the actuators being arranged on this same middle plane, as known from document FR 2 980173 A1 for example. However, in the architecture known as "C" or "D" shaped reverser movable fairing architecture, the actuator centered on the middle plane is located in the locking interface area of ​​the two movable fairings in the folding operating position. This creates potential difficulties when installing the actuator, because the locking interface area of ​​the movable fairing at the 6 o'clock position is usually still a seriously cluttered area due to the presence of equipment and auxiliary equipment.

[0008] Additionally, whether the movable cowl architecture is a "C", "D" or "O" shaped architecture, mounting the actuator at the 6 o'clock position may locally result in an increase in radial dimension toward the bottom of the nacelle, which may be incompatible with the need to maintain adequate ground clearance of the engine assembly. Summary of the invention

[0009] In order to solve the above mentioned problems, the present invention relates to a propulsion unit for an aircraft, the propulsion unit comprising the features according to claim 1 .

[0010] The present invention is therefore similar to a technical breakthrough, making it possible to take into account a reduction in the number of actuators of the movable structure without providing an actuator in an area opposite to the attachment mast (which area corresponds to the area full of locking interfaces between the two movable reverser fairings in the "C"-shaped and "D"-shaped reverser configurations), nor providing an actuator arranged symmetrically with respect to the eccentric actuator with respect to the first middle plane of the reverser.

[0011] Furthermore, whatever the chosen reverser configuration and the number of movable fairings resulting therefrom, the eccentric nature of the actuator positioned relative to the mast makes it possible to overcome the problem of increasing the radial dimension of the nacelle to the ground. Advantageously, the installation of this eccentric actuator does not negatively affect the ground clearance of the propulsion unit.

[0012] By reducing the number of actuators, cost advantages arise, particularly in terms of component costs and assembly costs.

[0013] This also results in a reduction in the mass of the reverser by removing certain actuators and their associated fixings.

[0014] Due to the removal of these means for fixing the actuators, an increase in the surface of the movable fairing that can be equipped with a sound-absorbing coating is also advantageously observed.

[0015] Furthermore, by reducing the number of actuators, better aerodynamics can be achieved through a reduction in the number of access hatches to these actuators.

[0016] Finally, in the case of two movable cowls arranged symmetrically with respect to the first median plane, the installation of the eccentric actuator is greatly facilitated, since it is not located in the area of ​​the cluttered locking interface of the two movable cowls. Obviously, any other actuator constituting the actuation system can be arranged relatively freely to ensure the required functionality both in normal operating mode and in the event of a failure of one or more of these actuators.

[0017] Furthermore, the actuation system consists of an odd number of actuators, preferably three or five actuators, which are circumferentially distributed relative to each other in a regular or irregular manner. This means that the angle between two directly consecutive actuators can be the same or different. According to one possibility falling within the scope of the invention, the actuation system consists of a single actuator.

[0018] Preferably, the present invention provides at least one technical feature of the following optional technical features that are adopted alone or in combination.

[0019] Preferably, the actuation system consists of three actuators, which include:

[0020] - eccentric actuator;

[0021] - Two further actuators, the further two actuators being arranged on either side of the first median plane, preferably symmetrically with respect to the first median plane.

[0022] Preferably, in the case of two movable cowls arranged symmetrically with respect to the first median plane, the eccentric actuator is positioned close to the locking means of the movable reverser cowls.

[0023] Preferably, one of the two movable reverser fairings comprises a beam to which the following components are fixed:

[0024] -guiding means for guiding the translation of the movable reverser cowl;

[0025] - an attachment fitting for a movable actuating member of an eccentric actuator;

[0026] -Part of the locking device for the two movable fairings.

[0027] Advantageously, therefore, the beam integrates multiple functions to benefit in terms of compactness and quality.

[0028] Preferably, the fixed part of the eccentric actuator is fixed to the front frame of the deflection cascade support or to a fixed longitudinal beam of the reverser extending rearwardly from the front frame of the cascade support.

[0029] Preferably, the reverser comprises at least one member associated with at least one of said one or two movable reverser cowls, for limiting the bending of said cowl in the retracted reverse thrust position in the event of a failure of one or more actuators.

[0030] Preferably, the reverser has a C-shaped, D-shaped or O-shaped fairing structure. The invention also applies to the reverse blade cascades that are the fixed structure of the reverser or the movable structure of the reverser.

[0031] Other advantages and characteristics of the invention will become apparent in the following detailed non-limiting description. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The following is a detailed description with reference to the accompanying drawings, in which:

[0033] [ Figure 1 ] is a schematic half view in longitudinal section of a propulsion unit including a thrust reverser shown in a direct thrust configuration;

[0034] [ Figure 2 ] is for Figure 1 A more detailed half view of a reverser equipped on the propulsion unit shown, wherein the reverser is in the form of a preferred embodiment of the invention and is shown in a thrust reverser configuration;

[0035] [ Figure 3 ] is a schematic cross-sectional view of the reverser shown in the aforementioned figures, the left portion showing the fairing in the folded operating position and the right portion showing the fairing in the open maintenance position;

[0036] [ Figure 4 ] is a more detailed schematic cross-sectional view similar to the previous figure and showing the fairing in a folded operational position and in an open maintenance position, the figure being taken along Figure 5 The line IV-IV is intercepted;

[0037] [ Figure 5 ] is a bottom view showing the reverser cowl shown in the preceding figures, the cowl being in a folded operational position;

[0038] [ Figure 6 ] is the inverter and also along Figure 5 A schematic cross-sectional view taken along line IV-IV of , schematically showing the positioning of the reverser actuator;

[0039] [ Fig. 6A ] is a schematic cross-sectional view of a reverser similar to that of the preceding figure, showing an alternative embodiment;

[0040] [ Figure 7 ] is related to Figure 5 A reverser of the invention is a bottom view of a similar reverser, showing more detailed elements of the invention;

[0041] [ Figure 8 ] is a bottom view of one of the two reverser cowls shown in the preceding figure;

[0042] [ Fig. 9 ] is along Figure 7 A cross-sectional view taken along line IX-IX of ;

[0043] [ Fig.10 ] is a schematic diagram showing an alternative solution for fixing the actuator to the reverser;

[0044] [ Fig.11 ] is a schematic diagram showing another alternative solution for fixing the actuator to the reverser;

[0045] [ Fig.12 ] is a schematic diagram showing a solution for limiting the bending of a movable reverser cowl, wherein the cowl is shown in an advanced positive thrust position;

[0046] [ Fig.13 ] is a schematic diagram similar to the preceding figure, wherein the movable cowl is shown in a retracted reverse thrust position;

[0047] [ Fig.14 ] is a schematic diagram showing another solution for limiting the bending of a movable reverser cowl, wherein the cowl is shown in an advanced positive thrust position;

[0048] [ Fig.15 ] is a schematic diagram similar to the preceding figure, wherein the movable cowl is shown in a retracted reverse thrust position;

[0049] [ Fig.16 ] is a schematic diagram showing a further solution for limiting the bending of a movable fairing of a reverser, the movable fairing not being shown in the figure; and

[0050] [ Fig.17 ] is according to an alternative embodiment with Figure 3 A schematic cross-sectional view of a reverser similar to that of a reverser, wherein the reverser has an “O” shaped configuration. DETAILED DESCRIPTION

[0051] Figure 1 An aircraft propulsion unit 1 is shown having a longitudinal centre axis A1 .

[0052] Subsequently, the terms "upstream" and "downstream" are defined relative to the general direction S1 of the gas flow through the propulsion unit 1 along the axis A1 when the propulsion unit 1 generates forward thrust. These terms "upstream" and "downstream" may be replaced by the terms "front" and "rear", respectively, having the same meanings.

[0053] The propulsion unit 1 comprises a turbine 2, a nacelle 3 and a mast (not shown) intended to connect the propulsion unit 1 to a wing (not shown) of an aircraft. In the present case, the propulsion unit is intended to be suspended under the wing of the aircraft by means of the mast, which is therefore located vertically above the turbine. However, other configurations are possible, such as attaching the propulsion unit laterally to the rear of the fuselage.

[0054] The turbomachine 2 is a twin-body twin-flow turbojet engine in this example, which includes, from front to rear, a fan 5, a low-pressure compressor 6, a high-pressure compressor 7, a combustion chamber 8, a high-pressure turbine 9 and a low-pressure turbine 10. The compressors 6 and 7, the combustion chamber 8 and the turbines 9 and 10 form a gas generator. The turbojet engine 2 is provided with a fan casing 11, which is connected to the gas generator via a structural arm 12.

[0055] The nacelle 3 includes a front section forming an air inlet 13 , a middle section having two fan cowls 14 surrounding the fan casing 11 , and a rear section 15 .

[0056] In operation, the air flow 20 enters the propulsion unit 1 via the air inlet 13, passes through the fan 5, and is then divided into a main flow 20A and a secondary flow 20B. The main flow 20A flows in a primary gas flow path 21A passing through the gas generator. The secondary flow 20B flows in a secondary flow path 21B around the gas generator. The secondary flow path 21B is radially inwardly defined by a fixed inner fairing surrounding the gas generator. In this example, the fixed inner fairing includes a first section 17 belonging to the middle section 14 and a second section 18 extending rearward from the first section 17 to form a part of the rear section 15.

[0057] This second section 18 is part of the fixed structure of a thrust reverser, which will be described below and is also centred on the axis A1 . This second section will subsequently be referred to as the radially inner delimiting wall 18 of the secondary flow path 21B.

[0058] On the radially outer side, the secondary flow path 21B is defined by the fan housing 11. Figure 1In the configuration of , the two movable reverser fairings 33 form part of the rear section 15 of the nacelle 3. More precisely, between the fan casing 11 and the two reverser fairings 33, there is arranged a casing 40 of an intermediate casing 42, which comprises the aforementioned structural arms 12, the radially outer ends of which are fixed to this casing 40. Thus, this casing 40 also participates in defining the secondary flow path 21B radially to the outside by being situated in the downstream axial extension of the fan casing 11.

[0059] Therefore, the nacelle 3 includes a thrust reverser 30 (at Figure 1 1 ), the thrust reverser is centered on the axis A1 and comprises, on the one hand, a fixed structure 31 fixed to the fan casing 11 and, on the other hand, a movable structure 29 movable relative to the fixed structure 31. The fixed structure 31 comprises, for example, a front frame 46, which preferably connects the fixed structure 31 to the fan casing 11 via a knife-edge assembly located downstream of the casing 11. The front frame 46 contains a shaped aerodynamic part called a deflection edge 46B, which guides the flow in the reverse jet.

[0060] In this preferred embodiment, the fixed structure 31 also comprises a plurality of deflection blades 32 arranged adjacent to one another around the axis A1 in the circumferential direction of the reverser 30 and of the propulsion unit 1 .

[0061] In addition, movable structure 29 comprises above-mentioned two movable reverser fairings 33 again, and two movable reverser fairings correspond to two fairings 33 with roughly semi-cylindrical shape, and each movable reverser fairing extends on the angular amplitude of about 180 °.Especially, this configuration with two fairings 33 is very suitable for the situation of nacelle design, wherein, fairing / wall 18 is also hingedly installed, and then reverser 30 has the architecture called "D-shaped" architecture (known name is "D-shaped duct").In this architecture, fairing 18,33 are connected to open / close simultaneously during the maintenance operation of engine.However, other architectures are also possible, such as the architecture called "C-shaped" architecture (known name is "C-shaped duct"), wherein, the fairing 18 of inner structure can be hinged independently of two movable fairings 33.

[0062] Each movable reverser cowl 33 comprises a radially outer wall 50 forming an outer nacelle aerodynamic surface, and a radially inner wall 52 participating in defining radially to the outside a secondary flow path 21B. In the forward thrust configuration, this wall 52 is located in the downstream continuation of the deflection edge 46B. The two walls 50, 52 define a housing 54 axially open at the upstream end of the reverser cowl 33, wherein at least a portion of the cascade 32 is in the forward thrust configuration.

[0063] Figure 1 The reverser 30 is shown in a forward thrust configuration (called "forward jet"), which corresponds to the standard flight configuration. In this configuration, the fairings 33 of the movable structure 29 are in a closed position, called forward thrust or "forward jet" position, in which these reverser fairings 33 bear on the fixed structure 31, in particular on the deflection edge 46B forming an integral part of the fixed structure 31. In fact, in the forward thrust configuration, the upstream end 52A of the radially inner wall 52 of each fairing 33 bears axially against the deflection edge 46B.

[0064] Thus, the movable structure 29 can be moved relative to the fixed structure 31 along the axis A1 of the reverser. Figure 1 The movable structure 29 is movable in translation between the forward forward thrust position shown and the retracted reverse thrust position to be described later. In the forward forward thrust position of the movable structure 29, the deflection cascades 32 are arranged in housings 54 of the reverser cowlings 33, which are separated from the secondary flow path 21B by radially inner walls 52 of these sliding cowlings 33. This wall 52, which forms the outer wall of the secondary flow path, is also called an acoustic inner panel.

[0065] The retracted reverse thrust position of the movable structure 29 is Figure 2 . In this figure, the retracted sound-absorbing inner panel 52 of the reverser cowl is shown to expose, upstream, an opening 56 for the passage of the secondary flow path 21B towards the deflection cascade 32. Thus, the opening 56 is also delimited upstream by a deflection edge 46B, which opens radially outwards towards the rear to delimit the air flow intended to pass through the cascade 32 when the movable system is in this retracted reverse thrust position. In other words, the deflection edge 46B moves gradually away from the axis A1 from the front to the rear to guide / deflect the air towards the cascade 32 in the thrust reversal configuration.

[0066] In order to deflect at least a portion of the secondary flow 20B toward a passage opening 56 axially defined between the upstream end 52A of the radial inner wall 52 of each fairing 33 and the deflection edge 46B, the reverser 30 generally includes a door 58 deployed in the flow path 21B. These doors 58 force at least a portion of the secondary flow 20B to be directed toward the opening 56 by closing the flow path, and force at least a portion of the secondary flow 20B to pass through the fixed cascade 32 to obtain the desired reverse thrust function.

[0067] As previously mentioned, the reverser has a D-shaped fairing configuration, i.e. each fairing 33 forms an outer fairing associated with an inner fairing formed by the wall 18. Each assembly can then be similar to a single fairing 60 hinged at the upper end on the attachment mast 59 so as to be able to pivot from a folded operating position to an open maintenance position, these positions being Figures 3 to 5 Shown in.

[0068] Two fairings 60 are arranged symmetrically with respect to the first middle plane P1 of the reverser, and the first imaginary plane is a vertical longitudinal plane here, which passes through the axis A1 and intersects with the mast 59 in the middle of the vertical longitudinal plane. Therefore, each fairing 60 includes a movable outer reverser fairing 33 and a fixed inner fairing 18, and each fairing has a semi-cylindrical shape. At the ends of the fairings 33 and 18, the fairings 33 and 18 are connected by upper branches 62a and lower branches 62b. Two fairings 60 are arranged on both sides of the first middle plane P1, and the two upper branches 62a are also arranged at a distance on both sides of the plane P1, for passing the upper fixed longitudinal beam 64a. The two upper branches 62a are at a clock position close to 12 o'clock relative to the axis A1. Similarly, the two lower branches 62b are also arranged at a distance on both sides of the plane P1, for passing the lower fixed longitudinal beam 64b. The two lower branches 62b are still at a clock position close to 6 o'clock relative to the axis A1. At the rear end of the fairing 60, behind the lower fixed beam 64b, the two lower branches 62b are closer to each other, and the space defined between the two lower branches 62b is used for the installation of equipment and the passage of auxiliary equipment 66, such as in Figure 4 Preferably, the passage of the auxiliary equipment is carried out over the entire length of the branch. At these rear ends, the two movable fairings 33 are provided with conventional locking devices 68 near the lower branch 62b, also in Figure 4 Schematically shown in FIG. These locking devices 68 are crossed by the first middle plane P1 and make it possible to keep the two fairings 60 together in the folded operating position. In addition, the fairing locking devices are located on the first side of the second middle plane P2 of the reverser, which is perpendicular to the first middle plane P1 and also passes through the axis A1, by being positioned close to the lower branch 62b. In other words, the locking devices 68 are located on the lower side of the second imaginary middle plane P2 oriented longitudinally and transversely.

[0069] Although the two outer and inner fairings 33, 18 form part of the same articulated fairing 60, the two outer and inner fairings 33, 18 forming part of the same articulated fairing 60 are designed to be able to move axially relative to each other in order to bring the reverser from a forward thrust configuration to a thrust reverser configuration or vice versa. To this end, the reverser is equipped with a translation actuation system 70, so that the entire movable structure 29 of the reverser can be moved relative to the fixed structure 31.

[0070] Now refer to Figure 6 , an actuation system 70 is shown, which therefore represents the only system in the reverser dedicated to the axial translational movement of the movable structure 29. The system 70 is here composed of three actuators 70a, 70b1, 70b2, each equipped with an actuation member 72, which is movable in translation and is centered on an actuation axis 74 oriented longitudinally.

[0071] One of the particularities of the invention is that the actuators 70a, 70b1, 70b2 no longer form a set of actuators that are symmetrical relative to the first median plane P1, in particular since one of the actuators 70a, 70b1, 70b2 forms an eccentric actuator 70a that is arranged on a first side of the second median plane P2, corresponding to the side opposite to the side where the mast is located. In fact, the actuation axis 74 of the eccentric actuator 70a is circumferentially offset relative to the first median plane P1 and the eccentric actuator 70a remains asymmetrical relative to the first median plane P1 relative to each of the other two actuators 70b1, 70b2. In other words, neither of the other two actuators 70b1, 70b2 of the actuation system 70 is arranged symmetrically relative to the first median plane P1 relative to the eccentric actuator 70a.

[0072] In the case of three actuators selected for this embodiment, the eccentric actuator 70a is still located near the locking device 68, preferably at an angular position between 155° and 175°. Preferably, the eccentric actuator 70a is arranged circumferentially offset relative to the lower branch 62b of the fairing 60 with which it is associated, even if this offset in the circumferential direction 76, in the direction away from the other fairing 60, can be kept small or even very small.

[0073] Due to this specific positioning of the eccentric actuator 70a, completely different from the configurations known in the prior art, the installation of the eccentric actuator 70a is easy because the installation of the eccentric actuator 70a is carried out at a distance from the cluttered area where the locking device 68 is located and the auxiliary equipment and equipment 66 in the space between the two lower branches 62b.

[0074] The other two actuators 70b1, 70b2 constituting the actuation system 70 are sequentially arranged on the same second side of the second middle plane P2 (i.e., on the upper side where the mast 59 is located), and are also arranged on both sides of the first plane P1. The three actuators 70a, 70b1, 70b2 can be together regularly distributed relative to each other in the circumferential direction 76, such as Figure 6 As can be seen in , other arrangements are still possible without departing from the scope of the invention. In the case of a regular distribution, the other two actuators 70b1 , 70b2 are therefore asymmetric with respect to the first median plane P1 .

[0075] In this regard, it should be noted that, in particular in the thrust reversal configuration, the distribution of the actuators is substantially determined by the restoration of the aerodynamic forces on the fairing 60 .

[0076] Another preferred configuration is Fig. 6A . This configuration consists in providing two actuators 70b1, 70b2 arranged symmetrically relative to each other and relative to the first median plane P1. Since the distances between each of the two actuators and the guidance systems associated with the two actuators are the same or substantially the same, this configuration reduces the risk of the fairing getting stuck during its translation.

[0077] In the described embodiment, the number of actuators 70a, 70b1, 70b2 constituting the actuation system 70 is fixed to three, but the number of actuators may be different (e.g. five) while keeping an odd number with an optimized distribution to limit the number to save cost and quality.

[0078] It should be noted that the actuators 70a, 70b1, 70b2, which are preferably oriented parallel to the axis A1, are actuators of conventional design, for example in the form of electric cylinders, hydraulic cylinders or ball or roller screws.

[0079] Now refer to Figures 7 to 9 , the fairing 60 is shown to cooperate with the eccentric actuator 70a. The articulated fairing 60 has a movable fairing 33 of the articulated fairing 60 and located on the lower edge of the movable fairing 33, the movable fairing 33 is equipped with a beam 78 oriented generally axially. The beam 78 has the characteristics of providing multiple functions, which will be described below.

[0080] Firstly, the main axially oriented part of the beam 78 carries fixedly guide means 80 for guiding the translation of the mobile fairing 33. These guide means 80 are, for example, in the form of rails which cooperate with complementary rails 82 fixed on the lateral sides of the fixed beam 64b so as to enable satisfactory translation of the mobile structure 29. It should be noted that preferably, the eccentric actuator 70a is therefore also arranged circumferentially offset relative to the guide means 80 and the rails 82, in a direction away from the other fairing 60.

[0081] In addition to fixing the guide device 80 to the beam 78 of the movable fairing 33 , the attachment fitting 84 of the movable actuating member 72 of the eccentric actuator 70 a is also fixed to a main axially oriented part of the beam 78 , preferably also towards the rear.

[0082] Finally, at the rear end of the beam 78 , a portion 68 a of the locking device 68 is fixed to the rear end of the beam 78 , which is bent until it adopts a circumferential orientation and defines axially towards the rear a housing space for the fixed beam 64 b .

[0083] On the other fairing 60 , similar means are also fixed to the beam 78 of the other fairing 60 , in addition to the attachment fitting 84 of the movable actuating member 72 .

[0084] exist Figure 7 and Figure 8 In the embodiment, the fixing member 86 of the eccentric actuator 70a is fixed to the front frame 46 supporting the cascade 32. More specifically, the fixing member 86 of the actuator 70a has a front end portion fixed to the front frame 46 supporting the cascade, and the fixing member 86 protrudes axially toward the rear.

[0085] Alternatives in Fig.10 and Fig.11 In Fig.10 , the fixing member 86 of the eccentric actuator 70a remains fixed to the front support frame 46 of the cascade 32. The dashed line joint 63 between the beam 64b at the 6 o'clock position and the front support frame 46 of the cascade 32 is located angularly between the eccentric cylinder 70a and the beam 64b.

[0086] exist Fig.11 In the embodiment, the fixing part 86 of the eccentric actuator 70a is fixed near the front support frame 46 of the cascade 32, fixed on the fixing beam 64b, fixed at the circumferential protrusion of the fixing beam 64b. Then, the joint area 63 between the beam 64b and the front support frame 46 of the cascade 32 is angularly / circumferentially offset from the cylinder 70a in the opposite direction to the other fairing 60.

[0087] The cascade vanes 32 may be slightly circumferentially offset from the stationary beam 64 b to provide the space necessary to accommodate the stationary actuator component 86 .

[0088] The following figures show different technical solutions for limiting the risk of bending of one or both movable fairings 33 in the event of a failure of one or more actuators 70a, 70b1, 70b2. In practice, these actuators ensure that the movable fairings 33 are kept in place, or even that all the fairings 60 are kept in place, in particular in the thrust reversal configuration, and specific means can be implemented to avoid such bending that could occur under the effect of the aerodynamic forces exerted on the fairings.

[0089] exist Fig.12 and Fig.13 , a first solution consists in arranging an axial stop 90a on the front end of the movable fairing 33 and a complementary axial stop 90b on the fixed beam 64b. The two stops 90a, 90b are intended to come into contact only in the retracted reverse thrust position of the movable fairing 33. In addition, preferably, a plurality of pairs of stops of this type are distributed circumferentially around the axis A1 in a regular or irregular manner.

[0090] exist Fig.14 and Fig.15 In FIG. 4 , a complementary axial stop 90 b is located on the rear frame 46 c supporting the cascade 32 .

[0091] Finally, in Fig.16 In the embodiment, the complementary axial stop 90b is still located on the rear frame 46c supporting the cascade blades 32, but the complementary axial stop 90b is connected to an axial spar 92 located between the cascade blades 32. This spar 92 transfers the forces experienced by the stop 90b directly into the front support frame 46 to provide better force absorption.

[0092] Various modifications may be made to the invention just described by those skilled in the art, by way of non-limiting examples only, and the scope of the invention is defined by the appended claims. For example, alternatively, the thrust reverser 30 may have a "C"-shaped architecture still with two movable fairings 33, or an "O"-shaped architecture with a single movable fairing 33 extending over an angular amplitude of nearly 360° and interrupted only at the 12 o'clock position by the upper fixed longitudinal beam 64a, as Fig.17 As another example, the propulsion unit may be arranged laterally in the rear part of the fuselage.

[0093] Furthermore, in various embodiments and alternatives to these embodiments, all features disclosed above may be combined with one another.In addition, it should be noted that in all the above figures, elements with the same reference numerals correspond to the same or similar elements.

Claims

1. A propulsion unit (1) for an aircraft, comprising a turbine (2), a nacelle (3) having at least one fan fairing (14), an attachment mast for attaching the turbine, and a thrust reverser (30), the thrust reverser comprising a fixed structure (31) provided with a radially inner delimiting wall (18) of a secondary flow path (21B) of the propulsion unit intended to be traversed by a secondary flow (20B), the reverser further comprising a movable structure (29) comprising one or more movable reverser fairings (33), each of which is provided with a radially inner reverser fairing wall (52) radially delimiting the secondary flow path (21B) to the outside, the reverser further comprising at least one deflection cascade (32), the movable structure being capable of being moved along a longitudinal center axis (A1) of the reverser. ) is translationally movable relative to the fixed structure between an advanced forward thrust position and a retracted reverse thrust position, the reverser comprising an actuation system (70) for moving the movable structure between an advanced forward thrust position of the movable structure and a retracted reverse thrust position of the movable structure, the actuation system being composed of one or more actuators (70a, 70b1, 70b2), each actuator comprising an actuation member (72) that is translationally movable and centered on an actuation axis (74), the reverser having a first mid-plane (P1) of the reverser and a second mid-plane (P2) of the reverser, the first mid-plane passing through the longitudinal center axis (A1) and intersecting the attachment mast, the second mid-plane passing through the longitudinal center axis (A1) and being perpendicular to the first mid-plane (P1), It is characterized in that Among the one or more actuators of the actuation system (70), there is provided an eccentric actuator (70a) arranged on a first side of the second middle plane (P2), the first side being opposite to a second side of the second middle plane (P2) on which the attachment mast is located, and an actuation axis (74) of the eccentric actuator is circumferentially offset relative to the first middle plane (P1), wherein, in the case of a plurality of actuators constituting the actuation system (70), the eccentric actuator (70a) is asymmetric relative to each of the other actuators (70b1, 70b2) relative to the first middle plane (P1), And wherein the actuation system (70) consists of an odd number of actuators (70a, 70b1, 70b2), preferably three or five actuators, which are circumferentially distributed relative to each other in a regular or irregular manner.

2. The propulsion unit according to claim 1, characterized in that The actuation system (70) is composed of three actuators (70a, 70b1, 70b2), and the three actuators include: - said eccentric actuator (70a); - two further actuators (70b1, 70b2) arranged on either side of said first median plane (P1), preferably symmetrically with respect to said first median plane.

3. A propulsion unit according to any one of the preceding claims, characterised in that One of the two movable reverser fairings (33) comprises a beam (78) to which the following components are fixed: - guiding means (80) for guiding the translation of the movable reverser cowl (33); - an attachment fitting (84) for the movable actuating member (72) of the eccentric actuator (70a); - a portion (68a) of the locking device (68) for the two movable fairings (33).

4. A propulsion unit according to any one of the preceding claims, characterised in that The fixing part (86) of the eccentric actuator (70a) is fixed to the front frame (46) of the deflection blade support (32), or to the fixed longitudinal beam (64b) of the reverser extending rearward from the front frame (46) of the blade support.

5. A propulsion unit according to any one of the preceding claims, characterised in that The propulsion unit comprises at least one member (90a, 90b) associated with at least one of the one or two movable reverser fairings (33), the at least one member being used to limit the bending of the movable fairing in the retracted reverse thrust position in the event of a failure of the one or more actuators (70a, 70b1, 70b2).

6. A propulsion unit according to any one of the preceding claims, characterised in that The reverser has a C-shaped, D-shaped or O-shaped fairing structure.

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