ENGINE ASSEMBLY FOR AN AIRCRAFT, COMPRISING A FRONT ENGINE MOUNT INCORPORATED WITH THE BOX OF THE MOUNTING PYLON

An engine assembly for an aircraft, comprising an engine mounting pylon comprising a primary structure forming a box closed by a front closing rib, a front engine mount comprising at least two connecting link rods that are disposed laterally on either side of the box and each comprise a first end mounted on a first fitting of the casing. The rib forms a part of the front mount, comprising at least one transverse fitting made in one piece so as to close a front end of the box and to have lugs protruding laterally on each side of the box, each lug being provided with a first orifice for mounting a second end of one of the link rods.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of the French patent application No. 1753606 filed on Apr. 25, 2017, the entire disclosures of which are incorporated herein by way of reference.

TECHNICAL FIELD

The present invention relates to the field of engine assemblies for aircraft comprising an engine, as well as a device for attaching the engine under a wing of that aircraft. One such attachment device is known from the document FR 3 014 840, for example.

It applies preferentially to commercial aircraft.

BACKGROUND OF THE INVENTION

On existing aircraft, the engines such as turbofan engines are usually attached under the wings by complex attachment devices known as EMS (Engine Mounting Structure), or mounting pylon. The mounting pylons habitually employed have a primary structure, also termed a rigid structure. This rigid structure generally forms a box, i.e., is constructed by assembling upper and lower stringers connected to each other by a plurality of transverse stiffener ribs situated inside the box. The stringers are arranged as upper and lower faces while lateral panels close the lateral faces of the box. Angle brackets can provide the mechanical connection between these constituent elements of the primary structure of the pylon.

In a known manner, the primary structure of an attachment device is designed to enable the transmission to the wings of the static and dynamic forces generated by the engines, such as the weight, the thrust, or once again the various dynamic forces.

In the known prior art solutions, forces are conventionally transmitted between the engine and the primary structure by attachment means consisting of a front engine mount, a rear engine mount and a thrust force absorbing device. These elements generally form an isostatic attachment system.

The front engine mount generally comprises a main body to which are articulated connecting link rods, the other end of which is mounted on a fitting of the fan casing. The main body is pressed against the bottom of the front end of the box and fixed to the latter by bolts that pass through the sole plate of a front closing rib of the box. This arrangement comprises a plurality of parts that render it costly in terms of mass and overall size, in particular in the vertical direction.

There is therefore a need to optimize the design of the front engine mount, in order to reduce its mass and its overall size.

SUMMARY OF THE INVENTION

To address this need, the invention comprises an engine assembly for an aircraft, comprising:an engine comprising a fan casing extended rearwardly by an intermediate casing;a pylon for mounting the engine under an aircraft wing, the pylon comprising a primary structure forming a box closed by a front closing rib;means for attaching the engine to the primary structure of the mounting pylon, the attachment means comprising a front engine mount connecting the primary structure either to the fan casing or to the intermediate casing, the front engine mount comprising at least two connecting link rods that are disposed laterally one either side of the box, and each comprising a first end mounted on a first fitting of the casing.

According to the invention, the front closing rib forms part of the front engine mount comprising at least one one-piece transverse fitting so as to close a front end of the box and to feature lugs protruding laterally on each side of the box, each lug projecting laterally being provided with a first orifice for mounting a second end of one of the connecting link rods.

The invention is therefore noteworthy in that it simplifies the design of the front engine mount, producing a saving in terms of mass and overall size. In particular, the front engine mount has smaller dimensions in the vertical direction, thanks to the integration in one piece of at least a part of the front closing rib of the box and the part that in the prior art formed the attachment main body.

The invention has at least one of the following optional features, separately or in combination.

The one-piece transverse fitting also includes a lug projecting downwardly relative to the box, the lug projecting downwardly being provided with a second orifice for mounting a second fitting of the casing.

Each first mounting orifice and/or the second mounting orifice are oriented in a longitudinal direction X of the engine assembly.

According to a first preferred embodiment of the invention, the front closing rib also comprises, made in one piece with the transverse fitting, at least one of the following elements:a first member for fixing the rib to an upper stringer of the box, the first fixing member projecting rearwardly from the top of the transverse fitting;a second member for fixing the rib to a lower stringer of the box, the second fixing member projecting rearwardly from a lower part of the transverse fitting;at least one third member for fixing the rib to one or more lateral panels of the box, each third fixing member projecting rearwardly from a side of the transverse fitting; andone or more secondary structure support members projecting forwardly from the transverse fitting.

According to a second preferred embodiment, the front closing rib also comprises an additional one-piece transverse fitting superposed on the transverse fitting in a longitudinal direction X of the engine assembly, the two fittings being of substantially the same shape and fixed to each other, preferably by bolts.

In this second embodiment, the front closing rib preferably comprises a one-piece rear fixing fitting comprising at least one of the following elements:a transverse platform superposed on the transverse fittings in the longitudinal direction X;a first member for fixing the rib to an upper stringer of the box, the first fixing member projecting rearwardly from the top of the transverse platform;a second member for fixing the rib to a lower stringer of the box, the second fixing member projecting rearwardly from the bottom of the transverse platform;at least one third member for fixing the rib to one or more lateral panels of the box, each third fixing member projecting rearwardly from a side of the transverse platform.

The front closing rib preferably also comprises a one-piece front support fitting comprising one or more secondary structure support members projecting forwardly from a platform of this front support fitting.

Whichever embodiment is envisaged, the front engine mount is configured to absorb at least forces exerted in a transverse direction Y and in a vertical direction Z of the engine assembly.

The attachment means preferably also include a rear engine mount and lateral link rods for absorbing thrust forces.

The invention also comprises an aircraft comprising at least one such engine assembly.

Other advantages and features of the invention will become apparent in the following nonlimiting detailed description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIG. 1, there is represented an aircraft200comprising a fuselage3to which two wings2are fixed (only one is visible inFIG. 1), each wing carrying one or more engine assemblies5according to the invention. The engine assembly5, also termed a propulsion assembly, includes a turbofan engine10, such as a turbojet, a device4for attaching the engine10, also known as a mounting pylon, as well as a nacelle11surrounding the engine. The engine assembly5is conventionally suspended under its wing2.

Throughout the following description, by convention, the direction X corresponds to the longitudinal direction of the device4that is equally like the longitudinal direction of the turbojet10and that of the engine assembly5, this direction X being parallel to a longitudinal axis9of this turbojet10. On the other hand, the direction Y corresponds to the direction oriented transversely relative to the device4and equally like the transverse direction of the turbojet and that of the engine assembly5, and the direction Z corresponds to the vertical direction or the height, these three directions X, Y and Z being mutually orthogonal.

On the other hand, the terms “front” and “rear” are to be considered relative to a direction of forward movement of the aircraft as a consequence of the thrust exerted by the turbojets10, this direction being represented diagrammatically by the arrow13inFIG. 2. Referring to that figure, the turbojet10includes an external structural envelope formed by various casings. These are, from front to rear, a fan casing20, an intermediate casing22, a central casing24and a gas ejection casing26. The intermediate casing22comprises an exterior cowling28that is in line with and to the rear of the fan casing, with substantially the same diameter. This cowling28carries internally radial structural arms (not shown, also termed structural OGV) that are connected at their internal end to a hub32of the intermediate casing22.

The engine assembly5also includes the mounting pylon of which the primary structure8is represented, but not the secondary structures intended to be mounted on this primary structure8. These secondary structures are conventional and are not described in more detail hereinafter. They provide the segregation and the retention of the systems at the same time as supporting aerodynamic fairing elements.

The primary structure8forms a box, i.e., it is formed by an upper stringer36and a lower stringer38and two lateral panels40(only one can be seen inFIG. 2). These box elements are interconnected by interior transverse stiffener ribs42, which are usually oriented in parallel planes YZ. These ribs are distributed in the box in the direction X. The rib42asituated at the front end is called the front closing rib of the box. It is specific to the present invention, and is described in detail hereinafter. Referring toFIG. 2a, it should be noted that angle brackets43can also be arranged between the elements36,38,40, so as to enable them to be fixed to one another. Alternatively, it is equally possible to provide a more “integrated” box design, in which the same part can form all or part of a plurality of these elements36,38,40.

The primary structure box8is fixed to the wing2by conventional means18, not described. Moreover, the engine10is attached to the box8under the wing by attachment means7preferably constituted of a front engine mount7c, a rear engine mount7aand a device for absorbing thrust forces formed by two lateral link rods7bfor absorbing thrust forces. The rear engine mount7aconnects the ejection casing26to the lower stringer38of the box. The front engine mount7cis for its part specific to the present invention, and connects the front end of the box to the fan casing20, or to the intermediate casing22to its rear and aligned with it. In this latter solution, the front engine mount7cis more preferably connected to the exterior cowling28of this intermediate casing22.

The attachment means7preferably form an isostatic force absorbing system. In fact, as shown diagrammatically inFIG. 3, the front engine mount7chandles only the absorption of forces in the directions Y and Z, while the link rods7babsorb only forces in the direction X. As for the rear engine mount7a, this defines two lateral half-mounts7a′,7a″ arranged on respective opposite sides of the vertical median plane XZ. The first half-mount7a′ is designed only to absorb thrust forces oriented in the direction Z, and the second half-mount7a″ is designed to absorb only thrust forces oriented in the directions Y and Z. In this configuration, the forces exerted in the direction X are therefore absorbed by means of the link rods7b, the forces exerted in the direction Y are absorbed by means of the front engine mount7cand the second rear half-mount7a″, while forces exerted in the direction Z are absorbed conjointly by means of the front engine mount7cand the two rear half-mounts7a′,7a″.

On the other hand, the moment exerted in the direction X is absorbed vertically by means of the two rear half-mounts7a′,7a″, the moment exerted in the direction Y is absorbed vertically by means of these two half-mounts in conjunction with the front engine mount7c, and the moment exerted in the direction Z is absorbed transversely by means of the second rear half-mount7a″ in conjunction with the front engine mount7c.

A first preferred embodiment of the front engine mount7cis described next with reference toFIGS. 4 to 7. The mount7chas the particular feature of being partially integrated into the primary structure8of the pylon, since the front closing rib42aof the box is a component part of that mount7c. To be more precise, in this first preferred embodiment, the front closing rib42ais made in one piece, for example, die stamped. It comprises a plurality of elements made in one piece, including a transverse fitting50substantially oriented in the plane YZ. This transverse fitting50is such that it not only closes the front end of the box8but also has integral lugs for fixing other components of the mount7c.

These are firstly two lugs52projecting laterally on each side of the box, in the direction Y. These two lugs52are preferably arranged symmetrically relative to the vertical median plane XZ of the engine assembly, represented by the section line IV-IV inFIG. 7. They therefore project laterally from the two lateral panels40, extending outwardly and downwardly.

Each of these lugs takes the form of a single fitting, or a yoke, having through it a first mounting orifice54intended for the articulation of a connecting link rod56shown inFIG. 7. Each link rod56is situated laterally relative to the box8, on either side of the latter. They are inclined so as to extend downwardly and laterally outwards. Each of them has a first end mounted on a first fitting58fastened to the fan casing20, or to the exterior cowling28of the intermediate casing. The first two fittings58are therefore lugs projecting upwardly from the casing concerned. Each of them has passing through it a first shear axis60oriented in the direction X.

The other end of each of the two connecting link rods56is mounted in and articulated to the first mounting orifice54of the associated lug52. A second shear axis62, oriented in the direction X like the first orifice54, passes through this same orifice54as well as the second end of the link rod56.

On the other hand, the transverse fitting50is such that it also integrates a lug64projecting downwardly relative to the box. This lug64, in the form of a single fitting or yoke, is intended to be mounted on and articulated to a second fitting66fastened to the associated casing20,28. To this end, a third shear axis68passes through a second orifice70of the lug64and the second fitting66. This third shear axis68and likewise the second orifice70are oriented in the direction X.

Due to making the transverse fitting50and the lugs52,64in one piece, the front mount has a lower mass because of the elimination on the one hand of the bolts usually employed and on the other hand of the increased thicknesses usually adopted for these bolts. The overall size is also reduced, which enables the engine to be moved closer to the pylon in the direction Z, and thus to increase the ground clearance. Moreover, fabrication is rendered easier because of the reduced number of component parts of the front mount7c. Finally, the mechanical strength of the mount is also increased by this, which enables the integration of more powerful engines.

In this first preferred embodiment, the front closing rib42aintegrates other elements made in one piece with the transverse fitting50.

Firstly, this refers to fixing members all extending rearwardly from the transverse fitting50and that together form a structure of substantially square or rectangular section, as shown inFIG. 5. These elements are situated in the interior of the primary structure8, pressed against and fixed to the constituent elements of this primary structure. Fixing is effected in the conventional manner by rivets or by bolts, with diameters for example between 10 and 15 mm inclusive. These bolts/rivets (not shown) therefore pass through the fixing members described in detail hereinafter, the stringers36,38, the lateral panels40and the angle brackets43.

They include a first member74for fixing the rib42ato the upper stringer36. This first fixing member74projects rearwardly from the top of the transverse fitting50. There is also provided a second member76for fixing the rib42ato the lower stringer38, this second fixing member projecting rearwardly from a lower part of the transverse fitting50. Finally, two third members80for fixing the rib42ato the two lateral panels40are also provided, to cooperate two by two. Each third fixing member80projects rearwardly from a side of the transverse fitting50.

The front closing rib42afinally integrates, in one piece with the transverse fitting50and the fixing members, one or more secondary structure support members. Here there is provided a support member84with a U-shaped section shown inFIG. 6, which projects forwardly from the transverse fitting50. This member84supports for example an aerodynamic fairing86and/or systems such as cables.

For so-called “failsafe” safety reasons, the front closing rib42acould be divided into two distinct parts, situated on respective opposite sides of the section plane diagrammatically indicated by the line VII-VII inFIG. 4. The transverse fitting50would therefore be divided into two superposed parts so that in the event of failure of one of them the other can absorb the forces for a particular time.

Accordingly,FIGS. 8 and 9show a second preferred embodiment in which the front closing rib42ahas a shape substantially identical or similar to that of the first embodiment, while being produced in the form of a plurality of distinct parts fixed together, each made in one piece. Because of the similarities between the two embodiments, in the figures, the elements that bear the same reference numbers correspond to identical or similar elements.

The front closing rib42afirstly comprises the transverse fitting50, equipped with its lugs52,64. It is duplicated by an additional transverse fitting50′ which is superposed on it in the direction X of the engine assembly. The two fittings50,50′ are of substantially the same shape and fixed to one another, preferably by bolts or rivets, for example with diameters between 10 and 15 mm inclusive. The additional fitting50′, which is symmetrical to the transverse fitting50about a transverse plane XZ, has a so-called “failsafe” safety function enabling the passage and the transmission of forces coming from the engine, even in the event of failure of the fitting50. Conversely, this “failsafe” function is also provided by the transverse fitting50in the event of failure of the additional transverse fitting50′.

The rib42aalso includes, pressed against and fixed to the transverse fittings50,50′, a one-piece rear fixing fitting88. This fitting88includes firstly a transverse platform90inscribed in a plane YZ and pressed against the additional transverse fitting50′. The platform90has dimensions locally corresponding to the inside cross section of the box. From the top, bottom and sides of this platform90first, second and third fixing members74,76,80respectively extend rearwardly in one piece, being fixed to the elements of the box8in a manner identical or similar to that described in the context of the first embodiment.

Finally, the rib42aalso includes, pressed against and fixed to the transverse fittings50,50′, a one-piece front support fitting92. This fitting92comprises firstly a transverse platform94inscribed in a plane YZ and pressed at the front against the transverse fitting50. The platform94has dimensions locally corresponding to the interior cross section of the box. From this platform94extends a support member84with a U-shaped section, identical or similar to that of the first embodiment. As in that first embodiment, the member84supports, for example, an aerodynamic fairing86and/or systems such as cables.

It is to be noted that segmenting the rib42ainto a plurality of parts enables maintenance operations to be simplified, given that some of these parts can be demounted while the other parts of the rib can remain in place.

Of course, diverse modifications can be made by the person skilled in the art to the invention that has just been described by way of nonlimiting example only.