FR2900979A1 - Engine assembly for aircraft, has flange with circular recess and receiving circular projections pertaining to internal fastening clips, where flange projects radially towards exterior and recess is radially opened towards interior - Google Patents

Abstract

The assembly has a fixation unit (30) with an external circular docking flange (50) maintained fixedly around an internal fastening clip (32) connected to an engine casing (10) and another internal fastening clip (34) connected to a gas exhaust cone (8). The flange has a circular recess (52) radially opened towards the interior. The flange receives circular projections (38, 42) pertaining to the clips, respectively, and projects radially towards the exterior. The projections are placed one against the other in the recess. The recess has a V shaped section radially opened towards the interior. An independent claim is also included for a method of assembling a motor assembly.

Description

AIRCRAFT ENGINE ASSEMBLY COMPRISING A MONTE GAS EJECTION CONE

  TECHNICAL FIELD The present invention relates generally to an engine assembly for an aircraft comprising an engine having a crankcase, this assembly also comprising a fan cone. ejection of gases defining a radially inner skin of an annular primary flow channel, this ejection cone being fixedly attached to a rear end of the motor housing. The engine assembly according to the invention also comprises an attachment pylon which makes it possible to suspend an engine such as a turbojet engine below the wing of the aircraft, or to mount this engine over the same. wing, or even to assemble this engine on a rear fuselage of the aircraft. STATE OF THE PRIOR ART In the motor assemblies known from the prior art, the gas ejection cone is usually bolted onto a rear end of the crankcase. However, the multitude of bolts angularly distributed about the longitudinal axis of the engine, between the rear end of the crankcase and the front end of the gas ejection cone, also called plug, inevitably leads to the risk of bad assembly. may lead to local damage, overall performance losses for the motor assembly, or even a partial or total loss of the ejection cone. In addition, the mass of these attachment means is important, and therefore penalizing. At the same time, their assembly time is also relatively high, so that the assembly of the motor unit can not be considered fully optimized. Moreover, for obvious reasons of limiting the aerodynamic disturbances of the primary flow conforming to the ejection cone, the bolts employed must lie internally with respect to the cone, which implies necessarily to provide internal access to the same cone for the cones. operators. Generally, this access is obtained by making the gas ejection cone in two distinct portions, the first upstream portion mounted first, providing at its rear end an opening for the operators assembling the aforementioned bolts. Then, it is the turn of the second downstream portion, that is to say the one defining the end of the cone, to be assembled on the upstream portion, for example also by bolting with the aid of an intermediate clamping flange interposed between the two constituent portions of the gas ejection cone.

  Naturally, this way of doing things is appreciably restrictive in terms of the overall mass generated and overall aerodynamic performance of the engine assembly.

  SUMMARY OF THE INVENTION The purpose of the invention is therefore to propose an aircraft engine assembly at least partially overcoming the disadvantages mentioned above, relating to the embodiments of the prior art.

  To do this, the subject of the invention is an engine assembly for an aircraft comprising a motor having a crankcase, this assembly also comprising a gas ejection cone defining a radially inner skin of an annular primary flow channel, this ejection cone is fixedly attached to a rear end of the motor housing by means of fixing means. According to the invention, the fastening means comprise an external junction flange fixedly held around a first internal fastening flange integral with the motor casing and an integral inner of the external circumferential junction cone open second ejection fastening flange gas, the flange having a notch radially inward and receiving on the one hand a first circumferential projection belonging to the first inner fixing flange and projecting radially outwards, and on the other hand a second projection circumferential member belonging to the second internal fastening flange and also projecting radially outwardly, the first and second circumferential projections housed in the circumferential notch being pressed against each other. Thus, the invention proposes to use an external junction flange coming to cover the two internal fastening flanges to ensure the mechanical connection between the crankcase and the gas ejection cone. Therefore, it is no longer necessary to use a multitude of bolts angularly distributed around the longitudinal axis of the motor as was the case in the prior art, which can significantly reduce or even completely eradicate the risks. poor mounting likely to lead to local damage, overall performance losses for the motor assembly, or even a partial or total loss of the ejection cone. In addition, the mass of these fastening means is substantially lower compared to that previously encountered, and their assembly time is also greatly reduced.

  As such, it is noted that the assembly of the gas ejection cone on the rear end of the crankcase is generally facilitated by the fact that the fastening means according to the invention do not require an interior access to the cone for the operator, since the junction flange just be placed around the crankcase and the same cone. This specificity advantageously implies that it is no longer necessary to provide a gas ejection cone in two distinct portions fixedly attached to one another, as was the case in the prior art. As will be indicated below, the cone can then be made preferentially in one piece. Preferably, the circumferential notch has a generally V-shaped section open radially inwardly. This allows, when clamping in the radial direction of the connecting flange carrying the aforementioned notch, to ensure a clamping in the longitudinal direction of the first projection against the second projection, which therefore each preferably have a surface of form complementary to that of the branch of the V with which it cooperates. Furthermore, the outer junction flange is in the form of a plurality of angular sectors distributed around a longitudinal axis of the motor. This ensures easy assembly and disassembly of this joining flange, the angular sectors can then for example be hinged to each other at their ends, while having two free and adjacent sector ends. However, we can prefer a configuration in which the angular sectors are not articulated to each other, in particular to give maximum flexibility to the flange, in order to allow easy assembly. In addition, it is desired to dissociate the circumferential displacement of the clamping strap (described below) during its tensioning, relative to the angular sectors so that they do not move circumferentially vis-à-vis the internal clamps with which they cooperate. The tightening of the strap then simply causes a radial pressurization of the angular sectors forming the outer junction flange, which, thanks to the circumferential notch generally V-shaped open radially inwards, allow to ensure the clamping in the longitudinal direction of the first projection against the second projection. As mentioned above, the gas ejection cone is made in one piece, implying that it can be entirely mounted on the crankcase by assembling the fastening means of the present invention, exclusively located between the rear end of the crankcase and the front end of the ejection cone. In other words, this cone advantageously no longer has a design in two upstream and downstream portions requiring to be fixedly attached to one another, only after the attachment of the upstream portion on the crankcase.

  This then results in a significant decrease in the overall mass of the assembly, in particular because of the suppression of the intermediate fastening flange employed in the prior art embodiments to establish the junction between the upstream portion and the downstream portion of the assembly. cone. This reduction of the mass advantageously generates a reduction of the loads at the recess of the ejection cone on the crankcase, which makes it possible to reduce the dimensioning of the front part of this cone provided in one piece, and therefore of further increase the achievable mass gain.

  In addition, in addition to the fact that the mounting time is further reduced, this particular design of the gas ejection cone also allows a gain in terms of aerodynamic performance, insofar as the primary flow is no longer disturbed by a junction between the upstream portion and the downstream portion of the cone. Still preferentially, the outer junction flange is fixedly held around the first and second internal fastening flanges by means of at least one tightening strap placed around this outer junction flange. This strap, which thus ensures the clamping of the connecting flange in the radial direction, can take any form known to those skilled in the art, and for example be of the type operable by hand and / or with a tool. Preferably, the assembly is designed such that a powering up of the at least one tightening strap causes, through the external connecting flange, clamping in the longitudinal direction of the first projection against the second protrusion, and therefore a tightening in the same longitudinal direction / axial ejection cone against the crankcase. As such, it is noted that the tensioning of said at least one tightening strap, designed to cause clamping in the radial direction of the joining flange, is carried out using a mechanism preferably using a manual lock. In addition, the mechanism and strap referred to above are preferably made of doubled element to provide a security function called Fail Safe, as known to those skilled in the art. The invention also relates to an aircraft comprising at least one engine assembly such as that described above, assembled on a wing or on a rear fuselage of this aircraft. Finally, the subject of the invention is a method of assembling an engine assembly such as that described above, comprising the following steps; positioning the gas ejection cone in the extension of the rear end of the crankcase, preferably so that the first and second circumferential projections are pressed against each other in the longitudinal direction of the engine assembly ; - Establishing the outer junction flange to accommodate the first and second circumferential projections within the circumferential notch of the outer junction flange; and - tightening the outer junction flange around the first and second internal fixing flanges, this clamping being preferably carried out in the radial direction of the motor assembly, using at least one clamping strap. Nevertheless, other means could be used to maintain and tighten the junction flange around the first and second internal fastening flanges, such as means for clamping the junction flange in the circumferential direction, without leaving of the scope of the invention.

  Other advantages and features of the invention will become apparent in the detailed non-limiting description below. BRIEF DESCRIPTION OF THE DRAWINGS This description will be made with reference to the appended drawings among which; - Figure 1 shows a side view of an engine assembly for aircraft, according to a preferred embodiment of the present invention; - Figure 2 shows a partial exploded perspective view of the motor assembly shown in Figure 1, schematically fixing between the motor housing and the gas ejection cone of the assembly; - Figure 3 shows a sectional view of the fastener shown in Figure 2; and FIGS. 4a and 4b schematically show the design of the outer junction flange belonging to the fastener shown in FIGS. 2 and 3, respectively in a state where this junction flange is not yet tightened around the first and second flanges. internal fasteners belonging to the motor assembly, and in a state where this connecting flange is clamped around these same internal fastening flanges.

  DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring firstly to FIG. 1, an engine assembly 1 for an aircraft intended to be fixed under a wing of this aircraft (not shown) is shown, this assembly 1 generally comprising a device attachment 4, a motor 6 such as a turbojet hooked under this device 4, and a nacelle 3 surrounding the turbojet engine 6. In addition, it comprises a gas ejection cone 8 (English plug) extending a crankcase 10, this cone 8 defining a radially inner skin of an annular channel 12 of primary flow 14, centered on the longitudinal axis 5 of the turbojet engine 6. In the following description, by convention, X is called the longitudinal direction of the device 4 which is also comparable to the longitudinal direction of the turbojet engine 6, this direction X being parallel to the longitudinal axis 5 of this turbojet engine. On the other hand, Y is referred to as the tractive direction. nsversalement relative to the device 4 and also comparable to the transverse direction of the turbojet engine 6, and Z the vertical direction or the height, these three directions X, Y and Z being orthogonal to each other. On the other hand, the terms front and rear are to be considered with respect to a direction of advancement of the aircraft encountered following the thrust exerted by the turbojet engine 6, this direction being represented schematically by the arrow 7.

  Still with reference to FIG. 1 on which it can be seen schematically by line 16 that the ejection cone 8 is fixedly attached to a rear end of the crankcase 10, by means of fixing means which will be described below. , it is noted that the assembly 1 further comprises an annular structure 18 surrounding the cone 8 and also attached to the rear end of the crankcase 10. As is known to those skilled in the art, this annular structure 18 ( nozzle) defines a radially outer skin of the annular channel 12 of primary flow 14, and is also bathed externally by the secondary flow 20 escaping from the secondary annular channel 22. Thus, the primary flow 14 passes between the cone 8 and the structure 18 before being ejected from the engine assembly 1. Finally, it is specified that the attachment device shown in FIG. 1 corresponds only to the primary structure of this, the other components of this device 4 and known to those skilled in the art such as engine fasteners, secondary structures of the type aerodynamic fairings, etc., not shown. Referring now to Figure 2, we can see fixing means 30 for mounting the gas ejection cone 8 on the rear end of the engine casing 10. In this exploded view, it can be seen that the means of fastening 30 firstly comprise a first internal fastening flange 32 integral with the crankcase 10, and more precisely extending the rear end of the same housing 10 downstream. They also comprise a second internal fastening flange 34 secured to the cone 8 preferably made in one piece from its front end to its cone end located further downstream, this second internal fastening flange 34 also extending the cone 8 upstream. These two internal fastening flanges 32, 34 are located in the longitudinal extension of one another, and may for example be symmetrical with respect to one another in a transverse plane YZ. As regards the first flange 32, it has an upstream portion which is naturally annular, and provided inclined so as to approach the longitudinal axis 5 while going backwards. This upstream portion 36 carries a first circumferential projection 38 projecting radially outwards, as is clearly visible in Figure 2. Similarly, the second flange 34 has a downstream portion which is naturally annular, and provided inclined of to approach the longitudinal axis 5 while going forward. This downstream portion 40 carries a second circumferential projection 42 projecting radially outwardly. In addition, the upstream and downstream portions 36, 40 together form a V radially outwardly open, as is clearly visible in Figure 2. The first and second circumferential projections 38, 42 are in plane support against one another. the other, preferably so as to form an annular support located in a transverse plane YZ. Thus, it is the plating in the longitudinal direction X of a transverse and annular end surface 44 of the projection 38 against an annular and transverse end surface 46 of the projection 42 which allows a fixed holding of the cone 8 on the rear end of the housing 10. As an indication, it is noted that the internal fastening flange 32 may comprise an annular seat 48 serving as an internal radial support for the second fastening flange 34, and in particular for its circumferential protrusion 42. This seat 48 allows a centering of the two flanges, when they are positioned in the longitudinal extension of one another as it is performed during the implementation of the method of assembly of the motor assembly 1. In this respect, it is preferably arranged that the positioning of the ejection cone 8 in the extension of the rear end of the crankcase 10 is achieved until the veneer is obtained in the longitudinal direction. ale of the two bearing surfaces 44, 46 above. To maintain and especially strengthen the tightening of the two flanges 32, 34, the fastening means 30 further comprises an outer junction flange 50 also extending substantially all around the axis 5, and in particular around the two fastening flanges internal 32, 34. This outer junction flange 50 has a circumferential notch 52 open radially inwards, and preferably having a general V-shaped section thus also opening radially inwardly of the 1. Referring now to FIG. 3, it can be seen that the circular joining flange 50 is intended to surround the circular internal fastening flanges 32, 34, while ensuring aerodynamic continuity between the casing 10 and the casing 10. the cone 8. Thus, the junction flange 50 is effectively placed around the flanges 32, 34, so as to accommodate the circumferential notch 52 the two circumferentially extending projections. 38, 42 pressed against each other in the X direction. As indicated above, the two bearing surfaces 44, 46 of the circumferential projections respectively corresponding to the downstream surface of the first projection 38 and at the upstream surface of the second projection 42, are preferably oriented transversely, that is to say in a plane YZ. On the other hand, the two projections 38, 42 also have opposite surface 54, 56 inclined so as to cooperate with the general V-shaped section of the circumferential notch section 52. More specifically, the bearing surface 54 of the projection 38, corresponding to the upstream surface of the latter, is inclined so as to cooperate with the upstream leg of the aforementioned V, while the bearing surface 56 of the projection 42, corresponding to the downstream surface thereof, is inclined so as to cooperate with the downstream leg of this V.

  Therefore, it can be understood that when clamping in the radial direction of the joining flange 50 is used, this makes it possible to clamp in the longitudinal direction of the first projection 38 against the second projection 42. being of course all the more important that the radial depression of the projections 38, 44 in the notch 52 is high. To ensure this radial clamping of the junction flange 50, and simultaneously allow it to be held on the internal fastening flanges 32, 34, the fastening means 30 may then comprise one or more tightening straps 60 in contact with and around this flange. Thus, the strap 60 used may be of any type known to those skilled in the art, without departing from the scope of the invention. Preferably, it is a tightening strap located all around the joining flange 50 and having two free ends that can be connected. In general, it is equipped with one or more mechanisms for circumferentially clamping the strap, namely the tensioning thereof, the latter tightening then resulting in a radial clamping of the flange 50. Referring to FIGS. 4a and 4b show schematically the design of the external junction flange 50 implemented in the preferred embodiment. Thus, it can be seen that this flange 50 is made using a plurality of angular sectors 62, which, when this flange 50 is in a tight state around the internal fastening flanges, surrounds them on to approximately 360. More specifically, in the preferred embodiment, the junction flange 50 comprises three angular sectors each extending substantially over 120, one of these three sectors 62 carrying at its two ends respectively the two other sectors 62, by example articulated, but preferably with the aid of flexible links. Consequently, when the connecting flange 50 is put in place on the motor assembly 1, only the intermediate angular sector 62 fully matches the internal fixing flanges (not shown in FIGS. 4a and 4b), the other two sectors 62 being then separated from the internal fastening flanges because of the gravity. In addition, in this position prior to any clamping of the flange 50, the two free ends 64 of the two sectors 62 connected to the intermediate sector, are relatively distant from each other as shown schematically in Figure 4a. With this procedure, it is noted that the step of placing the outer junction flange so as to accommodate the first and second circumferential projections within the circumferential notch of this flange, is preferably performed. so that the cooperation between the notch and the protrusions is effected only on an angular portion smaller than 360, the totality of this cooperation then being obtained only during the clamping of the flange 50 by means of the strap 60. In this regard, it is indicated that the clamping strap 60 is disposed around the sectors 62, with its two ends carrying each of the parts of a clamping mechanism 66. Therefore, to start the tightening of the junction flange external 50 first aiming to bring the two sectors 62 of the longitudinal axis 5 of the turbojet, the two portions of the mechanism 66 are connected to each other, so that the circumferential clamping the strap 60 can be initiated. This first clamping portion can optionally be performed by hand, without tools, by an operator. The so-called pre-tightening operation intended to obtain a total cooperation between the circumferential projections and the circumferential notch of the flange 50 on substantially 360, can be carried out always by hand by the operator, without tools. It is completed when the two sector ends 64 come opposite one another (FIG. 4b), implying that the three angular sectors 62 are perfectly arranged around a circle centered on the axis 5, shown schematically in FIG. dashed in Figure 4a. Then, the circumferential clamping of the strap 60, also called tensioning, can be continued using a tool cooperating with the mechanism 66, in order to ensure a real clamping in the radial direction of the flange. This portion of the clamping is therefore intended to accentuate the penetration of the circumferential protrusions within the notch provided on the joining flange 50, so as to obtain the desired plating between the gas ejection cone and the rear end of the crankcase, in the X direction. Of course, various modifications can be made by those skilled in the art to the invention which has just been described, only by way of non-limiting example. In this respect, it is possible in particular to indicate which if the engine assembly 1 has been presented in a configuration adapted to be suspended under the wing of the aircraft, this assembly 1 could also be in a different configuration allowing it to be mounted above this same wing, or even on a rear part of the fuselage of this aircraft.

Claims (8)

  Engine assembly (1) for an aircraft comprising a motor (6) having a crankcase (10), this assembly also comprising a gas ejection cone (8) defining a radially inner skin of an annular channel ( 12), said ejection cone (8) being fixedly attached to a rear end of said motor casing (10) by means of fixing means (30), characterized in that said fixing means (30) comprise an outer junction flange (50) fixedly held around a first internal fastening flange (32) integral with the crankcase and a second inner fastening flange (34) integral with the throttle cone said outer junction flange (50) having a circumferential notch (52) open radially inwardly and receiving on the one hand a first circumferential projection (38) belonging to said first inner fastening flange and projecting radially towards the inside. exter and secondly a second circumferential projection (42) belonging to said second inner fastening flange and projecting radially outwardly, the first and second circumferential projections (38, 42) housed in said circumferential notch (52). ) being pressed against each other.   2. Engine assembly (1) according to claim 1, characterized in that said circumferential slot (52) has a generally V-shaped section open radially inwardly.   3. Motor assembly (1) according to claim 1 or claim 2, characterized in that said outer junction flange (50) is in the form of a plurality of angular sectors (62) distributed around a longitudinal axis (5) motor.   4. Engine assembly (1) according to any one of the preceding claims, characterized in that said gas ejection cone (8) is made in one piece.   The engine assembly (1) according to any one of the preceding claims, characterized in that said outer junction flange (50) is held securely around the first and second inner fastening flanges (32, 34) with the aid of at least one clamping strap (60) placed around this outer joining flange (50).   Motor unit (1) according to claim 5, characterized in that it is designed so that a powering of said at least one clamping strap (60) causes, via said connecting flange external (50), clamping in the longitudinal direction of the first projection (38) against the second projection (42).   7. Aircraft comprising at least one engine assembly (1) according to any one of the preceding claims, assembled on a wing or a rear fuselage of this aircraft.   8. A method of assembling an engine assembly according to any one of claims 1 to 6, characterized in that it comprises the following steps; positioning said gas ejection cone in the extension of the rear end of the crankcase - placing the outer junction flange to accommodate said first and second circumferential projections within said circumferential notch of said flange external junction; and clamping the outer junction flange around the first and second internal fastening flanges.