System for coupling two aircraft turbine engine parts, preferably two turbine engine shafts

Abstract

The invention relates to a system (20) for coupling two aircraft turbine engine parts (22, 24), the system comprising a nut (32) for clamping the two parts together, and an anti-rotation ring (38) that comprises: - a first rotational coupling member (44a) intended to co-operate with a first complementary rotational coupling member (44b) provided on the first part (22), so as to form a first rotational coupling device; - a second rotational coupling member (46a) intended to co-operate with a second complementary rotational coupling member (46b) provided on the nut (32), so as to form a second rotational coupling device. The coupling system is configured such that the ring (38) can be placed in a provisional axial position relative to the nut and then be moved into a final coupling axial position.

Description

[0001] DESCRIPTION

[0002] TITLE: COUPLING SYSTEM FOR TWO AIRCRAFT TURBOMACHINE PARTS, PREFERABLY TWO TURBOMACHINE SHAFTS

[0003] TECHNICAL FIELD

[0004] The invention relates to the field of systems for coupling two parts of an aircraft turbomachine, such as for example a turbojet or a turboprop.

[0005] Preferably, the invention relates to a system for coupling two shafts of the aircraft turbomachine, for example a compressor shaft and a turbine shaft, but it is not limited to this preferred application.

[0006] Another application of the invention lies, for example, in the coupling of a bearing to a turbomachine shaft.

[0007] STATE OF THE PRIOR ART

[0008] Aircraft turbomachine parts coupling systems have been widely developed in the prior art. An example of a coupling system is disclosed in document FR 2 858 249 A1.

[0009] In certain turbomachine architectures, such a coupling system may comprise a nut for tightening the two parts, the nut then being provided with a thread cooperating with another thread made on one of the two parts to be coupled. The coupling system further comprises an anti-rotation ring cooperating with the nut, this ring being intended to limit / prevent the rotation of this nut relative to the aforementioned part.

[0010] The assembly process of such a system generally requires tightening the nut until a minimum tightening is obtained, to achieve the coupling between the two parts. Then, an additional tightening of the nut is carried out, called over-torque, solely for the purpose of matching the different means allowing the anti-rotation function of the nut.

[0011] Usually, the means enabling the anti-rotation function include on the shaft either notches involving significant over-torques to be applied during assembly, or particularly expensive splines.

[0012] Previous designs of this type can be problematic, firstly because the over-torque applied to the nut introduces undesirable mechanical stresses within the assembly. To limit these stresses, it is possible to increase the pitch / fineness of the anti-rotation means, such as the aforementioned splines, but this strategy inevitably leads to additional manufacturing costs.

[0013] Additionally, prior art may have designs that require visual access for coupling system assembly, but such visual access is not always possible within the dense environment of a turbomachine.

[0014] There therefore remains a need to improve the design of prior art coupling systems.

[0015] STATEMENT OF THE INVENTION

[0016] To meet the need mentioned above, the invention firstly relates to a system for coupling two parts of an aircraft turbomachine, according to the characteristics of claim 1.

[0017] Thanks to this design, the possible over-torque to be applied to the nut during assembly remains advantageously moderate, so that the assembly proves to be less mechanically constrained, without however requiring an increase in the pitch / fineness of the anti-rotation means, such as grooves and / or finger-notch assemblies.

[0018] Furthermore, the design of the invention is also advantageous in that it allows blind mounting of the coupling system, i.e. without visual access to the area of ​​the turbomachine in which the mounting is carried out. This situation occurs in particular when coupling large diameter parts, such as turbomachine shafts, and the invention is thus particularly suitable for this application.

[0019] The invention preferably comprises at least any one of the following optional features, taken alone or in combination.

[0020] Preferably, the first rotational coupling device comprises, and is preferably made up of, one or more finger-notch assemblies, the number of these assemblies being preferably less than six, and even more preferably less than four. The reduced number of these finger-notch assemblies, for stopping the rotation of the first turbomachine part via the ring, greatly reduces manufacturing costs, in particular compared to a splined solution, which can nevertheless be considered.

[0021] Preferably, the second rotational coupling device is formed by splines, to stop the nut from rotating, via the ring. Such splines remain less expensive to produce on these elements than on the parts to be coupled, such as turbomachine shafts.

[0022] In this embodiment, it is therefore the finger-notch assemblies forming the first coupling device which are first engaged, then it is the splines forming the second coupling device which are engaged after having been matched. The pitch of the splines being smaller than that of the notches, the rotation of the nut to be applied to allow the desired match, and the possible excess torque which results therefrom, advantageously remain low.

[0023] Preferably, in the temporary axial position of the ring, said first coupling member and said first complementary coupling member are intended to provide between them a circumferential clearance allowing, by consumption of this clearance, sufficient angular movement of the ring to allow said second coupling member to be placed in correspondence, in the circumferential direction, with said second complementary coupling member, this correspondence allowing the axial displacement of the anti-rotation ring from its temporary axial position to its final axial coupling position. In this solution, it is actually the consumption of the aforementioned clearance which allows, where appropriate, the second coupling member(s) to be placed in correspondence with the second complementary coupling member(s). Consequently, advantageously, no over-torque is required on the nut for finalizing the assembly of the coupling system.

[0024] It is noted that another solution without backlash could be to apply a moderate over-torque to the nut, to finalize the assembly. A hybrid solution is also possible, in which the finalization of the assembly of the coupling system may require the consumption of the backlash, and the application of an over-torque to the nut, of even more moderate intensity.

[0025] Preferably, the coupling system comprises elastic return means arranged between the nut and the anti-rotation ring, so as to force the latter axially towards its final axial coupling position. This design proves particularly suitable in the absence of visual access to the mounting area. It automatically generates the axial movements required for the anti-rotation ring. These elastic return means also preferably make it possible to maintain the anti-rotation ring in the final mounting position, even if other means can be adopted to fulfill this latter function, without departing from the scope of the invention.

[0026] Preferably, said first coupling member and said first complementary coupling member have inclined circumferential abutment surfaces, forming an angle with respect to the axial direction. With this design, it is possible to have a circumferential clearance between the first coupling member and the first complementary coupling member, in the intermediate axial position of the ring. Then, once the matching has been carried out for the second coupling member and the second complementary coupling member, for example by partial consumption of this circumferential clearance, the ring can be moved axially by the elastic return means, to its final coupling position in which the inclined circumferential abutment surfaces are in contact two by two.

[0027] Preferably, the nut and the anti-rotation ring are concentric, the anti-rotation ring being inserted inside the nut. The invention also relates to an assembly for an aircraft turbomachine comprising two parts, as well as a system as described above, coupling the two parts which are preferably two turbomachine shafts. Other applications can nevertheless be envisaged, without departing from the scope of the invention.

[0028] The invention also relates to an aircraft turbomachine comprising at least one such assembly. It may, for example, be a turbojet or a turboprop.

[0029] Finally, the invention also relates to a method for mounting a coupling system as described above, on two aircraft turbomachine parts to be coupled, comprising the following steps:

[0030] - tightening the nut on the first part, via the threads of the nut and the first part, so as to axially press the first part against the second part;

[0031] - bringing the anti-rotation ring into its temporary axial position relative to the nut, so as to place the first rotating coupling device in its coupling configuration, while keeping the second rotating coupling device in its non-coupling configuration;

[0032] - the movement of the anti-rotation ring relative to the nut, from its temporary axial position to its final axial coupling position after rotation of the ring relative to the nut, so as to bring the second coupling device into rotation in its coupling configuration, while maintaining the first coupling system in rotation in its coupling configuration.

[0033] Other advantages and characteristics of the invention will appear in the detailed non-limiting description below.

[0034] BRIEF DESCRIPTION OF THE DRAWINGS

[0035] [Fig. 1] is a longitudinal sectional view of a turbojet engine;

[0036] [Fig. 2] is a longitudinal half-sectional view of a two-piece coupling system of the turbojet shown in the preceding figure;

[0037] [Fig. 3] is a cross-sectional view of the coupling system shown in Fig. 2, and corresponding to the section taken along line III-III of Fig. 2; [Fig. 4] is a partial perspective view of a tightening nut of the coupling system shown in Figs. 2 and 3;

[0038] [Fig. 5] is a partial perspective view of an anti-rotation ring of the coupling system shown in Figures 2 and 3;

[0039] [Fig. 6] is a partial perspective view of an anti-rotation ring, according to an alternative;

[0040] [Fig. 7] is a partial perspective view of one end of a shaft of the turbomachine, intended to be coupled by the coupling system shown in Figures 2 and 3;

[0041] [Fig. 8] is a partial perspective view of the coupling system shown in Figures 2 and 3;

[0042] [Fig. 9]

[0043] [Fig. 10]

[0044] [Fig. 12] are longitudinal half-sectional views of the coupling system shown in Figure 2, in different successive states during a process of assembling this coupling system;

[0045] [Fig. 11] is a cross-sectional view of the coupling system shown in Fig. 10, and corresponding to the section taken along line XI-XI of Fig. 10;

[0046] [Fig. 13]

[0047] [Fig. 14] are cross-sectional views of the coupling system shown in the preceding figures, according to an alternative, and in different successive states during the process of assembling this coupling system;

[0048] [Fig. 15] is a longitudinal half-sectional view of the coupling system similar to that shown in the preceding figures, and presented in the form of an alternative;

[0049] [Fig. 16]

[0050] [Fig. 17]

[0051] [Fig. 18]

[0052] [Fig. 19] are partial sectional views of the coupling system according to yet another alternative, in different successive states during the assembly process of this coupling system; [Fig. 20] is a partial perspective view of a system for locking a plug in a part of the turbojet, this locking system being integrated into the coupling system shown in the preceding figures;

[0053] [Fig. 21] is an axial view of the plug shown in the preceding figure;

[0054] [Fig. 22]

[0055] [Fig. 23]

[0056] [Fig. 24] are partial perspective views of the locking system shown in Figure 20, in different successive states during a process of mounting this locking system;

[0057] [Fig. 25] is a partial sectional view of the locking system, in its condition as shown in Fig. 23;

[0058] [Fig. 26] is a partial sectional view of the locking system, in its condition as shown in Fig. 24;

[0059] [Fig. 27] is a partial sectional view of the locking system, in its state at the end of the assembly process of this system.

[0060] DETAILED DESCRIPTION OF THE INVENTION

[0061] Referring firstly to Figure 1, there is shown an aircraft turbomachine 1, according to a preferred embodiment of the invention. This is a double-flow, double-spool turbojet engine. However, it could be a turbomachine of another type, for example a turboprop, without departing from the scope of the invention.

[0062] The turbomachine 1 has an axis X around which its various components extend, this axis being called the longitudinal axis of the turbomachine. It comprises, from upstream to downstream along a main direction 5 of flow of the gases through this turbomachine, a fan 3, a low-pressure compressor 4, a high-pressure compressor 6, a combustion chamber 11, a high-pressure turbine 7 and a low-pressure turbine 8. Conventionally, after passing through the fan, the air divides into a central primary flow 12a and a secondary flow 12b which surrounds the primary flow. The primary flow 12a flows in a main gas circulation vein 14a passing through the compressors 4, 6, the combustion chamber 11 and the turbines 7, 8. The secondary flow 12b flows in a secondary vein 14b delimited radially towards the outside by a motor casing, surrounded by a nacelle 9.

[0063] Figures 2 to 8 represent a system 20 for coupling two rotating parts of the turbojet 1, having the same axis of rotation X. This involves a first shaft 22 corresponding to a shaft of the low pressure turbine, and a second shaft 24 corresponding to a shaft of the low pressure compressor. These two shafts 22, 24 are hollow, and the upstream end of the first shaft 22 is inserted into the downstream end of the second shaft 24, so as to be coupled in translation and in rotation in the axial direction, via the system 20. The two shafts 22, 24, concentric and centered on the X axis, form with their coupling system 20 an assembly 30. Several assemblies of this type can be provided within the turbojet engine, with coupled parts which can indifferently belong to various modules of the turbojet engine, including the fan, the compressors, the combustion chamber, or even the turbines.

[0064] Here, preference is given to coupling parts with large diameters, and for which visual access to the coupling zone is limited, or even non-existent. This is particularly the case for the architecture shown partially in Figure 2, showing the system 20 in a mounted state, in which the two shafts 22, 24 are coupled.

[0065] The coupling system 20 firstly comprises a nut 32 for tightening the two shafts, this nut being centred on the axis X and provided with a first thread 34a, or nut thread, cooperating with a second thread 34b, or first part thread, made on an external surface of the first shaft 22. As can be seen in FIGS. 2 and 8, in the mounted state of the coupling system 20, the downstream end of the nut 32 exerts an axial force on the second shaft 24, and more precisely on an internal shoulder of the latter. This axial force pushes the second shaft 34 downstream against an external shoulder of the first shaft 22, with an axial shim 36 possibly interposed between the two shoulders, as has been shown by way of example in FIG. 2. The axial tightening intensity of the nut is sufficient to generate the desired coupling between the two shafts 22, 24.The system 20 also comprises an anti-rotation ring 38 intended to limit / prevent the rotation of the nut 32, relative to the first shaft 22, in the mounted state of the system 20.

[0066] The anti-rotation ring 38 is centered on the axis X, being arranged at least partly internally in the nut 32, and being capable of being moved axially relative to the latter, in different axial positions. In Figures 2 and 8, the anti-rotation ring 38 adopts its most downstream position relative to the nut 32, corresponding to a final coupling position of the shafts. It is held there by a snap ring 40 or a similar retaining element, carried by the ring 38 and cooperating with a groove 42a opposite, made on the internal surface of the nut 32 upstream of the first thread 34a.

[0067] In the final coupling position of the ring 38, the latter is thus retained axially relative to the nut 32, thanks to the snap ring 40, or any other translational stop system associated with the ring. In this position, a first rotational coupling device is provided, as well as a second rotational coupling device, both in active coupling configuration.

[0068] The first rotational coupling device is constituted by first rotational coupling members 44a produced on the downstream end of the ring 38, and by first complementary rotational coupling members 44b, provided on the upstream end of the first shaft 22. Here, these are preferably finger-notch assemblies, the fingers 44a being preferably provided on the ring 38, and the notches 44b on the first shaft 22, even if an inverse solution can be envisaged. The notches 44b are also called first notches 44b.

[0069] The number of these finger-notch assemblies is preferably less than four, for example three, or two as in the figures. In this case, the two fingers 44a are preferably diametrically opposed, as are their corresponding notches 44b on the upstream end of the first shaft 22, these notches opening axially upstream.

[0070] The fingers 44a, provided at the downstream end of the ring 38, project axially downstream and radially inward as shown in Figures 2, 5 and 8, or they project only axially downstream, as shown in the alternative of Figure 6. The second rotational coupling device is constituted by second rotational coupling members 46a produced on the external surface of the ring 38, and by second complementary rotational coupling members 46b, provided on the internal surface of the nut 32. Here, these are preferably grooves 46a, 46b cooperating with each other, in the form of two concentric annular rows of grooves. Each annular row of grooves 46a, 46b may be uninterrupted over 360°, or extend only over an angular sector less than 360°, or extend over several angular sectors spaced circumferentially from each other.The number of grooves per annular row is high, for example greater than twenty, thirty or forty. The number of grooves is preferably the same for each of the two annular rows of grooves, and this number is strictly greater than that of the number of notches and the number of fingers.

[0071] Each spline extends radially, in the conventional form of a tooth, and more precisely radially outwards for splines 46a, and radially inwards for splines 46b.

[0072] One of the particularities lies in the fact that the first grooves 46a are axially spaced from the fingers 44a, towards the upstream. Indeed, there is preferably no axial overlap zone between these elements 46a, 44a.

[0073] Figures 9 to 12 illustrate the method of mounting the coupling system 20 on the two shafts 22, 24.

[0074] First, the system 20 is put in place on the first shaft 22, so that the nut 32 surrounds the upstream end of this shaft, then this nut 32 is tightened via the first and second threads 34a, 34b. The objective of this tightening is to axially press the first shaft 22 against the second shaft 24, by pressing the downstream end of the nut against the second shaft 24. The tightening torque applied to the nut 32 corresponds to a minimum torque to ensure the desired coupling of the two shafts. This step is shown diagrammatically in FIG. 9. During this step, the ring 38 is held in an inactive upstream position, called the non-coupling position, where it is retained axially relative to the nut 32 via the snap ring 40 which cooperates with another groove 42b on the internal surface of the nut, arranged upstream of the groove 42a. The next step is illustrated in Figures 10 and 11.It consists of rotating the ring 38 along the X axis relative to the fixed nut 32, as well as translating it downstream. The rotation of the ring serves to align the fingers 44a with the notches 44b, after which an axial introduction of the fingers can be carried out in these same notches. This axial displacement of the ring in fact leads to bringing the anti-rotation ring 38 into a temporary axial position relative to the nut, thus placing the first rotational coupling device 44a, 44b in its coupling configuration. However, the axial displacement of the ring 38 is normally stopped by the lack of correspondence between the splines 46a, 46b, as shown in Figure 11 in which it is shown that the first splines 46a are not aligned with inter-spline spaces on the other row of second splines 46b, and vice versa.Therefore, in the temporary axial position of the ring 38, the second rotational coupling device 46a, 46b remains in a non-coupling configuration.

[0075] During this step, the rotation and translation force on the ring 38 can be exerted simultaneously, in particular when these actions take place blindly in the turbojet mounting area.

[0076] To achieve the desired correspondence between the splines 46a, 46b, shown in particular in FIG. 3, the nut 32 is tightened again on the second shaft 22. An overtorque is thus applied to the nut, of a measured intensity, until the desired correspondence between the splines 46a, 46b is obtained. This step of applying an overtorque to the nut 32 is shown diagrammatically in FIG. 12.

[0077] The pitch of the splines being smaller than that of the notches, the rotation of the nut to be applied to allow the desired correspondence between these splines, and the resulting overtorque, remain advantageously low.

[0078] Then, a new axial displacement of the ring 38 relative to the nut 32 is carried out, from its temporary axial position to its final axial coupling position, so as to make the splines 46a, 46b cooperate together as shown in FIG. 2. Here also, it is noted that the rotation of the nut 32 and the application of the translational force on the ring 38 can be exerted simultaneously, in particular when these actions take place blindly in the mounting zone of the turbojet.

[0079] At the end of this step, the second rotational coupling device 46a, 46b is in its coupling configuration, due to the cooperation between the splines. Similarly, the first rotational coupling system 44a, 44b remains in its coupling configuration, after its fingers 44a have been further inserted into their respective notches 44b, following the additional axial displacement of the ring 38 relative to the nut 32.

[0080] During this additional movement of the ring 38, the snap ring 40 is inserted into the groove 42a of the ring, thus ensuring its locking in translation. This makes it possible to maintain the entire system 20 in a mounted state, ensuring the coupling in translation and in rotation of the two shafts 22, 24, without risk of loosening the nut 32.

[0081] Figures 13 and 14 represent an alternative, the design of which advantageously does not require the application of an over-torque on the nut, for finalizing the assembly of the coupling system 20.

[0082] This alternative has many technical characteristics in common with the embodiment shown in Figures 2 to 12, and moreover, in the figures, the elements which bear the same numerical references correspond to identical or similar elements.

[0083] In the alternative of figures 13 and 14, it is shown the existence, in the provisional axial position of the ring 38, of a circumferential clearance 48 between each finger 44a and its corresponding notch 44b. This arrangement allows, by partial or total consumption of the clearance 48, sufficient angular movement of the ring 38 relative to the nut 32 remaining fixed, to allow the splines 46a, 46b to be placed in correspondence, still in the circumferential direction. After such an operation, the coupling system 20 adopts a state such as shown in figure 14. In this respect, it is noted that the circumferential direction, which extends around the axis X, also corresponds to the tangential direction. As indicated previously, the desired correspondence between the grooves 46a, 46b allows the axial displacement of the anti-rotation ring 38, from its temporary axial position to its final axial coupling position.

[0084] It is noted that a hybrid solution is also possible, in which the matching of the splines 46a, 46b is obtained on the one hand by rotating the ring 38 while consuming the aforementioned clearance 48, and on the other hand by applying a slight over-torque to the nut 32.

[0085] Another alternative is shown in Figure 15, which provides elastic return means, such as one or more springs 50 arranged axially between the nut 32 and the anti-rotation ring 38. The spring 50 makes it possible to force the ring 38 axially downstream relative to the nut 32, and it is therefore capable of generating the axial forces required for the passage of the ring 38 from its most upstream position to its provisional axial position, then from this provisional axial position to its final axial coupling position.

[0086] This principle also makes it possible to maintain the ring 38 in its final axial coupling position, so that the snap ring stop means are no longer necessarily required.

[0087] Figures 16 to 19 represent different states of the coupling system 20 according to yet another alternative, in which each finger 44a and its corresponding notch 44b have inclined circumferential abutment surfaces, forming an angle with respect to the axial direction. In other words, each of these two surfaces 52a, 52b forms an angle of non-zero value with the axial direction, parallel to the X axis.

[0088] The inclined circumferential abutment surfaces 52a, 52b are shown in Figure 16. They are parallel or substantially parallel, and respectively constituted by a lateral flank of the finger 44a, and by a lateral flank 68 of the notch 44b. The inclination of the circumferential abutment surface 52b of the notch 44b is such that it widens circumferentially when going axially upstream. Conversely, the inclination of the circumferential abutment surface 52a of the finger 44a is such that it narrows circumferentially when going axially downstream.

[0089] The position of Figure 16 corresponds to that of Figure 9, in which the finger 44a is not yet in correspondence with its associated notch 44b. When such a correspondence is reached following the rotation of the ring 38, under the effect of the operator or the spring 50, the finger 44a is partially introduced into the notch 44b, as has been shown diagrammatically in Figure 17. The axial introduction is stopped by the stop between the splines. The circumferential clearance 48 observed between the inclined circumferential stop surfaces 52a, 52b can then be consumed, partially or completely by rotation of the ring 38, in order to bring these same splines (not shown in Figures 16 to 19) into correspondence. This step is shown diagrammatically in Figure 18. Then, when the correspondence between the splines is obtained, the ring 38 is moved axially to its final axial coupling position, under the effect of the spring 50.This position is reached when the circumferential abutment surfaces 52a, 52b come into contact with each other as shown in Figure 19, this contact being preferentially surface-based.

[0090] Due to the inclination of the contacting surfaces 52a, 52b, the finger 44a in abutment, on the lateral flank of the notch 44b, exerts on the shaft 22 an inclined force with a circumferential component. This component has a direction such that the finger 44a forces the second shaft 22 in a direction of rotation causing the nut 38 to tighten more tightly on this shaft 22.

[0091] Figure 20 shows the assembly 30 comprising the coupling system 20 of the two shafts 22, 24, but also a system 120 for locking a plug 60 in the first shaft 22. Indeed, the plug 60 is mounted at the upstream end of the first shaft 22, at the level of the first rotational coupling device 44a, 44b, or close to the latter. This plug 60 serves to close, towards the upstream, the hollow space 66 inside the shaft 22, centered on the axis X. This plug 60 may be required to support significant loads, in particular pressure loads, which the locking system 120 must be able to withstand.

[0092] In the embodiment of Figure 20, the locking system 120 of the cap as well as the coupling system 20 of the two shafts are thus combined within the assembly 30, and they share parts in common in order to present a compact overall design, of lower mass, and of reduced cost. Still with reference to Figure 20, the locking system 120 comprises the anti-rotation ring 38, which therefore fulfills here the additional function of locking the cap 60. Consequently, in the remainder of the description, this ring 38 will therefore be called the locking ring.

[0093] The locking ring 38 is, as mentioned previously, equipped with projecting elements formed by the fingers 44a. In a locking position of the ring 38, corresponding to its final axial coupling position described previously, the fingers 44a are inserted respectively into first recesses of the shaft 22, corresponding to the first notches 44b. Other shapes could nevertheless be adopted for the projecting elements 44a and the first recesses 44b, without departing from the scope of the invention. One of the particularities here lies in the fact that the plug 60 comprises one or more holding fingers 62, their number preferably being identical to that of the first notches 44b, as well as their arrangement. These are thus two holding fingers 62 which are provided on a plug body 64, in a diametrically opposed manner.In this regard, it is noted that the body 64 of the plug has an outside diameter substantially equal to an inside diameter of the hollow 66 of the shaft 22, only a small mounting clearance being preferentially retained. In addition, the holding fingers 62 project radially outwards from this plug body 64.

[0094] Each of the holding fingers 62 is inserted into a second recess of the shaft 22, this second recess taking the form of a second notch 144b opening circumferentially into one of the first notches 44b. Each second notch 144b may be of a dimension much smaller than that of the first notch 44b into which it opens, for example taking the form of a simple notch in the circumferential direction.

[0095] More specifically, each second circumferential notch 144b is made in one of the two lateral flanks 68 of the first notch 44b into which it opens. In the preferred embodiment shown in FIG. 20, each second circumferential notch 144b (only one of the two notches 144b being visible in FIG. 20) is made at the axial bottom of its associated first notch 44b. Thus, in the locking position of the ring 38 on the upstream end of the first shaft 22, each finger 44a circumferentially covers, at least in part, one of the second notches 144b housing a finger 62 for holding the cap. More specifically, each finger 44a covers, in the circumferential direction, the bottom of one of the second notches 144b housing a holding finger 62.

[0096] Thanks to this overlap, each finger 44a therefore follows a second notch 144b in the circumferential direction, without these two elements necessarily being in contact with each other. In the event of circumferential play, the latter preferably remains sufficiently small to prevent the total extraction of the holding finger 62 from the second notch 144b.

[0097] Figure 21 shows an axial view of the plug 60, the mounting method of which will now be described with reference to Figures 22 to 27.

[0098] First of all, as visible in figures 22, 23 and 25, a step of axial introduction of the plug 60 into the hollow 66 of the first shaft 22 is carried out, so that each holding finger 62 of the plug is inserted axially downstream into its first associated notch 44b of the shaft 22, until it reaches the axial bottom of this notch 44b. Then, the plug 60 is rotated along the axis X on which it is centered, so as to make each holding finger 62 penetrate into its second associated notch 144b. The extent of the rotation can remain measured, in correlation with the shallow depth of the second notch 144b. Figures 24 and 26 show the system 120 after this step has been carried out.

[0099] Finally, Figure T1 illustrates the last step, corresponding to the axial displacement of the locking ring 38 into its locking position. This leads to introducing each finger 44a into its first associated notch 44b of the shaft 22, until the finger 44a circumferentially covers, at least in part, the second notch 144b housing the holding finger 62.

[0100] Of course, various modifications may be made by those skilled in the art to the invention which has just been described, solely by way of non-limiting examples, and the scope of which is defined by the appended claims. In particular, the technical characteristics of the different embodiments and their alternatives are interchangeable and combinable.

Claims

CLAIMS 1. System (20) for coupling two parts (22, 24) of an aircraft turbomachine, comprising a nut (32) for tightening the two parts (22, 24), the nut (32) being provided with a nut thread (34a) intended to cooperate with a first part thread (34b) made on a first (22) of the two parts (22, 24), as well as an anti-rotation ring (38) intended to limit / prevent the rotation of the nut (32) relative to the first part (22), characterized in that the anti-rotation ring (38) comprises: - a first rotational coupling member (44a) intended to cooperate with a first complementary rotational coupling member (44b) provided on the first part (22), so as to form a first rotational coupling device; - a second rotational coupling member (46a) intended to cooperate with a second complementary rotational coupling member (46b) provided on the nut (32), so as to form a second rotational coupling device; the coupling system being configured so that the anti-rotation ring (38): - can be placed in a temporary axial position relative to the nut (32), in which position the first rotational coupling device (44a, 44b) is in a coupling configuration, while maintaining the second rotational coupling device (46a, 46b) in a non-coupling configuration; - can be moved relative to the nut (32), from its temporary axial position to a final axial coupling position after rotation of the anti-rotation ring (38) relative to the nut (32), position in which the second rotational coupling device (46a, 46b) is in a coupling configuration, while maintaining the first rotational coupling device (44a, 44b) in its coupling configuration.

2. System according to claim 1, characterized in that the first rotational coupling device (44a, 44b) comprises one or more finger-joints. notch, the number of these assemblies being preferably less than six, and even more preferably less than four.

3. System according to claim 1 or 2, characterized in that the second rotational coupling device (46a, 46b) is formed by grooves.

4. System according to any one of the preceding claims, characterized in that in the temporary axial position of the anti-rotation ring (38), the first coupling member (44a) and the first complementary coupling member (44b) are intended to provide between them a circumferential clearance (48) allowing, by consumption of this clearance, sufficient angular movement of the anti-rotation ring (38) to allow the second coupling member (46a) to be placed in correspondence, in the circumferential direction, with the second complementary coupling member (46b), this correspondence allowing the axial displacement of the anti-rotation ring (38) from its temporary axial position to its final axial coupling position.

5. System according to any one of the preceding claims, characterized in that it comprises elastic return means (50) arranged between the nut (32) and the anti-rotation ring (38), so as to force the latter axially towards its final axial coupling position.

6. System according to any one of the preceding claims, characterized in that the first coupling member (44a) and the first complementary coupling member (44b) have inclined circumferential abutment surfaces (52a, 52b), forming an angle relative to the axial direction.

7. System according to any one of the preceding claims, characterized in that the nut (32) and the anti-rotation ring (38) are concentric, the anti-rotation ring (38) being inserted inside the nut (32).

8. Assembly (30) for an aircraft turbomachine comprising two parts (22, 24), as well as a system (20) according to any one of the preceding claims, coupling the two parts (22, 24) which are two turbomachine shafts.

9. Aircraft turbomachine (1) comprising at least one assembly (30) according to claim 8.

10. Method for mounting a coupling system (20) according to any one of claims 1 to 7, on two parts (22, 24) of an aircraft turbomachine to be coupled, comprising the following steps: - tightening the nut (32) on the first part (22), via the nut and first part threads (34a, 34b), so as to axially press the first part (22) against the second part (24); - bringing the anti-rotation ring (38) into its temporary axial position relative to the nut (32), so as to place the first rotational coupling device (44a, 44b) in its coupling configuration, while keeping the second rotational coupling device (46a, 46b) in its non-coupling configuration; - moving the anti-rotation ring (38) relative to the nut (32), from its temporary axial position to its final axial coupling position after rotating the anti-rotation ring (38) relative to the nut (32), so as to bring the second rotational coupling device (46a, 46b) into its coupling configuration, while keeping the first rotational coupling device (44a, 44b) in its coupling configuration.

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