MODULARITY OF AN AIRCRAFT TURBOMACH ENGINE

Description

Technical field of the invention

[0001] The present invention relates to solutions for facilitating the modularity of an aircraft turbomachine. Technical background

[0002] The state of the art includes in particular document WO-A1-2015 / 075345, US-A1-3,631,688, FR-A1-2 975 149, US-A-3,958,887 and US-A-3,469,868.

[0003] An aircraft turbomachine is often produced as an assembly of modules, each of which may include fixed and moving parts. A module is defined as a subassembly of an engine that has geometric characteristics at its interfaces with adjacent modules that are sufficiently precise for it to be delivered individually, and which has undergone separate balancing when it includes rotating parts. The assembly of the modules makes it possible to form a complete engine, minimizing the balancing and matching operations of the interfacing parts.

[0004] The modularity of a turbomachine is a key element for its maintenance. Indeed, during an intervention, the parts must be easily accessible without having to dismantle a large number of parts of the engine. In practice, we try to obtain a division into a few major modules. For example, for a turbomachine with an upstream fan (the terms "upstream" and "downstream" are assessed in relation to the flow of gases in the turbomachine), we seek a division into three modules: a first major module for the front part including the fan and the LP compressor, a second major module for the part including the HP body and a third major module for the rear part of the engine including the LP turbine and the LP shaft. We thus understand that the LP body is divided into two modules.

[0005] The two BP body modules are fixed to each other by a nut which extends around the axis of the turbomachine and which serves to axially tighten the fan shaft on the BP shaft.

[0006] During a maintenance operation, this nut must be unscrewed using a tool which is inserted into the turbomachine along its longitudinal axis, and therefore inside the LP shaft and / or the fan shaft.

[0007] This maintenance is particularly difficult on a turbomachine with a gearbox in the front or upstream section. The problem in this case is accessibility to the nut. The gearbox is located upstream of the nut and must be partially disassembled to access the nut. Furthermore, access to the nut must be achieved with complex tools that present risks of mishandling and damage to the engine.

[0008] In this case, the modularity of the first major module is lost. In addition, the second major module and the third major module must be separated independently.

[0009] The modularity of the first module is, however, important when this module includes a reducer. Indeed, the reducer is housed in a lubrication enclosure which should preferably remain closed during a maintenance operation to avoid any oil leakage. To avoid dismantling this enclosure, there is a tendency to increase the internal diameter of the reducer so that it is greater than the diameter of the nut and thus allow the nut to be dismantled from the inside of the reducer. This solution is, however, penalizing for the size of the reducer and the general performance of the turbomachine.

[0010] In order to improve their propulsive efficiency, turbomachines tend towards increasing bypass ratios, which generally results in an increase in the size of the fan (diameter and axial dimension). This makes access to the LP shaft nut even more complex due to the lengthening of the tool required to access it.

[0011] Furthermore, some turbomachines, such as single-fan unducted turbomachines (also called USF, acronym for the English Unducted Single Fan), have a particularly long length and the HP and BP body modules have very small internal diameters, which complicates or even makes access to the nut by the tool impossible.

[0012] The present invention provides a solution to at least some of the problems discussed above that simplifies the modularity of an aircraft turbomachine. Summary of the invention

[0013] An example concerns a set of shafts for an aircraft turbomachine, this set comprising: a first shaft comprising external splines oriented parallel to an axis of rotation of the shaft, a second shaft comprising internal splines complementary to said external splines, this second shaft being axially engaged on the first shaft and these shafts being integral in rotation by engagement of their splines, and a system for axially locking the shafts with respect to each other, characterized in that said system comprises screws which are oriented radially relative to said axis, each of these screws being screwed into a first orifice of one of the shafts and comprising a free end capable of being engaged in a second orifice of the other of the shafts, each of these screws being movable by screwing from a first radial position in which its free end is engaged in said second orifice and ensures axial locking of the shafts, and a second radial position in which its free end is disengaged from said second orifice and ensures axial unlocking of the shafts.

[0014] The shaft assembly is particularly suitable for facilitating the modularity of an aircraft turbomachine, and can for example be used in the interface between two modules of an aircraft and more particularly in the interface between two shafts of these modules.

[0015] The coupling between the two shafts is achieved by splines. The splines extend parallel to each other and are engaged in each other by simple axial translation of the first shaft into the second shaft.

[0016] There are two types of spline coupling, the first being a coupling in which the splines are free to slide axially within each other. A first disadvantage of this coupling is that the splines must be lubricated and it is therefore necessary to provide an oil nozzle nearby. In the case of a turbomachine with a reduction gear, the splines could be housed in the reduction gear enclosure for lubrication purposes, but disengagement of the splines during a maintenance operation would cause the enclosure to open.

[0017] The second type of spline coupling is a coupling in which the splines are axially locked within each other and it is this technology that is used in the example.

[0018] The advantage is that the splines do not need to be lubricated. However, a system for axially locking the shafts and therefore the splines within each other must be provided.

[0019] In the example, this locking is ensured by radial screws. In other words, the shaft locking screws do not extend parallel to the axis but radially relative to this axis. The screws can be regularly distributed around the axis and their number is adapted in particular according to the diameters of the shafts and the maximum torque to be transmitted between these shafts.

[0020] The assembly according to the example may comprise one or more of the following features, taken in isolation from each other or in combination with each other: the first position is a radially external position, and the second position is a radially internal position; each of the screws comprises a radially internal end carrying a bearing head, and a free radially external end comprising a hollow imprint configured to receive a tool for screwing / unscrewing the screw; a ring is fixed in each of said second orifices and comprises an internal bore which has a frustoconical portion configured to cooperate with said free end of the screw for the purpose of centering the latter in said second orifice; the advantage of providing a centering ring in each second orifice is that this ring can be replaced in the event of wear while limiting the impact on the shaft; each ring is crimped in the corresponding second orifice; a sleeve is mounted in each of said first orifices and comprises an internal thread for screwing the corresponding screw;the advantage of providing a threaded sleeve in each first orifice is that this sleeve can be replaced in the event of wear while limiting the impact on the shaft; each sleeve comprises an external annular collar for bearing on the corresponding shaft; a retaining ferrule is mounted inside the first shaft and comprises a first cylindrical rim which extends at least partly opposite said first and second orifices and which is configured to radially retain the screws when they are in their respective second positions; the collar of each sleeve is interposed radially between the shaft and a second cylindrical rim of the ferrule; and the ferrule comprises an external cylindrical centering surface configured to cooperate with an internal cylindrical surface of the first shaft, this internal cylindrical surface comprising an annular groove for mounting an annular ring for axially retaining the ferrule with respect to the first shaft. ;

[0021] An aircraft turbomachine may comprise at least one assembly as described above.

[0022] Advantageously, said assembly is surrounded by at least one stator casing which comprises at least one radial orifice configured to allow the passage of a tool for screwing / unscrewing said screws.

[0023] According to a first other aspect, the invention relates to an aircraft turbomachine, according to claim 1, this turbomachine having a longitudinal axis and comprising: a high pressure body called HP comprising an HP shaft connecting an HP compressor rotor to an HP turbine rotor, this HP shaft extending along said axis, a low pressure body called BP comprising an BP shaft connecting an BP compressor rotor to an BP turbine rotor, this BP shaft extending along said axis and inside the HP shaft, a fan connected to a fan shaft, and an epicyclic gear reducer connecting the BP shaft to the fan shaft, characterized in that the BP body comprises three modules: a first module comprising the LP turbine and the LP shaft, the LP shaft comprising a downstream end coupled to the rotor of the LP turbine, a second module comprising the LP compressor and a journal secured to the rotor of the LP compressor, this journal being configured to be coupled in rotation to an upstream end of the LP shaft and to be axially immobilized on this end by screwing a nut onto a thread of the shaft, and a third module comprising an input shaft of the reducer, this input shaft comprising an upstream end for coupling to a solar of the reducer and a downstream end comprising first splines which are oriented parallel to said axis and which are configured to be engaged in second complementary splines of said second module,radially oriented screws being carried by one of the second and third modules and intended to be engaged in the other of the second and third modules in order to axially lock the first and second grooves in each other.

[0024] The LP body of the turbomachine is thus divided into three modules and no longer two as in most prior art turbomachines. The first, conventional module, comprises the LP turbine and the LP shaft. This LP shaft extends along the axis of the turbomachine and its downstream end is coupled to the rotor of the LP turbine.

[0025] The second module comprises the LP compressor, the rotor of which is conventionally connected to a journal. As in the prior art, this journal is engaged on the LP shaft and secured to the latter by a nut screwed axially from upstream. This second module is coupled by splines to a third module comprising the input shaft of the reducer. These splines are axially locked by radial screws. When the screws are in the unscrewed position, it is understood that the third module can be disassembled and removed from the second module.

[0026] The third module with the gearbox can be disassembled and removed from the turbomachine before having access to the unscrewing nut of the second module with respect to the first module. This has the advantage that the gearbox can have an internal diameter smaller than the diameter of the nut which is therefore no longer disassembled from the inside of the gearbox. The locking screws of the second and third modules are oriented radially and can therefore be unscrewed by a tool oriented in the same direction and which is also not hindered by the gearbox.

[0027] The turbomachine according to the invention may comprise one or more of the following characteristics, taken in isolation from one another or in combination with one another: the fan is of the unducted type; the reducer is located in a lubrication enclosure, said first and second splines being located outside this enclosure; the first and second splines are axially interposed between two annular seals of the enclosure, which are mounted between the input shaft and an annular cover of the enclosure mounted around the input shaft; a first of the seals, located upstream of the first and second splines, is a segmented radial seal, and a second of the segmented seals, located downstream of the first and second splines, is a labyrinth seal; one of the seals is axially interposed between said first and second splines, on the one hand, and said screws, on the other hand;the second module comprises an upstream shaft portion comprising said second splines and mounting holes for said screws, and a downstream shaft portion coupled or connected to said journal, said shaft portions comprising annular flanges fixed together by screws oriented parallel to said axis; the upstream shaft portion comprises a first radial annular wall whose outer periphery is connected to a first of the flanges, the downstream shaft portion comprises a second radial annular wall whose outer periphery is connected to a second of the flanges, said first and second annular walls extending opposite each other and conferring a capacity for flexural deformation to the second module in operation; this type of connection confers a certain flexibility to the module and is commonly called "flex coupling";and the turbomachine comprises a stator casing which surrounds the LP and HP bodies and which comprises at least one radial orifice configured to allow the passage of a tool for screwing / unscrewing said radial screws.;

[0028] The invention also relates to a method for dismantling a turbomachine, according to claim 10, as described above, characterized in that it comprises the steps of: unscrewing the radial screws so as to axially unlock said first and second splines, removing the third module from the second module, unscrewing the nut from inside the fan and the reducer, and removing the second module from the first module.

[0029] Advantageously, the radial screws are unscrewed using at least one unscrewing tool which is inserted through the or each hole in the casing. Brief description of the figures

[0030] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: [ Fig. 1 ] there figure 1 is a half schematic view in axial section of an aircraft turbomachine; [ Fig.2 ] there figure 2 is a schematic perspective and axial sectional view of a set of shafts within the meaning of one aspect of the invention; [ Fig.3 ] there figure 3 is a schematic sectional view of the entire figure 2 ; [ Fig.4 ] there figure 4 is a schematic perspective view of an axial spline locking system of the entire figure 2 , and shows screws in an unlocked position, [ Fig.5 ] there Figure 5 is a schematic sectional view of the axial locking system with the screws in the unlocked position, [ Fig.6 ] there figure 6is a schematic sectional view of the axial locking system with the screws in a locking position, [ Fig.7 ] there figure 7 is a larger scale view of part of the figure 6 ; [ Fig.8 ] there figure 8 is a view similar to that of the figure 1 and illustrates a first step of a method according to the invention for dismantling an aircraft turbomachine; [ Fig.9 ] there figure 9 is a larger scale view of part of the figure 8 ; And [ Fig. 10a-10c ] THE Figures 10a to 10c are views similar to those of the figure 1 and illustrate other steps in the disassembly process. Detailed description of the invention

[0031] We first refer to the figure 1 which illustrates an aircraft turbomachine which is herein a single unducted fan (USF) turbomachine 10 although aspects of the invention are not limited to this particular type of turbomachine.

[0032] The turbomachine 10 is modular and comprises several modules assembled together. The reference A designates the longitudinal axis of the turbomachine 10 which is generally the axis of rotation of its rotors.

[0033] A first module 12 is a high pressure or HP module and comprises an HP compressor 14 and an HP turbine 18. The rotor of the HP compressor 14 is connected by an HP shaft 16 to the rotor of the HP turbine 18. This HP module 12 further comprises the annular combustion chamber 20 which is axially interposed between the HP compressor 14 and the HP turbine 18.

[0034] The low pressure body or LP of the turbomachine 10 is itself divided into three modules: a first module 22 comprising the LP turbine 24 and the LP shaft 26, the LP shaft comprising a downstream end coupled to the rotor of the LP turbine, a second module 28 comprising the LP compressor 30, and a third module 32 comprising the input shaft 34 of a reducer 36 of the turbomachine.

[0035] The turbomachine 10 is in fact equipped with a reduction gear 36 with an epicyclic gear train which conventionally comprises a sun gear 38 centered on the axis A, a ring gear 40 which extends around the sun gear 38, and satellites which are arranged between the sun gear and the ring gear and which are meshed with them and carried by a planet carrier 42. In the present case, the ring gear 40 is stationary and fixed to a stator of the turbomachine which is here an input casing 44. The sun gear 38 is rotatable and coupled to the input shaft 34, and the planet carrier 42 is also rotatable and coupled to a shaft 46 of the fan 48. The fan 48 is therefore driven in rotation by the input shaft 34 via the reduction gear 36.

[0036] The reducer 36 is located in a lubrication enclosure 50 which extends around the axis A and therefore has a generally annular shape. At its inner periphery, the enclosure 50 is delimited by the fan shaft 46 and the input shaft 34. At its outer periphery, the enclosure 50 is delimited by the input casing 44 which extends around the reducer 36. At its upstream end, the enclosure 50 is delimited by an annular support 52 of bearings 54, 56. This support 52 has an outer periphery which is fixed to the input casing 44 and an inner periphery which holds rolling bearing rings of the rolling bearings 54, 56, the inner rings of which are fixed to the fan shaft 46. Finally, the enclosure 50 is closed at its downstream end by an annular cover 58 which is carried by the input casing 44 and the inner periphery of which surrounds the input shaft 34 in a sealed manner.

[0037] An intermediate casing 60 is interposed between the BP 30 and HP 14 compressors, an inter-turbine casing 62 is interposed between the HP 18 and BP 24 turbines, and an exhaust casing 64 is located downstream of the BP 24 turbine.

[0038] The LP compressor 28 and the HP module 12 are surrounded by an annular casing 66, an upstream end of which comprises an annular flange 66a for attachment to an annular flange 44a of the inlet casing 44, and a downstream end of which comprises an annular flange 66b for attachment to an annular flange 64a of the exhaust casing 64.

[0039] In addition to the LP compressor 30, the second module 28 comprises a journal 68 which is rotationally secured to the rotor of the LP compressor and which is configured to be rotationally coupled to an upstream end of the LP shaft 26 and to be axially immobilized on this end by screwing a nut 70 onto a thread of the LP shaft 26.

[0040] In the example shown, the journal 68 is engaged axially from upstream on the upstream end of the LP shaft 26. The nut 70 is engaged axially from upstream on the upstream end of the shaft 26 and is screwed until the journal 68 is axially tightened against an annular shoulder or the like of the shaft 26.

[0041] Although schematic, the figure 1 allows us to see that the nut 70 has a diameter which is greater than the internal diameter of the input shaft 34. This means that this input shaft 34 must be disassembled and removed in order to be able to remove the nut 70.

[0042] The second module 28 further comprises a shaft 72 divided into two portions 72a, 72b, respectively upstream and downstream. The shaft portions 72a, 72b are fixed together by clamping.

[0043] The upstream portion 72a is coupled to the input shaft 34 and comprises at its downstream end a radially external fixing flange 72aa. This flange 72aa is located at the external periphery of a radial annular wall 72ab of the downstream end of the portion 72a.

[0044] The downstream portion 72b is rotationally secured to the journal 68 and to the rotor of the LP compressor 30 and comprises at its upstream end a radially external fixing flange 72ba. This flange 72ba is located at the external periphery of a radial annular wall 72bb of the upstream end of the portion 72b.

[0045] The flanges 72aa, 72ba are applied axially against each other and comprise axial holes for mounting axial screws (not visible) for fixing the flanges together. This configuration of the flanges 72aa, 72ba and the radial walls 72ab, 72bb makes it possible to produce a connection with a certain flexibility. Thus, the shaft can withstand misalignment between the upstream and downstream parts, which is particularly advantageous in the case of a relatively long engine. The invention proposes a solution for facilitating the modularity of the turbomachine 10 thanks to a particular device for coupling the modules 28, 32 and in particular the shaft 72 of the second module 28 with the input shaft 34 of the third module 32.

[0046] THE figures 2 to 7 illustrate an embodiment of this device in which the elements already described in the above are designated by the same references.

[0047] The input shaft 34 of the module 32 is coupled to the shaft 72 of the module 28 and more specifically to the shaft portion 72a by a spline coupling 74, 76. The input shaft 34 comprises, in the vicinity of its downstream end, internal splines 74 which are oriented parallel to the axis A and which are configured to be engaged on complementary external splines 76 of the shaft portion 72a.

[0048] The coupling by splines 74, 76 is here of the axial locking type and this locking is here ensured by screws 78 oriented in a radial direction relative to the axis A.

[0049] The screws 78 are preferably regularly distributed around the axis A. Their number is for example between 6 and 12.

[0050] Each of the screws 78 is carried by and screwed into one of the shafts 34, 72 and intended to be engaged in the other of the shafts in order to axially lock the splines 74, 76 in each other. It is understood that each screw 78 is movable in the radial direction by screwing from a first radial position of axial locking of the shafts to a second radial position of axial unlocking of the shafts, and vice versa.

[0051] In the example shown, as is best seen in the figures 4 to 7 , each screw 78 is screwed into an orifice 80 of the shaft portion 72a and has a free end capable of being engaged in an orifice 82 of the shaft 34. Each screw 78 is movable by screwing from the aforementioned first radial position, which is a radially external position for screwing and tightening the screw, to the aforementioned second radial position, which is a radially internal position for unscrewing and loosening.

[0052] Each screw 78 comprises a threaded body of elongated shape along a radial axis relative to the axis A, and of which one longitudinal end (radially external) is free and of which the opposite longitudinal end (radially internal) is connected to a head 84. The body of each screw 78 is intended to be screwed into one of the orifices 80, the head 84 of each screw is intended to bear on the shaft portion 72a in the first tightening position, and the free end of each screw is intended to be engaged in one of the orifices 82 of the shaft 34 in this first position for the purpose of axially locking the splines 74, 76 and the shafts 34, 72.

[0053] Each screw 78 must be rotated and screwed by means of a tool which must also have a radial or quasi-radial orientation relative to the axis A. According to one aspect of the invention, the screwing and unscrewing of each screw are carried out radially from the outside and not from the inside of the turbomachine. The tool must therefore have access to the radially external end of each screw 78 and be able to be engaged with this end. Thus, the tool is not intended to be engaged with the head 84 of each screw 78 but on the contrary with the free end of the screw, which comprises for example a hollow imprint 81, as is schematically shown in figures 4 And 7 .

[0054] This imprint 81 may have a polygonal and, for example, hexagonal shape in section so as to receive a hexagonal bit of the tool, for example. Alternatively, it could be of the Torx ® type.

[0055] A tool 83 is schematically represented in figures 1, 2 And 9 to carry out the unscrewing of the screws 78, as well as their screwing. This tool 83 has an elongated shape and is engaged through one or more of the orifices 85 of the turbomachine 10. These orifices 85 can be located on stator elements of the turbomachine, such as the intermediate casing 44 or the casing 66 for example. These orifices 85 are for example endoscopy orifices, that is to say orifices which are generally used for inspection of the turbomachine by endoscopy. Naturally, these orifices must be aligned with each other and as much as possible with the axes of the screws 78. The rotation of the shaft 34 allows access to the screws 78 one after the other through the orifices 85.

[0056] In the example shown, a ring 86 is fixed in each orifice 82 of the shaft 34. This ring 86 comprises an internal bore which has a frustoconical portion 86a configured to cooperate with the free end of the screw 78 for the purpose of centering the latter in the orifice 82. The portion 86a is flared radially inwards. The ring 86 is here fixed by crimping in the orifice 82 and comprises at its radially external end a peripheral rim 86b intended to be plastically deformed and pressed against an internal rim 82a of the orifice 82 (see Figure 5 for example). It is therefore understood that the ring 86 is inserted radially from the inside into the orifice 82 and then is crimped into the orifice by deformation of its rim 86b.

[0057] Furthermore, in the example shown, each screw 78 is not directly screwed into one of the orifices 80 but into a sleeve 88 mounted in this orifice. This sleeve 88 has an internal thread 88a for screwing the screw 78 and further comprises at its radially internal end an annular collar 88b for bearing on a boss of the shaft 72 (see Figure 5for example). The sleeve 88 can be mounted by shrink fitting in the orifice 80 and comprise an external cylindrical surface mounted tightly in an internal cylindrical surface of the orifice 80. The sleeve 88 is engaged radially from the inside in the orifice 80 until the collar 88b bears on the boss of the shaft 72. The sleeve 88 and the ring 86 can be changed in the event of wear of their screw thread so as not to have to change the complete shaft. Advantageously, a retaining ferrule 90 is mounted inside the shaft 72 and has the function of ensuring retention of the screws 78 and thus making them captive when they are in their unscrewed positions.

[0058] The ferrule 90 has an annular shape and extends around the axis A. It comprises a first cylindrical rim 92 which is oriented downstream and which extends at least partly opposite the orifices 80, 82 and which is configured to radially retain the screws 78 when they are in their unscrewed positions, as illustrated in figures 4 And 5 .

[0059] The ferrule 90 preferably comprises an external cylindrical centering surface 90a configured to cooperate with an internal cylindrical surface of the shaft 72 to ensure the centering of the ferrule during assembly. The internal cylindrical surface of the shaft 72 may comprise an annular groove 94 for mounting an annular ring (not shown) for axially retaining the ferrule 90, for example against the aforementioned boss of the shaft 72.

[0060] The ferrule 90 further comprises a second cylindrical rim 94 which is oriented downstream and extends partly around this boss. The collars 88b of the bushings 88 are interposed radially between the boss and this rim 96, which ensures radial retention of the bushings in the orifices 80 and also makes them captive or immobilizes them radially.

[0061] THE figures 4 And 5 represent the screws 78 in their unscrewed positions for unlocking the shafts 34, 72. It can be seen that the heads 84 of the screws 78 are in radial support on the rim 92 of the ferrule 90 and that their free ends are at a radial distance from the orifices 82. The screws 78 therefore do not hinder the movement of the shafts 34, 72 relative to each other and the axial disengagement of the splines 74 from each other.

[0062] THE figures 6 And 7represent the screws 78 in their screwed positions for axially locking the shafts 34, 72. It can be seen that the heads 84 of the screws 78 are at a radial distance from the rim 92 of the ferrule 90 and that their free ends are engaged in the rings 86 of the orifices 82. The screws 78 prevent the displacement of the shafts 34, 72 relative to each other and the axial disengagement of the splines 74 from each other.

[0063] As regards the grooves 74, 76, the figures 2 And 3 in particular allow us to see that they are located outside the lubrication enclosure 50 of the reducer 36, and more precisely downstream of it.

[0064] In the example shown, the grooves 74, 76 are located axially between two annular sealing joints 98, 100 of the enclosure 50, namely the two joints located at the downstream end of the enclosure 50 and mounted between the cover 58 and the input shaft 34.

[0065] The seal 98 located upstream of the grooves 74, 76 is a segmented radial seal, and the seal 100 located downstream of the grooves is a labyrinth seal. The screws 78 are located downstream of the grooves 74, 76 and the seals 98, 100, the seal 100 being axially interposed between the grooves and the screws 78.

[0066] THE figures 2 And 3 also allow us to see that the diameters of the seals 98, 100, the grooves 74, 76 and the screws 78 are relatively close to each other.

[0067] We now refer to the figures 8 to 10c which illustrate the steps of dismantling the turbomachine 10 of the figure 1 It will be understood that the assembly or reassembly of the turbomachine can be used by repeating these operations in reverse order.

[0068] There figure 8 is similar to the figure 1 and the figure 9is a larger scale view in which certain references of the set of trees according to the invention described in the above are indicated.

[0069] A first step of the method consists of inserting the tool 83 through the orifices 85 of the turbomachine 10 and then unscrewing the screws 78, one after the other so as to bring them from their screwed positions to their unscrewed positions. This can be achieved by means of a single tool engaged in a single orifice 85 or in a single series of aligned orifices 85 if the shafts 34, 72 are rotated after each unscrewing so that the next screw to be unscrewed is aligned with the orifice(s) 85. Alternatively, in the case where there are as many orifices 85 or series of orifices 85 as there are screws 78, the same tool 83 could be inserted in turn into each of these orifices or each of these series of orifices.

[0070] The screws 78 are then in the unscrewed position so the splines 74, 76 and the shafts 34, 72 are free to move axially relative to each other or relative to each other. This means that the third module 32 can be separated from the second module 28. For this, it may be necessary to separate the flanges 44a, 66a from each other. After this separation, the entire upstream part of the turbomachine, which includes the module 28 but also the reduction gear 36, the fan 48 and the intermediate casing 44, can be removed from the rest of the turbomachine illustrated in Figure 10a . We thus understand that the enclosure 50 remains closed, which limits the risk of oil leakage.

[0071] Another step in the process is to unscrew the nut 70 securing the two modules 28, 22. It is unscrewed and removed from upstream. The situation is then obtained as illustrated in Figure 10b .

[0072] A next step of the method consists of separating the flanges 66b, 64a from each other and removing the exhaust casing 64 axially from downstream ( Figure 10c ). The first module 22 can then be removed by axial translation downstream with respect to the second module 28 as well as the HP module 12 and the inter-compressor 60 and inter-turbine 62 casings.

[0073] The various modules of the turbomachine 10 are separated from each other and can undergo maintenance operations with the reassembly of the turbomachine.

Claims

1. An aircraft turbomachine (10), this turbomachine having a longitudinal axis (A) and comprising: - a high-pressure body called HP comprising an HP shaft (16) for connecting a HP compressor rotor (14) to a HP turbine rotor (18), this HP shaft extending along said axis, - a low-pressure body called LP comprising a LP shaft (26) for connecting a LP compressor rotor (30) to a LP turbine rotor (24), this LP shaft extending along said axis and inside the HP shaft, - a fan (48) connected to a fan shaft (46), and - an epicyclic reduction gear (36) connecting the LP shaft (26) to the fan shaft (46), characterised in that the LP body comprises three modules: - a first module (22) comprising the LP turbine (24) and the LP shaft (26), the LP shaft comprising a downstream end coupled to the rotor of the LP turbine, - a second module (28) comprising the LP compressor (30) and a journal (68) secured to the rotor of the LP compressor, this journal being configured to be coupled in rotation to an upstream end of the LP shaft (26) and to be immobilised axially on this end by screwing a nut (70) onto a thread on the shaft, and - a third module (32) comprising an input shaft (34) of the reduction gear (36), said input shaft comprising an upstream end for coupling to a sun gear (38) of the reduction gear and a downstream end comprising first splines (74) which are oriented parallel to said axis and which are configured to be engaged in complementary second splines (76) of said second module (28), radially oriented screws (78) being carried by one of the second and third modules and intended to be engaged in the other of the second and third modules in order to axially lock the first and second splines in each other.

2. The turbomachine (10) of claim 1, wherein the fan (48) is of the unducted type.

3. The turbomachine (10) of claim 1 or 2, wherein the reduction gear (36) is located in a lubrication enclosure (50), said first and second splines (74, 76) being located outside said enclosure.

4. The turbomachine (10) of claim 3, wherein the first and second splines (74, 76) are interposed axially between two annular seals (98, 100) of the enclosure (50), which are mounted between the input shaft (34) and an annular cover (58) of the enclosure mounted around the input shaft.

5. The turbomachine (10) of claim 4, wherein a first of the seals (98), located upstream of the first and second splines (74, 76), is a segmented radial seal, and a second of the segmented seals (100), located downstream of the first and second splines, is a labyrinth seal.

6. The turbomachine (10) of claim 4 or 5, wherein one of the seals (100) is interposed axially between said first and second splines (74, 76), on the one hand, and said screws (78), on the other hand.

7. A turbomachine (10) according to any of the preceding claims, wherein the second module (28) comprises an upstream shaft segment (72a) comprising said second splines (76) and orifices (80) for mounting said screws (78), and a downstream shaft segment (72b) coupled or connected to said journal (68), said shaft segments (72a, 72b) comprising annular flanges (72aa, 72ba) secured together by screws oriented parallel to said axis.

8. The turbomachine (10) of claim 7, wherein the upstream shaft segment (72a) comprises a first radial annular wall (72ab), the external periphery of which is connected to a first of the flanges (72aa), the downstream shaft segment (72b) comprises a second radial annular wall (72bb), the external periphery of which is connected to a second of the flanges (72ba), said first and second annular walls extending opposite each other and imparting a bending deformation capability to the second module (28) in operation.

9. A turbomachine (10) according to any of the preceding claims, wherein it comprises a stator casing (44, 66) which surrounds the LP and HP bodies and which comprises at least one radial orifice (85) configured to allow the passage of a tool (83) for screwing / unscrewing said radial screws (78).

10. A method of dismantling a turbomachine (10) according to one of the preceding claims, characterized in that it comprises the steps of: - unscrewing the radial screws (78) so as to axially unlock said first and second splines (74, 76), - retracting the third module (32) from the second module (28), - unscrewing the nut (70) from inside the fan (48) and the reduction gear (36), and - retracting the second module (28) from the first module (22).

11. The method of claim 10, the turbomachine (10) being as defined in claim 9, wherein the radial screws (78) are unscrewed by means of at least one unscrewing tool (83) which is inserted through the or each hole (85) in the casing (44, 66).