ASSEMBLY FOR A TURBINE ENGINE

Abstract

The invention relates to an assembly for a turbine engine, comprising a radially inner shaft (3) and a radially outer shaft (7), said shafts (7, 8) being coaxial and extending along an axis (X), means (11, 15) for coupling said inner and outer shafts (7, 8) in rotation, means (22) for axially holding the inner shaft (8) relative to the outer shaft (7), means for centring the inner shaft (8) relative to the outer shaft (7), characterised in that the centring means comprise a shim (14) for radial centring and for axial positioning, this shim being frustoconical and interposed between a frustoconical centring surface (13) of the inner shaft (8) and a corresponding frustoconical centring surface (10) of the outer shaft (7).

Claims

1. An assembly for a turbomachine extending about an axis (X), comprising a radially inner shaft (8) and a radially outer shaft (7), said shafts (7, 8) being coaxial and extending along the axis (X), means (11, 15) for coupling the inner and outer shafts (7, 8) in terms of rotation, means (22) for axially holding the inner shaft (8) with respect to the outer shaft (7) means for centring the inner shaft (8) with respect to the outer shaft (7), characterised in that the means of centring comprise a frustoconical radial centring and axial positioning wedge (14) inserted between a frustoconical centring surface (13) of the inner shaft (8) and a complementary frustoconical centring surface (10) of the outer shaft (7).

2. An assembly according to claim 1, characterised in that the means of centring comprises a cylindrical centring surface (16) formed radially outwardly of the inner shaft (8), the cylindrical centring surface (16) cooperating with a complementary cylindrical centring surface (12) formed radially inwardly of the outer shaft (7), said cylindrical centring surfaces (16, 12) being axially offset with respect to the frustoconical centring surfaces (10, 13).

3. An assembly according to any of claim 1 or 2, characterised in that the wedge (14) is annular.

4. An assembly according to any of claims 1 to 3, characterised in that the wedge (14) has at least one mainly axially extending slot (17).

5. An assembly according to one of claims 1 to 4, characterised in that said slot (17) comprises a first end (18) opening axially at the level of an axial end (19) of the wedge (14) and a second end (20) situated axially between the axial ends (19, 21) of the wedge (14).

6. An assembly according to claim 5, characterised in that the second end (20) of the slot (17) has a circular orifice with a diameter greater than a transverse dimension of the slot.

7. An assembly according to one of claims 1 to 6, characterised in that the axial means of retention comprise at least one nut (22) screwed onto a threaded part (23) of the inner shaft (8) or onto a threaded part of the outer shaft (7) and coming to bear axially on an axial end-stop surface (9) of the outer shaft (7) or respectively of the inner shaft (8).

8. An assembly according to any of claims 1 to 7, characterised in that the angle of the

9. frustoconical surfaces (10, 13) with respect to the axis (X) is between 1 and 45°.

10. An assembly according to any of claims 1 to 8, characterised in that the angle of the

11. rotational coupling (11, 15) of the inner and outer shafts have splines.

12. A turbomachine (1) comprising, from upstream to downstream with respect to the direction of gas flow within the turbomachine (1), a fan (2), a high-pressure compressor (3), a low-pressure compressor (4), a combustion chamber, a high-pressure turbine (5)

13. and a low-pressure turbine (6), the low-pressure turbine (5) being rotatably coupled to a first shaft, the fan (2) being rotatably coupled to a second shaft, characterized in that it comprises an assembly according to one of claims 1 to 9, and in that the first shaft forms the inner shaft (8) of the assembly and the second shaft forms the outer shaft (7) of the assembly, or vice versa.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0034] FIG. 1 is a schematic half view of a turbomachine according to the invention,

[0035] FIG. 2 is a half axial sectional view of a part of an assembly according to one embodiment of the invention,

[0036] FIG. 3 is a perspective view of a wedge according to one embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0037] FIG. 1 shows the general structure of an X-axis turbomachine 1. This comprises, from upstream to downstream in the direction of air flow within the turbomachine 1, a fan 2, a low-pressure compressor 3, a high-pressure compressor 4, a combustion chamber (not shown), a high-pressure turbine 5 and a low-pressure turbine 6. The high-pressure compressor 4 and the high-pressure turbine 5 are connected via a high-pressure shaft and together form a high-pressure housing. The low-pressure compressor 3 and the low-pressure turbine 6 are also coupled in rotation.

[0038] Furthermore, as can be seen in FIG. 2, the rotor of the low-pressure compressor 3 has a shaft 7 and the rotor of the low-pressure turbine 6 has a shaft 8. These shafts 7, 8 are coaxial and are connected to the fan via a gearbox, e.g. an epicyclic gearbox.

[0039] In particular, FIG. 2 shows the assembly of the shaft 8 of the low-pressure turbine 6 and the shaft 7 of the low-pressure compressor 2.

[0040] The low-pressure compressor 3 shaft 7 extends radially outwards or around the low-pressure turbine shaft 8.

[0041] The radially inner surface of the low-pressure compressor 3 shaft 7, or outer shaft 7, has, in the area shown in FIG. 2 and from upstream to downstream, an annular radial shoulder 9, a frustoconical surface 10 flaring downstream, a rotational coupling zone with splines 11, and a cylindrical centring area 12. The diameter of the cylindrical area 12 is smaller than the diameter of the rotational coupling zone 11, which in turn is smaller than the smallest diameter of the truncated cone area 10.

[0042] The radially outer surface of the low-pressure turbine 6 shaft 8, or inner shaft 8, has, in the area shown in FIG. 2 and from upstream to downstream, a frustoconical surface 13 flaring downstream and cooperating with the frustoconical surface 10 of the outer shaft 7 by means of a frustoconical wedge 14, a rotational coupling zone comprising splines 15 cooperating with the splines 11 of the coupling zone of the external shaft 7, and a cylindrical centring zone 16 cooperating with the cylindrical zone 12 of the external shaft 7.

[0043] The splines 11, 15 of the inner and outer shafts 7, 8 ensure the rotational coupling of said shafts 7, 8. The cylindrical zones 12, 16 of the inner and outer shafts 7, 8 have approximately the same diameter, whereby a small amount of clearance can be provided for mounting if required.

[0044] The frustoconical wedge 14 is inserted radially between the frustoconical surfaces 10, 13 of the inner and outer shafts 7, 8.

[0045] The angle a of the frustoconical surfaces 10, 13 and the wedge 16 with respect to the axis X can be between 1 and 450.

[0046] The truncated cone shape of the centring surfaces 10, 13 and the wedge 14 allow precise centring of the inner shaft with respect to the outer shaft 7.

[0047] The wedge 14 and/or the corresponding frustoconical surfaces 10, 13 can be adapted depending on the dimensions and the axial and radial positioning of the inner shaft 8 with respect to the outer shaft, so as to ensure that the two shafts 7, 8 are not only well centred with respect to each other, but also well positioned axially with respect to each other. Such adaptation can be achieved by machining the frustoconical surfaces 10, 13 of the shafts 7, 8 and/or the wedge 14, or by an appropriate choice of the dimensions of the wedge itself.

[0048] Such a structure makes it possible to improve the dynamic behaviour of the assembly in operation, so as to reduce vibrations in particular.

[0049] As illustrated in FIG. 3, the wedge 14 has slots 7 extending axially over part of the axial dimension of the wedge 14. The number of slots 7 is equal to three but can vary according to need.

[0050] The presence of a slot 7 allows the wedge 14 to be deformed to conform to the actual shape of the frustoconical surfaces 10, 13 of the shafts 7, 8, in the event that the wedge 14 or said surfaces 10, 13 are not perfectly frustoconical.

[0051] Each slot 17 has a first end 18 that opens axially at the downstream end 19 of the wedge 14 and a second end 20 that is not open, located axially between the axial ends 19, 21 of the wedge 14.

[0052] Each slot 17 can extend over an axial dimension of between 50% and 90% of the axial dimension of the wedge 14.

[0053] The second end 20 of the slot 17 is rounded and has a radius of curvature greater than half the width I or transverse dimension of the slot 17, the width or transverse dimension being taken along a circumferential direction of the wedge 14.

[0054] The rounded zone formed at the second end 20 of the slot 17 is wider than the slot 17, which makes it possible to distribute the stresses more evenly and to avoid stress concentration effects that could lead to cracks or cracking within the wedge 14. Such a rounded zone 20 is also called a discharge zone.

[0055] A nut 22 is screwed onto a threaded portion 23 of the upstream end of the inner shaft 8. The threaded portion 23 is formed on the radially inner surface of the inner shaft 8. The upstream end 24 of the nut 22 extends radially and comes to bear on the radial shoulder 9 of the outer shaft 7.

[0056] The nut 22 is thus designed to prevent axial displacement, in a first axial direction, for example from upstream to downstream, of the inner shaft 8 with respect to the outer shaft 7. The axial displacement of the inner shaft 8 with respect to the outer shaft 7 in a second, opposite direction, e.g. from downstream to upstream, can be prevented by any suitable means, for example by an axial end-stop of the inner shaft 8 on the outer shaft 7.