ASSEMBLY OF SHAFTS OF A TURBOMACHINE INCLUDING AN ACTIVE INTER-SHAPED AXIAL TRANSLATION CONTROL SYSTEM OF A BODY AND A METHOD FOR ACTIVELY CONTROLLING AXIAL CLEARANCE BETWEEN A ROTOR ELEMENT AND A STATOR ELEMENT OF A TURBINE

Abstract

ASSEMBLY OF SHAFTS OF A TURBOMACHINE INCLUDING AN ACTIVE CONTROL SYSTEM FOR INTER-SHAPED AXIAL TRANSLATIONS OF A BODY AND A METHOD FOR ACTIVELY CONTROLLING AXIAL PLAY BETWEEN A ROTOR ELEMENT AND A STATOR ELEMENT OF A TURBINE Assembly of shafts of an aircraft turbomachine comprising: a drive shaft (40) including an upstream and downstream axial stop; a compressor shaft (41) including an upstream and downstream axial stop aligned axially between those of the drive shaft; an axial translation control system of the drive shaft relative to the compressor shaft, said control system comprising: an upstream pair of cams and a downstream pair of cams (46) housed between respectively the upstream axial stops (43a, 42) the downstream axial stops (43b, 46) each pair (46, 47) of cams comprising a fixed cam (46f, 47f) and a movable cam (46p, 47p) rotating about an axis Z to form an angle A with the movable cam of the upstream pair of cams.FIGURE 5.

Description

Title of the invention: ASSEMBLY OF SHAFTS OF A TURBOMACHINE COMPRISING AN ACTIVE INTER-SHEET AXIAL TRANSLATION CONTROL SYSTEM OF A BODY AND CONTROL METHOD ACTIVE AXIAL GAMES BETWEEN AN ELEMENT OF ROTOR AND A STATOR ELEMENT OF A TURBINE TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of aeronautics and particularly to the field of aircraft turbomachine shafts.

[0002] The invention relates to an assembly of shafts with an active control system for axial translation between two shafts by means of a double pair of cams. Another object of the invention is a method for controlling axial play between two turbine rotor elements / turbine stator part by using the active control system for two shafts of a single body. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] An aeronautical turbomachine conventionally comprises a combustion chamber and a body including a compressor and a turbine. The role of the turbine is to drive the compressor in rotation by coupling it to the rotation by two shafts, by extracting part of the pressure energy of the hot gases exiting the combustion chamber and transforming it into mechanical energy.

[0004] A turbomachine generally comprises a low-pressure body and a high-pressure body.

[0005] A compressor and a turbine of a high-pressure or low-pressure body each comprise a rotor portion rotating about an axis of rotation and a stator portion of the turbomachine. The turbomachine comprises a stator comprising each stator portion and a rotor per body comprising each the rotor portion of the compressor and the rotor portion of the turbine.2

[0006] The stator part is said to be fixed and comprises a housing and a plurality of fixed blades (because they do not rotate around the axis of rotation of the rotor part but can rotate freely about their own axis) fixed circumferentially to the housing or to housing ferrules. The rotor part comprises a drum including an assembly of several discs on which rotating blades are fixed circumferentially. Each row of fixed blades of the stator part, said Rectifiers form a rectifier or distributor. A row of moving blades and a row of fixed blades form a compressor stage.

[0007] During operation, thermal inertia and the forces applied to the turbine, for example at low pressure, result in greater expansion on elements of the turbine stator than on elements of the turbine rotor. It is therefore necessary to dimension the clearances between the ends of the turbine rotor elements and the opposite ends of the turbine stator as closely as possible to each other in order to maintain positive clearances at all times during a flight mission and prevent the two ends from coming into contact.

[0008] On the other hand, these games involve leaks and therefore a loss of engine efficiency which can lead to a decrease in performance and an increase in fuel requirements during a flight mission.

[0009] Figure 1 illustrates the axial displacements y as a function of time t during a flight mission. Curve 10 shows the displacements of one end of a stator element, and curve 11 shows the displacements of one end of a rotor element relative to the other end. Curve 12 illustrates the differential displacement (stator - rotor). A positive displacement indicates a shift of the assembly considered downstream of the axial flow. Positive values ​​of the differential displacement show that the displacement of the stator is greater than that of the rotor, implying a closing of the clearances where the stator is upstream of the rotor.

[0010] To avoid contact on this type of clearance, a sufficient margin must be provided to absorb the relative displacement of the stator downstream of the flow. Figure 2 schematically represents a half-axial cross-section of a gas turbine engine 1. The turbomachine 1, also called a gas turbine engine, comprises a fan 49 and four main sections: a low-pressure compressor 41, a high-pressure compressor 51, a high-pressure turbine 500, and a low-pressure turbine 400. The low-pressure compressor 41 and the low-pressure turbine 400 each comprise a rotor with rows of rotor blades 412, 402, each mounted on its own shaft 414, 404 (called the low-pressure compressor shaft 414 and the low-pressure turbine shaft 404), which are rotationally connected to each other by a low-pressure drive shaft 40.The low pressure compressor 41 and the low pressure turbine 400 each comprise rows of stator blades 416, 406 integral with a stator S.

[0011] Similarly, the high-pressure compressor 51 and the high-pressure turbine 500 each comprise a rotor including rotor blades 512, 502, each mounted on its own shaft 514, 504 (called the high-pressure compressor shaft 514 and the high-pressure turbine shaft 504) which are rotationally fixed to each other by a high-pressure drive shaft 50. The high-pressure compressor 51 and the high-pressure turbine pressure 500 each include in addition stator blades 516, 506 integral with the stator.

[0012] It is further represented in pentagons, an example of a non-contact clearance zone 413, 513, 503, 403 for each of the four main zones 41, 51, 500, 400, between a rotor blade and a stator blade. Figure 3 schematically represents a stator blade 6 and a rotor blade 2 of one of the four main zones 41, 51, 500, 400, and in particular that of zone 403. Such a clearance, however, results in air losses from the main flow to the outside. To limit these losses, the designer ensures an axial overlap zone 3 between the rotor blades 2 and the stator blades 6 during operation. In order to achieve the axial overlap 3, each stator blade 6 includes more or less long flaps 36 covering or covered by a platform 32 of the rotor blade 2. The length of these flaps 36 and platform 32 will be limited by the risk of contact between the rotor part and the stator part.

[0013] The axial alignment between the rotor blades is currently ensured by a shim, also called shim D48. Figure 4 shows, in its upper part, a very simplified schematic diagram of an example of a turbomachine comprising the stator S, the low-pressure compressor 41, and the fan 49, which are mounted here on a low-pressure compressor shaft 414 mounted on a front bearing Pla and a rear bearing Plr in the stator S. The turbomachine includes the low-pressure drive shaft 40 on which the low-pressure turbine 400 is mounted, and a rear bearing POr mounted in the stator S. The turbomachine further includes the high-pressure section 5 mounted between the low-pressure turbine 400 and the low-pressure compressor 410.The high-pressure part 5 includes the high-pressure shaft 50 on which is mounted the high-pressure compressor 51 and the high-pressure turbine 500 which are shown schematically without their bearings with the stator S, the high-pressure shaft here surrounds part of the drive shaft 40. The low-pressure compressor shaft 414 is rotationally fixed to the low-pressure turbine shaft 40 in a zone D by splines shown in [Fig.2] and in a dotted square illustrated in the lower part in [Fig.4]. The D48 shim is mounted in this area, and allows the same alignment between the low-pressure drive shaft 40 and the low-pressure compressor shaft 414 to be maintained. The inter-shaft alignment is ensured by a clamping nut 420. The low-pressure compressor shaft 414, mounted on the front bearing Pla and rear bearing Plr, allows the upstream part of the low-pressure drive shaft 40 to be joined with the stator S.Thus, the low-pressure compressor 41 provides the axial shimming link between the stator and the low-pressure drive shaft 40. The shim D48 has an axial thickness according to the specific axial measurements of the turbomachine elements in order to take into account the manufacturing tolerances of these elements.

[0014] This solution is not satisfactory however because it does not allow compensation, during the different phases of a flight mission, for the differential displacement between the rotor part and the stator part, in particular in areas 503 and 406, due to the hot gases expelled after the combustion chamber. Summary of the invention

[0015] The invention offers a solution to the problems mentioned above by proposing an active control system for axial play between a drive shaft and a compressor shaft, allowing the turbine rotor to be moved axially relative to the elements of the turbine stator part to compensate for its greater expansion than that of the turbine.

[0016] A first aspect of the invention relates to a set of shafts of an aircraft turbomachine comprising: • a drive shaft for a turbine having an axis of rotation X and comprising an upstream axial stop and a downstream axial stop; • a compressor shaft, said compressor shaft being rotationally coupled with the drive shaft and comprising an upstream axial stop and a downstream axial stop; • an axial translation control system between the drive shaft and the compressor shaft, said control system comprising: - a pair of upstream cams housed between the upstream axial stop of the compressor shaft and the upstream axial stop of the drive shaft; - a pair of downstream cams housed between the downstream axial stop of the compressor shaft and the downstream axial stop of the drive shaft;

[0017] Each pair of cams comprising a fixed cam rotating about an axis Z parallel to the axis X and a movable cam rotating about the axis Z, each cam having an external face and an internal face, each internal face having at least one ramp, the internal face of the fixed cam being in contact with the internal face of the movable cam, the movable cam of the downstream pair of cams being pivoted about the axis Z to form an angle A with the movable cam of the upstream pair of cams, so that when the distance between the external faces of the upstream pair is at its maximum, the distance between the external faces of the cams of the downstream pair is at its minimum.

[0018] In the description, the terms "upstream" and "downstream" are defined with respect to the direction of air flow from the air inlet of the turbomachine to the air outlet of the turbomachine, i.e., from the upstream end of the compressor shaft to the downstream end of the drive shaft located opposite the upstream end. in the assembly of shafts according to the aspect of the invention, (downstream end of the compressor shaft being that closest to the drive shaft).

[0019] The inner face of a cam is defined as the face that is opposite and in contact with the other cam in the pair. In other words, the inner face of one cam is always opposite the inner face of another cam. The outer face of a cam is defined as the face opposite the inner face. In other words, the outer face of a cam is always opposite one of the two axial stops of the compressor shaft or the drive shaft.

[0020] The distance between the outer faces of two cams belonging to the same pair of cams is also called the length of the pair of cams. The maximum distance between the outer faces of a pair of cams is understood to be the maximum distance between the two outer faces, with the inner faces in contact at at least one point. The minimum distance between the outer faces of a pair of cams is understood to be the minimum distance between the two outer faces, with the inner faces in contact at at least one point.

[0021] A ramp is defined as a portion of the inner face of a cam that protrudes along the Z-axis. In other words, each cam has a variable thickness along the Z-axis around its circumference. For example, each cam could be a drum cam.

[0022] The external faces of each pair of cams are in contact respectively with an axial stop of the drive shaft and of the compressor shaft, so as to ensure the movement of the compressor shaft relative to the drive shaft and therefore the movement of the turbine rotor.

[0023] Thanks to the presence of the offset angle A between the moving cam of the upstream pair and the moving cam of the downstream pair, it is possible to simultaneously actuate both moving cams so as to axially displace the turbine shaft relative to the compressor shaft while keeping the sum of the lengths of the two pairs of cams constant. This maintains the axial inter-shaft clamping. With the compressor shaft axially braced against the stator, when the drive shaft moves relative to the compressor shaft at axial brace, the turbine blades move axially relative to the stator. The turbine components are thus axially displaced to compensate for the displacement of the stator components due to thermal expansion.

[0024] In other words, the axial translation control system of the shaft assembly according to one aspect of the invention makes it possible to modify the clearance between the first ends of the turbine rotor elements with respect to the ends (opposite the first ends) of the turbine stator part "when hot", namely during the operation of the low-pressure or high-pressure turbine, for example during a flight mission. This is achieved by using two variable-length shims instead of a single constant-length shim, as in the prior art. These two shims are, respectively, the upstream cam pair and the downstream cam pair. Each cam pair includes a steerable cam that rotates around the Z-axis. In other words, the two cams in a cam pair can rotate relative to each other (one is stationary in rotation about the Z-axis, and the other is movable in rotation about the Z-axis) to lengthen or shorten the overall thickness of a cam pair, measured between the outer surface of the movable cam and the outer surface of the fixed cam in each pair. The two cams in an upstream or downstream cam pair rotate relative to each other by steering the rotation of the movable cam around the Z-axis.The two movable cams can be driven by a device that controls both movable cams, either individually or simultaneously. During the rotation of the movable cam of each pair of cams around the X-axis, the sum of the distances between the outer faces of the cams of the upstream pair and the distances between the outer faces of the cams of the downstream pair remains constant. This ensures that the drive shaft, and therefore the turbine shaft, is properly aligned with the compressor shaft, while simultaneously moving them axially relative to the upstream axial stop. This prevents contact between the stator and rotor blades, particularly at the turbine's vanes and platforms.Thus, the solution allows the function of the prior art wedge to be retained while controlling the axial displacement of the turbine shaft to avoid contact between one end of a rotor element and one end of a stator element of the turbine.

[0025] Thanks to the positioning of the compressor shaft or drive shaft on either side of the upstream / downstream axial stops, the upstream and downstream cam pairs cooperate to offset the compressor shaft upstream or downstream relative to the drive shaft. Since the compressor shaft, when mounted in a turbomachine bearing, is axially stopped and fixed in axial translation relative to the stator bearing, the compressor shaft does not translate axially relative to the stator. Thus, the offset of the drive shaft relative to the compressor shaft allows the elements of the turbine rotor section to be offset axially relative to the stator, either upstream or downstream. This maintains a constant distance between the elements of the rotor and stator sections.

[0026] It is important to note that, thanks to the angular offset of the movable cam of the downstream wedge (pair of cams) relative to the movable cam of the upstream wedge (pair of cams) and thanks to the simultaneous piloting of these two movable cams, an axial lengthening or reduction of the downstream wedge by a length l corresponds respectively to an axial reduction or lengthening of the upstream wedge by the same length l. By The axial lengthening of a shim refers to the movement of the two outer surfaces of the cams in a pair of cams away from each other, while the axial reduction of a shim refers to the movement of the two outer surfaces of the cams in a pair of cams towards each other. For example, the lengthening of the downstream shim due to a rotation of its moving cam is compensated by a reduction of the upstream shim achieved by a timely rotation of its moving cam. This keeps the sum of the axial lengths of the two shims constant, thus maintaining the axial inter-shaft clamping (of the compressor / drive shaft) regardless of any offset between the rotor and stator sections.

[0027] Finally, the invention is adaptable to a low-pressure or high-pressure body. The drive shaft can be axially and rotationally fixed to a turbine shaft (low pressure or high pressure), or it can be a single unit with the turbine shaft, or it can itself be the turbine shaft. Thus, the compressor shaft can be that of a low-pressure or high-pressure compressor, and the drive shaft can be that driven by a low-pressure or high-pressure turbine, or it can be the turbine shaft of a low-pressure or high-pressure turbine, respectively.

[0028] In one example, the fixed cam of the upstream pair is identical to the fixed cam of the downstream pair. In another example, the movable cam of the upstream pair is identical to the movable cam of the downstream pair. In one embodiment, all the cams have an identical inner face, namely an inner face having the same ramp or the same set of ramps.

[0029] According to one embodiment: - the drive shaft includes a recess forming, on either side, the upstream axial thrust bearing and the downstream axial thrust bearing of the drive shaft and - the compressor shaft includes a tooth housed in the recess forming on either side the upstream axial stop and the downstream axial stop of the compressor shaft.

[0030] According to another embodiment: - the drive shaft includes a tooth forming, on either side, the upstream axial thrust bearing and the downstream axial thrust bearing of the drive shaft and - the compressor shaft includes a recess housing the tooth, forming on either side the upstream axial stop and the downstream axial stop of the compressor shaft.

[0031] According to an example of one of the two preceding embodiments: - The external face of the fixed cam of the upstream cam pair is in contact with the upstream axial stop delimiting the recess; - The outer face of the moving cam of the upstream cam pair is in contact with an upstream face of the tooth forming the upstream axial stop; - The external face of the fixed cam of the downstream cam pair is in contact with a downstream face of the tooth forming the downstream axial stop; - The outer face of the moving cam of the downstream cam pair is in contact with the downstream axial stop delimiting the recess.

[0032] This arrangement ensures good contact between the outer faces of the cams and, respectively, the axial stops defining the recess, for example, of the turbine shaft and the tooth, for example, of the compressor shaft. This allows the compressor shaft to be offset relative to the turbine shaft by varying the lengths of the shims.

[0033] It is important to note that this arrangement of the fixed and moving cams in each pair of cams can be reversed. For example, the outer face of the upstream fixed cam can be in contact with an upstream wall of the tooth and the outer face of the upstream moving cam can be in contact with the upstream axial stop of the recess. Similarly, the arrangement of the downstream fixed cam and the downstream moving cam can be reversed.

[0034] According to one example, the drive shaft includes a clamping nut screwed onto a portion of the thread of the drive shaft and distant from a rim of the drive shaft forming between them the recess, the clamping nut including a downstream face forming the upstream axial stop delimiting the recess and the rim forming the downstream axial stop delimiting the recess; this allows the use of an element already in place in the junction of the two shafts using a shim of constant thickness (axial length) while having a clamping means allowing to avoid a large play between the drive shaft and the compressor shaft causing vibrations and friction.

[0035] In one or more embodiments, each cam has a circular section along a cutting plane normal to the Z axis, the outer face of each cam being flat and normal to the Z axis; the use of flat outer faces makes it possible to improve the contact between the cams and respectively the axial stops.

[0036] In one or more embodiments, the fixed cam of the upstream cam pair and the fixed cam of the downstream cam pair are press-fitted to the turbine shaft. This improves the rotational clamping force around the Z-axis during operation between the fixed cam and the rotor shaft, thereby enhancing control of the axial translation of the two moving cams relative to the turbine shaft and, consequently, of the turbine shaft itself during rotation. This solution also improves axial clamping along the Z-axis, thus preventing unintended movement of the nut or wear.

[0037] In one or more embodiments, each inner face comprises a single ramp, and the pivot angle A of the downstream movable cam is equal to 180 degrees. This arrangement allows the position of the movable cams to be adjusted so as to keep the sum of the lengths of the two shims constant while offsetting the low-pressure compressor shaft relative to the turbine shaft. Furthermore, using this pivoting of The 180° rotation prevents friction between the moving cams and the axial stops, thus reducing or even eliminating wear. Furthermore, in the example of a nut where one face forms an upstream axial stop, this prevents both the risk of the nut loosening and wear on that face.

[0038] According to an example in one or more embodiments, the movable cams comprise a material enabling sliding between the movable cams and the low-pressure drive shaft.

[0039] According to one embodiment, the compressor shaft and the low-pressure drive shaft are rotationally fixed to each other by splines allowing only axial translation relative to each other.

[0040] According to one embodiment, the shaft assembly is a low-pressure shaft assembly.

[0041] According to one embodiment, the shaft assembly is a high-pressure shaft assembly.

[0042] According to one embodiment, comprising a turbine shaft fixed in rotation and axially to the drive shaft. In one example, the turbine shaft is mounted on the drive shaft in a manner fixed in rotation and axially. In another example, the drive shaft and the turbine shaft are a single unit.

[0043] According to another embodiment, the drive shaft is a turbine shaft.

[0044] According to one example, the drive shaft is a high-pressure turbine shaft.

[0045] According to one embodiment, the drive shaft is adapted to pass axially through an orifice surrounded by a combustion chamber of the turbomachine in order to couple the turbine in rotation to a compressor of the same body of the turbomachine. In other words, the combustion chamber surrounds a part of the drive shaft.

[0046] According to another embodiment, the compressor shaft passes axially through a combustion chamber and the drive shaft is a turbine shaft adapted to drive the rotation of turbine blades.

[0047] Another aspect of the invention relates to a turbomachine comprising: - a stator comprising a turbine stator section and a compressor stator section, - a rotating part comprising the set of shafts according to the first aspect of the invention, in which • The drive shaft is movable in translation relative to the stator by the axial translation control system, • rotating turbine blades fixed in rotation and axially to the drive shaft, • fixed blades of the turbine stator section opposite the moving turbine blades, - a front bearing mounted in the stator part of the compressor, in which the compressor shaft is mounted for rotation and is against axial stop, - in which the control system axially displaces the movable blades relative to the fixed blades of the turbine during the rotation of the movable cams.

[0048] According to one embodiment, the turbomachine comprises - a low-pressure turbine comprising movable rotor blades and stator blades, a low-pressure turbine shaft fixed in rotation and axially to the drive shaft and the rotor blades to couple them, - a rear bearing mounted between the drive shaft and the stator to support the drive shaft, in which the drive shaft is movable in axial translation relative to the bearing.

[0049] Another aspect of the invention relates to a method for controlling axial play between one end of a turbine rotor element and one end of an element of a turbine stator part by using the shaft assembly according to the first aspect of the invention by controlling the translation control system, said control method comprising the following steps: • Determination of a target distance between a stator element and a rotor element; • Measurement of the distance between the stator element and the rotor element; • Determining the difference between the target distance and the measured distance; • Pivoting, based on the determined gap, of the movable cams so as to reduce the gap determined during the determination step, the sum of the distance separating the external faces of the cams of the upstream pair of cams and the distance separating the external faces of the cams of the downstream pair of cams being constant.

[0050] The target distance between a stator element and a rotor element is defined as a predetermined distance that both reduces losses in the main air stream and prevents contact between the rotor and stator sections. The target distance may vary during a flight mission and depend, for example, on the phase of the flight mission.

[0051] Thanks to the method according to the second aspect of the invention, it is possible to actively control the distance between the rotor elements and the stator elements, so as to compensate for the differential displacement between these two sets of elements. The method according to the second aspect of the invention makes it possible to adapt the axial translation of the transmission shaft relative to the stator so as to axially displace the turbine rotor elements relative to those of the turbine stator part in order to avoid contact between them, while avoiding degradation of engine performance.

[0052] Thanks to the arrangement of the two pairs of cams, an axial lengthening of one of the two pairs corresponds to a simultaneous reduction in the axial length of the other pair, so as to maintain the sum of the lengths of the two shims. This also ensures inter-shaft clamping for any misalignment of the rotor part relative to the stator part.

[0053] In one or more embodiments, the distance between the rotor element and the stator element is measured using a distance sensor or a contact sensor.

[0054] In one or more embodiments, the pivoting step includes the simultaneous pivoting of the movable cam of the upstream cam pair and the movable cam of the downstream cam pair.

[0055] In one or more embodiments, the pivoting step is carried out using an automatic flight parameter control system.

[0056] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0057] Other advantages and features of the invention will become apparent from the following description, illustrated by the figures, among which:

[0058] Fig. 1 illustrates a graph representing the axial displacements of the rotor part and the stator part of a low-pressure turbine according to the prior art;

[0059] Fig. 2 schematically illustrates a half axial section of a turbomachine to illustrate axial clearances between elements of the rotor part and the stator part;

[0060] Fig. 3 illustrates a schematic diagram of a stator blade and a rotor blade to illustrate an axial overlap zone in a low-pressure turbine;

[0061] Fig. 4 illustrates a schematic diagram of a turbomachine and an enlargement of an area including an example of inter-shaft alignment between a low-pressure drive shaft and a low-pressure compressor shaft according to the prior art;

[0062] Fig. 5 illustrates an embodiment of part of a low-pressure shaft assembly with an active axial translation control system according to the first aspect of the invention;

[0063] Fig. 6a schematically illustrates a side view of one embodiment of a cam;

[0064] Fig. 6b illustrates a cross-sectional view of the cam shown in Fig. 6a;

[0065] Fig. 6c illustrates a cross-sectional view of an embodiment of a pair of upstream cams and a pair of downstream cams;

[0066] Fig. 7 schematically illustrates a flowchart of an embodiment of a process according to the second aspect of the invention;

[0067] Figure 8 illustrates a graph representing the axial displacements of the rotor part and the stator part of a low-pressure turbomachine according to the first aspect of the invention. DETAILED DESCRIPTION

[0068] Figures 1 and 4 have been described in relation to the prior art and Figures 2, 3 already described also apply to an aspect of the invention described below.

[0069] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0070] For the purposes of understanding the invention, the radial (R), tangential (T), and axial (A) orientations will be adopted according to the RTA coordinate system shown in the figures, the tangent (T) and axial (A) axes of which extend in a horizontal plane along the orientation shown in the figures. The axial axis A is parallel to an axis of rotation X of an aircraft turbomachine comprising the axial translation control system according to one aspect of the invention.

[0071] The shaft assembly of the invention may be that of a low-pressure body or that of a high-pressure body. The description is given for a low-pressure body but can be applied to a high-pressure body. The same applies to a method for controlling axial play between one end of a turbine rotor element and one end of a turbine stator element using the shaft assembly.

[0072] Figure 5 illustrates an embodiment of a set of shafts, in this case low pressure, according to one aspect of the invention.

[0073] According to the example illustrated in [Fig. 5], the assembly comprises a drive shaft 40 fixed to the rotor of the low-pressure turbine (not shown) and a compressor shaft 414 of the low-pressure compressor. The compressor shaft 414 is radially external to the low-pressure drive shaft 40. The two shafts are coaxial. The low-pressure drive shaft 40 and the compressor shaft 414 are rotationally locked together by splines 40.1.

[0074] The low pressure drive shaft 40 includes an upstream axial stop 42 and a downstream axial stop 45 delimiting between them in this example a recess 44.

[0075] According to the embodiment illustrated in [Fig. 5], the low-pressure drive shaft 40 comprises an inter-shaft clamping nut 420 mounted on a threaded portion of a shaft of the drive shaft 40, the downstream face of which is the nut 420 forms the upstream axial stop 42. The downstream axial stop 45 is a rim of the low pressure drive shaft 40.

[0076] The compressor shaft 414 includes an upstream axial stop 43a and a downstream axial stop 43b aligned with the upstream and downstream axial stops 42, 45. In this case, the compressor shaft includes a tooth 43 comprising on each of its axial end faces, the upstream axial stop 43a and the downstream axial stop 43b.

[0077] The recess 44 is sized to accommodate: • tooth 43 at least partially lodged in the recess 44; • a pair of upstream cams 46 positioned upstream of tooth 43 and at less partially housed in recess 44; • a pair of downstream cams 47 positioned downstream of the tooth 43 and at least partially housed in the recess 44.

[0078] The two pairs of cams 46 and 47 form an active control system for axial translations in both directions between the compressor shaft 414 and the drive shaft 40 to control the axial clearances between the elements of the rotor part and the stator part of the turbine, in this case low pressure.

[0079] Figure 6a illustrates a three-dimensional side view of an embodiment of a cam C. According to the example shown in Figure 6a, the cam C comprises an inner face Ci and an outer face Ce opposite the inner face Ci. The inner face Ci is intended to be in contact with another cam, for example, with the inner face of another cam. The outer face Ce is intended to be in contact with an axial stop element or with the tooth 43. The cam C further comprises a ramp R, namely a region of the inner face Ci extending axially along the Z-axis and projecting outwards.

[0080] Figure 6b illustrates a cross-sectional view of the cam C along a cutting plane passing through face Z. In the example shown in Figure 6b, the outer face Ce of the cam C is flat and normal to the Z axis. The inner face Ci comprises a flat portion and a portion including the ramp R. The ramp R projects along the Z axis relative to the flat portion of the inner face Ci.

[0081] In other embodiments, each cam may comprise a plurality of ramps R extending axially along the Z axis.

[0082] Fig. 6c illustrates an example of an embodiment of the two pairs of upstream cams 46 and downstream cams 47.

[0083] In the example illustrated in [Fig. 6c], the upstream cam pair 46 comprises a fixed upstream cam 46f and a movable upstream cam 46p. The fixed upstream cam 46f comprises an external face 46f.e and an internal face 46f.i. The movable upstream cam 46p also comprises an internal face 46p.i and an external face 46p.e. The internal face of the fixed upstream cam 46f.i is opposite and in contact with the internal face of the movable upstream cam 46p.i. Each internal face includes a ramp R extending axially from the cam along the Z axis.

[0084] According to the example illustrated in [Fig. 6c], the downstream cam pair 47 comprises a downstream fixed cam 47f and a downstream movable cam 47p. The downstream fixed cam 47f comprises an external face 47f.e and an internal face 47f.i. The downstream movable cam 47p also comprises an internal face 47p.i and an external face 47p.e. The internal face of the downstream fixed cam 47f.i is opposite and in contact with the internal face of the downstream movable cam 47p.i. Each internal face comprises a ramp R extending axially from the cam along the Z-axis.

[0085] In the example illustrated in [Fig. 6c], the downstream movable cam 47p is mounted pivotally about the Z-axis relative to the upstream movable cam 46p. Thanks to this mounting, when the length of the upstream cam pair 46 is at its maximum Lmax, the length of the downstream cam pair 47 is at its minimum Lmin. In the case illustrated in [Fig. 6c], the angular offset A between the upstream movable cam 46p and the downstream movable cam 47p is 180 degrees.

[0086] It is important to note that thanks to the assembly illustrated in [Fig.6a] and [Fig.6c], simultaneous control of the movable cams 46p and 47p makes it possible to keep the sum of the lengths of the two pairs of cams 46 and 47 constant. Here, the length of a pair of cams is understood to be the distance separating the two external faces of the pair of cams, measured along the Z axis.

[0087] This mechanism allows control of the axial offset between the compressor shaft 414 and the drive shaft 40, thus allowing control of the axial clearances between elements of the turbine rotor part and elements of the stator part while maintaining the inter-shaft clamping.

[0088] It is important to note that the mounting order of the fixed and moving cams of the cam pairs illustrated in [Fig. 6c] is irrelevant for the implementation of the invention, provided that the angular offset and simultaneous pivoting of the two moving cams are carried out as explained above. In other words, it is not necessary to position the fixed cams upstream of the moving cams. Indeed, it would also be possible to position the moving cams upstream of the fixed cams.

[0089] Each movable cam is driven in rotation by any known means of rotational drive, whether directly by a motor, via gears, or by one or more connecting rods. The drive means may be a system driving both movable cams simultaneously, or two systems driving the movable cam individually but controlled to rotate simultaneously. For example, a connecting rod system to actuate the two movable cams simultaneously in a phased manner to modify the clearances but maintain the clamping force between the two shafts (compressor and drive), or a system controlling each movable cam's rotation independently. According to a For example, each cam has teeth on its periphery that mesh with a corresponding wheel, the two wheels being driven in rotation by the same motor or hydraulic system.

[0090] Intentional downstream shift of the turbine rotor

[0091] The downstream movable cam 47p is actuated to lengthen the downstream cam pair 47. Simultaneously, the upstream movable cam 46p is actuated to reduce the length of the cam pair 46 by an amount equal to the increase in the length of the downstream cam pair 47. This double pivoting allows the rotor portion to be shifted downstream. The tightening of the nut 420 is ensured by the fact that the sum of the lengths of the two cam pairs is constant.

[0092] Intentional offset of the turbine rotor towards the upstream

[0093] The movable cam 46p of the upstream cam pair 46 is actuated to increase its length. Simultaneously, the downstream movable cam 47p is actuated to reduce its length by an amount equal to the increase in length of the upstream cam pair. This allows the rotor portion to be shifted downstream while maintaining the inter-shaft clamping, i.e., while preserving the sum of the lengths of the two cam pairs.

[0094] Thus, the turbomachine 1 according to one aspect of the invention is similar to that shown in [Fig. 2] and 3 of the prior art, except that it comprises a set of shafts according to the first aspect of the invention. The turbomachine therefore comprises a stator S comprising a turbine stator part and a compressor stator part, a rotating part comprising the set of shafts according to the first aspect of the invention, for example, that described in the description of a low-pressure body. The drive shaft 40 is movable in translation relative to the stator by the axial translation control system. The turbine comprises rotor blades 2 such as, for example, those described with reference to [Fig. 3], movable in rotation relative to the stator and fixed in rotation and axially to the drive shaft 40. The turbine 400, 500 comprises fixed stator blades 6, 406, such as, for example, those described with reference to [Fig. 3].3], of the turbine stator part opposite the rotor blades 2, 402 of the turbine. The turbomachine includes a front bearing Pla mounted in the compressor stator part, in which the compressor shaft 414 is mounted in rotation and in axial stop by being fixed in axial translation with the front bearing Pla and therefore with the stator S.

[0095] The control system axially displaces the movable rotor blades relative to the fixed blades during the rotation of the movable cams.

[0096] The turbomachine 1, in the case of the example described above, comprises a low-pressure turbine 400 including the moving blades 2, 402 and the turbine blades fixed 6, 406, a low pressure turbine shaft 404 fixed in rotation and axially with the drive shaft 40 and the turbine blades to couple them.

[0097] The turbomachine 1 includes a rear bearing POr mounted between the drive shaft 40 and the stator S to support the drive shaft 40, in which the drive shaft is movable in axial translation relative to the bearing POr.

[0098] According to one embodiment, the rotation control of the movable cams to lengthen and shorten the distance between two external surfaces of the cams of the two pairs of cams is managed by an automatic flight parameter control system such as the FADEC system. The rotation is performed by an individual or simultaneous system.

[0099] Fig. 7 illustrates an example of an embodiment of a method 90 for controlling axial play between one end of a turbine rotor element and one end of an element of a turbine stator part by using the shaft assembly to control the axial translation control system between a drive shaft by a turbine and a compressor shaft, here in this case low pressure, according to another aspect of the invention.

[0100] As illustrated in [Fig.7], the method 90 according to one aspect of the invention includes a step of determining 91 a target distance between a stator element and a rotor element.

[0101] The target distance can be determined, for example, according to the phase of the flight mission or according to other parameters of the turbomachine.

[0102] The method 90 further comprises a step 92 of measuring the distance between the stator element and a rotor element. The distance is measured, for example, using a sensor, such as an optical sensor or a contact sensor.

[0103] The difference between the target distance and the measured distance is determined during a determination step 93. The comparison of these two distances makes it possible to determine whether it is necessary to offset the rotor part relative to the stator part in order to maintain the target distance.

[0104] In the example illustrated in [Fig. 7], the method 90 further includes a pivoting step of the movable cams. During the pivoting step 94, the angular positions of the two movable cams are changed simultaneously so as to move the rotor part relative to the stator part while maintaining the sum of the axial lengths of the cam pairs.

[0105] The pivoting step 94 may for example include the simultaneous pivoting of the two movable cams.

[0106] Figure 8 shows a graph representing the difference between the axial displacements y of the stator part and the rotor part as a function of time t during a flight mission, namely the difference between an element of the stator part and an element of the rotor in with respect to each other, as a function of time. Curve 80 shows the difference in axial displacements in the absence of an active control system according to one aspect of the invention. The offset between the stator and rotor sections varies over time and is always positive. Curve 81 shows the difference in axial displacements in the presence of the active control system for axial translations of the shaft assembly according to one aspect of the invention. It is evident that in a low-pressure turbine according to one aspect of the invention, the distance between the rotor and stator sections is constant thanks to the dynamic compensation of the axial offset.

Claims

1. Demands Assembly of shafts of an aircraft turbomachine comprising: - a drive shaft (40, 50) adapted to be driven by a turbine (400, 500), having an axis of rotation X and comprising an upstream axial stop (42) and a downstream axial stop (45); - a compressor shaft (414, 514), said compressor shaft (414) being rotationally coupled with the drive shaft (40) and comprising an upstream axial stop (43a) and a downstream axial stop (43b); - a system for controlling axial translation between the drive shaft (40) and the compressor shaft (414), said control system comprising: • a pair of upstream cams (46) housed at least between the upstream axial stop (43a) of the compressor shaft (414) and the upstream axial stop (42) of the drive shaft (40); • a pair of downstream cams (47) housed between the downstream axial stop (43b) of the compressor shaft (414) and the downstream axial stop (46) of the drive shaft (40); - each pair (46, 47) of cams comprising a fixed cam rotating (46f, 47f) about a Z-axis parallel to the X-axis and a movable cam rotating (46p, 47p) about the Z-axis, each cam (46f, 47f, 46p, 47p) having an external face (46f.e, 46p.e, 47f.e, 47p.e) and an internal face (46f.i, 46p.i, 47f.i, 47p.i), each internal face (46f.i, 46p.i, 47f.i, 47p.i) having at least one ramp (R), the internal face of the fixed cam (46f.i, 47f.i) being in contact with the internal face of the movable cam (46p.i, 47p.i), the movable cam of the pair of downstream cams (47p) being pivoted around the Z axis to form an angle A with the movable cam of the upstream pair of cams (46p), so that when the distance between the external faces (46f.e,46p.e) of the cams of the upstream pair (46) is at its maximum, the distance between the external faces (47f.e,47p.e) of the cams of the downstream pair (47) is at its minimum.

2. Assembly of shafts according to the preceding claim in which: - the drive shaft (40, 50) or the compressor shaft (414, 514) comprises a recess (44) forming on either side the upstream axial thrust bearing (42) and the downstream axial thrust bearing (45) respectively of the drive shaft (40, 50) or the compressor shaft (414, 514) and - respectively the compressor shaft (414, 514) or the drive shaft (40, 50) comprises a tooth (43) housed in the recess (44), the tooth (43) forming on either side the upstream axial thrust bearing (43a) and the downstream axial thrust bearing (43b) of respectively the compressor shaft (414, 514) or the drive shaft (40, 50).

3. Assembly of shafts according to the preceding claim in which: - The external face (46f.e) of the fixed cam of the upstream cam pair is in contact with the upstream axial stop (42) delimiting the recess (44); - The external face (46p.e) of the movable cam (46p) of the upstream cam pair (46) is in contact with an upstream face of the tooth (43) forming the upstream axial stop (43a); - The external face (47f.e) of the fixed cam (47f) of the downstream cam pair (47) is in contact with a downstream face of the tooth (43) forming the downstream axial stop (43b); - The external face (47pe) of the mobile cam (47p) of the downstream cam pair (47) is in contact with the downstream axial stop (45) delimiting the recess (44).

4. Assembly of shafts according to the preceding claim in which the drive shaft (40, 50) comprises a clamping nut (420) screwed onto a portion of the thread of the drive shaft (40, 50) and distant from a rim of the drive shaft (40, 50) forming between them the recess (44), the clamping nut (420) comprising a downstream face forming the upstream axial stop (42) delimiting the recess (44) and the rim forming the downstream axial stop (45) delimiting the recess (44).

5. Assembly of shafts according to any one of the preceding claims wherein the fixed cam of the upstream cam pair (46) and the fixed cam of the downstream cam pair (47) are shrunk to the drive shaft (40, 50).

6. Assembly of shafts according to any one of the preceding claims wherein each inner face comprises a single ramp and the pivot angle A of the downstream movable cam is equal to 180 degrees.

7. Turbomachine comprising: - a stator (S) comprising a turbine stator portion and a compressor stator portion, - a rotating portion comprising the shaft assembly according to any one of the preceding claims, wherein: • the drive shaft (40, 50) is movable in translation relative to the stator by the axial translation control system, • rotor blades (2, 402) of the turbine (400, 500), movable in rotation relative to the stator (S) and rotationally and axially fixed to the drive shaft (40, 50), • fixed stator blades (6, 406) of the turbine stator portion opposite the rotor blades (2, 402), - a front bearing (Pla) mounted in the compressor stator portion, in which the compressor shaft (414) is mounted in rotation and axially supported, - wherein the control system axially displaces the rotor blades (2,402) movable relative to the fixed stator blades (6, 406) during the rotation of the movable cams.

8. Turbomachine according to the preceding claim, comprising: - a low pressure turbine (400) comprising movable rotor blades (2, 402) and fixed stator blades (6, 406), a low pressure turbine shaft (404) fixed in rotation and axially with the drive shaft (40) and with the rotor blades (2, 402) for coupling them, - a rear bearing (POr) mounted between the drive shaft and the stator (S) for supporting the drive shaft (40), in which the drive shaft (40) is axially movable in translation relative to the bearing (POr).

9. Method (90) of controlling axial play between one end of a turbine rotor element and one end of an element of a

10. turbine stator part by using the shaft assembly according to any one of the preceding claims 1 to 6 by controlling the translation control system, the method comprising the following steps: - Determination (91) of a target distance between a stator element and a rotor turbine element; - Measurement (92) of the distance between the stator element and the rotor element; - Determination (93) of the difference between the target distance and the measured distance; - Pivoting (94), based on the determined gap, of the movable cams so as to reduce the gap determined during the determination step (93), the sum of the distance separating the external faces of the cams of the upstream pair of cams and the distance separating the external faces of the cams of the downstream pair of cams being constant. Method (90) according to the preceding claim wherein the pivoting step (94) comprises the simultaneous pivoting of the movable cam of the upstream cam pair and the movable cam of the downstream cam pair.