Torque transmission shaft for an aircraft turbomachine

Abstract

Torque transmission shaft (10) for a turbomachine, in particular for an aircraft, the shaft (10) comprising a tubular body (12) and a clearance compensation ring (18) at at least one of the longitudinal ends (12a, 12b) of the body (12).

Description

[0001] DESCRIPTION

[0002] TITLE: TORQUE DRIVE SHAFT FOR AN AIRCRAFT TURBOMACHINE

[0003] Technical field of the invention

[0004] The invention relates in particular to a torque transmission shaft for a turbomachine, in particular for aircraft, as well as a turbomachine comprising such a shaft.

[0005] Technical background

[0006] The state of the art includes, in particular, documents FR-A1-3 124541 and FRAI-3 123375, EP 3927989 B1, US 7736083 B2, and US 2024 / 209775 A1. As is well known, an aircraft turbomachine extends along a longitudinal axis and comprises, from upstream to downstream in the direction of gas flow, a fan, at least one compressor, an annular combustion chamber, at least one turbine, and finally a combustion gas exhaust nozzle. In the case of a twin-spool turbomachine, with low-pressure and high-pressure components respectively, the turbomachine comprises, between the fan and the nozzle, a low-pressure compressor, a high-pressure compressor, the combustion chamber, a high-pressure turbine, and a low-pressure turbine.

[0007] The high-pressure unit includes a high-pressure shaft that connects the high-pressure compressor rotor to the high-pressure turbine rotor. This high-pressure shaft is tubular and axially traversed by the low-pressure shaft of the low-pressure unit. This low-pressure shaft connects the low-pressure compressor rotor to the low-pressure turbine rotor and is further connected, either directly or via a mechanical gearbox, to the blower shaft.

[0008] In order to explore hybridization solutions, it is known to equip a turbomachine with one or more electric machines. In this application, an electric machine is defined as, for example, a motor, a generator, or a motor / generator combination.

[0009] An electric machine can, for example, be mounted on an accessory or gear box, commonly called an AGB (which is the acronym for Accessory Gear Box), and can draw power from one of the turbomachine shafts, or inject power into one of these shafts, via a radial shaft.

[0010] An electric machine can also be mounted at one end of a shaft and be directly coupled to that shaft, which must ensure a transmission of torque.

[0011] A torque transmission shaft commonly uses splines for connecting shafts to each other and gears with pinions for transmitting power from one shaft line to another. These transmissions have some backlash (reference J in Figure 1) which is due to the assembly requirements (since it is practically impossible to mount splines or pinions with zero backlash) on the one hand, and to manufacturing tolerances on the other.

[0012] At each engine start, and particularly at each change in power delivery / injection phases by the high-speed electric generator / motor of the turbomachine, the transmission chain's torque is restored with changes in the contact points (especially changes in the tooth flanks). These changes often cause torque oscillations and can contribute to wear at the contact points, particularly damaging the teeth due to the shocks they endure. This phenomenon can occur more frequently in the drive systems of certain equipment that do not operate continuously.

[0013] In the current state of the art, this phenomenon is taken into account and has little impact on the lifespan of the transmission chain because it occurs at relatively low speeds and power levels. Gear standards recommend considering dynamic factors in calculations, leading to larger gear teeth to withstand shocks.

[0014] The phenomenon becomes much more important when a driven piece of equipment can also be a motor (like an electric machine).

[0015] Reversing the direction of the torque initially causes a sudden and often abrupt correction, as this occurs with a very low torque. After the play is eliminated, contact with the opposite side results in an impact that will have several consequences:

[0016] - the resulting torque is greater than the nominal torque to be transmitted: therefore, the transmission chain must be oversized for high power levels.

[0017] - Contact on the opposite side generates a shock whose frequency content systematically includes the natural frequencies of the transmission chain. This phenomenon therefore generates an oscillation that could be amplified by the engine control. In some cases, this equipment will need to be oversized to account for this torque demand. Alternatively, the control system will need to incorporate specific processing at the expense of engine operability.

[0018] - a number of high-speed power injection cycles of the turbomachine much greater than the single case of starting.

[0019] For applications with torque direction reversal, the presence of play in the transmission components therefore leads to unfavorable vibration behavior in torsion, oversizing of the torque generator and transmission chain, and increased complexity of engine control.

[0020] Therefore, there is a need for a technology that allows for preloading the drive components and thus limiting the dynamic amplification of the torque to be transmitted. There is also a need to minimize the shock associated with the change in the point of contact, even if the preload is reduced (to avoid oversizing these components).

[0021] The invention provides a simple, efficient and economical solution to at least some of these needs.

[0022] Summary of the invention

[0023] To this end, the invention proposes a torque transmission shaft for a turbomachine, in particular for aircraft, the shaft comprising a tubular body which has an elongated shape along an axis and which includes at a first longitudinal end first external splines, characterized in that it further comprises a first backlash compensation ring at said first longitudinal end of the body, the first ring being centered on the axis and rotationally fixed to the body, the first ring comprising a first axial part which is located inside the first longitudinal end of the body, and a second axial part which is located outside the body and which includes external backlash compensation splines located next to the splines of the first longitudinal end and located at the same diameter as these splines,the first ring further comprising an annular row of blades which are distributed around the axis and which each extend along the axis from the backlash compensation splines to the interior of the body, the blades being elastically deformable by bending and being configured to adopt a first rest position in which the backlash compensation splines are angularly offset by a predetermined angle from the splines of the first longitudinal end, and a second deformed position in which the backlash compensation splines are axially aligned with the splines of the first longitudinal end.

[0024] Preferably, the tubular body comprises at a second longitudinal end external splines, the shaft further comprising a second backlash compensation ring at said second longitudinal end of the body, the second ring being centered on the axis and rotationally fixed to the body, the second ring having a first axial part which is located inside the second longitudinal end of the body, and a second axial part which is located outside the body and which comprises external backlash compensation splines located next to the splines of the second longitudinal end and situated at the same diameter as these splines, the second ring further comprising an annular row of blades which are distributed around the axis and which each extend along the axis from the backlash compensation splines to the inside of the body,the blades being elastically deformable by bending and being configured to adopt a first rest position in which the play-compensating grooves are angularly offset by a predetermined angle from the grooves of the second longitudinal end, and a second deformed position in which the play-compensating grooves are axially aligned with the grooves of the second longitudinal end.

[0025] Backlash compensation splines (or counter-splines) compensate for mounting clearances between the external splines of the shaft and the internal splines of another component to which the shaft is coupled. The blades act as deformable springs, each bending in a circumferential direction around the shaft. This allows the backlash compensation splines to move around the axis, relative to the splines of the shaft body, and provides a certain preload on these backlash compensation splines against the internal splines of the component. The aforementioned angular offset angle and the geometry of the blades are advantageously determined so that the mounting torque corresponds to the desired preload. The preload torque can be chosen to exceed the potential variations in the control signal (for example, the maximum amplitude of torque variation in a motor operating at a steady speed).However, this preload could also be lower when the preload level would lead to an unacceptable oversizing of the splines. In this case, the shock / oscillation limiting effect would be less pronounced but still significant. The choice of blade geometry, which determines their stiffness, will be made according to the desired preload. The load torque will then be, for example, a direct function of the angle and the width / length / thickness of the flexible blades. These parameters can therefore allow the thickness, length, and width of the flexible zone to be adapted according to the need, which is determined by the angular clearance and the amplitude of the oscillations in the torsional natural mode (the lowest frequencies) of the mechanical transmission chain.

[0026] The shaft could be, for example, a rotor shaft of an electric machine, and it is the splined connection between one end of this rotor shaft and a transmission shaft that is fitted with a backlash compensation ring. The shaft (rotor or transmission) may have external splines at both of its longitudinal ends, but only one end may have backlash compensation splines.

[0027] The torque transmission shaft according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0028] - where each ring is rotationally secured to the body by means of the blades, and in particular the longitudinal ends of the blades opposite the play-compensating grooves of the ring,

[0029] - The body and the ring(s) are formed from a single piece using additive manufacturing.

[0030] - The body and the ring(s) are made of the same material and form a single unit, the blades being welded to the body.

[0031] - where each ring is attached inside the body and is configured to cooperate through complementary shapes with the body's interior in order to secure the ring to the body,

[0032] - the blades have a generally wavy or S-shaped form at rest, - the backlash compensation grooves of each ring are separated by an axial play from the grooves of the corresponding longitudinal end of the body,

[0033] - at least part of the ring(s) is separated from the body by a radial clearance,

[0034] - the backlash compensation splines of each ring are shorter than the splines of the corresponding longitudinal end of the body,

[0035] - the play-compensating grooves of the or each ring are domed, - the play-compensating grooves of the or each ring, or even the first and second grooves of the body, have axial ends of convex rounded shape;

[0036] -- the number of blades is at least two;

[0037] -- the bending takes place in the circumferential direction.

[0038] The present invention also relates to a turbomachine, in particular for aircraft, comprising at least one torque transmission shaft as described above.

[0039] The turbomachine preferably includes at least one electric machine connected to a torque transmission chain, one rotor of which includes internal splines in which the backlash compensation splines and the external splines of one of the longitudinal ends of the torque transmission shaft are engaged.

[0040] The backlash compensation ring can also be installed on another component of the torque transmission chain, such as the radial shaft. Therefore, it is not necessarily installed directly on the rotor of the electric machine.

[0041] The turbomachine according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0042] - the turbomachine comprises a drive shaft and an accessory box connected to the drive shaft by a radial shaft, the accessory box being equipped with the transmission shaft which extends inside a casing of the accessory box coaxially to a shaft line, and the electric machine being mounted on the accessory box.

[0043] - the turbomachine includes a drive system comprising the accessory gearbox, a first right-angle gearbox connecting the radial shaft to the drive shaft and a second right-angle gearbox connecting the accessory gearbox to the radial shaft.

[0044] - the radial shaft comprises a first shaft element and a second shaft element connected together via an intermediate bearing.

[0045] - a transfer shaft connects the accessory box to the second angle gearbox.

[0046] - the drive shaft forms the first shaft element, and / or the second shaft element and / or the transfer shaft.

[0047] - the turbomachine includes a turbine shaft extending along a longitudinal axis to a rear end, the rotor of the electric machine being connected to the turbine shaft via the transmission shaft.

[0048] Brief description of the figures

[0049] Other features and advantages will become apparent from the following description of a non-limiting embodiment of the invention with reference to the accompanying drawings in which:

[0050] Figure 1 is a partial schematic cross-sectional view of a splined coupling between two elements of a turbomachine.

[0051] Figure 2 is a schematic half-view in axial cross-section of a torque transmission shaft according to the invention.

[0052] Figure 3 is a schematic top view of one end of the tree in Figure 2;

[0053] Figure 4 is a schematic view of an example of a driveshaft installation in an accessory box; Figure 5 is a schematic view of an example of a driveshaft installation at the rear of a turbomachine, connecting an electric machine to a turbine shaft; and

[0054] Figure 6 is a schematic view of the installation of a drive shaft between angle gearboxes or between an angle gearbox and an accessory gearbox for the transmission of power from a turbomachine drive shaft.

[0055] Detailed description of the invention

[0056] Figure 1 has already been described above.

[0057] Figures 2 and 3 show an embodiment of a torque transmission shaft 10 for a turbomachine, particularly for aircraft. The shaft 10 comprises a tubular body 12 which has an elongated shape along an axis X and which includes at a first longitudinal end 12a first external splines 14, and optionally at a second longitudinal end 12b second external splines 16.

[0058] The shaft 10 further includes a backlash compensation ring 18 at at least one of the longitudinal ends 12a, 12b of the body 12, and in the example shown at each of the longitudinal ends 12a, 12b of the body 12. Each ring 18 is centered on the X-axis and rotationally fixed to the body 12. Each ring 18 has a first axial portion 18a which is located inside the corresponding longitudinal end 12a, 12b of the body 12, and a second axial portion 18b which is located outside the body 12. The second axial portion 18b of each ring 18 includes external backlash compensation splines 20 located next to the splines 14, 16 of the corresponding longitudinal end 12a, 12b and situated at the same diameter D as these splines 14, 16.

[0059] Each ring 18 further comprises an annular row of at least two blades 22 which are distributed around the X axis and which each extend along the X axis from the backlash compensation grooves 20 to the inside of the body 12.

[0060] The blades 22 are elastically deformable, particularly in bending in a circumferential direction of the shaft, and are configured to adopt a first rest position, shown in Figure 3, in which the backlash compensation splines 20 are angularly offset by a predetermined angle a from the splines 14, 16 of the corresponding longitudinal end 12a, 12b.

[0061] The blades 22 are configured to adopt a second deformed position in which the backlash compensation grooves 20 are axially aligned with the grooves 14, 16 of the corresponding longitudinal end 12a, 12b.

[0062] It is therefore understood that the grooves 20 make it possible to take up the play J illustrated in figure 1 between the grooves 14, 16 of the body 12 and the internal grooves 24 of the element in which the end 12, 12b of the body 12 will be engaged.

[0063] A suitable mounting tool (not shown) can be used to engage the splines 20, 14, or the splines 20, 16, into the splines 24. This tool allows the blades 22 to be deformed from their first position to their second position, so that the splines 20, 14 or the splines 20, 16 are axially aligned. The splines 20, 14 (or 20, 16) are then engaged in the splines 24, and the blades 22 are released. By elastic return, these blades 22 assume a position in which the splines 20 take up the play J by bearing against the flanks of the splines 24. The opposite flanks of the splines 24 bear against the splines 14 (or 16). The position adopted by the splines 20 is an intermediate position between the two positions mentioned above.

[0064] Each ring 18 is preferably rotationally secured to the body 12 by means of the blades 22, and in particular the longitudinal ends of the blades 22 opposite the grooves 20. The body 12 and the rings 18 can be formed in one piece by additive manufacturing.

[0065] Alternatively, the body 12 and the rings 18 could be made of the same material and could form a single unit. The blades 22 would then preferably be welded to the body 12, in particular at their longitudinal ends opposite the grooves 20.

[0066] In yet another variant, the rings 18 are attached inside the body 12 and are configured to cooperate by complementary shapes with the interior of the body 12 in order to secure the rings 18 to the body 12. Projecting features, such as ribs, or recessed features, could then be formed inside the body 12 to accommodate the ends of the blades 22 and cooperate with them by complementary shapes. A layer of elastomer could be provided between the ends of the blades 22 and the projecting features to prevent wear of the blades by friction against these projecting features.

[0067] As can be seen in the drawings, the blades 22 can have a generally wavy or S-shaped form at rest.

[0068] The backlash compensation splines 20 of each ring 18 are preferably separated by an axial clearance H1 from the splines 14, 16 of the corresponding longitudinal end 12a, 12b of the body 12.

[0069] At least a part of each ring 18 can be separated by a radial clearance H2 from the body 12.

[0070] The H1, H2 set or sets facilitates the movement of the ring 18 relative to the body 12.

[0071] As in the example shown, the backlash compensation splines 20 of each ring 18 may have a length L1 less than the length L2 of the splines 14, 16 of the corresponding longitudinal end 12a, 12b of the body 12.

[0072] The backlash compensation splines 20 of each ring 18 may be convex. The splines 14, 16 may also be convex. The backlash compensation splines 20 of each ring 18, and even the splines 14, 16 of the body 12, may have convex rounded axial ends, as can be seen in Figure 3.

[0073] The present invention also relates to a turbomachine, particularly for aircraft, comprising at least one torque transmission shaft 10 as described above. Different mounting configurations of the shaft 10 are illustrated in Figures 2 and 4 to 6.

[0074] The turbomachine includes, for example, an electric machine 30 (shown in dashed lines in Figure 2) coupled to the shaft 10 directly or via another component of the torque transmission chain. The machine 30 may include a rotor 30a (see Figures 1 and 2) having internal splines of the type shown in Figure 1 (reference 24), in which the backlash compensation splines 20 and the external splines 14, 16 of one of the longitudinal ends 12a, 12b of the shaft 10 are engaged.

[0075] According to an embodiment shown in Figure 4, the transmission shaft 10 can be fitted to an accessory gearbox 50 (known by the English acronym "AGB" for "Accessory Gear Box") of the turbomachine. At least one electric machine 30 can be mounted on the accessory gearbox 50 and connected to the shaft 10. Preferably, the electric machine 30 is mounted outside the accessory gearbox 50.

[0076] The accessory box 50 includes, for example, a housing 52 inside which extends the transmission shaft 10. The X-axis of the transmission shaft can be coaxial with a shaft line L50 of the accessory box 50. The shaft line L50 can be dedicated not only to the electric machine 30 but also to a manual control port HOP 72 (known as the "Hand Crank Port") mounted externally on the wall 52b of the housing 52 opposite the electric machine 30.

[0077] The electric machine 30 includes a rotor 30a which can be coupled to one of the longitudinal ends 12a, 12b of the transmission shaft 10. In particular, the rotor 30a includes internal splines 24 which engage with the backlash-compensating splines 20 and the external splines 14, 16 of one of the longitudinal ends 12a, 12b of the shaft 10.

[0078] A pinion 56 comprising a pinion shaft 56a can extend between the two opposing walls 52a and 52b of the housing 52. The walls 52a, 52b are arranged in a non-limiting manner perpendicular to the shaft line L50. The electric machine 30 is, for example, mounted on the side of wall 52a. The pinion shaft 56a extends radially outside the shaft 10. The pinion shaft 56a includes, for example, teeth 56b1 allowing it to mesh with other gear elements such as pinions 58, 60 also arranged inside the housing 52 of the accessory gearbox. The axis of each pinion 58, 60 is shown parallel to the axis of the shaft 10. These pinions 58, 60 can be used to drive other accessories and / or equipment 70, mounted on the accessory box 50.

[0079] According to this embodiment, the manual control port HCP 72 is mounted externally on the wall 52b of the housing 52 opposite the electric machine 30. The control port is, for example, centered on the axis of the shaft 10 and is configured to interface, on command, with the internal gear system of the housing and to allow, on command, manual drive of this system. This manual control port 72 is used only when the aircraft is on the ground, during maintenance operations.

[0080] The shaft 10 may have a frangible section (mechanical fuse). The frangible section is advantageously, but not exclusively, located on the tubular body 12, and preferably in the middle of its length (measured between the ends 12a and 12b).

[0081] According to another embodiment illustrated in Figure 5, the transmission shaft 10 is connected to a turbine shaft 1 of the turbomachine. The turbine shaft 1 extends along a longitudinal axis A of the turbomachine (defining a central axis thereof) to a rear end of the turbomachine. The turbine shaft 1 can be supported by various bearings, including, for example, a rear roller bearing 3. The transmission shaft 10 is centered on the turbine shaft 1 and extends rearward from the turbine shaft 1. The turbine shaft 1 includes internal splines 24a that extend radially inward. The internal splines 24a engage with, for example, the backlash compensation splines 20 and the external splines 14, 16 of one of the longitudinal ends 12a, 12b of the shaft 10, and here of end 12a. Such a configuration allows for easy assembly and disassembly (for example for maintenance) of the shaft 10.Furthermore, the splined coupling allows for "free" translation of the shafts within each other. Thrust elements are provided, for example, to limit the displacement and / or stabilize the axial operation of shaft 10. Thrust elements are, for example, a nut and / or a removable ring at one downstream end of shaft 8, which helps to stabilize shaft 10 during operation.

[0082] As illustrated, an electric machine 30 is, for example, mounted at the rear of the turbomachine and preferably on an exhaust housing 6. The electric machine 30 advantageously comprises a rotor 30a driven in rotation by the turbine shaft via the transmission shaft 10. For this purpose, the rotor 30a of the electric machine 30 includes a shaft 8 concentric with the shaft 10. The shaft 8 includes, for example, internal splines 24b that extend radially inwards. The internal splines 24b engage with, for example, the backlash compensation splines 20 and the external splines 14, 16 of one of the longitudinal ends 12a, 12b of the shaft 10, and here of the end 12b.

[0083] Advantageously, the shaft 8 is also concentric with a cylindrical bearing 9 of the exhaust housing 6 and is connected to it by two rolling bearings 5a, 5b (for example cylindrical rollers).

[0084] The electric machine 30 further includes a stator 30b which can be attached to the exhaust housing 6 by a bolted flange 7. Figure 6 illustrates another embodiment of the arrangement of the transmission shaft 10 in a turbomachine. The turbomachine shown is a twin-spool, twin-spool turbojet engine. The turbomachine includes, for example, a drive shaft 11 from which power is extracted or injected. The extracted power can, for example, supply accessories and / or equipment of the turbomachine and / or the aircraft. The drive shaft 11 can be the high-pressure shaft.

[0085] The turbomachine can be equipped for this purpose with a drive system 90 known by the Anglo-Saxon acronym "ADT" for "Accessory Drive Train". The drive system 90 can include at least one of the following components: an accessory gearbox 50 and a right-angle gearbox 91 (known by the Anglo-Saxon acronym "TGB" for "Transfer Gear Box" or "IGB" for "Inlet Gear Box", depending on its location in the drive system 90).

[0086] In Figure 6, a radial shaft 100 connects the accessory gearbox 50 to the turbomachine's drive shaft. The radial shaft 100 is advantageously mounted in a radial arm 92 of the turbomachine. The radial arm 92 passes, for example, through a secondary flow V2 of the turbomachine.

[0087] An intermediate bearing 110 supports the radial shaft 100 between its two radial ends. One radial end of the radial shaft 100 is coupled to the drive shaft 11 by a first right-angle gearbox 91a (IGB) and a second end is coupled to the accessory gearbox 50 by a second right-angle gearbox 91b (TGB).

[0088] The intermediate bearing 110 may include a plurality of bearings (not shown) mounted in housings and known to those skilled in the art. The bearings support the radial shaft 100 and facilitate its rotation.

[0089] In the illustrated example, the radial shaft 100 comprises a first shaft element 101 and a second shaft element 102 which are connected together, for example, via the intermediate bearing 110. The drive system 90 includes, but is not limited to, a transfer shaft 103 known by the Anglo-Saxon acronym "TDS" for "Transfer Drive Shaft" which allows the angle gearbox 91b to be connected to the accessory gearbox 50. The transfer shaft 103 advantageously extends along an axis parallel to the longitudinal axis A of the turbomachine.

[0090] The transmission shaft 10 as described above can be advantageously used for the first shaft element 101, the second shaft element 102, and / or the transfer shaft 103.

[0091] Advantageously, the accessory box 50 of this embodiment can also have the transmission shaft 10 according to the configuration shown in the embodiment of Figure 4.

[0092] When the transfer shaft 103 has the characteristics of the shaft 10 described previously, the parts with internal splines can be the shafts (hollow shafts) of the gears to which the transfer shaft 103 connects. Typically, a bevel gear can be provided in the right-angle gearbox 91b TGB and a spur gear can be provided in the accessory gearbox 50(AGB). Alternatively, the transfer shaft 103 can have at least backlash-compensating external splines 20 at only one of its two ends, although it is generally preferable for both ends to have them: this limits the impact between splines when the direction of torque is reversed (load -> motor). The transfer shaft 103 also includes external splines 14, 16.

[0093] Regarding the radial shaft 100 formed by the first shaft element 101 and the second shaft element 102, backlash compensation splines 20 may be provided at one of their ends. In other words, each end of a shaft element 101, 102 will preferably be a male part intended to connect to a female part formed by:

[0094] - a pinion shaft of the first internal angle gearbox (IGB) or of the second angle gearbox (TGB), or - a female connecting part of the other shaft element 101, 102, in the case where there are two shaft elements 101, 102 which connect at the level of an intermediate bearing 110.

[0095] Radial trees typically have, but are not limited to, a male end and a female end.

[0096] Alternatively, a radial shaft 100 formed from a single piece can have one end fitted with a male portion having at least 20 external splines for backlash compensation. The male portion of the radial shaft 100 is connected (via a gear, for example) to the second right-angle gearbox (TGB) to transmit power. The first internal right-angle gearbox (IGB) includes, for example, a gear with external splines to connect to the female end of the radial shaft 100, which has corresponding splines.

Claims

DEMANDS 1. A torque transmission shaft (10) for a turbomachine, particularly for aircraft, the shaft (10) comprising a tubular body (12) having an elongated shape along an axis (X) and comprising at a first longitudinal end (12a) first external splines (14), characterized in that it further comprises a first backlash compensation ring (18) at said first longitudinal end (12a) of the body (12), the first ring (18) being centered on the axis (X) and rotationally fixed to the body (12), the first ring (18) comprising a first axial portion (18a) located inside the first longitudinal end (12a) of the body (12), and a second axial portion (18b) located outside the body (12) and comprising external backlash compensation splines (20) situated next to the splines (14, 16) of the first longitudinal end (12a) and located at the same diameter (D) as these grooves (14, 16),the first ring (18) further comprising an annular row of blades (22) which are distributed around the axis (X) and which each extend along the axis (X) from the external backlash compensation splines (20) to the interior of the body (12), the blades (22) being elastically deformable by bending and being configured to adopt a first rest position in which the external backlash compensation splines (20) are angularly offset by a predetermined angle (a) from the splines (14, 16) of the first longitudinal end (12a), and a second deformed position in which the external backlash compensation splines (20) are axially aligned with the splines (14, 16) of the first longitudinal end (12a).

2. Torque transmission shaft (10) according to claim 1, in which the tubular body (12) comprises at a second longitudinal end (12b) external second splines (14), the shaft (10) further comprising a second backlash compensation ring (18) at said second longitudinal end (12b) of the body (12), the second ring (18) being centered on the axis (X) and rotationally fixed to the body (12), the second ring (18) having a first axial portion (18a) which is located inside the second longitudinal end (12b) of the body (12), and a second axial portion (18b) which is located outside the body (12) and which comprises external backlash compensation splines (20) located next to the splines (14, 16) of the second longitudinal end (12b) and located at the same diameter (D) as these splines. (14, 16),the second ring (18) further comprising an annular row of blades (22) which are distributed around the axis (X) and which each extend along the axis (X) from the external backlash compensation splines (20) to the interior of the body (12), the blades (22) being elastically deformable by bending and being configured to adopt a first rest position in which the external backlash compensation splines (20) are angularly offset by a predetermined angle (a) from the splines (14, 16) of the second longitudinal end (12b), and a second deformed position in which the external backlash compensation splines (20) are axially aligned with the splines (14, 16) of the second longitudinal end (12b).

3. Torque transmission shaft (10) according to claim 1 or 2, in which the ring or each ring (18) is rotationally fixed to the body (12) by means of the blades (22), and in particular the longitudinal ends of the blades (22) opposite the external grooves (20) for compensating for ring backlash.

4. Torque transmission shaft (10) according to any one of claims 1 to 3, wherein the body (12) and the ring(s) (18) are formed in one piece by additive manufacturing.

5. Torque transmission shaft (10) according to any one of claims 1 to 3, wherein the body (12) and the ring(s) (18) are made of the same material and form a single unit, the blades (22) being welded to the body (12).

6. Torque transmission shaft (10) according to any one of claims 1 to 3, wherein the ring or each ring(s) (18) is brought inside the body (12) and is configured to cooperate by complementary shapes with the inside of the body (12) in order to secure the ring (18) to the body (12).

7. Torque transmission shaft (10) according to any one of the preceding claims, wherein the blades (22) have at rest a generally wavy or S-shaped form.

8. Torque transmission shaft (10) according to any one of the preceding claims, wherein the external backlash compensation splines (20) of the or each ring (18) are separated by an axial clearance (H1) from the splines (14, 16) of the corresponding longitudinal end (12a, 12b) of the body (12).

9. Torque transmission shaft (10) according to any one of the preceding claims, wherein at least a portion of the or each ring (18) is separated by a radial clearance (H2) from the body (12).

10. Torque transmission shaft (10) according to any one of the preceding claims, wherein the external backlash compensation splines (20) of the or each ring (18) have a length (L1) less than that (L2) of the splines (14, 16) of the corresponding longitudinal end (12a, 12b) of the body (12).

11. Torque transmission shaft (10) according to any one of the preceding claims, in which the external backlash compensation splines (20) of the or each ring (18) are domed.

12. A torque transmission shaft (10) according to any one of the preceding claims, wherein the external backlash compensation splines (20) of the ring (18), or even the first and second splines (14, 16) of the body (12), have convex rounded axial ends.

13. A turbomachine, particularly for aircraft, comprising at least one torque transmission shaft (10) according to any one of the preceding claims.

14. Turbomachine according to the preceding claim, comprising at least one electric machine (30) connected to a torque transmission chain of which a rotor (30a) includes internal splines (24) in which are engaged the external backlash compensation splines (20) and the external splines (14, 16) of one of the longitudinal ends (12a, 12b) of the torque transmission shaft (10).

15. Turbomachine according to any one of claims 13 and 14, comprising a drive shaft (11) and an accessory box (50) connected to the drive shaft (11) by a radial shaft (100), the accessory box (50) being equipped with the transmission shaft (10) which extends inside a housing (52) of the accessory box (50) coaxially to a shaft line (L50), and the electric machine (30) being mounted on the accessory box (50).

16. Turbomachine according to the preceding claim, comprising a drive system (90) including the accessory box (50), a first right-angle gearbox (91a) connecting the radial shaft (100) to the drive shaft (11) and a second right-angle gearbox (91b) connecting the accessory box to the radial shaft (100).

17. Turbomachine according to any one of claims 15 and 16, wherein the radial shaft (100) comprises a first shaft element (101) and a second shaft element (102) connected together via an intermediate bearing (110).

18. Turbomachine according to any one of claims 16 and 17, wherein a transfer shaft (103) connects the accessory box to the second angle gearbox (91b).

19. Turbomachine according to any one of claims 17 and 18, wherein the transmission shaft (10) forms the first shaft element (101), and / or the second shaft element (102) and / or the transfer shaft (103).

20. Turbomachine according to claim 14, comprising a turbine shaft (1) extending along a longitudinal axis (A) to a rear end, the rotor (30a) of the electric machine (30) being connected to the turbine shaft (1) via the transmission shaft (10).

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