GEAR FOR AN AIRCRAFT TURBOMACHINE

Abstract

A gear (5) for an aircraft turbomachine, the gear (5) comprising a shaft (6) of revolution about an axis (X) and a toothed disc (7) having external teeth (8), the shaft (6) and the disc (7) being rotationally linked via a splined joint (9), the external teeth (8) and / or the splined joint (9) being configured to at least partially transform the torsional vibratory stresses exerted on the teeth (8) of the disc (7) into an axial displacement of the disc (7), characterized in that the gear (5) comprises two axial dampers (10) disposed on either side of the disc (7), the dampers (10) each being annular about the axis (X), each damper (10) having a first axial end (11) integral with the shaft (6) and a second axial end (12) integral with the disc (7), in such a way to axially dampen the toothed web (7) against the torsional vibrational stresses it undergoes. Figure for the abbreviated version: Figure 1

Description

Title of the invention: GEAR WHEEL FOR AN AIRCRAFT TURBOMACHINE Technical field of the invention

[0001] The present invention relates to a gear wheel for an aircraft turbomachine, as well as to an assembly comprising such a gear wheel. Technical background

[0002] A turbomachine generally comprises various gear trains which allow the transmission (reversibly or not) of mechanical power taken from one or more driving devices to one or more receiving devices.

[0003] Such a gear train classically comprises a plurality (or cascade) of gear wheels which are meshed with each other.

[0004] Such a gear train is found for example in an accessory box of the turbomachine, and allows the power taken from the thermal engine of the turbomachine to be transmitted to the various accessories (pumps, electric machines, oil separator, starter, etc.) of the turbomachine, or vice versa.

[0005] To reduce fuel consumption and noise emissions, engine manufacturers are moving towards hybridizing turbomachinery by developing, in particular, hybrid electric architectures.

[0006] For this purpose, one or more electric machines are, for example, mounted on the accessory housing and coupled to the latter's gear train. The electric machine(s) are each configured to operate in so-called motor and generator modes.

[0007] An electric machine operating in motor mode injects (or introduces) mechanical power onto the gear train to supplement or complement the internal combustion engine.

[0008] Conversely, an electric machine operating in generator mode takes mechanical power from the gear train to generate electrical power which can be stored for example in batteries.

[0009] The addition of one or more electric machines puts more stress on the various gear wheels of the gear train, due in particular to the numerous variations and reversals of torque.

[0010] Engine manufacturers note that variations and reversals of torque cause repeated vibrational stresses (or excitations) in torsion (particularly at low frequencies) which must be addressed to optimize wheel life toothed. Vibrational stresses in torsion generally result in the presence of torque oscillations.

[0011] In addition to this, the low-frequency torsional natural modes can be excited (spotentially or continuously) by unanticipated vibrational sources (for example, an accessory), so it is important to take these torsional vibrational stresses into consideration.

[0012] To dampen these torsional vibration stresses, it is known to integrate elastomer dampers. However, such dampers have a reduced lifespan and are therefore not really suitable for an aeronautical application requiring optimized reliability in determining lifespans and / or optimized maintenance operations.

[0013] It is also known to integrate one or more radial or tangential dampers into a toothed wheel. However, such dampers can be improved, particularly due to their efficiency and the complexity of their assembly.

[0014] Engine manufacturers note that to avoid these torsional vibration stresses, it might be advantageous to shift the low-frequency torsional natural modes towards higher frequencies. However, such a shift is not easy to implement and is generally achieved at the cost of a significant increase in mass (increased inertia and / or torsional stiffness).

[0015] The objective of the present invention is therefore to provide a simple, effective and economical solution to the aforementioned problem. Summary of the invention

[0016] The invention thus proposes a gear for an aircraft turbomachine, the gear comprising a shaft of revolution about an axis X and a toothed web which has external teeth, the shaft and the web being linked in rotation via a splined connection, the external teeth and / or the splined connection being configured to transform at least partially the torsional vibratory stresses which are exerted on the teeth of the web into an axial displacement of the web, characterized in that the gear comprises two axial dampers disposed on either side of the web, the dampers being each annular about the axis X, each damper having a first axial end fixed to the shaft and a second axial end fixed to the web, so as to axially dampen the toothed web with respect to the torsional vibratory stresses which it undergoes.

[0017] The two axial dampers make it possible to effectively dampen the torsional vibration stresses, and in other words to significantly reduce their intensity, so as to generally maximize the life of the gear.

[0018] Compared to radial or tangential shock absorbers (prior art), axial shock absorbers have a larger installation space, which allows for the installation of larger shock absorbers when necessary, but also facilitates assembly.

[0019] The axial arrangement of the shock absorbers also offers the possibility of integrating viscous damping (and in particular oil damping), in order to increase the damping capacity of the shock absorbers (by complementing, for example, mechanical damping) and / or limit the size of the shock absorbers.

[0020] Such a damping solution can be applied to any gear in the gear train, depending on the requirements.

[0021] Such a damping solution proves to be effective not only on the gear itself, but also on the gear train in which the gear is installed.

[0022] The integration of the damping into the gear does not entail any modification of the structure (for example of the accessory housing) which houses the gear.

[0023] The gear according to the invention may comprise one or more of the following features and / or steps, taken individually or in combination with each other: - each shock absorber includes an elastic damping element which is annular around the X axis and which is capable of deforming axially in an elastic manner; - the elastic element is either a coiled spring or a Belleville washer; - each shock absorber includes an oil inlet through which a shock absorber damping oil bath is supplied, and an oil outlet through which excess oil is expelled from the bath; - the oil inlet is formed in the barrel and at the inner periphery of the shock absorber, and the oil outlet is formed at the outer periphery of the shock absorber; - each shock absorber comprises a male part and a female part, the male part cooperating by complementary shape with the female part; - the male part is attached to the veil and the female part is attached to the shaft; - the male part is fretted onto the veil and the female part is fretted onto the body; - the external teeth and the grooved connection are defined according to one of the following pairs: — the external teeth are helical and the grooved connection is helical; — the external teeth are helical and the grooved connection is straight; — the external teeth are straight and the grooved connection is helical; — the external teeth are spiroconic and the grooved joint is straight.

[0024] The present invention also relates to an assembly for an aircraft turbomachine comprising a fixed structure and a gear as described Previously, the shaft of the gear was guided in rotation relative to the structure via two roller bearings arranged on either side of the toothed web. Brief description of the figures

[0025] The invention will be better understood and other details, features and advantages of the invention will become more apparent upon reading the following description, given by way of non-limiting example and with reference to the accompanying drawings in which:

[0026] [Fig-1] [Fig.1] is a schematic axial half-section view of a gear according to a first embodiment;

[0027] [Fig.2] [Fig.2] is a detailed view of [Fig.1] which illustrates a variant embodiment of the first embodiment;

[0028] [Fig.3] [Fig.3] is a perspective view of a gear according to a second, more concrete embodiment;

[0029] [Fig.4] [Fig.4] is a half-sectional axial view of the gear illustrated on the [Fig.3];

[0030] [Fig.5] [Fig.5] is an exploded side view of the gear illustrated in Figures 3 and 4;

[0031] [Fig.6] [Fig.6] is a detailed perspective view showing only the shaft and toothed veil of the gear illustrated in figures 3 to 5. Detailed description of the invention

[0032] Figure [Fig.1] shows a partial and schematic representation of an accessory housing 1 of an aircraft turbomachine 2.

[0033] The aircraft is for example an airplane or a drone.

[0034] Turbomachine 2 is, for example, an unducted single-fan turbomachine, more commonly known by its English acronym USF. Such a turbomachine comprises a movable, unducted fan and a fixed, unducted rectifier. The fan is mechanically driven by a power turbine, which is itself driven by the hot gases from a gas generator.

[0035] The accessory housing 1 brings together various accessories (pumps, electrical machines, oil separator, starter, etc.) which are necessary for the operation of the turbomachine 2.

[0036] More specifically, the accessory housing 1 includes a fixed housing 3 onto which the various accessories of the turbomachine 2 are attached.

[0037] The various accessories are rotationally linked with the gas generator of the turbomachine 2 via, in particular, a gear train 4 which is housed in the casing 3 of the accessory housing 1.

[0038] The gear train 4 comprises a plurality (or cascade) of gears, one of which, according to the invention, is shown in [Fig. 1]. The various gears The gear train 4 are meshed with each other, so as to transmit the mechanical power taken from the gas generator to the various accessories, or vice versa.

[0039] The gear 5 comprising a shaft 6 of revolution about an axis X and a toothed web 7 which has an external toothing 8. The shaft 6 and the web 7 are connected in rotation via a splined joint 9. The external toothing 8 and / or the splined joint 9 are configured to transform at least partially the vibratory torsional stresses which are exerted on the teeth 8 of the web 7 into an axial displacement of the web 7.

[0040] According to the invention, the toothed wheel 5 comprises two axial dampers 10 arranged on either side of the web 7. The dampers 10 are each annular around the axis X. Each damper 10 has a first axial end 11 fixed to the shaft 6 and a second axial end 12 fixed to the web 7, so as to axially dampen the toothed web 7 with respect to the torsional vibratory stresses it undergoes.

[0041] The two axial dampers 10 make it possible to effectively dampen the torsional vibration stresses, and in other words to significantly reduce their intensity, so as to generally maximize the life of the gear 5.

[0042] Compared to radial or tangential dampers (prior art), axial dampers 10 have a larger installation space, which allows for the installation of larger dampers 10 when necessary, but also facilitates assembly.

[0043] The axial arrangement of the shock absorbers 10 also offers the possibility of integrating viscous damping (and in particular oil damping), in order to increase the damping capacity of the shock absorbers 10 (by supplementing, for example, mechanical damping) and / or limit the size of the shock absorbers 10.

[0044] Such a damping solution can be applied to any gear of the gear train 4, depending on the requirements.

[0045] Such a damping solution proves to be effective not only on the gear wheel 5 itself, but also on the gear train 4 in which the gear wheel 5 is installed.

[0046] The integration of the damping into the gear 5 does not entail any modification of the structure (for example the housing 3 of the accessory housing 1) which accommodates the gear 5.

[0047] The gear 5 is defined along the X axis which corresponds in particular to its axis of rotation.

[0048] By convention in this application, "axial" means any direction parallel to the X-axis of the gear 5, "radial" means any direction perpendicular to the X-axis of the gear 5, and "circumferential" or "tangential" means any direction relative to the circumference of the gear 5 (as opposed to the axial and radial directions explained above).

[0049] Furthermore, by convention in the present application, the terms "internal" and "external" are defined with respect to the X axis of the gear 5.

[0050] Advantageously, in the case of the aforementioned example with the accessory housing 1, the shaft 6 of the gear 5 is guided in rotation relative to the housing 3 via two bearing supports 13 arranged on either side of the toothed disc 7.

[0051] Each bearing 13 comprises inner and outer rings and rolling elements arranged radially between the rings.

[0052] The bearings 13 are determined according to the choices made for the external teeth 8 of the web 7 and the splined connection 9, and in other words according to the forces to be resisted.

[0053] Advantageously, the gear 5 according to the invention is positioned in the gear train 4 as close as possible to the maximum deformations of the most critical torsion mode.

[0054] Advantageously, the axial dampers 10 are attached to the toothed disc 7.

[0055] Advantageously, each shock absorber 10 is located axially between a bearing 13 and the toothed disc 7.

[0056] Advantageously, each shock absorber 10 can have so-called mechanical damping.

[0057] To this end, each damper 10 comprises an elastic damping element 14 which is annular around the axis X and which is capable of axially deforming elastically. Each damper 10 can obviously comprise several elastic elements 14 arranged in series or in parallel.

[0058] An elastic element 14 can be either a coiled spring 14 or a Belleville washer. The Belleville washer can be spiral in shape and have several coils.

[0059] The elastic element(s) 14 can be dimensioned according to several strategies, including: - a first strategy in which the elastic element(s) 14 compress beyond a predetermined torque which is close to the maximum operating torque; - a second strategy in which the elastic element(s) 14 compress beyond a predetermined torque which is well below the maximum operating torque.

[0060] The first strategy aims more specifically at mitigating over-torques which could be destructive to the gear 5.

[0061] The second strategy aims to mitigate oscillatory torques over the entire operating range of the gear 5. However, such a strategy introduces a transmission error on each torque oscillation around the average torque.

[0062] Each damper 10 may have so-called viscous damping to supplement or complete the mechanical damping (elastic element(s) 14).

[0063] For this purpose, each shock absorber 10 includes an oil inlet 15 through which a damping oil bath 16 of the shock absorber 10 is supplied, and an oil outlet 17 through which excess oil is expelled from the bath 16.

[0064] The addition of viscous damping can increase the capacity damping of a shock absorber 10 and / or to limit the bulk of the elastic element(s) 14 (and consequently to limit the overall bulk of the shock absorber 10).

[0065] Advantageously, the oil inlet 15 is formed in the barrel 6 and at the inner periphery of the shock absorber 10, and the oil outlet 17 is formed at the outer periphery of the shock absorber 10.

[0066] Such an arrangement of the oil inlet 15 allows the oil bath 16 to be supplied via the oil inlet 15 under the effect of centrifugal force. In other words, the oil level in the bath 16 is maintained under the effect of centrifugal force. Similarly, such an arrangement of the oil outlet 17 allows excess oil to be removed under the effect of centrifugal force.

[0067] The oil inlet 15 may include one or more annular rows of radial orifices 18.

[0068] The oil outlet 17 can be formed by a gap 19 (axial or radial) between two parts, one of them being integral with the barrel 6 and the other being integral with the toothed disc 7.

[0069] Advantageously, each shock absorber 10 comprises a damping cavity 20 that is at least partially closed. The damping cavity 20 houses, for example, one or more elastic elements 14 (mechanical damping) and / or the oil bath 16 (viscous damping).

[0070] Each shock absorber 10 can include a male part 21 and a female part 22, the male part 21 cooperating by complementary shape with the female part 22.

[0071] According to a first configuration of the shock absorber 10 (figures 3-6), the male part 21 is integral with the web 7 and the female part 22 is integral with the barrel 6. Alternatively, according to a second configuration (not shown), the male part 21 could be integral with the barrel 6 and the female part 22 could be integral with the web 7.

[0072] According to the first configuration of the damper 10 described above, the male part 21 is shrink-fitted onto the web 7 and the female part 22 is shrink-fitted onto the shaft 6. In addition to shrink-fitting, the female part 22 can be axially fixed on the shaft 6. by a stop ring 39 which is housed in a groove of the barrel 6, the stop ring 39 being disposed on the side of the toothed veil 7.

[0073] Advantageously, the external teeth 8 and the splined connection 9 are defined according to one of the following pairs: - the external teeth 8 are helical and the splined linkage 9 is helical; (first pair) - the external teeth 8 are helical and the splined linkage 9 is straight; (second pair) - the external teeth 8 are straight and the splined linkage 9 is helical; (third pair) - the external teeth 8 are spiral-conical and the grooved linkage 9 is straight, (fourth pair)

[0074] The profile of the teeth (external teeth 8) and / or the grooves (grooved link 9) allows the vibratory stresses in torsion exerted on the teeth 8 of the web 7 to be transformed at least partially into an axial displacement of the web 7.

[0075] The different pairs mentioned above allow the invention to be adapted according to the desired application.

[0076] The grooved connection 9 has a predetermined clearance which allows axial displacement of the web 7 relative to the shaft 6, and depending on the case, rotation around the X axis of the web 7 relative to the shaft 6.

[0077] The first and third couples mentioned above make it possible to efficiently transform the vibratory stresses into torsion which are exerted on the teeth 8 of the web 7 into an axial displacement of the web 7.

[0078] The second couple is easy to produce industrially. The veil 7 moves only in translation (straight splined joint 9) which limits transmission errors.

[0079] The first, second and third pairs mentioned above are associated with ball bearings 13, to take up axial and radial forces.

[0080] The fourth couple mentioned above is associated with a ball bearing 13 and to a roller bearing 13, to take up axial and radial forces.

[0081] According to the embodiments illustrated in the figures, the toothed wheel 5 is mobile in rotation around the axis X.

[0082] The barrel 6 is hollow and open at each of its axial ends.

[0083] The shaft 6 of the toothed wheel 5 is guided in rotation relative to the housing 3 of the casing accessories 1 via two bearing supports 13 arranged on either side of the toothed disc 7.

[0084] More specifically, each bearing 13 comprises an inner ring attached to a bearing surface 43 of the shaft 6, an outer ring placed in a housing 44 of a wall of the casing 3, and rolling elements arranged radially between the rings.

[0085] The toothed veil 7 is annular around the axis X. The toothed veil 7 comprises an internal hub 24 and an external toothing 8 which are connected to each other by a radial web 25.

[0086] The axial shock absorbers 10 are arranged on either side of the web 7, the shock absorbers 10 being attached to the web 7. Each shock absorber 10 is located axially between a bearing 13 and the web 7.

[0087] According to the first embodiment illustrated in [Fig.1], each damper 10 has only mechanical damping.

[0088] More specifically, each shock absorber 10 comprises a coil spring 14 which is annular about the axis X. The spring 14 has an axial end which bears against an external collar 26 of the barrel 6 and an axial end which bears against the hub 24 of the disc 7. The external collar 26 determines an axial stop and constitutes a shoulder.

[0089] Each bearing 13 is stopped axially by a shoulder of the collar 26 of the barrel 6 and by a retaining ring 27 which is housed in a groove of the barrel 6. The retaining ring 27 could include or be replaced by a nut.

[0090] According to the embodiment illustrated in [Fig.2], each damper 10 has mechanical damping and viscous damping.

[0091] More specifically, each shock absorber 10 comprises a coil spring 14 and an oil bath 16 housed in a cavity 20 of the shock absorber 10.

[0092] Each shock absorber 10 includes an annular sleeve 28 attached to the barrel 6.

[0093] The cavity 20 of each shock absorber 10 is annular, and defined by the sleeve 28 and barrel 6.

[0094] The sleeve 28 comprises a radial base 29 and an axial skirt 30 which is located opposite and at a distance from the shaft 6. The base 29 is arranged axially between one of the bearing supports 13 and an external flange 31 of the shaft 6. The external flange 31 constitutes a shoulder.

[0095] The coil spring 14 of each shock absorber 10 is annular around the axis X. The spring 14 has an axial end which is in contact with the base 29 of the sleeve 28 and an axial end which is in contact with the hub 24 of the disc 7.

[0096] The oil bath 16 of each shock absorber 10 is annular around the axis X. The oil bath 16 is formed at the inner periphery of the skirt 30 of the sleeve 28, and is axially delimited by the base 29 and an inner rim 32 of the skirt 30. The height of the inner rim 32 defines the oil height of the bath 16. The surface of the oil bath 16 is shown in dashed lines on [Fig.2].

[0097] The oil inlet 15 comprises an annular row of radial orifices 18. Each radial orifice 18 is open, and connects the interior of the barrel 6 to the cavity 20. The radial orifices 18 thus allow the oil inside the barrel 6 to enter the cavity 20 and supply the bath 16, under the effect of centrifugal force.

[0098] The oil outlet 17 is radial, and formed by a gap 19 which is defined axially between the axial end of the skirt 30 and a free axial end of the hub 24 of the web 7. The gap 19 allows excess oil from the bath 16 to leave the cavity 20, under the effect of centrifugal force.

[0099] The path of the oil in the shock absorber 10 is shown in dotted line on [Fig.2],

[0100] Each bearing 13 is stopped axially by the base 29 of the sleeve 28 and by a retaining ring 27 which is housed in a groove of the barrel 6. The retaining ring 27 could include or be replaced by a nut.

[0101] According to the second embodiment illustrated in figures 3 to 6, each damper 10 has mechanical damping and viscous damping.

[0102] More specifically, each shock absorber 10 comprises a coil spring 14 and an oil bath 16 housed in a cavity 20 of the shock absorber 10.

[0103] Each shock absorber 10 comprises a male part 21 and a female part 22, the male part 21 cooperating by complementarity of form with the female part 22.

[0104] The male part 21 is here integral with the veil 7 and the female part 22 is integral with the shaft 6.

[0105] The cavity 20 of each shock absorber 10 is annular, and jointly defined by the male and female parts 21, 22 as well as the barrel 6.

[0106] The male part 21 is annular and has a right-angled profile in cross-section. The male part 21 thus comprises an axial flange 33 and a radial apron 34. The axial flange 33 is press-fitted onto the hub 24 of the web 7.

[0107] The female part 22 is annular and has a stepped profile in section. The female portion 22 thus comprises an axial base 35, a radial bottom 36, and an axial sleeve 37. The base 35 and the sleeve 37 extend from the bottom 36 in opposite directions. The sleeve 37 is located opposite and at a distance from the shaft 6. The axial base 35 is press-fitted onto the shaft 6. The female portion 22 includes ribs 38 externally connecting the base 35 to the bottom 36. The base 35 is arranged axially between one of the roller bearings (not shown) and a retaining ring 39, which is housed in a groove in the shaft 6. The retaining ring 39 is located on the side of the toothed web 7.

[0108] The coil spring 14 of each shock absorber 10 is annular around the axis X. The spring 14 has an axial end which is in contact with the apron 34 of the male part 21 and an axial end which is in contact with the bottom 36 of the female part 22.

[0109] The oil bath 16 of each shock absorber 10 is annular around the axis X. The oil bath 16 is formed by the inner periphery of the casing 37 of the female part 22, and is axially delimited by the bottom 36 and an inner rim 40 of the casing 37. The height of the inner rim 40 defines the oil height of the bath 16. The surface of the oil bath 16 is shown in dashed lines on [Fig.4].

[0110] The oil inlet 15 includes an annular row of radial orifices 18. Each radial orifice 18 is open, and connects the inside of the barrel 6 to the cavity 20. The radial orifices 18 thus allow the oil inside the barrel 6 to enter the cavity 20 and supply the bath 16, under the effect of centrifugal force.

[0111] The oil outlet 17 is axial and formed by a gap 19 which is defined radially between the flange 33 of the male part 21 and the sleeve 37 of the female part 22. The gap 19 allows excess oil from the bath 16 to leave the cavity 20 under the effect of centrifugal force. The gap 19 forming the oil outlet 17 is dimensioned to allow the flange 33 to slide relative to the sleeve 37, and to evacuate the excess oil from the bath 16.

[0112] Each bearing (not shown) is axially stopped by the base 35 of the female part 22 and a clamping nut (not shown) which is attached to a threaded portion 41 of the barrel 6. Each bearing is lubricated via two annular rows of radial holes 42, the radial holes 42 being formed in the barrel 6. The radial holes 42 allow the oil inside the barrel 6 to access the corresponding bearing, under the effect of centrifugal force.

[0113] The external teeth 8 of the veil 7 are here straight and the grooved linkage 9 is here helical (third couple defined above in the description).

Claims

Demands

1. A gear (5) for an aircraft turbomachine (2), the gear (5) comprising a shaft (6) of revolution about an axis (X) and a toothed disc (7) having external teeth (8), the shaft (6) and the disc (7) being rotationally linked via a splined joint (9), the external teeth (8) and / or the splined joint (9) being configured to at least partially transform the torsional vibratory stresses exerted on the teeth (8) of the disc (7) into an axial displacement of the disc (7), characterized in that the gear (5) comprises two axial dampers (10) disposed on either side of the disc (7), the dampers (10) each being annular about the axis (X), each damper (10) having a first axial end (11) fixed to the shaft (6) and a second axial end (12) integral with the veil (7), so as to axially dampen the toothed veil (7) with respect to the torsional vibratory stresses it undergoes.

2. Gear wheel (5) according to claim 1, characterized in that each damper (10) comprises an elastic damping element (14) which is annular around the axis (X) and which is capable of deforming axially in an elastic manner.

3. Toothed wheel (5) according to the preceding claim, characterized in that the elastic element (14) is either a coil spring (14) or a Belleville washer.

4. Gear wheel (5) according to any one of the preceding claims, characterized in that each damper (10) includes an oil inlet (15) through which a damping oil bath (16) of the damper (10) is supplied, and an oil outlet (17) through which excess oil is expelled from the bath (16).

5. Gear wheel (5) according to the preceding claim, characterized in that the oil inlet (15) is formed in the barrel (6) and at the inner periphery of the shock absorber (10), and the oil outlet (17) is formed at the outer periphery of the shock absorber (10).

6. Gear wheel (5) according to any one of the preceding claims, characterized in that each damper (10) comprises a male part (21) and a female part (22), the male part (21) cooperating by complementarity of form with the female part (22).

7. Gear wheel (5) according to the preceding claim, characterized in that the male part (21) is integral with the web (7) and the female part (22) is integral with the shaft (6).

8. Gear wheel (5) according to the preceding claim, characterized in that the male part (21) is shrunk onto the web (7) and the female part (22) is shrunk onto the shaft (6).

9. Gear wheel (5) according to any one of the preceding claims, characterized in that the external teeth (8) and the splined connection (9) are defined according to one of the following pairs: - the external teeth (8) are helical and the splined connection (9) is helical; - the external teeth (8) are helical and the splined connection (9) is straight; - the external teeth (8) are straight and the splined connection (9) is helical; - the external teeth (8) are spiroconic and the splined connection (9) is straight.

10. Assembly for an aircraft turbomachine (2) comprising a fixed structure (3) and a gear (5) according to any one of the preceding claims, the shaft (6) of the gear (5) being guided in rotation relative to the structure (3) via two roller bearings (13) arranged on either side of the toothed web (7).

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