Reduction gear for an aircraft turbine engine and turbine engine equipped with such a reduction gear

Abstract

This reduction gear (3) for an aircraft turbine engine comprises a fan shaft (14) and a planet carrier (15) separated from the fan shaft and comprising means (18, 19) for rotationally securing the fan shaft and the planet carrier. It comprises means (23) for axially fixing the fan shaft and the planet carrier. The rotational securing means comprise a spline (18) provided on the planet carrier and in engagement with a corresponding spline (20) of the fan shaft.

Description

[0001] DESCRIPTION

[0002] TITLE: REDUCTION GEAR FOR AIRCRAFT TURBOMACHINES AND TURBOMACHINES EQUIPPED WITH A REDUCTION TEE

[0003] technical field

[0004] The invention relates, in general, to mechanical reducers for aircraft turbomachinery and relates more particularly to the assembly of a fan shaft and a satellite carrier for such a reducer.

[0005] Previous techniques

[0006] The role of a mechanical reducer is to change the speed and torque ratio between the input and output shafts of a mechanical system.

[0007] With regard to aircraft turbomachinery, and in particular double-flow turbomachinery, especially those with a very high bypass ratio, the mechanical reducer has the role of driving the shaft of a fan by transforming the so-called high rotational speed of the shaft of a power turbine into a slower rotational speed for the shaft driving the fan.

[0008] Such a reducer includes a central pinion, called the sun gear, a ring gear, and pinions called satellite gears that mesh between the sun gear and the ring gear.

[0009] The satellites are held by a frame called a satellite carrier. The solar array, the corona, and the satellite carrier are planetary because their axis of revolution coincides with the longitudinal X-axis of the turbomachine.

[0010] The satellites have different axes of revolution distributed over the same operating diameter around the axis of the planetary bodies.

[0011] These axes are parallel to the longitudinal axis X.

[0012] There are several gearbox architectures. In the state of the art of double-flow turbomachinery, gearboxes are of the planetary or epicyclic type.

[0013] In other similar applications, there are so-called differential architectures.

[0014] On a planetary reducer, the planet carrier is fixed and the ring gear forms the output shaft of the device which rotates in the opposite direction to the sun.

[0015] On an epicyclic reducer, the ring gear is fixed and the satellite carrier constitutes the output shaft of the device which rotates in the same direction as the sun gear.

[0016] On a differential gearbox, no element is fixed for rotation. The ring rotates in the opposite direction to the solar panel and the satellite carrier.

[0017] In some types of gearboxes, the planet carrier is integrated with the blower shaft. This makes the component more complex to manufacture. Furthermore, this type of solution presents increased constraints in terms of sizing, manufacturing, and maintenance because the stresses of the integrated component, and therefore of the gearbox, correspond to those of the blower shaft.

[0018] Furthermore, this type of solution does not allow for modularity in order to quickly separate the blower shaft and the reducer when dismantling the motor.

[0019] To overcome these drawbacks, it has been proposed to separate the blower shaft and the satellite carrier into two separate parts.

[0020] Description of the invention

[0021] In view of the foregoing, the aim of the invention is to propose a reducer in which the blower shaft and the planet carrier are made up of separate parts and for which a linkage ensures the transfer of torque and the centering of the parts.

[0022] The invention therefore relates to a gearbox for an aircraft turbomachine, comprising a fan shaft and a planet carrier separate from the fan shaft, and including means for rotational locking and means for axial fixing of the fan shaft and the planet carrier.

[0023] According to another feature of the reducer, the means of rotational locking include a spline provided on the planet carrier, in contact with a corresponding spline of the blower shaft.

[0024] In one embodiment, the spline of the blower shaft is supported by an annular spacer extending radially from the blower shaft, said spacer comprising an external radial surface receiving a blower shaft mounting bearing in which the blower shaft truncates.

[0025] Advantageously, the annular spacer has internal axial grooves regularly distributed around the spacer.

[0026] In another embodiment, the splines are axially offset relative to a blower shaft mounting bearing in which the blower shaft truncates.

[0027] In one embodiment, the axial fixing means include an axial clamping nut for the satellite carrier and the blower shaft.

[0028] For example, the nut is screwed onto a thread made on a cylindrical bearing surface of the blower shaft, against a radial annular stop of the planet carrier.

[0029] Alternatively, the nut can be screwed onto a thread made on a cylindrical bearing surface of the planet carrier, against a radial annular stop of the blower shaft.

[0030] In one embodiment, the nut is insertable from the upstream side of the blower shaft.

[0031] Preferably, the annular stop is formed of a set of partially annular sectors suitable for the passage of the nut from a proximal end of the blower shaft.

[0032] In another embodiment, the axial mounting means comprise a set of bolted connections between the fan shaft and the planet carrier. The invention also relates to an aircraft turbomachine, comprising a gearbox as defined above.

[0033] Brief description of the drawings

[0034] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings in which:

[0035] Figure 1 schematically illustrates an aircraft turbomachine, equipped with a reducer according to the invention;

[0036] The [Fig 2] is a cross-sectional view of a blower shaft-satellite carrier assembly of the turbomachine gearbox in Figure 1;

[0037] Figure 3 is a perspective view of the whole of Figure 2;

[0038] The [Fig 4] ; is a cross-sectional view of a blower shaft-satellite carrier assembly of the turbomachine gearbox of figure 1, according to another embodiment;

[0039] Figures [Fig 5] and [Fig 6] illustrate the annular thrust bearing of the blower shaft of the turbomachine in Figure 1;

[0040] Figures 7 and 8 illustrate another embodiment of a blower shaft-satellite carrier assembly of the turbomachine reducer in Figure 1;

[0041] Figures 9 and 10 illustrate other embodiments of a blower shaft-satellite carrier assembly of the turbomachine gearbox in Figure 1;

[0042] Figure 11 illustrates a variant embodiment of the blower shaft-satellite carrier assembly of Figure 10;

[0043] Figure 12 schematically illustrates one embodiment of a blower shaft-satellite carrier assembly using a conical spline; and

[0044] Figure 13 schematically illustrates another embodiment of a blower shaft-satellite carrier assembly in which the axial fixing bolts are brought closer to the axis of rotation.

[0045] Detailed description

[0046] Figure 1 shows a turbojet engine for an aircraft according to the invention, designated by the general numerical reference 1, with axis XX.

[0047] This turbojet 1 is a twin-flow turbojet which has at the front, considering the direction of the airflow admitted into the turbojet, a fan 2 which is connected to a reducer 3, then a low-pressure compressor 4 and a high-pressure compressor 5.

[0048] The turbomachine 1 also includes a combustion unit 6, then, downstream, a high-pressure turbine 7 which supplies air to said combustion unit 6 and, further downstream, a low-pressure turbine 8.

[0049] The hot gases from combustion pass through the low-pressure turbine 7 which drives the blower before escaping through an exhaust nozzle 9.

[0050] The assembly comprising the reducer 3, the low pressure compressors 4 and high pressure compressor 5, as well as the combustion equipment 6 and the high pressure turbines 7 and low pressure turbines 8 are placed in an inner casing 10 which is surrounded by an annular outer casing 12 held by spacers 13 connecting the casings 10 and 12.

[0051] Figures 2 and 3 show the blower shaft 14 and the planet carrier 15 of the reducer 3.

[0052] As can be seen, the tree 14 and the satellite carrier 15 are distinct and separate elements.

[0053] They each comprise a proximal end I intended to receive the driving torque, with regard to the planet carrier 15, and to transmit the driving torque to the blower, with regard to the blower shaft 14, and a distal coupling end II at which the blower shaft 14 and the planet carrier are rotationally secured and axially fixed.

[0054] As can be seen, the blower shaft 14 rotates in a main bearing 16 and in a secondary bearing 17.

[0055] The blower shaft 14 and the planet carrier 15 are rotationally secured by means of securing means comprising a right male spline 18 carried by an axial cylindrical extension 19 of the planet carrier 15 and a female spline 20 carried by the blower shaft 14.

[0056] In the embodiment of figures 2 and 3, the splines are radially aligned with respect to the bearing 16. In figure 2, they are in fact positioned below the bearing 16, that is to say internally with respect to the bearing 16.

[0057] The female spline of the blower shaft 14 is formed internally in an annular spacer 21 which extends radially from the blower shaft 14 and which externally has an external radial surface S supporting the main bearing 16.

[0058] Advantageously, the spacer 21 has 360° grooves 22 around the spacer, which lighten the spacer and allow the splines 18 and 20 and the main bearing 16 to be mechanically separated by locally creating a bending zone in the vicinity of the support zone of the main bearing 16.

[0059] It should be noted, however, that spacer 21 is optional. It is indeed possible to radially bring the splines of the main bearing closer together.

[0060] The blower shaft 14 and the satellite carrier 15 are rotationally secured by means of the straight male splines 18 and female splines 20.

[0061] The blower shaft 14 and the planet carrier 15 are axially fixed by means of the spacer 21 bearing against the planet carrier and by means of a nut 23 which screws into an external thread of an axial cylindrical bearing surface 24 of the blower shaft 14, against an annular stop 25 which extends radially from the cylindrical extension 19 of the planet carrier 15. It should be noted that the nut 23 is held in place, either floating inside the cylinder 19 or in a retention position provided for this purpose, before the gears are mounted. It should also be noted that the term "gears" refers to all the gears of the reduction gear, namely the sun gear, planet gears, and ring gears.

[0062] During the assembly of the reducer, the nut 23 is screwed on using a tool inserted from the proximal end of the blower shaft 14.

[0063] In the embodiment of figure 4, the means for axially fixing the blower shaft and the planet carrier can be made in the form of a nut 23 screwed onto a cylindrical bearing surface 28 extending from the cylindrical extension 19 of the planet carrier 15. This nut is screwed against an annular stop 29 extending radially from the wall of the blower shaft 14.

[0064] With reference to figures 5 and 6, in order to allow the insertion of the nut 23 from the distal end II of the blower shaft, the stop 29 is made in the form of a set of sectors 30 configured so as to allow the nut 23 to pass in an inclined position.

[0065] The number of sectors 30 and their angular extent result from a compromise between, on the one hand, the ease of assembly by facilitating the insertion of the nut and, on the other hand, the increase of the bearing surface for the nut 23.

[0066] Advantageously, but in no way limitingly, the stop 29 is formed of two sectors of approximately 45°.

[0067] This embodiment is advantageous because the nut is inserted during the assembly of the blower shaft. Therefore, it is not necessary to pre-mount it on the planetary carrier.

[0068] In another embodiment illustrated in Figures 7 and 8, the blower shaft 14 and the planet carrier 15 are assembled using a set of bolted connections, such as 32, comprising a set of flanges, such as 33, evenly distributed around the distal end of the blower shaft and a set of corresponding bolts 34. The bolts do not perform any torque transmission function but serve to axially fix the blower shaft 14 and the planet carrier 15.

[0069] Of course, the number of screw connections can vary. For example, three equally spaced screw connections can be used, while still achieving a rigidity comparable to that of a monobloc solution for the blower shaft and the planet carrier.

[0070] In the embodiment described with reference to Figures 2 to 8, the male and female splines are radially aligned with respect to the main bearing 16. However, with reference to Figure 9, which corresponds to the embodiment of the axial mounting means of Figure 4, it is possible to axially offset the male splines 18 and 20 with respect to the external radial surface S of the blower shaft 14 receiving the main bearing 16, thus avoiding the need for the annular spacer 21, as described previously with reference to Figures 2 and 3. It should be noted that in the case of Figure 9, the nut can be inserted from the upstream side of the blower shaft. It is not necessary to insert it beforehand.

[0071] Of course, the axial offset of the splines relative to the bearing 16 can be combined with the different embodiments of the axial fixing means described previously with reference to figures 2 to 8.

[0072] It should also be noted that the position of the spline is not limited to that shown in Figure 9. It can also extend along the entire length of the blower shaft. However, it is advantageous to position it as close as possible to the planet carrier to minimize the overall mass.

[0073] With reference to figure 10, in order to bring the spline closer to the satellite carrier, it is advantageous to equip the blower shaft with an internal axial cylindrical branch 36, to support the male spline 35. This branch 36 cooperates with a female spline carried by the axial cylindrical extension 19 of the satellite carrier 15.

[0074] In this embodiment, the axial fixing of the blower shaft 14 and the planet carrier 15 is achieved by bringing the main bearing support 16 into contact with the planet carrier 15. It can also be achieved by pinching the radial part which extends internally from the arm 19 between the nut and a stop formed on the arm 36.

[0075] A nut 40 is used to secure it. It must be inserted and held in place in the planet carrier before the planet gears are mounted.

[0076] It is also possible, as seen in Figure 11, to offset the axial stop of the blower shaft radially internally, by providing a radial end stop 37.

[0077] In this case, the nut 38, carried by the planet carrier 15, can then be inserted, without difficulty, from inside the blower shaft.

[0078] As described previously, in this embodiment, axial fixing can also be achieved using screw connections, as described previously with reference to Figures 7 and 8.

[0079] It should be noted, with reference to figure 12, that the invention which has just been described, and in particular the rotational locking of the blower shaft and the satellite carrier, can be implemented by means of conical male and female splines 39.

[0080] In this case, it will be advantageous to use an axial fixing of the blower shaft and the satellite carrier by means of screw connections using flanges and bolting.

[0081] Finally, it should be noted, with reference to figure 13, that when using an axial fixing by screw connection, it is possible to bring the bolts 34 and the flanges 33 closer to the axis of rotation.

[0082] The bolts can then be tightened from the proximal end of the blower shaft.

[0083] Although this implementation illustrated in Figure 13 corresponds to the embodiment of Figure 10, such a variant can also be used for all the embodiments described above.

Claims

DEMANDS 1. Gearbox (3) for an aircraft turbomachine, comprising a fan shaft (14) and a planet carrier (15) separate from the fan shaft and comprising means (18, 20) for rotationally locking the fan shaft and the planet carrier, characterized in that it comprises means (23; 38) for axially fixing the fan shaft and the planet carrier, wherein the rotationally locking means comprise a spline (18) provided on the planet carrier, engaging with a corresponding spline (20) of the fan shaft, the spline (20) of the fan shaft being supported by an annular spacer (21) extending radially from the fan shaft, said spacer comprising an external radial surface (S) receiving a bearing (16) in which a trunnion the blower shaft, the splines (16, 18) being radially aligned with respect to the bearing (16).

2. Reducer according to claim 1, in which the annular spacer (21) has internal grooves at 360° (22).

3. Reducer according to any one of claims 1 to 2, wherein the axial fixing means comprise an axial clamping nut (23; 38) of the planet carrier (15) and of the blower shaft (14).

4. Reducer according to claim 3, in which the nut (23) is screwed onto a thread made on a cylindrical bearing surface (24) of the blower shaft, against a radial annular stop (25) of the planet carrier.

5. Reducer according to claim 3, in which the nut is screwed onto a thread made on a cylindrical bearing surface (28) of the satellite carrier, against a radial annular stop (29) of the blower shaft.

6. Reducer according to claim 5, wherein the annular stop is formed of a set of partially annular fittings suitable for the passage of the nut from a proximal end of the blower shaft.

7. Reducer according to any one of claims 1 to 3, wherein the nut is insertable from the upstream side of the blower shaft.

8. Reducer according to any one of claims 1 to 2, wherein the axial fastening means comprise a set of screw connections (32) between the blower shaft and the planet carrier.

9. Aircraft turbomachine, comprising a reduction gear according to any one of claims 1 to 8.

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