MECHANICAL REDUCTION GEAR FOR GAS TURBOCHARGERS WITH LONGITUDINAL AXLE

Description

DOMAIN

[0001] The present invention relates to a bearing pivot and more particularly to a pivot intended to be integrated into a reducer of a turbomachine such as a turbojet or a turboprop. CONTEXT

[0002] The role of a mechanical reducer is to modify the speed and torque ratio between the input shaft and the output shaft of a mechanism.

[0003] New generations of dual-flow turbomachines, particularly those with a high bypass ratio, include a mechanical reducer to drive the shaft of a fan. Typically, the reducer's purpose is to transform the so-called fast rotation speed of a power turbine shaft into a slower rotation speed for the shaft driving the fan.

[0004] Such a reducer comprises a central pinion, called a sun gear, a crown gear and pinions called planet gears, which are meshed between the sun gear and the crown gear. The planet gears are held by a frame called a planet carrier. The sun gear, the crown gear and the planet carrier are planet gears because their axes of revolution coincide with the longitudinal axis X of the turbomachine. The planet gears each have a different axis of revolution Y; they are equally distributed on a circle around the axis of the planet gears. These Y axes are parallel to the longitudinal axis X.

[0005] There are several gearbox architectures. In the state of the art of double-flow turbomachines, gearboxes are of the planetary or epicyclic type. Such a gearbox is for example known from document FR 3 047 284 A1. In other similar applications, so-called differential or "compound" architectures exist. On a planetary gearbox, the planet carrier is fixed and the ring gear is the output shaft of the device, which rotates in the opposite direction to the sun gear. On an epicyclic gearbox, the ring gear is fixed and the planet carrier is the output shaft of the device, which rotates in the same direction as the sun gear. On a differential gearbox, no element is fixed in rotation. The ring gear rotates in the opposite direction to the sun gear and the planet carrier.

[0006] Gearboxes can include one or more meshing stages. This meshing is achieved in various ways, such as contact, friction, or magnetic fields. There are several types of contact meshing, such as straight or herringbone.

[0007] Each satellite carried by the planet carrier is mounted to rotate freely on a pivot. The use of a pivot forming a plain bearing with a satellite pinion reduces the size and weight and offers a virtually infinite service life, provided that they are constantly supplied with lubricating and cooling oil. It should also be noted that a pivot can be used with a rolling bearing with an inner ring carried by the pivot, the outer ring then being integral in rotation with a satellite.

[0008] It is known that the temperature of the pivots controls the bearing capacity, whether hydrodynamic or rolling bearing. The higher the temperature, the lower the bearing capacity, i.e. the load capacity, of the pivot. It is therefore clear that controlling the pivot temperature is of prime importance to ensure effective bearing capacity. SUMMARY OF THE INVENTION

[0009] There is thus proposed a mechanical reducer for a gas turbomachine with a longitudinal axis, comprising a crown and satellites engaged with a sun gear and with the crown and each mounted free to rotate about their axis on a planet carrier, the satellites being configured to each rotate about their axis by means of a pivot for a bearing, the pivot comprising a first annular part comprising an axial lubrication passage and a second annular part mounted around the first annular part, the first annular part delimiting with the second annular part a lubrication circuit of which at least one oil inlet opens inside the first annular part in the axial passage and at least one oil outlet opens radially outside the second annular part.

[0010] Unlike the prior art, the pivot is made in two separate pieces and an oil circuit is made in the pivot so as to cool the pivot. Thus, for a given load under given operating conditions, lowering the temperature of the pivot makes it possible to reduce the size of the pivot, thus allowing a weight saving. When the pivot is used in a mechanical reducer, it is understood that reducing the mass of several pivots proves to be all the more advantageous.

[0011] According to another characteristic, the first annular part comprises an annular wall in which a plurality of annular grooves are formed around which the second annular part is mounted in a sealed manner. The annular grooves are open radially outwards and the radially external outlets of the annular grooves are closed by the second annular part.

[0012] According to another characteristic, the lubricating oil circuit comprises a plurality of annular grooves formed in an annular wall, the second annular part being mounted around the annular grooves and mounted sealingly around them.

[0013] The first annular part and the second annular part can be made by casting or by additive manufacturing. The assembly simplifies the design of the first annular part and the second annular part.

[0014] The annular grooves may be in fluid communication with each other.

[0015] The oil inlet of the lubricating oil circuit opens into an annular groove positioned longitudinally at half the length of the pivot.

[0016] The pivot may comprise 2k+1 annular grooves, k being a positive integer, preferably greater than or equal to 3. In a particular embodiment, the number of annular grooves may be equal to 5.

[0017] The annular grooves communicate fluidically by means of openings, such as slots, formed in annular partitions separating the annular grooves. Orifices may be formed in the annular partitions.

[0018] Each groove comprises a radial wall joining two consecutive partitions so as to prevent the circulation of oil over 360°, each radial wall circumferentially separating a first circumferential end of the annular groove and a second circumferential end of the annular groove, each annular groove comprising an oil inlet at its first circumferential end and an oil outlet at its second circumferential end.

[0019] The oil thus circulates circumferentially from the first circumferential end of an annular groove to the second circumferential end of said annular groove so as to allow oil circulation over substantially 360° and thus best cool the pivot annularly.

[0020] The two annular grooves at longitudinal ends may each comprise an oil outlet connected to a channel, one downstream end of which opens radially outside the second annular part.

[0021] The invention also relates to a gas turbomachine for aircraft comprising such a mechanical reducer whose sun gear surrounds and is integral in rotation with a shaft of the compressor of the turbomachine.

[0022] The turbomachine can also be such that the crown is integral with a static annular casing or shell of the low pressure compressor.

[0023] The pivot according to this document can be used in a hydrodynamic plain bearing or in a rolling bearing, for example ball or roller bearing.

[0024] The invention will be better understood and other details, characteristics and advantages of the invention will appear on reading the following description given by way of non-limiting example with reference to the appended drawings. BRIEF DESCRIPTION OF THE FIGURES

[0025] [ Fig.1 ] there figure 1 is a schematic axial sectional view of a turbomachine using the invention, [ Fig.2 ] there figure 2 is a partial axial sectional view of a mechanical reducer; [ Fig.3 ] there figure 3 is a schematic view of a pivot according to the present invention and according to a section plane comprising the longitudinal axis Y of the pivot; [ Fig.4 ] there figure 4 is a schematic perspective view of the first annular part of the pivot according to the present invention; [ Fig.5 ] there figure 5 is another schematic perspective view of the first annular part of the pivot according to the present invention; [ Fig.6 ] there figure 6 is a schematic view of a pivot according to the present invention, along a section plane substantially perpendicular to the longitudinal Y axis of the pivot; [ Fig.7 ] there figure 7 is a schematic view of a longitudinal end of the pivot according to the invention; [ Fig.8 ] there figure 8 is a schematic view of one longitudinal end of the first pivot part. DETAILED DESCRIPTION

[0026] There figure 1 describes a turbomachine 1 which comprises, in a conventional manner, a fan S, a low-pressure compressor 1a, a high-pressure compressor 1b, an annular combustion chamber 1c, a high-pressure turbine 1d, a low-pressure turbine 1e and an exhaust nozzle 1h. The high-pressure compressor 1b and the high-pressure turbine 1d are connected by a high-pressure shaft 2 and form with it a high-pressure (HP) body. The low-pressure compressor 1a and the low-pressure turbine 1e are connected by a low-pressure shaft 3 and form with it a low-pressure (LP) body.

[0027] The blower S is driven by a blower shaft 4 which is driven to the LP shaft 3 by means of a reducer 6. This reducer 6 is generally of the planetary or epicyclic type.

[0028] The following description concerns a reducer of the epicyclic type, the planet carrier and the sun gear of which are rotatable, the crown of the reducer being fixed in the motor frame of reference. However, the description also applies to a reducer of another type, such as a planetary or differential reducer.

[0029] The reducer 6 is positioned in the upstream part of the turbomachine. In the present application, the expressions upstream and downstream refer to the direction of the general flow of gases in the turbomachine, along its axis of elongation or rotation of its rotors. A fixed structure comprising schematically, here, an upstream part 5a and a downstream part 5b which composes the motor casing or stator 5 is arranged so as to form an enclosure E surrounding the reducer 6. This enclosure E is here closed upstream by seals at the level of a bearing allowing the fan shaft 4 to pass through, and downstream by seals at the level of the passage of the LP shaft 3.

[0030] There figure 2 shows an epicyclic reducer 6. At the input, the reducer 6 is connected to the LP shaft 3, for example via internal splines 7a. Thus, the LP shaft 3 drives a planetary pinion called the sun gear 7. Conventionally, the sun gear 7, whose axis of rotation coincides with that of the turbomachine X, drives a series of pinions called satellites 8, which are equally distributed over the same diameter around the axis of rotation X. This diameter is equal to twice the operating center distance between the sun gear 7 and the satellites 8. The number of satellites 8 is generally defined between three and seven for this type of application.

[0031] All of the satellites 8 are held by a frame called a planet carrier 10. Each satellite 8 rotates around its own Y axis, and meshes with the crown 9.

[0032] At the output we have: In this epicyclic configuration, the set of planet gears 8 rotates the planet carrier 10 around the axis X of the turbomachine. The ring gear is fixed to the engine casing or stator 5 via a ring gear carrier 12 and the planet carrier 10 is fixed to the fan shaft 4. In another planetary configuration, the set of planet gears 8 is held by a planet carrier 10 which is fixed to the engine casing or stator 5. Each planet gear drives the ring gear which is attached to the fan shaft 4 via a ring gear carrier 12.

[0033] Each planet gear 8 is mounted to rotate freely using a bearing 11, for example of the rolling bearing or hydrodynamic bearing type. Each bearing 11 is provided on one of the tubular supports 10b of the planet carrier 10 and all the supports are positioned relative to each other using one or more structural frames 10a of the planet carrier 10. The bearing may be formed by a pivot around which a planet gear is mounted, thus forming a hydrodynamic bearing. The bearing may be of the rolling bearing type and comprise an inner ring formed or integral with the pivot and an outer ring integral with the planet gear. There are a number of tubular supports 10b and bearings 11 equal to the number of planet gears. For reasons of operation, assembly, manufacturing, inspection, repair or replacement, the supports 10b and the frame 10a may be separated into several parts.

[0034] For the same reasons mentioned above, the teeth of a reducer can be separated into several helices, each having a median plane P. In our example, we detail the operation of a reducer with several helices with a crown separated into two half-crowns:

[0035] An upstream half-crown 9a consisting of a rim 9aa and a half-fixing flange 9ab. On the rim 9aa is the upstream helix of the gear teeth. This upstream helix meshes with that of the satellite 8 which meshes with that of the solar 7.

[0036] A 9b downstream half-crown consisting of a 9ba rim and a 9bb fixing half-flange. On the 9ba rim is the downstream helix of the reduction gear teeth. This downstream helix meshes with that of the satellite 8 which meshes with that of the solar 7.

[0037] If the helix widths vary between the sun gear 7, the satellites 8 and the crown wheel 9 due to the tooth overlaps, they are all centered on a median plane P for the upstream helices and on another median plane P for the downstream helices. In the case of a double-row roller bearing, each row of rolling elements is also preferably, but not necessarily, centered on two median planes.

[0038] The half-clamp 9ab of the upstream crown 9a and the half-clamp 9bb of the downstream crown 9b form the crown mounting flange 9c. The crown 9 is fixed to a crown carrier by assembling the crown mounting flange 9c and the crown carrier mounting flange 12a using a bolted assembly for example.

[0039] The arrows of the figure 2 describe the routing of the oil in the reducer 6. The oil arrives in the reducer 6 from the stator part 5 in a distributor 13 by different means which will not be specified in this view because they are specific to one or more types of architecture. The distributor 13 comprises injectors 13a and arms 13b. The injectors 13a have the function of lubricating the teeth and the arms 13b have the function of lubricating the bearings. The oil is brought to the injector 13a to exit through the end 13c in order to lubricate the teeth. The oil is also brought to the arm 13b and circulates via the supply mouth 13d of the bearing 11. The oil then circulates through the support 10b in one or more cavities 10c to then exit through pipes 10d in order to lubricate the bearings of the satellites.

[0040] The bearing thus comprises a pivot 14 as shown in figures 3 and following. More particularly, the figure 3 represents the pivot 14 in its entirety comprising a first annular part 14a and a second annular part 14b. The figure 4 represents the first annular part 14a in isolation.

[0041] According to the invention, the second annular part 14b externally surrounds the first annular part 14a. The first annular part 14a comprises an annular wall 15 connected at its ends to two tubular portions 16. The annular wall 15 and the tubular portions 16 together internally delimit an axial passage 17. This passage is tubular and is coaxial with the Y axis of the pivot. The first annular part 14a comprises a plurality of annular grooves G1, G2, G3, G4, G5 along the longitudinal Y axis of the pivot 14. The annular grooves G1, G2, G3, G4, G5 are delimited laterally by radial annular partitions 18. The radial annular partitions 18, with the exception of the longitudinal end partitions 18a, 18b, comprise openings 19, such as slots, allowing the passage of oil from one annular groove to the other.

[0042] The first annular part 14a comprises an odd number of grooves, i.e. 2k+1 annular grooves, with k a positive integer. It could also comprise an even number of annular grooves. In the case illustrated in the figures, the first annular part comprises 5 annular grooves, namely a first annular groove G1 with a longitudinal end, a second annular groove G2, a third annular groove G3, a fourth annular groove G4 and a fifth annular groove G5 with a longitudinal end.

[0043] The second annular part 14b comprises a cylindrical wall 21 mounted in a sealed manner (sealed assembly) around the first annular part 14a so that a radially internal cylindrical surface of this cylindrical wall 21 closes the annular grooves G1, G2, G3, G4, G5 by bearing on the radially external ends of the radial annular partitions 18. The annular grooves G1, G2, G3, G4, G5 are in fluid communication with each other so as to form an oil circuit between the first annular part 14a and the second annular part 14b.

[0044] As can be seen on the figure 4 , the first annular part 14a comprises at least one oil inlet 20 for cooling the pivot 14. In this case, it comprises a plurality of oil inlet orifices 20 substantially aligned circumferentially, these orifices 20 opening radially inwards into the axial passage and being able to be fluidically connected to the channels 10d previously described. These oil inlet orifices open into the third annular groove G3.

[0045] Each annular groove G1, G2, G3, G4, G5, comprises a radial wall 22 or a wall element 24 joining two consecutive partitions so as to prevent the circulation of oil over 360°, each radial wall 22 or wall element 24 circumferentially separating a first circumferential end of the annular groove and a second circumferential end of the annular groove ( figures 4 et 5 ). It is observed that in the case of the second G2, third G3 and fourth G4 annular grooves, the radial wall extends longitudinally and that in the case of the first G1 and fifth G5 annular grooves, the wall element 24 extends over a greater angular distance and houses an oil flow channel 26 whose upstream end is connected to the second circumferential end of the first annular groove G1 and the fifth annular groove G5 and whose downstream end is connected to an oil outlet 28 formed in the cylindrical wall 21 of the second annular part 14b ( figure 6 ).

[0046] Each annular groove G1, G2, G3, G4, G5 comprises an oil inlet at its first circumferential end and an oil outlet at its second circumferential end. More particularly, the oil inlet in the third annular groove G3 is formed by the orifices 20 formed at the first circumferential end of the third annular groove G3. This third annular groove G3 comprises two oil outlets arranged at its second circumferential end, a first being formed by an opening 19 for supplying oil to the first circumferential end of the second annular groove G2 and by an opening 19 for supplying oil to the first circumferential end of the fourth annular groove G4. The oil then flows over 360° to the second end of the second annular groove G2 and to the second circumferential end of the fourth annular groove G4.It then enters the first annular groove G1 at its first circumferential end through an opening 19 and into the fifth annular groove G5 at its first circumferential end through an opening 19. It then flows into the first G1 and fifth G5 annular grooves, then into the respective channels 26 to the oil outlet orifices 28 of the second annular part 14b.

[0047] The creation of an oil circuit in the pivot 14 allows its operating temperature to be lowered, which allows a reduction in its dimensions while allowing unchanged load resistance. Thus, the mass of the pivot is reduced as is that of the mechanical reducer. In the case of an epicyclic configuration, the reduction in mass reduces the radial loads of the planet carrier, which could also have a reduced mass.

[0048] There figure 7 illustrates a possible mechanical connection between the first annular part 14a and the second annular part 14b to allow axial locking of the two annular parts together. This axial locking can be achieved by the presence of an annular rim 30 extending radially inwards from the cylindrical wall 21 of the second annular part and which is engaged in an annular groove 32 of the first annular part 14a. Other locking means can be envisaged such as screwing or welding. A rotational locking of the first annular part 14a and second annular part 14b can be provided and achieved for example by the formation of a notch 34 on a radial annular partition 18, this notch 24 cooperating with a member of the second annular part 14b ( figure 8 ).

Claims

1. A reduction gear for a gas turbomachine with a longitudinal axis, comprising a ring gear and planet gear (8) meshing with a sun gear (7) and with the ring gear (9) each mounted free in rotation about their axis (Y) on a planet carrier (10), each of the planet gears (8) being configured to rotate about their axis (Y) through a pivot (14) which comprises a first annular part (14a) including a lubrication axial passage (17) and a second annular part (14b) mounted around the first annular part (14a), the first annular part (14a) delimiting with the second annular part (14b) a lubrication circuit at least one oil inlet (20) of which opens out inside the first annular part (14a) into the axial passage (17) and at least one oil outlet (28) of which opens radially outwards of the second annular part (14b), wherein the first annular part (14a) comprises an annular wall (15) in which a plurality of annular grooves (G1, G2, G3, G4, G5) are formed around which the second annular part (14b) is sealingly mounted, the annular grooves (G1, G2, G3, G4, G5) fluidly communicating by means of openings (19), such as slots, formed in annular partition walls (18) of the annular grooves (G1, G2, G3, G4, G5), each annular groove (G1, G2, G3, G4, G5) comprising a radial wall (22, 24) joining two consecutive partition walls (18) so as to prevent oil circulation over 360°, each radial wall (22, 24) circumferentially separating a first circumferential end of the annular groove (G1, G2, G3, G4, G5) and a second circumferential end of the annular groove, each annular groove (G1, G2, G3, G4, G5) comprising an oil inlet at its first circumferential end and an oil outlet at its second circumferential end.

2. The reduction gear according to claim 1, wherein the annular grooves (G1, G2, G3, G4, G5) are in fluidic communication with each other.

3. The reduction gear according to claim 2, wherein the oil inlet (20) of the lubrication circuit opens out into an annular groove (G1, G2, G3, G4, G5) positioned longitudinally at the mid-length of the pivot (14).

4. The reduction gear according to one of claims 1 to 3, comprising 2k+1 annular grooves, k being a positive integer number, preferably greater than or equal to 3.

5. The reduction gear according to one of claims 1 to 4, wherein each of the two annular grooves (G1, G5) with longitudinal ends comprises an oil outlet connected to a channel (26) whose downstream end opens out radially outwards of the second annular part (14b).

6. A gas turbomachine for an aircraft comprising a reduction gear (6) according to one of the preceding claims whose sun gear (7) surrounds and is rotatably secured to a shaft of the compressor of the turbomachine.

7. The turbomachine according to the preceding claim, wherein the ring gear is secured to a stator annular casing or shroud.