Patent ID: 12209652

DETAILED DESCRIPTION OF THE INVENTION

FIG.1shows a turbomachine that is intended to be mounted on an aircraft. The turbomachine illustrated is a turbofan, but the invention is not limited to this turbomachine. The turbomachine can be a turboprop engine and comprise a single propeller or a doublet of counter-rotating propellers rotating around a longitudinal axis and designated by the expression “open rotor” for unducted propeller or unducted propellers. The turbomachine can also be a turboshaft engine.

Generally speaking, a double-flow turbomachine1with a longitudinal axis X comprises, from upstream to downstream and in the direction of flow of the gas flows, a compressor cross-section, a combustion chamber1c, and a turbine cross-section. The compressor cross-section may comprise a low-pressure compressor1aand a high-pressure compressor1b. The turbine cross-section may comprise a low-pressure turbine1eand a high-pressure turbine1d. The compressors, the combustion chamber and the turbines form a gas generator. The high-pressure compressor1band the high-pressure turbine1dare connected by a high-pressure shaft2and together they form a high-pressure (HP) body. The low-pressure compressor1aand the low-pressure turbine1eare connected by a low-pressure shaft3and together they form a low-pressure (LP) body.

Downstream of the low-pressure turbine1e, an exhaust nozzle1his arranged to allow the evacuation of the gases resulting from the combustion chamber1coutward.

A fan4is mounted upstream of the low-pressure compressor1a. The fan4is driven by a fan shaft5which is driven by the LP shaft3by means of a mechanical reducer6. The fan4comprises a plurality of fan vanes7that extend radially outward from a fan disc. The fan vanes7are radially delimited by a fan casing8. The latter carries a nacelle attached to the aircraft.

The reducer6is formed with a gear train and is known by the acronym RGB for “Reduction Gear Box”. The reducer6is generally of the planetary or epicyclic type. The reducer comprises, as schematically illustrated inFIG.2, a sun gear10(or internal planetary), planet gears11, a planet carrier12and a ring gear13(or external planetary). The sun gear10, the ring gear13and the planet carrier12are planetary because their axes of revolution coincide with the longitudinal axis X of the turbomachine. The planet gears each have a different axis of revolution and are equally distributed on the same operating diameter around the axis of the planetaries. These axes are parallel to the longitudinal axis X.

In this example, the reducer6is here with a planetary gear train. The input of the reducer is coupled to the LP shaft3while the output of the reducer is coupled to the fan shaft. In particular, the ring gear13is rotatable and the planet carrier12is non-rotatable.

Although the following description refers to a reducer with planetary-type gear train, it also applies to an epicyclic gear train or a mechanical differential gear train in which the three components, namely the planet carrier, the ring gear and the sun gear, are rotatable, the rotational speed of one of these components being dependent, in particular, on the difference in speed of the other two components.

The reducer6is positioned in the upstream portion of the turbomachine. A stationary structure14schematically comprises an upstream portion14aand a downstream portion14b, which makes up the motor casing or stator. The stationary structure is arranged to form an enclosure E surrounding the reducer6. This enclosure E is closed upstream by seals at the level of an upstream bearing allowing the passage of the fan shaft5, and downstream by seals at the level of the passage of the LP shaft3. The upstream bearing allows to support and guide the fan shaft5in rotation in order to support the radial and axial loads it is subjected to. This upstream bearing is mounted in the enclosure E. Two upstream bearings can be provided to guide the fan shaft5in rotation as shown inFIG.2.

FIGS.2and3show the reducer6, which can take the form of different architectures depending on whether certain parts are stationary or rotating. The input of the reducer6is connected to the LP shaft3, for example by means of internal splines15. Thus, the LP3shaft drives the sun gear. Classically, the sun gear10, whose axis of rotation is coincident with that of the turbomachine X, drives the planet gears11, which are equally spaced on the same diameter around the axis of rotation X. This diameter is equal to twice the operating centre distance between the sun gear10and the planet gears11. The number of planet gears11is generally defined between three and seven for this type of application.

The assembly of the planet gears11is maintained by a frame which is the planet carrier12. Each planet gear11, in the form of pinion, rotates around its own axis Y, and meshes with the ring gear13. At the output, the assembly of the planet gears11is maintained by the planet carrier10which is attached to the motor casing or stator14. Each planet gear drives the ring gear13which is fitted to the fan shaft4. A ring gear carrier16is provided to connect the fan shaft10to the ring gear13. The planet gears11are mounted freely rotatably by means of bearings, for example of the roller or hydrostatic bearing type. Each bearing is mounted on one of the axles of the planet carrier and all the axles are positioned relative to each other using one or more structural frame of the planet carrier.

InFIG.4, the ring gear13is provided with an internal toothing that meshes with the toothing of the planet gears. In the present example of embodiment, the ring gear13is formed in two portions (i.e. two half-ring gears). A downstream half-ring gear17consists of a rim17aand an attachment half-flange17b. The flange17bextends radially outward. An upstream half-ring gear18consists of a rim18aand an attachment half-flange18b. The flange18bextends radially outward. The rim17acomprises an upstream toothing segment in the form of an upstream propeller of the toothing of the reducer. This upstream propeller meshes with that of the planet gear11which meshes with that of the sun gear10. The rim18acomprises a downstream toothing segment also in the form of a downstream propeller of the toothing of the reducer. This downstream propeller meshes with that of the planet gear11which meshes with that of the sun gear10. Such a configuration allows to make it even easier to manufacture the ring gear and to facilitate the recovery of the oil. If the propeller widths vary between the sun gear10, the planet gears11and the ring gear13because of the toothings overlaps, they are all centred on a median plane for the upstream propellers and on another median plane for the downstream propellers.

The attachment half-flange17bof the downstream half-ring gear and the attachment half-flange18bof the upstream half-ring gear form the attachment flange19of the ring gear. The ring gear13is attached to the ring gear carrier by assembling the attachment flange19of the ring gear and an attachment flange of the ring gear carrier. This attachment is made by means of attachment members20such as screws, bolts and/or nuts.

During operation, the oil is supplied to the reducer6from the stator portion14via a dispenser (not shown) by various means which are specific to one or more types of architecture. The dispenser is separated into two portions, each repeated with the same number of planet gears. The dispenser comprises injectors21a(seeFIG.3) whose function is to lubricate the toothings of the wheels and/or pinions of the reducer and arms whose function is to lubricate the bearings of the reducer. The oil is fed towards the injectors21ato emerge from ends in order to lubricate with oil referred to as cold oil (HF) the toothings of the planet gears11, of the sun gear10and also of the ring gear13. The oil is also fed towards the arm and circulates through the feed opening of the bearing. The oil then flows through the shaft into one or more buffer areas and then emerge through the orifices to lubricate the bearings of the planet gears.

With reference toFIG.3, due to centrifugal forces, oil referred to as hot oil HC for lubricating the toothings is sprayed radially outward in relation to the axles Y of the planet gears. The hot oil is also sprayed and ejected by centrifugal effect from the ring gear13. In particular, the oil is ejected radially outward at the level of the attachment flange19via oil ejection means. The ejection means here comprise one or more channels that are regularly formed between the two half-ring gears and over the entire circumference of the ring gear13.

Advantageously, but not restrictively, first channels22extend substantially along the radial axis Z. Each first channel22extends radially between an inlet orifice23defined in an internal surface of the ring gear (and which comprises the toothing) and an outlet orifice24defined on the periphery of the attachment flange19. Preferably, but not restrictively, there are a plurality of outlet orifices24circumferentially distributed around the periphery of the flange19. The oil flows from the inside of the ring gear13to the outside of the latter via the channel or the channels22. Second channels may also allow to evacuate the oil flowing around the external periphery of the ring gear towards the first channels22.

With reference toFIG.4, the turbomachine is also equipped with an oil recovery device which is provided for recovering and rapidly evacuating the oil ejected by centrifugal effect from the reducer6and also from the enclosure E. The recovery device comprises an annular oil recovery gutter30, which is intended to recover the oil ejected from the reducer6. The gutter30, centred on the longitudinal axis X, is arranged around the ring gear13. The gutter30is attached to a stationary structure of the turbomachine (stator). Advantageously, the gutter30is attached to the enclosure E surrounding the reducer. The gutter30has a generally U-shaped axial cross-section. More specifically, the gutter30comprises a bottom wall31from which a first side wall32and a second side wall33extend. The bottom wall31and the side walls32,33are annular and centred on the longitudinal axis X. The side walls32,33extend substantially radially (perpendicular to the longitudinal axis X).

The bottom wall31is arranged radially outside the ring gear13and is oriented facing the oil ejection means. The side walls32,33(referred to as first and second walls) are arranged on either side of the attachment flange19along the longitudinal axis. As can be seen inFIG.4, the gutter30comprises a profiled surface34, here internal, which faces the reducer6and the ring gear13. Each side wall32,33comprises a peripheral edge35defining an internal diameter of the gutter that is smaller than the external diameter of the ring gear13defined by the periphery of the attachment flange19. Also the axis of the attachment members20of the attachment flange19delimits a diameter that is larger than the internal diameter of the peripheral edges35. This configuration allows to avoid the phenomenon of air being sucked from outside the gutter into the gutter. To enhance this advantage, the bottom wall31and the side walls32,33are arranged at a predetermined distance from the attachment flange19, in particular its periphery and attachment members19. These predetermined distances take into account the axial displacements of the ring gear during operation of the reducer, manufacturing tolerances and thermal expansion of the parts.

In the example shown, the gutter30is formed in two portions to facilitate its assembly and its disassembly in the turbomachine. Of course, the gutter can be formed in one part (integral with). The gutter30comprises a first portion30aand a second portion30b. The first portion30acomprises a first tab36, the first side wall32and a bottom wall segment connecting the first tab36and the first side wall32. The second portion30bcomprises a second tab37, the second side wall33and a bottom wall segment connecting the second tab37and the second side wall33. The first and second tabs36,37extend radially outward. In particular, the first and second tabs36,37each comprise a bearing surface defined in a plane, and these planes are parallel. The first portion and the second portion are attached together at the level of the first and second tabs. The tabs36,37are attached to each other by means of attachment members38. The attachment members38comprise screws, nuts, bolts or other suitable member. In this example of embodiment, the first tab35comprises an annular recess36aintended to receive a portion of the second tab37. The internal surface of the bottom wall and side walls segments have a surface continuity and are flush. The first tab36, which is longer than the second tab37, allows the attachment of the gutter30to the stationary structure of the turbomachine.

In another alternative, the gutter30comprises a single radial tab allowing the attachment to the stationary structure of the turbomachine.

The gutter30is made of a metal material. The metal material can be steel or titanium. Advantageously, but not restrictively, the gutter30is made from a sheet-metal to lighten its weight. The walls31,32,33are obtained by folding or welding. The bending and the welding are quick and easy to implement and require very little equipment to manufacture the gutter.

FIG.5shows a first embodiment of a gutter30in which the profiled, internal surface34comprises a hydrophobic and/or lipophobic coating or a surface texturing rendering said surface hydrophobic and/or lipophobic. As used in this description, the terms “hydrophobic” and “lipophobic” (and even “oleophobic”) are used to refer to the ability of a surface to repel water and/or oil from said surface to decrease the contact surface area between the surface and the drop that is formed. Such properties allow to decrease the friction coefficient. The coating or the textured surface allows a smaller coefficient of friction between the surface of the water and/or the oil and the metal surface with the coating. More precisely, the lipophobic and/or hydrophobic character allows the fluid (water/oil/grease) to bead up (pearl shaped) when it is sprayed on the mechanical part, which contributes to a good evacuation of this fluid. Similarly, we also understand by “more lipophobic/hydrophobic” that the surface is less lipophilic/hydrophilic, i.e. the fluid will be less likely to spread/stay on the surface.

The coating or the texturing extends over the entire internal surface of the side walls and of the bottom wall.

FIG.6shows a second embodiment of the gutter30in which only the surface of the side walls32,33comprises a surface coating or texturing. In other words, the surface of the bottom wall is devoid of any coating or texturing.

According to an alternative not shown, the surface coating or texturing thus extends over predetermined areas of the side walls32,33and/or of the bottom wall31. The predetermined areas may correspond to annular strips facing the attachment members38and/or of the attachment flange19. In the case of annular areas provided on the side walls, these would be away from the peripheral edges34of side walls32,33. In the case of the area of the bottom wall, this would be away from the side walls.

FIG.7shows different examples of surface texturing39for the entire surface or certain areas of the surface.

The surface texturing39preferably comprises a surface repetition of hollow or bump patterns of micrometric dimensions. The dimensions can also be in the nanometric range. The patterns can be linear or punctual. The texturing38is advantageously, but not restrictively, made using a material removal micromachining method. An example of a micromachining method is the laser micromachining.

The hollow or bump patterns allow to decrease the surface area of the surface in contact with the fluid containing water and/or oil and thus reduce the friction of the water and/or oil with the surface. In this way, the patterns have the effect of repelling the fluid that flows or displaces faster over the coating or the textured surface.

FIG.8shows an example of hydrophobic/lipophobic coating40intended to coat the internal surface of the side walls and/or the bottom wall or certain predetermined areas thereof.

The hydrophobic and/or lipophobic coating40is preferably made of a polymer, and in particular a fluopolymer such as polytetrafluoroethylene (PTFE). It has for example a thickness between 1 and 100 μm. It can be obtained by spraying a solution on the internal surface of each surface and heating to polymerize and harden the coating.

Thus, the mechanical part, here the oil recovery gutter30, equipped with such a coating40or such a texturing39facilitates the recovery and the evacuation of the oil. The flow is facilitated by the fact that by decreasing the spreading coefficient of the oil, we increase the speed and thus the evacuation flow rate of the gutter. This evacuation is important in particular in the operating or flight phases of the aircraft where the reducer needs a large flow rate of oil, such as during take-off.

The hydrophobic and/or lipophobic coating and the texturing provide the same advantages mentioned above. The advantage of the texturing over the coating is that it does not introduce any pollutants because the coating is likely to degrade during operation and release unwanted elements into the engine.