MECHANICAL COMPONENT FOR THE TURBO ENGINE OF AN AIRCRAFT

Description

Technical field of the invention

[0001] The present invention relates to a mechanical part for an aircraft turbomachine, and in particular a part intended to ensure oil flow during operation. Technical Downstream Plan

[0002] The state of the art includes in particular documents JP-A-2011 112145, JP-A-2011 185322, US-A1-2020 / 309032, WO-A1-2010 / 092263, FR-A1-2 987 416, FR-A1-3 041 054 and FR-A1-3 076 853.

[0003] An aircraft turbomachine consumes oil to operate. This oil is necessary, for example, to lubricate mechanical parts such as bearings or gears, and can also be used to cool these parts. Some mechanical parts of an aircraft turbomachine have profiled surfaces to ensure oil flow during operation. This is the case, for example, with the oil deflectors or collectors of a mechanical gearbox.

[0004] The role of a mechanical reducer is to modify the speed and torque ratio between the input shaft and the output shaft of a mechanical system.

[0005] A mechanical gearbox comprises a central pinion, called the sun gear, a ring gear, and pinions called planet gears, which mesh between the sun gear and the ring gear. The planet gears are held by a frame called the planet carrier. The sun gear, ring gear, and planet carrier are planetary gears because their axes of revolution coincide with the longitudinal X-axis of the turbomachine. The planet gears each have a different axis of revolution and are evenly spaced around the same operating diameter of the planetary gears. These axes are parallel to the longitudinal X-axis.

[0006] Several gearbox architectures exist. In state-of-the-art turbomachinery, gearboxes are of the planetary or epicyclic type. In other similar applications, differential or compound architectures exist. In a planetary gearbox, the planet carrier is fixed, and the ring gear forms the output shaft of the device, rotating in the opposite direction to the sun gear. In an epicyclic gearbox, the ring gear is fixed, and the planet carrier forms the output shaft of the device, rotating in the same direction as the sun gear. In a differential gearbox, no element is fixed in rotation. The ring gear rotates in the opposite direction to both the sun gear and the planet carrier. Gearboxes can be composed of one or more meshing stages. This meshing is achieved in various ways, such as by contact, friction, or magnetic fields. There are several types of contact meshing, such as with spur or herringbone gears.

[0007] The gears in gearboxes are lubricated by oil. The lubricating oil heats up during operation as it absorbs heat energy generated by the gearbox. The oil temperature affects its viscosity and lubrication efficiency. Therefore, it is important to remove the hot oil after lubricating the gearbox for recycling.

[0008] However, once lubricated, the gearbox's satellites project hot oil by centrifugal force onto neighboring satellites. This oil recirculation has several drawbacks: increased losses due to gearbox ventilation, increased satellite temperature, reduced seizing margin, increased oil outlet temperature for heat exchanger sizing, higher air content in the oil, higher oil consumption which lowers the oil level in the reservoir, etc.

[0009] One solution to this problem is to install deflectors or oil collectors between the satellites. Deflectors are designed to divert the oil spray towards oil drainage and recycling facilities. Oil collectors are designed to collect the sprayed oil and convey it to oil drainage and recycling facilities.

[0010] A gearbox oil collector generally comprises a body having two opposing lateral surfaces configured to extend partly around gearbox satellites, the collector may further comprise an internal oil circulation cavity connected on one side to oil inlets located on the lateral faces, and on the other side to at least one oil outlet.

[0011] This collector must efficiently evacuate the oil, otherwise the space between the satellites and the collector will become saturated with oil. This phenomenon results in the satellites bubbling and leads to the same harmful consequences listed previously.

[0012] It is therefore important that the oil flows as quickly as possible over the lateral surfaces of the manifolds and, more generally, over the surfaces of mechanical parts designed to ensure oil flow during operation. Oil that flows too slowly over these surfaces could also be disturbed by the ventilation air circulating through the mechanical gearbox during operation.

[0013] These mechanical parts are generally made of metal. The oil's spreading coefficient on a metallic surface is relatively high, so oil flowing over such a surface tends to spread both on and off the surface. This spreading of the oil is related to the lipophilic nature of the metallic surface.

[0014] The present invention proposes a simple, effective and economical solution, which facilitates the flow of oil on a mechanical part of an aircraft turbomachine. Summary of the invention

[0015] The invention relates to a part as defined in claim 1.

[0016] The surface coating makes the oil flow surface hydrophobic and / or lipophobic. This reduces the oil's spreading coefficient on the surface, thus promoting droplet formation rather than the oil spreading out and forming a film. This facilitates oil flow, preventing it from adhering to the surface and thus accelerating the flow. Accelerating the oil flow on the surface limits the impact of ventilation air on the oil. Furthermore, it can accelerate oil removal and recycling, thereby reducing the amount of oil consumed during turbomachine operation.

[0017] The mechanical part according to the invention may comprise one or more of the following features, taken according to the dependent claims: said surfaces are concave and curved; said coating extends over only part of said surface; said coating extends over the entire surface; the part has two opposing lateral surfaces which are profiled and configured to ensure oil flow in operation, each of these lateral surfaces comprising a hydrophobic and / or lipophobic coating rendering said surface hydrophobic and / or lipophobic; the hydrophobic and / or lipophobic coating is PTFE; the part has an internal oil circulation cavity.

[0018] The invention further relates to a mechanical reducer comprising a mechanical part as described above and a turbomachine, in particular an aircraft turbomachine comprising a mechanical reducer as described above. Brief description of the figures

[0019] 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: [ Fig. 1 ] there figure 1 is a schematic axial cross-sectional view of a turbomachine using the invention, [ Fig. 2 ] there figure 2 is a partial schematic axial cross-sectional view of a mechanical reducer, [ Fig. 3 ] there figure 3 is a schematic cross-sectional view of a mechanical reducer, [ Fig. 4 ] there figure 4 is a schematic perspective view of a mechanical part that is a collector or deflector of a mechanical reducer, [ Fig. 5 ] there figure 5 is a view similar to that of the figure 4 and which shows a mechanical part according to a first embodiment of the invention, [ Fig. 6 ] there figure 6 is a view similar to that of the figure 4and which shows a mechanical part according to a second embodiment of the invention, [ Fig. 7 ] there figure 7 is a very schematic view of examples of surface texturing for a mechanical part, and [ Fig. 8 ] there figure 8 is a very schematic cross-sectional view of a mechanical part according to the invention, some of whose surfaces have hydrophobic and / or lipophobic coatings. Detailed description of the invention

[0020] There figure 1describes a turbomachine 1 which conventionally comprises 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 together form a high-pressure (HP) unit. The low-pressure compressor 1a and the low-pressure turbine 1e are connected by a low-pressure shaft 3 and together form a low-pressure (LP) unit.

[0021] The blower S is driven by a blower shaft 4 which is driven to the BP shaft 3 by means of a reducer 6. This reducer 6 is generally of the planetary or epicycloidal type.

[0022] Although the following description relates to a planetary or epicycloidal type reducer, it also applies to a mechanical differential in which the three components, namely the planet carrier, the ring and the sun gear, are mobile in rotation, the rotational speed of one of these components depending in particular on the difference in speeds of the other two components.

[0023] The gearbox 6 is positioned in the upstream part of the turbomachine. A fixed structure schematically comprising, here, an upstream part 5a and a downstream part 5b which make up the motor or stator housing 5 is arranged to form an enclosure E surrounding the gearbox 6. This enclosure E is closed upstream by seals at the level of a bearing allowing the passage of the blower shaft 4, and downstream by seals at the level of the passage of the BP shaft 3.

[0024] There figure 2Figure 6 shows a reduction gear that can take on different forms depending on whether certain parts are fixed or rotating. At the input, the reduction gear 6 is connected to the shaft BP 3, for example, via internal splines 7a. Thus, the shaft BP 3 drives a planetary gear called the sun gear 7. Typically, the sun gear 7, whose axis of rotation coincides with that of the turbomachine X, drives a series of gears called planet gears 8, which are evenly spaced on 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 planet gears 8. The number of planet gears 8 is generally defined between three and seven for this type of application. The entire set of planet gears 8 is held by a frame called the planet carrier 10. Each planet gear 8 rotates around its own axis Y and meshes with the ring gear 9.

[0025] Our output is: ▪ In an epicyclic configuration, the set of satellites 8 drives the planet carrier 10 in rotation around the X-axis of the turbomachine. The ring gear is fixed to the motor or stator housing 5 via a ring carrier 12, and the planet carrier 10 is fixed to the fan shaft 4. ▪ In a planetary configuration, the set of satellites 8 is held by a planet carrier 10, which is fixed to the motor or stator housing 5.

[0026] Each satellite drives the crown which is brought back to the blower shaft 4 via a crown carrier 12.

[0027] Each satellite 8 is mounted to rotate freely using a bearing 11, for example, a roller bearing or hydrostatic bearing. Each bearing 11 is mounted on one of the axes 10b of the satellite carrier 10, and all the axes are positioned relative to each other using one or more structural frames 10a of the satellite carrier 10. There is a number of axes 10b and bearings 11 equal to the number of satellites. For operational, assembly, manufacturing, inspection, repair, or replacement purposes, the axes 10b and the frame 10a may be separated into several parts.

[0028] For the same reasons mentioned above, the 8d teeth of a gearbox can be separated into several helices, each with a median plane P. In our example, we detail the operation of a multi-helix gearbox with a ring gear separated into two half-ring gears: ▪ An upstream half-crown 9a consisting of a rim 9aa and a mounting flange half 9ab. The upstream helix of the reduction gear teeth is located on the rim 9aa. This upstream helix meshes with that of the satellite gear 8, which meshes with that of the solar gear 7. ▪ A downstream half-crown 9b consisting of a rim 9ba and a mounting flange half 9bb. The downstream helix of the reduction gear teeth is located on the rim 9ba. This downstream helix meshes with that of the satellite gear 8, which meshes with that of the solar gear 7.

[0029] Although the helix widths vary between the solar element 7, the satellite elements 8, and the crown element 9 due to 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 other figures, in the case of a double-row roller bearing, each row of rolling elements is also centered on two median planes.

[0030] The mounting half-flange 9ab of the upstream sprocket 9a and the mounting half-flange 9bb of the downstream sprocket 9b form the mounting flange 9c of the sprocket. The sprocket 9 is fixed to a sprocket carrier by assembling the mounting flange 9c of the sprocket and the mounting flange 12a of the sprocket carrier using, for example, a bolted assembly.

[0031] The arrows of the figure 2describe the oil delivery in the reducer 6. The oil arrives in the reducer 6 from the stator section 5 in the distributor 13 by various means which will not be specified in this view because they are specific to one or more types of architecture. The distributor is divided into 2 parts, generally each repeated with the same number of satellites. The injectors 13a are used to lubricate the gear teeth and the arms 13b are used to lubricate the bearings. The oil is supplied to injectors 13a and exits through ends 13c in order to lubricate, with so-called cold oil (HF), the gear teeth of the satellites 8, the solar element 7 and also the ring gear 9 ( figure 3 The oil is also supplied to the arm 13b and flows through the bearing's supply port 13d. The oil then flows through the shaft into one or more buffer zones 10c and then exits through the ports 10d to lubricate the satellite bearings.

[0032] Due to centrifugal forces, hot oil (Hc) used to lubricate the gears is projected radially outwards relative to the Y axes of the satellites, as shown in the diagram. figure 3 To prevent this oil from interfering with the lubrication of the adjacent satellites 8, oil collectors 20 are arranged between the satellites 8. Although the figure 3 represents a single collector 20, the reducer includes a collector between two adjacent satellites and therefore includes as many collectors as satellites, namely four in the example shown.

[0033] There figure 4 shows an example of the construction of an oil collector 20.

[0034] The collector 20 comprises a body, here a single piece, which has two opposing lateral surfaces 20a designed to extend partially around two adjacent satellites 8. These lateral surfaces 20a advantageously have a concave curved shape whose radius of curvature can be centered on the Y axis of rotation of the satellite 8 to which this surface 20a faces.

[0035] The collector 20 further includes an upper face 20b or radially external, here flat, intended to extend in relation to the ring 9 or to a wall of a cage in the case where the solar 7 and the satellites 8 of the reducer 6 are arranged in a cage.

[0036] The collector 20 further includes a lower face 20c or radially internal, here flat, intended to extend in relation to the solar 7.

[0037] Finally, the manifold 20 comprises two faces 20d, respectively upstream and downstream. As in the example shown, one of these faces 20d may include a fixing element 22 for the reducer.

[0038] The opposite face 20d of the manifold 20 may include a common oil outlet 26, which may be, for example, a tubular fluid connection fitting. This fitting may be configured to pass through a passage in the gearbox housing, for example. The manifold 20 further includes an internal (not visible) oil circulation cavity connected to the oil outlet 26 and to at least one oil inlet 30 located here on face 20b.

[0039] There figure 5 shows a first embodiment of the invention in which a part of each surface 20d comprises a hydrophobic and / or lipophobic coating rendering said surface hydrophobic and / or lipophobic.

[0040] In this description, we use the terms "hydrophobic" and "lipophobic" (and even "oleophobic") to refer to a surface's ability to repel water and / or oil, thereby reducing the contact area between the surface and the resulting droplet. Such properties lower the coefficient of friction. The coating allows for a lower coefficient of friction between the water and / or oil surface and the metallic surface with the coating. More specifically, the lipophobic and / or hydrophobic nature of the coating allows the fluid (water / oil / grease) to bead up (form beads) when it comes into contact with the mechanical part, thus contributing to efficient fluid removal. Similarly, we also understand "more lipophobic / hydrophobic" to mean that the surface is less lipophilic / hydrophilic, in other words, the fluid will be less likely to spread or remain on the surface.

[0041] The coating extends over a zone Z1 which has an elongated band shape. In the example shown, zone Z1 is located in the middle of each surface 20d and extends at a distance from faces 20d and from face 20c to face 20b.

[0042] There figure 6 This shows a second embodiment of the invention in which the entirety of each surface 20d comprises a hydrophobic and / or lipophobic coating. This coating extends over an area Z2 which corresponds to the entirety of each surface 20d. The area Z2 extends to the faces 20d and to the faces 20c and 20b.

[0043] There figure 7 shows examples of surface texturing 32 for zones Z1 and Z2, which are not relevant to the invention.

[0044] Surface texturing 32 preferably comprises a surface repetition of micrometer-sized indentations or bumps. The patterns can be linear or point-like. This texturing 32 is, for example, produced by laser micromachining. The indentations or bumps reduce the surface area in contact with the oil and thus decrease the friction between the oil and the surface.

[0045] There figure 8 shows an example of hydrophobic and / or lipophobic coating 34 for zones Z1 and Z2.

[0046] The coating 34 is preferably made of polymer, and in particular PTFE. It has, for example, a thickness between 1 and 100 µm. It can be obtained by spraying a solution onto each surface 20d and heating it to polymerize and harden the coating. The coating 34 offers the same advantages mentioned above.

Claims

1. A mechanical part for an aircraft turbomachine, this mechanical part being made of metal and comprising at least one profiled surface (20a) configured to ensure an oil flow during operation, the part being an oil deflector or collector (20) for a mechanical reduction gear (6), characterized in that said surface comprises a coating (34) made of polymer more hydrophobic and / or lipophobic than said surface.

2. The mechanical part of claim 1, wherein said surface (20a) is concave curved.

3. The mechanical part of claim 1 or 2, wherein said coating (34) extends over only a portion of said surface (20a).

4. The mechanical part according to claim 1 or 2, wherein said coating (34) extends over the entirety of said surface (20a).

5. The mechanical part according to any of claims 1 to 4, comprising two opposing side surfaces (20a) which are profiled and configured to ensure an oil flow during operation, each of these side surfaces comprising a hydrophobic and / or lipophobic coating (34) rendering said surface hydrophobic and / or lipophobic.

6. The mechanical part according to any of claims 1 to 5, wherein the hydrophobic and / or lipophobic coating (34) is made of PTFE.

7. The mechanical part according to any of claims 1 to 6, comprising an internal oil circulation cavity (28).

8. A mechanical reduction gear (6) for an aircraft turbomachine, comprising a sun gear (7), a ring gear (9) extending around the sun gear, planet gears (8) meshed with the sun gear (7) and the ring gear (9), and a mechanical part according to one of the preceding claims, the mechanical part having said surface (20a) arranged facing a planet gear so as to form an oil deflector.

9. A turbomachine (1), in particular for an aircraft, comprising mechanical reduction gear (6) according to claim 8.