LOW-NOISE MECHANICAL REDUCTION GEAR SATELLITE SLIDING BEARING

Description

Technical field of the invention

[0001] The invention relates to a plain bearing for a satellite of a mechanical turbomachine reducer, and a mechanical reducer comprising such a plain bearing. Technical background

[0002] The state of the art includes in particular documents WO-A1-2010 / 092263, FR-A1-2 987 416, FR-A1-3 041 054, FR-A1-3 071 022, FR-A1-3 071 023, FR-A1-3 071 023 and FR-A1-3 095 252-A1.

[0003] 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.

[0004] Newer generations of turbomachinery, particularly high-bypass turbomachinery, incorporate a mechanical gearbox to drive the fan shaft. Typically, the gearbox's purpose is to transform the high rotational speed of the turbine shaft into a slower rotational speed for the fan shaft.

[0005] Such a reduction gear 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 Y-axis of revolution, and they are evenly spaced around the same operating diameter of the planetary gears. These Y-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.

[0007] Gearboxes can have 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. A gearbox must be lubricated, and supplying lubricating oil to the rotating components of a gearbox can be problematic. The oil is generally supplied to the gearbox by a lubricating oil distributor.

[0008] The satellites are guided in rotation by lubricated bearings. The bearings can be composed of rolling elements (ball bearings, roller bearings, tapered roller bearings, etc.) or can be plain or hydrodynamic bearings.

[0009] In this latter case, each satellite is rotatably mounted on and around a plain bearing, which is supplied with oil by the distributor and is configured to form an oil film between the outer periphery of the bearing and the inner periphery of the satellite. To achieve this, in the current technique, each satellite comprises an internal cylindrical surface extending around an external cylindrical surface of the bearing, defining with it an annular space for oil film formation. This space is supplied with oil through oil passages formed in a bore of the bearing and extending from the external cylindrical surface to a central bore of the bore, which is supplied with oil by the aforementioned distributor.

[0010] Plain bearings are substantial components of the gearbox, typically numbering between three and seven. The greater the mass of the bearings, the greater its impact on the gearbox's weight, and therefore, the weight of the motor. Furthermore, the greater the mass of the bearings, as they orbit around the motor's (planetary) axis, the greater the potential for adverse consequences such as imbalance, high-amplitude vibrations, and radial forces on the planet carrier, which can lead to misalignment between the sun gear, the planets, and the corona. In addition, the greater the mass of the bearings, the more susceptible they are to shearing the oil film between the bearing and the planet, due to the centrifugal forces they are subjected to. This results in friction losses at the points where the oil film breaks.

[0011] To limit the mass of each bearing, it has been classically proposed to lighten them.

[0012] As is known, each bearing has an axial annular shaft that defines a central bore centered on the shaft's axis. The shaft has annular grooves that extend around its axis and open axially in opposite directions to the shaft's axial ends. Each annular groove is defined by two coaxial walls, internal and external to the shaft, connected by a transverse bottom wall that has at least one opening leading into a cavity formed in the shaft between the central bore and the shaft's periphery.

[0013] The barrel may have multiple openings, which can be regularly distributed around the central bore. The cavities can be arranged as extensions of the openings, for example, as nearly straight cylindrical channels or axes inclined relative to the axis of the central bore, obtained by drilling or molding. The channels may pass through the bearings along their entire length or, conversely, be blind. The cavities can also be larger than the openings and form pockets within the barrel, particularly if they are formed by molding. In any case, the cavities allow for a reduction in the barrel's weight.

[0014] Advantageously, the inner and outer walls of each groove provide flexibility to the axial ends of the bearing and limit bearing deformation, thus ensuring good radial alignment of the satellite gear teeth with the central pinion and the outer ring gear.

[0015] However, it has been observed that the presence of cavities is a significant source of noise when the bearings are rotating due to the rotation of the planet carrier.

[0016] It is therefore necessary to limit the noise generated by the rotation of the bearings accompanying the satellite carrier. Summary of the invention

[0017] The invention remedies the aforementioned drawback by at least partially sealing each cavity.

[0018] To this end, the invention proposes a plain bearing for a satellite of a mechanical turbomachine reducer, the plain bearing having an annular shaft of axis Y which delimits at least one central bore centered on the axis Y, and the shaft having annular grooves which extend around the axis Y and which open axially in opposite directions to the axial ends of the shaft, each annular groove being delimited by two internal and external walls of the shaft connected by a transverse bottom wall which has at least one opening which opens into a cavity which is formed in the shaft between said at least one central bore and a periphery of the shaft, characterized in that each cavity is closed by a sealing means.

[0019] Sealing the cavities prevents air or oil from entering them, thus eliminating any source of noise. However, it also allows for a reduced-mass plain bearing due to the presence of the cavities. Other bearing characteristics may also apply. The sealing means is a closing plate that extends in contact with the bottom wall across said at least one opening; the sealing means is a filling material that is introduced into said cavity and fills it at least partially; each cavity is closed by a plug that is received in the corresponding opening and at least partially in said cavity; each cavity is a cylindrical conduit, in particular a bore, which opens through its opening into the bottom wall, and each plug comprises a cylindrical body that has a diameter corresponding to a diameter of said cylindrical conduit and that is received in said conduit; the plug has at one end of its cylindrical body a head that has a cross-section greater than the diameter of said cylindrical conduit and that is adapted to bear against the bottom wall; the plug is fitted, crimped, crimped or glued into the opening and / or into the cavity.The cylindrical body of the plug has a thread, and said body is screwed into a complementary threaded hole formed in the cylindrical conduit; the plug is made of steel, aluminum, or a thermoplastic material.

[0020] The invention also relates to a mechanical reducer of a gas turbomachine for aircraft, comprising an outer ring gear and satellite gears in mesh with the central pinion and with the outer ring gear and each mounted freely in rotation on a satellite carrier, the satellite gears each being able to rotate around a satellite axis by means of a plain bearing of the type described above. Brief description of the figures

[0021] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for an understanding of which reference should be made to the attached drawings in which: [ Fig. 1 ] there figure 1is a schematic axial cross-sectional view of a turbomachine using the invention, [ Fig. 2 ] there figure 2 is a partial axial cross-sectional view of a mechanical reducer according to the prior art, [ Fig. 3 ] there figure 3 is seen as similar to that of the figure 2 and representing an embodiment of a mechanical reducer comprising plain bearing satellites according to the prior art, [ Fig. 4 ] there figure 4 is a perspective view of a plain bearing of a reducer according to the invention, [ Fig. 5 ] there figure 5 is a cross-sectional view of the plain bearing of the figure 4 , [ Fig. 6 ] there figure 6 is a detailed cross-sectional view of the plain bearing of the figure 6 , And [ Fig. 7 ] there figure 7 is a perspective view of a plug for a plain bearing according to the invention. Detailed description of the invention

[0022] There figure 1This describes a turbomachine 10 with X-axis which conventionally comprises a fan 12, a low-pressure compressor 14, a high-pressure compressor 16, an annular combustion chamber 18, a high-pressure turbine 20, a low-pressure turbine 22, and an exhaust nozzle 24. The high-pressure compressor 16 and the high-pressure turbine 20 are connected by a high-pressure shaft 26 and together form a high-pressure (HP) unit. The low-pressure compressor 14 and the low-pressure turbine 20 are connected by a low-pressure shaft 28 and together form a low-pressure (LP) unit.

[0023] The blower 12 is driven by a blower shaft 30 which is driven by the BP shaft 28 by means of a reducer 32. This reducer 32 is generally of the planetary or epicycloidal type.

[0024] The following description concerns an epicycloidal type reducer, whose planet carrier and sun gear are mobile in rotation, the ring gear of the reducer being fixed in the frame of reference of the motor.

[0025] The gearbox 32 is positioned in the upstream part of the turbomachine. In this application, the terms upstream and downstream refer to the general gas flow in the turbomachine, along its axis of extension or rotation of its rotors.

[0026] A fixed structure schematically comprising, here, an upstream part 34 and a downstream part 36 which make up the motor or stator housing 38 is arranged to form an enclosure 40 surrounding the reducer 32. This enclosure 40 is here closed upstream by seals at the level of a bearing allowing the passage of the blower shaft 30, and downstream by seals at the level of the passage of the BP shaft 28.

[0027] There figure 2Figure 32 shows an epicyclic gearbox. At the input, the gearbox 32 is connected to the shaft BP 28, for example, via internal splines 42a. Thus, the shaft BP 28 drives a central planetary gear 42, also called the sun gear. Typically, the sun gear 42, whose axis of rotation coincides with that of the turbomachine X, drives a series of gears called sun gears 44, which are evenly spaced around the same diameter around the axis of rotation X. This diameter is equal to twice the operating center distance between the sun gear 42 and the sun gears 44. The number of sun gears 44 is generally between three and seven for this type of application.

[0028] The set of satellites 44 is held by a frame called a satellite carrier 46. Each satellite 44 rotates around its own Y axis, and meshes with a ring gear 54.

[0029] Our output is: In this epicyclic configuration, the set of planet gears 44 drives the planet carrier 46 in rotation around the X-axis of the turbomachine. The ring gear 54 is fixed to the motor or stator housing 38 via a ring carrier 50, and the planet carrier 46 is fixed to the fan shaft 30. In another planetary configuration, the set of planet gears 44 is held by a planet carrier 46, which is fixed to the motor or stator housing 38. Each planet gear 44 drives the ring gear 54, which is connected to the fan shaft 30 via a ring carrier 50.

[0030] Each satellite 44 has an internal bearing surface 52 which is mounted to rotate freely by means of a plain bearing 46b, which is a rolling or hydrodynamic bearing type. Each plain bearing 46b is fixed to the satellite carrier 46, and all the plain bearings 46b are positioned relative to each other by means of one or more structural frames 46a of the satellite carrier 46. There is a number of plain bearings and internal bearing surfaces 52 equal to the number of satellites. For reasons of operation, assembly, manufacturing, inspection, repair, or replacement, the bearings 46b and the frame 46a can be separated into several parts.

[0031] For the same reasons mentioned previously, the teeth of a reduction gear can be separated into several helices, each with a median plane P. In our example, we detail the operation of a multi-helix reduction gear with a ring gear 54 divided into two half-rings 54a and 54b: An upstream half-ring 54a consisting of a rim 54aa and a mounting flange half 54ab. The upstream helix of the reduction gear teeth is located on the rim 54aa. This upstream helix meshes with that of the satellite gear 44, which meshes with that of the solar gear 42.

[0032] A downstream half-crown 54b consisting of a rim 54ba and a mounting flange half 54bb. The downstream helix of the reduction gear teeth is located on the rim 54ba. This downstream helix meshes with that of the satellite 44, which in turn meshes with that of the solar 42.

[0033] Although the helix widths vary between the solar element 42, the satellite elements 44, and the crown element 54 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 case of a double-row roller bearing, each row of rolling elements is also preferably, but not necessarily, centered on two median planes.

[0034] The mounting half-flange 54ab of the upstream crown 54a and the mounting half-flange 54bb of the downstream crown 54b form the mounting flange 54c of the crown. The crown 54 is fixed to a crown carrier by assembling the mounting flange 54c of the crown and the mounting flange 50a of the crown carrier 50 using, for example, a bolted assembly.

[0035] The arrows of the figure 2The diagram describes the oil delivery within the gearbox 32. The oil enters the gearbox 32 from the stator section 38 via a distributor 60 by various means, which will not be detailed in this view as they are specific to one or more types of architecture. The distributor 60 comprises injectors 60a and arms 60b. The injectors 60a lubricate the gear teeth, and the arms 60b lubricate the bearings. The oil is supplied to injector 60a and exits through end 60c to lubricate the gear teeth.

[0036] The oil is also supplied to the arm 60b and flows through the supply port 60d of the bearing 46b. The oil then flows through the plain bearing 46b into one or more bores 46c and then exits through channels 46d to lubricate the internal bearing surfaces 52 of the satellites 44.

[0037] There figure 3represents another mechanical reducer 32 comprising satellites 44 mounted on hydrodynamic bearings or plain bearings known from the prior art. In this example, the plain bearing 46b and the structural frame 46a are in two parts.

[0038] The plain bearing 46b of each satellite 42 includes a monobloc annular shaft 64 in the example shown here which has two coaxial external annular walls 62a and internal annular walls 62b which extend around each other and are connected to each other by a transverse bottom wall 62c.

[0039] The internal annular wall 62b and the bore 46c are closed by a partition 62d and have on the opposite side an axial end 62e open on the opposite side to receive in the bore 46c lubricating oil supplied by the oil distributor (not shown).

[0040] The plain bearing 46b includes channels 46d for conveying lubricating oil from the bore 46c to the outer periphery of the bearing 46b. The coaxial annular walls 62a, 62b define annular grooves 66a, 66b. This configuration provides a degree of flexibility to the bearing 46b at each of its axial ends.

[0041] The bearing 46b thus comprises a first annular groove 66a located on one side and whose opening is axially directed, and a second annular groove 66b located on the opposite side of the bearing and whose opening is axially directed opposite to groove 66a. These grooves 66a, 66b have a general U-shaped cross-section.

[0042] THE figures 4 to 6represent more particularly a plain bearing 46b according to the invention. By way of non-limiting the latter, the plain bearing 46b comprises two bores 46c, one of which is closed by a partition 62d, and which are separated by a transverse wall 46e in which is formed one of the conduits 46d, a T-shaped branch 46f of which connects the two bores 46c so that they communicate with each other.

[0043] On each side of the shaft 64, each transverse bottom wall 62c has at least one opening 68 which leads into a cavity 70 which is formed in the shaft 64, radially between said at least one central bore 46c and a periphery 72 of the shaft 64. In the example which has been shown in the figure 5 The shaft 64 comprises a single cavity 70, common to pairs of opposing openings 68 aligned along a Y axis parallel to the X axis. This configuration is not limiting to the invention and, as illustrated by the figure 6, the 68 openings could communicate with 70 blind cavities not communicating with each other.

[0044] In the example shown here, each cavity 70 is a cylindrical conduit, which opens through its aperture 68 into the bottom wall 62c. The cylindrical conduit can be obtained by molding or by drilling, and therefore the aperture 68 is circular and of the same diameter as the conduit forming the cavity 70.

[0045] It will be understood that this configuration is not limiting to the invention. The cavity 70 is not necessarily cylindrical and can take any shape aimed at lightening the barrel 64. For example, the cavity 70 could form a pocket in the barrel material, with dimensions larger than those of the opening 68. The opening 68 could also be non-circular, without limiting the invention.

[0046] The cavities 70 make it possible to lighten the barrel 64. However, it has been observed that the presence of the cavities 70 is a significant source of noise when the bearings 46b are rotating due to the rotation of the planet carrier.

[0047] According to the invention, to remedy this drawback, each cavity 70 is closed by a sealing means 76.

[0048] According to a first embodiment of the invention which has not been shown in the figures, the closing means could be a closing plate which would extend in contact with the bottom wall 62c across said at least one opening 68. In particular, such a plate could be annular and fit the bottom wall 62c by being housed in the grooves 66a, 66b to cover all the openings.

[0049] According to a second embodiment of the invention, which is not shown in the figures, the sealing means could be a filling material introduced through the opening 68 into the cavity 70, at least partially filling it. The material can be solidified in the cavity 70 to prevent it from escaping. Preferably, the filling material is injected, poured, or molded into the cavity 70.

[0050] According to a third embodiment of the invention, which has been shown in the figures 5 to 7 , each cavity is closed by a plug forming the obturation means 76 which is received in the corresponding opening 68 and at least partly in the cavity 70.

[0051] The plug 76 is designed to fit the opening 68. For this purpose, it is either of the same cross-section as the opening 68 or is deformable and expandable so that it can be inserted into it and expand, thus closing the opening 68.

[0052] As we have seen, in the example referring to Figures 5 And 6 Each cavity 70 is a cylindrical conduit, which opens through its opening 68 into the bottom wall 62c. In this configuration, as can also be seen in the figure 7 , each plug 76 comprises a cylindrical body 78 which has a diameter corresponding to a diameter of the cylindrical conduit 70 and which is received in said conduit.

[0053] To limit the penetration of the plug 76 into the cavity 68, it has at one end of its cylindrical body 78 a head 80 which has a cross-section greater than a diameter of the cylindrical conduit 70 and which is able to bear against the bottom wall 62c.

[0054] The plug 76 is preferably immobilized in the opening 68. Also, whatever its method of embodiment, the plug 76 is fitted, crimped, crimped or glued into the opening 68 and / or into the cavity 70.

[0055] When cavity 70 is cylindrical as shown in Figures 5 And 6 The cylindrical body 78 of the plug 76 may have a thread and be screwed into a complementary thread formed in the cylindrical conduit 70. In this case, it will be understood that the head 80 of the plug may have a complementary impression of a screwing tool.

[0056] The 76 plug is made of steel, aluminum, or a thermoplastic material. It can also be made of foam, which has the advantage of absorbing lubricating oil to ensure the seal of the 76 plug.

[0057] The invention thus provides a reduction gear 32 for an aircraft gas turbomachine, such as a planetary or epicyclic type reduction gear 32, comprising an outer ring gear 54 and planet gears 44 meshing with a central pinion 42 and with the outer ring gear 54, each freely rotatable on a planet carrier 46. Each of the planet gears 44 can rotate about a planet Y-axis via a bearing 46b of the type described previously. Such a reduction gear 42 offers significantly quieter operation compared to known prior art reduction gears.

Claims

1. A plain bearing (46b) for a planet gear (44) of a turbomachine mechanical reduction gear (32), the plain bearing (46b) having an annular barrel (64) with an axis (Y) which delimits at least one central bore (46c) centred on the axis (Y), and the barrel (64) having annular grooves (66a, 66b) which extend around the axis (Y) and which open axially in opposite orientations at the axial ends of the barrel (64), each annular groove (66a, 66b) being delimited by two internal (62b) and external (62a) walls of the barrel (64) connected by a transverse bottom wall (62c) which has at least one opening (68) which opens into a cavity (70) which is formed in the barrel (64) between said at least one central bore (46) and a periphery (72) of the barrel (64), characterised in that each cavity (70) is closed by a sealing means (76).

2. The plain bearing (46b) according to claim 1, characterised in that the sealing means (76) extends in contact with the bottom wall (62c) across said at least one opening (68).

3. The plain bearing (46b) as claimed in claim 1, characterised in that the sealing means (76) comprises a filling material which is introduced into said cavity (70) and at least partially fills it.

4. The plain bearing (46b) according to claim 1, characterised in that each cavity (70) is closed by a plug forming the sealing means (76) which is received in the corresponding opening (68) and at least partly in said cavity (70).

5. The plain bearing (46b) according to the preceding claim, characterised in that each cavity (70) is a cylindrical duct, in particular a drilling, which opens out via its opening (68) into the bottom wall (62c), and in that each plug (76) comprises a cylindrical body (78) which has a diameter corresponding to a diameter of said cylindrical duct (70) and which is received in said duct (70).

6. The plain bearing (46b) according to the preceding claim, characterised in that the plug (76) comprises, at one end of its cylindrical body (78), a head (80), a cross-section of which is greater than the diameter of said cylindrical duct (70) and which is capable of bearing against the bottom wall (62c).

7. The plain bearing (46b) according to one of claims 4 to 6, characterised in that the plug (76) is fitted, shrunk, crimped or glued in the opening and / or in the cavity.

8. The plain bearing (46b) according to one of claims 5 or 6, characterised in that the cylindrical body (78) of the plug (76) comprises a thread and in that said body (78) is screwed into a complementary tapping formed in the cylindrical duct (70).

9. The plain bearing (46b) according to one of claims 4 to 8, characterised in that the plug (76) is made of steel, aluminium or a thermoplastic material.

10. A mechanical reduction gear (32) for an aircraft gas turbomachine, comprising an outer ring gear (54) and planet gear pinions (44) engaged with a central pinion (42) and with an outer ring gear (54) and each mounted to rotate freely on a planet carrier (46), the planet gear pinions (44) each being rotatable about a planet gear axis via a plain bearing (46b) according to any one of claims 1 to 9.