SMOOTH BEARING FOR AN AIRCRAFT TURBOMACHINE

Abstract

Plain bearing (11) for an aircraft turbomachine, this plain bearing (11) comprising a tubular body (10b) including: - an external cylindrical surface (20aa), - an internal cavity (10c) for containing oil, - a main lubrication groove (24) which is formed on a median part (20aa1) of the external surface (20aa), and - a main oil supply channel (10d) for the main groove (24), characterized in that the external surface (20aa) of the body (10b) further includes at least one secondary lubrication groove (26) which is formed on an end part (20aa2, 20aa3) of the external surface (20aa) and which is independent of the main groove (24), and in that the body (10b) further includes a secondary oil supply channel (27) for the or each secondary groove (26). Figure for the summary: Figures 6a-6c

Description

Title of the invention: PLAIN BEARING FOR AN AIRCRAFT TURBO MACHINE Technical field of the invention

[0001] The present invention relates to a plain bearing for an aircraft turbomachine, as well as a mechanical reducer comprising this type of plain bearing. Technical background

[0002] The state of the art includes in particular documents FR-A1-2 995 055, FR-Al-3 071 022 and WO-A1-2014 / 037659.

[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 mechanical system.

[0004] New generations of multiflow turbomachinery, particularly those with a high bypass ratio, include a mechanical gearbox to drive the shaft of a fan or propeller. Typically, the gearbox's purpose is to transform the high rotational speed of the power turbine shaft into a slower rotational speed for the shaft driving the fan or propeller.

[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 a planet carrier. The sun gear, ring gear, and planet carrier are planetary 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, equally spaced on the same operating diameter around the axis of the planetary gears. These axes are parallel to the longitudinal axis X.

[0006] Several gearbox architectures exist. In the state of the art of multi-flow turbomachinery, gearboxes are of the planetary or epicyclic type. In other similar applications, there are so-called differential or "compound" architectures.

[0007] - on a planetary reducer, the planet carrier is fixed and the ring constitutes the output shaft of the device which rotates in the opposite direction to the solar.

[0008] - on an epicyclic reducer, the ring gear is fixed and the planet carrier constitutes the output shaft of the device which rotates in the same direction as the solar panel.

[0009] - on a differential reducer, no element is fixed for rotation. The ring rotates in the opposite direction to the solar panel and the satellite carrier.

[0010] Reducers can be composed of one or more meshing stages. This meshing is achieved in various ways such as by contact, by friction, or by magnetic fields. There are several types of contact meshing such as with straight or herringbone teeth.

[0011] Satellites are guided in rotation by bearings, which may be plain bearings or roller bearings. This application relates to a plain bearing that can be used for guiding a satellite or any other mechanical element of a turbine. In this application, plain bearing and hydrodynamic bearing have the same meaning.

[0012] A plain or hydrodynamic bearing comprises a tubular body whose internal cavity is supplied with lubricating oil. The oil supplies the internal cavity and is conveyed through a supply channel to a main lubrication groove formed on an external cylindrical surface of the body.

[0013] The main lubrication groove is located on a median part of the external surface of the body and has a straight and elongated shape along the main axis of the plain bearing which is the axis of revolution of its cylindrical surface.

[0014] In the case of a satellite guidance system, the satellite comprises an internal cylindrical surface extending around the external surface of the bearing body. In its normal operating position, the internal surface of the satellite covers and closes the lubrication groove. However, during operation, the satellite can move axially on the plain bearing. During these movements, the satellite can adopt an axial position on the plain bearing in which the internal surface of the satellite no longer covers one longitudinal end of the lubrication groove, which is therefore no longer closed. The oil contained in the groove then escapes at a significant and uncontrolled rate. The movement of the satellite on the plain bearing thus raises concerns about substantial oil leaks at the bearing and consequently excessive oil consumption.

[0015] One solution to this problem could be to reduce the length of the feed groove to prevent it from being exposed during the relative movements of the planet gear and the plain bearing. However, this solution would not be satisfactory because it would not guarantee effective lubrication of the bearing. The longitudinal ends of the bearing might not be sufficiently lubricated, which could lead to contact seizure between the planet gear and the bearing, and reduce the bearing's service life.

[0016] The present invention proposes a solution to this problem of the prior art, which is simple, effective and economical. Summary of the invention

[0017] The invention relates to a plain bearing for an aircraft turbomachine, this plain bearing comprising a tubular body with a main axis and comprising:

[0018] - an external cylindrical surface extending around the axis over a major part of an axial dimension of the body,

[0019] - two tubular mounting ends located respectively at two ends opposites of the body along the axis,

[0020] - an internal cavity intended to receive oil and opening at the center of at least one of the tips,

[0021] - a main lubrication groove that is cut into the external surface of a the middle part of the body, which has an elongated shape along its axis, and

[0022] - a main oil supply channel for the main groove, which ensures a fluidic communication between the cavity and the main groove,

[0023] characterized in that the body comprises two opposite end parts separated from each other by the middle part of the body, at least one of these end parts having a secondary lubrication groove which is cut into the external surface and which has an elongated shape along the axis and which is fluidly independent of the main groove,

[0024] and in that the body further comprises a secondary oil supply channel to the or each secondary groove, which ensures fluidic communication between the cavity and the secondary groove.

[0025] The plain bearing thus comprises a primary lubrication groove and at least one secondary lubrication groove. The primary and secondary grooves are independent, meaning they do not communicate with each other and are supplied by separate channels. The primary groove extends along the middle portion of the housing, and each secondary groove extends along an end portion of the housing, thus allowing lubrication of a major portion of the external surface length of the housing during operation. Furthermore, if a planetary gear, for example, moves on the plain bearing, the secondary groove, or one of the secondary grooves, may no longer be covered by the planetary gear. Oil will then escape and leak from the secondary groove.However, because this secondary groove is fed by a channel with a smaller cross-section than the main groove's feed channel, the oil will escape at a lower rate. Most of the bearing's oil supply will continue to feed the main groove, and only a small portion will leak through the exposed secondary groove. This reduced cross-section helps maintain sufficient pressure within the bearing's internal cavity to ensure oil supply to the main groove, thus reducing the risk of seizing.

[0026] The invention thus makes it possible to guarantee the supply of oil to the main groove and to limit oil leaks at the longitudinal ends of the plain bearing during relative movements between the plain bearing and the element it guides.

[0027] The invention is compatible with a single-stage or multi-stage gearbox. It is compatible with an epicyclic, planetary, or differential gearbox. It is compatible with herringbone gears, in particular. Finally, it is compatible with any type of planet carrier, whether monobloc or cage-type.

[0028] The plain bearing according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0029] — the body of the plain bearing is a single piece

[0030] - said secondary channel has a minimum passage cross-section smaller than that of the channel main ;

[0031] - the main and secondary groove(s) are straight and parallel;

[0032] - the secondary groove or grooves have a longitudinal dimension smaller than that of the main groove, and preferably less than half the size of the main groove;

[0033] - the one or each secondary groove extends into the outer surface of the middle part of the body to create a zone of mutual overlap with the main groove;

[0034] - the main channel is free of restrictor;

[0035] - the secondary channel or each secondary channel includes a restrictor which is reported and fixed onto the body; in this application, a (fluid) restrictor is understood to be a device which is used to reduce the cross-sectional area through which a fluid passes; a restrictor allows the passage of fluid but in a limited or controlled manner; in the case of an aircraft turbomachine, a restrictor is housed in a bore of a part in order to control the amount of fluid passing through that bore, for example;

[0036] - the main channel is located substantially in the middle of the main groove, and the secondary channel is located at one longitudinal end of the or each secondary groove, this longitudinal end being located on the side of the main groove;

[0037] - the bearing comprises a main groove and two secondary grooves, the two secondary grooves being axially aligned with each other and being located at a predetermined distance from the main groove;

[0038] - the distance is less than or equal to a width of the main groove.

[0039] The present invention also relates to an assembly comprising a plain bearing according to one of the preceding claims, and a mechanical gearbox satellite, this satellite comprising a tubular body having a main axis and comprising:

[0040] - at least one external toothing extending around the axis, and

[0041] - an internal cylindrical surface extending around the axis over a major part of an axial dimension of the body, this internal surface being intended to extend around the external surface of the body of the plain bearing.

[0042] Advantageously, the internal surface of the satellite body has a length less than that of the external surface of the plain bearing body, and in which the main and secondary groove(s) extend over a longitudinal dimension of the plain bearing body which is between 95%.L1 and 99%.L1, L1 being the length of the internal surface of the satellite body.

[0043] The present invention also relates to a mechanical turbomachine reducer, in particular for aircraft, comprising a solar, a crown extending around the solar, and assemblies as described above, the satellites of these assemblies being meshed with the solar and the crown.

[0044] The invention further relates to a turbomachine, in particular for aircraft, comprising a mechanical reducer as described above. Brief description of the figures

[0045] 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:

[0046] [Fig. 1] [Fig. 1] is a schematic axial cross-sectional view of a turbomachine using the invention,

[0047] [Fig.2] [Fig.2] is a partial schematic axial cross-sectional view of a reducer mechanical,

[0048] [Fig.3] [Fig.3] is a schematic perspective view and axial section of a bearing smooth and a satellite of a mechanical reducer,

[0049] [Fig.4] [Fig.4] is a schematic perspective view of the plain bearing of [Fig.3],

[0050] [Fig. 5a-5c] Figures 5a-5c are very schematic half-views in axial section of a plain bearing and a satellite according to the prior art, and illustrate different axial positions of the satellite on the plain bearing,

[0051] [Fig. 6a-6c] Figures 6a-6c are very schematic half-views in perspective and in axial section of a plain bearing and a satellite according to the invention, and illustrate different axial positions of the satellite on the plain bearing,

[0052] [Fig.7] [Fig.7] is a larger-scale view of part of Figure 6c,

[0053] [Fig.8] [Fig.8] is an even larger scale view of part of the figure 6c,

[0054] [Fig. 9a-9c] Figures 9a-9c are views similar to those of Figures 6a-6c and illustrate different axial positions of the satellite on the plain bearing within the framework of the present invention. Detailed description of the invention

[0055] Figure 1 describes a turbomachine 1 which conventionally comprises a blower S, a low-pressure compressor 1a, a high-pressure compressor 1b, a The assembly consists of an annular combustion chamber, a high-pressure turbine (Id), a low-pressure turbine (le), and an exhaust nozzle (Ih). The high-pressure compressor (1b) and the high-pressure turbine (Id) are connected by a high-pressure shaft (2) and together form a high-pressure (HP) unit. The low-pressure compressor (la) and the low-pressure turbine (le) are connected by a low-pressure shaft (3) and together form a low-pressure (LP) unit.

[0056] 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.

[0057] 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 crown 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.

[0058] The reducer 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 reducer 6. This enclosure E is here 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.

[0059] Figure 2 shows a gearbox 6 which can take the form of different architectures depending on whether certain parts are fixed or rotating. At the input, the gearbox 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. Conventionally, 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 equally 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.

[0060] The set of satellites 8 is held by a frame called a satellite carrier 10. Each satellite 8 rotates around its own Y axis, and meshes with the ring 9.

[0061] The output we have: • 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 satellite carrier 10 which is fixed to the motor or stator housing 5. Each satellite drives the crown which is brought to the blower shaft 4 via a crown carrier 12.

[0062] Each satellite 8 is mounted to rotate freely by means of a bearing 11, for example, a rolling bearing or hydrodynamic plain bearing. In the case of a plain bearing, the bearing 11 comprises a tubular body 10b, and the tubular bodies of the various plain bearings are positioned relative to one another and are supported by a structural frame 10a of the satellite carrier 10. There is a number of bearings 11 equal to the number of satellites 8. For reasons of operation, assembly, manufacturing, inspection, repair, or replacement, the bearings 11 (and in particular the tubular bodies 10b) and the frame 10a can be separated into several parts.

[0063] For the same reasons mentioned above, the teeth 8d of a gearbox can be separated into several helices, each having 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: A half-crown 9a consists of a rim 9aa and a half-flange 9ab. The rim 9aa houses the upstream helix of the reduction gear teeth. This upstream helix meshes with that of the satellite 8, which in turn meshes with that of the solar 7. A downstream half-crown 9b consists 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 8, which in turn meshes with that of the solar 7.

[0064] If the helix widths vary between the solar 7, the satellites 8 and the crown 9 because of 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.

[0065] The mounting half-flange 9ab of the upstream crown 9a and the mounting half-flange 9bb of the downstream crown 9b form the mounting flange 9c of the crown. The crown 9 is fixed to a crown carrier by assembling the mounting flange 9c of the crown and the mounting flange 12a of the crown carrier using, for example, a bolted assembly.

[0066] The arrows in [Fig. 2] describe the oil flow in the gearbox 6. The oil enters the gearbox 6 from the stator section 5 into 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 two parts, generally each repeated with the same number of planets. The injectors 13a lubricate the gear teeth, and the arms 13b lubricate the bearings 11. The oil is supplied to the injectors 13a and exits through the ends 13c to lubricate the gear teeth of the planets 8, the sun gear 7, and also the ring gear. 9. The oil is also supplied to the arm 13b and flows through the feed opening 13d of the body 10b into an internal cavity 10c of the latter. The oil then flows through this cavity 10c to supply oil passage orifices lOd to ​​an external cylindrical guiding surface of the corresponding satellite.

[0067] Figures 3 and 4 show a more concrete example of the realization of a plain bearing 11 and its tubular body 10b for a reducer satellite 8.

[0068] The tubular body 10b comprises two coaxial annular walls 20a, 20b which extend around each other and are connected to each other by an annular core 20c.

[0069] The internal annular wall 20b has axial ends defining tubular fittings 25 for mounting on the planet carrier 10. At least one of these axial ends is open to also define the aforementioned supply port 13d for receiving oil supplied by the distributor (not shown). The internal wall 20b further defines the internal cavity 10c for receiving the lubricating oil.

[0070] The external annular wall 20a has an axial length or dimension measured along the Y axis, which is close to that of the wall 20b. The wall 20a includes an external cylindrical surface 20aa which is configured to delimit with an internal cylindrical surface 8a of the bearing 8 an annular space for receiving oil and forming an oil film for the purpose of forming the plain or hydrodynamic bearing 11.

[0071] The core 20c has a shorter length measured in the same way, so that the axial ends of the walls 20a, 20b define annular grooves 21a, 21b between them. This configuration allows the body 10b to have a certain degree of flexibility at each of its axial ends.

[0072] The body 10b further comprises a transverse partition 22 located in the cavity 10c, substantially in its middle with respect to the extent of the cavity along the Y axis. This partition 22 is connected at its periphery to the internal surface of the wall 20a and comprises conduits 23 for fluidic communication of the two portions of the cavity 10c between which the partition 22 extends.

[0073] The body 10b includes at least one main channel lOd for the passage of lubricating oil from the cavity 10c to the external periphery of the body 10b, and in particular to a main lubrication groove 24 formed or cut into the surface 20aa (cf. [Fig.4]).

[0074] In the example shown, this channel lOd is formed in the middle of the body 10b, with respect to the extent of the body along the Y axis, and extends from one of the conduits 23 to the surface 20aa by passing through the partition 23, the internal wall 20b, the core 20c and finally the external wall 20a.

[0075] Cavity 10c is continuously supplied with oil during operation. This oil enters cavity 10c then into conduits 23 and is conveyed by the main channel lOd to ​​the lubrication groove 24. The centrifugal forces applied to the planet carrier 10 and the bodies 10b in operation are sufficient to ensure this oil circulation.

[0076] The lubrication groove 24 extends over a major part of the length of the body 10b of the plain bearing 11 and is closed by the inner surface 8a of the satellite 8 when the latter is in its normal operating position illustrated in Figure 5a. The lubricating oil that supplies the main groove 24 flows between the surfaces 20aa, 8a and escapes from the longitudinal ends of the bearing 11 with a controlled flow (arrows Fl in Figure 5a).

[0077] As mentioned above, during operation, the satellite 8 can undergo axial displacements and adopt extreme positions illustrated in Figures 5b and 5c, in which an axial end of the main groove 24 may no longer be covered by the satellite 8 and release oil at an excessive rate. In Figure 5b, the satellite 8 has adopted an extreme axial position in which a first longitudinal end of the groove 24 (on the right in the drawing) is exposed, and uncontrolled oil leaks occur at this end (arrows F2). In Figure 5c, the satellite 8 has adopted the opposite extreme axial position in which a second, opposite longitudinal end of the groove 24 (on the left in the drawing) is exposed, and uncontrolled oil leaks occur at this end (arrows F2).

[0078] The present invention proposes a solution to this problem.

[0079] One embodiment of the invention is illustrated in Figures 6a and following.

[0080] The plain bearing 11 according to the invention comprises a tubular body 10b, preferably monobloc, having a main Y axis and comprising:

[0081] - an external cylindrical surface 20aa extending around the Y axis over a major part of an axial dimension of the body 10b (at least 90% in the example shown),

[0082] - two tubular mounting ends 25 located respectively at two ends opposites of body 10b along the Y axis,

[0083] - an internal cavity 10c intended to receive oil and opening at the center of minus one of the 25 tips,

[0084] - a main lubrication groove 24 which is formed or cut into the surface external 20aa of a median part 20aal of the body 10b and which has an elongated, and preferably straight, shape along the Y axis, and

[0085] - a main oil supply channel for the main groove 24, which ensures fluidic communication between cavity 10c and main groove 14.

[0086] In the example shown, the internal surface 8a of the body of satellite 8 has a length L1 measured along the Y-axis. The external surface 20aa of the body 10b of the plateau lia a length L2 measured along the Y axis (cf. [Fig.7]).

[0087] The main groove 24 has a length L3 measured along the Y axis and a width T3 measured in a plane perpendicular to this axis ([Fig.7]).

[0088] In the example shown, the main channel lOd feeds the main groove 24 at its midpoint. The main channel lOd can have a constant internal diameter, denoted DI.

[0089] The figures show that:

[0090] - L2 is smaller than L1 and represents, for example, 60 to 90% of L1,

[0091] - L3 is smaller than L2 and represents, for example, 60 to 80% of L2,

[0092] - DI is less than T3,

[0093] - L3 is between 10.T3 and 50.T3.

[0094] These parameters are, however, optional. They can be combined or taken individually within the scope of the present invention. Each of them offers advantages in terms of oil circulation and consumption.

[0095] According to the invention, the body comprises two opposing end parts 20aa2, 20aa3 separated from each other by the middle part 20aal of the body 10b. At least one of these end parts 20aa2, 20aa3 has a secondary lubrication groove 26 which is cut into the external surface 20aa and which has an elongated, and preferably straight, shape along the Y axis and which is independent of the main groove 24. The grooves 24, 26 are preferably parallel to each other and to the Y axis.

[0096] In the example shown, each of the end parts 20aa2, 20aa3 includes a secondary groove 26. The plain bearing 11 thus includes a main groove 24 and two secondary grooves 26. Alternatively, the plain bearing 11 could include a secondary groove 26 on only one of its end parts 20aa2, 20aa3.

[0097] The body 10b of the plain bearing 11 further includes a secondary channel 27 for supplying oil to the or each secondary groove 26, which ensures fluidic communication between the cavity 10c and the secondary groove 26.

[0098] Each secondary groove 26 has a length L4 measured along the Y axis and a width T4 measured in a plane perpendicular to this axis.

[0099] In the example shown, the secondary channel 27 supplies each secondary groove 26 from one of its longitudinal ends. It is the longitudinal end located on the side of the main groove 24 or the other secondary groove 26 that is supplied by the secondary channel 27. It is thus understood that if one of the secondary grooves 26 becomes exposed, it is the longitudinal end of that groove opposite its oil-supplied end that will be exposed, which is advantageous for limiting oil leaks during operation.

[0100] Each secondary channel 27 can have a constant internal diameter, denoted D2.

[0101] The figures show that:

[0102] - L4 is smaller than L3 and represents, for example, 20 to 50% of L3,

[0103] - T4 is similar or identical to T3.

[0104] Furthermore, let E be the distance between each secondary groove 26 and the main groove, measured in a plane perpendicular to the Y-axis. This distance E is controlled and is here less than T3 and T4. Moreover, in the example shown, the two secondary grooves 26 are located on the same side of the main groove 24 and are axially aligned with each other, so the distance E is identical for both secondary grooves 26.

[0105] The secondary feed channel 27 of each secondary groove 26 preferably has a minimum cross-sectional area smaller than that of the main channel 10c. This minimum cross-sectional area can be obtained by a channel 27 with a smaller internal diameter D2 (i.e., D2 is less than or equal to Dl). Advantageously, this cross-sectional area is obtained by a fluid restrictor 28 which is fitted and fixed in each secondary channel 27. In this latter case, the internal diameter D2' of each secondary channel 27 can be similar or identical to the internal diameter Dl of the main channel 26, and the minimum cross-sectional area in each secondary channel 27 is defined by the restrictor 28 (see [Fig. 8]). D2' is here less than T4.

[0106] Figures 7 and 8 show that each of the restrictors 28 is mounted in a bore 29 of the body 10b located at the intersection between the secondary groove 26 and its channel 27. The restrictor 28 can be shrink-fitted into the bore 29, for example. The bore 29 here has a diameter greater than D2' and less than the width T4.

[0107] Each restrictor 28 may comprise a tubular, one-piece body having a transverse partition 28a perforated with one or more orifices 28b of predetermined internal diameter D3. It is thus understood that the restrictor 28 reduces the cross-sectional area in the channel 27 in which it is mounted. Upstream of the restrictor 28, the cross-sectional area is equal to jt. (D2 / 2)2. At the restrictor 28, the cross-sectional area becomes k.ir.(D3 / 2)2, where k is the number of orifices 28b.

[0108] Advantageously, the main groove 24 and secondary groove(s) 26 overlap axially with each other as illustrated in Figures 6 and 7. This means that each secondary groove 26 extends axially into the external surface 28aa of the middle part 28aal so as to have an end part that overlaps (in a tangential direction around the Y axis) an end part of the main groove 24.

[0109] The overlap length is denoted L5 and can represent between 10 and 30% of L4 (cf. [Fig.7]).

[0110] L6 is designated as the longitudinal dimension of the body 10b of the plain bearing 11 on which the main groove 24 and secondary groove(s) 26 extend. It is understood that in the example shown L6 is equal to L3+2.L4-2.L5.

[0111] Advantageously, L6 is between 95%.L1 and 99%.L1, which allows the grooves to directly supply almost the entire length of the internal surface 8a of the satellite 8.

[0112] Figures 6a to 6c and 9a to 9c show relative axial positions of a satellite 8 on the plain bearing 11 according to the embodiment described above.

[0113] In normal operating position (figures 6a and 9a), the satellite 8 is located in the middle of the plain bearing 11 and the grooves 24, 26 are closed by the internal surface 8a of the satellite 8. The lubricating oil which supplies the grooves 24, 26 flows between the surfaces 20aa, 8a and escapes at the longitudinal ends of the bearing 11 with a controlled flow (arrows Fl).

[0114] In Figures 6b and 9b, the satellite 8 has adopted an extreme axial position in which part of one of the grooves 26 (on the left in the drawing) is exposed, and controlled oil leakage occurs at this end (arrows F3) thanks to the restriction of the diameter or cross-section of the secondary channel 27. In Figures 6c and 9c, the satellite 8 has adopted the opposite extreme axial position in which part of the other groove 26 (on the right in the drawing) is exposed, and controlled oil leakage occurs at this end (arrows F3) thanks to the restriction of the diameter or cross-section of the secondary channel 27. Regardless of the axial position of the satellite 8 on the bearing 11, the main groove 24 is therefore always covered by the satellite 8 and continuously supplies the interface between the bearing 11 and the satellite with sufficient flow. 8.

[0115] Restricting the diameter or cross-section of the passage in each secondary channel 27 limits the leakage to a flow rate only slightly higher than that required for the operation of the bearing 11 (for example, approximately 5% higher). It also maintains sufficient pressure in the internal cavity 10c of the bearing 11 to ensure oil supply to the main groove 24, thereby reducing the risk of seizing.

[0116] In the case of using the bearing 11 according to the invention in a mechanical reducer 6, the sufficient flow to the reducer is thus known and controlled in all phases of flight and does not require oversizing the circuit for the phases with high displacement.

Claims

1.

2.

3. Demands Plain bearing (11) for an aircraft turbomachine, this plain bearing (11) comprising a tubular body (10b) with main axis (Y) and comprising: - an external cylindrical surface (20aa) extending around the axis (Y) over a major part of an axial dimension of the body (10b), - two tubular mounting ends (25) located respectively at two opposite ends of the body (10b) along the axis (Y), - an internal cavity (10c) intended to receive oil and opening into the center of at least one of the nozzles (25), - a main lubrication groove (24) which is machined on the external surface (20aa) of a central portion (20aal) of the body (10b) and which has an elongated shape along the axis (Y), and - a main oil supply channel (lOd) for the main groove (24), which ensures fluidic communication between the cavity (10c) and the main groove (24), characterized in that the body (10b) comprises two opposing end portions (20aa2, 20aa3) separated from each other by the middle portion (20aal) of the body (10b), at least one of these end portions (20aa2, 20aa3) having a secondary lubrication groove (26) machined into the outer surface (20aa) and having an elongated shape along the axis (Y) and which is fluidically independent of the main groove (24), the secondary groove(s) (26) having a longitudinal dimension (L4) smaller than that (L3) of the main groove (24), the secondary groove(s) (26) extending into the outer surface (20aa) of the part median (20aal) of the body (10b) to create a zone of mutual overlap with the main groove (26),and in that the body (10b) further comprises a secondary oil supply channel (27) for the secondary groove (26), which ensures fluidic communication between the cavity (10c) and the secondary groove (26), said secondary channel (27) having a minimum passage cross-section smaller than that of the main channel (10d). Plain bearing (11) according to claim 1, wherein the main groove (24) and secondary groove(s) (26) are straight and parallel. Plain bearing (11) according to any one of the preceding claims, wherein the secondary groove(s) (26) has a longitudinal dimension (L4) less than half that (L3) of the main groove (24).

4. Plain bearing (11) according to any one of the preceding claims, wherein the main channel (lOd) is devoid of a restrictor.

5. Plain bearing (11) according to any one of claims 1 to 4, wherein the or each secondary channel (27) comprises a restrictor (28) which is reported and fixed on the body (10d).

6. Plain bearing (11) according to any one of the preceding claims, wherein the main channel (10d) is located substantially in the middle of the main groove (24), and the secondary channel (27) is located at a longitudinal end of the or each of the secondary grooves (26), this longitudinal end being located on the side of the main groove (24).

7. Plain bearing (11) according to any one of the preceding claims, wherein it comprises a main groove (24) and two secondary grooves (26), the two secondary grooves (26) being axially aligned with each other and being located at a predetermined distance (E) from the main groove.

8. Plain bearing (11) according to the preceding claim, wherein the distance (E) is less than or equal to a width (T3) of the main groove (24).

9. Assembly comprising a plain bearing (11) according to any one of the preceding claims, and a mechanical reducer satellite (8) (6), this satellite (8) comprising a tubular body having a principal axis (Y) and comprising: - at least one external toothing (8d) extending around the axis (Y), and - an internal cylindrical surface (8a) extending around the axis (Y) over a major part of an axial dimension of the body, this internal surface (8a) being intended to extend around the external surface (20aa) of the body (10b) of the plain bearing (11).

10. Assembly according to claim 10, wherein the internal surface (8a) of the satellite body (8) has a length (L1) less than that (L2) of the external surface (20aa) of the body (10b) of the plain bearing (11), and wherein the main groove (24) and secondary groove(s) (26) extend over a longitudinal dimension (L5) of the body (10b) of the plain bearing (11) which is between 95%.L1 and 99%.L1, L1 being the length of the internal surface (8a) of the satellite body (8).

11. A mechanical reducer (6) for a turbomachine, in particular for aircraft, comprising a solar element (7), a ring gear (9) extending around the solar element (7), and assemblies according to claim 10 or 11, the satellites (8) of these assemblies being meshed with the solar element (7) and the

12. crown (9). Turbomachine (1), in particular aircraft, comprising a mechanical reducer (6) according to the preceding claim.

Images