Device for guiding shaft of aircraft turbine engine

Abstract

The invention relates to a device for guiding a shaft of an aircraft turbine engine, comprising:-rolling bearings (10, 11); -an annular bearing support (22); and-an oil film compression damping system (19) comprising:-two annular sealing sections (26, 27); and-a first oil supply circuit (33) connected to the annular supply groove (34), characterized in that the damping system further comprises:-a second oil supply circuit (41) connected to at least one annular temperature control groove (40) independent of the supply groove (34) and extending around one of the sealing sections (26, 27).

Description

Technical Field

[0001] The invention relates to a device for guiding the shaft of an aircraft turbine engine and to an aircraft turbine engine comprising such a device. Background Art

[0002] The prior art includes in particular documents FR-A1-2 876 758, FR-A1-3 085 242, FR-A1-3 088 680, US-A1-202 / 284298, FR-A1-3 093 531, FR-A1-2 664 330, US-A1-2017 / 248033 and US-A1-2016 / 369652.

[0003] In general, a turbine engine comprises a rotating member, such as a shaft, which is guided relative to a stationary structure of the turbine engine by guide bearings. Each of these guide bearings comprises an inner ring and an outer ring enclosing rolling elements, such as rollers or balls. Typically, the outer ring is firmly mounted on a bearing support of the turbine engine and the inner ring is firmly mounted on the rotating shaft of the turbine engine.

[0004] Some guide bearings can be associated with an oil film compression damping system known as a squeeze film damper. The oil film is more or less confined in an annular space extending around the bearing so as to damp the movement of the rotating shaft and reduce the vibrations of the rotating shaft, which are transmitted to the bearing supports and fixed structures of the turbine engine and the aircraft. These damping systems also make it possible to reduce the consumption of the rotor / stator clearance at each compressor and turbine stage by damping the rotor modes, thereby increasing the engine performance. Finally, the damping system makes it possible to reduce the risk of the occurrence of non-synchronous vibrations or NSV (NonSynchronous Vibrations), which can damage the engine, in particular when the shaft on which the damping system is arranged is a supercritical rotor (wherein the first bending mode of the supercritical rotor is within the operating range of the engine). In general, the oil film makes it possible to improve the dynamic response of the turbine engine at a given operating speed, thereby improving the performance of the turbine engine.

[0005] The annular space in which the oil film is formed is delimited radially between the outer ring of the guide bearing (which is locked against rotation) and the bearing support, and axially by annular sealing segments. These segments enable the oil film to be kept under pressure (which provides the required cushioning) while ensuring the drainage of the oil.

[0006] Traditionally, the sealing segment is an annular metal element, elastically deformable, resistant to high temperatures, and having straight or cut slots or overlaps in the tangential direction of the segment. This cross section enables the oil to be drained, wherein the oil flow rate is dictated by the overall dynamics. This flow rate must be sufficient to drain the heat generated by the damping in the oil film, but not so high that the oil film remains under pressure.

[0007] As a guide, the flow rate can be in the order of tens of liters per hour, and the cross section of each segment can be cut to a few tenths of a millimeter to a few millimeters. When the segments are assembled, they are radially supported on the bearing support or on a shrink ring mounted in the support, and axially supported on the wall of the channel formed in the outer ring of the bearing (corresponding to the inner ring of the oil film) and accommodating the segments. Therefore, the oil can only pass through the tangential gap at the cutout of each segment.

[0008] In operation, the gap at the cross section of the segment varies due to the thermal gradient between the segment (which can be considered to be approaching oil temperature first) and the bearing support or shrink ring (on which the segment is supported).

[0009] At various stages in the engine life, this thermal gradient changes during operation due to the temperature conditions of the oil and parts:

[0010] - From the start-up to the take-off phase, the oil is hotter than the bearing support: the gradient between the oil (and the segments in direct contact with the oil) and the bearing support (on which the segments are supported) is negative.

[0011] Since the segments are hotter than the support (because they are in contact with the oil), they will expand in the axial direction, which will cause the gap to close during cutting due to contact with the cooler support;

[0012] - From take-off to end of mission phase, the bearing support is hotter than the oil entering the membrane, so the gradient is positive. Since the segments are cooler than the support (because they are in contact with the oil), they will compress axially, which will cause the cutting gap to open due to contact with the hotter support.

[0013] For example, during a typical flight mission, there may be a temperature gradient of several tens of degrees between the temperature of the oil and the bearing support corresponding to the rolling bearing. This gradient may also change significantly during extremely transient phases (rapid acceleration or deceleration) outside of a classic mission.

[0014] The object of the present invention is to provide an optimized damping device which makes it possible to reduce the thermal gradient between the sealing segment and the bearing support or the shrink ring with which the sealing segment is in contact in the case of a straight cut of the sealing segment.

[0015] Document FR-A1-2876758 describes a sealing segment with overlapping cutouts, comprising recesses for the passage of oil at the periphery of the sealing segment.

[0016] This solution reduces the static rotational forces generated by a single leak at the section, but does not reduce the thermal gradient p. Furthermore, from an industrial point of view, the machining of the notches can be complex, with the machining costs of the notches being two to three times that of a conventional straight-cut section. Finally, defining the geometry (height and width) of these notches requires complex calculations and validation tests to ensure that the leakage flow generated by these sections is as expected. Summary of the invention

[0017] The invention relates to a device for guiding the shaft of an aircraft turbine engine, comprising:

[0018] - rolling bearing, the rolling bearing comprises two rings, namely a first ring and a second ring, and the rolling element is installed between the first ring and the second ring,

[0019] - an annular bearing support extending around the bearing, and

[0020] - An oil film compression damping system installed between the bearing support and the second ring, the damping system comprising:

[0021] - an annular shrink ring, which is inserted between the bearing support and the second ring,

[0022] - two annular sealing segments, respectively located upstream and downstream, housed in annular grooves formed in the outer cylindrical surface of the second ring and able to bear radially on the inner cylindrical surface of the shrink ring, the outer and inner surfaces defining between them an annular space for the formation of an oil film, the annular space being axially delimited by the sealing segments, each of these segments being cut open by a straight cut to enable the oil to be discharged from this space, and

[0023] a first oil supply circuit connected to an annular supply channel extending around the space and connected to the space through orifices formed in the shrink ring,

[0024] Characterized in that the damping system also includes:

[0025] a second oil supply circuit connected to at least one annular heating channel which is independent of the supply channel and extends around the space and is arranged corresponding to one of the sealing sections.

[0026] The invention therefore proposes to equip the guide device with at least one heating channel, independent of the supply channel and dedicated to reducing the above-mentioned thermal gradient. It will therefore be understood that, unlike the single circuit of the prior art, the device comprises two oil circuits with different functions.

[0027] Therefore, in the present application, the channels are differentiated according to their function. The function of the oil supply channel is to supply oil, while the function of the heating channel is to regulate the temperature and thus to supply or remove heat, in particular in order to limit the occurrence of thermal gradients.

[0028] The oil which circulates in the first circuit, in particular in the annular supply channel, in the bores and in the space, does not circulate in the second circuit, in particular not in the heating channel, and vice versa.

[0029] The device according to the invention may include one or more of the following features, which may be employed alone or in combination with each other:

[0030] - the supply channel is formed in the annular support or in the shrink ring;

[0031] - the or each heating channel is formed in the annular support and / or in the shrink ring;

[0032] - the axial extent of the supply channel is greater than the axial extent of the orifice;

[0033] - the or each heating channel has an axial extent greater than the axial extent of the sealing section, the heating channel extending around the sealing section;

[0034] - a second oil supply circuit is connected to two heating channels, one upstream and one downstream, respectively, which are arranged corresponding to the sealing section;

[0035] - the or each heating channel is connected to at least one oil outlet orifice formed in the shrink ring;

[0036] - said at least one oil outlet opening is axially offset from said space so as to prevent oil leaving said opening from entering said space;

[0037] - the oil outlet orifice connected to the upstream heating channel opens upstream of the upstream sealing section or even upstream of the second turn;

[0038] - the oil outlet orifice connected to the downstream heating channel opens downstream of the downstream sealing section;

[0039] - the or each heating channel is connected to at least one oil inlet orifice formed in the bearing support;

[0040] - the oil inlet orifice and the oil outlet orifice of the or each heating channel are positioned at an angle less than or equal to 30°, preferably less than or equal to 20°, relative to each other; this angle is measured relative to the axis of the bearing;

[0041] - similar to a clock face, the oil inlet opening of the or each heating channel is located in an angular region extending between 12 o'clock and 1 o'clock about the main axis of the device according to the first configuration, or in an angular region extending between 11 o'clock and 12 o'clock about the axis according to the second configuration, and the oil outlet opening of the or each heating channel is located in an angular region extending between 11 o'clock and 12 o'clock about the axis according to the first configuration, or in an angular region extending between 12 o'clock and 1 o'clock about the axis according to the second configuration;

[0042] - the oil inlet orifice and the outlet orifice of the or each heating channel are inclined relative to the radial direction;

[0043] - the first circle and the second circle are the inner circle and the outer circle respectively, or conversely, the first circle and the second circle are the outer circle and the inner circle respectively;

[0044] --The device comprises a main axis, and the bearing extends around the main axis;

[0045] - the cross-section of each segment extends in a plane parallel to said axis;

[0046] - a second ring of guide means is associated with the flexible cage and comprises a hollow annular web connected to an annular fixing flange;

[0047] --the oil pressure in the first supply circuit is higher than the oil pressure in the second supply circuit;

[0048] - the oil pressure in one or more heating channels is between 1.5 bar and 10 bar;

[0049] -- Each segment defines a cutting gap of 0.05 mm to 5 mm at the position where it is installed in the device;

[0050] - the or each heating channel has an axial extent that is one to five times the axial extent of the segment associated with that channel;

[0051] --The radial thickness of the oil film or the space where the oil film is formed is between 0.05 mm and 1 mm;

[0052] --The axial distance between the segments or the length of the oil film or the length of the space where the oil film is formed is between 10 mm and 50 mm;

[0053] --The diameter of the oil film or the space in which the oil film is formed is between 100 mm and 500 mm;

[0054] - the or each supply channel is of a central type and is located midway between the sealing sections;

[0055] - the or each supply channel is of eccentric type and is located close to one of the sealing sections;

[0056] - when the supply channel is of the central type, the device comprises exactly two heating channels;

[0057] - when the supply channel is of eccentric type, the device comprises a single heating channel;

[0058] The invention also relates to an aircraft turbine engine comprising a device as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Further features and advantages will emerge from the following description of non-limiting embodiments of the invention with reference to the accompanying drawings, in which:

[0060] [ Figure 1 ] Figure 1 is a schematic half view of an axial section of an aircraft turbine engine,

[0061] [ Figure 2 ] Figure 2 is a schematic axial cross-section and perspective view of a guide device in the prior art,

[0062] [ Figure 3 ] Figure 3 yes Figure 2 A schematic cross-sectional view of the guiding device shown,

[0063] [ Figure 4 ] Figure 4 yes Figure 2 A schematic axial cross-sectional view of the guide device shown,

[0064] [ Figure 5 ] Figure 5 is a schematic perspective view of a sealing section in cross section,

[0065] [ Figure 6 ] Figure 6 is a schematic perspective view of a sealing section with overlapping cutouts,

[0066] [ Figure 7 ] Figure 7 is similar to Figure 4 and showing an embodiment of a guide device according to the invention,

[0067] [ Figure 8 ] Figure 8 is with Figure 7 A similar view and showing an alternative embodiment of the invention,

[0068] [ Fig. 9 ] Fig. 9 is with Figure 7 A similar view and showing another embodiment of the present invention, and

[0069] [ Fig.10 ] Fig.10 is a very schematic view of a heating channel of a guide device according to the invention and shows the positions of the oil inlet and outlet orifices of the channel. DETAILED DESCRIPTION

[0070] Figure 1 is a partial axial section through a turbine engine 1 to which the invention applies, having a longitudinal axis X. The turbine engine 1 shown is a twin-flow turbine engine designed to be installed on an aircraft.

[0071] Typically, a turbine engine 1 comprises a rotating shaft which is guided in rotation relative to a fixed part of the turbine engine via one or more guide bearings. The rotating shaft may be a low-pressure shaft on the turbine engine. The rotating shaft may also be a high-pressure shaft or any shaft driven in rotation by a guide bearing in the turbine engine.

[0072] Reference Figure 1 The low-pressure shaft 2 drives, for example, a fan 3 located upstream of the turbine engine 1. The turbine engine 1 comprises, downstream of the fan 3, a compressor assembly (a low-pressure compressor 4a and a high-pressure compressor 4b), a combustion chamber 5 and a turbine assembly (a high-pressure turbine 6a and a low-pressure turbine 6b), which form a gas generator.

[0073] In the present invention, the terms “upstream” and “downstream” are defined relative to the gas flow in the turbine engine, here along the longitudinal axis X.

[0074] The low-pressure shaft 2 connects the low-pressure compressor 4a of the compressor assembly and the low-pressure turbine 6b of the turbine assembly to form a low-pressure body. The turbine engine 1 may also include a high-pressure body, which includes the high-pressure compressor 4b of the compressor assembly, which is connected to the high-pressure turbine 6a of the turbine assembly via a high-pressure shaft 7.

[0075] The low-pressure shaft 2 is centered on the longitudinal axis X and is guided at its upstream end by an upstream guide bearing 10 and at its downstream end by a downstream guide bearing 11. The guide bearings 10, 11 are each housed in an enclosure of a stationary housing 12 relative to which the low-pressure shaft 2 rotates.

[0076] Reference Figures 2 to 4, each bearing 10, 11 comprises an annular inner ring 13 mounted on a rotating shaft (low-pressure shaft 2) and an annular outer ring 14 connected to a fixed structure, the fixed structure being fixed to the fixed housing 12 of the turbine engine 1. For example, the inner ring 13 is contracted onto the low-pressure shaft 2 to prevent any translation or rotation of the inner ring 13 relative to the low-pressure shaft 2. Advantageously, the outer ring 14 is fixed to the fixed structure by anti-rotation means to prevent the outer ring from rotating relative to the fixed structure. The anti-rotation means are generally formed by a radial spacer 15, which is housed on the one hand in a recess open to the outside in the outer ring 14 and on the other hand in a hole (not shown) in a fixed structure fixed to the fixed housing 12. The outer ring 14 surrounds the inner ring 13 and is radially spaced apart from the inner ring 13.

[0077] In the present invention, the terms “radial” and “radially” are defined relative to a radial axis R perpendicular to the longitudinal axis X.

[0078] Rolling elements 16, such as rollers or balls, are arranged between the inner ring 13 and the outer ring 14, which provide a connection between the rotating shaft and the fixed structure of the turbine engine. The inner ring 13 and the outer ring 14 include inner surfaces 17, 18, which form inner rolling tracks for the rolling elements 16.

[0079] Figures 2 to 4 It is also shown that the bearings 10, 11 are equipped with a damping system. The damping system comprises a damping film, which is an oil film 19 and circulates between the outer ring 14 and the fixed structure of the turbine engine. This oil film 19 limits, damps or regulates the vibrations of the turbine engine 1 during operation. It is known that when one or more rotating shafts rotate, the turbine engine 1 vibrates in at least one given vibration mode. These vibrations are caused, for example, by imbalances in the turbine engine 1 and the imbalances generated by these imbalances.

[0080] The oil film 19 is designed to occupy the annular damping space 20. Figure 4 In the case of the guide bearing, the space 20 is radially located between the outer ring 14 of the guide bearing and an annular shrink ring 21 (i.e. a shrink ring) mounted in an annular bearing support 22, which forms part of or is fixed to the fixed structure. In other words, the shrink ring 21 surrounds the outer ring 14 of the bearing 10, 11 and is itself surrounded by the bearing support 22.

[0081] The inner cylindrical surface 22a of the bearing support 22 faces the outer cylindrical surface 21a of the shrink ring 21. The inner cylindrical surface 21b of the shrink ring 21 faces the outer cylindrical surface 14a of the outer ring 14 of the bearings 10, 11. The surfaces 22a and 21a are in contact with each other. The surfaces 21b and 14a are radially spaced apart from each other, and the radial gap between these surfaces 21b and 14a is predetermined to define the radial size of the space 20 for forming the oil film 19.

[0082] The damping space 20 is also axially bounded by sealing segments 24, which regulate or allow oil to "leak" from the damping membrane to the outside of the space 20. These segments control the leakage flow of the damping membrane to ensure effective vibration reduction. In the present invention, the terms "axial" and "axially" are defined relative to the longitudinal axis X.

[0083] The first annular segment 26 is located upstream of the space 20 and the second annular segment 27 is located downstream of the space 20. The segments 26, 27 extend radially between the outer ring 14 and the shrink ring 21. The outer ring 14 comprises a first annular groove 28 upstream and a second annular channel 29 downstream, which are designed to receive the segments 26, 27 respectively. The grooves 28, 29 are formed in the surface 14a of the outer ring 14 and are axially spaced apart. The segments 26, 27 extend radially from the grooves 28, 29 of the segments and can be radially supported on the surface 21b of the shrink ring. Due to the pressure exerted by the oil film during operation, the segments 26, 27 are also designed to bear on the side walls of the channel (the upstream segment 26 bears on the upstream wall of the upstream groove 28 and the downstream segment 27 bears on the downstream wall of the downstream groove 29).

[0084] The sections 26, 27 are slotted and each section includes a cutout or slot 30 forming a facing end 31 (see Figure 5 ). This is called a straight cut. Each end 31 is defined in a plane parallel to the plane RX. The plane RX is formed by the longitudinal axis X and the radial axis R. The sections 26, 27 have a substantially square or rectangular cross section.

[0085] exist Figure 6 In the current technology shown, the segments 26, 27 can also be divided and each segment comprises overlapping cuts 30. In this case, each end comprises a tongue extending in the circumferential direction (transverse axis T). The transverse axis T is perpendicular to the longitudinal axis X and the radial axis R. The two tongues each have a surface intended to abut axially against each other and an axially opposite surface flush with one side of the segment. The segments 26, 27 can also be provided with notches 32 on the periphery of the segments 26, 27. These notches are evenly distributed around the axis of the segment (parallel to the longitudinal axis X in the installed condition) and allow the power dissipated by the damping in the oil film 19 to be discharged.

[0086] In the present invention, the sections 26 and 27 are as follows Figure 4 When mounted in the device, the notch gap J, ie the distance between the circumferential ends of the segments, is preferably between 0.5 mm and 5 mm.

[0087] The turbine engine 1 is also equipped with a first supply circuit 33 connected to a supply source (not shown) to supply pressurized oil to the space 20 and form an oil film 19 therein. This first circuit 33 can also supply oil to the guide bearing to lubricate it.

[0088] For this reason, Figure 4 As shown, the bearing support 22 comprises an annular supply channel 34 which extends around the space 19 and is connected to the space via an orifice 35 formed in the shrink ring 21. The channel 34 is connected to a duct 36 which is schematically shown here. The channel 34 extends around the space 19 between the segments 26, 27 and at a predetermined axial position relative to these segments 26, 27. The channel 34, the orifice 35 and the duct 36 form part of a supply circuit 33.

[0089] The orifices 35 are calibrated and their number is between 1 and 12. The orifices 35 are preferably evenly distributed around the axis X.

[0090] exist Figure 4 In the example shown, the channel 34 is of eccentric type, or the oil film feed 19 is of eccentric type. H is defined as a mid-plane perpendicular to X and passing approximately through the middle of the oil film. It can be seen that the channel 34 is not intersected by this plane H, but is at a distance from this plane H, and here downstream of this plane, close to the downstream section 27.

[0091] Alternatively, the supply channel can be of the central type, or the feed 19 into the oil film can be of the central type. To achieve this, the channel will be traversed by the plane H, and will therefore be approximately in the middle between the sections 26 and 27.

[0092] Figure 4 It also shows the flow of oil in the circuit 33 from the duct 36 to the channel 34 (arrow F1) through the orifice 35 in the shrink ring 21 and then from the space 20 through the cross section of the sectors 26, 27. Corresponding to the orifice 35, the outer surface 14a of the ring 14 may comprise an annular groove 37 for collecting the oil leaving the orifice 35 and distributing it all around the axis X in the space 20.

[0093] The thermal gradient between the segments 26, 27 and the shrink ring 21 (on which the segments 26, 27 are radially supported) is not measured in operation and is therefore not well known. For example, the thermal gradient may be between 5° C. and 100° C. However, this gradient is used as an assumption to define the tangential gap, which is called the “kerf gap” of the segments 26 and 27.

[0094] In the presence of a negative gradient (the temperature of the segments is similar to that of the oil and higher than that of the shrink ring), the segments will stretch by thermal expansion and thus the gaps of the segments will close due to the applied gradient.

[0095] There are three different cases. In the first case, the function of the membrane can be seen without questioning its function, the segment is closed at the interruption point, but the closing gap imposed by the gradient is smaller than the interruption point, so the drainage of the oil can proceed normally. This case does not question the operation of the membrane.

[0096] In the second case, when the gap at the cutout (tangential gap) is not well defined or the thermal gradient used to define it is underestimated, the segment will close beyond the value of the predicted gap. As a result, the oil in the oil film 19 can no longer be emptied and the temperature will therefore rise very sharply (due to the heat generated by damping the oil film), which will reduce the viscosity of the oil and therefore the damping capacity of the oil film. If the gradient is too high and the segment is closed for too long, there is also a risk of oily coking, which makes the membrane completely inoperative and requires disassembly for cleaning.

[0097] In the third case, the absolute value of the negative thermal gradient is even greater than that of the thermal gradient in the second case, and the segments will be more inclined to close. Due to the radial clearance between the segments 26, 27 and the grooves 28, 29 that house them, the two ends of the segments will be pressed radially against each other at the bottom of the channel. As a result, the oil will be discharged via the space left between the outer diameter of the segments and the shrink ring, which may lead to very large leaks, larger than those in normal operation. If these leaks are too large, it will not be possible to achieve a sufficient supply pressure in the oil film, which will reduce the damping provided by the membrane.

[0098] On the other hand, in the second and third cases, as soon as the gradient returns to a positive value, the segment will regain its position with an open gap. Therefore, these two cases, as well as the repetition of these compression / decompression cycles of the segment in each mission of the vehicle (or for transient changes outside the classic mission of the vehicle), may create the risk of plasticization of the segment, whereby the segment will retain its deformed shape instead of its initial shape and therefore will no longer function.

[0099] The result in the second and third cases is to have a membrane that is non-functional or has a degraded (or even very degraded) operation compared to its nominal operation, with the damping provided by the membrane being reduced or even lost.

[0100] The results are as follows:

[0101] - Increased vibration,

[0102] - deterioration of the relative clearances between the rotor and the stator in the various compressor and turbine stages, and a deterioration of performance, or even an increase in the risk of surge,

[0103] - The occurrence of non-synchronous vibrations (NSV) which can damage the engine, especially if the membrane is arranged on a supercritical rotor.

[0104] Therefore, there is a need to reduce or at least control this thermal gradient, which is addressed by the present invention.

[0105] Therefore, the invention proposes to add a second oil supply circuit, which is dedicated to heating the sectors 26 and 27. To this end, the second circuit is connected to at least one annular heating channel extending around the space 20 and arranged in correspondence with one of the sectors 26, 27.

[0106] Figures 7 to 9 Several embodiments are shown in which the guide device can be used according to the invention. In particular, the differences between these embodiments are based on the number and position of the heating channels 40 and on the position of the supply channels 34.

[0107] Although not necessarily apparent from or described below, the guiding device according to the present invention may include some or all of the features of the guiding devices of the prior art, such as in Figures 2 to 5 In particular, the outer ring 14 of the guide device can be connected to a flexible cage C1 or a squirrel cage (i.e. a perforated cage connected to an annular fixed flange C2, such as Figure 2 shown).

[0108] Figure 7 A first embodiment of the guide device according to the invention is shown, in which the heating channel 40 is formed in the bearing support 22, in particular in the inner surface 22a of the support 22. This is also the case for the supply channel 34 formed in the support 22, in particular in the inner surface 22a of the support 22.

[0109] In this case, the channel 34 is central and therefore intersects the plane H. There are two channels 40 , an upstream channel situated upstream of the plane H and a downstream channel situated downstream of the plane H.

[0110] The cross section of the channel 34 is, for example, rectangular or square.

[0111] In the example shown, the axial extent of the passage 34 is greater than the axial extent of the orifice 35.

[0112] The upstream passage 40 extends around the space 20, and extends around the upstream section 26 and is disposed correspondingly to the upstream section 26. The downstream passage 40 extends around the space 20, and extends around the downstream section 27 and is disposed correspondingly to the downstream section 27.

[0113] The cross section of each channel 40 is, for example, rectangular or square. The shapes and sizes of the channels 40 are the same, and the volume defined by each channel 40 may be smaller than the volume defined by the channel 34.

[0114] In the example shown, each channel 40 has an axial extent greater than that of the segments 26, 27 around which it extends. The axial extent of each channel 40 is preferably 1 to 5 times, preferably 2 to 5 times, that of the corresponding segment.

[0115] The channels 40 form part of a circuit 41 comprising one or more ducts 42 supplying oil to the channels 40. In the example shown, each channel 40 is supplied with oil by a duct 42 independent of the duct 36.

[0116] The number of ducts 42 supplying a channel 40 is, for example, 1 to 3. The supply ducts 42 in a single channel 40 are preferably evenly distributed around the axis X.

[0117] Each duct 42 has an end opening into the corresponding channel 40 to form an oil inlet orifice 43. The shrink ring 21 comprises at least one radial orifice, and preferably a single radial orifice, forming an oil outlet orifice 44.

[0118] With regard to the upstream passage 40a, an oil outlet orifice 44 communicates with the upstream end of the passage 40 and is located upstream of the section 26, or even upstream of the coil 14. The arrows show the path of the oil through this area.

[0119] With respect to downstream passage 40b, an oil outlet orifice 44 communicates with the downstream end of passage 40b and is located downstream of section 27. Arrows illustrate the path of the oil through this area.

[0120] Circuits 33, 41 are preferably independent. This means that the oil circulating in the first supply circuit 33, in particular in the annular supply channel 34, in the orifice 35 and in the space 20, does not circulate in the second supply circuit 41, in particular in the heating channel 40 and the oil outlet orifice 44, and vice versa.

[0121] exist Figure 8In the variant shown, the channel 34 is eccentric and away from the plane H. The channel 34 is located downstream of the plane H and close to the sector 27. The channel 34 can be considered to extend partially around the sector 27 and to be arranged in correspondence with the sector 27. In this case, there is no heating channel 40 in this area. In fact, due to the presence of a temperature gradient in the shrink ring, closing this sector is less problematic, since this will promote the circulation of oil towards the opposite sector, which will increase the damping.

[0122] therefore, Figure 8 The guide means shown comprise a single channel 40, 40a situated upstream of the plane H and surrounding the segment 26. In the example shown, this channel 40 is formed in the shrink ring 21, in particular in the outer surface 21 of the shrink ring 21. The supply duct 42 for this channel 40 is similar to that for the Figure 7 The supply conduit of passage 40a in.

[0123] Circuit 33 is similar to Figure 4 The circuit shown. Figure 8 The passage 34, orifice 35 and conduit 36 ​​of the circuit 33 in the embodiment are similar to the upstream passage 40a, orifice 35 and conduit 36. Figure 4 A pipe 36 is connected to the channel.

[0124] Fig. 9 The embodiment shown is Figure 7 The embodiment shown differs in that the channel 40 is formed in the shrink ring 21 instead of in the support 22 , and in particular in the outer surface 21 a of the shrink ring 21 .

[0125] The circuits 36, 41 are preferably independent and can be supplied with oil at different pressures, for example from the same oil source. The supply pressure of the second circuit 41 is preferably lower than the supply pressure of the first circuit 36. To achieve this, the circuit 41 can be connected to the oil source by a pump that provides a pressure lower than the pressure provided by another pump connecting the circuit 36 ​​to the oil source. Alternatively, the circuits 36, 41 can be connected to the oil source by the same pump, and the circuit 41 can be configured to reduce the oil pressure supplied by the pump, for example by a controlled pressure drop in the pipe 42.

[0126] The oil pressure in the circuit 41 or in the or each channel 40 is preferably between 1.5 and 10 bar. The oil pressure in the circuit 36 ​​or in the channel 34 is preferably greater than 10 bar.

[0127] Fig.10 One of the heating channels 40 and the corresponding positions of its oil inlet opening 43 and oil outlet opening 44 are shown very schematically.

[0128] The oil inlet orifice 43 and the outlet orifice 44 of the or each heating channel 40 are positioned relative to each other at an angle (measured around the axis X) less than or equal to 30°, preferably less than or equal to 20°.

[0129] In the example shown, the oil inlet orifice 43 is formed by the opening of the duct 42 leading to the channel 40 and is located, for example, close to 12 o'clock, similar to a clock face (about the axis X). In the example shown, the oil inlet orifice 43 is located in an angular region extending between 12 o'clock and 1 o'clock about the axis X. The oil outlet orifice 44 is formed by the above-mentioned orifice and is located about the axis X at 11 o'clock and 12 o'clock.

[0130] Alternatively, the oil outlet orifice 44 may be located in an angular region extending about the axis X between 12 o'clock and 1 o'clock, and the oil inlet orifice 43 may be located in an angular region extending about the axis X between 11 o'clock and 12 o'clock.

[0131] As another possible variation, depending on the integration constraints, the orifices can be located at different azimuth angles while maintaining a "timing point" (relative azimuth position) (+ / - 1h) between the oil inlet and outlet orifices (e.g., inclined orifices (rather than purely radial orifices)) to force the flow direction of the oil flux between the oil inlet and outlet orifices to be coupled with the supply pressure applied to the oil flux.

[0132] The sections 26, 27 are made of a metal alloy, for example. Examples of metal alloys are mixtures of copper or iron.

[0133] The oil film 19 preferably has a radial thickness of between 0.05 mm and 1 mm. The segments 26, 27 are spaced apart from one another by a distance of between 10 mm and 50 mm, which corresponds to the length of the oil film.

[0134] The oil film 19 may be located at an injection radius comprised between 100 mm and 500 mm (measured relative to the axis X).

[0135] In operation, therefore, at the start of a mission, the oil is intended to reach the space 20 for forming the oil film 19 and the heating channel or channels 40. This oil will therefore increase the temperature of the shrink ring 21 more rapidly, thus mathematically reducing the gradient between the segment(s) 26, 27 and the shrink ring 21.

[0136] The oil reaching the passage 40 is then discharged through the oil outlet orifice 44 to ensure that the oil flows around the entire circumference of the passage 40 ( Fig.10 ).

[0137] The above-described size and shape (rectangular or non-rectangular) of the one or more passages 40 and the oil inlet orifices 43 and oil outlet orifices 44 may be defined using standard thermal calculations.

[0138] The invention thus provides a simple and passive way to reduce the thermal gradients between the segments 26, 27 and the shrink ring 21 or the bearing support 22 on which the segments are radially supported, which will therefore reduce the risk of "over-closing" of the segments in the event that there are tangential gaps at the cutouts or the thermal gradients are underestimated during the design phase.

[0139] This ensures better control of the damping of the film whatever the operating phase the engine is in, and this reduced gradient variation minimizes the variation of this gap over the cutout, which ensures smaller variations of the leakage flow and therefore better control / robustness of the oil film damping.

[0140] In contrast to the above, the bearing support 22 and the shaft 13 may have an opposite arrangement, wherein the bearing support 22 is located inside the bearings 10 , 11 and the shaft 13 is located outside the bearings 10 , 11 .

Claims

1. A device for guiding the shaft of an aircraft turbine engine, the device comprising: - a rolling bearing (10, 11), said rolling bearing comprising two rings (13, 14), respectively a first ring and a second ring, and a rolling element (16) being mounted between said first ring and said second ring, - an annular bearing support (22) extending around the bearing (10, 11), and - an oil film compression damping system (19) mounted between the bearing support (22) and the second ring (14), the damping system comprising: - an annular shrink ring (21) inserted between the bearing support (22) and the second ring (14), - two annular sealing segments (26, 27) located respectively upstream and downstream, housed in annular grooves (28, 29) formed in the outer cylindrical surface (14a) of the second ring (14) and able to bear radially on the inner cylindrical surface (21b) of the shrink ring (21), the outer surface and the inner surface (14a, 21b) defining between them an annular space (20) for forming an oil film (19), the annular space being axially delimited by the sealing segments (26, 27), each of these segments being cut open by a straight cut to enable the oil to be discharged from the space, and a first oil supply circuit (33) connected to an annular supply channel (34) extending around the space (20) and connected to the space through an orifice (35) formed in the shrink ring (21), Characterized in that the damping system also includes: - a second oil supply circuit (41), the second circuit being connected to at least one annular heating channel (40), the at least one annular heating channel being independent of the supply channel (34) and extending around the space (20), and the at least one annular heating channel being arranged corresponding to one of the sealing sections (26, 27).

2. The device according to claim 1, wherein: The supply channel (34) is formed in the annular support (22) or in the shrink ring (21).

3. The device according to claim 1 or 2, wherein: The or each heating channel (40) is formed in the annular support (22) and / or in the shrink ring (21).

4. A device according to any one of the preceding claims, wherein: The axial extent of the supply channel (34) is greater than the axial extent of the orifice (35).

5. A device according to any one of the preceding claims, wherein: The or each heating channel (40) has an axial extent greater than the axial extent of the sealing section (26, 27) around which the or each heating channel extends.

6. A device according to any one of the preceding claims, wherein: The second oil supply circuit (41) is connected to two heating channels (40a, 40b) respectively upstream and downstream, and the two heating channels are arranged corresponding to the sealing sections (26, 27).

7. A device according to any one of the preceding claims, wherein: The or each heating channel (40) is connected to at least one oil outlet orifice (44) formed in the shrink ring (21).

8. The device according to claim 7, wherein: The at least one oil outlet orifice (44) is axially offset from the space (20) to prevent oil exiting the orifice (44) from entering the space (20).

9. The device according to claim 6 and 7 or all of claims 6, 7 and 8, wherein: The oil outlet orifice (44) connected to the upstream heating channel (40a) opens upstream of the upstream sealing section (26) or even upstream of the second ring (24).

10. The device according to claim 6 and 7, or claim 6, 7 and 8, or all of claim 9, wherein: The oil outlet port (44) connected to the downstream heating passage (40b) opens downstream of the downstream sealing section (27).

11. The device according to any one of claims 7 to 10, wherein: The or each heating channel (40) is connected to at least one oil inlet aperture (43) formed in the bearing support (22).

12. The device according to claim 11, wherein The oil inlet and outlet orifices (43, 44) of the or each heating channel (40) are positioned at an angle less than or equal to 30°, preferably less than or equal to 20°, relative to each other.

13. The device according to claim 11 or 12, wherein: Similar to a clock face, the oil inlet opening (43) of the heating channel or each heating channel (40) is located in an angular area extending between 12 o'clock and 1 o'clock around the main axis of the device according to the first construction, or in an angular area extending between 11 o'clock and 12 o'clock around the axis according to the second construction, and the oil outlet opening (44) of the heating channel or each heating channel (40) is located in an angular area extending between 11 o'clock and 12 o'clock around the axis according to the first construction, or in an angular area extending between 12 o'clock and 1 o'clock around the axis according to the second construction.

14. A device according to any one of the preceding claims, wherein: The oil inlet orifice and the outlet orifice of the or each heating channel may be inclined relative to the radial direction.

15. A device according to any one of the preceding claims, wherein: The second ring of the guide means is associated with the flexible cage and comprises a hollow annular web connected to an annular fixing flange.

16. A device according to any one of the preceding claims, wherein: The or each heating channel may have an axial extent that is between one and five times the axial extent of the section with which that channel is associated.

17. A device according to any one of the preceding claims, wherein: When each supply channel is of the central type, the device comprises exactly two heating channels.

18. The device according to any one of claims 1 to 16, wherein: When the supply channel is of eccentric type, the device comprises a single heating channel.

19. An aircraft turbine engine comprising a shaft directed in rotation by a device according to any one of the preceding claims.

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