Abstract:
A device for lubricating a turbomachine rolling bearing includes a rolling bearing mounted between an internal component and an external component. The bearing has rolling elements mounted between an outer ring secured to the external component and an inner ring secured to the internal component. The internal component includes at least one first duct for the passage of oil for supplying the internal ring of the bearing with oil, wherein the internal component is a stator component and at least one first duct is connected to an oil supply source configured to deliver the oil at a pressure high enough that this oil can be conveyed as far as the rolling elements of the bearing.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates in particular to a device and a method for lubricating a rolling bearing of a turbine engine. 
       PRIOR ART 
       [0002]    Conventionally, a turbine engine rolling bearing is mounted between an internal part and an external part, the bearing comprising rolling elements that are mounted between an external race that is rigidly connected to the external part, and an internal race that is rigidly connected to the internal part. 
         [0003]    A turbine engine bearing is generally lubricated by means of a nozzle that sprays oil onto the bearing or in the region of the bearing. 
         [0004]    In the prior art, in the case where the bearing is mounted between two rotor parts (the external race is rigidly connected to the external rotor part, and the internal race is rigidly connected to the internal rotor part) or between a rotor part and a stator part (the external race is rigidly connected to the external stator part, and the internal race is rigidly connected to the internal rotor part), the bearing is lubricated, during operation, by the oil which is transported by the internal race as far as the bearing by means of centrifugal forces. In this case, the internal rotor part comprises oil flow ducts for supplying oil to the internal race of the bearing, the radially internal ends of which ducts open into a trough for retaining oil supplied by a nozzle. On account of the centrifugal forces, the oil flows from the trough to the bearing, passing through the ducts of the internal part. 
         [0005]    However, this technology is not suitable in the case where the internal support part of the internal race of the bearing is a stator part, i.e. a part that is immobile during operation. Since the stator part is not subjected to centrifugal forces, there is currently no solution for effectively lubricating the bearing without oil being applied directly onto the bearing by means of a nozzle. 
         [0006]    The present invention proposes a simple, effective and economical solution to this problem. 
       DISCLOSURE OF THE INVENTION 
       [0007]    The invention proposes a device for lubricating a rolling bearing of a turbine engine, comprising a rolling bearing that is mounted between an internal part and an external part, the bearing comprising rolling elements that are mounted between an external race that is rigidly connected to the external part, and an internal race that is rigidly connected to the internal part, the internal part comprising at least one first oil flow duct for supplying oil to the internal race of the bearing, characterised in that the internal part is a stator part, and in that said at least one first duct is connected to an oil supply source that is designed to deliver oil at a sufficient pressure for said oil to be transported as far as the rolling elements of the bearing. 
         [0008]    The present invention thus proposes a solution to the above-mentioned problem in which the technology of the prior art is adapted so as to make it possible to lubricate a bearing that is mounted between an internal stator part and an external rotor part. This adaptation consists in connecting the ducts of the stator part to an oil supply source that is designed to deliver oil at a sufficient pressure for said oil to be transported as far as the bearing. In contrast with the prior art in which the oil is transported as far as the bearing by means of centrifugal forces, in this case the oil is transported as far as the bearing by means of the pressure at which the source supplies the oil, which oil is not subjected to any centrifugal force. 
         [0009]    The internal race preferably comprises substantially radial oil flow channels, the radially internal ends of which channels open into an annular cavity, such as an internal annular cavity of the internal race. 
         [0010]    According to a particular embodiment of the invention, an intermediate part, such as a sleeve, is interposed between the internal part and the internal race, said intermediate part comprising at least one second oil flow duct that is connected to said at least one first duct. 
         [0011]    The radially internal end of said at least one second duct can open into an annular cavity into which the radially external end of said at least one first duct opens. The cavity is an external annular cavity of the intermediate part, for example. 
         [0012]    Said at least one first duct can have a diameter that is different from that of said at least one second duct. 
         [0013]    Advantageously, said at least one first duct is in fluid communication with a recess for receiving an end of a pipe for supplying oil from said source. At least one seal can be mounted between the end of the pipe and the recess. 
         [0014]    Said at least one first duct preferably defines an oil flow cross section that is smaller than or equal to that of the pipe. In a variant or as additional features, said at least one second duct defines an oil flow cross section that is smaller than or equal to that of the pipe. The flow cross sections of the first and/or second ducts are thus advantageously designed such that said ducts have a calibration function. 
         [0015]    The present invention also relates to a turbine engine, such as a turboprop engine having at least one unducted propeller, characterised in that it comprises at least one device as described above. 
         [0016]    The present invention further relates to a method for lubricating a rolling bearing of a turbine engine, said bearing being mounted between an internal part and an external part, the bearing comprising an external race that is rigidly connected to the external part, and an internal race that is rigidly connected to the internal part, the internal part comprising at least one first oil flow duct for supplying oil to the internal race of the bearing, characterised in that, as the internal part is immobile, said method consists in supplying oil to said at least one first duct at a sufficient pressure for said oil to be transported as far as the bearing. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0017]    The invention will be better understood, and other details, features and advantages of the invention will become apparent upon reading the following description, given by way of non-limiting example with reference to the accompanying drawings, in which: 
           [0018]      FIG. 1  is a very schematic, axial sectional half view of a turboprop engine having a pair of unducted propellers, 
           [0019]      FIG. 2  is a schematic, axial sectional half view of a lubricating device according to the invention, 
           [0020]      FIGS. 3 and 4  are very schematic views of members of the device of  FIG. 2 , and show variants of the invention in a section perpendicular to the axis of the engine, all the oil flows being brought into the same plane in order to improve understanding, 
           [0021]      FIGS. 5 and 6  are schematic partial perspective views in axial section of the device of  FIG. 2 , 
           [0022]      FIG. 7  is a view which corresponds to  FIG. 2  and shows a variant of the invention, and 
           [0023]      FIGS. 8 to 10  are views which correspond to  FIGS. 3 and 4  and show further variants of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    Reference is first made to  FIG. 1  which shows a turboprop engine  1  for an aircraft, said turboprop engine being provided with a pair of contra-rotating propellers and referred to as “open rotor” or “unducted fan”. 
         [0025]    The turboprop engine  1  comprises an upstream propeller  2  and a downstream propeller  3  that are mounted so as to rotate in opposing directions about the longitudinal axis A. The turboprop engine  1  comprises a “gas generator” portion G that is located inside a stationary cylindrical nacelle  4  that is supported by the structure of the aircraft (such as the rear portion of the fuselage of an aeroplane), and a “propulsion” portion P comprising the pair of propellers  2 ,  3  arranged in parallel radial planes that are perpendicular to the axis A and forming an unducted fan (open rotor). In this example of a turboprop engine, this portion P extends the gas generator portion G and the nacelle  4 . 
         [0026]    The gas generator portion G of the turboprop engine  1  usually comprises, from upstream to downstream in the flow direction, with respect to the axis A, of the gaseous flow F entering the nacelle  4 , one or more compressors  5 ,  5 ′ according to the architecture of the gas generator having one or more bodies, an annular combustion chamber  6 , one or more turbines  7 ,  7 ′ having a distinct pressure according to said architecture, the shaft  8  of one of said turbines driving, by means of a device for reducing speed or a reducer  9  having epicyclic gears (PBG, or power gear box) and in a contra-rotating manner, the concentric and coaxial shafts  10  and  11  of the two propellers, upstream  2  and downstream  3 , that are aligned along the axis A of the turboprop engine. An exhaust nozzle  12  terminates the turboprop engine  1  in the usual manner. 
         [0027]    During operation, the airflow F entering the turboprop engine  1  is compressed and then mixed with fuel and burnt in the combustion chamber  6 . The combustion gases generated then pass into the turbines  7 ,  7 ′ in order to set the propellers  2 ,  3 , which supply the major part of the thrust, into reverse rotation, via the epicyclic reducer  9 . The combustion gases are expelled through the exhaust nozzle  12 , thus increasing the thrust of the turboprop engine  1 . 
         [0028]    As can be seen in  FIG. 1 , the radially internal shaft  11  surrounds a cylindrical stator sleeve  13  and is centred and rotatably guided about said sleeve by means of at least one rolling bearing  14  that has to be lubricated in order to ensure the proper operation thereof. 
         [0029]    As described above, the prior art cannot be used for lubricating this bearing  14  since the sleeve  13  is immobile during operation and the oil in contact with said sleeve  13  is not subjected to any centrifugal force. 
         [0030]      FIG. 2  shows an embodiment of a device according to the invention for lubricating a rolling bearing. In this drawing, the reference signs  13  and  14  denote the sleeve and the bearing, respectively, as is the case in  FIG. 1 . 
         [0031]    The bearing  14  conventionally comprises two races, internal  15  and external  16 , respectively, between which rolling elements  17  such as balls or rollers are mounted, which elements are, in this case, kept at a distance from one another by means of an annular cage  18 . 
         [0032]    The internal race  15  comprises two annular rows, upstream and downstream, respectively, of oil flow channels  19 . Said channels  19  are substantially radial, the radially external ends thereof opening onto the rolling track of the race  15  and the radially internal ends thereof opening into an internal annular cavity  20  of the race  15 . 
         [0033]    In the example shown, the internal race  15  of the bearing  14  is mounted on a race support  30  which is itself mounted on the sleeve  13  inside which an internal part  21  is mounted. The internal race  15 , the race support  30 , the part  21  and the sleeve  13  are coaxial and are rigidly interconnected. They are thus all immobile during operation, in contrast with the external race  16  of the bearing  14  which is fixed to the rotor shaft  11  of  FIG. 1  for conjoint rotation. 
         [0034]    The race support  30  comprises an annular row of oil flow ducts  31 . Said ducts  31  are substantially radial. The radially external ends thereof open into the cavity  20  of the race  15 , and the radially internal ends thereof open into an external annular cavity  32  of the sleeve  13 . 
         [0035]    The sleeve  13  comprises an annular row of oil flow ducts  22 . Said ducts  22  are substantially radial. The radially external ends thereof open into the cavity  32 , and the radially internal ends thereof open into an external annular cavity  23  of the internal part  21 . 
         [0036]    The part  21  comprises at least one oil flow duct  24 . Said duct  24  is substantially radial. The radially external end thereof opens into the cavity  23 , and the radially internal end thereof opens into an internal recess  25  of the part  21 . 
         [0037]    In this case, the ducts  31 ,  22  and  24  extend in the same transverse plane P that passes substantially between the channels  19 , halfway between said channels. 
         [0038]    The recess  25  in the part  21  comprises a widened upstream portion  26  in which an end of a pipe  27  is fitted, the other end of which pipe is connected, directly or indirectly, to an oil source S. In this case, the end of the pipe  27  carries an O-ring seal  28  that engages with an internal wall of the recess  25  in order to ensure a sealed connection between the pipe  27  and the part  21 . In this case, the pipe  27  has a substantially axial orientation. Said pipe thus extends substantially in parallel with the above-mentioned axis A. 
         [0039]    Two annular seals  29  are mounted between the sleeve  13  and the part  21 , upstream and downstream, respectively, of the cavity  23 , in order to ensure sealed fluid connection between the ducts  22 ,  24 . 
         [0040]    The source S mainly comprises a pump and an oil reservoir (not shown). The source S is intended for supplying the device with oil at a sufficient pressure for the oil to be transported, purely on account of said pressure, from the reservoir as far as the bearing  14  (and in particular as far as the rolling elements  17 ), passing successively through the recess  25 , the duct  24 , the cavity  23 , the ducts  22 , the cavity  20  and the channels  19  (cf. arrows). 
         [0041]    In the example shown, and as is also shown schematically in  FIG. 3 , the flow cross section defined by the duct  24  is smaller than that of the ducts  22  (i.e. smaller than the cumulative flow cross sections of said ducts  22 ), and smaller than that of the ducts  31 ,  19 , of the pipe  27  and of the recess  25 . The flow cross section of the duct  24  is a calibrating flow cross section that is intended for calibrating the pressure of the oil supplying the bearing  14 . As the flow cross sections of the ducts  22  and of the ducts  31 ,  19  are larger than that of the duct  24 , the oil pressure will barely change while flowing in the ducts  22  and will therefore be substantially the same in the cavities  20  and  23 . Moreover, the cavities  23  and  20  are designed so as to change this pressure as little as possible. 
         [0042]      FIG. 4  shows a variant in which it is the ducts  19  that provide the oil pressure calibration function. The flow cross section defined by the ducts  19  (cumulative flow cross sections of said ducts  19 ) is smaller than that of the duct  24  and smaller than that of the ducts  31 ,  22  (cumulative flow cross sections of said ducts  31 ,  22 ), of the pipe  27  and of the recess  25 . The flow cross section of the ducts  19  is a calibrating flow cross section that is intended for calibrating the pressure of the oil supplying the bearing  14 . The pressure of the oil will therefore be changed while flowing in the ducts  19  and will be higher in the cavity  20  than in the cavity  23 . 
         [0043]    Other configurations may result from adding or eliminating parts between the internal part  21  and the internal race  15 . Indeed, if the race support  30  were not present, it would be possible to eliminate the ducts  31  and the cavity  32 , as is shown schematically in  FIGS. 7 to 9 . Likewise, it would be possible to add parts that are similar to the race support  30  and that comprise ducts similar to the ducts  31  and a cavity similar to the cavity  32 , i.e. having the non-calibrating cross section of the various elements for the system. 
         [0044]      FIG. 10  shows an improvement of the embodiments shown in  FIGS. 8 and 9 . The parts  13 ,  21  and  15  may have an angular locating pin in order for the ducts  24 ,  22  and  19  to be positioned in the top portion of the engine. Advantageously, the duct  24  is positioned at 12:00 (or 12 o&#39;clock, by analogy with a watch face). The ducts  22  must cover an angular perimeter that is greater than that of the duct  24  and is centred on 12:00. The ducts  19  must cover an angular perimeter that is greater than that of the ducts  22 , is centred on 12:00 and is preferably smaller than or equal to [−90°; +90°].