BEARING FOR AIRCRAFT TURBOMACHINE GEARBOX, GEARBOX AND TURBOMACHINE EQUIPPED WITH SUCH A GEARBOX

Abstract

This bearing, particularly for an aircraft turbomachine gearbox, comprises a roller (18), an outer ring (20), and an inner ring (21). The roller includes, at at least one of its mutually opposite ends, teeth (24) designed to cooperate with corresponding teeth of the outer and inner rings. The teeth (24) of the roller are inscribed within the outer diameter of the roller, said teeth having a tip diameter (C) inscribed in a curve (C) generating the roller. Figure for the abbreviation: Fig 2

Description

Title of the invention: BEARING FOR AIRCRAFT TURBOMACHINE REDUCER, REDUCER AND TURBOMACHINE EQUIPPED WITH SUCH A REDUCER Technical field

[0001] The invention relates, in general, to aircraft turbomachinery and relates in particular to a roller bearing for aircraft turbomachinery.

[0002] In one application, the invention relates to a roller bearing for an aircraft turbomachine reducer. Previous techniques

[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] With regard to aircraft turbomachinery, in particular double-flow turbomachinery, especially those with a very high bypass ratio, the mechanical reducer has the role of driving the shaft of a fan by transforming the so-called high rotational speed of the shaft of a power turbine into a slower rotational speed for the shaft driving the fan.

[0005] Aircraft turbomachine gearboxes must be compact and efficient.

[0006] A reducer is an epicyclic or planetary train which includes a central pinion, called the sun gear, a ring gear and satellites which are in contact between the sun gear and the ring gear.

[0007] The satellites are held by a frame called a satellite carrier. These satellites are sized according to the load on the gear teeth and the load on the bearings, which can be roller bearings. In many cases, reducing the size of the bearing while maintaining its load capacity makes it possible to reduce the overall size and mass of the gearbox.

[0008] Roller bearings consist of rollers, an outer ring, an inner ring, and often a cage that holds the rollers in place. This cage ensures spacing between the rolling elements to prevent contact between them, as contact between two rotating rolling elements generates slippage, which reduces both the efficiency and reliability of the bearing.

[0009] To improve the performance of a bearing, it is advantageous to maximize the number of rollers supporting the load. Increasing the number of rolling elements in a bearing, with constant roller and ring diameters, requires reducing the spacing between each roller. Beyond a certain roller spacing, it is no longer possible to integrate a properly sized cage. Therefore, the cage must be removed.

[0010] Cageless bearings exist. However, they generate roller-to-roller contact and consequently generate more loss and wear. Description of the invention

[0011] In view of the foregoing, the object of the invention is to propose a roller bearing, in particular for an aircraft turbomachine reducer, which makes it possible to increase the number of rollers supporting the load, while in particular making it possible to eliminate the cage, and avoiding any contact between the rollers.

[0012] The invention therefore relates to a bearing, in particular for an aircraft turbomachine reducer, comprising a roller, an outer ring and an inner ring, the roller comprising at least one of its mutually opposed ends a toothing intended to cooperate with a corresponding toothing of the outer and inner rings.

[0013] The teeth of the roller are inscribed in the outer diameter of the roller, said teeth comprising a head diameter inscribed in a generating curve of the roller.

[0014] Thus, the indexing of the roller is carried out by means of the teeth, which do not perform any force transmission function and the manufacturing problems of the bearing are avoided.

[0015] It will advantageously be provided that the tooth tip diameter satisfies the relation:

[0016] 0a = 0d + 2(cha + x)m(r)

[0017] In which:

[0018] Cha is the projection of the teeth;

[0019] x is the offset of the teeth;

[0020] 0a is the head diameter;

[0021] 0d is the pitch diameter.

[0022] m is the module of the gear teeth,

[0023] With:

[0024] m = z being the number of teeth in the toothing. z.

[0025] With such a tooth configuration, the tooth offset is negative.

[0026] Advantageously, the roller has teeth at each end.

[0027] It should be noted that the pitch diameter of the or each tooth can be equal to the diameter of the rolling surface of the roller and greater than the diameter of the head of the roller.

[0028] Advantageously, the tooth or teeth of the roller are herringbone teeth.

[0029] In one embodiment, the teeth of at least one of the outer and inner rings are reported.

[0030] For example, the sum of the teeth of the external and internal raceways is divisible by the number of rollers.

[0031] The invention also relates to a reducer for an aircraft turbomachine, comprising a set of satellites supported by bearings, in which the bearings comprise a bearing as defined above.

[0032] The invention also relates to an aircraft turbomachine, comprising a reducer as defined above. Brief description of the drawings

[0033] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings in which:

[0034] Fig. 1 schematically illustrates an aircraft turbomachine, equipped with a reducer according to the invention;

[0035] The [Fig.2] is a schematic view of a roller bearing of the reducer of the turbomachine of the [Fig.1];

[0036] The [Fig.3] is a schematic view of an example of the implementation of a bearing tooth of the [Fig.2];

[0037] Fig. 4 is a front view of a roller bearing according to the invention, showing helical teeth;

[0038] [Fig.5] is a cross-sectional view along line AA of [Fig.4];

[0039] Figures [Fig. 6] and [Fig. 7] are respectively front and sectional views along the line BB of [Fig.6] of another example of an embodiment of a roller bearing according to the invention, having teeth at each end of the roller;

[0040] Figures [Fig.8] and [Fig.9] illustrate examples of the realization of tracks which mesh with the rolling of Figures 6 and 7;

[0041] Fig. 10 illustrates a particular embodiment of a roller according to the invention;

[0042] Figure 11 shows a bearing equipped with the roller of Figure 10; and

[0043] Figure 12 schematically illustrates one embodiment of a double reducer floor equipped with a roller bearing according to the invention. Detailed description

[0044] Figure [Fig. 1] shows a turbomachine for an aircraft according to the invention, designated by the general numerical reference 1, with axis XX.

[0045] The invention relates essentially to the turbomachine reducer and the bearings of the low pressure and high pressure bodies, only the part located upstream of the turbomachine combustion chamber has been illustrated in [Fig.1]

[0046] The turbojet 1 is a turbofan engine which has at the front, considering the direction of the airflow admitted into the turbojet, a fan 2 which is carried by a fan shaft 3 connected to the reducer 4, then a low pressure compressor 5 and a high pressure compressor 6.

[0047] Downstream, behind the high-pressure compressor, the turbomachine 1 also includes a combustion unit and then, successively, a high-pressure turbine which supplies air to said combustion unit and, further downstream, a low-pressure turbine.

[0048] The hot gases from the combustion pass through the high-pressure turbine which drives the blower before escaping through an exhaust nozzle.

[0049] The reducer 4 has the role of driving the blower shaft 3 by transforming the so-called high rotation speed of the shaft line into a slower rotation speed for the blower shaft.

[0050] It drives the compressors 5 and 6 via a shaft line comprising an input shaft 7, rotationally linked to the reducer, a low pressure shaft 8, linked to the low pressure compressor 5 and a high pressure shaft 9 linked to the high pressure compressor 6.

[0051] The blower shaft 3, the inlet shaft 7, and the low pressure shafts 8 and high pressure shafts 9 rotate in bearings 10, 11 and 12.

[0052] The reducer is generally of the planetary or epicycloidal type.

[0053] It includes a solar 13 which receives the driving torque, a ring 14, which transmits the output torque to the blower shaft 3, and satellites 15 carried by satellite carriers 16 which are engaged between the solar 13 and the ring 14.

[0054] The satellites are supported by bearings made of roller bearings 17.

[0055] With reference to Figures 2 to 5, the roller bearings 17 are devoid of cage and each include a roller 18 having a peripheral bearing surface 19, an outer ring 20 and an inner ring 21 (figures 4 and 5) defining respectively an outer bearing track 22 and an inner bearing track 23 for the bearing surface 19.

[0056] At least one of the mutually opposite ends of the roller is equipped with an external toothing 24 which meshes both with a corresponding toothing of the external track and with a corresponding toothing of the internal track.

[0057] In the embodiment shown in [Fig.2], the ends of the roller are each equipped with an external tooth 24. However, it does not depart from the scope of the invention when only one of the ends of the roller is equipped with a tooth.

[0058] Each tooth of the roller is inscribed within the external diameter of the roller. As can be seen in [Fig. 2], the peripheral rolling surface 19 is generally convex and has a curvature with convexity facing outwards from the roller. Thus, each tooth or teeth are inscribed in the curve C generating the roller, being located radially internally with respect to the curve C. This characteristic makes it possible in particular to ensure the possibility of manufacturing the bearing.

[0059] Furthermore, the pitch diameter of the teeth 0d, which corresponds to the area of ​​the teeth where there is no slippage, is identical to the maximum diameter of the roller. Thus, the pitch diameter is located on the same non-slip diameter of the roller, in order to ensure the absence of slippage on the raceway. In other words, compared to a conventional tooth configuration in which the pitch diameter is generally located in the middle of the tooth, the pitch diameter of the teeth is here radially offset outwards, at the level of the maximum diameter of the bearing surface.

[0060] Furthermore, the tip diameter 0(l) of the teeth is less than the pitch diameter 0^ (0a < 0d). To this end, in order to ensure that 0a < 0d, each tooth satisfies the following relationship: [006i] 0^ = 0d + 2(cha + x)m^

[0062] In which:

[0063] Cha is the projection of the teeth;

[0064] x is the offset of the teeth;

[0065] 0a is the head diameter;

[0066] 0d is the pitch diameter.

[0067] m is the module of the teeth,

[0068] With:

[0069] m = z, where z is the number of teeth in the gear teeth.

[0070] Thus, in relation (1), the term 2{Cha + x)m is negative constant, i.e.:

[0071] Cha + x<0 (2)

[0072] and

[0073] Cha<-x0)

[0074] The teeth therefore exhibit a negative offset, resulting in a tooth shape with a widened head and a hollowed shank. Figure 3 shows an example of teeth meeting the criteria of equation (1) and whose drive ratio is greater than 1.

[0075] Such a bearing advantageously has a number of teeth on the roller teeth and on the external and internal raceways adapted for mounting the rollers equidistantly. Advantageously, the sum of the teeth on the external and internal raceways is divisible by the number of rollers.

[0076] This bearing can have a high roller density, with a very small distance between its rollers, much less than 15% of the roller diameter.

[0077] The bearing may have specific characteristics. Indeed, the curvature of the rolling surface 19 may have a circular or logarithmic geometry

[0078] As previously stated, the teeth may be present on only one side of the roller, which meshes with a corresponding set of teeth on the outer track and the inner track, always on the same side.

[0079] Alternatively, the roller may be provided with teeth at each end, which mesh with teeth provided on each side of the outer and inner tracks. In this case, however, at least one of the teeth on the outer or inner track shall be provided as a separate piece to allow for roller mounting.

[0080] Moreover, in various embodiments, the teeth can be straight, helical or herringbone.

[0081] In the embodiment illustrated in Figures 4 and 5, the bearing comprises a roller having teeth at both ends of the roller. These teeth are helical and perfectly symmetrical to each other in order to form a chevron on either side of the roller.

[0082] These teeth mesh with the respective teeth of the tracks of the outer ring 20 and the inner ring 21. However, the teeth of at least one of the outer and inner rings are added. The teeth 25 of the outer ring are added and are held in place by means of a nut 26.

[0083] The herringbone teeth ensure axial retention of the roller. Thus, the outer and inner ring(s) may be provided with one or more shoulders 27 on which the roller rests, this shoulder being oversized so as to present a clearance relative to the roller in order to allow a degree of axial movement freedom of the roller.

[0084] In the embodiment shown in Figures 6 to 9, in which teeth are also provided at both opposite ends of the roller, on one of the outer and inner tracks, teeth are also provided on each side. On this double-toothed track, it is also possible to provide shoulders 27.

[0085] On the other track, only one end is toothed. On this track, the teeth can be wider to obtain axial freedom of movement of the rollers.

[0086] With reference to [Fig. 10], when using straight teeth, which do not provide any axial support for the roller, it is advantageous to provide the track with two end teeth to have a shoulder 27 to axially retain the roller. In this latter case, the roller has a slight overthickness 28 on one of its end faces, on a disk with a diameter DI smaller than the diameter D2 of the foot of The tooth of the teeth ensures contact with the shoulder. This way, the shoulder will not experience any variation in contact with the roller.

[0087] With reference to [Fig. 11], in this embodiment, the outer and inner rings are devoid of a smooth surface, and the load is entirely received by the teeth, here referred to with regard to the outer ring.

[0088] It should be noted that, in this embodiment, the number of rollers may be different from the number of teeth per roller.

[0089] Furthermore, the quality class of the teeth of each roller can be defined so that the play in the teeth is less than half the nominal distance between two rollers.

[0090] For a ring without a shoulder, the teeth can be dimensioned with a tooth root diameter that protrudes from the diameter of the track, having a smaller tooth root diameter on the outer ring side and a larger root diameter on the inner ring, in order to ensure simpler machining.

[0091] Finally, it should be noted that in the embodiments described above, the roller bearing constitutes a bearing for a turbomachine gearbox satellite of an aircraft.

[0092] Such a bearing can also be used to make other types of bearings integrated into an aircraft engine.

[0093] Such a bearing can thus be used to make the bearing 10 of the blower shaft, the bearing 11 for the input shaft, or the bearing 12 for the high pressure shaft.

[0094] As seen in [Fig. 12], with regard to the realization of a bearing for a reducer, such a bearing 17 can be integrated into a two-stage reducer to maintain and guide a two-stage satellite 29 30 and 31 in contact with two stages 32 and 33 of a ring 34.

Claims

Demands

1. Bearing, in particular for aircraft turbomachine reducer, comprising a roller (18), an outer ring (20) and an inner ring (21), the roller comprising at at least one of its mutually opposed ends a tooth (24) intended to cooperate with a corresponding tooth of the outer and inner rings, characterized in that the tooth (24) of the roller is inscribed in the outer diameter of the roller, said tooth comprising a head diameter (0) inscribed in a curve (C) generating the roller.

2. Bearing according to claim 1, wherein the tooth tip diameter substantially satisfies the relation: 0a = 0d + l(çha + x}m^ Where: Cha is the tooth tip protrusion; x is the tooth offset; 0a is the tip diameter; 0^ is the pitch diameter. m is the tooth module, With: m = 4¾ z being the number of teeth in the tooth set.

3. Bearing according to one of claims 1 and 2, wherein the offset (x) of the teeth is negative.

4. Bearing according to any one of claims 1 to 3, wherein the roller (18) has at each end a tooth (24).

5. , Bearing according to any one of claims 1 to 3, wherein the pitch diameter of the or each tooth (24) is equal to the diameter of the rolling surface (19) of the roller and is greater than the head diameter of the roller.

6. Bearing according to any one of claims 1 to 5, wherein the tooth(s) (24) of the roller are herringbone teeth.

7. Bearing according to any one of claims 1 to 6, wherein the teeth (25) of at least one of the outer (20) and inner (21) rings are reported.

8. Bearing according to any one of claims 1 to 7, wherein the sum of the teeth of the outer and inner raceways is divisible without remainder by the number of rollers.

9. Aircraft turbomachine reducer, comprising a set of satellites supported by bearings, characterized in that the bearings comprise a bearing according to any one of claims 1 to 8.

10. Aircraft turbomachine, comprising a reducer according to claim 9.