Bearing for a reduction gear of an aircraft turbine engine, reduction gear and turbine engine equipped with such a reduction gear

Abstract

This bearing, in particular for a reduction gear of an aircraft turbine engine, comprises a roller (18), an outer ring (20) and an inner ring (21), the roller comprising, at at least one of its mutually opposing ends, a series of teeth (24) intended to mesh with a corresponding series of teeth of the outer and inner rings. The series of teeth (24) of the roller lies within the outer diameter of the roller, said series of teeth comprising an addendum circle (Øa) that lies within a generatrix curve (C) of the roller.

Description

[0001] DESCRIPTION

[0002] TITLE: BEARING FOR REDUCER

[0003] AIRCRAFT TURBOMACHINE, REDUCTION GEARBOX AND TURBOMACHINE EQUIPPED WITH SUCH A REDUCTION GEARBOX

[0004] technical field

[0005] The invention relates, in general, to aircraft turbomachinery and relates in particular to a roller bearing for aircraft turbomachinery.

[0006] In one application, the invention relates to a roller bearing for an aircraft turbomachine gearbox.

[0007] Previous techniques

[0008] The role of a mechanical reducer is to change the speed and torque ratio between the input and output shafts of a mechanical system.

[0009] With regard to aircraft turbomachinery, particularly dual-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.

[0010] Gearboxes for aircraft turbomachinery must be compact and efficient.

[0011] A reducer is an epicyclic or planetary train which includes a central pinion, called the sun gear, a ring gear and satellites which are engaged between the sun gear and the ring gear.

[0012] 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 allows for a reduction in the overall size and mass of the gearbox.

[0013] 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; contact between two rotating rolling elements generates slippage, which reduces both the efficiency and reliability of the bearing.

[0014] To improve bearing performance, it is beneficial 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.

[0015] Cageless bearings exist. However, they generate roller-to-roll contact and consequently lead to more loss and wear.

[0016] Description of the invention

[0017] In view of the above, the aim of the invention is to provide a roller bearing, in particular for an aircraft turbomachine gearbox, which allows the number of rollers supporting the load to be increased, while in particular allowing the cage to be eliminated, and avoiding any contact between the rollers.

[0018] 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.

[0019] The roller teeth are inscribed within the roller's outer diameter, with the teeth having a tip diameter that lies within a curve that generates the roller. Thus, roller indexing is achieved via the teeth, which do not perform any force transmission function, and bearing manufacturing problems are avoided.

[0020] It is advantageous to assume that the tooth tip diameter satisfies the following relationship:

[0021] 0 a = 0 d + 2(Ch a + x)m (1 )

[0022] In which:

[0023] Ch ais the projection of the teeth; x is the offset of the teeth;

[0024] 0 a is the head diameter;

[0025] 0 d is the pitch diameter. m is the module of the gear teeth.

[0026] With: m = —, z being the number of teeth in the gear. z

[0027] With such a tooth configuration, the tooth offset is negative.

[0028] Advantageously, the roller has teeth at each end.

[0029] It should be noted that the pitch diameter of the tooth or teeth can be equal to the diameter of the rolling surface of the roller and greater than the diameter of the roller head.

[0030] Advantageously, the tooth(s) of the roller are herringbone teeth.

[0031] In one embodiment, the teeth of at least one of the outer and inner rings are added.

[0032] For example, the sum of the teeth of the external and internal raceways is divisible by the number of rollers.

[0033] The invention also relates to a gearbox for an aircraft turbomachine, comprising a set of planetary gears supported by bearings, in which the bearings comprise a rolling bearing as defined above. The invention further relates to an aircraft turbomachine, comprising a gearbox as defined above.

[0034] Brief description of the drawings

[0035] 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:

[0036] Figure 1 schematically illustrates an aircraft turbomachine, equipped with a reducer according to the invention;

[0037] The [Fig 2] is a schematic view of a roller bearing of the turbomachine reducer in Figure 1;

[0038] The [Fig 3 ] is a schematic view of an example implementation of a bearing toothing of figure 2;

[0039] The [Fig 4] is a front view of a roller bearing according to the invention, showing helical teeth;

[0040] Figure 5 is a cross-sectional view along line AA of Figure 4;

[0041] Figures [Fig 6] and [Fig 7] are respectively front and cross-sectional views along line BB of Figure 6 of another example of an embodiment of a roller bearing according to the invention, having teeth at each end of the roller;

[0042] Figures 8 and 9 illustrate examples of track construction that mesh with the rolling of figures 6 and 7;

[0043] Figure 10 illustrates a particular embodiment of a roller according to the invention;

[0044] Figure 11 shows a bearing equipped with the roller of Figure 10; and

[0045] Figure 12 schematically illustrates an embodiment of a two-stage reducer equipped with a roller bearing according to the invention. Detailed description

[0046] Figure 1 shows a turbomachine for aircraft according to the invention, designated by the general numerical reference 1, with axis XX.

[0047] The invention essentially relates to the turbomachine gearbox and the bearings of the low-pressure and high-pressure bodies; only the part located upstream of the turbomachine combustion chamber is illustrated in Figure 1.

[0048] The turbojet 1 is a twin-flow turbojet 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.

[0049] 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.

[0050] The hot gases from combustion pass through the high-pressure turbine which drives the blower before escaping through an exhaust nozzle.

[0051] The role of the reducer 4 is to drive the blower shaft 3 by transforming the so-called high rotational speed of the shaft line into a slower rotational speed for the blower shaft.

[0052] It drives 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.

[0053] 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.

[0054] The reducer is generally of the planetary or epicyclic type. It includes a sun gear 13 which receives the driving torque, a ring gear 14, which transmits the output torque to the blower shaft 3, and satellites 15 carried by satellite carriers 16 which are meshed between the sun gear 13 and the ring gear 14.

[0055] The satellites are supported by bearings consisting of roller bearings 17.

[0056] Referring to figures 2 to 5, the roller bearings 17 are cageless and each comprise 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.

[0057] At least one of the mutually opposite ends of the roller is equipped with an external tooth 24 which meshes both with a corresponding tooth of the external track and with a corresponding tooth of the internal track.

[0058] In the embodiment shown in Figure 2, the ends of the roller are each equipped with an external tooth 24. However, we do not depart from the scope of the invention when only one of the ends of the roller is equipped with a tooth.

[0059] Each tooth or teeth of the roller are inscribed within the roller's external diameter. As can be seen in Figure 2, the peripheral bearing surface 19 is generally convex and has a curvature with its convexity facing outwards from the roller. Thus, each tooth or teeth are inscribed within the curve C generating the roller, being located radially inward with respect to the curve C. This characteristic, in particular, ensures the feasibility of manufacturing the bearing.

[0060] Furthermore, the pitch diameter of the teeth 0 dThe pitch diameter, which corresponds to the non-slip area of ​​the teeth, is identical to the maximum diameter of the roller. Thus, the pitch diameter is located on the same non-slip diameter of the roller, ensuring no slippage on the raceway. In other words, compared to conventional teeth where the pitch diameter is usually located in the middle of the tooth, the pitch diameter of this tooth is radially offset outwards, to the maximum diameter of the running surface.

[0061] Furthermore, the head diameter 0 a the tooth size is less than the pitch diameter 0 rf ( 0 a < 0 d ). To that end, in order to ensure that 0 a < 0 d Each tooth satisfies the following relationship:

[0062] 0 a = 0 d + 2(Ch a + x~)m (1 )

[0063] In which:

[0064] Ch ais the projection of the teeth; x is the offset of the teeth;

[0065] 0 a is the head diameter;

[0066] 0 d is the pitch diameter. m is the module of the gear teeth.

[0067] With: m = —, z being the number of teeth in the gear. z

[0068] Thus, in relation (1), the term 2 Ch a + xm is negative, i.e.:

[0069] Ch a + x < 0 (2) and

[0070] Ch a < -x (3)

[0071] The teeth therefore exhibit a negative offset, resulting in a tooth shape with a widened tip and a concave root. Figure 3 shows an example of teeth that meet the criteria of equation (1) and whose drive ratio is greater than 1. Advantageously, such a bearing has a number of teeth on the roller teeth and the outer and inner raceways adapted to mounting the rollers equidistantly. Advantageously, the sum of the teeth on the outer and inner raceways is divisible by the number of rollers.

[0072] This bearing can have a high roller density, with a very small distance between its rollers, much less than 15% of the roller diameter.

[0073] The bearing can have specific characteristics. Indeed, the curvature of the rolling surface 19 can be with a circular or logarithmic geometry

[0074] 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.

[0075] Alternatively, the roller can be fitted with teeth at each end, which mesh with teeth provided on each side of the outer and inner tracks. However, in this case, at least one of the teeth on the outer or inner track must be added to allow for roller mounting.

[0076] Furthermore, in various embodiments, the teeth can be straight, helical or herringbone.

[0077] 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.

[0078] 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 a nut 26.

[0079] The herringbone teeth ensure axial support of the roller. Thus, the outer and inner ring(s) can 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.

[0080] 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. Shoulders 27 can also be provided on this double-toothed track.

[0081] On the other track, only one end has teeth. On this track, the teeth can be wider to allow for greater axial movement of the rollers.

[0082] Referring to Figure 10, when using straight teeth, which do not provide axial support for the roller, it is advantageous to provide the track with two end teeth a shoulder 27 to axially retain the roller. In this case, the roller has a slight overthickness 28 on one of its end faces, on a disc with a diameter DI smaller than the tooth root diameter D2 of the teeth, to ensure contact with the shoulder. Thus, the shoulder will not experience any variation in contact with the roller.

[0083] With reference to Figure 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.

[0084] It should be noted that, in this embodiment, the number of rollers may be different from the number of teeth per roller.

[0085] 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.

[0086] For a ring without a shoulder, the teeth can be dimensioned with a root diameter that exceeds the raceway diameter, with a smaller root diameter on the outer ring and a larger root diameter on the inner ring to simplify machining. Finally, it should be noted that in the embodiments described above, the roller bearing serves as a support for a turbomachine gearbox planetary bearing in an aircraft.

[0087] Such a bearing can also be used to create other types of integrated bearings in an aircraft engine.

[0088] Such a bearing can therefore 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.

[0089] As can be seen in Figure 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 meshing with two stages 32 and 33 of a ring 34.

Claims

DEMANDS 1. Bearing, particularly for an aircraft turbomachine gearbox, 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 teeth (24) intended to cooperate with corresponding teeth of the outer and inner rings, characterized in that the teeth (24) of the roller are inscribed in the outer diameter of the roller, said teeth comprising a head diameter (0 a ) inscribed in a curve (C) generating the roll.

2. Bearing according to claim 1, in which the tooth tip diameter substantially satisfies the relation: 0 a = 0 d + 2(Ch a + x)m ( 1 ) In which: Ch a is the projection of the teeth; x is the offset of the teeth; 0 a is the head diameter; 0 dis the pitch diameter. m is the module of the gear teeth. With : 0 d m = —, z being the number of teeth in the gear. z 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 toothed section (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 diameter of the roller head.

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 external and internal bearing races 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 reduction gear according to claim 9.

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