ASSEMBLY FOR RETAINING A GEAR TRAIN IN A TURBOMACHINE

Abstract

The present document relates to an assembly for retaining a gear train in a turbomachine, the assembly comprising an annular casing (44) in which is engaged an annular part (48) rotatably locked in the casing (44) by annular means of cogging comprising first annular means of coupling (50) formed on the annular part and co-operating with second annular means of coupling formed on the annular casing (44), wherein a film of oil is formed in an annular space bounded between the first means of coupling (50) and the second means of coupling.

Claims

1. An assembly for retaining a gear train (32) in a turbomachine, the assembly comprising an annular casing (44) in which an annular part (48) is engaged and rotationally fixed in the casing (44) by annular means of cogging comprising first annular means of coupling (50) formed on the annular part and cooperating with second annular means of coupling (56) formed on the annular casing (44), wherein an oil film is formed in an annular space defined between the first means of coupling (50) and the second means of coupling (56), the first means of coupling (50) and the second means of coupling (56) being axially arranged between a first annular seal (66a) and a second annular seal (66b) each clamped between the annular part (48) and the casing (44) the first means of coupling (50) comprising first teeth (50) extending radially outwardly and arranged circumferentially in alternation with second teeth (56) of the second means of coupling, the second teeth extending radially inwardly said first teeth (50) extending axially from a first radial annular wall (54) of the ring member (48) which is arranged axially opposite the free axial ends of said second teeth (56), said second teeth (56) extending axially from a second radial annular wall (58) of the casing which is arranged axially opposite the free ends of the first teeth (50).

2. An assembly according to claim 1, wherein one of the annular part (48) and the casing (44) comprises an oil-inlet channel (68) of the said annular space.

3. An assembly according to claim 1 or 2, wherein each first tooth (50) comprises circumferential radial end faces (50a, 50b) and circumferentially faces (56a, 56b) opposite radial circumferential end faces of each second tooth (56).

4. An assembly according to any of claims 1 to 3, wherein each first (50) tooth comprises a radially outer end face (50c) arranged radially opposite a face (57) of the casing (44).

5. An assembly according to any of claims 1 to 4, wherein each second tooth (56) comprises a radially inner end face (56c) arranged radially opposite a face (52) of the annular part (48).

6. An assembly according to any of claims 1 to 5, wherein each first (50) tooth comprises a radially outer end face (50d) arranged radially opposite a face (59) of the casing (44).

7. An assembly according to any of claims 1 to 6, wherein each second tooth (56) comprises a radially inner end face (56d) arranged radially opposite a face (61) of the annular part.

8. An assembly according to any of claims 1 to 7, wherein the first annular seal (66a) is radially interposed between the radially outer end of the first annular wall (54) and a radially facing cylindrical surface (64) of the casing (44).

9. An assembly according to claims 1 to 8, wherein the second annular seal (66b) is radially interposed between the radially inner end of the second annular wall (58) and a radially facing cylindrical surface (52) of the annular part (48).

10. An assembly comprising an assembly according to any of the preceding claims and a gear train (32) having an inner planetary gear (36) and an outer planetary gear (38) and planet gears (34) meshing with the inner planetary gear (36) and the outer planetary gear (38), and each mounted for free rotation on a satellite carrier (42).

11. An assembly according to claim 10, wherein the annular part (48) is attached to the outer planetary gear (38) or to the satellite carrier (42).

Description

BRIEF DESCRIPTION OF THE FIGURES

[0028] FIG. 1 is a schematic view, in perspective, of a turbomachine according to the known technique;

[0029] FIG. 2 is a cross-sectional schematic view of an epicyclic gear train intended to be used in a turbomachine according to FIG. 1;

[0030] FIG. 3 comprises a left-hand part, named FIG. 3A, showing in perspective an annular part intended to be mounted in a casing shown in perspective on the right-hand part, named FIG. 3B;

[0031] FIG. 4 is a perspective schematic of an assembly of the annular part of FIG. 3A into the casing of FIG. 3B;

[0032] FIG. 5 comprises a left-hand part, named FIG. 5A representing the assembly of FIG. 4 according to a first cutting plane and a right-hand part, named FIG. 5B, representing the assembly of FIG. 4 according to a second cutting plane circumferentially offset from the first cutting plane;

[0033] FIG. 6 comprises a left-hand part, named FIG. 6A, showing the oil introduction between the annular part and the casing, and a right-hand part, named FIG. 6B, showing the clearances between the annular part and the casing in cross-section along a transverse plane.

DETAILED DESCRIPTION OF THE INVENTION

[0034] First of all, reference is made to FIG. 1, which represents a schematic view of a turbomachine 10 according to the known technique comprising, from upstream to downstream, a fan wheel 12, the rotation of which induces an acceleration of air in an annular secondary air stream 14 (air flow B) surrounding successively from upstream to downstream, an annular primary air stream 16 (air flow A) flowing into a low-pressure compressor 18, a high-pressure compressor 20, an annular combustion chamber 22, a high-pressure turbine 24 and a low-pressure turbine 26. Classically, the low-pressure turbine 26 rotates the rotor 30 of the low-pressure compressor, which is connected to the fan wheel 12. However, in order to limit the rotational speed of the fan wheel 12 relative to the rotational speed of the rotor 30 of the low-pressure compressor 18, it is known to mount a reduction gear 32 radially inside the low-pressure compressor 18 to reduce the output speed. As illustrated in FIG. 2, such a gear train 32 comprises planet gears 34 meshing with an inner planetary gear 36 or central gear and an outer planetary gear 38 or outer crown, the inner planetary gear 36 and the outer planetary gear 38 being coaxial with the X axis of the turbomachine. Each planet gear 34 is mounted freely rotatable around a pivot 40 and the pivots 40 are integral with a satellite carrier 42. In a planetary reduction gear, the centre gear 36 is integral in rotation with the shaft 30 of the low-pressure compressor 18, which forms an input of a gear train, the satellite carrier 42 is stationary, and the outer crown 38 is made integral with the fan wheel 12 and forms an output for reducing the speed of the gear train. The casing 44 of the turbomachine externally delimits an annular enclosure 46 in which the gear train is mounted. In an epicyclic reduction gear, the satellite carrier forms an output for reducing the speed of the gear train and is made integral with the fan wheel 12, the outer planetary gear being integral with the casing. In both cases, the satellite carrier when fixed or the outer planetary gear when fixed is connected to the casing by a annular part. The object of the present invention is to provide a particular embodiment of an assembly for holding a gear train 32 in a turbomachine.

[0035] FIG. 3A shows a annular part 48 intended for connection to the satellite carrier 42 in a planetary reduction gear assembly or to the outer planetary gear 38 in an epicyclic reduction gear. Only part of the casing 44 is shown in FIG. 3B. As can be seen, the annular part 48 comprises first means of coupling formed by a plurality of first teeth 50 projecting radially outwards from an annular wall and more precisely from a cylindrical surface 52 facing radially outwards (FIG. 3A, FIGS. 5A and 5B). The first teeth 50 extend axially from a first radial annular wall 54 of the annular part 48. Each first tooth 50 has a substantially block-like profile comprising substantially flat faces. The first teeth 50 cooperate with second means of coupling of the casing 44. These second means of coupling comprise second radial teeth 56 evenly spaced circumferentially from each other. The second teeth 56 extend axially from a second radial annular wall 58 and circumferentially define between them recesses 60 for receiving the first teeth 50. Similarly, the first teeth 50 define circumferential recesses 62 between them for receiving the second teeth 56.

[0036] When the annular part 48 is mounted in the casing 44, the axial free ends of the first teeth 50 axially face the second radial annular wall 58 of the casing 44 and the axial free ends of the second teeth 56 axially face the first radial annular wall 54 of the casing 44.

[0037] As can be seen in FIG. 5, the first radial annular wall 54 is mounted in the casing 44 so that its radially outer end is arranged opposite a cylindrical surface 64 of the casing 44. Similarly, the radially inner end of the second radial annular wall 58 is arranged radially opposite the cylindrical surface 52 of the annular part 48.

[0038] A first annular seal 66a is radially interposed between the radially outer end of the first radial annular wall 54 and the cylindrical wall of the casing and a second annular seal 66b is radially interposed between the cylindrical face or surface 52 of the annular part 48 and the radially inner end of the second radial annular wall 58.

[0039] Each first tooth 50 comprises circumferential end faces 50a, 50b extending radially and circumferentially opposite radially extending circumferential end faces 56a, 56b of each second tooth 56 (FIG. 6B). Each first tooth 50 comprises a radially outer end face 50c arranged radially opposite a face 57 of the casing 44 (FIG. 6B). Each second tooth 56 comprises a radially inner end face 56c arranged opposite the face 52 of the annular part 48 (FIG. 5A). Each first tooth 50 can comprise a radially outer end face 50d arranged radially opposite a face 59 of the casing 44. Each second tooth 56 can comprise an axial end face 56d arranged axially opposite a face 61 of the annular part 44. This face 61 being a downstream face of the radial annular wall 54. As there are several teeth 50, 56, it is understood that there are several faces as mentioned above.

[0040] To allow oil to flow through the annular space formed between the first teeth 50 and the second teeth 56, it is necessary to size the annular part 48 and the casing 44 so that: [0041] clearances exist, in the circumferential direction, between the first teeth 50 and the second teeth 56, more specifically between the faces 50a and 56a and between the faces 50b and 56b [0042] clearances exist radially between the radially outer faces of the first teeth 50 and the casing 44 and between the radially inner faces of the second teeth 60 and the annular part 48, more specifically between the faces 56c and 52 and between the faces 50c and 57.

[0043] Also, oil also lodges itself between the axial ends of the first teeth 50 and the second radial annular wall 58 and between the axial ends of the second teeth 56 and the first radial annular wall 54, more specifically between the faces 56d and 61 and between the faces 50d and 59. The oil is inserted through a channel 68 formed in the second radial annular wall of the casing, this channel 68 opening between the first annular seal 66a and the second annular seal 66b. It is understood that the oil could also be inserted through a channel 68 formed in the annular part 48.

[0044] The use of a film of oil between the first teeth 50 and the second teeth 56 allows for the damping of the movements of the annular part 52 relative to the casing 44. Thus, when the annular part 48 is integral with a satellite carrier 42 or an outer planetary gear 38 of a gear train 32 as illustrated in FIG. 2, it is possible to limit the transmission of vibrations to the casing 44 and the rest of the turbomachine.