FR3125319A1 - MECHANICAL ASSEMBLY AND MECHANICAL REDUCER OF AIRCRAFT TURBOMACHINE COMPRISING SUCH AN ASSEMBLY - Google Patents

Abstract

Mechanical assembly (150) for an aircraft turbomachine, this assembly comprising: - a part (156) comprising an external thread (170) and an external cylindrical surface (166) extending around the same axis (Y), - a rolling bearing (94) mounted on said surface (166), this bearing (94) comprising an inner ring (158) which is configured to be shrunk on said surface (166) and which bears on a cylindrical shoulder ( 168) of said part (156), and - a nut (152) having an internal thread (185) and configured to be screwed onto said thread (170) in order to axially lock said internal ring (158) against said shoulder (168) , said nut (152) having an internal diameter smaller than the external diameter (Dex) of said ring (158), said nut (152) and said shoulder (168) being located on the same side of the ring (158). Figure for abstract: Figure 6

Description

MECHANICAL ASSEMBLY AND MECHANICAL REDUCER OF AIRCRAFT TURBOMACHINE COMPRISING SUCH AN ASSEMBLY

Technical field of the invention

The present invention relates in particular to the field of mechanical reduction gears for turbomachines, in particular aircraft.

Technical background

The state of the art includes in particular the documents WO-A1-2010/092263, FR-A1-2 987 416, FR-A1-3 008 462, FR-A1-3 008 463 and FR-A1-3 041 054 .

The role of a mechanical gearbox is to modify the speed and torque ratio between the input axis and the output axis of a mechanical system.

The new generations of multi-flow turbomachines, in particular those with a high bypass ratio, include a mechanical reduction gear to drive the shaft of a propeller (also called a "fan"), for example a fan. Usually, the purpose of the reduction gear is to transform the so-called fast rotation speed of the shaft of a power turbine into a slower rotation speed for the shaft driving the fan.

Such a reducer comprises a central pinion, called sun gear, a crown and pinions called satellites, which are engaged between the sun gear and the crown. The satellites are held by a frame called the planet carrier. The solar, the crown and the planet carrier are planetary because their axes of revolution coincide with the longitudinal axis X of the turbomachine. The satellites have different axes of revolution evenly distributed over the same operating diameter around the axis of the planetary gears. These axes are parallel to the longitudinal axis X.

There are several reducer architectures. In the state of the art of multi-flow turbomachines, the reduction gears are of the planetary or planetary type. In other similar applications, there are so-called differential or “compound” architectures.

- On a planetary gearbox, the planet carrier is fixed and the crown constitutes the output shaft of the device which rotates in the opposite direction to the sun.

- On an epicyclic reduction gear, the crown is fixed and the planet carrier constitutes the output shaft of the device which rotates in the same direction as the sun gear.

- On a differential gearbox, no element is fixed in rotation. The crown rotates in the opposite direction to the sun and the planet carrier.

Reducers can be composed of one or more meshing stages. This meshing is ensured in different ways such as by contact, by friction or even by magnetic fields. There are several types of contact meshing such as straight, helical or chevron gears.

The increase in reduction ratios of target motor architectures leads to the use of so-called “double-stage” reduction gears. Indeed, beyond a ratio of the order of 6 or 7, the so-called "single stage" technology loses its interest because it is no longer compact enough. It is then necessary to use so-called “double-stage” reducers.

In a single stage technology, it is the same toothing of a satellite which cooperates with the sun and the crown. In a double-stage technology, the toothing of the satellite which cooperates with the sun is different from the toothing of the satellite which cooperates with the crown. In general, the teeth of a satellite which cooperate respectively with the solar and the corona have different average diameters.

The main problem with double-stage gearboxes (each stage or gearing comprising a single series of teeth) lies in the fact that they are asymmetrical with respect to a plane perpendicular to the X axis. Thus, the power entering downstream through inside and emerging upstream from the outside generates non-negligible moments at the level of the satellites (the expressions “upstream” and “downstream” referring to the general flow of gases in the turbomachine).

A solution to this problem consists in providing a symmetrical arrangement of the two gears with respect to a plane perpendicular to the X axis (each stage or gear having a double series of teeth). These two teeth are herringbone, i.e. they each have a series of upstream teeth separated axially from a series of downstream teeth. The upstream teeth are substantially parallel to each other and inclined relative to the X axis. The downstream teeth are also substantially parallel to each other and inclined relative to the X axis and relative to the upstream teeth so that the upstream teeth and downstream form chevrons all around the satellite. In a herringbone gear, the helix angle of the two series of teeth has the same value (and an opposite inclination), so that these series of teeth generate opposite axial forces of the same value.

The gearbox satellites must be supported and guided in rotation with respect to the planet carrier. The classic solutions to do this are to use bearings. Several technologies are possible such as plain bearings, roller bearings, etc. The integration of roller bearings is not easy because the bearings must be arranged symmetrically around each satellite and on either side of the aforementioned plane, which tends to increase the size of the gearbox.

However, the motor environment in which the gearbox must be integrated is constrained. Thus, the size of the reducer, in particular axial, can lead to an elongation of the motor and therefore an increase in the drag and mass of the motor, which reduces the performance of the latter. Likewise, the mass of the reducer negatively influences the performance of the system.

There is therefore a need to find a configuration in which the bearings perform their role effectively without impacting the axial bulk of the part on which they are mounted. To achieve this objective, and as illustrated in , the bearing A can be accommodated in a relatively limited annular space B. The bearing A comprises an outer ring C and an inner ring D between which are mounted rolling elements E which are here rollers. The inner ring D is mounted on an outer cylindrical surface F and bears axially on a cylindrical shoulder G.

The inner ring D of the bearing A is shrunk on the surface F. In the case of a roller bearing, the inner ring D does not theoretically take up any axial force. However, with the vibrations and parasitic forces, the shrinking force of the ring D is sometimes not sufficient to hold it in position and an H nut is then associated with this assembly to guarantee that the ring is held in position. internal d.

In the case illustrated in , the inner ring D can only be mounted from right to left because the geometry of the satellite on which the bearing A is mounted creates an obturation on the other side. This problem also applies to nut H which must be fitted after and on the opposite side to shoulder G.

Nut H thus generates additional axial space, while a space remains empty on the other side of bearing A.

Although the technical problem is presented in the context of a mechanical reducer, it also arises in other contexts, and in particular to any type of mechanical assembly requiring the maintenance of a rolling bearing by nut in an environment constrained.

The object of the invention is to provide a simple, effective and economical solution to this problem.

The invention relates to a mechanical assembly for an aircraft turbomachine, this assembly comprising:

- a part comprising an external thread and an external cylindrical surface extending around the same axis,

- a rolling bearing mounted on said surface, this bearing comprising an inner ring which is configured to be shrunk on said surface and which bears on a cylindrical shoulder of said part, and

- a nut comprising an internal thread and configured to be screwed onto said thread in order to axially block said internal ring against said shoulder, said nut comprising an internal diameter smaller than the external diameter of said ring,

characterized in that said nut and said shoulder are located on the same side of the ring, and in that the assembly further comprises an annular spacer which is mounted on the ring, said nut comprising an internal annular flange which bears axially on this annular spacer so as to apply an axial tensile force on this spacer as well as on the inner ring when screwing the nut.

The invention makes it possible to reduce the size, in particular axial, of the assembly by allowing the mounting of the nut on the same side as the shoulder. The nut can then be located in a relatively small space which was not exploited in the prior art.

The assembly can be used in the context of a reduction gear or in any other context requiring the axial retention of a rolling bearing by means of a nut.

The assembly according to the invention may comprise one or more of the following characteristics, taken separately from each other, or in combination with each other:

• said wedge is mounted on a cylindrical rim of the ring, one free end of which bears axially on said shoulder;
• said ring includes an outer annular rib at said free end;
• said rib of the ring is scalloped and comprises an annular row of external teeth, and said rim of the nut is scalloped and comprises an annular row of internal teeth configured to cooperate by dogging with the external teeth of the rib of the ring;
• said wedge is formed by a split ring;

-- the wedge is configured to be deformed by spreading its circumferential edges in order to be mounted on the ring, or to be mounted by rotation of the screwing type on the ring;

• said wedge is inserted axially between the rim of the ring and the rim of the nut;
• said wedge is mounted on the ring by a bayonet system;

-- the bayonet system comprises lugs carried by one of the elements chosen from the wedge and the ring, and L-shaped notches formed in the other of the elements chosen from the wedge and the ring;

-- the lugs are oriented radially or axially;

-- the lugs are configured to be engaged in the L-shaped notches, by displacement in translation of the ring and of the wedge towards each other, then by rotation of the ring and of the wedge relative to each other the other ; when the lugs are engaged in the L-shaped notches, the wedge and the ring are immobilized axially with respect to each other by cooperation of the lugs with the edges of the L-shaped notches;

• said wedge comprises a first axial and/or radially internal end mounted on the ring by the bayonet system, and a second axial and/or radially external end which comprises an external annular flange on which the flange of the nut bears axially ;
• said wedge comprises a cylindrical wall extending between said first and second ends and having an outer diameter smaller than said inner diameter of the nut;
• said nut comprises indentations and/or protrusions configured to allow engagement of a screwing tool;
• said part comprises a body extending around the axis, an annular wall carrying an external toothing and extending around the body, and an annular web extending radially between the body and the annular wall, the wall defining around the body an annular space for housing at least part of said bearing, and the nut which is located axially between the veil and this bearing;
• said part is a satellite of a mechanical reduction gear;

-- the bearing is roller bearing;

-- the inner ring comprises a first element and the part comprises a second element, these first and second elements being configured to cooperate together by complementarity of shapes in order to immobilize the ring in rotation on the part; And

-- the part includes an external toothing.

The invention also relates to a mechanical reduction gear for an aircraft turbine engine, comprising at least one assembly as described above.

The invention further relates to a turbomachine, in particular for an aircraft, comprising an assembly or a reducer as described above.

The invention also relates to a method for assembling an assembly as described above, characterized in that it comprises the steps of:

- assembly of the nut and the wedge on the bearing ring,

- shrinking of the bearing ring on the cylindrical surface of the part, until the ring is axially supported on the shoulder of the part,

- screwing the nut on the thread of the part so as to block the ring axially on the part.

The shim can be mounted on the ring after assembly or simultaneously with the assembly of the nut on the ring.

Brief description of figures

Other characteristics and advantages will emerge from the following description of a non-limiting embodiment of the invention with reference to the appended drawings in which:

there is a schematic half view in axial section of a mechanical assembly,

there is a schematic view in axial section of a turbomachine using the invention,

there is a partial view in axial section of a single-stage mechanical gear reducer,

there is a partial view in axial section and in perspective of a mechanical reduction gear with two meshing stages,

there is another schematic view in axial section of the reducer of the , and illustrates an embodiment of the invention,

there is a larger scale view of part of the reducer of the ;

there is a schematic partial half view in axial section of a nut and a shim of the gearbox of the ;

there is a schematic perspective view of the shim and an inner ring of the gearbox of the , and illustrates an assembly step of these parts;

there is a schematic perspective view of the nut, shim and part of the gear reducer bearing of the ;

there is a partial schematic perspective view of a satellite gear reducer ;

there is a view similar to that of the and illustrates a variant embodiment of the invention;

there is a schematic perspective view of a gear reducer nut ;

there is a view similar to that of the and illustrates a variant embodiment of the invention;

there is a view similar to that of the and illustrates a variant embodiment of the invention;

there is a schematic perspective view of the nut, shim and part of the gear reducer bearing of the ;

there is a schematic perspective view of an alternative embodiment of the shim of the reducer of the ; And

there is a schematic perspective view of another alternative embodiment of the shim of the reducer of the .

Claims (15)

Mechanical assembly (150) for an aircraft turbine engine, this assembly comprising:
- a part (156) comprising an external thread (170) and an external cylindrical surface (166) extending around the same axis (Y),
- a rolling bearing (94) mounted on said surface (166), this bearing (94) comprising an inner ring (158) which is configured to be shrunk on said surface (166) and which bears on a cylindrical shoulder ( 168) of said part (156), and
- a nut (152) comprising an internal thread (185) and configured to be screwed onto said thread (170) in order to axially block said internal ring (158) against said shoulder (168), said nut (152) comprising an internal diameter smaller than the outer diameter (Dex) of said ring (158),
characterized in that said nut (152) and said shoulder (168) are located on the same side of the ring (158), and in that the assembly (150) further comprises an annular spacer (154, 154' ) which is mounted on the ring (158), said nut (152) comprising an internal annular rim (186) which bears axially on this annular wedge (154, 154') so as to apply an axial tensile force on this wedge as well as on the inner ring (158) when screwing the nut (152). Assembly (150) according to claim 1, in which said shim (154, 154') is mounted on a cylindrical rim (174) of the ring (1658), one free end of which bears axially on said shoulder (168). An assembly (150) according to claim 2, wherein said ring (158) includes an outer annular rib (192) at said free end. An assembly (150) according to claim 3, wherein said rib (192) of the ring (158) is scalloped and includes an annular row of outer teeth, and said flange (186) of the nut (152) is scalloped and includes an annular row of internal teeth configured to cooperate by dog clutching with the external teeth of the rib (192) of the ring (158). Assembly (150) according to one of claims 1 to 4, in which said shim (154') is formed by a split ring. An assembly (150) according to claim 5, when dependent on claim 3 or 4, wherein said wedge (154) is axially interposed between the rib (192) of the ring (158) and the flange (186) of the nut (152). Assembly (150) according to claim 1 or 2, wherein said shim (154) is mounted on the ring (158) by a bayonet system. Assembly (150) according to claim 7, in which said shim (154) comprises a first axial and/or radially internal end mounted on the ring (158) by the bayonet system, and a second axial and/or radially external end which comprises an outer annular flange (182) on which the flange (186) of the nut (152) bears axially. An assembly (150) according to claim 8, wherein said shim (154) comprises a cylindrical wall (180) extending between said first and second ends and having an outer diameter (Dpe) less than said inner diameter of the nut (152 ). Assembly (150) according to one of the preceding claims, in which said nut (152) comprises recesses (184) and/or protrusions (190) configured to allow engagement of a driving tool . Assembly (150) according to one of the preceding claims, in which the said part (156) comprises a body (86) extending around the Y axis), an annular wall (91) carrying an external toothing (82) and extending around the body (86), and an annular veil (88) extending radially between the body (86) and the annular wall (91), the wall (91) defining around the body (86) an annular space (R1, R2) housing at least a portion of said bearing (94), and the nut (152) which is located axially between the veil (88) and this bearing (94). Assembly (150) according to one of the preceding claims, in which said part (156) is a satellite (80) of a mechanical reduction gear. Mechanical reduction gear (6) for an aircraft turbomachine (1), comprising at least one assembly (150) according to one of the preceding claims. Method for assembling an assembly (150) according to one of Claims 1 to 12, characterized in that it comprises the steps of:
- assembly of the nut (152) and the wedge (154, 154') on the ring (158) of the bearing (94),
- hooping of the ring (158) of the bearing (94) on the cylindrical surface (166) of the part (156), until the axial bearing of the ring (158) on the shoulder (168) of the part (156),
- screwing the nut (152) on the thread (170) of the part (156) so as to axially block the ring (158) on the part (156). A method according to claim 14, wherein the shim (154, 154') is mounted on the ring (158) after mounting or simultaneously with the mounting of the nut (152) on the ring (158).