FR3122713A1 - Rolling bearing comprising an oil film compression damper with fluid disturbance recesses - Google Patents

Abstract

A rolling bearing (20) includes a radial oil film damping cavity (60) bounded by a surface (50) including oil flow disturbance recesses (70) which follow each other circumferentially. Figure for abstract: Fig. 4

Description

Rolling bearing comprising an oil film compression damper with fluid disturbance recesses

The invention relates to the field of rolling bearings for turbomachines or other rotating machines, in particular for an aircraft propulsion system.

State of the prior art

A conventional aircraft turbine engine comprises at least one shaft and a device for guiding this shaft in rotation comprising at least one rolling bearing mounted on suspension and equipped with an oil film compression damper, known as Anglo-Saxon “squeeze-film damper”. Such a damper makes it possible to dampen the vibrations and displacements of the shaft caused by its rotation and by the imbalance of its mechanical loading.

Document EP 1 650 449 A1 describes such a guiding device.

The effectiveness of oil film compression dampers known in the state of the prior art generally depends on the axial dimension of the cavity receiving the fluid and forming the film so that the increase in damping performance can require an elongation of this cavity, which is not always possible given the available space.

In addition, the generally cylindrical geometry of conventional damping cavities does not make it possible to ensure selective damping along privileged directions when the rotor is for example subjected to non-axisymmetric cyclic forces.

There is therefore a need to provide a damper adapted to such conditions and making it possible to improve its efficiency without lengthening the cavity.

To this end, the subject of the invention is a bearing for guiding a rotating machine shaft in rotation about an axis, comprising a first annular part, a second annular part and sealing members, the first part forming a ring of the bearing or being intended to be secured to a bearing race of the bearing, the second part being intended to be connected to a casing of the rotating machine, the first part and the second part defining radially between them a cavity configured to receive a flow of a pressurized fluid so as to form a circumferential film of the fluid capable of radially damping a relative displacement of the first part with respect to the second part, the cavity being delimited radially by a damping surface of each of the first and second parts and axially by the sealing members. According to the invention, the damping surface of the first part and/or of the second part comprises recesses for disturbing the flow of fluid which follow one another circumferentially.

The invention thus makes it possible to modify the geometry of the film of fluid as well as the flow of this fluid in the cavity.

This results on the one hand in the possibility of improving the damping for an identical size of the bearing compared to a conventional bearing or of maintaining the same damping efficiency by reducing its size, and/or the possibility of using a less viscous fluid.

On the other hand, each recess makes it possible to locally modify the pressure of the fluid and the dissipation of energy in the fluid, which makes it possible to define preferred damping orientations, by inducing for example a drop in damping in a given angular direction. The invention thus makes it possible to limit the impact on the movement of the rotor of non-axisymmetric forces.

The cavity is preferably annular, for example cylindrical or conical.

The fluid is preferably oil.

In one embodiment, at least one of the recesses extends axially for at least fifty percent of an axial length of the cavity.

Preferably, each recess extends over a circumferential portion less than 90°.

In one embodiment, at least one of the recesses forms a groove.

In one embodiment, at least one of the recesses extends axially and circumferentially.

In one embodiment, the recesses form one or more chevrons.

In another embodiment, the recesses form an intersecting mesh whose profiles, angles and distances can vary circumferentially.

The invention also relates to a rotating machine comprising a shaft and such a bearing for guiding the shaft in rotation about an axis.

In one embodiment, the subject of the invention is a turbomachine formed by such a rotating machine.

The invention also relates to a propulsion assembly for an aircraft, comprising such a turbomachine.

According to another aspect, the subject of the invention is a method of manufacturing a bearing as defined above.

In one embodiment, the method includes a step of machining the recesses.

Other advantages and characteristics of the invention will appear on reading the detailed, non-limiting description which follows.

The following detailed description refers to the attached drawings in which:

is a schematic view in longitudinal half-section of a turbojet engine according to the invention;

is a schematic view in longitudinal section of a bearing according to the invention;

is a schematic perspective view of a part forming a bearing race and a flexible cage of the bearing of FIG. 2;

is a view in longitudinal section of a part of the bearing of FIG. 2, along a section plane passing through a recess formed by a ring according to a first embodiment of the invention;

is a schematic perspective view of the hoop ring of FIG. 4;

is a schematic perspective view of a bearing ring according to a second embodiment of the invention;

is a schematic perspective view of a bearing ring according to a third embodiment of the invention.

Detailed description of embodiments

There is shown in Figure 1 a turbofan engine 1 and double body.

Subsequently, the terms "upstream" and "downstream" are considered according to a direction S1 of main gas flow through the turbojet engine 1.

The turbojet engine 1 conventionally comprises a gas generator 2 forming, from upstream to downstream, a low-pressure compressor 3, a high-pressure compressor 4, a combustion chamber 5, a high-pressure turbine 6 and a low-pressure turbine pressure 7.

The low pressure compressor 3 and the low pressure turbine 7 form a low pressure body and are connected to each other by a low pressure shaft 8 centered on a central longitudinal axis A1 of the turbojet engine 1. Similarly, the high pressure compressor 4 and the high pressure turbine 6 form a high pressure body and are connected to each other by a high pressure shaft 9 centered on the axis A1 and arranged around the low pressure shaft 8.

The turbojet 1 also comprises, upstream of the gas generator 2, a fan 10 which is here arranged directly behind an air inlet cone of the engine. The fan 10 is rotatable along the axis A1 and is surrounded by a fan casing 11. It is driven indirectly by the low pressure shaft 8, via a speed reducer 12.

In addition, conventionally, the turbojet engine 1 defines a primary stream 16 intended to be traversed by a primary flow, as well as a secondary stream 18 intended to be traversed by a secondary flow located radially outwards with respect to the primary flow. .

The two shafts 8 and 9 as well as the hub of the fan 10 are guided in rotation by means of bearings 20 supported by casings of the turbojet engine 1. At least one of these bearings 20 conforms to one of the modes implementation described below.

Figure 2 shows a bearing 20 according to the invention.

In this example, the bearing 20 is intended to provide guidance in rotation around the axis A1 of the high pressure shaft 9. Of course, this bearing 20 can be implemented in a similar manner in the turbojet engine 1 of FIG. 1 in order to guide the low pressure shaft 8 or within another type of rotating machine.

The bearing 20 comprises on the one hand a rolling member formed by an inner rolling ring 21, an outer rolling ring 22 and rolling elements 23 extending radially between the rings 21 and 22.

In a manner known per se, each of the rings 21 and 22 forms a rolling track of the rolling elements 23, the latter being circumferentially spaced around the axis A1 by means of a separator cage (not shown).

The rolling elements 23 are rollers here.

Alternatively, the rolling elements 23 can be balls arranged to form a ball bearing with two, three or four points of contact.

Each of the rings 21 and 22 is annular and made in this example in one piece. Alternatively, the rings 21 and/or 22 can each be formed by two half-rings.

The inner ring 21 is integral with the shaft 9.

The outer ring 22 is intended to be connected to one of said casings of the turbojet engine 1, via a support 24.

In the example of Figure 2, the support 24 comprises axial part 25 and a radial flange 26.

A shrunken ring 27 is tightly mounted in the axial part 25 of the support 24 so as to extend radially between this axial part 25 and the outer ring 22 of the bearing.

The bearing 20 further comprises a flexible cage 30 defining circumferentially spaced axial openings around the axis A1.

In this example, the cage 30 extends the outer ring 22 downstream and is made in one piece with this outer ring 22 (see Figure 3). In an embodiment not shown, the outer ring 22 and the cage 30 can form two separate parts assembled with each other.

The cage 30 comprises a downstream end 31 secured to a support 32 also connected to the aforementioned casing.

In this example, the support 32 comprises an upstream radial flange 33 fixed to the radial flange 26 of the support 24, a downstream radial flange 34 to which the cage 30 is fixed by its downstream end 31 and a tapered part 35 connecting the flanges 33 and 34 to each other.

The cage 30 is elastically deformable so as to allow a slight displacement in translation of the outer ring 22, in a plane orthogonal to the axis A1. The cage 30 thus performs a suspension function.

Referring to Figure 3, the outer ring 22 defines an outer surface 40 and includes three grooves 41, 42 and 43 formed on this outer surface 40.

The grooves 41 and 43 are made at the upstream and downstream ends, respectively, of the ring 22, while the functionally optional groove 42 extends axially between the grooves 41 and 43, in this example equidistant from those -this. In variants not shown, the groove 42 can be located close to one of the grooves 41 and 43.

Each of the grooves 41, 42 and 43 forms an annular straight groove extending over the entire circumference of the ring 22, that is to say 360°.

Referring to Figures 3 and 4, the bearing 20 comprises two sealing members 44 and 45 forming annular segments housed respectively in the grooves 41 and 43.

The organs 44 and 45 establish a sealed connection with the shrink ring 27.

Shrink-fit ring 27 forms an inner surface 50, facing outer surface 40 of ring 22, so as to define, radially between these surfaces 40 and 50, an annular cavity 60.

The cavity 60 is thus delimited radially by the surfaces 40 and 50 and axially by the sealing members 44 and 45.

The cavity 60 is intended to receive a flow of a fluid such as pressurized oil so as to form a circumferential film of oil capable of radially damping a relative displacement in translation of the outer race 22 of the bearing with respect to the shrunken ring 27 and therefore relative to the casing of the turbojet engine 1.

The bearing 20 thus makes it possible to ensure both a suspension function by the flexible cage 30 and a radial damping function by the film of oil, known by the English name “squeeze-film”.

This radial damper makes it possible to dissipate part of the energy resulting from the orthogonal displacements authorized by the flexible cage 30 and to transmit the corresponding forces to the casing.

In this example, the surfaces 40 and 50, also called damping surfaces, are substantially cylindrical so that the cavity 60 is generally cylindrical.

In an embodiment not shown, the cavity 60 and/or at least one of the damping surfaces 40 and 50 can be conical.

In order to introduce oil into the cavity 60, the shrink ring 27 comprises one or more orifices 62 fluidically connecting the cavity 60 to a supply channel 64 formed by the support 24.

The orifices 62 open into the cavity 60 axially facing the groove 42 of the outer ring 22 of the bearing 20, this groove 42 thus making it possible to improve the circumferential distribution of the oil within the cavity 60.

Figure 5 shows the shrink ring 27 of the bearing 20 of Figure 4.

In this example, the damping surface 50 formed by the ring 27 comprises recesses 70, also called hollows or indentations, which form ridges on the surface 50 capable of disturbing the flow of oil in the cavity 60.

Referring to Figures 4 and 5, each recess 70 forms in this embodiment a straight groove which extends axially over a distance X1 of more than fifty percent of the axial length X2 of the cavity 60.

Each recess 70 is in particular perpendicular to the groove 42 formed by the ring 22.

In this example, the recesses 70 all have an identical width or circumferential dimension X3 of the order of a few degrees. It is preferred that this width X3 be less than 10°.

The recesses 70 follow each other circumferentially, defining two by two between them a circumferential distance X4.

In the example of Figure 5, part of the recesses 70, in particular those shown towards the top of this figure, are grouped together in an angular portion of the ring 27 which is less than 90°.

The recesses 70 thus make it possible to locally disturb the flow of oil in the cavity 60, so as to define one or more preferred damping directions.

FIG. 6 illustrates an embodiment which differs from that of FIG. 5 in that the recesses 70 do not all have the same width X3.

In particular, some recesses 70A have a width close to twice the width of other recesses 70B.

In this example, the recesses 70B extend over an angular portion of the ring 27 which is between 00° and 50° and forms a series circumferentially delimited on either side by a respective one of the recesses 70A.

Such an organization of the recesses 70A and 70B makes it possible to hinder the flow of oil in the cavity 60 at the level of this angular portion and to selectively increase the damping in a direction passing through this angular portion.

FIG. 7 illustrates another embodiment in which the recesses form chevrons 80, that is to say V-shaped recesses, which follow one another circumferentially.

In this example, each chevron 80 is formed by a first straight groove 70C extending both axially and circumferentially in a first direction and by a second straight groove 70D extending both axially and circumferentially in a second oblique direction by relative to the first direction.

The first groove 70C and the second groove 70D of each chevron 80 have in this example an identical dimension so as to present a symmetry with respect to a plane orthogonal to the axis A1 passing through the orifices 62 of the ring 27.

The chevrons 80 are in this example grouped together on an angular portion of the ring 27 comprised between 70° and 100°.

By making each of the chevrons 80 so that the point they form is oriented in a direction opposite to the flow of oil in the cavity 60, it is possible to promote this flow at this angular portion and to selectively reduce damping in a direction passing through this angular portion.

The invention is in no way limited to the embodiments described above and the recesses may have a geometry and an arrangement different from those of FIGS. 5 to 7. For example, the invention covers a ring having both recesses in the form of straight grooves as shown in Figures 4 to 6 and recesses forming chevrons such as those shown in Figure 7. In addition, the recesses may have non-straight parts and / or form for example zigzags.

More generally, such recesses can be made on another bearing part, for example on the ring 22 of the bearing 20 of FIG. 2 or even on a part of a different bearing.

Claims (9)

Bearing (20) for guiding a shaft (8, 9) of a rotating machine (1) in rotation around an axis (A1), comprising a first annular part (22), a second annular part (27) and seal (44, 45), the first part (22) forming a bearing race (20) or being intended to be secured to a bearing race (20), the second part (27) being intended to be connected to a casing of the rotating machine (1), the first part (22) and the second part (27) defining radially between them a cavity (60) configured to receive a flow of a pressurized fluid so as to form a circumferential film of the fluid capable of radially damping a relative displacement of the first part (22) with respect to the second part (27), the cavity (60) being delimited radially by a damping surface (40, 50) of each of the first and second parts (22, 27) and axially by the sealing members (44, 45), characterized in that e the damping surface (40, 50) of the first part (22) and/or of the second part (27) comprises recesses (70, 70A-70D) for disturbing the flow of fluid which follow one another circumferentially . A bearing (20) according to claim 1, wherein at least one of the recesses (70, 70A-70D) extends axially for at least fifty percent of an axial length (X2) of the cavity (60). A bearing (20) according to claim 1 or 2, wherein at least one of the recesses (70, 70A-70D) forms a groove. A bearing (20) according to any of claims 1 to 3, wherein at least one of the recesses (70C, 70D) extends axially and circumferentially. A bearing (20) according to any of claims 1 to 4, wherein the recesses (70C, 70D) form one or more chevrons (80). Rotating machine (1) comprising a shaft (8, 9) and a bearing (20) according to any one of claims 1 to 5 for guiding the shaft (8, 9) in rotation about an axis (A1) . Turbomachine (1) formed by a rotating machine according to claim 6. Propulsion assembly for aircraft, comprising a turbine engine (1) according to claim 7. Method of manufacturing a bearing (20) according to any one of claims 1 to 5, comprising a step of machining the recesses (70, 70A-70D).