Device for centering and guiding the rotation of a turbomachine shaft with liquid film compression damper and secondary damper

Abstract

A device (30) with a rolling bearing (32) provided with a liquid film compression damper comprises a secondary damper, comprising friction means (76) movable between: a rest position, towards which the friction means are urged by the pressure of the liquid (L), and in which the friction means are spaced from a friction structure (88) configured to move radially according to possible radial movements of an outer ring (38) of the bearing; and a service position, in which the friction means are applied against the friction structure by elastic return means (84), so as to cause a dissipation of mechanical energy by friction under the effect of the possible radial movement of the friction structure. Figure for abstract: Figure 2A

Description

Title of the invention: Device for centering and guiding the rotation of a turbomachine shaft with liquid film compression damper and secondary damper Technical field

[0001] The present invention relates to the field of turbomachines, in particular for aircraft, and more particularly concerns a device for centering and guiding in rotation a turbomachine rotor shaft, comprising a bearing damped by compression of a liquid film, generally of oil, also called an "SFD" bearing (from the English "Squeeze Film Damper"). State of the prior art

[0002] A device for centering and guiding in rotation a turbomachine rotor shaft of the SFD bearing type is a known means for enabling the damping of vibrations of the shaft, as explained for example in the document EP1650449B1 of the applicant.

[0003] With reference to the attached [Fig. 1A], which shows such a device schematically, the reference 210 designates a rotor shaft of a turbomachine intended for the propulsion of an aircraft, such as an aircraft turbojet or turboprop. This rotor shaft 210 is centered and guided in rotation in a rolling bearing 212. The latter comprises an outer ring 214 carried by an elastically deformable structure 216, commonly called a “squirrel cage” or “flexible cage”, itself carried by a stator structure of the turbomachine.The elastically deformable structure 216 comprises, between one end connected to the outer ring 214 and an opposite end connected to the stator structure, an annular row of openings 216A separated two by two by columns 216B, making it possible to give flexibility in bending to the structure, so as to offer a certain degree of radial movement, or orbiting, to the outer ring 214, under the effect of vibrations of the shaft, for example following an unbalance.

[0004] The outer ring 214 is mounted in a cylindrical housing 218 defined by a bearing support 220 to form around the outer ring 214 an oil film compression damper (SFD). For this purpose, an annular damping cavity 222 is delimited around the outer ring 214 by the cylindrical surface 221 of the bearing support 220 defining the housing 218, and is axially closed by annular seals 224 mounted in annular grooves 226 formed in the outer cylindrical surface of the ring 214.

[0005] The annular cavity 222 is filled with a liquid, typically a lubricant such as the oil, brought through one or more inlet orifice(s) 228 formed by a radial bore in the bearing support 220 and opening into an annular groove 230 formed in the cylindrical surface 221 and opening into the annular cavity 222.

[0006] Thus, any orbiting of the outer ring would lead to a crushing of the liquid film defined within the aforementioned cavity, such crushing being the cause of damping.

[0007] Such a damping capacity makes it possible to reduce the design loads, and therefore to lighten the structures, resulting in an overall reduction in mass.

[0008] However, in the event of an interruption in the supply of liquid to the aforementioned cavity, orbiting of the outer ring of the bearing risks damaging the elements constituting the bearing and its support, or even causing vibrations likely to damage the entire turbomachine. Statement of the invention

[0009] The invention aims to at least partially remedy the above problem.

[0010] To this end, it proposes a device for centering and guiding the rotation of a turbomachine shaft, comprising: a rolling bearing comprising an inner ring, an outer ring defining an axis of the rolling bearing, and an annular row of rolling elements interposed between the inner ring and the outer ring; a bearing support surrounding the outer ring; an annular damping cavity, formed between the bearing support and the outer ring; a supply pipe opening into the annular damping cavity to supply the latter with liquid and thus form a damper there by compressing the liquid film;

[0011] in which the outer ring is carried by an elastically deformable structure rigidly secured to the bearing support;

[0012] characterized in that it comprises a secondary damper, comprising friction means movable between: a rest position, towards which the friction means are urged by the pressure of the liquid, and in which the friction means are spaced from a friction structure configured to move radially according to any radial movements of the outer ring; and a service position, in which the friction means are applied against the friction structure by elastic return means, so as to cause dissipation of mechanical energy by friction under the effect of any radial displacement of the friction structure.

[0013] Thus, the friction means remain inoperative during normal operation, since the pressure of the liquid supplying the annular damping cavity allows the friction means to be maintained in the rest position. In the event of a fault in the liquid supply, the elastic return means bring the friction means into their service position in contact with the friction structure, so that any radial displacement of the friction structure, and therefore any radial displacement of the outer ring reflecting, for example, an orbiting phenomenon of the latter, is accompanied by a dissipation of mechanical energy by friction between the friction means and the friction structure.

[0014] Implementing such a dissipation of mechanical energy by friction only in the event of failure of the shock absorber by compression of the liquid film also makes it possible to avoid polluting the liquid, typically oil, with residues originating from the wear of the friction means or the friction structure. The presence of such residues would have the particular disadvantage of fouling, if necessary, filters provided for filtering the oil before its evacuation. The invention thus makes it possible to avoid such fouling.

[0015] In preferred embodiments of the invention, the friction structure is a friction ring extending transversely projecting from the elastically deformable structure. In other preferred embodiments of the invention, the friction structure forms a free end of the outer ring.

[0016] In preferred embodiments of the invention, the secondary damper comprises a housing, a piston and a pad.

[0017] In preferred embodiments of the invention, the piston is arranged within the enclosure to delimit an inhibition chamber in fluid communication with the annular damping cavity.

[0018] In preferred embodiments of the invention, the pad, which forms said friction means, is rigidly connected to the piston and arranged outside the enclosure so as to be movable between the rest position and the service position by means of sliding of the piston within the enclosure in a sliding direction having a component along the axis of the rolling bearing.

[0019] In preferred embodiments of the invention, the enclosure, the piston and the pad are each annular in shape and each extend around the axis of the rolling bearing.

[0020] In preferred embodiments of the invention, the elastic return means comprise an elastic washer extending around the axis of the rolling bearing and housed in an activation chamber delimited by the piston within the enclosure, on a side opposite the inhibition chamber, so as to urge the piston towards the inhibition chamber.

[0021] In preferred embodiments of the invention, the secondary damper comprises a plurality of secondary damping devices distributed around the axis of the rolling bearing.

[0022] In preferred embodiments of the invention, each of the secondary damping devices comprises an enclosure, a piston arranged within the enclosure to delimit therein an inhibition chamber in fluid communication with the annular damping cavity, and a pad rigidly connected to the piston and arranged outside the enclosure, so that the set of respective pads of the secondary damping devices, which constitutes said friction means, is movable between the rest position and the service position by means of sliding of the pistons respectively within the enclosures each in a respective sliding direction having a component along the axis of the rolling bearing.

[0023] In preferred embodiments of the invention, the elastic return means comprise, for the secondary damping device or for each secondary damping device, an elastic member housed in an activation chamber delimited by the piston within the enclosure of the damping device in question, on a side opposite the inhibition chamber thereof, so as to urge the piston in the direction of the inhibition chamber.

[0024] In preferred embodiments of the invention, said sliding direction is parallel to the axis of the rolling bearing.

[0025] In preferred embodiments of the invention, the friction structure is an integral part of a body forming the outer ring or the elastically deformable structure. In other preferred embodiments of the invention, the friction structure is a wear part fixed to a body forming the outer ring or the elastically deformable structure.

[0026] The invention also relates to a turbomachine comprising at least one device of the type defined above. Brief description of the drawings

[0027] The invention will be better understood, and other details, advantages and characteristics thereof will appear on reading the following description given by way of non-limiting example and with reference to the appended drawings in which:

[0028] [Fig. 1 A], already described, is a schematic view in axial section and in perspective of a device for centering and guiding the rotation of a shaft in a turbomachine, of known type;

[0029] [Fig.lB] is a schematic axial sectional view of a turbomachine for aircraft;

[0030] [Fig.2A] is a schematic axial sectional view of a device for centering and the rotational guidance of a shaft in a turbomachine such as that of [Fig.lB], according to a preferred embodiment of the invention, illustrating friction means in a rest position;

[0031] [Fig.2B] is a view similar to [Fig.2A], illustrating the friction means in a service position;

[0032] [Fig.3] is a view similar to [Fig.2A], illustrating a variant of the device;

[0033] [Fig.4] is a view similar to [Fig.2A], illustrating another variant of the device ;

[0034] [Fig.5] is a view similar to [Fig.2A], illustrating another variant of the device.

[0035] Throughout the following description and the accompanying drawings, identical reference numerals may designate similar or analogous elements. Detailed description of preferred embodiments

[0036] [Fig. 1B] illustrates a turbomachine 10, for example a twin-spool, dual-flow turbojet for aircraft, generally comprising a fan 12 intended for the suction of an air flow F1 dividing downstream of the fan into a primary flow F2 circulating in a primary flow channel, hereinafter referred to as the primary vein PV, and a secondary flow F3 circulating in a secondary flow channel, hereinafter referred to as the secondary vein SV, arranged around the primary vein PV.

[0037] By way of illustration, the turbomachine generally comprises a low-pressure compressor 14, a high-pressure compressor 16, a combustion chamber 18, a high-pressure turbine 20 and a low-pressure turbine 22 which jointly define the primary flow path PV. The respective rotors of the high-pressure compressor and the high-pressure turbine are connected by a shaft 24 called the “high-pressure shaft”, while the respective rotors of the low-pressure compressor and the low-pressure turbine are connected by a shaft 26 called the “low-pressure shaft”, in a well-known manner. These rotors are rotatably mounted about an axis 28 of the turbomachine. For this purpose, devices 30A, 30B ensure the centering and rotational guidance of the high-pressure shaft 24, while devices 30C-30E ensure the centering and rotational guidance of the low-pressure shaft 26.These devices 30A-30E, which each comprise a rolling bearing, establish force paths between the shafts 24, 26, on the one hand, and the casings of the turbomachine, on the other hand, in a well-known manner.

[0038] Throughout this description, the axial direction X is the direction of the axis 28. We further consider a cylindrical coordinate system centered on the axis 28, in which a radial direction R is at all points orthogonal to the axis 28 and passes through the latter, while an orthoradial or circumferential direction C is at all points orthogonal to the radial direction R and to the axis 28. A transverse plane is a plane orthogonal to the axis 28. The terms "internal" and "external" respectively refer to at a relative proximity, and a relative distance, of an element with respect to the axis 28. Finally, the “upstream” and “downstream” directions are defined by reference to the general direction FD of the flow of gases in the primary PV and secondary SV veins of the turbomachine, according to the axial direction X.

[0039] The invention is, generally speaking, applicable to any type of turbomachine, whether single-flow or multi-flow, single-body or multi-body.

[0040] The invention relates more specifically to a device for centering and guiding the rotation of a shaft within such a turbomachine, of the SFD bearing type as described above with reference to [Fig. 1A], and optimized to limit the risks of damage in the event of a fault in the supply of the damping liquid film.

[0041] [Fig.2A] illustrates such a device 30, which corresponds for example to any one of the devices 30A-30E of [Fig.1B]. The latter comprises in particular a rolling bearing 32 and a bearing support 34.

[0042] The rolling bearing 32 comprises an inner ring 36, an outer ring 38, and an annular row of rolling elements 40 interposed between an outer annular surface 42 of the inner ring 36 and an inner annular surface 44 of the outer ring 38. The rolling elements 40 are typically associated with an annular cage, in a well-known manner.

[0043] The outer ring 38 is carried by an elastically deformable structure 45 or “squirrel cage”, such as the structure 216 of [Fig. 1A], comprising an annular row of openings 45A separated two by two by columns 45B, for example similar to the openings 216A and columns 216B of [Fig. 1A]. Conventionally, the elastically deformable structure 45 comprises, at one of its ends, a flange 45C by which it is fixed to a corresponding flange 34A of the bearing support 34, and the elastically deformable structure 45 is, at its opposite end, rigidly connected to - or fully extended by - the outer ring 38.

[0044] The internal annular surface 44 of the outer ring 38 has a shape of revolution along an axis defined as axis 46 of the bearing 32 and coinciding for example with the axis 28 of the turbomachine.

[0045] Furthermore, the outer ring 38 has an outer annular surface 48. In addition, the bearing support 34 has an inner annular surface 50 surrounding the outer annular surface 48 of the outer ring 38. The two surfaces 48 and 50 are centered along the axis 46 of the bearing.

[0046] An annular cavity called a damping cavity 52 is formed between the internal annular surface 50 of the bearing support 34 and the external annular surface 48 of the outer ring 38 and is defined axially between two annular sealing joints 54A, 54B mounted in corresponding annular grooves formed in the outer surface 48 of the outer ring 38. The annular damping cavity 52 is intended to receive liquid L, typically a lubricating liquid such as oil, to form a damping film and thus define a liquid film compression damper or “SFD”.

[0047] Furthermore, the device 30 comprises a supply pipe 60 opening, through the internal annular surface 50 of the bearing support 34, into the annular damping cavity 52, to supply the latter with liquid L intended to form the aforementioned damping film. By "pipe", it is generally understood, in the present description, any channel or network of channels adapted to the circulation of the liquid. The liquid can come from any circuit or any source available for this purpose in the turbomachine.

[0048] Furthermore, to allow continuous circulation of the liquid L and thus limit its heating despite the high temperatures that may prevail in the region of a bearing, in particular in cases where such a bearing is located at the level of a turbine of the turbomachine, an evacuation path is defined from the annular damping cavity 52 so as to allow the liquid L to escape from the latter. Such an evacuation path is generally made up of leakage sections provided between the annular sealing joints 54A, 54B and the external annular surface 48 of the outer ring 38. Other evacuation methods are of course possible as a variant within the framework of the present disclosure.

[0049] The invention generally provides for equipping the device 30 with a secondary damper to dissipate mechanical energy corresponding to radial movements of the outer ring 38, reflecting for example a phenomenon of orbiting of the outer ring 38 due to a failure of the liquid film compression damper, typically in the event of a failure in the supply of the damping cavity 52 with liquid L.

[0050] Thus, the device 30 visible in [Fig.2A] comprises a secondary damping device 70 which comprises an enclosure 72, a piston 74 and a pad 76.

[0051] The enclosure 72 is for example in the shape of a rectangular parallelepiped or a cylinder.

[0052] The piston 74 is adapted to slide in a sealed or substantially sealed manner within the enclosure 72, in a direction having a component along the axis 46, preferably a direction parallel to the axis 46.

[0053] The piston 74 divides the enclosure 72 into a chamber 78, hereinafter referred to as the inhibition chamber, and a chamber 80, hereinafter referred to as the activation chamber. The inhibition chamber 78 is in fluid communication with the annular damping cavity 52, for example via a conduit 82 connected to the supply pipe 60. The activation chamber 80 houses elastic means return, in this case an elastic member such as a compression spring 84. This spring 84 or these elastic return means urge the piston 74 towards the inhibition chamber 78.

[0054] The pad 76 is arranged outside the enclosure 72 while being rigidly connected to the piston 74, for example by a rod 86 passing in a sealed or substantially sealed manner through an end wall of the enclosure 72. The pad 76 comprises for example a body 76A formed in one piece with the rod 86 and the piston 74, or fixed to the rod 86, and a friction lining 76B covering the body 76A on the side opposite the rod 86.

[0055] The pad 76 is an example of “friction means”, according to the terminology used in the general definition of the invention, as will become more clear in the following.

[0056] A friction ring 88, which projects radially outward from an external surface of the elastically deformable structure 45, is arranged axially opposite the pad 76, in this case opposite the friction lining 76B, so that the stress of the piston 74 in the direction of the inhibition chamber 78 corresponds to a stress of the pad 76 in the direction of the friction ring 88.

[0057] The friction ring 88 is positioned in a region of the structure 45 capable of moving radially according to deformations of this structure induced by a possible orbiting of the outer ring 38 in the event of a malfunction of the damper by compression of the liquid film defined by the annular damping cavity 52. ​​For this purpose, the friction ring 88 is positioned at a distance from the flange 45C in the direction of the outer ring 38 of the bearing, for example around the openings 45A and columns 45B.

[0058] The friction ring 88 is an example of a “friction structure” configured to move radially in response to possible radial movements of the outer ring 38 and to cooperate with the pad 76, or more generally with the friction means, so as to cause a dissipation of mechanical energy by friction under the effect of its possible radial movement, as will appear more clearly in the following.

[0059] The friction ring 88, or more generally the friction structure, may be an integral part of a body forming the elastically deformable structure 45, or be a wear part attached to such a body.

[0060] In operation, liquid L ([Fig.2A]) enters the annular damping cavity 52 from the supply pipe 60 and forms a damping film within the cavity 52. ​​The liquid preferably circulates continuously as explained above. Liquid L is further supplied to the inhibition chamber 78 via the conduit 82. The compression spring 84 has a stiffness chosen so that the pressure of the liquid L within the inhibition chamber 78, in normal operation, allows the force exerted by the spring 84 on the piston 74 to be counterbalanced, and thus allows the pad 76 to be maintained in a rest position, at a distance from the friction ring 88, as illustrated in [Fig.2A].

[0061] If the supply of liquid L is interrupted ([Fig.2B]), the damping by the liquid film within the cavity 52 no longer operates, which generates a risk of orbiting of the outer ring 38.

[0062] Furthermore, the force induced by the pressure of the liquid L ceases to be applied to the piston 74, so that the latter slides towards the inhibition chamber 78, thus reducing the volume of the latter, under the effect of the stiffness of the spring 84, until the shoe 76 reaches a service position in which the shoe 76 is applied against the friction ring 88.

[0063] Therefore, any possible orbiting phenomenon of the outer ring 38 of the bearing, accompanied by a radial displacement of the friction ring 88, causes friction between the latter and the pad 76, causing a dissipation of mechanical energy, and thus making it possible to attenuate the orbiting phenomenon.

[0064] The secondary damper of the device 30 of Figures 2A-2B comprises the secondary damping device 70 described above, or, preferably, a plurality of such devices distributed around the axis 46 of the bearing. In preferred embodiments, the secondary damper of the device 30 of Figures 2A-2B comprises at least two secondary damping devices 70 oriented at 90 degrees to each other so as to act in two radial directions orthogonal to each other.

[0065] As a variant, the secondary damper of the device 30 visible in [Fig. 3] comprises a single secondary damping device 70 whose enclosure 72, piston 74 and pad 76 are each annular in shape and each extend around the axis 46 of the bearing. The inhibition 78 and activation 80 chambers are therefore also annular in shape.

[0066] In such a case, the elastic return means comprise for example an elastic member such as an elastic washer 90, housed in the activation chamber 80 so as to urge the piston 74 towards the inhibition chamber 78, in a manner analogous to that described above.

[0067] [Fig. 4] illustrates another variant, in which the friction ring 88, or more generally the friction structure, forms a free end of the outer ring 38. Here again, the friction structure can be an integral part of a body forming the outer ring 38, or be a wear part attached to such a body.

[0068] The configuration of the secondary damping device 70 is here axially reversed with respect to that visible in FIGS. 2A to 3, so that the elastic return means, in this case the spring 84, here again urge the piston 74 in the direction of the friction ring 88.

[0069] [Fig. 5] illustrates another variant, in which the secondary damping device 70 differs from that of [Fig. 2A] in that the pad 76 comprises a rim 92 projecting in the direction from the pad 76 towards the friction ring 88, so that in the service position, the rim 92 is interposed between an edge 88A of the friction ring 88 and the bearing support 34. For this purpose, the bearing support 34 advantageously comprises a prominent seat 94 of a shape complementary to that of the rim 92. Furthermore, in the example illustrated, the rim 92 is formed jointly by a rim of the body 76A and by a rim of the friction lining 76B covering the rim of the body 76A.

[0070] The rim 92 makes it possible to form a stop opposing excessive radial displacement of the outer ring 38, while contributing to the dissipation of mechanical energy in the event of vibrations of the ring 38 in the circumferential direction resulting in friction between the edge 88A of the friction ring 88 and the rim 92 of the pad 76.

[0071] Figures 2A to 5 thus show different examples in which the secondary damper, formed by the damping device 70 or a plurality of such devices, and the friction structure, in this case the friction ring 88, are configured so that in the service position, the possible radial displacement of the friction structure causes friction between the friction structure and the friction means, which friction causes a dissipation of mechanical energy making it possible to attenuate the displacements of the outer ring 38.

Claims

Claims

1. Device (30) for centering and guiding in rotation a turbomachine shaft, comprising: • a rolling bearing (32) comprising an inner ring (36), an outer ring (38) defining an axis (46) of the rolling bearing, and an annular row of rolling elements (40) interposed between the inner ring (36) and the outer ring (38); • a bearing support (34) surrounding the outer ring (38); • an annular damping cavity (52), formed between the bearing support (34) and the outer ring (38); • a supply pipe (60) opening into the annular damping cavity (52) to supply the latter with liquid (L) and thus form a damper there by compression of the liquid film; in which the outer ring (38) is carried by an elastically deformable structure (45) rigidly secured to the bearing support (34); characterized in that it comprises a secondary damper, comprising friction means (76) movable between: • a rest position, towards which the friction means are urged by the pressure of the liquid (L), and in which the friction means are spaced from a friction structure (88) configured to move radially according to any radial movements of the outer ring (38); and • a service position, in which the friction means are applied against the friction structure by elastic return means (84; 90), so as to cause dissipation of mechanical energy by friction under the effect of any radial displacement of the friction structure.

2. A device according to claim 1, wherein the friction structure (88) is a friction ring extending transversely projecting from the elastically deformable structure (45), or wherein the friction structure (88) forms a free end of the outer ring (38).

3. Device according to claim 1 or 2, wherein the secondary damper comprises an enclosure (72), a piston (74) and a pad (76), wherein the piston (74) is arranged within the enclosure (72) to delimit therein an inhibition chamber (78) in fluid communication with the annular damping cavity (52), and wherein the pad (76), which forms said friction means, is rigidly connected to the piston (74) and arranged outside the enclosure (72) so as to be movable between the rest position and the service position by means of sliding of the piston (74) within the enclosure (72) in a sliding direction having a component along the axis (46) of the rolling bearing.

4. A device according to claim 3, wherein the enclosure (72), the piston (74) and the pad (76) are each annular in shape and each extend around the axis (46) of the rolling bearing.

5. Device according to claim 4, in which the elastic return means (90) comprise an elastic washer extending around the axis (46) of the rolling bearing and housed in an activation chamber (80) delimited by the piston (74) within the enclosure (72), on a side opposite the inhibition chamber (78), so as to urge the piston (74) towards the inhibition chamber (78).

6. Device according to claim 1 or 2, in which the secondary damper comprises a plurality of secondary damping devices (70) distributed around the axis (46) of the rolling bearing and each comprising an enclosure (72), a piston (74) arranged within the enclosure (72) to delimit therein an inhibition chamber (78) in fluid communication with the annular damping cavity (52), and a pad (76) rigidly connected to the piston (74) and arranged outside the enclosure (72), so that the set of respective pads (76) of the secondary damping devices (70), which constitutes said friction means, is movable between the rest position and the service position by means of sliding of the pistons (74) respectively within the enclosures (72) each in a respective sliding direction having a component along the axis (46) of the rolling bearing.

7. Device according to any one of claims 3 to 6, in which the elastic return means (84) comprise, for the secondary damping device (70) or for each secondary damping device (70), an elastic member housed in a activation chamber (80) delimited by the piston (74) within the enclosure (72) of the damping device in question, on one side opposite the inhibition chamber (78) thereof, so as to urge the piston (74) in the direction of the inhibition chamber (78).

8. Device according to any one of claims 3 to 7, wherein said sliding direction is parallel to the axis (46) of the rolling bearing.

9. A device according to any one of claims 1 to 8, wherein the friction structure is an integral part of a body forming the outer ring (38) or the elastically deformable structure (45), or wherein the friction structure is a wear part fixed to a body forming the outer ring (38) or the elastically deformable structure (45).

10. Turbomachine, comprising at least one device according to any one of claims 1 to 9.

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