GASKET DEVICE FOR THE BEARING OF A TURBOMACHINE, COMPRISING TWO ELASTIC SEALS

A gasket device for a turbomachine bearing, configured to separate an oil enclosure and an air enclosure from the turbomachine, including a segmenting gasket for providing most of tightness of the device and a supporting jacket for holding the segmented gasket. The supporting jacket includes a first groove accommodating a first elastic seal for centering the supporting jacket. The supporting jacket includes a second groove accommodating a second elastic seal for centering the supporting jacket, or aligning the axis of the supporting jacket with the axis of the rotor.

TECHNICAL FIELD

The present invention relates to the field of turbomachines. It relates to a gasket device for a turbomachine bearing, as well as the turbomachine including such a device.

The invention is applicable to any type of terrestrial or aeronautical turbomachines, in particular to aircraft turbomachines such as turbofans and turboprop engines. More preferentially, the invention is applicable to a twin spool axial flow turbofan.

STATE OF PRIOR ART

Conventionally, a turbomachine bearing supporting a shaft rotating inside a fixed case includes a balling bearing arranged in an enclosure where the lubrication thereof is ensured. However, any oil migration should be avoided toward some compartments of the turbomachine and the tightness should thus be ensured at the separation between the oil containing bearing enclosure and an air-neighbouring enclosure which must be kept free of oil.

Several solutions have already been offered to that end, using for example carbon segmented gaskets associated with various implementation modes.

FIG. 1illustrates an example of use of such a segmented gasket, also called segmented radial seal (SRS), including in particular a static sealing ring consisting of carbon segments. In this figure, a shaft1is rotatably supported by a bearing, carried by a case2, including a balling bearing3. A sleeve4rotatably integral with the shaft1is sandwiched between the balling bearing3and the shaft1, according to arrangements known per se in the application to turbomachines. The balling bearing3is comprised in an enclosure5where both air and oil are present for lubricating the balling bearing3ensured in a known manner per se are present.

Beyond the supporting bearing, the shaft1is surrounded by a so-called air enclosure6which should remain free of oil because any oil upwelling in some compartments of the turbomachine would be detrimental to a proper operation. A sealing device10is thus provided between the shaft1and the case2at the separation between the oil enclosure5and the air enclosure6.

The sealing device10includes a static sealing ring7, consisting of carbon segments which are held together using a circumferential spring22, this spring22tightening the carbon segments against the sleeve4. The static sealing ring7is associated with a rotating surface8, that can include grooves12to provide for lift. This rotating surface8is extended to a cylindrical surface9, in relation with a labyrinth oil outlet system11to prevent oil particles from reaching the carbon segments.

The static sealing ring7is kept in a metal supporting jacket14(or support14) by the circumferential spring22and axial springs21, pressed against a ring18which is held in the support14by a stop joint20. The support14is centred without tightening by means of an O-ring19placed between the support14and a case element24acting as a cover and thus enabling the static part of the gasket device10to be attached to the case2of the turbomachine.

Dynamic tightness is achieved between the respective cooperating cylindrical faces16and17of the carbon segments7and of the rotating surface8. Static tightness is achieved between the carbon segments7and the static face23of the support14, located at the labyrinth oil outlet ring11, to avoid any radial leak. Thus, to succeed in providing satisfactory dynamic tightness and static tightness, the static sealing ring7should be mounted so as to retain in use a high concentricity with respect to the rotor and a perpendicularity with respect to the static face23.

However, known assemblies from prior art, such as that described in reference toFIG. 1, for a segmented gasket s are generally incapable of meeting these needs, in particular for applications aimed at by the present invention. In particular, the tightness can be difficult to achieve in use given that the selected material for the support14, i.e. generally steel because of tribology stresses, substantially expands half as much as that selected for the case element24, i.e. generally aluminium for most recent engines. Consequently, it is possible that a ball joint movement is created about the O-ring19which, by deteriorating the contact between the friction surfaces, increases the radial clearance opening and decreases the tightness efficiency thus achieved.

Besides, international application WO 2012/022550 A2 describes another example of sealing device, placed between two parts of a turbocompressor, enabling a separation between two enclosures to be made under different pressures.

DISCLOSURE OF THE INVENTION

Thus, there is a need for a new assembly of a segmented gasket of a gasket device for a turbomachine bearing, enabling the tightness of the device in use to be improved. There is in particular a need to design an assembly of a segmented gasket which is adapted to existing requirements regarding the choice of the materials of turbomachine components.

The invention aims at overcoming at least partly the abovementioned needs and drawbacks relating to prior art embodiments.

Thus, one purpose of the invention, according to one of its aspects, is to provide a gasket device for a turbomachine bearing having two elastic seals. Said bearing includes a balling bearing mounted between a sleeve integral with a shaft and a case. The sleeve has a rotating surface and the case includes a case element acting as a cover for the gasket device. The gasket device is able to separate an oil enclosure of the balling bearing from an air enclosure of the turbomachine. It includes:

a segmented gasket, including in particular one or more carbon segments, which seal is mounted in association with a rotating surface of the sleeve, to ensure in particular most of the tightness of the device,

a supporting jacket for holding the segmented gasket, which jacket is mounted between the sleeve and the case element, the supporting jacket including a first groove accommodating a first elastic seal for centring the supporting jacket over the case element, in particular for aligning the axis of the supporting jacket with the axis of the case element.

The gasket device for the turbomachine bearing is characterised in that the supporting jacket includes a second groove accommodating a second elastic seal for centring the supporting jacket over the case element.

The solution provided by the invention can enable various drawbacks of known prior art solutions to be avoided while ensuring the tightness searched for between an air enclosure and an oil enclosure. By virtue of the invention, it can for example be possible to overcome difficulties relating to the radial clearance opening because of existing differences between the materials of the turbomachine components in terms of expansion. Moreover, the centring of the supporting jacket over the case element through two elastic seals can enable case vibrations to be dampened, and thus axial wear of the carbon segments of the segmented gasket to be reduced.

The gasket device according to the invention can further include one or more of the following characteristics taken alone or according to any possible technical combinations.

The first and second grooves can be identical, having in particular the same dimensions and shape.

The first and second grooves are advantageously formed on the part of the supporting jacket which is located facing the case element.

The supporting jacket can include more than two grooves each accommodating an elastic seal for centring the supporting jacket over the case element, in particular at least three, at least four, or even five grooves each accommodating an elastic seal.

The first and second elastic seals can have the same dimensions. In particular, the first and second elastic seals can have the same diameter.

The first and second elastic seals advantageously contact the case element.

The first and second elastic seals can be of any type, being in particular O-rings.

The first and second elastic seals can be selected such that the maximum radial clearance opening between the case element and the elastic seals, when the turbomachine is in use, is within the range of admissible minimum and maximum values because of design requirements for crushing an elastic seal, in particular an O-ring. The first and second elastic seals can be fit upon assembling the gasket device with the maximum admissible crush value.

The first and second grooves can be spaced apart from each other by a distance being higher, lower or equal to the width of at least one of the first and second grooves, in particular to the width of each of the first and second grooves.

The gap between the first and second grooves can be maximum to make the centring of the supporting jacket over the case element optimum.

The first and second elastic seals can be made of any type of elastic material, in particular of an elastomeric material.

The rotating surface of the sleeve can be extended by a cylindrical surface, and the supporting jacket can include a labyrinth oil outlet system in relation with the cylindrical surface.

The segmented gasket can include a sealing ring including a set of one or more carbon segments, that can be held together by a circumferential spring and/or pressed against the supporting jacket by one or more axial springs pressing against a stop joint, in particular a stop ring (of the SRS type or face joints).

Yet another object of the invention, according to another of its aspects, is to provide a turbomachine characterised in that it includes a gasket s device such as previously defined.

In all the figures, identical references can indicate identical or analogous elements.

Moreover, the different parts represented in the figures are not necessarily drawn at a uniform scale, for the figures to be more legible.

DETAILED DISCLOSURE OF A PARTICULAR EMBODIMENT

An exemplary embodiment of the invention relating to a gasket device for a turbomachine bearing will be described hereinafter in reference toFIG. 2.

The turbomachine bearing is similar to that described in reference toFIG. 1.

Thus, the bearing includes a balling bearing3mounted between a sleeve4integral with a shaft1and a case2, the sleeve4having a rotating surface8and the case2including a case element24acting as a cover for the gasket device10. The gasket device10is able to separate an oil enclosure5from the balling bearing3and an air enclosure6from the turbomachine.

On the other hand, the sealing device10represented inFIG. 2differs from that represented inFIG. 1in that it includes a supporting jacket14including two housings25each accommodating an elastic seal19, in accordance with the invention.

More precisely, the gasket device10includes a segmented gasket7, consisting of a static sealing ring of carbon segments held together by a circumferential spring22, which is mounted in association with the rotating surface8of the sleeve4to ensure most of the tightness of the gasket device10. The latter also includes a supporting jacket14(or support14) for holding the segmented gasket7, this support14being mounted between the sleeve4and the case element24.

The support14includes first and second grooves25accommodating first and second elastic seals19respectively that enable the support14to be centred over the case element24.

Preferably, as represented inFIG. 2, the first and second grooves25can be identical and the first and second elastic seals19can be O-rings with the same diameter, made of an elastomeric material.

In order to achieve an optimum centring, that is an optimum alignment of the axis of the support14with the axis of the case element24, both O-rings19can be spaced apart from each other as much as possible. In other words, the distance D which separates the first and second grooves25can be as great as possible, being in particular equal or higher than the width W of the first and second grooves25.

The centring of the support14to the case element24can be made easier, and even be made when cold, the support14being for example able to be mounted in its bore according to the H7g6 fitting defined by the system of ISO fittings.

Of course, the invention is not restricted to the exemplary embodiment that has just been described. Various modifications can be made thereto by those skilled in the art.

In particular, the support14could include more than two grooves25each associated with an elastic seal19. The grooves25and/or the elastic seals19can be identical or not.

The phrase “including one” should be understood as being a synonym of “including at least one”, unless otherwise specified.