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
10 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
15 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.
2 0 Several solutions have already been offered to that end, using for
example carbon segmented gaskets associated with various implementation modes.
Fig. 1 illustrates 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 shaft 1 is rotatably supported by a bearing, carried by a
25 case 2, including a balling bearing 3. A sleeve 4 rotatably integral with the shaft 1 is
sandwiched between the balling bearing 3 and the shaft 1, according to arrangements
known per se in the application to turbomachines. The balling bearing 3 is comprised in
an enclosure 5 where both air and oil are present for lubricating the balling bearing 3
ensured in a known manner per se are present.
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Beyond the supporting bearing, the shaft 1 is surrounded by a so-called
air enclosure 6 which should remain free of oil because any oil upwelling in some
compartments of the turbomachine would be detrimental to a proper operation. A
sealing device 10 is thus provided between the shaft 1 and the case 2 at the separation
5 between the oil enclosure 5 and the air enclosure 6.
The sealing device 10 includes a static sealing ring 7, consisting of
carbon segments which are held together using a circumferential spring 22, this spring 22
tightening the carbon segments against the sleeve 4. The static sealing ring 7 is associated
with a rotating surface 8, that can include grooves 12 to provide for lift. This rotating
10 surface 8 is extended to a cylindrical surface 9, in relation with a labyrinth oil outlet
system 11 to prevent oil particles from reachingthe carbon segments.
The static sealing ring 7 is kept in a metal supporting jacket 14 (or
support 14) by the circumferential spring 22 and axial springs 21, pressed against a ring 18
which is held in the support 14 by a stop joint 20. The support 14 is centred without
15 tightening by means of an O-ring 19 placed between the support 14 and a case
element 24 acting as a cover and thus enabling the static part of the gasket device 10 to
be attached to the case 2 of the turbomachine.
Dynamic tightness is achieved between the respective cooperating
cylindrical faces 16 and 17 of the carbon segments 7 and of the rotating surface 8. Static
20 tightness is achieved between the carbon segments 7 and the static face 23 of the
support 14, located at the labyrinth oil outlet ring 11, to avoid any radial leak. Thus, to
succeed in providing satisfactory dynamic tightness and static tightness, the static sealing
ring 7 should be mounted so as to retain in use a high concentricity with respect to the
rotor and a perpendicularity with respect to the static face 23.
2 5 However, known assemblies from prior art, such as that described in
reference to Fig. 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 support
14, i.e. generally steel because of tribology stresses, substantially expands half as much as
30 that selected for the case element 24, i.e. generally aluminium for most recent engines.
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3
Consequently, it is possible that a ball joint movement is created about the O-ring 19
which, 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
5 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
10 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.
15 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
20 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
25 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.
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i 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
5 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
10 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.
15 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
20 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.
2 5 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
30 maximum radial clearance opening between the case element and the elastic seals, when
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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.
BRIEF DESCRIPTION OF DRAWINGS
The invention will be better understood upon reading the following
detailed description of an exemplary embodiment thereof in no way limiting, as well as
upon examining the schematic and partial figures of the appended drawing, wherein:
-Fig. 1 represents, in a cross-section view through a plane passing
through the axis of rotation of the shaft, a part of a turbomachine bearing including an
enclosure gasket device according to prior art, and
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- Fig. 2 represents an enlarged view of a turbomachine bearing similar to
that of Fig. 1, however including a gasket device according to the invention.
In all the figures, identical references can indicate identical or analogous
elements.
5 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
10 for a turbomachine bearing will be described hereinafter in reference to Fig. 2.
10 The turbomachine bearing is similar to that described in reference to
Fig. 1.
Thus, the bearing includes a balling bearing 3 mounted between a
sleeve 4 integral with a shaft 1 and a case 2, the sleeve 4 having a rotating surface 8 and
the case 2 including a case element 24 acting as a cover for the gasket device 10. The
15 gasket device 10 is able to separate an oil enclosure 5 from the balling bearing 3 and an
air enclosure 6 from the turbomachine.
On the other hand, the sealing device 10 represented in Fig. 2 differs
from that represented in Fig. 1 in that it includes a supporting jacket 14 including two
housings 25 each accommodating an elastic seal 19, in accordance with the invention.
2 0 More precisely, the gasket device 10 includes a segmented gasket 7,
consisting of a static sealing ring of carbon segments held tcgether by a circumferential
spring 22, which is mounted in association with the rotating surface 8 of the sleeve 4 to
ensure most of the tightness of the gasket device 10. The latter also includes a supporting
jacket 14 (or support 14) for holding the segmented gasket 7, this support 14 being
25 mounted between the sleeve 4 and the case element 24.
The support 14 includes first and second grooves 25 accommodating
first and second elastic seals 19 respectively that enable the support 14 to be centred
over the case element 24.
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Preferably, as represented in Fig. 2, the first and second grooves 25 can
be identical and the first and second elastic seals 19 can be O-rings with the same
diameter, made of an elastomeric material.
In order to achieve an optimum centring, that is an optimum alignment
5 of the axis of the support 14 with the axis of the case element 24, both O-rings 19 can be
spaced apart from each other as much as possible. In other words, the distance D which
separates the first and second grooves 25 can be as great as possible, being in particular
equal or higher than the width W of the first and second grooves 25.
The centring of the support 14 to the case element 24 can be made
10 easier, and even be made when cold, the support 14 being for example able to be
mounted in its bore according to the H7g6 fitting defined by the system of IS0 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.
15 In particular, the support 14 could include more than two grooves 25
each associated with an elastic seal 19. The grooves 25 and/or the elastic seals 19 can be
identical or not.
The phrase "including one" should be understood as being a synonym of
"including at least one", unless otherwise specified.

WE CLAIMS:-
1. A gasket device (10) for a turbomachine bearing, said bearing
including a balling bearing (3) mounted between a sleeve (4) integral with a shaft (1) and
5 a case (2), the sleeve (4) having a rotating surface (8) and the case (2) including a case
element (24) acting as a cover for the gasket device (lo), the gasket device (10) being able
to separate an oil enclosure (5) from the balling bearing (3) and an air enclosure (6) from
the turbomachine, the gasket device (10) including:
- a segmented gasket (7), mounted in association with the rotating
10 surface (8) of the sleeve (4), for providing most of the tightness of the device (lo),
- a supporting jacket (14) for holding the segmented gasket (7), which
jacket is mounted between the sleeve (4) and the case element (24), the support jacket
(14) including a first groove (25) accommodating a first elastic seal (19) for centring the
c
i: supporting jacket (14) over the case element (24),
15 characterised in that the supporting jacket (14) includes a second
:j groove (25) accommodating a second elastic seal (19) for centring the supporting
jacket (14) over the case element (24).
2. The device according to claim 1, characterised in that the first and
20 second grooves (25) are identical.
3. The device according to claim 1 or 2, characterised in that the first
and second elastic seals (19) have the same dimensions, in particular the same diameter.
2 5 4. The device according to one of the preceding claims, characterised in
that the first and second elastic seals (19) are O-rings.
5. The device according to any of the preceding claims, characterised in
that the first and second grooves (25) are spaced apart from each other by a distance (D)
30 equal to or higher than the width (W) of at least one of the first and second grooves (25).
, < ,
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6. The device according to any of the preceding claims, charaderised in
that the first dnd second elastic seals (19) are made of an elastomeric material.
. ,
5 7.. The device according to any of the preceding claims, characterised in
that the rotating surface (8) of the sleeve (4) is extended by a cylindricil surface (9), and
in that the supporting jacket (14) includes a labyrinth oil ou;ilet system (11) in relation
'
with the cyiindrical,surface (9).
10 8. Tke device according to any of the preceding claims, chdracterised in
that the segmented gasltet (7) includes a sealing ring including a set of one or more
I carbon segments.
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9. The device according to the preceding claim, characterised in that the
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1 I 15 one or mot-e carbon segm.ents are held together by a circumferential spring (22) and/or
I pressed against the supporting jacket (14.) by one or more axial springs (21) pressing on a
I
1 stop joint (20).
10. A turbomachine characterised in that it includes a gasltet device (10)
20 according to any of the preceding claims.