FR3127262A1 - Detector of the mechanical contact of a flexible radial cage with a sleeve surrounding this cage in a turbojet bearing - Google Patents

Abstract

The invention relates to a turbomachine comprising a bearing (13) which comprises a flexible cage (27) receiving an outer ring of a bearing (28), a sleeve (33) surrounding this flexible cage (27) being radially at a distance from this flexible cage (27), the flexible cage (27) being rigidly secured to the sleeve (33) via a support (29) having a certain flexibility. According to the invention: - the sleeve (33) comprises an electrically insulating internal ring (34) bearing on its internal face an electrically conductive ring (36) located radially opposite the flexible cage (27); – a conductive wire (37) is connected to the ring (36), and an electronic circuit is connected to the conductive wire (37) and to the flexible cage (27) to emit a signal in the event of electrical contact between the flexible cage ( 27) and ring (36). Figure for abstract: Figure 2

Description

Detector of the mechanical contact of a flexible radial cage with a sleeve surrounding this cage in a turbojet bearing

The invention relates to the detection of the mechanical contact which may be established between a so-called flexible cage and a sleeve surrounding this cage in an inter-shaft bearing or of the “ squeeze film damper ” type of a turbomachine such as a turbojet.

PRIOR ART

A turbofan engine has an inlet pipe receiving air upstream which is drawn in by a low pressure compressor, before being divided into a central primary flow and a secondary flow surrounding the primary flow. After passing the low pressure compressor, the secondary flow is propelled downstream to generate thrust by being blown around the primary flow.

After passing the low pressure compressor, the primary flow passes through a high pressure compressor before reaching a combustion chamber to then be expanded in a high pressure turbine and in a low pressure turbine.

The moving blades of the low-pressure compressor and of the low-pressure turbine are carried by a so-called low-pressure rotor which is surrounded by a so-called high-pressure rotor carrying the moving blades of the high-pressure compressor and the high-pressure turbine. This low-pressure rotor is held by two or more bearings, respectively upstream and downstream, which are carried by structural elements of the engine. The high pressure rotor is generally carried by means of two bearings upstream and downstream held either by structural elements of the engine or by the low pressure rotor, given that in this second case, we speak of intershaft bearings.

Such a landing which appears on the where it is identified by 1, comprises a so-called flexible cage 2 intended to receive an outer ring, not shown, of a roller bearing surrounding the rotor that it carries, and a sleeve 3 surrounding this cage 2 being spaced radially from that -here by an annular space 4.

The cage 2 is connected to the sleeve 3 by means of a support having a certain flexibility to benefit from radial mobility or flexibility with respect to this sleeve, this cage thus being mounted flexibly.

More particularly, the upstream end of the cage 2 is connected to a fixed member 6 by means of a support comprising a squirrel cage structure 7 which provides flexible support thanks to the perforated spaces separating the columns of this cage to form a bond having some flexibility.

In this type of arrangement, the annular space 4 is pressurized with oil to form a damper, usually referred to as a " squeeze film damper ", making it possible to absorb the effects of any imbalance in the rotor, so as to reduce the fatigue stress on cage 2 resulting from this unbalance.

It may happen that the external face of the cage 2 comes into contact with the internal face of the sleeve 3, in the case of an excessive imbalance resulting for example from an incident during an engine test. Such an incident can lead to the degradation or even the destruction of the engine being tested, so it is useful to detect it.

However, such detection is complex due to the fact that the flexible cage and the sleeve are located in the center of the engine, that is to say almost inaccessible. To date, such detection is provided by engine vibration analysis, but given the significant processing times of such an analysis, detection cannot be performed in real time.

This situation is even more complex in the case of an intershaft bearing, because the flexible cage is then a rotating element carried by the low-pressure rotor. In addition, the components of an intershaft bearing are even more inaccessible than those of other bearings due to their location in the heart of the engine, between two rotors.

The object of the invention is to provide a solution for ensuring real-time detection of the contact of a flexible cage with the sleeve that surrounds it in a turbojet bearing.

To this end, the subject of the invention is a turbomachine comprising a bearing which comprises a flexible cage receiving an outer ring of a bearing, a sleeve surrounding this flexible cage while being radially at a distance from this flexible cage, the flexible cage being secured to the sleeve via a support having radial flexibility, and in which:

- the sleeve comprises an electrically insulating ring bearing on its inner face an electrically conductive inner ring located radially opposite the flexible cage;

– an electronic circuit is electrically connected to the inner ring and the sleeve to emit a signal when the sleeve and the inner ring are in electrical contact with each other.

With this arrangement, the detection of the mechanical contact between the flexible cage and the sleeve which surrounds it is ensured by a very simple electronic circuit, so that the integration of the detector into the turbomachine is easy.

The invention also relates to a turbomachine thus defined, in which the electronic circuit comprises an electrical supply battery electrically connected to the inner ring, and a signal transmitter electrically connected to the battery and to the sleeve.

The invention also relates to a turbomachine thus defined, in which the signal transmitter is a light-emitting diode.

The invention also relates to a turbomachine thus defined, in which the signal transmitter is electrically connected to the sleeve via a metallic mechanical element carrying the sleeve.

The invention also relates to a turbomachine thus defined, in which the bearing is an intershaft bearing carried by a low pressure rotor, and in which the electronic circuit is carried by this low pressure rotor.

The invention also relates to a turbomachine thus defined, in which the signal transmitter is a light-emitting diode carried at an upstream end of the low-pressure rotor, and in which a fixed camera is positioned opposite the diode.

The invention also relates to a turbomachine thus defined, in which the electronic circuit is carried by the low-pressure rotor.

The invention also relates to a turbomachine thus defined, in which the sleeve comprises an electrically insulating outer ring carrying a conductive outer ring, and in which the signal transmitter is electrically connected to the conductive outer ring by a conductive wire.

There is a sectional view of a known turbojet bearing;

There is a sectional view of a rear part of a turbojet comprising a bearing equipped with a detector according to the invention;

There is a sectional view of the bearing equipped with the detector according to the invention (zoom on the );

There is a sectional view of a front part of a turbojet equipped with the detector according to the invention;

There is a cross-sectional view of a rear part of a turbojet engine comprising a bearing equipped with a detector variant according to the invention;

There is a sectional view of the bearing equipped with a detector variant according to the invention.

DETAILED DISCUSSION OF PARTICULAR EMBODIMENTS

The basic idea of the invention is to identify the mechanical contact of the cage with the sleeve by electrical detection, and to transmit this information by means of a signal transmitter such as a light-emitting diode, so that all of the detection elements are carried by the rotating part.

On the , a rear part 11 of the turbojet engine comprises an exhaust casing 12 integrating in its central region a bearing 13 carrying a low-pressure rotor 14.

This low-pressure rotor 14 is an assembly comprising a generally cylindrical central pin 16 surrounded by a cylindrical shroud 17 terminated by a flange 18 to which is fixed a structure of revolution 19 carrying low-pressure turbine blades, not shown.

The bearing 13 carries a roller bearing 21 which surrounds the cylindrical shroud 17 so as to maintain and guide in rotation the entire rear part of this low pressure rotor 14.

This engine also comprises a high-pressure rotor 22 comprising a generally cylindrical high-pressure trunnion 23 carrying the blades (not visible here) of a high-pressure turbine located upstream of the low-pressure turbine. This high pressure trunnion 23 surrounds the central low pressure trunnion 16 while having its downstream end surrounded by the cylindrical shell 17.

As seen on the , the downstream part AV of the high pressure rotor 22 is held and guided in rotation by an intershaft bearing 26 carried by the low pressure rotor 14, the rotors 14 and 22 rotating around an axis AX corresponding to the longitudinal axis of the engine.

This intershaft bearing 26 which extends in the internal region of the cylindrical shroud 17 comprises a cage 27 surrounding the downstream end of the high pressure journal 23 and carrying on its internal face a roller bearing 28 which is mounted around the end downstream of the high pressure trunnion 23 to ensure its guidance and maintenance.

The cage 27 is located at the upstream end of a support 29 of revolution which extends along the internal face of the ferrule 17 to be fixed to the base 31 of this ferrule 17, this support 29 comprising 32 extending between the base 31 and the cage 27.

As visible more clearly on the , the bearing 26 further comprises a sleeve 33 carried by the revolving structure 19 being located at the end of the ferrule 17 so as to be held rigidly by this ferrule. This sleeve 33 surrounds the flexible cage 27, having an internal diameter greater than the external diameter of the cage 27 to be separated therefrom by an annular space E. The flexible cage 27 and the sleeve 33 are thus rotating elements forming part of the low pressure rotor.

According to the invention, the sleeve 33 comprises an internal ring 34 of electrically insulating material, on the internal face of which is mounted a cylindrical internal ring 36 which is electrically conductive and located radially opposite the flexible cage 27.

The internal conductive ring 36 is electrically connected to a first end of a conductive wire 37 provided with an insulating sheath, which runs along the internal face of the ferrule 17 and the columns 32 to pass through the wall of the low pressure trunnion 16 ( ) at a radial hole 38 ( ).

As seen on the , the trunnion 16 has the general shape of a hollow cylinder, and the conductive wire 37 runs along the internal face of this trunnion 16 to join the upstream end AM of this trunnion 16.

In the front part, as shown in the , the pin 16 carries on its internal face an electric battery 39, which can also be constituted by a battery, which is connected to the upstream end of the conductive wire 37. As visible on the , the upstream end of the trunnion carries a front cone 41 at the end of which is mounted a light-emitting diode 42, which is connected on the one hand to the battery 39 by a conductive wire 43, and on the other hand to a metal part of the pin 16 via another conductive wire 44.

As shown by the , in the event of significant unbalance, if cage 27 deflects radially and comes into contact with sleeve 33, it establishes electrical contact with internal ring 36 which is electrically conductive and which is connected by wire 37 to battery 39, so that in this case the supply circuit of the diode 42 is formed to cause the ignition of this diode.

As visible in the figures, the assembly consisting of the diode 42 with the battery 39 and the conductive wires constitutes an electronic circuit 45 for detecting the contact of the cage 27 with the sleeve 33 which surrounds it, which is autonomous and carried by the low pressure rotor 14.

As shown schematically in the , a camera 46 can advantageously be placed opposite the diode 42, being connected to a processing circuit to control the emission, for example, of a sound signal when the ignition of the diode 42 is detected.

The camera 46 can also be a high-speed camera, so as to identify the instants at which the diode lights up, so as to deduce therefrom the establishment of contact of the cage 27 with the sleeve 33 when it comes to intermittent contact.

In the example of the , the diode is placed in the center of the front end of the low pressure rotor, but it can also be carried by another part of the low pressure rotor, the choice of its positioning being able to be conditioned by the general layout of the engine.

In the example which has been described in relation to FIGS. 2 and 3, pin 16 forms part of the diode supply circuit by constituting the ground of this circuit.

Alternatively, as shown in , the power supply of the diode 42 ( ) does not pass through the body of the trunnion 16, but through a return conductor wire 47 ( ). In this variant of the invention which appears in more detail on the , the flexible cage 27 carries at its outer periphery an electrically insulating outer ring 48 which is surrounded by a conductive outer ring 49.

The outer ring 49 is electrically connected to one end of the return wire 47 is equipped with an electrically insulating sheath passes along the columns 32 to pass through the wall of the journal 16 at the level of the radial hole 38. As visible on the the return wire 47 runs along the internal face of the journal 16 by substantially following the same path as the wire 37, to join the diode 42 and be connected thereto by its other end. As in the case of the , the diode is connected to the inner ring 36 through the wires 37 and 43 connected to the battery 39, so that the operation is the same as in the example of the .

In the examples illustrated in Figures 2 to 6, the invention is implemented to detect the contact of the cage with the sleeve of an intershaft bearing. But the invention can also be applied to a simple bearing, such as a bearing supporting the low pressure journal 16, for which the cage and the sleeve are then carried by a stator part of the motor, so that in this case , the diode is also carried by the motor stator.

In general, the invention makes it possible to detect the mechanical contact of a flexible cage with a bearing sleeve in real time, without requiring the implementation of heavy instrumentation elements, by ensuring this detection by means of a very simple autonomous electronic circuit. The mechanical contact detection information is transmitted by a signal transmitter which is a light-emitting diode in the example of the figures, but the signal transmitter can be of another nature, such as for example a radioelectric transmitter instead of the diode.

Claims (8)

Turbomachine comprising a bearing (13) which comprises a flexible cage (27) receiving an outer race of a bearing (28), a sleeve (33) surrounding this flexible cage (27) being radially at a distance from this flexible cage (27 ), the flexible cage (27) being secured to the sleeve (33) via a support (29) having radial flexibility, and in which:
- the sleeve (33) comprises an electrically insulating ring (34) bearing on its inner face an inner ring (36) electrically conductive located radially opposite the flexible cage (27);
– an electronic circuit (45) is electrically connected to the inner ring (36) and to the sleeve (33) to emit a signal when the sleeve (33) and the inner ring (36) are in electrical contact with each other other. A turbomachine according to claim 1, wherein the electronic circuit (45) comprises an electrical supply battery (39) electrically connected to the inner ring (36), and a signal transmitter electrically connected to the battery and to the sleeve (33) . A turbomachine according to claim 2, wherein the signal transmitter is a light emitting diode (42). Turbomachine according to Claim 2, in which the signal transmitter is electrically connected to the sleeve (33) via a metallic mechanical element carrying the sleeve (33). Turbomachine according to Claim 1, in which the bearing (13) is an intershaft bearing carried by a low-pressure rotor (14), and in which the electronic circuit (45) is carried by this low-pressure rotor (14). Turbomachine according to Claim 5, in which the signal transmitter is a light-emitting diode (42) carried at an upstream end of the low-pressure rotor (14), and in which a fixed camera (46) is positioned opposite of the diode (42). Turbomachine according to Claim 5, in which the electronic circuit (45) is carried by the low-pressure rotor (14). A turbomachine according to claim 2, wherein the sleeve has an electrically insulating outer ring (48) carrying a conductive outer ring (49), and wherein the signal transmitter is electrically connected to the conductive outer ring (49) by a wire conductor (47).