Detector of mechanical contact between a flexible radial cage and a sleeve surrounding this cage in a turbojet engine bearing

Abstract

The invention relates to a turbomachine comprising a bearing (13) which includes a flexible cage (27) receiving an outer ring of a bearing (28), a sleeve (33) surrounding this flexible cage (27) and radially offset from it, the flexible cage (27) being rigidly attached to the sleeve (33) by means of a support (29) exhibiting a certain degree of flexibility. According to the invention: – the sleeve (33) includes an electrically insulating inner ring (34) carrying on its inner 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 the ring (36). Figure for the abstract: Figure 2

Description

Title of the invention: Detector of the mechanical contact of a flexible radial cage with a sleeve surrounding this cage in a turbojet engine bearing. Technical field

[0001] The invention relates to the detection of mechanical contact that may occur between a so-called flexible cage and a sleeve surrounding this cage in an inter-shaft bearing or a "squeeze film damper" type bearing of a turbomachine such as a turbojet engine. PRIOR TECHNOLOGY

[0002] A turbofan engine comprises an inlet sleeve receiving upstream air which is drawn in by a low-pressure compressor, before being split into a central primary flow and a secondary flow surrounding the primary flow. After passing through the low-pressure compressor, the secondary flow is propelled downstream to generate thrust by being blown around the primary flow.

[0003] After passing through 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.

[0004] The moving blades of the low-pressure compressor and the low-pressure turbine are supported by a low-pressure rotor, which is surrounded by a high-pressure rotor carrying the moving blades of the high-pressure compressor and the high-pressure turbine. This low-pressure rotor is supported by two or more bearings, upstream and downstream respectively, which are supported by structural elements of the engine. The high-pressure rotor is generally supported by two upstream and downstream bearings held either by structural elements of the engine or by the low-pressure rotor, since in this second case, they are referred to as intershaft bearings.

[0005] Such a bearing, which appears in [Fig. 1] where it is identified by 1, comprises a cage 2 said flexible intended to receive an outer ring not shown of a roller bearing surrounding the rotor it carries, and a sleeve 3 surrounding this cage 2 being spaced radially from it by an annular space 4.

[0006] 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 relative to this sleeve, this cage being thus mounted flexibly.

[0007] 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 openwork spaces separating the columns of this cage to form a connection having a certain flexibility.

[0008] In this type of arrangement, the annular space 4 is pressurized with oil to constitute a damper, usually referred to as a "squeeze film damper", allowing the effects of any imbalance of the rotor to be absorbed, so as to reduce the fatigue stress on the cage 2 resulting from this imbalance.

[0009] It may happen that the outer face of the cage 2 comes into contact with the inner face of the sleeve 3, in the case of excessive imbalance resulting, for example, from an incident during engine testing. Such an incident can lead to the degradation or even destruction of the engine under test, so it is useful to detect it.

[0010] However, such detection is complex because the flexible cage and the sleeve are located in the center of the motor, i.e., virtually inaccessible. To date, such detection is achieved by vibration analysis of the motor, but given the significant processing times of such an analysis, detection cannot be performed in real time.

[0011] This situation is even more complex in the case of an intershaft bearing, because the flexible cage is then a rotating element supported by the low-pressure rotor. Furthermore, the components of an intershaft bearing are even more inaccessible than those of other bearings due to their location at the very heart of the engine, between two rotors.

[0012] The object of the invention is to provide a solution to ensure real-time detection of the contact of a flexible cage with the sleeve that surrounds it in a turbojet bearing. Description of the invention

[0013] To this end, the invention relates to a turbomachine comprising a bearing which includes a flexible cage receiving an outer ring of a bearing, a sleeve surrounding this flexible cage and being radially distanced from this flexible cage, the flexible cage being secured to the sleeve by means of a support having radial flexibility, and in which:

[0014] - the sleeve comprises an electrically insulating ring bearing on its inner face an electrically conductive inner ring located radially opposite the flexible cage;

[0015] - an electronic circuit is electrically connected to the inner ring and the flexible cage to emit a signal when the sleeve and the flexible cage are in electrical contact with each other.

[0016] With this arrangement, the detection of mechanical contact between the flexible cage and the sleeve surrounding it is ensured by a very simple electronic circuit, so that the integration of the detector into the turbomachine is easy.

[0017] The invention also relates to a turbomachine as defined above, in which the electronic circuit includes a connected power supply battery electrically to the inner ring, and a signal transmitter electrically connected to the battery and the soft cage.

[0018] The invention also relates to a turbomachine thus defined, in which the signal emitter is a light-emitting diode.

[0019] The invention also relates to a turbomachine as defined above, in which the signal transmitter is electrically connected to the sleeve via a metallic mechanical element carrying the flexible cage.

[0020] 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.

[0021] The invention also relates to a turbomachine thus defined, in which the signal emitter 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.

[0022] The invention also relates to a turbomachine as defined above, in which the electronic circuit is carried by the low-pressure rotor.

[0023] The invention also relates to a turbomachine thus defined, in which the flexible cage comprises an electrically insulating outer ring carrying a conductive outer ring, and in which the signal emitter is electrically connected to the conductive outer ring by a conductive wire. Brief description of the drawings

[0024] Fig. 1 is a cross-sectional view of a known turbojet engine bearing;

[0025] Figure 2 is a cross-sectional view of a rear portion of a turbojet engine comprising a bearing equipped with a detector according to the invention;

[0026] [Fig.3] is a cross-sectional view of the bearing equipped with the detector according to the invention (zoom on [Fig.2]);

[0027] Fig. 4 is a cross-sectional view of a front part of a turbojet engine equipped with the detector according to the invention;

[0028] Fig. 5 is a cross-sectional view of a rear part of a turbojet engine comprising a bearing equipped with a variant of a detector according to the invention;

[0029] Fig. 6 is a cross-sectional view of the bearing equipped with a variant of the detector according to the invention.

[0030] DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0031] The idea behind 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 emitter such as a light-emitting diode, so that all the detection elements are carried by the rotating part.

[0032] On [Fig.2], a rear part 11 of a turbojet engine includes an exhaust casing 12 integrating in its central region a bearing 13 carrying a low-pressure rotor 14.

[0033] This low-pressure rotor 14 is an assembly comprising a central trunnion 16 generally cylindrical surrounded by a cylindrical ferrule 17 ending in a flange 18 to which is fixed a structure of revolution 19 carrying low-pressure turbine blades not shown.

[0034] The bearing 13 carries a roller bearing 21 which surrounds the cylindrical shell 17 so as to ensure the retention and rotational guidance of the entire rear part of this low-pressure rotor 14.

[0035] This engine also includes a high-pressure rotor 22 comprising a generally cylindrical high-pressure journal 23 carrying blades (not visible here) of a high-pressure turbine located upstream of the low-pressure turbine. This high-pressure journal 23 surrounds the central low-pressure journal 16, while its downstream end is surrounded by the cylindrical shell 17.

[0036] As seen in [Fig.2], 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 motor.

[0037] This intershaft bearing 26 which extends in the internal region of the cylindrical shell 17 comprises a cage 27 surrounding the downstream end of the high-pressure trunnion 23 and carrying on its internal face a roller bearing 28 which is mounted around the downstream end of the high-pressure trunnion 23 to ensure its guidance and retention.

[0038] The cage 27 is located at the upstream end of a support 29 of revolution which extends along the inner face of the ferrule 17 to be fixed to the base 31 of this ferrule 17, this support 29 comprising columns 32 extending between the base 31 and the cage 27.

[0039] As can be seen more clearly in [Fig. 3], the bearing 26 further comprises a sleeve 33 carried by the rotational structure 19, located at the end of the ferrule 17 so as to be rigidly held by this ferrule. This sleeve 33 surrounds the flexible cage 27, having an internal diameter greater than the external diameter of the cage 27, and is separated from it by an annular space E. The flexible cage 27 and the sleeve 33 are thus rotating elements forming part of the low-pressure rotor.

[0040] According to the invention, the sleeve 33 comprises an inner ring 34 made of electrically insulating material, on the inner face of which is mounted an internal cylindrical ring 36 which is electrically conductive which is located radially opposite the flexible cage 27.

[0041] 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 inner face of the ferrule 17 and the columns 32 to pass through the wall of the low pressure trunnion 16 ([Fig.2]) at the level of a radial hole 38 ([Fig.3]).

[0042] As can be seen in [Fig.2], the trunnion 16 has a general hollow cylindrical shape, and the conducting wire 37 runs along the inner face of this trunnion 16 to join the upstream end AM of this trunnion 16.

[0043] In the front part, as shown in [Fig.4], the trunnion 16 has on its inner face an electric battery 39, which can also be a cell, which is connected to the upstream end of the conducting wire 37. As seen in [Fig.4], the upstream end of the trunnion has a front cone 41 at the end of which is mounted a light-emitting diode 42, which is connected on one side to the battery 39 by a conducting wire 43, and on the other side to a metallic part of the trunnion 16 by means of another conducting wire 44.

[0044] As shown in [Fig.3], in the event of a significant imbalance, if the cage 27 moves radially and comes into contact with the sleeve 33, it establishes electrical contact with the inner ring 36 which is electrically conductive and which is connected by the wire 37 to the battery 39, so that in this case the supply circuit of the diode 42 is formed to cause the ignition of this diode.

[0045] As can be seen in the figures, the assembly consisting of the diode 42 with the battery 39 and the conducting 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.

[0046] As schematically represented in [Fig.4], 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 lighting of the diode 42 is detected.

[0047] The camera 46 can also be a high-speed camera, so as to identify the moments when the diode lights up, so as to deduce the establishment of contact of the cage 27 with the sleeve 33 when it is an intermittent contact.

[0048] In the example of [Fig.4], 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 conditioned by the general arrangement of the motor.

[0049] In the example which has been described in relation to figures 2 and 3, the trunnion 16 is part of the diode supply circuit by constituting the ground of this circuit.

[0050] Alternatively, as illustrated in [Fig. 5], the power supply to diode 42 ([Fig. 4]) does not pass through the body of trunnion 16, but through a conducting wire return wire 47 ([Fig. 6]). In this embodiment of the invention, which is shown in more detail in [Fig. 6], the flexible cage 27 has on its outer periphery an electrically insulating outer ring 48 which is surrounded by a conductive outer ring 49.

[0051] The outer ring 49 is electrically connected to one end of the return wire 47 is equipped with an electrically insulating sheath that runs along the columns 32 to pass through the wall of the trunnion 16 at the radial hole 38. As shown in [Fig. 5], the return wire 47 runs along the inner face of the trunnion 16, following essentially the same path as the wire 37, to reach the diode 42 and be connected to it at its other end. As in the case of [Fig. 4], the diode is connected to the inner ring 36 via the wires 37 and 43 connected to the battery 39, so the operation is the same as in the example of [Fig. 4].

[0052] In the examples illustrated in Figures 2 to 6, the invention is implemented to detect contact between the cage and the sleeve of an intershaft bearing. However, 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 portion of the motor, so that in this case, the diode is also carried by the motor stator.

[0053] 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 use of cumbersome instrumentation, by ensuring this detection by means of a very simple, self-contained electronic circuit. The mechanical contact detection information is transmitted by a signal emitter, which is a light-emitting diode in the example shown in the figures, but the signal emitter can be of another nature, such as a radio transmitter instead of the diode.

Claims

Demands

1. Turbomachine comprising a bearing (13) which includes a flexible cage (27) receiving an outer ring of a bearing (28), a sleeve (33) surrounding this flexible cage (27) while being radially distant from this flexible cage (27), the flexible cage (27) being secured to the sleeve (33) by means of a support (29) having radial flexibility, and in which: - the sleeve (33) includes an electrically insulating ring (34) carrying on its inner face an electrically conductive inner ring (36) located radially opposite the flexible cage (27); - an electronic circuit (45) is electrically connected to the inner ring (36) and to the flexible cage (27) to emit a signal when the sleeve (33) and the flexible cage (27) are in electrical contact with each other.

2. Turbomachine according to claim 1, wherein the electronic circuit (45) comprises a power supply battery (39) electrically connected to the inner ring (36), and a signal transmitter electrically connected to the battery and the flexible cage (27).

3. Turbomachine according to claim 2, wherein the signal emitter is a light-emitting diode (42).

4. Turbomachine according to claim 2, wherein the signal transmitter is electrically connected to the flexible cage (27) via a metallic mechanical element carrying the flexible cage (27).

5. Turbomachine according to claim 1, wherein the bearing (13) is an intershaft bearing carried by a low pressure rotor (14), and wherein the electronic circuit (45) is carried by this low pressure rotor (14).

6. Turbomachine according to claim 5, wherein the signal emitter is a light-emitting diode (42) carried at an upstream end of the low-pressure rotor (14), and wherein a fixed camera (46) is positioned opposite the diode (42).

7. Turbomachine according to claim 5, wherein the electronic circuit (45) is carried by the low pressure rotor (14).

8. Turbomachine according to claim 2, wherein the flexible cage (27) comprises an electrically insulating outer ring (48) carrying an outer conductive ring (49), and in which the signal transmitter is electrically connected to the outer conductive ring (49) by a conductive wire (47).

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