Vibration monitoring device for a mechanical power transmission system of an aircraft engine

Abstract

One aspect of the invention relates to a device 100 for vibration monitoring of a mechanical power transmission system of an aircraft engine comprising: A first accelerometer 101 adapted to measure a first vibration signal continuously when the first accelerometer 101 is implemented, A housing 106 comprising a processing unit 103 configured to: acquire the first vibration signal and store the first vibration signal measured during a predetermined period of time, calculate an N2 speed from the acquired and stored first vibration signal, identify a first event from the N2 speed, when the first event is identified, control storage of the N2 speed, the stored first vibration signal and a timestamp associated with the N2 speed, the storage being carried out in a storage memory 107, and implement the first accelerometer 101 when a second event is identified. Figure to be published with the abstract: Figure 1

Description

Title of the invention: Device for monitoring the vibration of a mechanical power transmission system of an aircraft engine TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of vibration monitoring and in particular of vibration monitoring of an aircraft engine.

[0002] The present invention relates to a vibration monitoring device and in particular to a vibration monitoring device for a mechanical power transmission system of an aircraft engine. The invention also relates to a vibration monitoring method implemented by the vibration monitoring device. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Monitoring the health status, commonly called "Health Monitoring" in English, of an aircraft engine is essential to ensure passenger safety during an aircraft flight. For example, excessive vibration excitation at the level of an engine can cause damage, such as cracking or breaking of an engine component due to vibration fatigue. Thus, it is known to monitor the behavior of the engine bearings. Patent EP1367226 B1 entitled "Method and system for detecting damage to the rotor of an aircraft engine" is an example of such a monitoring method. Indeed, through feedback, they have been identified as being particularly subject to degradation during the life of the engine. The bearings, consisting of ball or roller bearings, support the shafts that connect the compressor to the turbine, by relying on the fixed structures of the turbojet engine.

[0004] Monitoring the health status of an aircraft engine is therefore carried out using a vibration monitoring device comprising a "Health Monitoring" box and vibration sensors dedicated to this task. This device is permanently installed on the engine, i.e. its installation on the engine is permanent. The vibration sensors, generally two in number, have the function of monitoring the engine bearings. The position of the vibration sensors is defined during the engine design phase. The "Health Monitoring" box records and analyzes the vibration signatures from the vibration sensors in order to estimate the health status of the aircraft engine. Given the criticality of the tasks performed by the vibration monitoring device, the "Health Monitoring" box is developed with a high level of security, i.e. DAL level, for "Design Assurance Level" in English, C or sometimes DAL level A.

[0005] It is sometimes desirable to obtain additional vibration measurements after the engine has been put into service. For example, when an event during a flight indicates a risk concerning the health of the aircraft engine, it would be useful to add sensors in order to be able to carry out these additional vibration measurements. Currently, the addition of new vibration sensors after the engine has been put into service has many disadvantages since the addition of such sensors was not foreseen during the design. For example, the addition of new vibration sensors would require modifying the interfaces of the “Health Monitoring” box to connect this or these new sensors. The addition of new vibration sensors would also require updating the software of the “Health Monitoring” box to process this data.Thus, adding new additional sensors would require modifying, after the design phase, the operation of critical components, such as the "Health Monitoring" box. This would therefore potentially have significant impacts on the engine and would harm the overall reliability of the engine. Finally, this would lead to an increase in the development times of the software for the "Health Monitoring" box and the immobilization of the aircraft on the ground. Thus, in practice, adding additional sensors to an engine already in service is not carried out because it has too many disadvantages.

[0006] There is therefore a need for a vibration monitoring device which does not have, or at least limits, the aforementioned drawbacks. Summary of the invention

[0007] The invention provides a solution to the problems mentioned above by proposing a device for monitoring an aircraft engine. The device allows monitoring of the aircraft engine by carrying out additional measurements of vibration signals at a mechanical power transmission system of the aircraft engine. These measurements are further processed by the processing unit of the device to automatically control the storage of data. This data can then be used, for example by people on the ground, in order to identify a possible fault affecting the aircraft engine and therefore repair the component of the engine affected by the fault.

[0008] One aspect of the invention relates to a device for vibration monitoring of a mechanical power transmission system of an aircraft engine comprising: • a first accelerometer adapted to measure a first continuous vibration signal when the first accelerometer is implemented, • A housing comprising a processing unit configured to: • acquire the first vibration signal and store the first vibration signal measured during a predetermined period of time, • calculate an N2 regime from the first vibration signal acquired and stored, • identify a first event from the N2 regime, • when the first event is identified, ordering storage of the N2 regime, the first stored vibration signal and a timestamp associated with the N2 regime, the storage being carried out in a storage memory, and • implement the first accelerometer when a second event is identified.

[0009] Thanks to the invention, it is possible to monitor an aircraft engine by obtaining additional vibration measurements, i.e. in addition to those permitted by the vibration sensors installed on the aircraft engine permanently, on the mechanical power transmission system of an aircraft engine. In addition, the device is modular, i.e. it can be considered as an additional module that can be added to or removed from the engine after it has been put into service without harming the operation and overall reliability of the engine. Indeed, the components of the device according to the invention can be mounted and removed from an aircraft engine. Thus, the housing and the accelerometer of the device are modules that can be mounted and removed from an aircraft engine.Furthermore, the presence and operation of the components of the device according to the invention do not alter the operation of the aircraft engine since the device according to the invention operates autonomously with respect to the other components of the engine. The device is in particular autonomous from the point of view of vibration measurement but also of the calculations carried out from this vibration measurement. In particular, no connection to the “Health Monitoring” box is necessary. Finally, the device can be used on the ground, for example when the aircraft is on the ground or when the engine is on a test bench, but also in flight, i.e. when the engine is in operation.

[0010] In addition to the characteristics which have just been mentioned in the preceding paragraph, the device according to one aspect of the invention may have one or more complementary characteristics among the following, considered individually or according to all technically possible combinations: • the first accelerometer has a first electrical consumption, • the housing further comprises a second accelerometer adapted to measure a second vibration signal and having a second electrical consumption lower than the first electrical consumption of the first accelerometer, • The processing unit is further configured to identify the second event from the second vibration signal, • the housing further comprises an electric battery adapted to power the first accelerometer, the second accelerometer, the processing unit and the storage memory, • the device further comprises a noise-cable connecting the housing to the first accelerometer, the noise-cable being adapted to transmit to the housing the vibration signal measured by the first accelerometer, • the measurement of the second vibration signal is carried out at regular intervals lasting between 1 and 20 seconds, • the predetermined time period for acquisition and storage of the first vibration signal by the processing unit is between 30 and 120 seconds, • the second event is a start-up phase of the aircraft engine and the first event is an operating mode of the aircraft engine among: • the aircraft engine start-up phase, • an end of the aircraft engine start phase • a taxi phase, • a take-off phase, • an end of the ascent phase, • a cruising speed phase, • the start of a descent phase, and • an aircraft engine shutdown phase,

[0011] A second aspect of the invention relates to an aircraft engine comprising a vibration monitoring device according to the invention and a mechanical power transmission system. In one example, the first accelerometer of the device according to the invention is placed at a middle portion of the mechanical power transmission system and the housing of the device according to the invention is located at a casing of a fan of the aircraft engine.

[0012] A third aspect of the invention relates to an aircraft comprising an engine according to the invention.

[0013] A fourth aspect of the invention relates to a method for vibration monitoring of a mechanical power transmission system of an aircraft engine implemented by a device according to the invention comprising the steps of: • When the second event is identified by the processing unit (103), implemented (202) by the processing unit (103) of the first accelerometer (101), • Measurement (203) of the first vibration signal by the first accelerometer (101), • Acquisition and storage (204), for the predetermined duration of the first vibration signal by the processing unit (103), and • Calculation (205) of the N2 regime from the first vibration signal acquired and stored by the processing unit (103); • When the first event is identified by the processing unit (103) from the calculated N2 regime, control (206) the storage, of the calculated N2 regime, of the first acquired and stored vibration signal and of the timestamp associated with the N2 regime, the storage being carried out in the storage memory (107).

[0014] In addition to the characteristics which have just been mentioned in the preceding paragraph, the vibration monitoring method according to one aspect of the invention may have one or more complementary characteristics among the following, considered individually or according to all technically possible combinations: • the process is implemented by a device in which: • the first accelerometer has a first electrical consumption, • the housing further comprises a second accelerometer (102) adapted to measure a second vibration signal and having a second electrical consumption lower than the first electrical consumption of the first accelerometer, and • The processing unit is further configured to identify the second event from the second vibration signal. • The method further comprises an initial step of measuring the second vibration signal by the second accelerometer.

[0015] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0016] The figures are presented for information purposes only and in no way limit the invention. • [Fig.l] shows a schematic representation of an example of a vibration monitoring device according to the invention. • [Fig.2] shows a block diagram of an example of a process of vibration monitoring according to the invention • [Fig.3] shows a schematic representation of an example of placement of an accelerometer, included in a vibration monitoring device according to the invention, on a mechanical power transmission system of an aircraft engine. DETAILED DESCRIPTION

[0017] Unless otherwise specified, the same element appearing in different figures has a single reference.

[0018] [Fig.l] shows a schematic representation of an example of a vibration monitoring device 100 according to the invention.

[0019] The device 100 allows vibration monitoring of a mechanical power transmission system of an aircraft engine. For example, the device 100 can be used to monitor vibration behavior of an accessory gear box, commonly referred to as AGB for "Accessory Gear Box" in English, or of a speed reducer of an aircraft engine, commonly referred to as RGB for "Reduction Gear Box" in English. Thus, when the device monitors an AGB or an RGB, it allows monitoring of the gears and bearings of these systems, as illustrated in [Fig. 3] in which the AGB is denoted 300, which can cause high vibration levels. In addition, the device 100 allows, by monitoring the vibration behavior of a mechanical power transmission system of an aircraft engine, to detect an anomaly in the vibration behavior of the system before the appearance of damage to the system.For example, thanks to the invention, an anomaly in the vibration behavior of the mechanical power transmission system can be detected at least 60 flights before the occurrence of damage to the system by the device 100.

[0020] The device 100 comprises a housing 106. The housing 106 is for example a machined aluminum housing, resistant to the environmental conditions on an aircraft engine. There are two compartments in this housing. A first compartment comprises the electronic elements and a second compartment comprises only the battery. The existence of these two separate compartments meets a need to ensure physical separation between the battery and the electronic devices, for flight safety reasons. The compartment comprising the battery can for example be physically distant from the compartment comprising the electronic elements. Thus, in the event of leaks of electrochemical fluids from the battery, the electronic elements are not damaged. The housing is adapted to contain a processing unit 103 and a storage memory 107. The housing 106 can also contain, in an exemplary embodiment, an electric battery. The housing is closed.Thus, all the components in the housing are protected from the external environment, for example from the temperature of the external environment. The surface of the housing may have a hole allowing the passage of a cable. The surface of the housing may also have a USB port, from the English, "Universal Serial Bus". In one example, the housing has the shape of a rectangular parallelepiped having a length of 137 millimeters, a width of 99 millimeters and a thickness of 35.5 millimeters.

[0021] The device 100 comprises a first accelerometer 101. This first accelerometer 101 is located outside the housing 106. The first accelerometer 101 can be fixed, by gluing or using one or more screws, to the component of the aircraft engine to be monitored. The first accelerometer 101 measures a first vibration signal continuously, i.e. without interruption. This continuous measurement is carried out only when the first accelerometer 101 is implemented. The terms “implemented” mean in the present application that the first accelerometer is put to work or, in other words, activated. Thus, when it is not implemented, the first accelerometer is put on standby or even switched off, i.e. not electrically powered. In such a case, the first accelerometer does not measure the first vibration signal.In one example, the first accelerometer measures a first vibration signal at high frequency, i.e. at a frequency between 1 and 50,000 hertz, for example 32,768 hertz. In one example, compatible with the previous example, the first accelerometer 101 is a piezoelectric accelerometer. The first accelerometer 101 may be connected to the housing 106, for example by a cable 109 or by any other means enabling it to transmit the data of the first vibration signal measured to the housing 106, more precisely to the various elements included in the housing.

[0022] In a preferred embodiment, compatible with the previous examples, the first accelerometer 101 is connected to the housing 106 by a noise-reducing cable 109. The noise-reducing cable 109 allows the transmission to the housing 106, more precisely to the various elements included in the housing, of the vibration signal measured by the first accelerometer 101. The noise-reducing cable 109 is for example a cable having a resistance to a high temperature, for example up to 150°C or even 300°C. In order not to be disturbed by parasitic signals, the cable is made up of two conductive wires. In addition, the pair of conductive wires is twisted, then covered with a shielding braid and a sheath covering the shielding braid. The use of a noise-reducing cable 109 makes it possible to limit the parasitic effects on the signals which pass through this noise-reducing cable 109.

[0023] The housing 106 of the device 100 also comprises a processing unit 103. The processing unit 103 placed in the housing 106 is configured to acquire the first vibration signal during a predetermined period of time and store this first vibration signal acquired during a predetermined period of time. In other words, the processing unit 103 is configured to acquire the first vibration signal during a predetermined period of time and the processing unit 103 is also configured to store the first vibration signal acquired. The terms “configured for” mean in the present application that the processing unit has been “programmed for”. In other words, the terms “configured for” mean that the processing unit is adapted to execute one or more operations allowing the implementation of a task, possibly in a fully automatic or semi-automatic manner. The processing unit may comprise one or more processors, preferably two processors. The processing unit may further comprise one or more memory units, preferably four memory units.

[0024] In one example, the predetermined time period for acquiring and storing the first vibration signal is between 30 and 120 seconds, preferably 60 seconds. This first vibration signal is then used by the processing unit 103 to calculate an N2 speed. An N2 speed corresponds to the rotational speed of the high-pressure shaft of the aircraft engine. An example of a method for obtaining the N2 speed of an aircraft engine from the first vibration signal is disclosed in French patent application FR2300770 entitled “Determination of an average of a carrier frequency of a pseudo-periodic signal”. The invention relates to a method for determining an average of a carrier frequency of a pseudo-periodic signal s(t) over a period T, the method being implemented by a computer and comprising: • Receive samples of the signal S ( t ) sampled over the period T, the signal being relative to a physical quantity associated with a system; • Construct, using an iterative search mechanism, a stretched signal by resampling the signal s{t) according to a resampling frequency fe evolving over the period T and depending on a variation of the carrier frequency of the signal during the period T, the stretched signal s'fy being oversampled with respect to the signal $(t); • Determine the average of the carrier frequency by comparing the stretched signal 5^) to one or more reference signals.

[0025] The processing unit 103 is further configured to identify a first event from the N2 regime. By “identifying an event from the N2 regime” is meant “identifying an event from a set of predefined events from an N2 regime”. For example, the event may correspond to a rising or falling peak in the N2 regime, which may be detected by noting that a rising or falling edge of the N2 regime reaches a predefined threshold. When the first event is identified, the processing unit 103 sends a control signal so that data is stored in a storage memory 107. This storage memory 107 is also located in the housing 106. In one example, the storage memory 107 can store a maximum of 32 gigabits of data. Limiting the size of the storage memory 107 makes it possible to limit its power consumption.

[0026] The data stored in the storage memory 107 following the sending of the signal by the processing unit 103 comprise the calculated N2 regime. The stored data also comprise the first vibration signal used to perform the calculation of the N2 regime, that is to say the first vibration signal acquired and stored by the processing unit 103 during the predetermined period of time. The term “stored” means that the data, in this case the first vibration signal, are stored in memory by the processing unit 103. Finally, the data stored in the storage memory 107 comprise a timestamp associated with the N2 regime, for example the time at which the calculation of the N2 regime was carried out. In addition, it is possible to partially store the acquired data depending on the nature of the first and / or second event. The storage can for example be carried out for 20 to 80% of all the acquired data.In other words, for 120 seconds of acquired data it is possible to store only 30 and 120 seconds of data. In one example, compatible with the previous examples, the processing unit 103 comprises two processors. When the processing unit comprises two processors, a first processor and a second processor work in parallel by sliding windows. Indeed, while the first processor acquires and stores the first vibration signal for a time period T, the second processor calculates a regime N2 from the first vibration signal acquired and stored for a preceding time period T1, the time period T1 being a time period preceding the time period T, for example a time period T1 immediately preceding the time period T.For the time period T+1, the time period T+1 being a time period following the time period T, the first processor acquires and stores the first vibration signal for the time period T+1 while the second processor calculates an N2 regime from the first vibration signal acquired and stored for the time period T. The calculated N2 regime therefore makes it possible to correlate the first vibration signal with the meshing level of the parts of the monitored mechanical transmission system, and therefore to detect abnormal vibration behaviors. In addition, the presence of these two processors makes it possible to acquire and store the first vibration signal without interruption, when these processors are implemented, while performing the calculations of the N2 regime from this first vibration signal.In the case where a first event has not been identified from the N2 regime, the second processor does not send a control signal, thus, no data is stored in the storage memory 107.

[0027] In one example, consistent with the preceding examples, the first identified event corresponds to an operating mode of the aircraft engine. For example, the first identified event is an operating mode of the aircraft engine among: • an aircraft engine start-up phase, • an end of the aircraft engine start phase, • a taxi phase, which corresponds to the moment when the aircraft moves on the ground, • a takeoff, • an end of climb phase, which corresponds to the transition between the climb phase of a flight and the cruise phase, i.e. the moment when the planned climb to cruising altitude is completed. This end of climb phase is commonly called in English “top of climb”, • a cruising speed phase, • the start of a descent phase, which corresponds to the transition from the cruise phase of a flight to the descent phase, or the moment when the planned descent to the final approach altitude is initiated. This start of the descent phase is commonly referred to in English as the “top of descent”, and • an aircraft engine flameout.

[0028] This identification of the first event can be carried out using the method disclosed in French patent application FR2210673 entitled “Method for detecting an operating mode of a rotating machine, in particular for an aircraft during flight”. Thus, for a 10-hour flight, it is possible in this example to limit the time for measuring the first vibration signal and calculating the N2 regime to a few minutes, for example 5 minutes.

[0029] The processing unit 103 is configured to implement the first accelerometer 101 when a second event is identified. Thus, the processing unit 103 controls the implementation and the putting into standby, or even the stopping, of the first accelerometer 101. This implementation is carried out when a second event is identified. This second event can be of different natures. For example, the second event can be an interaction of a user, such as pressing a button of a user interface to control the recording of the first vibration signal.

[0030] In one example, compatible with the preceding examples, the device 100 may further comprise a second accelerometer 102. This second accelerometer 102 may be placed in the housing 106 or outside the housing 106. The second accelerometer 102 is configured to measure a second vibration signal. This second vibration signal may be used to identify the second event. As a reminder, the identification of this second event is the condition for implementation, by the processing unit 103, of the first accelerometer 101. This identification of the second event from the second vibration signal is performed by the processing unit 103. In one example compatible with the preceding examples, the second event is a start-up phase of the aircraft engine. The implementation of the identification of this second event may consist of identifying a period of time, of a predetermined duration, during which the second vibration signal is greater than a predetermined vibration level threshold value.

[0031] In the preceding example, the second accelerometer 102 may have a second electrical consumption which is lower than a first electrical consumption of the first accelerometer 101. There are many characteristics influencing the electrical consumption of the accelerometer such as the frequency of capture, the age of the accelerometer, etc. For example, the second accelerometer has an electrical consumption less than or equal to 45 microamperes, noted pA, in “measurement” mode and 0.1 pA in “stand-by” mode. Thus, the electrical consumption of the device 100 is optimized since the first accelerometer 101 is only implemented when a second event is identified from the measurement of the second vibration signal carried out by the second accelerometer 102. In one example, compatible with the preceding examples, the measurement of the second vibration signal is carried out at regular intervals of a duration of between 1 and 20 seconds.Preferably, the measurement of the second vibration signal is carried out every 5 seconds.

[0032] In one example, consistent with the preceding examples, the housing 106 further comprises a fastening means for placing the housing 106 on a component of an aircraft engine. In one example, the fastening means makes it possible to place the housing 106 on a component of an aircraft engine while maintaining a distance, for example between 10 and 100 millimeters and preferably 30 millimeters, between the closest surface of the housing and the surface of the engine component on which the housing is fixed. This distance also makes it possible to maintain an air space making it possible to thermally insulate the housing 106 with respect to temperature variations of the aircraft engine component. This fastening means, like that used to fix the first accelerometer 101, is adapted to the environmental constraints of an aircraft engine, in particular to thermal and vibration constraints.For example, the means for attaching the housing 106 may consist of screws allowing the housing 106 to be placed quickly, i.e. in a maximum of 20 minutes, on a component of the aircraft engine. It is for example possible to attach the housing 106 to a mounting bracket which is permanently attached to the aircraft engine. Regarding the means for attaching the first accelerometer 101, a means similar to that used to attach the housing 106 may be used. Thus, the device 100 may be of the Plug & Play type.

[0033] In one example, compatible with the previous examples, the housing 106 further comprises an electric battery 108. This electric battery 108 makes it possible to supply the electricity necessary for the operation of the various components of the device 100. Thus, the battery 108 supplies the electricity necessary for the operation of the first accelerometer 101, the processing unit 103, and the storage memory 107. The electric battery 108 can also power the second accelerometer 102 when it is included in the device 100. Thus, the device 100 is energy autonomous to ensure its operation. This electric battery 108 is suitable for operating at temperatures ranging, for example, between -55°C and 90°C. In addition, in order to meet fire resistance constraints, it is for example possible to use a battery comprising lithium cells. The lithium cells are for example insulated from each other by a specific coating to contain the fluids. This cell pack can also be encapsulated in a stainless steel box, and placed in the housing 106 in a compartment physically segregated from the compartment containing the other elements of the housing 106.

[0034] In an alternative to the previous example, the energy required for the operation of the device 100, and therefore for all of its components, can be provided by a piezoelectric or thermoelectric type energy harvester.

[0035] In one example, compatible with the preceding examples, the housing 106 further comprises a means for transmitting the data stored in the storage memory 107 to a ground maintenance station. The transmitted data may comprise all or part of the data stored on the storage memory 107. Preferably, the transmission means, such as a USB connection, makes it possible to transmit all of the data in less than 15 minutes, preferably less than 10 minutes. For this, the transmission means has a suitable rate, high enough to transmit this set of data in the allotted time. For example, the transmission may be carried out by a wired link and / or by a wireless link. This transmission may also be carried out autonomously with respect to the other communication systems of the aircraft.

[0036] In one example, compatible with the preceding examples, the housing 106, as well as all of the components included in the housing 106, has a mass less than 1% of the mass of a casing of a fan of the aircraft engine monitored by the device 100. For example, the mass of the housing 106 is less than or equal to 800 grams, and preferably less than or equal to 700 grams. Thus, the device 100 does not impact the overall dynamics of the aircraft engine when it is in operation.

[0037] A second aspect of the invention relates to an aircraft engine comprising: • a device 100 according to the invention, and • a mechanical power transmission system.

[0038] In one example, the housing 106 of the device 100 may be placed at a casing of a fan of the aircraft engine and the first accelerometer 101 of the device 100 may be placed at a middle portion of the system. mechanical power transmission of the engine. [Fig. 3] illustrates an example of placement of the first accelerometer 101 of the device 100 at the middle portion of an AGB 300.

[0039] [Fig. 2] is a block diagram illustrating the steps of an example of the vibration monitoring method 200 according to the invention. The mandatory steps of the example of the method 200 are indicated by a solid line rectangle and the optional steps are indicated by a dotted line rectangle.

[0040] The method 200 for vibration monitoring of a mechanical power transmission system of an aircraft engine is implemented by the vibration monitoring device 100.

[0041] In an example in which the device 100 comprises a second accelerometer 102, an optional first step 201 of the method 200 may comprise measuring the second vibration signal by the second accelerometer 102.

[0042] A second step 202 of the method 200 is performed when the second event is identified by the processing unit 103. This second step 202 comprises an implementation 202 by the processing unit 103 of the first accelerometer 101. In one example, the identification of the second event can be performed from the second vibration signal when step 201 has been performed.

[0043] A third step 203 of the method 200 comprises the measurement of the first vibration signal by the first accelerometer 101. This step 203 is carried out when the first accelerometer is implemented by the processing unit 103 and therefore when a second event has been identified.

[0044] A fourth step 204 of the method 200 comprises acquiring the first vibration signal for the predetermined duration. The fourth step 204 also comprises storing, by the first vibration signal, the first acquired vibration signal.

[0045] A fifth step 205 of the method 200 comprises the calculation of the N2 regime from the first vibration signal acquired and stored by the processing unit 1031.

[0046] A sixth step 206 of the method 200 is performed when the first event is identified by the processing unit 103. This first event is identified from the calculated N2 regime. This sixth step 206 comprises sending a control signal so that the storage of the calculated N2 regime, of the first vibration signal acquired and stored by the processing unit 103 and of the timestamp associated with the N2 regime is carried out. This storage is carried out in the storage memory 107.

Claims

Claims

1. Device (100) for vibration monitoring of a mechanical power transmission system of an aircraft engine comprising: A first accelerometer (101) having a first power consumption and being adapted to measure a first vibration signal continuously when the first accelerometer (101) is implemented, A housing (106) comprising: • a second accelerometer (102) adapted to measure a second vibration signal and having a second electrical consumption lower than the first electrical consumption of the first accelerometer, • a processing unit (103) configured to: - acquire the first vibration signal and store the first vibration signal measured during a predetermined period of time, - calculate an N2 regime from the first vibration signal acquired and stored, the N2 regime corresponding to a rotation speed of a high pressure shaft of the aircraft engine, - identify a first event from the N2 regime, - when the first event is identified, ordering storage of the N2 regime, of the first stored vibration signal and of a timestamp associated with the N2 regime, the storage being carried out in a storage memory (107), - identify a second event from the second vibration signal, and - implementing the first accelerometer (101) when a second event is identified.

2. Device (100) according to claim 1 wherein: - the first accelerometer (101) has a first electrical consumption, - the housing (106) further comprises a second accelerometer (102) adapted to measure a second vibration signal and having a second electrical consumption lower than the first electrical consumption of the first accelerometer, and - The processing unit (103) is further configured to identify the second event from the second vibration signal.

3. Device (100) according to claim 2 wherein the housing (106) further comprises an electric battery (108) adapted to power: - the first accelerometer (101) and the second accelerometer (102), - the processing unit (103), and - the storage memory (107).

4. Device (100) according to any one of claims 2 to 3 wherein: - the measurement of the second vibration signal is carried out at regular intervals of a duration of between 1 and 20 seconds, and / or - the predetermined period of time for acquisition and storage of the first vibration signal by the processing unit (103) is between 30 and 120 seconds.

5. Device (100) according to any one of claims 2 to 4 wherein the second event is a start phase of the aircraft engine and the first event is an operating mode of the aircraft engine among: - the start phase of the aircraft engine, - an end of the start phase of the aircraft engine - a taxi phase, - a takeoff phase, - an end of a climb phase, - a cruise phase, - the start of a descent phase, and - an aircraft engine shutdown phase.

6. Device (100) according to any one of the preceding claims further comprising a noise-cable (109) connecting the housing (106) to the first accelerometer (101), the noise-cable (109) being adapted to transmit to the housing (106) the vibration signal measured by the first accelerometer (101).

7. An aircraft engine comprising a vibration monitoring device (100) according to any one of the preceding claims and a mechanical power transmission system.

8.

9. Aircraft comprising an engine according to the preceding claim. Method (200) for vibration monitoring of a mechanical power transmission system of an aircraft engine implemented by a device (100) according to any one of claims 1 to 6 comprising the steps of: - Measurement (201) of the second vibration signal by the second accelerometer (102), - When the second event is identified by the processing unit (103) from the second vibration signal, implementation (202) by the processing unit (103) of the first accelerometer (101), - Measurement (203) of the first vibration signal by the first accelerometer (101), - Acquisition and storage (204), for the predetermined duration of the first vibration signal by the processing unit (103), and - Calculation (205) of the N2 regime from the first vibration signal acquired and stored by the processing unit (103);- When the first event is identified by the processing unit (103) from the calculated N2 regime, order (206) the storage, of the calculated N2 regime, of the first acquired and stored vibration signal and of the timestamp associated with the N2 regime, the storage being carried out in the storage memory (107).;

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