TRANSMISSION SYSTEM WITH TORQUE SENSOR

Abstract

The transmission system (100) comprises: - a gear or a gear train (102) comprising pinions (P1, P2, P2', P3), of which a pinion, called the measuring pinion (P2, P2'), transmits a torque, called the transmitted torque, the measuring pinion (P2, P2') having an axial force dependent on the transmitted torque; - bearings for guiding the pinions (P1, P2, P2', P3); - a torque sensor (104) designed to provide a measurement signal (S) of the transmitted torque by measuring the axial force; and - a data processing device (106) comprising: a frequency analysis module (110) designed to analyze a frequency spectrum of the torque measurement signal (S) in order to detect at least one damage in the gear or gear train (102) or the bearings, and a low-pass filter (108) of the torque measurement signal (S) to obtain an average transmitted torque (C). Figure for the abstract: Fig. 1

Description

Title of the invention: TRANSMISSION SYSTEM WITH TORQUE SENSOR Technical field of the invention

[0001] The present invention relates to a transmission system with a torque sensor, an aircraft comprising such a transmission system, and a data processing method. Technological background

[0002] An aircraft such as a rotorcraft generally includes a transmission system interposed between a turboshaft engine and a propulsion system, for example, a rotary-wing system in the case of a rotorcraft. The transmission system is generally a reduction gear and can be single, double, or N-stage reduction.

[0003] The transmission system is generally designed for desired operating conditions, particularly average torque. During aircraft operation, it is therefore necessary to maintain the torque for which the transmission system was designed, so an average torque sensor is often required in the transmission system.

[0004] In the field of rotorcraft turboshaft engines, the following torque sensors are often used: - Torsional torque sensors designed to compare the phase shift of a reference shaft driven in rotation but not subjected to the torque to be measured and of a power shaft subjected to the torque to be measured; - hydraulic torque sensors in which an axial thrust of a pinion is estimated by means of a hydraulic pressure measurement automatically regulated via a control valve and pushing back the axial thrust, so that the pressure measurement is representative of the torque to be measured.

[0005] In addition, European patent EP 3 289 329 B1 describes an axial force torque sensor designed to measure an axial force representative of the torque to be measured, by means of a measurement of a deformation of a membrane.

[0006] Furthermore, for example to carry out predictive maintenance, it is necessary to detect damage in the transmission system.

[0007] For this purpose, the following sensors are sometimes used: - Encoder wheels, either in oil or without oil, are used to determine the rotor rotation with great precision. Analyzing even the smallest irregularities theoretically provides information about the transmission's condition. The required sensitivity (measurement precision, clock frequencies), the associated data processing, and the integration of such a measurement in or out of oil make this approach complex at high rotational speeds; - Vibration sensors or strain gauges mounted on a transmission system housing. This is the most common solution because it is simple to implement. However, using the housings adds a complex mechanical assembly between the sensor and the source, with the added difficulty of understanding the transfer function. This solution may require multiple sensors; - External or internal microphone: this simple solution allows monitoring a failure from one or a few sensors. However, in the aeronautical field, the surrounding noise of the turbine could mask the noise of the failure until a significant advance is made; - Particle counters: This solution for monitoring the passage of particles through the oil allows tracking the degradation kinetics of mechanical components. The cost of this solution limits the number of sensors on the machine, especially for small helicopter turboshaft engines. Thus, a single sensor can monitor the entire transmission system but will not allow for the identification of the component undergoing degradation, the estimation of the degradation kinetics or the consequences of a potential failure, and therefore will not allow for targeted maintenance tasks by focusing on the module to be disassembled. Consequently, this solution is generally used in conjunction with another solution.

[0008] Thus, at least two types of sensors are needed to obtain an average torque measurement and damage monitoring in the transmission system.

[0009] It may therefore be desirable to provide a transmission system which makes it possible to overcome at least some of the aforementioned problems and constraints. Summary of the invention

[0010] A transmission system is therefore proposed, characterized in that it comprises: - a gear or a gear train comprising pinions, of which a pinion, called a measuring pinion, transmits a torque, called the transmitted torque, the measuring pinion presenting an axial force dependent on the transmitted torque; - pinion guide bearings; - a torque sensor designed to provide a torque measurement signal by measuring axial force; and - a data processing device comprising: • a frequency analysis module designed to analyze a frequency spectrum of the torque measurement signal in order to detect at least one instance of damage in the gear, gear train, or bearings, and • a low-pass filter of the torque measurement signal to obtain an average transmitted torque.

[0011] Thus, thanks to the invention, a single torque sensor is used both to provide an average torque measurement usable, for example, by a controller—that is, relatively stable over time—and to detect damage. Furthermore, an axial force torque sensor can easily be placed in an intermediate gear, which facilitates its integration when the output shaft is not accessible.

[0012] The invention may further include one or more of the following optional features, according to any technically possible combination.

[0013] Optionally, the low-pass filter is designed to average the torque measurement signal over several revolutions of the measuring pinion.

[0014] Optionally also, the low-pass filter has a cutoff frequency at -3 dB of at least 0.5 events per turn.

[0015] Optionally also, the measuring pinion has helical teeth, the gear or gear train has a housing relative to which the measuring pinion is mounted freely in translation, and the torque sensor is designed to follow an axial translation, representative of the axial force, of the measuring pinion relative to the housing and to provide, as a torque measurement signal, a measurement signal of the axial translation representative of the axial force.

[0016] Optionally, the torque sensor also includes: - a part mounted to move in translation relative to the housing along the axis of rotation of the measuring pinion, but fixed in rotation relative to the housing, the part being further mounted to move in rotation around the axis of rotation relative to the measuring pinion, but fixed to the measuring pinion in translation along the axis of rotation; - a flexible membrane fixed to the housing and in contact with one end of the part, so that, when the part follows the axial translation of the measuring pinion, the end deforms the flexible membrane; and - a device for measuring deformation of the flexible membrane caused by the end to provide the torque measurement signal.

[0017] Optionally, the frequency analysis module also includes a peak detection module designed to detect a frequency of at least one peak in the frequency spectrum of the torque measurement signal and a peak analysis module designed to detect damage in the gear or gear train or bearings from the detected frequency or frequencies.

[0018] Optionally also, the frequency analysis module includes a memory in which predetermined frequencies are recorded and the peak analysis module is designed to compare the detected frequency or frequencies with the predetermined frequencies, in order to detect one or more changes among: a shift of one of the predetermined frequencies, an appearance of a frequency with respect to the predetermined frequencies, and a disappearance of one of the predetermined frequencies.

[0019] An aircraft comprising a transmission system according to the invention is also proposed.

[0020] Optionally, the aircraft further includes a memory in which the detection of damage is recorded and / or a human / machine interface designed to trigger a visual and / or audible alarm in response to the detection of damage.

[0021] Optionally, the aircraft may also include: - a propulsion system, for example a rotary-wing aircraft; and - a turboshaft engine; and the transmission system connects the turboshaft engine to the propulsion system so that the latter is driven by the turboshaft engine.

[0022] Optionally, the aircraft also includes a turboshaft engine controller designed to compare the torque measurement to a predefined threshold and to control the turboshaft engine to limit the torque to this predefined threshold.

[0023] A data processing method is also proposed comprising: - receiving a measurement signal of a torque transmitted by a pinion, called a measuring pinion, among several pinions of a gear or a gear train, the measurement signal being provided by a torque sensor designed to measure an axial force presented by the measuring pinion and dependent on the transmitted torque; - an analysis of the frequency spectrum of the torque measurement signal, in order to detect damage in the gear, the gear train, or the pinion guide bearings; and - a low-pass filtering of the torque measurement signal to provide an average transmitted torque.

[0024] Also proposed is a computer program downloadable from a communication network and / or stored on a computer-readable medium, characterized in that it includes instructions for executing the steps of a process of data processing according to the invention, when said program is executed on a computer. Brief description of the figures

[0025] The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the accompanying drawings in which: - [Fig. 1] is a schematic view of a transmission system according to the invention, - [Fig.2] is a kinematic diagram of a gear train of the transmission system of [Fig.1], - Figure [Fig. 3] is a frequency spectrum of a measurement signal of the torque of a pinion in the gear train of Figure [Fig. 2], when the gear train is in good condition. - Figure [Fig. 4] is a frequency spectrum of the torque measurement signal of the gear train pinion in Figure [Fig. 2], when the gear train has two damages, - [Fig.5] is a low-frequency enlargement of the frequency spectrum of [Fig.4], - Figure 6 is a cross-sectional view of an example of a torque sensor implementation. - [Fig. 7] is a block diagram of a data processing method implemented in the transmission system of [Fig. 1], and - [Fig.8] is a functional view of a computer system that can be used to form a data processing device. Detailed description of the invention

[0026] With reference to [Fig.1], an example of a transmission system 100 according to the invention will now be described.

[0027] The transmission system 100 is intended to equip an aircraft, and more particularly a rotorcraft. The transmission system 100 is intended to connect the turboshaft engine to the aircraft's propulsion system, so that the propulsion system is driven by the turboshaft engine. In the case of a rotorcraft, the propulsion system includes a rotating wing.

[0028] The transmission system 100 first includes a gear train 102 comprising several pinions PI, P2, P2', P3, forming gears each made up of two meshed pinions.

[0029] In the illustrated example, the gear train 102 thus comprises four pinions: a driving pinion PI, first and second intermediate pinions P2, P2' which are fixed together, and an output pinion P3. Thus, on the one hand, the pinion PI and the pinion P2 are meshed together to form a first gear E1 and, on the other hand, the pinion P2' and the pinion P3 are meshed together to form a second gear E2.

[0030] The gear train 102 achieves, for example, as in the illustrated example, a reduction in rotational speed between the pinion PI and the pinion P3.

[0031] The transmission system 100 further includes a torque sensor 104 (sometimes called a "torque meter") designed to provide a measurement signal S of a torque transmitted by one of the gears P1, P2, P2', P3, or gear P2, P2' in the illustrated example. Preferably, the torque sensor 104 is undamped, i.e., for example, it is designed to provide the measurement signal S with frequencies above 1 event per revolution, preferably up to at least 500 events per revolution.

[0032] The torque sensor 104 is specifically designed to measure an axial force on the gear P2, P2' resulting from the transmitted torque. In this case, the gear P2, P2' whose torque is measured has helical teeth (as does the gear P3 with which it is meshed). In the illustrated example, all the gears P1, P2, P2', P3 have helical teeth. Furthermore, the gear P2, P2' whose torque is measured is mounted free to rotate and translate relative to a housing (visible in [Fig. 2]). The torque sensor 104 is then designed to follow an axial translation of the gear P2, P2' relative to the housing along an axis of rotation D of the gear P2, P2', this axial translation being representative of the axial force and therefore of the transmitted torque to be measured. The torque sensor 104 is further designed to provide, as a measurement signal S of the torque, a measurement signal of this axial translation.Such an axial force torque sensor 104 has the advantage of being easily housed along the axis of rotation D of the pinion P2, P2' whose torque is measured. An example of an axial force torque sensor 104 that can be used in the invention will be described in more detail later, with reference to [Fig. 6].

[0033] The transmission system 100 further includes a data processing device 106.

[0034] The data processing device 106 first includes a low-pass filter 108 of the measurement signal S designed to provide an average transmitted torque C. For example, the low-pass filter 108 has a cutoff frequency at -3 dB of at least 0.5 events per revolution.

[0035] The data processing device 106 further includes a frequency analysis module 110 designed to analyze a frequency spectrum of the measurement signal S in order to enable the detection of damage in the gear train 102.

[0036] The frequency analysis module 110 includes, first of all, for example, a peak search module 112 designed to detect peak frequencies in the frequency spectrum of the measurement signal S.

[0037] The frequency analysis module 110 further includes, for example, a memory 114 in which predetermined peak frequencies are recorded, these peaks being expected in the absence of damage to the gear train 102. Each of these predetermined frequencies is, for example, associated with an element of the gear system 102, and several predetermined frequencies may be associated with the same element. An element is, for example, a gear or a bearing, for example, a ball bearing or a roller bearing.

[0038] To determine these predetermined frequencies, a first solution is to detect, on the gear train 102, the peaks present at the beginning of the commissioning of the gear train 102, before the appearance of damage.

[0039] Another solution is to detect the peaks present at the beginning of the commissioning of a gear train identical to gear train 102. In this case, a single detection can be carried out for a whole batch of gear trains.

[0040] Another solution is to detect the peaks by numerical simulation of the gear train 102.

[0041] The frequency analysis module 110 further includes, for example, a peak analysis module 116 designed to compare the detected frequencies with predetermined frequencies, for example, to detect one or more changes. Each change is, for example, a shift in one of the predetermined frequencies, or the appearance of a frequency relative to the predetermined frequencies, or the disappearance of one of the predetermined frequencies.

[0042] Fig. 2 is a simplified kinematic diagram of the gear train 102.

[0043] As can be seen, the transmission system 100 includes a housing 202 and the gear train 102 includes, for each of the pinions PI, P2 (and P2'), P3, at least one respective bearing RI, R2, R3 with the housing 202. Each bearing RI, R2, R3 is for example a ball bearing or a roller bearing.

[0044] Thus, in memory 114 are recorded for example: one or more predetermined frequencies for each of the bearings RI, R2, R3, and one or more predetermined frequencies for each of the gears El, E2.

[0045] For example, [Fig. 3] illustrates a frequency spectrum of the measurement signal S for the gear train 102 as shown in [Fig. 2], in the absence of damage. The frequency spectrum gives an amplitude A (on a logarithmic scale) as a function of the frequency F (in events per revolution). Peaks associated with the bearings RI, R2, R3 and the gears E1, E2 are indicated.

[0046] Figure 4 illustrates a frequency spectrum of the measurement signal for the gear train 102 as shown in Figure 2, in the presence of damage and more specifically, a first damage on an inner ring of the bearing RI and a second damage consisting of spalling of an inner ring of the bearing R2. As can be seen, new peaks 402 characteristic of this damage appear.

[0047] Figure 5 is an enlargement of the frequency spectrum of Figure 4, at low frequencies (between 0 and 20 events per revolution). As can be seen, new peaks appear. For example, some of the peaks correspond to roller passage frequencies over the scaling (squares), others to scaling passage frequencies in a load direction (circles), and others to interactions between the two phenomena (triangles).

[0048] With reference to [Fig.6], an example of an embodiment of the axial force torque sensor 104 will now be described.

[0049] In the illustrated example, two bearings R2A, R2B are provided between the pinions P2, P2' which are fixed together and the housing 202.

[0050] The torque sensor 104 first of all comprises a part 602 mounted movable in translation relative to the housing 202 along the axis of rotation D, but fixed in rotation relative to the housing 202.

[0051] The part 602 is further mounted to rotate freely about the axis of rotation D relative to the pinion P2, P2', but is fixed in translation along the axis of rotation D. For this purpose, the torque sensor 104 includes, for example, a bearing 604 between the part 602 and the pinion P2, P2'. Thus, the part 602 follows the axial translation of the pinion P2, P2', but not its rotation.

[0052] The torque sensor 104 further includes a flexible membrane 606 fixed to the housing 202 and in contact with an end 608 of the part 602. Thus, when the part 602 follows the axial translation of the pinion P2, P2', the end 608 deforms the flexible membrane 606.

[0053] The torque sensor 104 further includes a device for measuring the deformation of the flexible diaphragm 606 caused by the end 608, such as, for example, at least one strain gauge 610, also called a strain gauge, attached to the flexible diaphragm 606 so as to be deformed along with it. Generally, the strain gauge 610 has an electrical resistance that varies according to the strain gauge's deformation. Thus, by measuring the change in electrical resistance of the strain gauge 610, it is possible to track the translation of the part 602 and therefore of the pinion P2, P2'.

[0054] Such an axial force torque sensor is described for example in European patent EP3 289 329 Bl.

[0055] With reference to [Fig.7], an example of a method 700 for operating the transmission system 100 will now be described.

[0056] During a step 702, the torque sensor 102 provides a measurement signal S, which is received by the data processing device 106.

[0057] During a step 704, the low-pass filter 104 filters the measurement signal to provide an average transmitted torque C.

[0058] During an optional step 706, a turbocharger controller compares the average transmitted torque C to a predefined threshold and controls the turbocharger to limit the torque to this predefined threshold.

[0059] In parallel with steps 704 and 706, the following steps are implemented.

[0060] During a step 708, the frequency analysis module 110 analyzes a frequency spectrum of the measurement signal S, in order to detect damage in the gear train 102 or the bearings RI, R2, R3, R2A, R2B.

[0061] During an optional step 710, the detection of damage is recorded in memory for retrieval during a subsequent maintenance operation, during which the transmission system 100 will, for example, be repaired to correct the detected damage. Alternatively or in addition, in response to the detection of damage, a visual and / or audible alert is triggered by a human-machine interface, preferably for the benefit of an aircraft pilot.

[0062] With reference to [Fig. 8], the data processing device 106 may, for example, comprise a computer system 800 having a data processing unit 802 (such as a microprocessor) and a main memory 804 (such as RAM, or Random Access Memory) accessible by the processing unit 802. The computer system 800 further comprises, for example, a network interface and / or a computer-readable medium, such as a local medium (such as a local hard drive 806) or a remote medium (such as a remote hard drive accessible via the network interface through a communication network) or a removable medium (such as a USB flash drive, or a CD, or a DVD, or a Digital Versatile Disc) readable by means of a suitable reader of the computer system 800 (such as a port USB or a CD and / or DVD disc drive).A computer program 808 containing instructions for the processing unit 802 is stored non-transiently on a medium, such as the local hard drive 806, and / or is downloadable via the network interface. This computer program 806 is, for example, intended to be loaded into main memory 804, so that the processing unit 802 executes its instructions to implement the actions of the data processing device 106 described previously.

[0063] Alternatively, all or part of these actions could be carried out by hardware modules, i.e. in the form of an electronic circuit, for example micro-wired, not involving a computer program.

[0064] In conclusion, it is clear that a transmission system such as the one described above makes it possible to obtain both a torque measurement and a damage detection from a single torque sensor.

[0065] It should also be noted that the invention is not limited to the embodiments described above. It will indeed be apparent to those skilled in the art that various modifications can be made to the embodiments described above, in light of the information just disclosed to them.

[0066] In particular, the transmission system could comprise a single gear rather than a gear train.

[0067] In the detailed presentation of the invention given above, the terms used shall not be interpreted as limiting the invention to the embodiments set forth in this description, but shall be interpreted as including all equivalents which can be foreseen by a person skilled in the art by applying their general knowledge to the implementation of the teaching which has just been disclosed to them.

Claims

Demands

1. Transmission system (100) characterized in that it comprises: - a gear or a gear train (102) comprising pinions (PI, P2, P2', P3), of which a pinion, called the measuring pinion (P2, P2'), transmits a torque, called the transmitted torque, the measuring pinion (P2, P2') having an axial force dependent on the transmitted torque; - bearings (RI, R2, R3, R2A, R2B) for guiding the pinions (PI, P2, P2', P3); - a torque sensor (104) designed to provide a measurement signal (S) of the transmitted torque by measuring the axial force;and - a data processing device (106) comprising: • a frequency analysis module (110) designed to analyze a frequency spectrum of the measurement signal (S) of the torque in order to detect at least one damage in the gear or gear train (102) or the bearings (RI, R2, R3, R2A, R2B), and • a low-pass filter (108) of the measurement signal (S) of the torque to obtain an average transmitted torque (C).

2. Transmission system (100) according to claim 1, wherein the low-pass filter (108) is designed to average the measurement signal (S) of the torque over several revolutions of the measuring pinion (P2, P2').

3. Transmission system (100) according to claim 1 or 2, wherein the measuring pinion (P2, P2') has helical teeth, wherein the gear or gear train (102) has a housing (202) relative to which the measuring pinion (P2, P2') is mounted freely in translation, and wherein the torque sensor (104) is designed to follow an axial translation, representative of the axial force, of the measuring pinion (P2, P2') relative to the housing (202) and to provide, as a measurement signal (S) of the torque, a measurement signal of the axial translation representative of the axial force.

4. Transmission system (100) according to claim 3, wherein the torque sensor (104) comprises: - a part (602) mounted to move in translation relative to the housing (202) along the axis of rotation (D) of the measuring pinion (P2, P2'), but fixed in rotation relative to the housing (202), the part (602) being further mounted to move in rotation around the axis of rotation (D) relative to the measuring pinion (P2, P2'), but fixed to the measuring pinion (P2, P2') in translation along the axis of rotation (D); - a flexible membrane (606) fixed to the housing (202) and in contact with one end (608) of the part (602), so that, when the part (602) follows the axial translation of the measuring pinion (P2, P2'), the end (608) deforms the flexible membrane (606); and - a device for measuring a deformation of the flexible membrane (606) caused by the end (608) to provide the measurement signal (S) of the torque.

5. Transmission system (100) according to any one of claims 1 to 4, wherein the frequency analysis module (110) comprises a peak search module (112) designed to detect a frequency of at least one peak in the frequency spectrum of the measurement signal (S) of the torque and a peak analysis module (116) designed to detect damage in the gear or gear train (102) or the bearings (RI, R2, R3, R2A, R2B) from the detected frequency or frequencies.

6. Transmission system (100) according to claim 5, wherein the frequency analysis module (110) comprises a memory (114) in which predetermined frequencies are recorded and wherein the peak analysis module (116) is designed to compare the detected frequency or frequencies with the predetermined frequencies, in order to detect one or more changes among: a shift of one of the predetermined frequencies, an appearance of a frequency with respect to the predetermined frequencies, and a disappearance of one of the predetermined frequencies.

7. Aircraft comprising a transmission system (100) according to any one of claims 1 to 6.

8. Aircraft according to claim 7, further comprising a memory in which the detection of damage is recorded and /

9.

10. or a human-machine interface designed to trigger a visual and / or audible alarm in response to the detection of damage. Aircraft according to claim 7 or 8, further comprising: - a propulsion system, for example a rotary-wing aircraft; and - a turboengine; in which the transmission system (100) connects the turboshaft engine to the propulsion system so that the latter is driven by the turboshaft engine. Data processing method (700) comprising: - a reception (702) of a measurement signal (S) of a torque transmitted by a pinion, called a measuring pinion (P2, P2'), among several pinions (PI, P2, P2', P3) of a gear or a gear train (102), the measurement signal being provided by a torque sensor designed to measure an axial force presented by the measuring pinion (P2, P2') and dependent on the transmitted torque; - an analysis (708) of a frequency spectrum of the measurement signal (S) of the torque, in order to detect damage in the gear or gear train (102) or in the bearings (RI, R2, R3, R2A, R2B) guiding the pinions (PI, P2, P2', P3); and - a low-pass filtering (704) of the measurement signal (S) of the torque to provide an average transmitted torque (C).

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