Method and a system for monitoring a lubricated mechanical system

Abstract

A method and a system for monitoring a mechanical system, the mechanical system including a lubrication system provided with a reservoir containing a lubricating liquid, with a lubrication circuit designed to lubricate the mechanical system, as well as with a particle detection device arranged in the lubrication circuit. The detection device makes it possible, in particular, to count the number of particles flowing through the lubrication circuit and/or the flow rate of the particles. Comparing that number or that flow rate with a first threshold makes it possible to determine a risk of damage affecting the mechanical system and to anticipate the maintenance or reinforced monitoring operations that possibly need to be performed.

Claims

1. A method of monitoring a mechanical system, the mechanical system including a lubrication system provided with: at least one reservoir containing a lubricating liquid; at least one lubrication circuit through which the lubricating liquid flows and which is designed to lubricate the mechanical system, the lubrication circuit(s) including pipes through which the lubricating liquid flows; at least one flow generator for generating a flow of the lubricating liquid and making it possible to feed at least one lubrication circuit with the lubricating liquid; and at least one particle capture device; wherein the method comprises the following steps: measuring at least one first characteristic of detected particles flowing through at least one pipe of a lubrication circuit performed by at least one particle detection device; comparing at least one first characteristic of the detected particles with a first threshold; collecting particles captured by the capture device(s) if at least one first threshold is exceeded; measuring at least one second characteristic of the captured particles; comparing at least one second characteristic of the captured particles with a second threshold; and performing maintenance on the mechanical system if at least one second threshold is exceeded, wherein if the second characteristic(s) of the captured particles is/are less than the second threshold, and at least one second characteristic is greater than a third threshold, the third threshold being less than the second threshold, the method further comprises the following additional steps: analyzing the first characteristic(s) of the detected particles so as to identify whether the lubricating liquid is polluted; cleaning the mechanical system if pollution of the lubricating liquid is identified; and scheduling regular collections of the particles captured by the capture device(s) if no pollution of the lubricating liquid is identified.

2. The method according to claim 1, wherein the method further comprises additional steps performed following the comparison step, if at least one first threshold is exceeded: analyzing the first characteristic(s) of the detected particles so as to identify whether the lubricating liquid is polluted; cleaning the mechanical system if pollution of the lubricating liquid is identified; and scheduling regular collections of the particles captured by the capture device(s) if no pollution of the lubricating liquid is identified.

3. The method according to claim 1, wherein an alarm is triggered after the mechanical system stops if at least one first threshold is exceeded.

4. The method according to claim 1, wherein, during the step of analyzing the first characteristic(s), presence of pollution of the lubricating liquid is identified if a variation over time of a first characteristic of the detected particles is an increasing curve with at least one change of slope, the slope decreasing with increasing time.

5. The method according to claim 1, wherein, during the step of analyzing the first characteristic(s), presence of pollution of the lubricating liquid is identified if a variation over time of a first characteristic of the detected particles includes a first increase over a first time interval, and then a plateau over a second time interval, or indeed if the variation includes a plurality of increases and a plurality of plateaus in succession.

6. The method according to claim 1, wherein, during the step of analyzing the first characteristic(s), no pollution of the lubricating liquid is identified if a variation over time of a first characteristic of the detected particles is constantly increasing in linear manner.

7. The method according to claim 1, wherein, during the step of analyzing the first characteristic(s), no pollution of the lubricating liquid is identified if a variation over time of a first characteristic of the detected particles is an increasing curve with at least one change of slope, the slope increasing with increasing time.

8. The method according to claim 1, wherein, when the mechanical system equips an aircraft, the method further comprises a step of transmitting the first characteristic(s) of the detected particles to a base on the ground in order to perform the step of analyzing the first characteristic(s).

9. The method according to claim 1, wherein a first characteristic of the detected particles is to be chosen from among the number, the size, and the flow rate of the particles, and wherein a second characteristic of the captured particles is to be chosen from among the number, the size, the mass, the material, and the morphology of the particles.

10. The method according to claim 1, wherein the step of measuring at least one first characteristic of detected particles flowing through at least one pipe of a lubrication circuit is limited to metal particles that are detected.

11. The method according to claim 1, wherein the step of measuring at least one first characteristic of detected particles flowing through at least one pipe of a lubrication circuit is limited to metal particles that are detected, and the step of analyzing the first characteristic(s) of the particles that are detected in order to identify whether the lubricating liquid is polluted is limited to the metal particles that are detected.

12. The method according to claim 1, wherein the step of collecting particles captured by the capture device(s) if at least one first threshold is exceeded is limited to the metal particles that are captured.

13. A monitoring system for monitoring a mechanical system, the monitoring system including a lubrication system for lubricating the mechanical system, the lubrication system being provided with: at least one reservoir containing a lubricating liquid; at least one lubrication circuit through which the lubricating liquid flows and which is designed to lubricate the mechanical system, the lubrication circuit(s) including pipes through which the lubricating liquid flows; at least one flow generator for generating a flow of the lubricating liquid and making it possible to feed at least one lubrication circuit with the lubricating liquid; and at least one particle capture device; wherein the monitoring system further includes at least one detection device for detecting particles that is arranged in at least one lubrication circuit as well as at least one computer and an alarm device, the monitoring system being configured to implement the method according to claim 1.

14. The monitoring system according to claim 13, wherein the particle capture device(s) include(s) at least one magnetic plug or at least one electric magnetic plug.

15. The monitoring system according to claim 13, wherein the lubrication system further includes at least one device that can trap the particles, the detection device being arranged upstream from the device(s) that can trap the particles.

16. The monitoring system according to claim 13, wherein at least one particle detection device is inductive, acoustic, or indeed optical.

17. A mechanical system including: rotary elements; elements for transmitting power and for reducing or increasing rotation speed; and the monitoring system; wherein the monitoring system is the monitoring system according to claim 13.

18. The mechanical system according to claim 17, wherein the mechanical system is a power transmission main gearbox of an aircraft.

19. An aircraft including the mechanical system, wherein the mechanical system is the mechanical system according to claim 17.

20. A method of monitoring a mechanical system, the mechanical system including a lubrication system provided with: a reservoir containing a lubricating liquid; a lubrication circuit through which the lubricating liquid flows to lubricate the mechanical system, the lubrication circuit including a pipe through which the lubricating liquid flows; a flow generator for generating a flow of the lubricating liquid to feed the lubrication circuit with the lubricating liquid; and a particle capture device; wherein the method comprises: measuring at least one first characteristic of detected particles flowing through the pipe of the lubrication circuit performed by a particle detection device; comparing at least one first characteristic of the detected particles with a first threshold; collecting particles captured by the capture device(s) if at least one first threshold is exceeded; measuring at least one second characteristic of the captured particles; comparing at least one second characteristic of the captured particles with a second threshold; and performing maintenance on the mechanical system if at least one second threshold is exceeded, wherein if the second characteristic(s) of the captured particles is/are less than the second threshold, and at least one second characteristic is greater than a third threshold, the third threshold being less than the second threshold, the method further comprises: analyzing the first characteristic(s) of the detected particles so as to identify whether the lubricating liquid is polluted; cleaning the mechanical system if pollution of the lubricating liquid is identified; and scheduling regular collections of the particles captured by the capture device(s) if no pollution of the lubricating liquid is identified, the particle detection device arranged in the pipe of each lubrication circuit of the lubrication system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention and its advantages appear in greater detail from the following description of examples given by way of illustration with reference to the accompanying figures, in which:

(2) FIGS. 1 and 2 show examples of mechanical systems; and

(3) FIGS. 3 to 7 show curves representing variations in a first characteristic of detected particles.

DETAILED DESCRIPTION OF THE INVENTION

(4) Elements present in more than one of the figures are given the same references in each of them.

(5) FIGS. 1 and 2 show a mechanical system 1 including a monitoring system 20 for monitoring said mechanical system 1. This mechanical system 1 includes, in particular, a casing 5 and moving mechanical elements 6, in particular rotary elements, such as shafts and bearings, as well as power transmission elements, and elements for reducing or increasing rotation speeds, such as gears and/or gear trains. For example, this mechanical system 1 is a power transmission main gearbox equipping a rotary-wing aircraft.

(6) The monitoring system 20 includes a lubrication system 10, at least one particle detection device 25 arranged in the lubrication system 10, a computer 21, and an alarm device 22.

(7) In the first example of the mechanical system 1, shown in FIG. 1, the lubrication system 10 includes a single lubrication circuit 2, while the second example of the mechanical system 1, shown in FIG. 2, includes two identical lubrication circuits 2. Each lubrication circuit 2 makes it possible simultaneously to lubricate and to cool the moving mechanical elements 6 of the mechanical system 1.

(8) In a manner that is common to these two examples, the lubrication system 10 includes a reservoir 7 formed by a lower portion of the casing 5 of the mechanical system 1 and containing a lubricating liquid 4, such as oil, and a magnetic plug 18 arranged at the bottom of said reservoir 7. Each lubrication circuit 2 of the lubrication system 10 also includes a flow generator 11, such as a pump, a cooling device 13 formed by a heat exchanger, spray nozzles 14, at least one particle capture device 15-19, and pipes 12 interconnecting these various components.

(9) A particle detection device 25 of the monitoring system 20 is also arranged on each lubrication circuit 2 on a duct 12 positioned downstream from the flow generator 11 and upstream from a capture device 15.

(10) The flow generator 11 makes it possible to suck lubricating liquid 4 from the reservoir 7 and to feed said lubricating liquid to each lubrication circuit 2 until it is sprayed onto the moving mechanical elements 6 of the mechanical system 1 via the spray nozzles 14. The cooling device 13 makes it possible to cool the lubricating liquid 4 before it reaches the spray nozzles 14. The cooling device 13 can also temporarily or indeed permanently trap the metal or non-metal particles flowing through the cooling device 13. Some of said particles can subsequently be randomly fed back into the lubrication circuit 2.

(11) Each capture device 15-19 is arranged on a lubrication circuit 2 in order to capture certain particles flowing with the lubricating liquid 4 so as to limit flowing of them through each lubrication circuit 2. A capture device 15-17 may be a mechanical capture device provided with orifices and making it possible to block certain metal or non-metal particles having dimensions greater than or equal to the dimensions of said orifices. A capture device 18, 19 may also be magnetic and be arranged in the lubrication system 4 in order to capture and to retain only the metal particles that go past nearby.

(12) In the example shown in FIG. 1, the single lubrication circuit 2 includes a mechanical capture device 15 formed by a filtration device, e.g. a filter, arranged downstream from the detection device 25 and upstream from the cooling device 13, as well as a magnetic capture device 18 formed by a signaling magnetic plug arranged in the bottom of the reservoir 7. This magnetic capture device 18 is connected to a secondary alarm device 26 that can trigger an alarm whenever a predetermined quantity of metal particles has been captured by the magnetic capture device 18.

(13) An additional capture device 9 is arranged in the reservoir 7. This additional capture device 9 constitutes a particle retention region and comprises two cavities arranged at the bottom of the reservoir 7 and making it possible to trap metal or non-metal particles by gravity. A plug or stopper (not shown in FIG. 1) may be arranged in each cavity for the purpose of collecting the accumulated particles.

(14) In the example shown in FIG. 2, each lubrication circuit 2 includes a plurality of mechanical capture devices 15-17 and two magnetic capture devices 18-19. A first mechanical capture device 17 is, for example, a strainer that is arranged in the reservoir 7, at the end of a pipe 12, namely upstream from the flow generator 11, blocking certain particles and preventing them from entering the lubrication circuit 2. For example, a second mechanical capture device 15 may be constituted by a filter arranged downstream from the detection device 25 and upstream from the cooling device 13. For example, third mechanical capture devices 15 may be constituted by strainers arranged downstream from the cooling device 13 and upstream from respective ones of the spray nozzles 14. In this way, each third capture device 15 protects a spray nozzle 14 while limiting the risk that one or more particles come to obstruct the spray nozzle 14 at least in part.

(15) The two magnetic capture devices 18-19 have a signaling magnetic plug 18 that is identical to the one in the example of FIG. 1, arranged in the bottom of the reservoir 7, and connected to a secondary alarm device 26, as well as a magnetic plug 19 arranged in a wall of the casing 5, near to moving mechanical elements 6. Each magnetic plug 18, 19 makes it possible to capture the metal particles that are situated or that are moving near to it.

(16) The monitoring system 20 makes it possible to monitor the mechanical system 1 by means of each detection device 25 firstly by detecting particles flowing through each lubrication circuit 2 and going past near to the detection device 25, and by simultaneously measuring at least one first characteristic of said detected particles. Then, said at least one first characteristic or the detected particles may be analyzed in order to identify any risk of occurrence of damage or degradation of at least one moving mechanical element 6 of the mechanical system 1.

(17) To this end, the monitoring system 20 may implement a monitoring method 20 for monitoring the mechanical system 1, which method includes the following steps.

(18) Firstly, a step of measuring at least one first characteristic of the particles detected by the detection device 25 is performed. The detection device 25 may be optical or acoustic in order to detect and to measure the metal or non-metal particles flowing with the lubricating liquid 4 and going past near to the detection device 25. The detection device 25 may also be inductive in order to detect and to measure only the metal particles flowing with the lubricating liquid 4 and going past near to the detection device 25. Each first characteristic of the detected particles is representative of a cumulative quantity of particles going past near to the detection device 25.

(19) Then, a step of comparing at least one first characteristic of the particles detected by the detection device 25 with a first threshold is performed by means of the computer 21. For example, a first characteristic of the detected particles may be the number of detected particles, the flow rate of the particles, or the maximum size from among the sizes of the detected particles. Each first characteristic of the detected particles is representative of a cumulative quantity of particles captured by one or more capture devices 15-19. For example, a first threshold corresponding to each first characteristic may be stored in a memory of the computer 21.

(20) After this comparison step and if at least one threshold is exceeded, a step of collecting particles captured by at least one capture device 15-19, or indeed by each capture device 15-19 of a lubrication circuit 2, is performed. Each first threshold is defined to detect such a risk before an alarm is triggered by means of the secondary alarm device 26 connected to the signaling magnetic plug 18.

(21) After inspecting one or more capture devices 15-19, collecting the particles consists in collecting the particles captured by means of at least one capture device 15-19. In this way, the captured particles are removed from said at least one capture device 15-19 for analysis. If only the metal particles captured are to be analyzed, it is necessary to sort the metal particles from the non-metal particles captured by the capture devices 15-17, that sorting being, for example, performed by means of a magnetic device.

(22) Then, a step of measuring said at least one second characteristic of the captured particles is performed by an appropriate device. A second characteristic may be the number and/or the size of the captured particles. As regards the size of the captured particles, the measurement step may be performed manually, e.g. via a graduated precision magnifying glass, or indeed automatically. Each second characteristic of the captured particles is indicative of a cumulative quantity of particles captured by one or more capture devices 15-19.

(23) A step of comparing at least one second characteristic of the captured particles with a second threshold may then be performed by means of a dedicated computer. For example, a second threshold corresponding to each second characteristic may be stored in a memory of the computer 21.

(24) Depending on this comparison, a risk of damage or degradation of a mechanical element 6 of the mechanical system 1 can be identified and a maintenance operation can possibly be performed on the mechanical system 1 so that the presence of said risk of damage or degradation can be confirmed or not confirmed. In this example, whenever a second characteristic is greater than a second threshold, a step of carrying out maintenance on the mechanical system 1 is performed.

(25) The value of a second threshold may be determined by testing, or indeed by feedback from experience. It is known that captured particles of large dimensions are generally indicative of the presence of damage or degradation of the mechanical system, as is a large number of captured particles.

(26) In addition, an alarm may also be triggered by means of the alarm device 22 in order to warn an operative that a first threshold is exceeded and that it is necessary to collect particles captured by one or more capture devices 15-19. This alarm may be triggered whenever a first threshold is exceeded or indeed after the mechanical system has been stopped following the first threshold being exceeded.

(27) Furthermore, comparing at least one first characteristic with a first threshold has made it possible to identify a risk of damage or degradation of a mechanical element 6 of the mechanical system 1 and comparing at least one second characteristic with a second threshold can make it possible to assess whether or not occurrence of such damage or degradation can be established. However, the measurement of said at least one first characteristic may be a first sign that such damage or degradation, of a mechanical element 6 of the mechanical system 1 is in preparation, or it may be consequent upon pollution of the lubricating liquid. A step of analyzing said at least one first characteristic of the detected particles can then make it possible to identify whether pollution of the lubricating liquid 4 is possibly the cause of the measurement of the first characteristic being greater than the first threshold.

(28) Such an analysis step may be performed directly by the computer 21 of the monitoring system 20. Such an analysis step may also be performed outside the monitoring system 20, e.g. by a remote device 30. In which case, the measurement of said at least one first characteristic of the detected particles has to be transferred to the remote device 30, e.g. via a wireless link. The monitoring method 20 for monitoring the mechanical system 1 may then include a step of transmitting said at least one first characteristic of the detected particles to the remote device 30.

(29) When the mechanical system 1 equips an aircraft, the remote device 30 is, for example, a base on the ground, thereby making it possible not to use the computer 21 of the monitoring system 20 for this analysis, in particular if said computer 21 is shared with other devices of the aircraft.

(30) When the mechanical system 1 equips an aircraft, the remote device 30 can also make it possible only to view the curves coming from the analysis step, the aircraft being, for example, still in flight or having landed on the ground. The analysis is then performed by a computer 21 on board the aircraft, e.g. a computer 21 incorporated into the avionics system of the aircraft.

(31) For example, this analysis step may be performed following the comparison of at least one second characteristic of the captured particles with a second threshold if at the same time each second characteristic is less than the second threshold and at least one second characteristic is greater than a third threshold. The third threshold is less than the second threshold.

(32) This analysis step may also be performed after the step of comparing at least one first characteristic of the detected particles with a first threshold and whenever a first threshold is exceeded.

(33) In any event, during this analysis step, pollution of the lubricating liquid 4 may be identified on the basis of the measurement of at least one first characteristic.

(34) The presence of pollution of the lubricating liquid may be identified if variation over time of a first characteristic of the detected particles includes a first increase over a first time interval, then a substantially constant plateau over a second time interval, as shown in FIG. 3, the second time interval following the first time interval.

(35) A variation over time of a first characteristic of the detected particles may also be representative of pollution if a plurality of increases and of substantially constant plateaus succeed one another, as shown in FIG. 4. Such a variation thus takes the characteristic shape of a staircase, i.e. of a step curve.

(36) The presence of pollution of the lubricating liquid may also be identified if variation over time of a first characteristic of the detected metal particles includes a first increase over a first time interval, then a second increase less than said first increase over a second time interval, as shown in FIG. 5, the second time interval following the first time interval.

(37) Conversely, no pollution of the lubricating liquid is identified when a variation over time of a first characteristic of the detected particles constantly increases in linear manner, as shown in FIG. 5.

(38) Similarly, no pollution of the lubricating liquid is identified when a variation over time of a first characteristic of the detected particles includes a first increase over a first time interval, then a second increase greater than the first increase over a second time interval, as shown in FIG. 6. For example, such a variation over time of a first characteristic may be in the shape of a parabolic curve or of an exponential curve.

(39) Following this analysis step, a step of cleaning the mechanical system 1 may be performed if pollution of the lubricating liquid 4 is identified, in particular in order to remove said pollution.

(40) Otherwise if no pollution of the lubricating liquid is identified, a risk of presence of damage or degradation of at least one element of the mechanical system exists and a step of scheduling regular collections of the particles captured by at least one capture device 15-19 may be implemented. In this way, reinforced monitoring of the mechanical system is provided in order to monitor the presence or possible occurrence of damage or degradation of a mechanical element 6.

(41) Naturally, the present invention may be subjected to numerous variations as to its implementation. Although several implementations and embodiments are described above, it should readily be understood that it is not conceivable to identify exhaustively all possible implementations and embodiments. It is naturally possible to envisage replacing any of the means described by equivalent means without going beyond the ambit of the present invention.