Triple circuit lubrication device with increased reliability for a main power transmission gearbox of an aircraft

Abstract

A triple circuit lubrication device for lubricating a mechanical system, the lubrication device being provided with two independent lubrication circuits, a tank common to both lubrication circuits and containing a lubrication liquid, and a tertiary circuit in which a tertiary liquid flows. Each lubrication circuit comprises pipes, and respective pressure sensors, pumps, heat exchangers, spray nozzles, and suction points for sucking up the lubrication liquid situated in the tank. The second suction point is situated below the high first suction point. The tertiary circuit comprises a third pump, a third pressure sensor, the second heat exchanger, and a third heat exchanger, thus serving to cool the lubrication liquid flowing through the second lubrication circuit.

Claims

1. A triple circuit lubrication device for lubricating a mechanical system, the lubrication device being provided with a tank and two lubrication circuits, the tank containing a lubrication liquid, a first lubrication circuit comprising a first pump, first pipes, a first pressure sensor, a first heat exchanger, first spray nozzles, and a first suction point for sucking up the lubrication liquid, a second lubrication circuit comprising a second pump, second pipes, a second pressure sensor, a second heat exchanger, second spray nozzles, and a second suction point for sucking up the lubrication liquid, the first and second suction points being situated in the tank, each pump acting via the first and second suction points to deliver the lubrication liquid into the first and second pipes respectively, and then into the first and second spray nozzles in order to lubricate the mechanical system, wherein the triple circuit lubrication device includes a tertiary circuit in which a tertiary liquid flows, the tertiary circuit comprising a third pump, third pipes, a third pressure sensor, the second heat exchanger, and a third heat exchanger, the third pump serving to cause the tertiary liquid to flow through the second heat exchanger and through the third heat exchanger, the second suction point being situated below the first suction point.

2. A lubrication device according to claim 1, wherein the tertiary circuit is a closed circuit.

3. A lubrication device according to claim 1, wherein the tertiary circuit includes a tertiary tank and a third suction point, the third suction point being situated in the tertiary tank, the third pump acting via the third suction point to deliver the tertiary liquid into the third pipes and the second and third heat exchangers.

4. A lubrication device according to claim 1, wherein the lubrication liquid flows in the second lubrication circuit at a second pressure P2, the tertiary liquid flows in the tertiary circuit at a third pressure P3, and the second pressure P2 of the lubrication liquid is strictly greater than the third pressure P3 of the tertiary liquid.

5. A lubrication device according to claim 1, wherein the lubrication liquid flows in the second lubrication circuit at a second pressure P2, the tertiary liquid flows in the tertiary circuit at a third pressure P3, and the second pressure P2 of the lubrication liquid is strictly less than the third pressure P3 of the tertiary liquid.

6. A lubrication device according to claim 1, wherein the second heat exchanger is suitable for being situated inside the mechanical system.

7. A lubrication device according to claim 1, wherein the second heat exchanger is suitable for being situated above the tank.

8. A lubrication device according to claim 1, wherein the second heat exchanger is suitable for being situated against a wall of the tank.

9. A lubrication device according to claim 1, wherein the tertiary circuit includes a tertiary valve and third spray nozzles.

10. A lubrication device according to claim 1, wherein the mechanical system is a main power transmission gearbox of a rotary wing aircraft.

11. A main power transmission gearbox for a rotary wing aircraft, wherein the main power transmission gearbox is provided with a lubrication device according to claim 10, the tank being constituted by a casing of the main power transmission gearbox.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

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

(2) FIGS. 1 and 2 show two embodiments of the triple circuit lubrication device.

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

DETAILED DESCRIPTION OF THE INVENTION

(4) Two embodiments of a triple circuit lubrication device 1, shown in FIGS. 1 and 2, serve to lubricate a mechanical system 3 that comprises in particular rotary elements 5, such as shafts and bearings, and also elements 5 for transmitting power and reducing or increasing speed, such as gears and/or gearing. The mechanical system 3 may for example be a main power transmission gearbox of a rotary wing aircraft.

(5) Each triple circuit lubrication device 1 has a tank 2, two lubrication circuits 10, 20 serving simultaneously to lubricate the mechanical system 3, and a tertiary circuit 30. The tank 2 is formed by a casing of the mechanical system 3 and contains a lubrication liquid.

(6) Each lubrication circuit 10, 20 has a pump 11, 21, a pressure sensor 12, 22, a heat exchanger 13, 23, a filter 15, 25, spray nozzles 14, 24, a suction point 16, 26, and pipes connecting together the various components of each lubrication circuit 10, 20. The suction points 16, 26 are situated in the tank 2. The second suction point 26 is positioned in the bottom of the tank 2, whereas the first suction point 16 is positioned a little below the surface of the lubrication liquid in the tank 2. Thus, the second suction point 26 is positioned below the first suction point 16.

(7) Each pump 11, 21 serves to draw the lubrication liquid from the tank 2 via a suction point 16, 26 and to deliver the lubrication liquid into each lubrication circuit 10, 20. Each heat exchanger 13, 23 serves to cool the lubrication liquid before it reaches the nozzles 14, 24 after passing through the filters 15, 25.

(8) The first heat exchanger 13 is positioned outside the mechanical system 3. The first heat exchanger 13 is an air/liquid heat exchanger serving to cool the lubrication liquid that has been heated by lubricating the mechanical system 3. This air/liquid heat exchanger uses air situated in the proximity of the mechanical system 3. A first ventilation system 18 serves to activate the flow of air sweeping the first heat exchanger 13.

(9) The second heat exchanger 23 is a liquid/liquid heat exchanger. This liquid/liquid heat exchanger serves to cool the lubrication liquid that has been heated by lubricating the mechanical system 3. This liquid/liquid heat exchanger uses a tertiary liquid flowing in the tertiary circuit 30.

(10) The tertiary circuit 30 comprises a third heat exchanger 33, which is an air/liquid heat exchanger. This third heat exchanger 33 is positioned outside the mechanical system 3 and serves to cool the tertiary liquid that has been heated on passing through the second heat exchanger. This air/liquid heat exchanger uses air situated in the proximity of the mechanical system 3. A second ventilation system 38 serves to activate the flow of air sweeping the third heat exchanger 33.

(11) For example, the tertiary liquid may be water, glycol, or indeed oil, whereas the lubrication liquid is oil.

(12) In a first embodiment of the triple circuit lubrication device 1 shown in FIG. 1, the tertiary circuit 30 is a closed circuit and comprises a third pump 31, a third pressure sensor 32, the second heat exchanger 23, the third heat exchanger 33, and third pipes interconnecting the various components of the tertiary circuit 30.

(13) The second heat exchanger 23 is positioned against a wall of the tank 2. As a result, the second pipes of the second lubrication circuit 20 and the components 21, 22, 24, and 25 of the second lubrication circuit 20 (with the exception of the second heat exchanger 23) are all situated inside the mechanical system 3 and above the tank 2.

(14) As a result, any leak appearing in this second lubrication circuit 20 (with the exception of a leak in the second heat exchanger 23) discharges lubrication liquid directly into the tank 2. This applies for example for a leak from the coupling between the second pipes and the second heat exchanger 23. Consequently, there is no loss of lubrication liquid to the outside of the lubrication device 1 as a result of such a leak, and lubrication of the mechanical system 3 is ensured effectively by the two lubrication circuits 10, 20.

(15) The tertiary liquid flows around a closed loop under drive from the third pump 32 through the second heat exchanger 23 where it is heated, thereby cooling the lubrication liquid flowing through the second lubrication circuit 20, and then through the third heat exchanger 23 where it is cooled by air.

(16) Furthermore, the lubrication liquid flows through the second lubrication circuit 20 at a second pressure P2 that is strictly greater than the third pressure P3 of the tertiary liquid flowing in the tertiary circuit 30.

(17) In the event of a leak from the second lubrication circuit 20 in the heat exchanger 23, the lubrication liquid is then discharged into the tertiary circuit 30. The third pressure P3 rises until it becomes equal to the second pressure P2. As a result, the lubrication liquid is not lost to the outside of the triple circuit lubrication device 1.

(18) Furthermore, since the tertiary circuit 30 is a closed circuit, the quantity of lubrication liquid that is discharged into the tertiary circuit 30 remains limited. Consequently, the level of lubrication liquid remains substantially unchanged in the tank 2.

(19) In addition, the mixture constituted by the lubrication liquid and the tertiary liquid flowing in the tertiary circuit 30 passes through the third heat exchanger 33 and is thus cooled. Consequently, the lubrication liquid flowing through the second lubrication circuit 20 is also cooled in the second heat exchanger 23 by means of this mixture.

(20) The mechanical system 3 is thus lubricated effectively by the first lubrication circuit 10 and the second lubrication circuit 20, without duration being limited, and in spite of the presence of the leak in the second heat exchanger 23.

(21) In a second embodiment of the triple circuit lubrication device 1, as shown in FIG. 2, the tertiary circuit 30 is an open circuit and comprises a third pump 31, a tertiary tank 37, a third pressure sensor 32, the second heat exchanger 23, a third heat exchanger 33, a third suction point 36, and third pipes connecting together the various components of the tertiary circuit 30. The tertiary circuit 30 also has a tertiary valve 35 and third spray nozzles 34.

(22) The second heat exchanger 23 is positioned inside the mechanical system 3 and above the tank 2. As a result, the second pipes of the second lubrication circuit 20, together with all of the components 21, 22, 23, 24, and 25 of this second lubrication circuit 20 are situated inside the mechanical system 3 and above the tank 2.

(23) As in the first embodiment of the lubrication device 1, any leak that appears in the second lubrication circuit 20 (except for a leak in the second heat exchanger 23) discharges lubrication liquid directly into the tank 2. Consequently, there is no loss of lubrication liquid to the outside of the lubrication device 1 as a result of this leak, and the mechanical system 3 continues to be lubricated effectively by the two lubrication circuits 10 and 20.

(24) The tertiary liquid is drawn by the third pump 32 from the tertiary tank 37, and then flows through the second heat exchanger 23 where it is heated, thereby cooling the lubrication liquid flowing through the second lubrication circuit 20, and then through the third heat exchanger 33 where it is cooled by air, and finally returned to the tertiary tank 37.

(25) Furthermore, the lubrication liquid flows in the second lubrication circuit 20 with a second pressure P2 that is strictly less than the third pressure P3 of the tertiary liquid flowing in the tertiary circuit 30.

(26) In the event of a leak from the second lubrication circuit 20 in the heat exchanger 23, the tertiary liquid then discharges into the second lubrication circuit 20. Consequently, all of the tertiary liquid will thus become discharged into the second lubrication circuit 20 and then into the tank 2. The tank 2 thus contains a mixture constituted by the lubrication liquid and by the tertiary liquid.

(27) The lubrication liquid continues to flow in the second circuit 20, passes through the second heat exchanger 23 and reaches the nozzles 24 so as to lubricate the mechanical system 3. However there is no longer any tertiary liquid in the tertiary circuit 30. Consequently, the lubrication liquid is no longer cooled in the second heat exchanger 23. The lubrication performed by the second lubrication circuit 20 is thus not effective.

(28) Following the occurrence of this leak in the second heat exchanger 23, the mechanical system 3 is thus lubricated effectively only by the first lubrication circuit 10.

(29) It is then appropriate to reduce stress on the mechanical system 3, since the lubrication of this mechanical system 3 is reduced.

(30) Furthermore, the tertiary circuit 30 also acts as an emergency lubrication circuit following a drop in the pressure in the two lubrication circuits 10, 20. In the event of such a pressure drop in the two lubrication circuits 10, 20, the tertiary valve 35 is opened so as to allow the tertiary liquid flowing in the tertiary circuit 30 to reach the nozzles 34 and lubricate the mechanical system 3. However, this lubrication can take place for a limited duration only, depending on the quantity of tertiary liquid contained in the tertiary tank 37.

(31) Under such circumstances, the mechanical system 3 needs to be stopped quickly in order to avoid suffering degradation when it is no longer lubricated.

(32) When a leak appears in the tertiary circuit 30, whether in the first embodiment or the second embodiment of the triple circuit lubrication device 1, the tertiary liquid is discharged to the outside of the triple circuit lubrication device 1 and of the mechanical system 3. The tertiary circuit 30 thus becomes completely emptied of the tertiary liquid as a result of this leak. The lubrication liquid in the second lubrication circuit 20 is then no longer cooled in the second heat exchanger 23.

(33) The mechanical system 3 is then lubricated effectively only by the first lubrication circuit 10 as a result of there being a leak in the tertiary circuit 30. It is then appropriate to reduce stress on the mechanical system 3 since the lubrication of the mechanical system 3 is reduced.

(34) Likewise, when a leak appears in the first lubrication circuit 10, and regardless of whether it is in the first or the second embodiment of the triple circuit lubrication device 1, the lubrication liquid flowing in the first lubrication circuit 10 is then discharged to the outside of the triple circuit lubrication device 1 and of the mechanical system 3. The level of lubrication liquid present in the tank 2 decreases, and as soon as it drops below the level of the first suction point 16, the first pump 11 is unprimed and the flow of lubrication liquid through the first lubrication circuit 10 is stopped as a result of the leak. The mechanical system 3 is then no longer lubricated by the first lubrication circuit 10.

(35) The mechanical system 3 is thus lubricated effectively solely by the second lubrication circuit 20 as a result of the presence of this leak from the first lubrication circuit 10. It is then appropriate to reduce stress on the mechanical system 3, since lubrication of the mechanical system 3 reduced.

(36) This triple circuit lubrication device 1 thus makes it possible to propose a system with increased reliability for lubricating a mechanical system 3. This triple circuit lubrication device 1 serves to ensure that the lubrication liquid is cooled continuously and that there is no limitation on the duration of lubrication after a leak is detected, except for the exceptional situation of there being a leak simultaneously from both lubrication circuits 10 and 20.

(37) Naturally, the present invention may be subjected to numerous variations as to its implementation. Although several embodiments are described, it will readily be understood that it is not conceivable to identify exhaustively all possible 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.