Power transmission gearbox and an aircraft

Abstract

A power transmission gearbox provided with at least one lubrication system including a lubrication pump. The lubrication pump is in fluid flow communication with a fluid flow circuit leading to at least one spray means. The gearbox includes an emergency tank suitable for containing a lubrication fluid, the emergency tank being in fluid flow communication with the fluid flow circuit, the emergency tank being connected by at least one pipe to the fluid flow circuit upstream from each spray means, the lubrication fluid being moved in the fluid flow circuit to each spray means by a gas that is set into motion by the lubrication pump in the event of a leak of the lubrication liquid.

Claims

1. A power transmission gearbox having at least one lubrication system, the lubrication system including a lubrication pump that is arranged in a sump containing a lubrication liquid, the lubrication pump being in fluid flow communication with a fluid flow circuit leading to at least one spray means directed towards an internal space of a casing of the gearbox, the lubrication liquid being drawn from the sump by the lubrication pump in order to flow in the fluid flow circuit and be sprayed into the internal space by each spray means, wherein the gearbox includes an emergency tank suitable for containing a lubrication fluid, the emergency tank being in fluid flow communication with the fluid flow circuit, the emergency tank being connected by at least one pipe to the fluid flow circuit upstream from each spray means, the lubrication fluid being moved in the fluid flow circuit to each spray means by a gas that is set into motion by the lubrication pump in the event of a leak of the lubrication liquid.

2. A gearbox according to claim 1, wherein the gearbox includes two lubrication systems.

3. A gearbox according to claim 1, wherein the emergency tank is located above the fluid flow circuit.

4. A gearbox according to claim 1, wherein the emergency tank includes a movable divider dividing the emergency tank into a pressurized volume that does not receive a lubrication fluid and a volume that receives the lubrication fluid.

5. A gearbox according to claim 1, wherein in the absence of a leak of the lubrication liquid, the lubrication pump pressurizes the lubrication liquid to a pressure greater than or equal to 1.5 bars, the lubrication pump entraining the gas in the fluid flow circuit at a pressure of 1.05 bars following a leak of the lubrication liquid.

6. A gearbox according to claim 1, wherein the emergency tank is connected to the fluid flow circuit by at least one pipe referred to as outlet pipe that leads to a duct of the fluid flow circuit.

7. A gearbox according to claim 1, wherein the emergency tank is connected to the fluid flow circuit by at least one pipe referred to as outlet pipe, the outlet pipe having an end provided with a converging nozzle that is arranged within a duct of the fluid flow circuit.

8. A gearbox according to claim 1, wherein the emergency tank is filled by the fluid flow circuit in the absence of a leak of the lubrication liquid, the fraction of the lubrication liquid that fills the emergency tank representing the lubrication fluid.

9. A gearbox according to claim 8, wherein the emergency tank is connected to the fluid flow circuit by at least one pipe referred to as inlet pipe, the inlet pipe being a one-way connection enabling a fluid to flow solely from the fluid flow circuit towards the emergency tank.

10. A gearbox according to claim 1, wherein the emergency tank is connected to the fluid flow circuit by a pipe referred to as inlet pipe in order to be filled by the fluid flow circuit in the absence of a leak of the lubrication liquid, the emergency tank being connected to the fluid flow circuit by an outlet pipe in order to transfer a lubrication fluid to the fluid flow circuit, the outlet pipe presenting a minimum diameter that is smaller than a minimum diameter of the inlet pipe.

11. A gearbox according to claim 7, wherein the emergency tank is connected to the fluid flow circuit solely by an outlet pipe, the lubrication fluid being distinct from the lubrication liquid.

12. A gearbox according to claim 1, wherein the emergency tank is connected to the fluid flow circuit by a pipe provided with a valve.

13. A gearbox according to claim 11, wherein the valve is controlled by a manual control operable by a pilot.

14. A gearbox according to claim 12, wherein the valve is connected to at least one pressure sensor measuring a pressure in the fluid flow circuit.

15. A gearbox according to claim 12, wherein the valve is connected to at least one temperature sensor measuring a temperature in the internal space, the valve opening when the temperature becomes higher than a temperature threshold.

16. A gearbox according to claim 1, wherein the emergency tank is independent of the sump and arranged outside the casing.

17. An aircraft, wherein the aircraft includes a power transmission gearbox according to claim 1.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

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

(2) FIG. 1 is a diagram showing an aircraft of the invention, the aircraft including a power transmission gearbox;

(3) FIG. 2 is a diagram showing an outlet pipe including a convergent nozzle;

(4) FIGS. 3 to 5 are diagrams explaining the operation of a lubrication system comprising a tank fed with fluid by the fluid flow circuit of the lubrication circuit; and

(5) FIG. 6 is a diagram explaining the operation of a lubrication system comprising a tank having its own supply of fluid.

DETAILED DESCRIPTION OF THE INVENTION

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

(7) FIG. 1 shows an aircraft 1 of the invention. The aircraft 1 has a rotor 3. Such a rotor 3 may be a rotor that contributes at least in part to providing the aircraft 1 with lift and/or propulsion.

(8) In order to set the rotor 3 into motion, the aircraft has at least one engine 2 and a power transmission gearbox 5.

(9) Under such circumstances, the gearbox 5 comprises transmission members that rotate within a casing 10.

(10) Thus, inside the casing 10, the gearbox 5 includes a drive wheel 11 setting at least one speed reduction stage 15 into motion. For example, the speed reduction stage 15 may have a sunwheel 16 constrained to rotate with the drive wheel 11 by a power transmission shaft. The sunwheel 16 meshes with at least one planet wheel 17 that slides along a peripheral ring 18. Each planet wheel 17 is also carried by a planet carrier 19. The planet carrier 19 may be mechanically connected to the rotor 3 for driving as shown in FIG. 1, or indeed it may be connected to another speed reduction stage.

(11) The drive wheel 11 may also be driven indirectly in rotation about an axis of rotation by each engine. Thus, the gearbox may be provided with a respective mechanical inlet member 12 for each engine. Each mechanical inlet member 12 has at least one wheel 12 that meshes with the drive wheel 11.

(12) Furthermore, the gearbox 5 has at least one lubrication system 20 for lubricating the movable members of the gearbox 5. Optionally, the gearbox 5 may be provided with two lubrication systems 20 that may be identical or different.

(13) Each lubrication system 20 includes a lubrication pump 25. The lubrication pump 25 may be driven by a wheel 13, the wheel 13 optionally being constrained to rotate with the drive wheel 11.

(14) Under such circumstances, the lubrication pump 25 draws lubrication liquid 100 from a sump 26 of the gearbox. Conventionally, the lubrication liquid may comprise oil. Reference may be made to the literature in order to obtain information about lubrication liquids.

(15) The sump 26 may comprise the bottom of the casing 10 of the gearbox 5. Thus, a lubrication liquid injected into a internal space INT of the casing 10 drops into the sump 26 by gravity.

(16) Furthermore, each lubrication system 20 includes a fluid flow communication 30 in fluid flow communication with the lubrication pump 25. The lubrication pump is thus dimensioned so as to cause the lubrication liquid to flow in the fluid flow circuit 30.

(17) The fluid flow circuit leads to at least one spray means 40 directed towards the internal space INT of a casing. Each spray means 40 may comprise conventional means, such as an orifice 41 or a nozzle (not shown), by way of example.

(18) The fluid flow circuit includes at least one duct 31, 32, 33. The term duct should be interpreted broadly, a duct possibly comprising a plurality of individual pieces of pipework connected end to end.

(19) The fluid flow circuit may be virtually subdivided into an upstream duct 31 connected to the lubrication pump 25, a central duct 32 connected to the upstream duct 31, and a downstream duct 33 for each spray means 40. The upstream duct 31 may optionally co-operate with a heat exchanger 35.

(20) In the absence of a leak of lubrication liquid, such as a leak from the sump 26, lubrication liquid 100 is drawn from the sump 26 by the lubrication pump 25. The lubrication liquid then flows in the fluid flow circuit 30 so as to end up being sprayed into the internal space INT by each spray means 40.

(21) In order to lubricate this internal space following a leak of lubrication liquid 100, at least one, and possibly each, lubrication system 20 includes an additional emergency tank 50.

(22) The emergency tank 50 of a lubrication system 20 is arranged in parallel with the fluid flow circuit of the lubrication system 20.

(23) The emergency tank comprises a shell 51 containing a lubrication fluid 200. The lubrication fluid 200 may comprise oil.

(24) The emergency tank 50 is independent of the sump 26. Consequently, the emergency tank represents a container that is distinct from the sump 26.

(25) Furthermore, the emergency tank may be arranged outside the casing 10 that contains the rotary members of the gearbox.

(26) This emergency tank 50 is then in fluid flow communication with the fluid flow circuit 30 upstream from the spray means 40, i.e. by way of example, upstream from the downstream duct 33. Under such circumstances, the emergency tank may be in fluid flow communication with the central duct 32.

(27) For this purpose, the emergency tank 50 has at least one pipe 60 extending from the shell 51 to the fluid flow circuit 30.

(28) FIG. 1 shows two emergency tanks 50, respectively in a first embodiment and in a second embodiment.

(29) Whatever the embodiment, the emergency tank is thus connected by at least one outlet pipe 61 to the fluid flow circuit.

(30) The outlet pipe serves in particular to enable the lubrication fluid 200 to reach the fluid flow circuit 30. To facilitate this movement, an emergency tank 50 may be located above the corresponding fluid flow circuit 30 in order to enable the lubrication fluid 200 to flow under gravity.

(31) The outlet pipe 61 then leads to a duct of the fluid flow circuit, and in particular to the central duct as shown in FIG. 1.

(32) In the variant of FIG. 1, an outlet pipe 61 has an orifice 61 opening out into the fluid flow circuit. Furthermore, the outlet pipe may include a constriction 64, in particular for encouraging flow of the drop-by-drop type.

(33) In the variant of FIG. 2, an outlet pipe has an end provided with a converging nozzle 65 that is arranged in the fluid flow circuit. For example, the converging nozzle 65 is arranged in the middle of a duct of the fluid flow circuit.

(34) Furthermore, and with reference to FIG. 1, a pipe from an emergency tank may be fitted with a valve 70.

(35) In particular, an outlet pipe 61 may include such a valve 70 to enable lubrication fluid to flow only under predetermined conditions.

(36) A valve 70 may be controlled by a manual control 72 operable by a pilot.

(37) In addition, a valve 70 may be controlled as a function of a pressure that exists in the fluid flow circuit. The valve 70 is then connected to at least one pressure sensor 71 measuring a pressure in the fluid flow circuit 30. Said valve 70 may optionally open when the measured pressure becomes lower than a pressure threshold.

(38) A valve 70 may also be controlled by a temperature that exists in the internal space INT of the gearbox. The valve 70 is then connected to at least one temperature sensor 73 measuring a temperature in the internal space INT, said valve opening when said temperature becomes higher than a temperature threshold.

(39) Furthermore, an emergency tank may include a divider 55. By way of example, such a divider 55 presents a piston or a diaphragm separating the emergency tank 50 into a pressurized volume 56 that does not contain lubrication fluid 200 and a lubricant volume 57 that contains the lubrication fluid 200. The pressurized volume 56 may, by way of example, contain a gas that is injected by an operator at a predetermined pressure.

(40) The pressure that exists in the lubricant volume 57 is lower than the pressure of the lubrication liquid in the fluid flow circuit.

(41) In a first embodiment illustrated by the lubrication system 20 shown on the left in FIG. 1, the emergency tank is filled by the fluid flow circuit 30.

(42) In the absence of a leak of lubrication liquid, a fraction of the lubrication liquid fills the emergency tank. The lubrication fluid 200 thus represents a fraction of the lubrication liquid 100.

(43) The outlet pipe can enable the lubrication liquid to be conveyed to the emergency tank in a first alternative that is not shown.

(44) Nevertheless, in a second alternative as shown in FIG. 1, the emergency tank includes an inlet pipe 62 in order to enable it to be filled by the fluid flow circuit.

(45) The inlet pipe 62 is situated upstream from the outlet pipe 61. The inlet pipe also extends from the fluid flow circuit and, in particular, from the central duct 32, to the shell 51 of the emergency tank 50.

(46) This inlet pipe 62 may be a one-way connection enabling lubrication liquid to flow solely from the fluid flow circuit 30 to the emergency tank 50.

(47) Consequently, the inlet pipe may include a check valve 63.

(48) In addition, the inlet pipe 62 and the outlet pipe 61 may present different dimensions. The outlet pipe 61 thus presents a minimum diameter D1 that is less than a minimum diameter D2 of the inlet pipe 62.

(49) The emergency tank in the first embodiment shown in FIG. 1 has a valve 70. Nevertheless, such a valve is optional, and in particular it is shown in FIGS. 3 to 5.

(50) In a second embodiment illustrated by the lubrication system 20 arranged on the right in FIG. 1, the emergency tank is not filled by the fluid flow circuit 30.

(51) The emergency tank 50 is connected to the fluid flow circuit 30 solely by an outlet pipe 61.

(52) Furthermore, the lubrication fluid 200 is distinct from the lubrication liquid 100. The term is distinct from the lubrication liquid 100 means that the lubrication fluid is not a portion of the lubrication liquid. The lubrication fluid is introduced into the emergency tank 50 by an operator.

(53) Nevertheless, the lubrication fluid and the lubrication liquid may be fluids that are different or identical.

(54) The outlet pipe may be provided with a valve of the type described above.

(55) Independently of the way the emergency tank is embodied, the lubrication system does not have a compressor external to the gearbox.

(56) Specifically, in the event of a leak of lubrication liquid, the lubrication fluid 200 contained in an emergency tank is caused to move in the fluid flow circuit 30 towards each of the spray means 40 by a gas. In the event of a leak of the lubrication liquid, the sump 26 becomes filled with a gas, such as air. This gas is then set into motion by the lubrication pump 25 in the fluid flow circuit and it mixes with the lubrication fluid, in order to enable the lubrication fluid to be delivered into the internal space INT by the spray means 40.

(57) The invention therefore does not need an additional air compressor.

(58) FIGS. 3 to 5 show the operation of the invention with an emergency tank of the first embodiment.

(59) With reference to FIG. 3, the emergency tank is empty prior to starting the gearbox.

(60) With reference to FIG. 4, while the gearbox is set into motion by at least one engine, the lubrication pump is in operation.

(61) This lubrication pump causes the lubrication liquid 100 to flow in the fluid flow circuit 30. The lubrication pump can then pressurize the lubrication liquid 100 in the fluid flow circuit to a pressure greater than or equal to 1.5 bars, where one bar is equal to 101,300 pascals (Pa).

(62) When the lubrication liquid 100 reaches the central duct 32, a fraction of this lubrication liquid 100 passes along the inlet pipe 62 so as to reach the emergency tank 50.

(63) Since the outlet pipe 61 has a minimum diameter that is less than the minimum diameter of the inlet pipe 62, a fraction of the lubrication liquid remains in the emergency tank so as to constitute a supply of lubrication fluid 200. Optionally, a valve may be arranged on the outlet pipe in order to enable the emergency tank to be filled.

(64) The level of lubrication fluid thus rises in the emergency tank. The emergency tank therefore becomes filled passively.

(65) When used, a divider 55 serves to define a gas pressurized volume 56 in the emergency tank in order to maintain the lubrication fluid under a predetermined pressure. For example, the lubrication fluid may be maintained at a pressure lying in the range 1.1 bars to 1.5 bars.

(66) Optionally, a fraction of the lubrication fluid flows in the fluid flow circuit without having any influence on the operation of the fluid flow circuit.

(67) When the gearbox is stopped, the lubrication fluid flows under gravity into the fluid flow circuit, with the emergency tank returning to the state shown in FIG. 3.

(68) In the event of a leak of lubrication liquid, and with reference to FIG. 3, the lubrication pump causes a gas 300 to flow in the fluid flow circuit. This gas presents a pressure of less than 1.5 bars. In particular, the pressure of the gas is less than the pressure in the pressurized volume, e.g. reaching a pressure of about 1.05 bars.

(69) In the variant of FIG. 5, the lubrication fluid flows under gravity into the outlet pipe 61, and then flows in drop-by-drop form in the fluid flow circuit.

(70) In the variant of FIG. 2, the lubrication fluid escapes from the converging nozzle 65 by the Venturi effect.

(71) The mixture of gas and lubrication fluid is then directed towards the spray means which produce a mist of lubrication fluid inside the casing of the gearbox.

(72) In the second embodiment shown in FIG. 6, in the presence of a leak of the lubrication liquid, the lubrication pump causes a gas 300 to flow in the fluid flow circuit.

(73) In addition, the valve 70 opens. The lubrication fluid then flows under gravity along the outlet pipe 61 so as to be mixed with the gas 300.

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