Patent ID: 12228083

Before embodiments of a gearbox device30are described in detail, a gearbox device30is described within the technical context of a gas turbine engine10used in connection with an aircraft. It should be pointed out that the gearbox device30itself is not limited to applications in aircraft engines.

FIG.1illustrates a gas turbine engine10having a principal rotational axis9. The engine10comprises an air intake12and a propulsive fan23that generates two airflows: a core airflow A and a bypass airflow B. The gas turbine engine10comprises a core11that receives the core airflow A. The engine core11comprises, in axial flow series, a low pressure compressor14, a high-pressure compressor15, combustion equipment16, a high-pressure turbine17, a low pressure turbine19and a core exhaust nozzle20. A nacelle21surrounds the gas turbine engine10and defines a bypass duct22and a bypass exhaust nozzle18. The bypass airflow B flows through the bypass duct22. The fan23is attached to and driven by the low pressure turbine19via a shaft26and an epicyclic gearbox device30. The gearbox device30not only comprises the details of the gearbox itself, which are described inFIG.1to3, but also ancillary parts which are described inFIGS.4to10.

In use, the core airflow A is accelerated and compressed by the low pressure compressor14and directed into the high pressure compressor15where further compression takes place. The compressed air exhausted from the high pressure compressor15is directed into the combustion equipment16where it is mixed with fuel and the mixture is combusted. The resultant hot combustion products then expand through, and thereby drive, the high pressure and low pressure turbines17,19before being exhausted through the nozzle20to provide some propulsive thrust. The high pressure turbine17drives the high pressure compressor15by a suitable interconnecting shaft27. The fan23generally provides the majority of the propulsive thrust. The epicyclic gearbox device30works as a reduction gearbox.

An exemplary arrangement for a geared fan gas turbine engine10is shown inFIG.2. The low pressure turbine19(seeFIG.1) drives the shaft26, which is coupled to a sun wheel, or sun gear,28of the epicyclic gear arrangement30. Radially outwardly of the sun gear28and intermeshing therewith is a plurality of planet gears32that are coupled together by a planet carrier34. The planet carrier34constrains the planet gears32to process around the sun gear28in synchronicity whilst enabling each planet gear32to rotate about its own axis. The planet carrier34is coupled via linkages36to the fan23in order to drive its rotation about the engine axis9. Radially outwardly of the planet gears32and intermeshing therewith is an annulus or ring gear38that is coupled, via linkages40, to a stationary supporting structure24.

Note that the terms “low pressure turbine” and “low pressure compressor” as used herein may be taken to mean the lowest pressure turbine stages and lowest pressure compressor stages (i.e. not including the fan23) respectively and/or the turbine and compressor stages that are connected together by the interconnecting shaft26with the lowest rotational speed in the engine (i.e. not including the gearbox output shaft that drives the fan23). In some literature, the “low pressure turbine” and “low pressure compressor” referred to herein may alternatively be known as the “intermediate pressure turbine” and “intermediate pressure compressor”. Where such alternative nomenclature is used, the fan23may be referred to as a first, or lowest pressure, compression stage.

The epicyclic gearbox device30is shown by way of example in greater detail inFIG.3. Each of the sun gear28, planet gears32and ring gear38comprise teeth about their periphery to intermesh with the other gears. However, for clarity only exemplary portions of the teeth are illustrated inFIG.3. There are four planet gears32illustrated, although it will be apparent to the skilled reader that more or fewer planet gears32may be provided within the scope of the claimed invention. Practical applications of a planetary epicyclic gearbox device30generally comprise at least three planet gears32.

The epicyclic gearbox device30illustrated by way of example inFIGS.2and3is of the planetary type, in that the planet carrier34is coupled to an output shaft via linkages36, with the ring gear38fixed. However, any other suitable type of epicyclic gearbox device30may be used—

It will be appreciated that the arrangement shown inFIGS.2and3is by way of example only, and various alternatives are within the scope of the present disclosure. Purely by way of example, any suitable arrangement may be used for locating the gearbox device30in the engine10and/or for connecting the gearbox device30to the engine10. By way of further example, the connections (such as the linkages36,40in theFIG.2example) between the gearbox device30and other parts of the engine10(such as the input shaft26, the output shaft and the fixed structure24) may have any desired degree of stiffness or flexibility. By way of further example, any suitable arrangement of the bearings between rotating and stationary parts of the engine (for example between the input and output shafts from the gearbox device30and the fixed structures, such as the gearbox device casing) may be used, and the disclosure is not limited to the exemplary arrangement ofFIG.2.

Accordingly, the present disclosure extends to a gas turbine engine having any arrangement of gearbox styles, support structures, input and output shaft arrangement, and bearing locations.

Optionally, the gearbox device may drive additional and/or alternative components (e.g. the intermediate pressure compressor and/or a booster compressor).

Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. For example, such engines may have an alternative number of compressors and/or turbines and/or an alternative number of interconnecting shafts. By way of further example, the gas turbine engine shown inFIG.1has a split flow nozzle20,22meaning that the flow through the bypass duct22has its own nozzle that is separate to and radially outside the core engine nozzle20. However, this is not limiting, and any aspect of the present disclosure may also apply to engines in which the flow through the bypass duct22and the flow through the core11are mixed, or combined, before (or upstream of) a single nozzle, which may be referred to as a mixed flow nozzle. One or both nozzles (whether mixed or split flow) may have affixed or variable area. Whilst the described example relates to a turbofan engine, the disclosure may apply, for example, to any type of gas turbine engine, such as an open rotor (in which the fan stage is not surrounded by a nacelle) or turboprop engine, for example.

The geometry of the gas turbine engine10, and components thereof, is defined by a conventional axis system, comprising an axial direction (which is aligned with the rotational axis9), a radial direction (in the bottom-to-top direction inFIG.1), and a circumferential direction (perpendicular to the page in theFIG.1view). The axial, radial and circumferential directions are mutually perpendicular.

InFIG.4a schematic cross-section through an embodiment of the gearbox device30is shown. The general rotational axis9is also shown. The gearbox device30comprises a sun gear28, which in the shown embodiment drives the gearbox device30. The input side in the embodiment shown inFIG.4is assumed to be on the left hand side.

Within a rotatable planet carrier34, five planet gears32are coupled with the sun gear28, two of the planet gears32are visible in the sectional view ofFIG.4. In other embodiments more than five or less than five planet gears32can be used. The embodiment shown inFIG.3e.g. has four planet gears32.

Each of the planet gears32is mounted on a bearing device50, which is, in this embodiment, a journal bearing. In other embodiments the bearing50device could be of a different design.

A static ring gear38(see alsoFIG.3) is positioned at the outer rim of the gearbox device30which is connected with other static parts of the gas turbine engine30(see e.g.FIG.1).

The torque transmitted through the gearbox device30exits through the planet carrier34(here on the right hand side of the gearbox device30) and drives e.g. the propulsive fan23(seeFIG.1).

The lubrication of planet gears32and bearing devices50is an important operational issue for any system involving a gearbox device30.

To this effect, the embodiment of the gearbox device30described inFIG.4provides a device60,61,65which allows the collection of lubricant62, in this case oil, exiting a bearing device50and it also allows a reintroduction of the collected lubricant62to a lubrication location L, e.g. at the bearing device50or at a different position at the gearbox device30.

The planetary gearbox device30described in the following is an epicyclic planetary gearbox, which is driven by the sun gear28, having a static ring gear38and a rotatable planet carrier34.

As the planet carrier34is rotating around the axis9during operation, lubricant62is flowing radially outwards from the bearing devices50due to the centrifugal force acting on the planet carrier34. InFIG.4, this is schematically shown as a flow F.

But in this embodiment the flow F is also directed axially outwards, i.e., here towards the input side of the gearbox device30by means which will be described more detailed in embodiments shown inFIGS.5to10.

At the outer rim of the planet carrier34and on its outer axial side, a lubricant reservoir device61is positioned (see alsoFIG.5). This is essentially an L-shaped protrusion extending axially away from the planet carrier34. On the distal end of this protrusion, a section of the lubricant reservoir device61points radially inwards. As best can be seen inFIG.5, the lubricant reservoir device61forms a ring like lubricant collection space (with a part of the planet carrier34forming one wall) which is radially open inwards, i.e. towards the axis9of the gearbox device30.

Due to the centrifugal force acting on the lubricant62, the lubricant62exiting the bearing device50is collected in the ring-like collection space formed by the lubricant reservoir device61. This lubricant collection space extends circumferentially around the outer rim of the planet carrier34.

In other embodiments, the lubricant reservoir device61, and hence the collected lubricant62, is not positioned at the outer rim but some distance inwards from the rim, but still radially outward from the bearing devices50. In the embodiments shown in FIGS.4and5, the lubricant reservoir device61extends around the complete circumference of the gearbox device30. In other embodiments, this does not have to be the case, i.e. the lubrication reservoir device61would only extend over a certain part of the gearbox device30. Since the lubrication reservoir device61is connected to the planet carrier34, it is—under operation—rotating relative e.g. to the stationary ring gear38. Hence, also the lubricant62in the lubricant collecting space is rotating.

The lubricant62is gathered from the lubricant collecting space formed by the lubricant reservoir device61and the planet carrier34by a lubricant scooping device60. In the embodiment shown, the lubricant scooping device60is a static (i.e. static relative to the planet carrier34) tube with an opening pointing in the opposite direction of the rotation of the planet carrier34. In this way, the rotating lubricant62in the collection space is scooped up by the static lubricant scooping device60.

The kinetic energy of the lubricant62is providing sufficient energy to transport the lubricant62into the tube, which is part of a lubricant channel65. The lubricant channel65then radially guides inwards the lubricant62from the radial outer part of the gearbox device30.

As best can be seen inFIG.5, the lubricant channel65is entering the lubricant collection space from underneath the lubricant reservoir device61and transports the lubricant towards a lubrication point L at the bearing device50(best seen inFIG.4).

In the embodiment ofFIG.5, the lubricant62is transferred to a lubrication chamber66in a part attached to the side of the gearbox device30from which the lubricant62can be distributed to the bearing device50and other parts in the gearbox device30. In general, the lubricant62can be transported to other locations in the gearbox device30or into a lubricant chamber66from which it then can be transported to one or more respective users.

InFIG.6, a schematic view onto a lug of the planet carrier34is shown. For reasons of simplicity, only one planet gear32is partially shown, which is driven by the sun gear28(shown only in part) at the center of the planet carrier34. The sun gear28rotates in clockwise direction; consequently, the planet gear32is rotating in counter-clockwise direction. The planet carrier34rotates clockwise. All rotations are indicated by arrows inFIG.6. Radially outwards, a part of the static ring gear38is visible inFIG.6.

At the center of the planet gear32, a journal bearing is located, being the bearing device50.

InFIG.6, the lubricant62is indicated by black dots so that the flow of the lubricant62can be visualized.

On the right-hand side ofFIG.6, the respective planet gear32and the respective bearing device50are not shown. As can be seen by the “lubricant cloud” inFIG.6lubricant62is exiting the gap between the gear shaft (pin) in the direction of the local acting centrifugal force.

InFIGS.6and7(i.e. a sectional view along A-A indicated inFIG.6) flowpaths of the lubricant62are shown.

In one flowpath F1, the lubricant62flows along the pin of the bearing device50(not shown inFIGS.6and7) till it reaches the wall of the planet carrier34. In the embodiment shown inFIG.6it leaves the area around the pin and the planet gear32(both not shown inFIG.6) under an angle of approximately 40°, measured against the local circumference of the pin of the planet gear32. The lubricant flow F1is in a plane parallel to the wall of the planet carrier34and is directed radially outwards towards the radial rim of the planet carrier34. It flows in particular under the influence of the centrifugal force (and to some more less extent the Coriolis force).

Another lubricant62flowpath is shown inFIG.7, as the lubricant exits here at the edge of the planet gear32and is accelerated towards the lug of the planet carrier34. It then follows the centrifugal force. The conversation of momentum when fluid runs over the round transition between carrier side wall and the lug and the Coriolis force causes the flow on the side wall to take an angle that has a certain perpendicular component to the edge of the lug.

The embodiment shown has in particular means for collecting lubricant from those flowpaths as it is shown inFIG.8. to10.

FIG.8shows (in an axial direction of the gearbox device30) a detail of the planet carrier34from of the area around the ring gear38which itself is not visible inFIGS.5and8. This embodiment comprises means to collect lubricant62along the flowpath F1shown inFIG.5.

At the circumference of the pin (not shown inFIG.8) at the location of the flowpath F1of the lubricant62exiting the area under approximately 40° (seeFIG.5) an opening70for the lubricant is positioned. The opening70is essentially a part of a rectangle, which is inclined also approximately by 40° so that it is oriented towards the flow F1to collect it. An inclination of at least 30° has been found to work well.

In other alternatives, the opening70can be a slit or an opening with a curved rim.

The shape of the opening70could deviate from the one shown here, but it is beneficial if it is oriented so that it captures lubricant flowing away from the pin or the planet gear32. The cross-section of the opening70can e.g. be perpendicular to the incoming flowpath F1.

The orientation of the opening70can e.g. be chosen through experiments and/or simulations of the lubricant62dispersion in gearbox device30so that the size and/or shape are altered to maximize the lubricant flow. Simulations show that 30 to 40% of the bearing lubricant can be recovered this way.

InFIG.9a cross-sectional view along the line B-B inFIG.5is shown, i.e. the cross-section is along the axial dimension of the gearbox device30. Here, two openings70for the collection of lubricant62are visible.FIG.10shows a view from the inside of the bearing device50, with the openings70positioned in the wall.

Both openings70are more positioned towards the lateral end of the gearbox device30rather than the middle. An axial bore71extends from one face of the planet carrier39to the other. Therefore, lubricant62collected though the openings70guided towards the outer rims of the ratable planet carrier34. From there, the lubricant62can e.g. be collected by in the lubricant reservoir device61(as shown inFIGS.4and5).

FIG.9also shows some internal channels72which capture lubricant62which is already at the axial ends of the bearing device50. The lubricant62is also channeled towards the lubricant reservoir device61(seeFIG.4or5).

The embodiment of the gearbox device30can be used for geared turbofan engines10, but can also be used in other types of machinery with lubrication users requiring uninterrupted lubrication. The lubricant30is caught in a rotating framework to use the centrifugal force as pump to feed the lubricant back e.g. to the lubrication location L. Through the conversion of the centrifugal force a pressure head is generated, so that the lubricant62is directed back to the journal bearing50with the lubricant channel connecting the static lubricating scooping device60to a static trough and oil jet (it is basically an orifice). In the embodiment shown, there is one static lubricant scooping device61for the whole system, and one lubrication channel65and one static trough and oil jet per journal bearing50.

It is the purpose of this embodiment to maintain a continuous lubrication for the journal bearings50at conditions where the lubricant62feed from the main supply is interrupted. One possible example of an interruption is a negative load on an aircraft or a manoeuvre that results in exposure of the lubricant62off-take in the tank to air (not shown inFIG.4).

The embodiment aims at catching and collecting the lubricant62as it leaves the journal bearing50and uses the centrifugal force to feed the lubricant62back to the lubricant location L, i.e. a user, thus creating a “close lubricant loop” that is in particular not affected by negative g force due to gust or aircraft manoeuvres (in case of aircraft manoeuvres these also include lateral accelerations that could affect the oil pick-up in the oil tank resulting in a similar issue as a transient negative g event).

The embodiment is based on a gearbox architecture with a rotating planet carrier34and a static ring gear38. As the oil exits the journal bearing50it is collected. Features like grooves might be introduced to favour the lubricant as it leaves the journal bearing50to be directed towards the rotating lubricant reservoir device61. In the embodiment, this is arranged on only one side of the journal bearing50, there is little on the opposite side, but in principle the lubricant reservoir device61, the lubricant scooping device60and the lubricant channel65could be positioned on both sides.

It is expected that this embodiment might not be able to catch all the lubricant as it leaves the journal bearing50, but a sufficient amount that could allow the journal bearing50to sustain the transient negative g condition. In case the amount of flow is not sufficient, the solution can be complemented with other features (e.g. oil tank partition, accumulators, etc.).

The embodiment is also able to provide lubricant62flow also during normal operation and in particular during windmill and failure scenarios of the main lubricant feed supply.

The embodiment is self-contained within the gearbox device30and does not require any active components (e.g. valves) and it does not require additional complexity to be added to the rest of the oil system design.

Another advantage is that this solution will provide flow also during in-flight windmill and failure scenarios resulting in a simpler design of some of the oil system components and system solutions (e.g. auxiliary oil system, fault tolerant oil system).

It will be understood that the invention is not limited to the embodiments described above and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.