SHAFT ASSEMBLY AND AIRCRAFT ENGINE WITH A SHAFT ASSEMBLY

Abstract

A shaft arrangement with two concentrically arranged shafts, in particular two concentric hollow shafts that are coupled to the drive side or the output side of an engine, wherein the shafts respectively have envelope elements that are connected to at least one elastically bending connection element, wherein the torque transmission between the concentric shafts is effected by tensile forces in the elastically bending envelope elements. The invention also relates to an aircraft engine with such a shaft arrangement.

Claims

1. A shaft arrangement with two concentrically arranged shafts, in particular two concentric hollow shafts that are coupled to the drive side or output side of an engine, wherein the shafts respectively have envelope elements that are connected with at least one elastically bending connection element, wherein the torque transmission between the concentric shafts is effected by tensile forces in the elastically bending envelope elements.

2. The shaft arrangement according to claim 1, wherein the at least one elastically bending connection element is formed as a rope, in particular a wire rope, as a chain or as a strap.

3. The shaft arrangement according to claim 1, wherein the at least one elastically bending connection element is formed in a ring-shaped, that is, infinite manner.

4. The shaft arrangement according to claim 1, wherein the at least one elastically bending connection element is guided around and/or wound around the envelope elements for connecting the shafts.

5. The shaft arrangement according to claim 1, wherein the at least one elastically bending connection element is arranged around the envelope elements without being crossed with itself or with other elastically bending connection elements.

6. The shaft arrangement according to claim 1, wherein, for connecting the concentric shafts, the at least one elastically bending connection element, in particular in the loaded state, is arranged in a plane that is located perpendicular to the rotational axis of the two concentric shafts.

7. The shaft arrangement according to claim 1, wherein the at least one connection element is affixed at an envelope element at maximally one position.

8. The shaft arrangement according to claim 1, wherein the envelope elements are arranged at the concentric shafts in such a manner that the at least one elastically bending connection element connected thereto is arranged in a plane that is perpendicular to the rotational axis of the two concentric shafts.

9. The shaft arrangement according to claim 1, wherein the envelope elements are arranged as projections at least at one of the concentric shafts in the axial direction, wherein the projections are in particular formed in one piece at the shaft ends.

10. The shaft arrangement according to claim 1, wherein the envelope elements of the at least one concentric shaft are formed at least partially by openings, in particular by pairs of openings, in particular by openings in concentric hollow shafts.

11. The shaft arrangement according to claim 1, wherein the at least one elastically bending connection element is formed as a mechanical securing device against overloading in order to protect the gear against blocking.

12. The shaft arrangement according to claim 1, wherein at least two elastically bending connection elements are arranged so as to be axially offset with respect to one another, wherein the at least two elastically bending connection elements in particular have different tensile strains.

13. The shaft arrangement according to claim 1, wherein between 5 and 30 envelope elements, in particular 10 envelope elements, are arranged at the concentric shafts at the circumference or at the shaft end.

14. The shaft arrangement according to claim 1, wherein the shaft arrangement mechanically connects two concentric shafts on the output side of an engine, in particular of a planetary gear, of a turbofan drive.

15. The shaft arrangement according to claim 1, wherein the shaft arrangement mechanically connects two concentric shafts on the drive side of an engine, in particular of a planetary gear, of a turbofan drive.

16. The shaft arrangement according to claim 1, wherein the envelope elements have a means for axially affixing the at least one elastically bending connection element.

17. The shaft arrangement according to claim 1, wherein the at least one elastically bending connection element and/or the envelope elements have a low-friction coating.

18. The shaft arrangement according to claim 1, wherein the envelope elements have at least one slide bearing.

19. The shaft arrangement according to claim 1, wherein the at least one elastically bending connecting means is formed as a wire rope, wherein the wire rope has a diameter of between 5 and 25 mm, in particular of between 10 and 20 mm.

20. An aircraft engine with a core engine, comprising a turbine, a compressor and a core engine shaft for connecting the turbine to the compressor, a fan upstream of the core engine, wherein the fan has a plurality of blades, and a planetary gear that is connected to the core engine shaft on the entry side, and is connected to the fan on the exit side to the drive in such a manner that the rotational speed of the fan is lower than the rotational speed of the core engine shaft, and with a shaft arrangement having the features of claim 1.

Description

[0055] Exemplary embodiments are described in connection with Figures, herein:

[0056] FIG. 1 shows a lateral sectional view of a gear fan engine;

[0057] FIG. 2 shows an enlarged view of a lateral sectional view of the front part of the engine according to FIG. 1;

[0058] FIG. 3 shows a schematic view of a planetary carrier for planetary wheels;

[0059] FIG. 4 shows a schematic lateral sectional view through two shafts that are connected to an elastically bending connection element on the drive or output side of an engine;

[0060] FIG. 5 shows a schematic top view on the elastically bending connection element and the envelope elements establishing the connection between the two shafts;

[0061] FIG. 6 shows a perspective view of a shaft end with the envelope elements for the flexible connection element;

[0062] FIG. 7 shows a schematic rendering of a further embodiment of a shaft arrangement;

[0063] FIG. 8 shows a schematic rendering of a further embodiment with two elastically bending connecting means that are arranged in parallel.

[0064] FIG. 1 describes an aircraft engine 10 having a main rotational axis 9. The engine 10 comprises an air intake 12 and a fan 23 that generates two airflows: a core airflow A through a core engine 11 and a bypass airflow B.

[0065] The core engine 11 comprises, as viewed in the axial flow direction, a low pressure compressor 14, a high pressure compressor 15, combustion device 16, a high pressure turbine 17, a low pressure turbine 19 and a core engine exhaust nozzle 20. A nacelle 21 surrounds the aircraft engine 10 and defines the bypass duct 22 (also referred to as the subsidiary flow duct) and a bypass exhaust nozzle 18. The bypass airflow B flows through the bypass duct 22. The fan is driven by the low pressure turbine 19 via the shaft 26 and a planetary gear 30.

[0066] During operation, the airflow A in the core engine 11 is accelerated and compressed by the low pressure compressor 14, wherein it is directed into the high pressure compressor 15 where further compression takes place. The air that is discharged from the high pressure compressor 15 in a compressed state is directed into the combustion device 16 where it is mixed with fuel and combusted.

[0067] The resulting hot combustion gases are guided through the high pressure turbine 17 and the low pressure turbine 19, which are driven by the combustion gasses. Subsequently, the combustion gasses are discharged through the core exhaust nozzle 20 and provide a portion of the total thrust. The high pressure turbine 18 drives the high pressure compressor 15 via a suitable interconnecting shaft 27. The fan 23 usually provides the greatest portion of the propulsive thrust. In the present case, the planetary gear 30 is embodied as a reduction gear to reduce the rotational speed of the fan 23 as compared to the driving turbine.

[0068] An exemplary arrangement for a geared fan arrangement of an aircraft engine is shown in FIG. 2.

[0069] The low pressure turbine 19 (see FIG. 1) drives the shaft 26, which is coupled to a sun gear 28 of the planetary gear 30. Located radially outwardly of the sun gear 28 and intermeshing therewith is a plurality of planetary wheels 32 that are coupled with each other by a planet carrier 34. The planet carrier 34 forces the planetary wheels 32 to precess around the sun gear 28 synchronously whilst enabling each planetary wheel 32 to rotate about its own axis. Via connections 36, the planet carrier 34 is coupled to the fan 23 in order to cause its rotation about the rotational axis 9. An annulus or ring gear 38 is connected radially outside of the planetary wheels 32 and intermeshing therewith, and connected via connections 40 to a stationary supporting structure 24. This structural design represents an epicyclic planetary gear 30.

[0070] Note that the terms low pressure turbine and low pressure compressor as used herein may be taken to refer to the turbine stages with the lowest pressure and the compressor stages with the lowest pressure (i.e., not including the fan 23) and/or refer to the turbine and compressor stages that are connected by the interconnecting shaft 26 with the lowest rotational speed in the engine 10 (i.e., not including the gearbox output shaft that drives the fan 23). A low pressure turbine and a low pressure compressor referred to herein may alternatively also refer to an intermediate pressure turbine and an intermediate pressure compressor. Where such alternative nomenclature is used, the fan 23 may be referred to as a first or lowest pressure stage.

[0071] The planetary gear 30 is shown by way of example in greater detail in FIG. 3, wherein some of the features will be discussed in more detail in connection with the embodiments described herein. The sun gear 28, planetary wheels 32 and the ring gear 38 respectively have teeth at their circumference to intermesh with the other gears. However, for reasons of clarity only exemplary portions of the teeth are illustrated in FIG. 3. Here, four planetary wheels 32 are illustrated, although it will be apparent to the person skilled in the art that more or fewer planetary wheels 32 may be provided within the scope of the claimed invention. Practical applications of a planetary epicyclic gearbox 30 generally comprise at least three planetary wheels 32.

[0072] The planetary gear 30 illustrated by way of example in FIGS. 2 and 3 is an epicyclic planetary gear since the planetary carrier 34 is connected in a rotatable manner, i.e. above all in a drivable manner, to the fan 23 via a shaft.

[0073] However, it is also possible to use any other suitable type of a planetary gear 30.

[0074] By way of further example, the planetary gear 30 may comprise a star arrangement, in which the planet carrier 34 is supported in a fixed manner, and the ring (or annulus) gear 38 is rotatable. In such an arrangement, the fan 23 is driven by the ring gear 38. By way of further alternative example, the gear 30 may be a differential gearbox in which the ring gear 38 as well as the planet carrier 34 are both rotatable.

[0075] It will be obvious that the arrangement shown in FIGS. 2 and 3 serves merely as an example, and the scope of the present disclosure also comprises various alternatives. Purely by way of example, any suitable arrangement may be used for locating the planetary gear 30 in the engine 10 and/or for connecting the planetary gear 30 to the engine 10. By way of further example, the connections (such as the connections 36, 40 in the embodiment according to FIG. 2) between the planetary gear 30 and other parts of the engine 10 (such as the core engine shaft 26, the output shaft and the stationary support structure 24) may have any desired degree of stiffness or flexibility.

[0076] By way of further example, any suitable arrangement of the bearings between rotating and stationary parts of the engine 10 (for example between the input and output shafts of the planetary gear 30 and the fixed structures, such as for example the gearbox casing) may be used, and the disclosure is not limited to the exemplary arrangement of FIG. 2. For example, where the planetary gear 30 has a star arrangement, the person skilled in the art would readily understand that the arrangement of output and support connections and bearing locations would typically be different from that shown in FIG. 2.

[0077] Accordingly, the present disclosure extends to an aircraft engine 10 having any arrangement of gearbox styles (for example star arrangement or planetary arrangements), support structures, input and output shaft arrangement, and bearing locations.

[0078] Optionally, the planetary gear 30 may drive additional and/or alternative components (e.g. the intermediate pressure compressor and/or a booster compressor).

[0079] Other aircraft engines 10 to which the present disclosure may be applied may have alternative configurations. For example, such aircraft engines 10 may have a different number of compressors and/or turbines and/or a different number of interconnecting shafts. By way of further example, the engine 10 shown in FIG. 1 has a split flow nozzle 20, meaning that the flow through the bypass duct 22 has its own nozzle that is separate from and arranged radially outside of the core engine exhaust nozzle 20. However, this is not to be taken in a limiting manner, and any aspect of the present disclosure may also apply to engines 10 in which the flow through the bypass duct 22 and the flow through the core engine 11 is intermixed or combined by a single nozzle (in front of or upstream), which is referred to as a mixed flow nozzle. One or both nozzles may have a fixed or variable cross section (independently of whether a mixed or a partial flow is present). Whilst the example described herein relates to a turbofan engine, the disclosure may apply, for example, to any type of aircraft engine, such as an engine 10 with an open rotor (in which the fan stage 23 is not surrounded by a housing) or to a turboprop engine, for example.

[0080] The geometry of the aircraft engine 10 and its components is defined by a conventional axis system, comprising an axial direction (which is aligned with the rotational axis 9), a radial direction (in the bottom-to-top direction in FIG. 1), and a circumferential direction (perpendicular to the view of FIG. 1). The axial, radial and circumferential directions are mutually perpendicular.

[0081] Shown in the following are several embodiments for shaft arrangements in connection with an aircraft engine 10, namely a fan gear engine. As shown in FIGS. 1 and 2, this gear 30 serves for reducing a rotational speed of a driving turbine 19 in such a manner that the fan 23 can be driven with a lower rotational speed. Here, different shafts 50, 51 have to be connected to each other on the drive and output side of the gear 30.

[0082] One embodiment for connecting two shafts 50, 51 on the drive or the output side is shown schematically in FIG. 4. The drive is effected via the planetary carrier 38, which is shown here symbolically. The first shaft 50 is connected to the planetary carrier 38, so that the torque is ultimately transmitted to the fan 23 via the shaft arrangement (see FIG. 2). This transmission occurs via the second shaft 51 that is arranged concentrically with respect to the first shaft 50.

[0083] In this exemplary embodiment, concentrically means that the two shafts 50, 51 have a common rotational axis 9. Also, the second shaft 51 has a smaller diameter at the drive end than the first shaft 50; the two shaft ends overlap over a certain distance (overlapping area U).

[0084] In another embodiment, the shaft arrangement can also be embodied so as to overlap in exactly the opposite manner, i.e. the first shaft 50 has a smaller diameter than the second shaft 51.

[0085] In the overlapping area U, the two concentric shafts 50, 51 are connected to each other via an elastically bending connection element 53, which will be described in more detail in FIG. 5.

[0086] FIG. 5 shows the sectional view of the shaft arrangement in a plane E (see FIG. 4). Here, the shaft end of the first shaft 50 concentrically surrounds the shaft end of the inner, second shaft 51. For better rendering in the drawing, the radial distance between the shafts 50, 51 is shown in an enlarged manner.

[0087] Arranged at the respective shaft ends of the shafts 50, 51 are ten projections by way of envelope elements 52, with the elastically bending connection element 53 being wound around them. As shown in FIG. 5, here the elastically bending connection element 53 is wound about the envelope elements 52 alternatingly on the inner shaft 51 and the outer shaft 52. At that, the elastically bending connection element 53 can also be slightly pre-stressed. Thus, e.g. a spring element that is arranged at one of the shafts 50, 51 can press on the elastically bending connection element 53 in a spring-loaded manner.

[0088] In this embodiment, the envelope elements 52 overlap in the overlapping area U.

[0089] Here, the envelope elements 52 are formed as projections that extend in the axial direction of the shaft 50, 51. FIG. 6 shows a one-piece connection of the envelope elements 52 with a shaft end, wherein only six envelope elements are provided in the present case.

[0090] Here, the elastically bending connection element 53 is formed as a wire rope that in general can only transmit tensile forces. At that, the wire rope is embodied as a ring that is guided around the envelope elements 52 of the shafts 50, 51 without any crossing.

[0091] If the fan 23 transmits transverse forces and/or bending moments via the second shaft 51 in the direction of the gear 30, they cannot overcome the shaft arrangement with the elastically bending connection element 53. The latter forms an elastic shaft coupling through the rope bracing, so that no transverse forces or bending moments can be transmitted to the gear 30. Here, the rope-shaped connection element 53 can only transmit tensile forces that are located within the plane E.

[0092] The driving torque of the first shaft 50 causes the tensile forces from the envelope elements 52 of the first shaft 50 to act on the envelope elements 52 of the second shaft 51. These applied tensile forces are then translated into a torque for the second shaft 51 and ultimately the fan 23. Here, the torque transmission occurs in a plane E that is perpendicular to the rotational axis 9.

[0093] In general, any rope elongation that may possibly occur due to use and/or temperature is not harmful for the efficient transmission of the torque, since only the radial angular position of the concentric shafts 50, 51 changes in the case of elongation.

[0094] In the exemplary embodiment shown here, a ring-shaped wire rope is used as the elastically bending connection element 53. In general, also two or more wire ropes can be wound around the envelope elements 52. The wire rope can have a diameter of 10 to 25 mm, e.g. 15 mm. The strength is sufficient to transmit the high torques during output or also during drive of the gear.

[0095] Here, it can also be expedient to provide the elastically bending connection elements 53 and/or the envelope elements 52 with a low-friction coating.

[0096] It is also possible that the elastically bending connection element 53 is formed as a strap or a chain, since these too can generally only transmit tensile forces.

[0097] FIG. 6 shows a further feature at an envelope element 52 by way of example. At the distal end of the envelope elements 52, means for axially affixing the elastically bending connection element 53 (which is not shown here) can be arranged. Through the disc 55 shown here any sliding off of the elastically bending connection element 53 is avoided.

[0098] FIG. 7 shows a further embodiment in which the envelope elements 52 are formed as openings that are arranged about the circumference of the shafts 50, 51. Here, the elastically bending connection element 53 (which is not shown here) is braided alternatingly through these openings 53 to connect the concentric shafts 50, 51 to each other.

[0099] In the embodiments known so far, the shaft connection through the at least one elastically bending connecting means 53 was in the foreground. It generally forms an elastic coupling.

[0100] However, in general this connection can also be formed in terms of a mechanical securing device against any overloading, in particular overloading by torque. The elastically bending connecting means 53 can have a defined tear limit. If that is exceeded, e.g. through a defect in the gear 30, the elastically bending connecting means 53 tears, so that e.g. the output-side part, i.e. the second shaft 51, can rotate freely. This may be necessary to avoid blocking the fan 23 in the event of any damage.

[0101] FIG. 8 shows a further embodiment in which the envelope elements 52 are formed in such a manner that they have two elastically bending connecting means 53 arranged axially in the parallel planes E, E; which an axial offset thus being present. According to a required torque transmission of the shafts 50, 51, the tensile stress of the two elastically bending connecting means 53 can be correspondingly adjusted, i.e. the elastically bending connecting means 53 do not have to be identical in E and E.

PARTS LIST

[0102] 9 rotational axis [0103] 10 aircraft engine [0104] 11 core engine [0105] 12 air inlet [0106] 14 compressor, low pressure compressor [0107] 15 high pressure compressor [0108] 16 combustion device [0109] 17 high pressure turbine [0110] 18 bypass duct discharge nozzle [0111] 19 turbine, low pressure turbine [0112] 20 core engine discharge nozzle [0113] 21 nacelle [0114] 22 bypass duct (subsidiary flow duct) [0115] 23 fan [0116] 24 stationary support structure [0117] 26 core engine shaft [0118] 27 connecting shaft [0119] 28 sun gear [0120] 30 planetary gear [0121] 32 planetary wheel [0122] 32, 32 planetary wheel elements [0123] 34 planetary carrier for planetary wheels [0124] 36 connections [0125] 38 ring gear [0126] 40 connections [0127] 50 first shaft [0128] 51 second shaft [0129] 52 envelope element [0130] 53 elastically bending connection element [0131] 54 opening in shaft for inserting the elastically bending connecting means [0132] A flow through the core engine [0133] B flow through the bypass duct [0134] E. E plane of the elastically bending connection element [0135] U overlapping area