Rolling element device with jointly tiltable raceways

Abstract

A roller element device, in particular for a gas turbine engine, comprises an outer ring with an inner raceway, an inner ring with an outer raceway, and roller elements which are arranged between the raceways so as to roll thereon, wherein the outer ring and the inner ring are each connected via a connecting portion to a respective fixing portion for fixing to one of two components which are rotatable relative to each other about a rotation axis, and the connecting portions are formed such that the two raceways can be jointly tilted at least in portions relative to the rotation axis.

Claims

1. A gas turbine engine for an aircraft, comprising: a core engine comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor; a fan which is positioned upstream of the core engine, wherein the fan comprises a plurality of fan blades; and a gear mechanism which is drivable by the core shaft, wherein the fan is drivable by the gear mechanism at a lower speed than the core shaft, wherein the gear mechanism comprises: a roller element device, comprising: an outer ring with an inner raceway, an inner ring with an outer raceway, and roller elements arranged between the inner and outer raceways so as to roll on the inner and outer raceways, wherein the outer ring and the inner ring are each connected via a connecting portion to a respective fixing portion for fixing to one of two components that are rotatable relative to each other about a rotation axis, and wherein the connecting portions are formed such that inner and outer raceways are jointly tiltable, at least in portions relative to the rotation axis; wherein the connecting portions each have a stiffness, and the stiffnesses are matched to each other; wherein the stiffnesses have a ratio relative to each other of 1.0+/−0.2.

2. The gas turbine engine according to claim 1, wherein the two components that are rotatable relative to each other about the rotation axis are a stationary supporting structure and a component of the gas turbine engine which is rotatable relative thereto via the turbine, and the roller element device is configured for rotatable mounting of the rotatable component on the stationary supporting structure.

3. The gas turbine engine according to claim 1, wherein the connecting portions are flexible.

4. The gas turbine engine according to claim 1, wherein the connecting portions are deformed under effect of a force such that the two raceways at least in portions are tilted by a same angle relative to the rotation axis.

5. The gas turbine engine according to claim 1, wherein the inner and outer raceways are oriented parallel to each other both in a state tilted relative to the rotation axis and in a non-tilted state.

6. The gas turbine engine according to claim 1, wherein the inner and outer raceways are arranged overhanging relative to the respective fixing portions.

7. The gas turbine engine according to claim 1, wherein the outer ring and the inner ring are axially spaced from the respective fixing portions by the respective connecting portions.

8. The gas turbine engine according to claim 1, wherein the roller element device is a roller bearing.

9. The gas turbine engine according to claim 1, wherein the roller element device is a cylindrical roller bearing.

10. The gas turbine engine according to claim 1, wherein the gear mechanism is a planetary gear mechanism with a gear element mounted rotatably by the roller element device.

11. The gas turbine engine according to claim 1, wherein: the turbine is a first turbine, the compressor is a first compressor, and the core shaft is a first core shaft; the core engine further comprises a second turbine, a second compressor, and a second core shaft which connects the second turbine to the second compressor; and the second turbine, second compressor, and second core shaft are arranged to rotate at a higher speed than the first core shaft.

12. The gas turbine engine according to claim 1, wherein the stiffnesses have a ratio relative to each other of 1.0+/−0.1.

13. The gas turbine engine according to claim 1, wherein the stiffnesses have a ratio relative to each other of 1.0+/−0.05.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments will now be described by way of example, with reference to the figures, in which:

(2) FIG. 1 shows an aircraft in the form of an airplane with several gas turbine engines;

(3) FIG. 2 shows a sectional side view of a gas turbine engine;

(4) FIG. 3 shows a close-up lateral sectional view of an upstream portion of a gas turbine engine;

(5) FIG. 4 shows a partially cut-away view of a gear mechanism for a gas turbine engine;

(6) FIG. 5 shows a sectional view of a roller element device;

(7) FIG. 6 shows a sectional view of a roller element device in a force-free state;

(8) FIG. 7 shows the roller element device from FIG. 6, wherein additional directions of forces are illustrated;

(9) FIG. 8 shows the roller element device from FIGS. 6 and 7 in a state in which the forces illustrated in FIG. 7 are acting on the roller element device; and

(10) FIG. 9 shows a method for producing a roller element device.

DETAILED DESCRIPTION

(11) FIG. 1 shows an aircraft 8 in the form of an airplane. The aircraft 8 comprises a plurality of gas turbine engines 10. In order to consume as little fuel as possible and hence allow efficient operation and long ranges, aircraft components are regularly produced in lightweight design. Furthermore, many aircraft components are normally designed so as to achieve service intervals which are as long as possible, and to ensure maximum security against failure.

(12) FIG. 2 illustrates a gas turbine engine 10 having a principal rotational axis 9. The gas turbine engine 10 comprises an air inlet 12 and a fan 23 that generates two air flows: a core air flow A and a bypass air flow B. The gas turbine engine 10 comprises a core 11 that receives the core air flow A. When viewed in the order corresponding to the axial direction of flow, the core engine 11 comprises a low-pressure compressor 14, a high-pressure compressor 15, a combustion device 16, a high-pressure turbine 17, a low-pressure turbine 19, and a core thrust nozzle 20. An engine nacelle 21 surrounds the gas turbine engine 10 and defines a bypass duct 22 and a bypass thrust nozzle 18. The bypass airflow B flows through the bypass duct 22. The fan 23 is attached to and driven by the low-pressure turbine 19 via a shaft 26 and an epicyclic planetary gear mechanism 30.

(13) During operation, the core air flow A is accelerated and compressed by the low-pressure compressor 14 and directed into the high-pressure compressor 15, where further compression takes place. The compressed air expelled from the high-pressure compressor 15 is directed into the combustion device 16, where it is mixed with fuel and the mixture is combusted. The resulting hot combustion products then propagate through the high-pressure and the low-pressure turbines 17, 19 and thereby drive said turbines, before they are expelled through the nozzle 20 to provide a certain thrust. The high-pressure turbine 17 drives the high-pressure compressor 15 by means of a suitable connection shaft 27. The fan 23 generally provides the major part of the propulsive thrust. The epicyclic planetary gear mechanism 30 is a reduction gear.

(14) An exemplary arrangement for a geared fan gas turbine engine 10 is shown in FIG. 3. The low-pressure turbine 19 (see FIG. 2) drives the shaft 26, which is coupled to a sun wheel 28 of the epicyclic planetary gear mechanism 30. Radially outwardly of the sun wheel 28 and intermeshing therewith is a plurality of planet wheels 32 that are coupled together by a planet carrier 34. The planet carrier 34 guides the planet wheels 32 in such a way that they circulate synchronously around the sun wheel 28, whilst enabling each planet wheel 32 to rotate about its own axis. The planet carrier 34 is coupled via linkages 36 and an output shaft 42 to the fan 23 in order to drive its rotation about the engine axis 9. Radially to the outside of the planet wheels 32 and intermeshing therewith is an external gear or ring gear 38 that is coupled, via linkages 40, to a stationary supporting structure 24.

(15) Note that the terms “low-pressure turbine” and “low-pressure compressor” as used herein may be taken to mean the lowest-pressure turbine stage and lowest-pressure compressor stage (i.e. not including the fan 23) respectively, and/or the turbine and compressor stages that are connected together by the connecting shaft 26 with the lowest rotational speed in the engine (i.e. not including the gearbox output shaft that drives the fan 23). In some documents, the “low-pressure turbine” and the “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 fan 23 can be referred to as a first, or lowest-pressure, compression stage.

(16) The epicyclic planetary gear mechanism 30 is shown by way of example in greater detail in FIG. 4. The sun wheel 28, planet wheels 32 and ring gear 38 in each case comprise teeth on their periphery to allow intermeshing with the other gearwheels. However, for clarity, only exemplary portions of the teeth are illustrated in FIG. 4. Although four planet wheels 32 are illustrated, it will be apparent to the person skilled in the art that more or fewer planet wheels 32 may be provided within the scope of protection of the claimed invention. Practical applications of an epicyclic planetary gear mechanism 30 generally comprise at least three planet wheels 32.

(17) The epicyclic planetary gear mechanism 30 illustrated by way of example in FIGS. 3 and 4 is a planetary gear mechanism in which the planet carrier 34 is coupled to the output shaft 42 via linkages 36, with the ring gear 38 being fixed. However, any other suitable type of planetary transmission 30 may be used. As a further example, the planetary gear mechanism 30 may be a star arrangement, in which the planet carrier 34 is held fixed, with the ring gear (or external gear) 38 allowed to rotate. In such an arrangement, the fan 23 is driven by the ring gear 38. As a further alternative example, the gear mechanism 30 can be a differential gear mechanism in which both the ring gear 38 and the planet carrier 34 are allowed to rotate.

(18) It will be appreciated that the arrangement shown in FIGS. 3 and 4 is by way of example only, and various alternatives are within the scope of protection of the present disclosure. Purely by way of example, any suitable arrangement may be used for locating the gear mechanism 30 in the gas turbine engine 10 and/or for connecting the gear mechanism 30 to the gas turbine engine 10. As a further example, the connections (for example the linkages 36, 40 in the example of FIG. 3) between the gear mechanism 30 and other parts of the gas turbine engine 10 (such as the input shaft 26, the output shaft and the fixed structure 24) may have a certain degree of stiffness or flexibility. As a further example, any suitable arrangement of the bearings between rotating and stationary parts of the gas turbine engine 10 (for example between the input and output shafts of the gear mechanism and the fixed structures, such as the gear casing) may be used, and the disclosure is not limited to the exemplary arrangement of FIG. 3. For example, where the gear mechanism 30 has a star arrangement (described above), the person skilled in the art would readily understand that the arrangement of output and support linkages and bearing positions would typically be different to that shown by way of example in FIG. 3.

(19) Accordingly, the present disclosure extends to a gas turbine engine having any arrangement of gear mechanism types (for example star or epicyclic-planetary), supporting structures, input and output shaft arrangement, and bearing locations.

(20) Optionally, the gear mechanism may drive additional and/or alternative components (e.g. the intermediate-pressure compressor and/or a booster compressor).

(21) Other gas turbine engines in which the present disclosure can be used may have alternative configurations. For example, such engines may have an alternative number of compressors and/or turbines and/or an alternative number of connecting shafts. By way of a further example, the gas turbine engine shown in FIG. 2 has a split flow nozzle 20, 22, meaning that the flow through the bypass duct 22 has its own nozzle that is separate from and radially outside the core engine nozzle 20. However, this is not restrictive, and any aspect of the present disclosure can also apply to engines in which the flow through the bypass duct 22 and the flow through the core 11 are 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) can have a fixed or variable area. Whilst the described example relates to a turbofan engine, the disclosure may be applied, 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. In some arrangements, the gas turbine engine 10 may not comprise a gear mechanism 30.

(22) The geometry of the gas turbine engine 10, and components thereof, is/are defined by a conventional axis system, comprising an axial direction (which is aligned with the rotation axis 9), a radial direction (in the bottom-to-top direction in FIG. 2), and a circumferential direction (perpendicular to the view in FIG. 2). The axial, radial and circumferential directions run so as to be mutually perpendicular.

(23) The gas turbine engine 10 comprises several roller element devices 1, 1′. A roller element device 1 serves as a roller bearing for the planet carrier 34 on the stationary supporting structure 24. Another roller element device 1′ serves as a roller bearing for the output shaft 42 on the stationary supporting structure 24. The roller element devices 1, 1′ are explained in more detail below.

(24) FIG. 5 shows the roller element device 1 serving as a roller bearing for the planet carrier 34.

(25) The roller element device 1 comprises an outer supporting structure with an outer ring 50, a connecting portion 52 and a fixing portion 53. In the present case, the outer supporting structure is configured as one piece, wherein multipiece designs are also conceivable.

(26) The roller element device 1 furthermore comprises an inner supporting structure with an inner ring 54, a connecting portion 56 and a fixing portion 57. In the example shown, the inner supporting structure is configured as one piece, wherein multipiece designs are also conceivable here too.

(27) The fixing portion 53 of the outer supporting structure is attached to the stationary supporting structure 24 of the gas turbine engine 10, e.g. by means of the bolted joints indicated schematically in FIG. 5, alternatively for example by a weld seam or similar.

(28) The fixing portion 57 of the inner supporting structure is attached to the planet carrier 34 of the gear mechanism 30 of the gas turbine engine 10, e.g. by means of the bolted joints indicated schematically in FIG. 5, alternatively for example by a weld seam or similar.

(29) In the present case, the fixing portions 53, 57 with the respective connecting portion 52, 56 are formed L-shaped in cross-section, but other configurations are also conceivable, e.g. an elongate configuration without angle, or a configuration with several angles. The fixing portions 53, 57 each form a flange. The fixing portions 53, 57 extend in the radial direction starting from the respective connecting portion 52, 56, in the same direction, here towards the outside.

(30) FIG. 5 shows the main rotation axis 9. It is evident that the two connecting portions 52, 56 run parallel to the main rotation axis 9. In concrete terms, the connecting portions 52, 56 are each formed as hollow cylinders. The connecting portions 52, 56 each run coaxially to the main rotation axis 9.

(31) The two fixing portions 53, 57 are spaced apart from each other in the axial direction (parallel to the main rotation axis 9). In the present case, the inner ring 54 is arranged inside the outer ring 50. The outer ring 50 and the inner ring 54 are arranged coaxially to each other. The outer ring 50 has an inner raceway 51 running around the inside. The inner ring 54 has an outer raceway 55 running around the outside. A gap is formed between the raceways 51, 55. Several roller elements 58 are arranged between the raceways 51, 55. In the present case, the roller elements 58 are formed as cylindrical rollers, and can roll on the two running surfaces 51, 55 so that the inner ring 54 and the outer ring 50 are rotatable relative to each other about the main rotation axis 9.

(32) The connecting portion 52 of the outer supporting structure connects the fixing portion 53 of the outer supporting structure to the outer ring 50. The connecting portion 56 of the inner supporting structure connects the fixing portion 57 of the inner supporting structure to the inner ring 54. The raceways 51, 55 are arranged overhanging relative to the respective fixing portion 53, 57. The raceways 51, 55 protrude axially from the respective fixing portion 53, 57. The connecting portions 52, 56 each serve as a connecting arm.

(33) The connecting portions 52, 56 have stiffnesses such that they are flexible and bendable under the loads occurring in operation of the gas turbine engine 10 (in normal operation and/or in extraordinary load cases). In the present case, the stiffnesses of the connecting portions 52, 56 are matched to each other such that the two raceways 51, 55 are jointly tiltable at least in portions or as a whole relative to the rotation axis. If adjacent portions of the raceways 51, 55, e.g. the portions are shown in FIG. 5, are tilted relative to the main rotation axis 9, then the adjacent portions tilt by identical angular amounts. The raceways 51, 55 remain parallel to each other. This may prevent (in particular over a wide radial load range) loads from being supported only or mainly by edges at the axial end faces of the roller elements 58, which can lead to high wear or even to failure of one or more roller elements 58.

(34) FIG. 6 shows a roller element device 1′ which largely corresponds to the roller element device 1 shown in FIG. 5, so only the differences are explained below.

(35) The fixing portions 53, 57 extend in the radial direction, starting from the respective connecting portion 52, 56, in different directions. In the present case, the fixing portion 53 of the outer supporting structure extends radially outwardly (away from the main rotation axis 9), and the fixing portion 57 of the inner supporting structure extends radially inwardly (towards the main rotation axis 9).

(36) The fixing portion 57 of the inner supporting structure is attached to the output shaft 42 driving the fan 23.

(37) FIG. 6 furthermore shows an optional opening 60 (generally a weakening) of one of the connecting portions, here for example the connecting portion 56 of the inner supporting structure. The opening 60 in the present case is configured as a passage bore. The opening 60 may increase the flexibility of the connecting portion 56, e.g. to adapt this to the flexibility of the other connecting portion 52.

(38) Furthermore, FIG. 6 indicates in dotted lines an optional reinforcement 61, here in the form of the reinforcing rib. The reinforcement 61 may reduce the flexibility of the connecting portion 52, e.g. to adapt this to the flexibility of the other connecting portion 56.

(39) FIG. 7 shows the roller element device 1′ from FIG. 6, wherein an additional input force F is depicted. The force F acts radially outwardly on the output shaft 42 and thereby presses the fixing portion 57 of the inner supporting structure towards the outside. FIG. 7 shows a state of the output shaft 42 after not moving or moving towards the outside by only an insignificant radial displacement R.

(40) FIG. 7 furthermore shows arrows indicating the tilt direction in which the inner ring 54 and outer ring 50 tilt under the effect of the force F. Accordingly, the fixing portions 53, 57 move axially closer together.

(41) It is provided that the connecting portions 52, 56 have rotational stiffnesses K.sub.φa, K.sub.φi, the ratio of which is 1.0+/−0.2, in particular 1.0+/−0.1, in particular 1.0+/−0.05. In the example shown, the ratio is 1.0. This may ensure that despite the effect of the radial force F, no edge wear occurs. The ratio may also be indicated as follows: 0.9*K.sub.φi<K.sub.φa<1.1*K.sub.φi.

(42) The rotational stiffnesses may e.g. be measured in that one end of the respective connecting portion 52, 56 is held stationary while a torque is exerted on the other end, and the deflection determined. This may optionally take place with a cutout piece of the respective connecting portion 52, 56.

(43) FIG. 8 shows a state in which the output shaft 42 has moved radially outwardly by a radial displacement R under the effect of the force F. The connecting portions 52, 56 have permitted this movement and have thereby been deformed elastically. By matching the stiffnesses of the connecting portions 52, 56 to each other, the inner ring 54 and the outer ring 50 and hence the two raceways 51, 55 are tilted jointly and parallel to each other.

(44) The angles α.sub.a, α.sub.i, by which the inner ring 54 and the outer ring 50 have been tilted are illustrated by the dotted secondary lines. The angles α.sub.a, α.sub.i here fulfil the following equation: |α.sub.a−α.sub.i|<=1.5 mrad.

(45) Thus parallel tilting occurs over a defined, in particular a predefined load range.

(46) Thus the output shaft 42 is movable radially and/or axially relative to the stationary supporting structure 24 under the forces occurring (in general, this applies to two components rotatably connected together by means of the roller element device 1; 1′). It is thereby possible to accommodate loads during the operation of the gas turbine engine 10, e.g. those due to load changes or thermal expansion or contraction of individual components.

(47) Thus a roller bearing is provided which can operate under conditions which would normally lead to bearing damage.

(48) FIG. 9 shows a method for producing a roller element device 1; 1′, in particular as described above.

(49) In a first step S1, a geometry (in particular a material thickness) and/or material properties (in particular the material choice, e.g. steel) of connecting portions 52, 56 for a roller element device 1; 1′ are determined, in particular in an optimization procedure. For this purpose, one or more of the parameters mentioned is varied with the aim of achieving rotational stiffnesses which are as far as possible the same for the connecting portions 52, 56. Here again, a predefined bearing stiffness may be specified as a target value.

(50) As an option, the optimization procedure comprises an FEM algorithm and/or is performed iteratively.

(51) In a second step S2, an outer ring 50 with an inner raceway 51, and an inner ring 54 with an outer raceway 55 are provided, wherein the outer ring 50 and the inner ring 54 are each connected via a connecting portion 52, 56 to a respective fixing portion 53, 57 for fixed connection to one of two components 24, 34; 24, 42 which are rotatable relative to each other about a rotation axis 9, and wherein the connecting portions 52, 56 are matched to each other (in particular according to the optimization procedure) such that the two raceways 51, 55 can be jointly tilted at least in portions relative to the rotation axis 9.

(52) In a third step S3, roller elements 58 are arranged between the raceways 51, 55 such that the roller elements 58 can roll on the two raceways 51, 55 simultaneously.

(53) Thus a roller element bearing is provided, in particular for a geared turbofan engine, which has balanced bending moments.

(54) It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. Any of the features may be used separately or in combination with any other features, unless they are mutually exclusive, and the disclosure extends to and includes all combinations and subcombinations of one or more features which are described here. In particular, it is pointed out that the roller element device 1, 1′ can in particular be used at any bearing positions in which at least one of the two raceways cannot be supported directly radially outwardly.

LIST OF REFERENCE SIGNS

(55) 1, 1′ Roller element device 8 Aircraft 9 Main rotation axis 10 Gas turbine engine 11 Core engine 12 Air intake 14 Low-pressure compressor 15 High-pressure compressor 16 Combustion device 17 High-pressure turbine 18 Bypass thrust nozzle 19 Low-pressure turbine 20 Core thrust nozzle 21 Engine nacelle 22 Bypass duct 23 Fan 24 Stationary supporting structure 26 Shaft 27 Connecting shaft 28 Sun wheel 30 Gear mechanism 32 Planet wheel 34 Planet carrier 36 Linkage 38 Ring gear 40 Linkage 42 Output shaft 50 Outer ring 51 Inner raceway 52 Connecting portion 53 Fixing portion 54 Inner ring 55 Outer raceway 56 Connecting portion 57 Fixing portion 58 Roller element 60 Opening 61 Reinforcement A Core airflow B Bypass airflow F Force R Radial displacement α.sub.a, α.sub.i Angle