Reinforcement member for epicyclic gear system housing assembly

Abstract

The invention discloses a reinforcement member for an epicyclic gear system housing assembly. A planetary gear housing assembly in an epicyclic gear system of a gas turbine engine having an engine housing includes an aft planet carrier assembly, a forward planet carrier assembly, and a plurality of planet gears. A rear flange of the rear planet carrier assembly is coupled to the engine housing to define a first torsional stiffness. A front flange of the front planet carrier assembly is coupled to the rear flange to define a second torsional stiffness. The second torsional stiffness may be between 60% and 80% of the first torsional stiffness. The planetary gear housing assembly may also include a reinforcement member positioned between the front carrier assembly and the rear carrier assembly.

Description

[0001] This application is a divisional application of the Chinese application with application number 202011051750.3, application date September 29, 2020, and title “Reinforcement structure for epicyclic gear system housing assembly”. CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is related to the following concurrently filed and co-pending U.S. patent applications: U.S. Patent Application No. 16 / 592,492, entitled “EPICYCLICAL GEAR SYSTEM HOUSING ASSEMBLY,” attorney docket number G2640-00402 / RCA12398; U.S. Patent Application No. XXXXX, entitled “BEARING SPRING FOR EPICYCLICAL GEAR SYSTEM HOUSING ASSEMBLY,” attorney docket number G2640-00404 / RCA12400; and U.S. Patent Application No. XXXXX, entitled “STATIC CURVIC JOINT FOR EPICYCLICAL GEAR SYSTEM HOUSING ASSEMBLY,” attorney docket number G2640-00405 / RCA12406. ASSEMBLY" ("Static Flex Joint for Epicyclic Gear System Housing Assembly"), U.S. Patent Application No. 16 / 592,499, Attorney Docket No. G2640-00408 / RCA12402, the entire contents of each of the above applications are incorporated herein by reference. Background Art

[0003] Epicyclic gear systems can be used in rotating machines to transfer energy from one component (such as a rotatable shaft) to another. By changing certain variables (such as the number, size, and number of teeth of the gears), epicyclic gear systems can be designed to transfer energy between components at a desired ratio, and generally convert a high-speed, low-torque input to a lower-speed, higher-torque output.

[0004] Epicyclic gear systems can be suitable for a wide range of applications, including transferring energy from a turbine shaft to a fan rotor in a geared turbofan engine. However, in such dynamic applications, epicyclic gear systems must be designed to allow a certain degree of relative motion between parts of the system to avoid excessive wear and system failure under extreme conditions. Summary of the invention

[0005] According to some aspects of the present disclosure, a planetary gear housing assembly for an epicyclic gear system of a gas turbine engine having an engine housing is disclosed. The planetary gear housing assembly includes a rear planetary gear carrier assembly, a front planetary gear carrier assembly, and a plurality of planetary gears. The rear planetary gear carrier assembly includes: a rear flange defining a central aperture; and a plurality of gear shaft pockets, the plurality of gear shafts surrounding the central aperture and positioned radially outward of the central aperture. Each pocket has a cylindrical wall, and the rear flange is coupled to the engine housing to define a rear torsional stiffness. The front planetary gear carrier assembly includes: a front flange defining a central aperture; and a plurality of gear shaft pockets, the plurality of gear shaft pockets surrounding the central aperture and positioned radially outward of the central aperture. Each pocket has a cylindrical wall, and the front flange is coupled to the rear planetary gear carrier assembly to define a front torsional stiffness. The plurality of planetary gears each include a cylindrical shaft having a front end disposed in a gear shaft recess of the front planetary gear carrier assembly and coaxial with the cylindrical wall of the recess, a rear end disposed in a gear shaft recess of the rear planetary gear carrier assembly and coaxial with the cylindrical wall of the recess, and one or more gears carried by the shaft between the front end and the rear end. The front torsional stiffness is between 60% and 80% of the rear torsional stiffness.

[0006] In some embodiments, the front torsional stiffness is between 65% and 75% of the rear torsional stiffness. In some embodiments, the rear planetary gear carrier assembly further comprises an annular mounting flange extending from the rear flange, the annular mounting flange being positioned forward of and coaxial with the central aperture, the mounting flange forming a forward facing mounting surface. In some embodiments, the front planetary gear carrier assembly further comprises an annular mounting flange extending from the front flange, the annular mounting flange being positioned rearward of and coaxial with the central aperture, the mounting flange forming a rearward facing mounting surface. In some embodiments, the mounting surfaces are positioned relative to each other, thereby coupling the rear planetary gear carrier assembly and the front planetary gear carrier assembly.

[0007] In some embodiments, the shaft and the gear form a compound star gear in an epicyclic gear system. In some embodiments, the front planetary gear carrier assembly further comprises a reinforcement member positioned between the rear planetary gear carrier assembly and the front flange, the reinforcement member comprising: an annular body defining a central aperture; and a plurality of radial flanges extending radially outward from the annular body, each of the plurality of radial flanges partially defining a surface facing the gear. In some embodiments, the reinforcement member abuts both the front flange and the rear planetary gear carrier assembly.

[0008] According to a further aspect of the present disclosure, a planetary gear housing assembly in an epicyclic gear assembly includes a rear planetary gear carrier assembly, a front planetary gear carrier assembly, a plurality of planetary gears, and a reinforcement member. The rear planetary gear carrier assembly includes: a rear flange defining a central aperture; and a plurality of gear shaft recesses surrounding the central aperture and positioned radially outward of the central aperture, each recess having a cylindrical wall. The front planetary gear carrier assembly includes: a front flange defining a central aperture; and a plurality of gear shaft recesses surrounding the central aperture and positioned radially outward of the central aperture, each recess having a cylindrical wall. Each of the plurality of planetary gears comprises a cylindrical shaft having: a front end portion disposed in a gear shaft recess of the front planetary gear carrier assembly and coaxial with the cylindrical wall of the recess; a rear end portion disposed in a gear shaft recess of the rear planetary gear carrier assembly and coaxial with the cylindrical wall of the recess; and one or more gears carried by the shaft between the front end portion and the rear end portion. A reinforcing member is positioned between the rear planetary gear carrier assembly and the front planetary gear carrier assembly. The reinforcing member comprises: an annular body defining a central aperture; and a plurality of radial flanges extending radially outward from the annular body, each of the plurality of radial flanges partially defining a surface facing the gear.

[0009] In some embodiments, the rear planetary gear carrier assembly is coupled to the front planetary gear carrier assembly. In some embodiments, the rear planetary gear carrier assembly further comprises an annular mounting flange extending from the rear flange, the annular mounting flange being positioned forward of and coaxial with the central aperture, the mounting flange forming a forward facing mounting surface. In some embodiments, the front planetary gear carrier assembly further comprises an annular mounting flange extending from the front flange, the annular mounting flange being positioned rearward of and coaxial with the central aperture, the mounting flange forming a rearward facing mounting surface. In some embodiments, the mounting surfaces are positioned relative to each other, thereby coupling the rear planetary gear carrier assembly and the front planetary gear carrier assembly.

[0010] In some embodiments, the shaft and the gear form a compound star gear in an epicyclic gear system. In some embodiments, the epicyclic gear assembly is part of a gas turbine engine having an engine casing, and wherein the rear flange is coupled to the engine casing to define a rear torsional stiffness, and the front flange is coupled to the rear planetary gear carrier assembly to define a front torsional stiffness, and wherein the front torsional stiffness is between 50% and 90% of the rear torsional stiffness. In some embodiments, the front torsional stiffness is between 60% and 80% of the rear torsional stiffness. In some embodiments, the front torsional stiffness is between 65% and 75% of the rear torsional stiffness. In some embodiments, the reinforcement member includes seven gear-facing surfaces. In some embodiments, the rear flange includes a radially outer mounting surface to mount the planetary gear housing assembly to the engine casing.

[0011] According to some further aspects of the present disclosure, a gas turbine engine for an aircraft includes an engine core, a fan, and a gearbox. The engine core includes a turbine, a compressor, and a mandrel that connects the turbine to the compressor. The fan is located upstream of the engine core and includes a plurality of fan blades. The gearbox receives input from the mandrel and outputs a drive to the fan, thereby driving the fan at a speed lower than the mandrel. The gearbox has a planetary gear housing assembly, which includes a rear planetary gear carrier assembly, a front planetary gear carrier assembly, a plurality of planetary gears, and a reinforcement member. The rear planetary gear carrier assembly includes: a rear flange that defines a central aperture; and a plurality of gear shaft recesses that surround the central aperture and are positioned radially outside the central aperture, each recess having a cylindrical wall. The front planetary gear carrier assembly includes: a front flange that defines a central aperture; and a plurality of gear shaft recesses that surround the central aperture and are positioned radially outside the central aperture, each recess having a cylindrical wall. The plurality of planetary gears each include a cylindrical shaft having: a front end portion disposed in a gear shaft recess of the front planetary gear carrier assembly and coaxial with the cylindrical wall of the recess; a rear end portion disposed in a gear shaft recess of the rear planetary gear carrier assembly and coaxial with the cylindrical wall of the recess; and one or more gears carried by the shaft between the front end portion and the rear end portion. A reinforcing member is positioned between the rear planetary gear carrier assembly and the front planetary gear carrier assembly and the reinforcing member abuts against the rear planetary gear carrier assembly and the front planetary gear carrier assembly. The reinforcing member includes: an annular body defining a central aperture; and a plurality of radial flanges extending radially outward from the annular body, each of the plurality of radial flanges partially defining a surface facing the gear.

[0012] In some embodiments, each of the plurality of planetary gears includes a sun gear engaging gear and a ring gear engaging gear carried by the shaft between the front and rear ends. In some embodiments, the shaft and the gear form a compound star gear in an epicyclic gear system. In some embodiments, the gearbox further includes a roller element bearing disposed on at least a portion of one or both of the front and rear ends of the gear shaft. In some embodiments, the rear planetary gear carrier assembly defines a rear torsional stiffness and the front planetary gear carrier assembly defines a front torsional stiffness, and wherein the front torsional stiffness is between 65% and 75% of the rear torsional stiffness. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The following will become apparent with reference to the elements in the drawings which are provided for illustrative purposes.

[0014] Figure 1 is a cross-sectional side view of a gas turbine engine.

[0015] Figure 2 is a close-up cross-sectional side view of an upstream portion of a gas turbine engine.

[0016] Figure 3 is a partial cross-sectional view of a gearbox for a gas turbine engine.

[0017] Figure 4 is a schematic cross-sectional view of an epicyclic gear system according to some embodiments of the present disclosure.

[0018] Figure 5 is a detailed schematic cross-sectional view of a planetary gear disposed in an epicyclic gear system according to some embodiments of the present disclosure.

[0019] Figure 6 is an isometric view of a front planetary gear carrier assembly, a reinforcement member, and a rear carrier housing assembly of a planetary gear housing assembly according to some embodiments of the present disclosure.

[0020] Figure 7 is a partial cross-sectional view of a reinforcement member coupled between a front planetary gear carrier assembly and a rear planetary gear carrier assembly of a planetary gear housing assembly according to some embodiments.

[0021] Fig. 8A is an isometric view of a reinforcement member according to some embodiments.

[0022] Figure 8B is an isometric view of a reinforcement member according to some embodiments.

[0023] Fig. 9 is a flow chart of a method according to some embodiments of the present disclosure.

[0024] The present application discloses illustrative (i.e., example) embodiments. The claimed invention is not limited to the illustrative embodiments. Therefore, many embodiments of the claims will differ from the illustrative embodiments. Various modifications may be made to the claimed invention without departing from the spirit and scope of the present disclosure. The claims are intended to cover embodiments having these modifications. DETAILED DESCRIPTION

[0025] For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the various illustrative embodiments in the drawings, and specific language will be used to describe the same.

[0026] As noted elsewhere herein, the present disclosure may relate to a gas turbine engine. Such a gas turbine engine may include an engine core including a turbine, a combustor, a compressor, and a spindle connecting the turbine to the compressor. Such a gas turbine engine may include a fan (having fan blades) located upstream of the engine core.

[0027] The arrangement of the present disclosure is particularly advantageous, but not exclusive, for fans driven via a gearbox. Thus, a gas turbine engine may include a gearbox that receives input from a mandrel and outputs a drive to the fan so as to drive the fan at a lower speed than the mandrel. The input to the gearbox may be directly from the mandrel, or indirectly from the mandrel, for example, via a spur gear shaft and / or gears. The mandrel may rigidly connect the turbine and the compressor so that the turbine and the compressor rotate at the same speed (where the fan rotates at a lower speed).

[0028] The gas turbine engines described and / or claimed herein can have any suitable general architecture. For example, the gas turbine engine can have any desired number of shafts connecting the turbine and the compressor, for example, one, two, or three shafts. By way of example only, the turbine connected to the mandrel can be a first turbine, the compressor connected to the mandrel can be a first compressor, and the mandrel can be a first mandrel. The engine core can also include a second turbine, a second compressor, and a second mandrel connecting the second turbine to the second compressor. The second turbine, the second compressor, and the second mandrel can be arranged to rotate at a higher speed than the first mandrel.

[0029] In such an arrangement, the second compressor may be positioned axially downstream of the first compressor.The second compressor may be arranged to receive (eg directly, such as via a generally annular duct) the gas flow from the first compressor.

[0030] The gearbox may be arranged to be driven by a spindle that is configured to rotate at the lowest speed (e.g. in use) (e.g. the first spindle in the above example). For example, the gearbox may be arranged to be driven only by a spindle that is configured to rotate at the lowest speed (e.g. in use) (e.g. only the first spindle and not the second spindle in the above example). Alternatively, the gearbox may be arranged to be driven by any one or more shafts, for example the first shaft and / or the second shaft in the above example.

[0031] The gearbox can be a reduction gearbox (where the speed of the output to the fan is lower than the speed of the input from the spindle). Any type of gearbox can be used. For example, the gearbox can be a "planetary" or "star" gearbox, as described in more detail elsewhere herein. The gearbox can have any desired reduction ratio (defined as the speed of the input shaft divided by the speed of the output shaft), such as greater than 2.5, such as in the range of 3 to 4.2 or 3.2 to 3.8, for example, about or at least 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1 or 4.2. The transmission ratio can be between any two values ​​in, for example, the previous sentence. By way of example only, the gearbox can be a "star" gearbox with a transmission ratio in the range of 3.1 or 3.2 to 3.8. In some arrangements, the transmission ratio can be outside these ranges.

[0032] In any gas turbine engine described and / or claimed herein, the burner may be disposed axially downstream of the fan and the compressor. For example, where a second compressor is provided, the burner may be located directly downstream of the second compressor (e.g., at the outlet of the second compressor). As a further example, where a second turbine is provided, the airflow at the burner outlet may be provided to the inlet of the second turbine. The burner may be disposed upstream of the turbine.

[0033] The compressor or each compressor (e.g., the first compressor or the second compressor described above) may include any number of stages, such as multiple stages. Each stage may include a row of rotor blades and a row of stator blades, and the stator blades may be variable stator blades (wherein their angle of attack may be variable). The row of rotor blades and the row of stator blades may be axially offset from each other.

[0034] The turbine or each turbine (e.g., the first turbine and the second turbine described above) may include any number of stages, such as multiple stages. Each stage may include a row of rotor blades and a row of stator blades. The row of rotor blades and the row of stator blades may be axially offset from each other.

[0035] Each fan blade may be defined as having a radial span extending from a root (or hub) or 0% span position at a radially inner gas wash position to a tip at a 100% span position. The ratio of the radius of the fan blade at the hub to the radius of the fan blade at the tip may be less than (or approximately) any of the following values: 0.4, 0.39, 0.38, 0.37, 0.36, 0.35, 0.34, 0.33, 0.32, 0.31, 0.3, 0.29, 0.28, 0.27, 0.26, or 0.25. The ratio of the radius of the fan blade at the hub to the radius of the fan blade at the tip may be within an inclusive range bounded by any two values ​​in the previous sentence (i.e., these values ​​may form an upper or lower limit), for example, within a range of 0.28 to 0.32. These ratios may generally be referred to as hub-tip ratios. Both the radius at the hub and the radius at the tip can be measured at the leading edge (or axially forward most) portion of the blade. The hub-tip ratio, of course, refers to the gas washed portion of the fan blade, ie, that portion radially outward of any platform.

[0036] The radius of the fan may be measured between the centerline of the engine and the tip at the leading edge of the fan blades. The fan diameter (which may simply be twice the fan radius) may be greater than any of the following values ​​(or approximately the following values): 220 cm, 230 cm, 240 cm, 250 cm (approximately 100 inches), 260 cm, 270 cm (approximately 105 inches), 280 cm (approximately 110 inches), 290 cm (approximately 115 inches), 300 cm (approximately 120 inches), 310 cm, 320 cm (approximately 125 inches), 330 cm (approximately 130 inches), 340 cm (approximately 135 inches), 350 cm, 360 cm (approximately 140 inches), 370 cm (approximately 145 inches), 380 cm (approximately 150 inches), 390 cm (approximately 155 inches), 400 cm, 410 cm (approximately 160 inches), or 420 cm (approximately 165 inches). The fan diameter may be within an inclusive range bounded by any two values ​​in the previous sentence (ie, these values ​​may form an upper or lower limit), for example, in the range of 240 cm to 280 cm or 330 cm to 380 cm.

[0037] The speed of the fan may change when in use. Typically, for fans with larger diameters, the speed is lower. As a non-limiting example only, the speed of the fan under cruising conditions may be less than 2500 rpm, for example, less than 2300 rpm. As a further non-limiting example only, for an engine with a fan diameter in the range of 220 cm to 300 cm (e.g., 240 cm to 280 cm or 250 cm to 270 cm), the speed of the fan under cruising conditions may be in the range of 1700 rpm to 2500 rpm, for example, in the range of 1800 rpm to 2300 rpm, for example, in the range of 1900 rpm to 2100 rpm. As a further non-limiting example only, for an engine with a fan diameter in the range of 330 cm to 380 cm, the speed of the fan under cruising conditions may be in the range of 1200 rpm to 2000 rpm, for example, in the range of 1300 rpm to 1800 rpm, for example, in the range of 1400 rpm to 1800 rpm.

[0038] When a gas turbine engine is in use, the fan (with associated fan blades) rotates about an axis of rotation. This rotation causes the tip of the fan blade to move at a speed Utip. The work done by the fan blades 13 on the airflow causes the enthalpy of the airflow to rise by dH. The load at the fan tip can be defined as dH / Utip2, where dH is the enthalpy rise across the fan (e.g., 1-D (one-dimensional) average enthalpy rise), and Utip is the (translational) speed of the fan tip, such as the speed at the leading edge of the tip (which can be defined as the fan tip radius at the leading edge multiplied by the angular velocity). The fan tip load under cruise conditions can be greater than (or approximately) any of the following values: 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39 or 0.4 (all units in this paragraph are Jkg-1K-1 / (ms-1)2). The fan tip load may be within an inclusive range bounded by any two values ​​in the previous sentence (ie, these values ​​may form an upper or lower limit), for example, within a range of 0.28 to 0.31 or 0.29 to 0.3.

[0039] A gas turbine engine according to the present disclosure may have any desired bypass ratio, wherein the bypass ratio is defined as the ratio of the mass flow rate of the airflow through the bypass duct to the mass flow rate of the airflow through the engine core under cruise conditions. In some arrangements, the bypass ratio may be greater than (or about) any of the following values: 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, or 20. The bypass ratio may be within an inclusive range bounded by any two values ​​in the previous sentence (i.e., these values ​​may form an upper or lower limit), for example, within a range from 12 to 16, 13 to 15, or 13 to 14. The bypass duct may be substantially annular. The bypass duct may be located radially outside the engine core. The radially outer surface of the bypass duct may be defined by the nacelle and / or the fan case.

[0040] The total pressure ratio of the gas turbine engine described and / or claimed herein can be defined as the ratio of the stagnation pressure upstream of the fan to the stagnation pressure at the outlet of the highest pressure compressor (before entering the combustor). As a non-limiting example, the total pressure ratio of the gas turbine engine described and / or claimed herein at cruise can be greater than (or about) any of the following values: 35, 40, 45, 50, 55, 60, 65, 70, 75. The total pressure ratio can be within an inclusive range bounded by any two values ​​in the previous sentence (e.g., these values ​​can form an upper or lower limit), such as within a range of 50 to 70.

[0041] The specific thrust of an engine may be defined as the net thrust of the engine divided by the total mass flow through the engine. Under cruise conditions, the specific thrust of the engine described and / or claimed herein may be less than (or about) any of the following values: 110 Nkg-1s, 105 Nkg-1s, 100 Nkg-1s, 95 Nkg-1s, 90 Nkg-1s, 85 Nkg-1s, or 80 Nkg-1s. The specific thrust may be within an inclusive range bounded by any two values ​​in the previous sentence (e.g., these values ​​may form an upper or lower limit), for example, within a range of 80 Nkg-1s to 100 Nkg-1s, or 85 Nkg-1s to 95 Nkg-1s. Such an engine may be particularly efficient compared to conventional gas turbine engines.

[0042] The gas turbine engines described and / or claimed herein may have any desired maximum thrust. By way of non-limiting example only, the gas turbines described and / or claimed herein may be capable of producing a maximum thrust of at least (or about) any of the following values: 160 kN, 170 kN, 180 kN, 190 kN, 200 kN, 250 kN, 300 kN, 350 kN, 400 kN, 450 kN, 500 kN, or 550 kN. The maximum thrust may be within an inclusive range bounded by any two values ​​in the previous sentence (i.e., these values ​​may form an upper or lower limit). By way of example only, the gas turbines described and / or claimed herein may be capable of producing a maximum thrust in the range of 330 kN to 420 kN (e.g., 350 kN to 400 kN). The thrust mentioned above may be the maximum net thrust under standard atmospheric conditions at sea level plus 15 degrees Celsius (ambient pressure 101.3 kPa, temperature 30 degrees Celsius), with the engine at rest.

[0043] When in use, the temperature of the airflow at the inlet of the high-pressure turbine may be particularly high. This temperature, which may be referred to as TET, may be measured at the outlet of the burner, for example, just upstream of the first turbine blade, which itself may be referred to as a nozzle guide vane. When cruising, TET may be at least (or approximately) any of the following values: 1400K, 1450K, 1500K, 1550K, 1600K, or 1650K. The TET at cruise may be within the inclusive range bounded by any two values ​​in the previous sentence (i.e., these values ​​may form an upper or lower limit). The maximum TET when the engine is in use may, for example, be at least (or approximately) any of the following values: 1700K, 1750K, 1800K, 1850K, 1900K, 1950K, or 2000K. The maximum TET may be within the inclusive range bounded by any two values ​​in the previous sentence (i.e., these values ​​may form an upper or lower limit), for example, within the range of 1800K to 1950K. Maximum TET may occur, for example, at high thrust conditions, such as at maximum take-off (MTO) conditions.

[0044] The fan blades and / or airfoils of the fan blades described and / or claimed herein may be made of any suitable material or combination of materials. For example, at least a portion of the fan blade and / or airfoil may be at least partially made of a composite material, such as a metal-based composite material and / or an organic-based composite material, such as carbon fiber. As a further example, at least a portion of the fan blade and / or airfoil may be at least partially made of a metal, such as a titanium-based metal or an aluminum-based material (such as an aluminum-lithium alloy) or a steel-based material. The fan blade may include at least two regions made of different materials. For example, a fan blade may have a protective leading edge that may be made of a material that is more resistant to impact (e.g., to impact from birds, ice, or other materials) than the rest of the blade. Such a leading edge may be made, for example, of titanium or a titanium-based alloy. Thus, by way of example only, a fan blade may have a carbon fiber or aluminum base (such as an aluminum-lithium alloy) with a titanium leading edge.

[0045] The fan described and / or claimed herein may include a central portion from which fan blades may extend, for example, in a radial direction. The fan blades may be attached to the central portion in any desired manner. For example, each fan blade may include a fixture that may engage a corresponding slot in a hub (or disk). By way of example only, such a fixture may be in the form of a dovetail that may be inserted along the slot and / or engaged in a corresponding slot in the hub / disk so as to secure the fan blade to the hub / disk. As a further example, the fan blades may be formed integrally with the central portion. Such an arrangement may be referred to as a bladed disk or a bladed ring. Any suitable method may be used to manufacture such a bladed disk or bladed ring. For example, at least a portion of the fan blades may be machined from a block, and / or at least a portion of the fan blades may be attached to the hub / disk by welding (such as linear friction welding).

[0046] The gas turbine engines described and / or claimed herein may or may not be provided with a variable area nozzle (VAN). Such a variable area nozzle may allow the outlet area of ​​the bypass duct to vary during use. The general principles of the present disclosure may be applicable to engines with or without a VAN.

[0047] The fans of the gas turbines described and / or claimed herein may have any desired number of fan blades, such as 14, 16, 18, 20, 22, 24, or 26 fan blades.

[0048] The cruise condition used herein has a conventional meaning and will be readily understood by a person skilled in the art. Thus, for a given gas turbine engine for an aircraft, a person skilled in the art will immediately recognize that the meaning of the cruise condition refers to the operating point of the engine at mid-cruise of a given mission (referred to in the industry as an "economic mission") of the aircraft to which the gas turbine engine is designed to be attached. In this regard, mid-cruise refers to the point in time in the aircraft flight cycle at which 50% of the total fuel burned between the top of the climb and the start of descent has been burned (which can be approximated to the midpoint in time and / or distance between the top of the climb and the start of descent). Thus, the cruise condition defines the following operating point of the gas turbine engine, namely: the thrust provided by the operating point will ensure that the aircraft to which the gas turbine engine is designed to be attached is operated in a steady state (i.e., maintaining a constant altitude and a constant Mach number) during mid-cruise, taking into account the number of engines provided to the aircraft. For example, in the case where the engine is designed to be attached to an aircraft with two engines of the same type, under the cruise condition, the engine provides half of the total thrust required to operate the aircraft in a steady state during mid-cruise.

[0049] In other words, for a given gas turbine engine for an aircraft, cruise conditions are defined as the engine operating point that provides a specified thrust (the specified thrust being the thrust that the given gas turbine engine, in combination with any other engine on the aircraft, needs to provide in steady state operation of the aircraft to which the given gas turbine engine is designed to be attached, at a given mid-cruise Mach number) at mid-cruise atmospheric conditions (defined by the International Standard Atmosphere at mid-cruise altitude according to ISO 2533). For any given gas turbine engine for an aircraft, the mid-cruise thrust, atmospheric conditions, and Mach number are known, and thus the engine operating point at cruise conditions is clearly defined.

[0050] By way of example only, the forward speed at cruise conditions may be anywhere from Mach 0.7 to 0.9, such as Mach 0.75 to 0.85, such as Mach 0.76 to 0.84, such as Mach 0.77 to 0.83, such as Mach 0.78 to 0.82, such as Mach 0.79 to 0.81, such as about Mach 0.8, about Mach 0.85, or within the range of Mach 0.8 to 0.85. Any single speed within these ranges may be part of the cruise condition. For a particular aircraft, the cruise condition may not be within these ranges, such as below Mach 0.7 or above Mach 0.9.

[0051] Merely by way of example, cruising conditions may correspond to standard atmospheric conditions (according to the International Standard Atmosphere, ISA) at an altitude in the range from 10000 m to 15000 m, such as in the range from 10000 m to 12000 m, such as in the range from 10400 m to 11600 m (about 38000 feet), such as in the range from 10500 m to 11500 m, such as in the range from 10600 m to 11400 m, such as in the range from 10700 m (about 35000 feet) to 11300 m, such as in the range from 10800 m to 11200 m, such as in the range from 10900 m to 11100 m, such as about 11000 m. Cruising conditions may correspond to standard atmospheric conditions at any given altitude within these ranges.

[0052] By way of example only, a cruise condition may correspond to an operating point of the engine that provides a known desired thrust level (e.g., a value in the range of 30 kN to 35 kN) at a forward Mach number of 0.8 and standard atmospheric conditions (according to International Standard Atmosphere) at an altitude of 38,000 feet (11,582 m). By way of further example only, a cruise condition may correspond to an operating point of the engine that provides a known desired thrust level (e.g., a value from 50 kN to 65 kN) at a forward Mach number of 0.85 and standard atmospheric conditions (according to International Standard Atmosphere) at an altitude of 35,000 feet (10,668 m).

[0053] When used, the gas turbine engines described and / or claimed herein may be operated at cruise conditions defined elsewhere herein. Such cruise conditions may be determined by the cruise conditions (e.g., mid-cruise conditions) of an aircraft to which at least one (e.g., 2 or 4) gas turbine engines may be installed to provide propulsive thrust.

[0054] According to one aspect, there is provided an aircraft comprising a gas turbine engine as described and / or claimed herein. An aircraft according to this aspect is an aircraft to which the gas turbine engine has been designed to be attached. Thus, the cruise condition according to this aspect corresponds to the mid-cruise of an aircraft as defined elsewhere herein.

[0055] According to one aspect, there is provided a method of operating a gas turbine engine as described and / or claimed herein. The operation may be at cruise conditions (eg, in terms of thrust, atmospheric conditions, and Mach number) as defined elsewhere herein.

[0056] According to one aspect, there is provided a method of operating an aircraft comprising a gas turbine engine as described and / or claimed herein. The operation according to this aspect may include (or may be) operation at a mid-cruise of the aircraft as defined elsewhere herein.

[0057] Figure 1 A gas turbine engine 10 having a main axis of rotation 9 is shown. The engine 10 includes an air intake 12 and a propulsion fan 23, which produces two air flows: a core air flow A and a bypass air flow B. The gas turbine engine 10 includes a core 11 that receives the core air flow A. The engine core 11 includes an axial 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 exhaust nozzle 20. The engine compartment 21 surrounds the gas turbine engine 10 and defines a bypass duct 22 and a bypass exhaust nozzle 18. The bypass air flow B flows through the bypass duct 22. The fan 23 is attached to the low-pressure turbine 19 via a shaft 26 and an epicyclic gearbox 30 and is driven thereby.

[0058] In use, the core air stream A is accelerated and compressed by the low pressure compressor 14 and introduced into the high pressure compressor 15 where further compression occurs. The compressed air discharged from the high pressure compressor 15 is introduced into the combustion device 16 where the compressed air is mixed with fuel and the mixture is combusted. The resulting hot combustion products then expand through and thereby drive the high pressure turbine 17 and the low pressure turbine 19 before being discharged through the nozzle 20 to provide some propulsive thrust. The high pressure turbine 17 drives the high pressure compressor 15 via a suitable interconnecting shaft 27. The fan 23 typically provides the majority of the propulsive thrust. The epicyclic gearbox 30 is a reduction gearbox.

[0059] exist Figure 2 An exemplary arrangement for a geared fan gas turbine engine 10 is shown in FIG. Figure 1 ) drive shaft 26, which is coupled to a sun wheel or sun gear 28 of an epicyclic gear arrangement structure 30. Radially outwardly of the sun gear 28 and intermeshing therewith are a plurality of planet gears 32 coupled together by a planet gear carrier 34. The planet gear carrier 34 constrains the planet gears 32 to travel synchronously around the sun gear 28 while enabling each planet gear 32 to rotate about its own axis. The planet gear carrier 34 is coupled to the fan 23 via a connecting rod 36 to drive its rotation about the engine axis 9. Radially outwardly of the planet gears 32 and intermeshing therewith is a ring gear or ring gear 38, which is coupled to the stationary support structure 24 via a connecting rod 40.

[0060] It should be noted that the terms "low-pressure turbine" and "low-pressure compressor" used in this article can mean the lowest pressure turbine stage and the lowest pressure compressor stage (i.e., excluding the fan 23), respectively, and / or the turbine stage and the compressor stage connected together by the interconnecting shaft 26 having the lowest speed in the engine (i.e., excluding the gearbox output shaft driving the fan 23). In some documents, the "low-pressure turbine" and "low-pressure compressor" referred to in this article may be alternatively referred to as an "intermediate pressure turbine" and an "intermediate pressure compressor". In the case of using these alternative names, the fan 23 may be referred to as the first compression stage or the lowest pressure compression stage.

[0061] exist Figure 3 The epicyclic gearbox 30 is shown in more detail as an example in FIG. The sun gear 28, the planetary gears 32 and the ring gear 38 each include teeth around their periphery to intermesh with the other gears. However, for clarity, the epicyclic gearbox 30 is shown in FIG. Figure 3 Only an exemplary portion of the teeth is shown. Four planetary gears 32 are shown, but it will be appreciated by those skilled in the art that more or fewer planetary gears 32 may be provided within the scope of the claimed invention. Practical applications of the planetary epicyclic gearbox 30 typically include at least three planetary gears 32.

[0062] exist Figure 2 and Figure 3 The epicyclic gearbox 30 shown as an example in FIG. 1 is a planetary type, in which the planet gear carrier 34 is coupled to the output shaft via a connecting rod 36, with the ring gear 38 being fixed. However, any other suitable type of epicyclic gearbox 30 may be used. As a further example, the epicyclic gearbox 30 may be a star arrangement in which the planet gear carrier 34 remains fixed, allowing the ring gear (or annular gear) 38 to rotate. In this arrangement, the fan 23 is driven by the ring gear 38. As a further alternative example, the gearbox 30 may be a differential gearbox in which both the ring gear 38 and the planet gear carrier 34 are allowed to rotate.

[0063] It should be understood that Figure 2 and Figure 3 The arrangement shown in is by way of example only, and various alternatives are within the scope of the present disclosure. By way of example only, any suitable arrangement may be used to position the gearbox 30 in the engine 10 and / or to connect the gearbox 30 to the engine 10. As a further example, the connections (such as the gearbox 30 and the other parts of the engine 10, such as the input shaft 26, the output shaft, and the fixed structure 24) between the gearbox 30 and the engine 10 may be such as to prevent the gearbox 30 from being damaged. Figure 2The connecting rods 36, 40 in the example may have any desired degree of stiffness or flexibility. As a further example, any suitable bearing arrangement may be used between the rotating and stationary parts of the engine (e.g., between the input and output shafts of the gearbox and a fixed structure such as a gearbox housing), and the present disclosure is not limited to Figure 2 For example, where the gearbox 30 has a star arrangement (as described above), those skilled in the art will readily appreciate that the arrangement and bearing positions of the output and support rods will generally be the same as in Figure 2 are different from those shown as examples.

[0064] Thus, the present disclosure extends to gas turbine engines having any arrangement of gearbox styles (eg, radial or planetary), support structures, input and output shaft arrangements, and bearing locations.

[0065] Optionally, the gearbox may drive additional and / or alternative components (eg, an intermediate-pressure compressor and / or a booster compressor).

[0066] Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. For example, such engines may have alternative numbers of compressors and / or turbines, and / or alternative numbers of interconnecting shafts. As a further example, Figure 1 The gas turbine engine shown in has split flow nozzles 18, 20, which means that the airflow through the bypass duct 22 has its own nozzle 18, which is separate from the engine core nozzle 20 and is located radially outside the engine core nozzle 20. However, this is not limiting, and any aspect of the present disclosure may also be applied to the following engine in which the airflow through the bypass duct 22 and the airflow through the engine 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 flow or split flow) may have a fixed or variable area.

[0067] The geometry of the gas turbine engine 10 or its components is defined by a conventional axis system including an axial direction (which is aligned with the axis of rotation 9), a radial direction (in the Figure 1 in the bottom-to-top direction) and in the surrounding direction (perpendicular to Figure 1 view). The axial, radial, and circumferential directions are perpendicular to each other.

[0068] Figure 4A schematic diagram of an epicyclic gear system 100 according to some embodiments of the present disclosure is provided. The epicyclic gear system 100 can be a compound planetary gear system. A sun gear 101 is coupled to and driven by a first rotatable shaft 103. The sun gear 101 engages one or more planetary gears 105 such that rotation of the sun gear 101 causes the one or more planetary gears 105 to rotate. The planetary gears 105 can be planetary gears such that the planetary gears 105 rotate about an axis that is fixed relative to the axis of rotation of the sun gear 101.

[0069] Each of the one or more planetary gears 105 engages a ring gear 107. The ring gear 107 is coupled to a second rotatable shaft 109 via a ring gear hub 108. Thus, rotation of the first rotatable shaft 103 drives rotation of the second rotatable shaft 109 via rotation of the sun gear 101, the one or more planetary gears 105, and the ring gear 107. In some embodiments, the first rotatable shaft 103 may be a turbine shaft (i.e., a high or low speed spool) of a turbine engine, and the second rotatable shaft 109 may be a fan shaft or fan rotor.

[0070] Figure 5 A detailed schematic diagram of a housing assembly 111 of an epicyclic gear system 100 according to some embodiments of the present disclosure is provided. Each of the one or more planetary gears 105 includes a cylindrical gear shaft 123, a sun gear engagement gear 125, and a ring gear engagement gear 127. The sun gear engagement gear 125 and the ring gear engagement gear 127 can be carried by the cylindrical gear shaft 123. Each of the one or more planetary gears 105 is carried by the housing assembly 111. The planetary gears 105 can be compound star gears of the epicyclic gear system 100.

[0071] The housing assembly 111 may include a front housing member 113 and a rear housing member 115. In some embodiments, the housing assembly 111 further includes an intermediate housing member 114. One or more of the housing members 113, 114, 115 may be joined together. The front housing member 113 and the rear housing member 115 each define a plurality of gear shaft pockets 116 having cylindrical walls 120. The intermediate housing member 114 may define a plurality of holes 118.

[0072] The cylindrical gear shaft 123 of the planetary gear 105 can have a front end 141 disposed in one of the plurality of gear shaft pockets 116 formed by the front housing member 113. The cylindrical gear shaft 123 of the same planetary gear 105 can have a rear end 142 disposed in one of the plurality of gear shaft pockets 116 formed by the rear housing member 115. The cylindrical gear shaft 123 can be disposed in each gear shaft pocket 116 coaxially with the cylindrical wall 120 of the gear shaft pocket 116. The cylindrical gear shaft 123 can extend through the hole 118 defined by the intermediate housing member 114. The sun gear meshing gear 125 and the ring gear meshing gear 127 of the planetary gear 105 can be carried by the gear shaft 123 between the front end 141 and the rear end 142.

[0073] The housing assembly 111 may further include a bearing assembly 117. The housing assembly 111 may include a front bearing assembly and a rear bearing assembly. The bearing assembly 117 may include a bearing. For example, the front bearing 119 may be disposed on at least a portion of the front end 141 of the gear shaft 123, and the rear bearing 121 may be disposed on at least a portion of the rear end 142 of the gear shaft 123. Each bearing 119, 121 may rotatably carry the planetary gear 105. Each bearing 119, 121 may be a roller element bearing.

[0074] During operation of the epicyclic gear system 100, the components of the system 100 as described above and including the attached gear carrier assembly, housing, and bearings may move relative to each other. Even small changes in the relative positioning of one component to another may have a significant impact on the performance of the system 100. For example, misalignment of meshing gear teeth and / or bearings may cause uneven gear and / or bearing loading and lead to degradation or damage to the gear teeth. For example, misalignment of meshing gear teeth and / or bearings may cause uneven gear and / or bearing loading and lead to degradation or damage to the gear teeth and reduce bearing life and bearing stability.

[0075] Of particular concern is the fore-aft alignment of the gear shaft 123 of each planetary gear 105. Since each planetary gear 105 is carried by a gear shaft 123 that is partially disposed within a gear shaft recess 116 of the front housing member 113 and a gear shaft recess 116 of the rear housing member 115, relative movement or changes in relative positioning between the front housing member 113 and the rear housing member 115 may result in misalignment of the planetary gear 105. Similarly, relative movement or changes in relative positioning between the intermediate housing member 114 and one or both of the front housing member 113 and the rear housing member 115 may result in misalignment of the planetary gear 105.

[0076] This misalignment may in turn lead to uneven load distribution between the planet gears 105, gear degradation, and reduced useful life of the planet gears 105 and / or the planet bearings 119, 121. Factors that may cause planet gear misalignment include misaligned forces between the front bearing 119 and the rear bearing 121, manufacturing inaccuracies in the positions of the gear shaft pockets 116 and holes 118, the ability to reassemble the front and rear housings to the same positions as they were machined, gear tolerances, and inflexibility and / or relative rigidity between each of the housing components 113, 114, 115.

[0077] Therefore, the present disclosure relates to systems and methods for improving and maintaining alignment of planetary gears in an epicyclic gear system. More specifically, the present disclosure relates to a planetary gear housing assembly for an epicyclic gear system having a front planetary gear carrier assembly, a rear planetary gear carrier assembly, a reinforcement member positioned between the front planetary gear carrier assembly and the rear planetary gear carrier assembly, and a plurality of planetary gears, each of which is carried by the front planetary gear carrier assembly and the rear planetary gear carrier assembly. The reinforcement member can achieve a desired stiffness ratio between the front planetary gear carrier assembly and the rear planetary gear carrier assembly.

[0078] like Figure 4 As shown in FIG. 8 , the planetary gear housing assembly 111 may include: a rear planetary gear carrier assembly 131 ; a front planetary gear carrier assembly 161 ; a reinforcement member 171 ; and a plurality of planetary gears 105 , each of which is carried by the rear planetary gear carrier assembly 131 and the front planetary gear carrier assembly. Figure 6 is an isometric view of a front planetary gear carrier assembly, a reinforcement member, and a rear planetary gear carrier assembly of a planetary gear housing assembly according to some embodiments of the present disclosure. Figure 7 is a partial cross-sectional view of a reinforcement member coupled between a front planetary gear carrier assembly and a rear planetary gear carrier assembly of a planetary gear housing assembly according to some embodiments. Fig. 8A and Figure 8B An axonometric view of a reinforcement member according to some embodiments is provided.

[0079] The rear planetary gear carrier assembly 131 may include one or both of the intermediate housing member 114 and the rear housing member 115. The rear planetary gear carrier assembly 131 may include a rear flange 136. The rear flange 136 may be the intermediate housing member 114, the rear housing member 115, or another flange member. The rear flange 136 may include more than one flange, such as Figure 6, having a first rear flange 136A and a second rear flange 136B. The rear flange 136 may define a central aperture 132 and a plurality of gear shaft pockets 137 that surround the central aperture 132 and are positioned radially outward of the central aperture 132. Each gear shaft pocket 116 may have a cylindrical wall 138. In some embodiments, the rear flange 136 may further include a radially outer mounting surface 139 for coupling the rear planetary gear carrier assembly 131 to the engine housing.

[0080] The rear planetary gear carrier assembly 131 may also include an annular mounting flange 133. The annular mounting flange 133 may be positioned forward of and coaxial with the central aperture 132. The annular mounting flange 133 may extend generally perpendicularly from the rear flange 136. The annular mounting flange 133 may form a forward facing mounting surface 134, which may include a curved structure.

[0081] The front planetary gear carrier assembly 161 may include a front flange 162 and an annular mounting flange 143. The front planetary gear carrier assembly 161 may be the front housing member 113. The front flange 162 may define a central aperture 144 and a plurality of gear shaft pockets 145 that surround the central aperture 144 and are positioned radially outward of the central aperture 144. Each gear shaft pocket 145 may have a cylindrical wall 146. The annular mounting flange 143 may be positioned rearward of the central aperture 144 and coaxial with the central aperture 144. The annular mounting flange 143 may form a rearwardly facing mounting surface 147 that may include a curved structure. The annular mounting flange 143 may extend substantially vertically from the front flange 162.

[0082] A plurality of planetary gears 105 may be carried by the front planetary gear carrier assembly 161 and the rear planetary gear carrier assembly 131. Each of the planetary gears 105 may include a cylindrical shaft 123 having a front end 141 disposed in a gear shaft pocket 145 of the front flange 162. The front end 141 may be disposed in the gear shaft pocket 145 and coaxial with a cylindrical wall 146 defining the gear shaft pocket 145. The cylindrical shaft may have a rear end 142 disposed in a gear shaft pocket 137 of the rear flange 136 and may be disposed in the gear shaft pocket 137 coaxial with a cylindrical wall 138.

[0083] Each planet gear 105 may further include one or more gears carried by the cylindrical shaft 123 between the front end 141 and the rear end 142. These gears may be, for example, a sun gear engagement portion 125 of the planet gear 105 and / or a ring gear engagement portion 127 of the planet gear 105.

[0084] The planetary gear housing assembly 111 and / or the front planetary gear carrier assembly 161 can further include a reinforcement member 171. The reinforcement member 171 can include an annular body 172 defining a central aperture 173. The reinforcement member 171 can further include a plurality of radial flanges 174 extending radially outward from the annular body 172. Each radial flange 174 can at least partially define a gear-facing surface 175. In some embodiments, the reinforcement member 171 includes seven radial flanges 174 and defines seven gear-facing surfaces 175.

[0085] The reinforcement member 171 can be positioned between the rear planetary gear carrier assembly 131 and the front planetary gear carrier assembly 161. In some embodiments, the reinforcement member 171 can abut against one or both of the front flange 162 and the rear flange 136. In some embodiments, the reinforcement member 171 is coupled to one or both of the front flange 162 and the rear flange 136 by a plurality of bolts, pins or other fasteners 176.

[0086] When the epicyclic gear system 100 is fully assembled, the corresponding planet gears 105 can be carried by the front flange 162 and the rear flange 136, and can have a gear portion, such as the ring gear engagement portion 127, positioned adjacent to the gear-facing surface 175 of the reinforcement member 171. The reinforcement member 171 can be coupled between the front flange 162 and the rear flange 136 to increase the torsional stiffness of the front planet gear carrier assembly 161 relative to the rear planet gear carrier assembly 131.

[0087] The epicyclic gear system 100 may be an epicyclic gear system of a gas turbine engine. The gas turbine engine may include an engine casing 177, a portion of which is located at Figure 7 177 to define a rear torsional stiffness. The front flange 162 may be coupled to the rear flange 136 to define a front torsional stiffness. The front flange 162 may be coupled to the rear flange 136, for example, with the forward-facing mounting surface 134 of the mounting flange 133 positioned relative to the rearward-facing mounting surface 147 of the mounting flange 143. The front flange 162 may be coupled to the rear flange 136 via a static flex joint.

[0088] In some embodiments, the front torsional stiffness may be between 60% and 80% of the rear torsional stiffness. Since the radius at which the rear flange 136 is mounted to the rear housing 177 is greater than the radius at which the front flange 162 is mounted to the rear flange 136, the rear torsional stiffness may be greater. More generally, the front torsional stiffness may be between 50% and 90% of the rear torsional stiffness. In other embodiments, the front torsional stiffness may be between 65% and 75% of the rear torsional stiffness.

[0089] Fig. 99 is a flow chart of a method 900 for reducing relative motion between static components of an epicyclic gear system according to some embodiments of the present disclosure. The method 900 begins at block 901. The steps of the method 900 presented at blocks 901 to 919 may be performed as follows: Fig. 9 One or more steps in method 900 may not be performed.

[0090] At block 903, a static front planetary gear carrier assembly 161 and a static rear planetary gear carrier assembly 131 may be provided. The front planetary gear carrier assembly 161 may include a front flange 162 defining a central aperture 144 and a plurality of gear shaft pockets 145 positioned around the periphery of the central aperture 144. The front planetary gear carrier assembly 161 may also include an annular mounting flange 143 extending from the front flange 162, the annular mounting flange 143 positioned rearwardly of the central aperture 144 and coaxially with the central aperture 144. The mounting flange 143 may form a rearwardly facing mounting surface 147.

[0091] The rear planetary gear carrier assembly 131 may include a rear flange 136 defining a central aperture 132 and a plurality of gear shaft pockets 137 surrounding the circumference of the central aperture 132 and positioned radially outward of the central aperture 132. The rear planetary gear carrier assembly 131 may also include an annular mounting flange 133 extending from the rear flange 136 and positioned forward of and coaxial with the central aperture 132. The mounting flange 133 may form a forward facing mounting surface 134.

[0092] At block 905, a reinforcement member 171 may be positioned between the rear planetary gear carrier assembly 131 and the front planetary gear carrier assembly 161. The reinforcement member 171 may include an annular body 172 defining a central aperture 173 and a plurality of radial flanges 174 extending radially outward from the annular body 172. Each of the plurality of radial flanges 174 may partially define a gear-facing surface 175.

[0093] At block 907 , the bearings 119 , 121 may be at least partially positioned in the gear shaft pockets 145 , 137 of the front planetary gear carrier assembly 161 and / or the rear planetary gear carrier assembly 131 .

[0094] At block 909, a planet gear 105 of the plurality of planet gears 105 may be positioned in each of a plurality of axially aligned gear shaft pocket pairs formed between pockets 145, 137 of the front planet gear carrier assembly 161 and / or the rear planet gear carrier assembly 131. Each planet gear 105 may include a cylindrical shaft 123 having a front end 141 disposed in one of the gear shaft pockets 145 of the front planet gear carrier assembly 161 and coaxial with a cylindrical wall 146 of the pocket 145, and a rear end 142 disposed in one of the gear shaft pockets 137 of the rear planet gear carrier assembly 131 and coaxial with a cylindrical wall 138 of the pocket 137. The planet gear 105 may also include one or more gears 125, 127 carried by the shaft 123 between the front end 141 and the rear end 142.

[0095] At box 911 , a portion of the cylindrical shaft 123 of the planet gear 105 may be carried by the bearings 119 , 121 .

[0096] At block 913 , the method may also include positioning the mounting surface 134 of the rear planetary gear carrier assembly 131 relative to the mounting surface 147 of the front planetary gear carrier assembly 161 .

[0097] At block 915 , the front planetary gear carrier assembly 161 may be coupled to the rear planetary gear carrier assembly 131 .

[0098] At block 917 , the cylindrical shaft 123 of each planet gear 105 may rotate. The rotation may be driven by the sun gear 101 of the compound planetary gear assembly 100 .

[0099] Method 900 ends at block 919 .

[0100] The presently disclosed systems and methods provide numerous advantages over prior art systems. By providing a reinforcing member positioned between and coupling the front and rear planetary gear carrier assemblies, the disclosed planetary gear housing assembly reduces fore-aft misalignment of the planetary gear shafts caused by relative motion between the front and rear planetary gear carrier assemblies. The rear planetary gear carrier assembly can be rigidly mounted to the engine housing at the outer diameter of the rear flange. Because the front flange can be mounted to the rear flange at the inner diameter, the front-to-rear connection of the flanges can be inherently less rigid, thereby allowing greater torsional deflection under equal bearing reaction loads.

[0101] By coupling the rear planetary gear carrier assembly and the front planetary gear carrier assembly with a reinforcing member between the rear and front planetary gear carrier assemblies, the front planetary gear carrier assembly can be held to the rear planetary gear carrier assembly with less relative motion between the two than with a standard coupling. While a typical epicyclic gear system may have a front torsional stiffness that is 25%-40% of the rear torsional stiffness, the disclosed reinforcing member provides an increase in the front torsional stiffness to 60%-80% of the rear torsional stiffness. Less relative motion is advantageous during assembly and during operation of the epicyclic gear system.

[0102] The present disclosure may be used in conjunction with the disclosure of one or more of the related applications listed above. In particular, the present disclosure may be used in conjunction with "Static Curvic Joint for an Epicyclical Gear System Housing Assembly". Static curvature joints ensure hole-to-hole alignment during machining and assembly, but may reduce front torsional stiffness. The reinforcing member described herein may offset this reduction in front torsional stiffness, making the combination of a static curvature joint and a reinforcing member in an epicyclic gear system advantageous. This combination may ensure hole-to-hole alignment during manufacturing, machining, assembly, and operation.

[0103] While examples are illustrated and described herein, the embodiments are not limited to the details shown since various modifications and structural changes may be made in the embodiments by one skilled in the art within the scope and breadth of equivalents of the claims.

Claims

1. A planetary gear housing assembly in an epicyclic gear assembly, comprising: a rear planetary gear carrier assembly, the rear planetary gear carrier assembly comprising a rear flange defining a central aperture; and a plurality of gear shaft pockets surrounding a circumference of the central aperture and positioned radially outward of the central aperture, each pocket having a cylindrical wall; a front planetary gear carrier assembly, the front planetary gear carrier assembly comprising a front flange defining a central aperture; and a plurality of gear shaft pockets surrounding a circumference of the central aperture and positioned radially outward of the central aperture, each pocket having a cylindrical wall; a plurality of planetary gears, each of the plurality of planetary gears comprising a cylindrical shaft, the cylindrical shaft having: a front end portion disposed in a gear shaft recess of the front planetary gear carrier assembly and coaxial with the cylindrical wall of the recess; a rear end portion disposed in a gear shaft recess of the rear planetary gear carrier assembly and coaxial with the cylindrical wall of the recess; and one or more gears carried by the shaft between the front end and the rear end; as well as A reinforcement member, the reinforcement member being positioned between the rear planetary gear carrier assembly and the front planetary gear carrier assembly, the reinforcement member comprising: an annular body defining a central aperture; and a plurality of radial flanges extending radially outward from the annular body, Each radial flange of the plurality of radial flanges partially defines a gear-facing surface.

2. The planetary gear housing assembly according to claim 1, wherein: The rear planetary gear carrier assembly is coupled to the front planetary gear carrier assembly.

3. The planetary gear housing assembly according to claim 2: in, The rear planetary gear carrier assembly also includes an annular mounting flange extending from the rear flange, the annular mounting flange being positioned forward of and coaxial with the central aperture, and the mounting flange forming a forward facing mounting surface; wherein the front planetary gear carrier assembly further comprises an annular mounting flange extending from the front flange, the annular mounting flange being positioned rearward of the central aperture and coaxial with the central aperture, and the mounting flange forming a rearwardly facing mounting surface; and Wherein the mounting surfaces are positioned relative to each other, thereby coupling the rear planetary gear carrier assembly and the front planetary gear carrier assembly.

4. The planetary gear housing assembly according to claim 1, wherein: The shaft and the gear form a compound star gear in an epicyclic gear system.

5. The planetary gear housing assembly according to claim 1, wherein: The epicyclic gear assembly is part of a gas turbine engine having an engine casing, and wherein the rear flange is coupled to the engine casing to define a rear torsional stiffness, and the front flange is coupled to the rear planetary gear carrier assembly to define a front torsional stiffness, and wherein the front torsional stiffness is between 50% and 90% of the rear torsional stiffness.

6. The planetary gear housing assembly according to claim 5, wherein: The front torsional stiffness is between 60% and 80% of the rear torsional stiffness.

7. The planetary gear housing assembly according to claim 5, wherein: The front torsional stiffness is between 65% and 75% of the rear torsional stiffness.

8. The planetary gear housing assembly according to claim 1, wherein: The reinforcement member includes seven gear-facing surfaces.

9. The planetary gear housing assembly of claim 51, wherein: The rear flange includes a radially outer mounting surface for mounting the planetary gear housing assembly to the engine casing.

10. A gas turbine engine for an aircraft, comprising: an engine core including a turbine, a compressor, and a spindle connecting the turbine to the compressor; a fan, the fan being located upstream of the engine core, the fan comprising a plurality of fan blades; as well as a gearbox receiving input from the spindle and outputting drive to the fan to drive the fan at a speed lower than the spindle, wherein the gearbox has a planetary gear housing assembly, the planetary gear housing assembly comprising: a rear planetary gear carrier assembly comprising a rear flange defining a central aperture; and a plurality of gear shaft pockets located around and radially outward of the central aperture, each pocket having a cylindrical wall; a front planetary gear carrier assembly comprising a front flange defining a central aperture; and a plurality of gear shaft pockets located around and radially outward of the central aperture, each pocket having a cylindrical wall; a plurality of planetary gears, each of the plurality of planetary gears comprising a cylindrical shaft having: a front end portion disposed in a gear shaft recess of the front planetary gear carrier assembly and coaxial with the cylindrical wall of the recess; a rear end portion disposed in a gear shaft recess of the rear planetary gear carrier assembly and coaxial with the cylindrical wall of the recess; and one or more gears carried by the shaft between the front end portion and the rear end portion; and A reinforcing member, the reinforcing member being positioned between the rear planetary gear carrier assembly and the front planetary gear carrier assembly, and the reinforcing member being against the rear planetary gear carrier assembly and the front planetary gear carrier assembly, the reinforcing member comprising an annular body defining a central orifice; and a plurality of radial flanges extending radially outward from the annular body, each of the plurality of radial flanges partially defining a gear-facing surface.

11. The gas turbine engine according to claim 10, wherein: Each of the plurality of planetary gears includes a sun gear engaging gear and a ring gear engaging gear carried by the shaft between the front end portion and the rear end portion.

12. The gas turbine engine according to claim 10, wherein: The shaft and the gear form a compound star gear in an epicyclic gear system.

13. The gas turbine engine according to claim 10, wherein: The gear box further includes a roller element bearing disposed on at least a portion of one or both of the front end portion and the rear end portion of the gear shaft.

14. The gas turbine engine according to claim 10, wherein: The rear planetary gear carrier assembly defines a rear torsional stiffness, and the front planetary gear carrier assembly defines a front torsional stiffness, and wherein the front torsional stiffness is between 65% and 75% of the rear torsional stiffness.

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