EP3659746A1 - Meulage d'alésages cylindriques - Google Patents

Meulage d'alésages cylindriques Download PDF

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Publication number
EP3659746A1
EP3659746A1 EP19205047.4A EP19205047A EP3659746A1 EP 3659746 A1 EP3659746 A1 EP 3659746A1 EP 19205047 A EP19205047 A EP 19205047A EP 3659746 A1 EP3659746 A1 EP 3659746A1
Authority
EP
European Patent Office
Prior art keywords
grinding
workpiece
gear
bore
axis
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19205047.4A
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German (de)
English (en)
Inventor
Sufyan Khan
David Curtis
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rolls Royce PLC
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Rolls Royce PLC
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Filing date
Publication date
Application filed by Rolls Royce PLC filed Critical Rolls Royce PLC
Publication of EP3659746A1 publication Critical patent/EP3659746A1/fr
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B5/00—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor
    • B24B5/02—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor involving centres or chucks for holding work
    • B24B5/06—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor involving centres or chucks for holding work for grinding cylindrical surfaces internally
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B5/00—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor
    • B24B5/01—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor for combined grinding of surfaces of revolution and of adjacent plane surfaces on work
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B5/00—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor
    • B24B5/02—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor involving centres or chucks for holding work
    • B24B5/14—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor involving centres or chucks for holding work for grinding conical surfaces, e.g. of centres

Definitions

  • the present disclosure relates to a method of grinding the internal bore of a gear, for example a gear for use in a gas turbine engine.
  • a known method of reducing the mass of the gears involves grinding the internal bore to reduce its thickness. This, grinding also increases the bore accuracy, which provides an improved surface for the bearings to run on. Achieving accurate bearing surfaces results in an improved fit for the bearings themselves, which in turn reduces any imbalance in the system. Cylindrical grinders are able to perform this process. However, using cylindrical grinding machines results in a large number of manufacturing steps; this in turn increases the complexity of manufacturing the part. This is because cylindrical grinders are limited to a single function, but are much stiffer than other tools as typically they have fewer axes of movement. This conflicting set of features results in cylindrical grinders having the advantage of high conformance, but being limited in their use, as other machines are required to produce the other parts of the gear, such as the teeth.
  • the present disclosure provides a method of reducing the thickness of a bore of a cylindrical workpiece for use as a gear, and a gas turbine engine including a gear that has a central bore ground by that method, as set out in the appended claims.
  • the present disclosure provides a method of reducing the thickness of a bore of a cylindrical workpiece for use as a gear; the method comprising the steps of:
  • the internal bore may be ground on a standard 5-axis machine.
  • the external teeth of the gear can be ground on the same machine; this reduces the number of set up steps that are required for the gear, which reduces production time.
  • the other operations such as turning and milling can be performed all on the same machine.
  • this leads to a greater conformance as the errors created by changing and resetting equipment are not present when performing multiple stages on the same piece of equipment. This is because the operator does not have to setup the datums again for each of the different pieces of equipment.
  • the axis of rotation of the grinding wheel may be located from 90 degrees to 180 degrees, in the direction of rotation of the grinding wheel, from a plane that extends vertically through the workpiece when it is mounted in the grinding machine.
  • the grinding machine for grinding the bore of the cylindrical workpiece may be performed on a 5-axis machining centre.
  • the bore may be rotated about a C-axis of the machine whilst the grinding wheel position is maintained stationary.
  • Gear teeth may be ground on an external surface of the cylindrical workpiece using the same grinding machining centre.
  • the faces of the cylindrical workpieces may be ground using the same grinding machining.
  • the gear may be one of a planetary, sun, parallel axis or helical gear.
  • Coolant may be provided to the grinding wheel and/or workpiece whilst in use to cool the grinding wheel.
  • Coolant may be applied to the grinding wheel and/or workpiece via a flat head nozzle.
  • Coolant may be applied to the grinding wheel and/or workpiece in a range from 50 to 150 bar.
  • the internal bore may be reduced in thickness in three sages: a roughing stage; a semi-finishing stage; and a finishing stage.
  • the grinding process may be completed in fewer than 20 roughing steps within the roughing stage, fewer than 10 semi finishing steps within the semi finishing stage, and fewer than 5 finishing steps in the finishing stage.
  • the present disclosure provides a gas turbine engine that includes a gear that has a central bore ground by the above method.
  • Such a gas turbine engine may comprise an engine core comprising a turbine, a combustor, a compressor, and a core shaft connecting the turbine to the compressor.
  • a gas turbine engine may comprise a fan (having fan blades) located upstream of the engine core.
  • the gas turbine engine may comprise a gearbox that receives an input from the core shaft and outputs drive to the fan so as to drive the fan at a lower rotational speed than the core shaft.
  • the input to the gearbox may be directly from the core shaft, or indirectly from the core shaft, for example via a spur shaft and/or gear.
  • the core shaft may rigidly connect the turbine and the compressor, such that the turbine and compressor rotate at the same speed (with the fan rotating at a lower speed).
  • the gas turbine engine as described and/or claimed herein may have any suitable general architecture.
  • the gas turbine engine may have any desired number of shafts that connect turbines and compressors, for example one, two or three shafts.
  • the turbine connected to the core shaft may be a first turbine
  • the compressor connected to the core shaft may be a first compressor
  • the core shaft may be a first core shaft.
  • the engine core may further comprise a second turbine, a second compressor, and a second core shaft connecting the second turbine to the second compressor.
  • the second turbine, second compressor, and second core shaft may be arranged to rotate at a higher rotational speed than the first core shaft.
  • the second compressor may be positioned axially downstream of the first compressor.
  • the second compressor may be arranged to receive (for example directly receive, for example via a generally annular duct) flow from the first compressor.
  • the gearbox may be arranged to be driven by the core shaft that is configured to rotate (for example in use) at the lowest rotational speed (for example the first core shaft in the example above).
  • the gearbox may be arranged to be driven only by the core shaft that is configured to rotate (for example in use) at the lowest rotational speed (for example only be the first core shaft, and not the second core shaft, in the example above).
  • the gearbox may be arranged to be driven by any one or more shafts, for example the first and/or second shafts in the example above.
  • a combustor may be provided axially downstream of the fan and compressor(s).
  • the combustor may be directly downstream of (for example at the exit of) the second compressor, where a second compressor is provided.
  • the flow at the exit to the combustor may be provided to the inlet of the second turbine, where a second turbine is provided.
  • the combustor may be provided upstream of the turbine(s).
  • each compressor may comprise any number of stages, for example multiple stages.
  • Each stage may comprise a row of rotor blades and a row of stator vanes, which may be variable stator vanes (in that their angle of incidence may be variable).
  • the row of rotor blades and the row of stator vanes may be axially offset from each other.
  • each turbine may comprise any number of stages, for example multiple stages.
  • Each stage may comprise a row of rotor blades and a row of stator vanes.
  • the row of rotor blades and the row of stator vanes may be axially offset from each other.
  • Each fan blade may be defined as having a radial span extending from a root (or hub) at a radially inner gas-washed location, or 0% span 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 on the order of) any of: 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 in an inclusive range bounded by any two of the values in the previous sentence (i.e.
  • the values may form upper or lower bounds). These ratios may commonly be referred to as the hub-to-tip ratio.
  • the radius at the hub and the radius at the tip may both be measured at the leading edge (or axially forwardmost) part of the blade.
  • the hub-to-tip ratio refers, of course, to the gas-washed portion of the fan blade, i.e. the portion radially outside any platform.
  • the radius of the fan may be measured between the engine centreline and the tip of a fan blade at its leading edge.
  • the fan diameter (which may simply be twice the radius of the fan) may be greater than (or on the order of) any of: 250 cm (around 100 inches), 260 cm, 270 cm (around 105 inches), 280 cm (around 110 inches), 290 cm (around 115 inches), 300 cm (around 120 inches), 310 cm, 320 cm (around 125 inches), 330 cm (around 130 inches), 340 cm (around 135 inches), 350cm, 360cm (around 140 inches), 370 cm (around 145 inches), 380 (around 150 inches) cm or 390 cm (around 155 inches).
  • the fan diameter may be in an inclusive range bounded by any two of the values in the previous sentence (i.e. the values may form upper or lower bounds).
  • the rotational speed of the fan may vary in use. Generally, the rotational speed is lower for fans with a higher diameter. Purely by way of non-limitative example, the rotational speed of the fan at cruise conditions may be less than 2500 rpm, for example less than 2300 rpm. Purely by way of further non-limitative example, the rotational speed of the fan at cruise conditions for an engine having a fan diameter in the range of from 250 cm to 300 cm (for example 250 cm to 280 cm) may be in the range of from 1700 rpm to 2500 rpm, for example in the range of from 1800 rpm to 2300 rpm, for example in the range of from 1900 rpm to 2100 rpm.
  • the rotational speed of the fan at cruise conditions for an engine having a fan diameter in the range of from 320 cm to 380 cm may be in the range of from 1200 rpm to 2000 rpm, for example in the range of from 1300 rpm to 1800 rpm, for example in the range of from 1400 rpm to 1600 rpm.
  • the fan In use of the gas turbine engine, the fan (with associated fan blades) rotates about a rotational axis. This rotation results in the tip of the fan blade moving with a velocity U tip .
  • the work done by the fan blades 13 on the flow results in an enthalpy rise dH of the flow.
  • a fan tip loading may be defined as dH/U tip 2 , where dH is the enthalpy rise (for example the 1-D average enthalpy rise) across the fan and U tip is the (translational) velocity of the fan tip, for example at the leading edge of the tip (which may be defined as fan tip radius at leading edge multiplied by angular speed).
  • the fan tip loading at cruise conditions may be greater than (or on the order of) any of: 0.3, 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 being Jkg -1 K -1 /(ms -1 ) 2 ).
  • the fan tip loading may be in an inclusive range bounded by any two of the values in the previous sentence (i.e. the values may form upper or lower bounds).
  • Gas turbine engines in accordance with the present disclosure may have any desired bypass ratio, where the bypass ratio is defined as the ratio of the mass flow rate of the flow through the bypass duct to the mass flow rate of the flow through the core at cruise conditions.
  • the bypass ratio may be greater than (or on the order of) any of the following: 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, or 17.
  • the bypass ratio may be in an inclusive range bounded by any two of the values in the previous sentence (i.e. the values may form upper or lower bounds).
  • the bypass duct may be substantially annular.
  • the bypass duct may be radially outside the core engine.
  • the radially outer surface of the bypass duct may be defined by a nacelle and/or a fan case.
  • the overall pressure ratio of a gas turbine engine as described and/or claimed herein may be defined as the ratio of the stagnation pressure upstream of the fan to the stagnation pressure at the exit of the highest pressure compressor (before entry into the combustor).
  • the overall pressure ratio of a gas turbine engine as described and/or claimed herein at cruise may be greater than (or on the order of) any of the following: 35, 40, 45, 50, 55, 60, 65, 70, 75.
  • the overall pressure ratio may be in an inclusive range bounded by any two of the values in the previous sentence (i.e. the values may form upper or lower bounds).
  • Specific thrust of an engine may be defined as the net thrust of the engine divided by the total mass flow through the engine. At cruise conditions, the specific thrust of an engine described and/or claimed herein may be less than (or on the order of) any of the following: 110 Nkg -1 s, 105 Nkg -1 s, 100 Nkg -1 s, 95 Nkg -1 s, 90 Nkg -1 s, 85 Nkg -1 s or 80 Nkg -1 s.
  • the specific thrust may be in an inclusive range bounded by any two of the values in the previous sentence (i.e. the values may form upper or lower bounds). Such engines may be particularly efficient in comparison with conventional gas turbine engines.
  • a gas turbine engine as described and/or claimed herein may have any desired maximum thrust.
  • a gas turbine as described and/or claimed herein may be capable of producing a maximum thrust of at least (or on the order of) any of the following: 160kN, 170kN, 180kN, 190kN, 200kN, 250kN, 300kN, 350kN, 400kN, 450kN, 500kN, or 550kN.
  • the maximum thrust may be in an inclusive range bounded by any two of the values in the previous sentence (i.e. the values may form upper or lower bounds).
  • the thrust referred to above may be the maximum net thrust at standard atmospheric conditions at sea level plus 15 degrees C (ambient pressure 101.3kPa, temperature 30 degrees C), with the engine static.
  • the temperature of the flow at the entry to the high pressure turbine may be particularly high.
  • This temperature which may be referred to as TET
  • TET may be measured at the exit to the combustor, for example immediately upstream of the first turbine vane, which itself may be referred to as a nozzle guide vane.
  • the TET may be at least (or on the order of) any of the following: 1400K, 1450K, 1500K, 1550K, 1600K or 1650K.
  • the TET at cruise may be in an inclusive range bounded by any two of the values in the previous sentence (i.e. the values may form upper or lower bounds).
  • the maximum TET in use of the engine may be, for example, at least (or on the order of) any of the following: 1700K, 1750K, 1800K, 1850K, 1900K, 1950K or 2000K.
  • the maximum TET may be in an inclusive range bounded by any two of the values in the previous sentence (i.e. the values may form upper or lower bounds).
  • the maximum TET may occur, for example, at a high thrust condition, for example at a maximum take-off (MTO) condition.
  • MTO maximum take-off
  • a fan blade and/or aerofoil portion of a fan blade described and/or claimed herein may be manufactured from any suitable material or combination of materials.
  • at least a part of the fan blade and/or aerofoil may be manufactured at least in part from a composite, for example a metal matrix composite and/or an organic matrix composite, such as carbon fibre.
  • at least a part of the fan blade and/or aerofoil may be manufactured at least in part from a metal, such as a titanium based metal or an aluminium based material (such as an aluminium-lithium alloy) or a steel based material.
  • the fan blade may comprise at least two regions manufactured using different materials.
  • the fan blade may have a protective leading edge, which may be manufactured using a material that is better able to resist impact (for example from birds, ice or other material) than the rest of the blade.
  • a leading edge may, for example, be manufactured using titanium or a titanium-based alloy.
  • the fan blade may have a carbon-fibre or aluminium based body (such as an aluminium lithium alloy) with a titanium leading edge.
  • a fan as described and/or claimed herein may comprise a central portion, from which the fan blades may extend, for example in a radial direction.
  • the fan blades may be attached to the central portion in any desired manner.
  • each fan blade may comprise a fixture which may engage a corresponding slot in the hub (or disc).
  • a fixture may be in the form of a dovetail that may slot into and/or engage a corresponding slot in the hub/disc in order to fix the fan blade to the hub/disc.
  • the fan blades maybe formed integrally with a central portion.
  • Such an arrangement may be referred to as a blisk or a bling. Any suitable method may be used to manufacture such a blisk or bling.
  • at least a part of the fan blades may be machined from a block and/or at least part of the fan blades may be attached to the hub/disc by welding, such as linear friction welding.
  • variable area nozzle may allow the exit area of the bypass duct to be varied in use.
  • the general principles of the present disclosure may apply to engines with or without a VAN.
  • the fan of a gas turbine as described and/or claimed herein may have any desired number of fan blades, for example 16, 18, 20, or 22 fan blades.
  • cruise conditions may mean cruise conditions of an aircraft to which the gas turbine engine is attached.
  • cruise conditions may be conventionally defined as the conditions at mid-cruise, for example the conditions experienced by the aircraft and/or engine at the midpoint (in terms of time and/or distance) between top of climb and start of decent.
  • the forward speed at the cruise condition may be any point in the range of from Mach 0.7 to 0.9, for example 0.75 to 0.85, for example 0.76 to 0.84, for example 0.77 to 0.83, for example 0.78 to 0.82, for example 0.79 to 0.81, for example on the order of Mach 0.8, on the order of Mach 0.85 or in the range of from 0.8 to 0.85.
  • Any single speed within these ranges may be the cruise condition.
  • the cruise conditions may be outside these ranges, for example below Mach 0.7 or above Mach 0.9.
  • the cruise conditions may correspond to standard atmospheric conditions at an altitude that is in the range of from 10000m to 15000m, for example in the range of from 10000m to 12000m, for example in the range of from 10400m to 11600m (around 38000 ft), for example in the range of from 10500m to 11500m, for example in the range of from 10600m to 11400m, for example in the range of from 10700m (around 35000 ft) to 11300m, for example in the range of from 10800m to 11200m, for example in the range of from 10900m to 11100m, for example on the order of 11000m.
  • the cruise conditions may correspond to standard atmospheric conditions at any given altitude in these ranges.
  • the cruise conditions may correspond to: a forward Mach number of 0.8; a pressure of 23000 Pa; and a temperature of -55 deg C.
  • “cruise” or “cruise conditions” may mean the aerodynamic design point.
  • Such an aerodynamic design point may correspond to the conditions (comprising, for example, one or more of the Mach Number, environmental conditions and thrust requirement) for which the fan is designed to operate. This may mean, for example, the conditions at which the fan (or gas turbine engine) is designed to have optimum efficiency.
  • a gas turbine engine described and/or claimed herein may operate at the cruise conditions defined elsewhere herein.
  • cruise conditions may be determined by the cruise conditions (for example the mid-cruise conditions) of an aircraft to which at least one (for example 2 or 4) gas turbine engine may be mounted in order to provide propulsive thrust.
  • FIG. 1 illustrates a gas turbine engine 10 having a principal rotational axis 9.
  • the engine 10 comprises an air intake 12 and a propulsive fan 23 that generates two airflows: a core airflow A and a bypass airflow B.
  • the gas turbine engine 10 comprises a core 11 that receives the core airflow A.
  • the engine core 11 comprises, in axial flow series, a low pressure compressor 14, a high-pressure compressor 15, combustion equipment 16, a high-pressure turbine 17, a low pressure turbine 19 and a core exhaust nozzle 20.
  • a nacelle 21 surrounds the gas turbine engine 10 and defines a bypass duct 22 and a bypass exhaust 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 gearbox 30.
  • the core airflow 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 exhausted from the high pressure compressor 15 is directed into the combustion equipment 16 where it is mixed with fuel and the mixture is combusted.
  • the resultant hot combustion products then expand through, and thereby drive, the high pressure and low pressure turbines 17, 19 before being exhausted through the core exhaust nozzle 20 to provide some propulsive thrust.
  • the high pressure turbine 17 drives the high pressure compressor 15 by a suitable interconnecting shaft 27.
  • the fan 23 generally provides the majority of the propulsive thrust.
  • the epicyclic gearbox 30 is a reduction gearbox.
  • FIG. 2 An exemplary arrangement for a geared fan gas turbine engine 10 is shown in Figure 2 .
  • the low pressure turbine 19 (see Figure 1 ) drives the shaft 26, which is coupled to a sun wheel, or sun gear, 28 of the epicyclic gear arrangement 30.
  • a sun wheel, or sun gear, 28 of the epicyclic gear arrangement 30 Radially outwardly of the sun gear 28 and intermeshing therewith is a plurality of planet gears 32 that are coupled together by a planet carrier 34.
  • the planet carrier 34 constrains the planet gears 32 to precess around the sun gear 28 in synchronicity whilst enabling each planet gear 32 to rotate about its own axis.
  • the planet carrier 34 is coupled via linkages 36 to the fan 23 in order to drive its rotation about the engine axis 9.
  • an annulus or ring gear 38 Radially outwardly of the planet gears 32 and intermeshing therewith is an annulus or ring gear 38 that is coupled, via linkages 40, to a stationary supporting structure 24.
  • low pressure turbine and “low pressure compressor” as used herein may be taken to mean the lowest pressure turbine stages and lowest pressure compressor stages (i.e. not including the fan 23) respectively and/or the turbine and compressor stages that are connected together by the interconnecting shaft 26 with the lowest rotational speed in the engine (i.e. not including the gearbox output shaft that drives the fan 23).
  • the "low pressure turbine” and “low pressure compressor” referred to herein may alternatively be known as the "intermediate pressure turbine” and “intermediate pressure compressor”. Where such alternative nomenclature is used, the fan 23 may be referred to as a first, or lowest pressure, compression stage.
  • the epicyclic gearbox 30 is shown by way of example in greater detail in Figure 3 .
  • Each of the sun gear 28, planet gears 32 and ring gear 38 comprise teeth about their periphery to intermesh with the other gears. However, for clarity only exemplary portions of the teeth are illustrated in Figure 3 .
  • Practical applications of a planetary epicyclic gearbox 30 generally comprise at least three planet gears 32.
  • the epicyclic gearbox 30 illustrated by way of example in Figures 2 and 3 is of the planetary type, in that the planet carrier 34 is coupled to an output shaft via linkages 36, with the ring gear 38 fixed.
  • the epicyclic gearbox 30 may be a star arrangement, in which the planet carrier 34 is held fixed, with the ring (or annulus) gear 38 allowed to rotate. In such an arrangement the fan 23 is driven by the ring gear 38.
  • the gearbox 30 may be a differential gearbox in which the ring gear 38 and the planet carrier 34 are both allowed to rotate.
  • any suitable arrangement may be used for locating the gearbox 30 in the engine 10 and/or for connecting the gearbox 30 to the engine 10.
  • the connections (such as the linkages 36, 40 in the Figure 2 example) between the gearbox 30 and other parts of the engine 10 (such as the input shaft 26, the output shaft and the fixed structure 24) may have any desired degree of stiffness or flexibility.
  • any suitable arrangement of the bearings between rotating and stationary parts of the engine may be used, and the disclosure is not limited to the exemplary arrangement of Figure 2 .
  • the gearbox 30 has a star arrangement (described above)
  • the skilled person would readily understand that the arrangement of output and support linkages and bearing locations would typically be different to that shown by way of example in Figure 2 .
  • the present disclosure extends to a gas turbine engine having any arrangement of gearbox styles (for example star or planetary), support structures, input and output shaft arrangement, and bearing locations.
  • gearbox styles for example star or planetary
  • support structures for example star or planetary
  • input and output shaft arrangement for example star or planetary
  • bearing locations for example star or planetary
  • the gearbox may drive additional and/or alternative components (e.g. the intermediate pressure compressor and/or a booster compressor).
  • additional and/or alternative components e.g. the intermediate pressure compressor and/or a booster compressor.
  • gas turbine engines to which the present disclosure may be applied may have alternative configurations.
  • such engines may have an alternative number of compressors and/or turbines and/or an alternative number of interconnecting shafts.
  • the gas turbine engine shown in Figure 1 has a split flow nozzle 18, 20 meaning that the flow through the bypass duct 22 has its own nozzle that is separate to and radially outside the core exhaust nozzle 20.
  • this is not limiting, and any aspect of the present disclosure may 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 may have a fixed or variable area.
  • the described example relates to a turbofan engine, the disclosure may apply, for example, to any type of gas turbine engine, such as an open rotor (in which the fan stage is not surrounded by a nacelle) or turboprop engine, for example.
  • the geometry of the gas turbine engine 10, and components thereof, is defined by a conventional axis system, comprising an axial direction (which is aligned with the rotational axis 9), a radial direction (in the bottom-to-top direction in Figure 1 ), and a circumferential direction (perpendicular to the page in the Figure 1 view).
  • the axial, radial and circumferential directions are mutually perpendicular.
  • the gears for such engines and those for use for other purposes can be manufactured using a number of different processes such as casting, forging, blanking and extrusion. In many of these cases once the gear has been formed further machining will be required so that the part conforms to the specific design criteria required for its operation.
  • the further machining can be milling of the edges for size conformance; or milling or grinding of the teeth; and grinding the bore of the gear.
  • CNC computer numerical controls
  • 5-axis machines also allow for greater conformity of the final component as either the workpiece - the component to be machined - or the tooling head can be moved along 5 different axes simultaneously.
  • These movement axes are the standard X, Y and Z axis, as well as two rotational axes: the A-axis, which rotates around the X axis; and a C-axis which rotates around the Z-axis.
  • This movement of the workpiece and of the tooling enables the machining of highly complex components. It also allows for more than one process to be carried out on a single machine tool, which minimises the number of tools used in a production process. Furthermore, they can limit the number of machines required in a factory.
  • a dedicated cylindrical grinder In this an abrasive grinding wheel is rotated within the internal bore of the cylindrical workpiece, which is in turn rotated in the opposite direction, or alternatively the grinding wheel can move relative to the workpiece.
  • Cylindrical grinders can also be used for finishing the external surface of a cylinder or gear as well. These machines can produce high conformance components, but are limited as they are only able to grind and cannot be used to manufacture the teeth of the gear. As such when making a gear from its initial forming, if a cylindrical grinder is used then another machine is required to grind the teeth or to finish them.
  • One of the issues of using multiple machines is in errors resulting from the changing equipment between processing steps.
  • gears As such there are a number of means of producing the gears. Any of these processes can be used in the manufacture of the gears for gas turbine engines.
  • the gears used in a gas turbine engine are of a particularly high specification due to the forces that they are configured to take. As such, precision manufacturing is employed in order to achieve this, which is not just limited to the gear teeth themselves, but also to the grinding of the internal bore of the gear, such that it meets the weight and conformance targets required to use in a gas turbine engine.
  • Figure 4 shows an example of a typical planetary gear for use in the gearbox of a gas turbine engine. This is shown featuring an internal bore 44, which requires grinding down to increase the internal diameter and consequently, to reduce the mass of the gear.
  • On the outer surface of the gear are shown featuring double helical gear teeth 42, with a space between the helices of the gear.
  • Figure 5 shows the setup employed in the bore grinding process.
  • the workpiece has an outer edge onto which the gear teeth 52 are to be positioned either before or after the cylindrical bore 54 extending through the gear has been ground.
  • the bore is positioned in the centre of the cylindrical workpiece that is to be machined.
  • the internal bore comprises a cylindrical section 56 that requires grinding in order to reduce its thickness.
  • the internal bore is ground using grinding wheel 58.
  • the grinding wheel is rotated about an axis that is horizontal to that of the centre of the workpiece.
  • the workpiece can be rotated in the same or opposite direction to that of the grinding wheel.
  • the grinding wheel employed covers a substantial portion of the external diameter of the tube; this can be between 40%-80% of the external diameter of the pipe.
  • the method may also be applied to any type of gears having a central bore.
  • the same grinding machines can also be used for grinding the end faces of the cylindrical workpiece. This can be to ensure that the end faces are perpendicular to the outer surface of the workpiece.
  • the machine can be used to grind an outer face of the workpiece, that is to say the face whose axis runs parallel to the central bore. In doing so, it can be used to ground the gap between the helices of a double helical gear.
  • the grinding wheel can be positioned anywhere in the workpiece.
  • the grinding wheel is positioned in a lower quadrant.
  • the quadrants are taken relative to the standard orientation of the workpiece, such that 0° is considered to be at the top dead centre of the cylinder then the upper quadrants would cover this and the range of angles between 270°-90°.
  • the lower quadrants would cover the range of angles between 90°-270°- incorporating 180° from top dead centre.
  • the grinding wheel may have an axis of rotation that is parallel to the central axis of the workpiece and may be positioned anywhere on the workpiece. In an example it can be positioned anywhere from 90° to 180° from the top dead centre of the cylindrical bore with respect to the direction of rotation of the grinding wheel.
  • the grinding wheel is positioned at 135° around the arc of the bore with respect to the direction of rotation of the grinding wheel. However, it may be suitably positioned at 95 °, 100°, 105°, 110°, 115°, 120°, 125°, 130°, 140°, 145°, 150°, 155°, 160°, 165°, 170° or 175°.
  • a coolant may also be applied to the grinder wheel and/or workpiece whilst the grinding process is taking place.
  • the positioning of the grinding wheel in a lower quadrant has been found to allow for better access of the coolant. This in turn makes it better enabled to extract the swarf generated from grinding the workpiece and to reduce the temperature at the grind surface, thus reducing the amount of grind burn.
  • This also has the beneficial effect of improving the surface finish and reducing the wear on the grinding wheel.
  • This coolant therefore reduces the amount of damage that the workpiece suffers during its processing and consequently improves the strength of the final component.
  • the coolant can be supplied to the grinding interface from above the workpiece. This can be supplied in a variety of ways such as through a flat head slit nozzle or any suitable nozzle shape, such as round, oval, or square and at any suitable pressure. The use of high pressure coolant may further reduce the chance of grind burn on the workpiece.
  • the grinding may be performed as discussed above on a multi-axis grinding machine or on a dedicated cylindrical grinder.
  • the use of a multi-axis grinding machine could reduce the number of different setups required during the grinding process.
  • certain 5-axis machines having a Very Impressive Performance Extreme Removal (VIPER) grinding capability have been found to be particularly suitable for this purpose.
  • VIPER grinding employs aluminium oxide grinding wheels which are able to move around the work piece. The speed of rotation of the wheel and the use of coolant results in less thermal damage to workpiece during the manufacturing process. For this, it is desirable to operate the grinding wheel at high speeds.
  • Machines employing VIPER grinding are advantageous as they are not limited by the maximum size of the grind wheel, which is a limitation of a dedicated cylindrical bore grinder.
  • the grind reduction in the cylindrical bore may be performed in a three stage process. This involves an initial roughing pass, followed by semi finishing pass and completed via finishing pass. In a trial example 16 roughing passes, 8 semi-finishing passes and 2 finishing passes were used for the completed workpiece. However, the skilled person would appreciate the exact number of these steps for each stages could vary depending upon the operational configuration, and the desired final parameters of the bore grind. For example, this could be 20 or fewer roughing, semi-finishing or finishing steps , for example; 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 for each stage. For the different stages different grits on the grinding wheels may be used.
  • Coarser grit may be used for the roughing step and semi-finish finishing steps and a finer grit may be used for the finishing step.
  • the present disclosure also provides a gas turbine that has a gar that has a central bore ground by the method as described above.
  • the disclosure focuses on the machining of a gear for use in a gas turbine engine, the skilled person will appreciate that such a method may be used for any other suitable gear.
  • this could be for the gears used in wind turbine gear boxes, marine gearboxes, or car gear boxes.
  • the process can be applied to any type of power transmission gear requiring a high accuracy bore and teeth on the outside.
  • the disclosure can also be used for components that require a smooth interior bore as well as machining on the outer face. Examples of such components are turbocharger rotors.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)
EP19205047.4A 2018-11-19 2019-10-24 Meulage d'alésages cylindriques Withdrawn EP3659746A1 (fr)

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GBGB1818823.5A GB201818823D0 (en) 2018-11-19 2018-11-19 Grinding cylindrical bores

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EP3659746A1 true EP3659746A1 (fr) 2020-06-03

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CN1161267A (zh) * 1995-09-14 1997-10-08 邵文远 复合加工中心
US20060040584A1 (en) * 2002-07-30 2006-02-23 Charles Ray Method and apparatus for grinding
US20160003341A1 (en) * 2014-07-07 2016-01-07 Solar Turbines Incorporated Tri-lobe bearing for a gearbox
CN107470871A (zh) * 2017-09-22 2017-12-15 江苏赫夫特齿轮制造有限公司 中硬齿面齿轮轴加工方法
US20180169819A1 (en) * 2015-06-17 2018-06-21 Erwin Junker Maschinenfabrik Gmbh Method and grinding machine for grinding external and internal contours of workpieces in one clamping

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US2047055A (en) * 1934-06-01 1936-07-07 Heald Machine Co Grinding machine and method
DE19900011B4 (de) * 1999-01-02 2005-12-15 Reishauer Ag Vorrichtung zur gleichzeitigen Verzahnungs- und Bohrungsfeinbearbeitung an Getriebestirnzahnrädern
JP2008023596A (ja) * 2006-06-23 2008-02-07 Nissan Motor Co Ltd 微細凹部加工方法
DE102006034497A1 (de) * 2006-07-19 2008-01-24 Nagel Maschinen- Und Werkzeugfabrik Gmbh Verfahren zur kombinierten Feinbohr- und Honbearbeitung sowie Bearbeitungsanlage zur Durchführung des Verfahrens
JP5308388B2 (ja) * 2010-03-31 2013-10-09 三菱重工業株式会社 歯車加工機械
DE102010023830B4 (de) * 2010-06-15 2015-10-29 Gleason-Pfauter Maschinenfabrik Gmbh Verfahren und Werkzeugmaschine zum Bearbeiten einer Verzahnung, Computerprogrammprodukt und Verzahnung
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CN1161267A (zh) * 1995-09-14 1997-10-08 邵文远 复合加工中心
US20060040584A1 (en) * 2002-07-30 2006-02-23 Charles Ray Method and apparatus for grinding
US20160003341A1 (en) * 2014-07-07 2016-01-07 Solar Turbines Incorporated Tri-lobe bearing for a gearbox
US20180169819A1 (en) * 2015-06-17 2018-06-21 Erwin Junker Maschinenfabrik Gmbh Method and grinding machine for grinding external and internal contours of workpieces in one clamping
CN107470871A (zh) * 2017-09-22 2017-12-15 江苏赫夫特齿轮制造有限公司 中硬齿面齿轮轴加工方法

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