EFFICIENZA E ANALISI TERMICA Ing. Ivan Saltini Italy Country Manager
How to get most realistic efficiency calculation for gearboxes?
Topics Motivation / general calculation Industrial bevel-helical gearbox Automotive 7-speed dual clutch transmission Drive cycle simulations Efficiency optimization Conclusion
Motivation industrial gearboxes High demands for power loss investigations Reduction of oil temperature Dimensioning of cooler unit Modification of housing design Concept and design Power Loss Thermal rating Cooler dimensioning Operating costs Systematic power loss analysis and optimization process
Efficiency Motivation automotive applications Efficiency investigations as contribution to reach future CO 2 limits Comparison of different transmission layouts Detection of power loss drivers Evaluation of improvement measures in NEDC KISSsys-model Power loss maps Drive cycle simulation Improvement measures Efficiency evaluation Systematic power loss analysis and optimization process
Efficiency template general handling Calculation model with added efficiency template The thermal rating calculation is provided in a template and is added into the existing gearbox For each machine element the power loss or efficiency calculation is added The thermal rating is done considering the heat dissipation and cooler unit
Efficiency template losses calculation Modified calculation o Procedure The template checks the model for machine elements For the gears and bearings the losses calculation are added to the shaft editor For the input and output shaft, the sealing losses can be added if required
Efficiency template losses calculation Gear calculation o Gears P V PVZ 0 P VZP according to ISO/TR 14179-1/2 Epicyclic gears: AGMA 6123-B06 Bevel and hyoid gears: Niemann/Winter, Wech o Alternative for ISO/TR 14179: Contact analysis for meshing losses for cylindrical gears
Efficiency template losses calculation Shaft calculation o Bearings o P V = P VL0 + P VLP according to ISO/TR 14179-1/2 according to SKF Catalog 1994 M M 0 M1 M 2 M3 according to SKF Catalog 2004 M M rr M sl M seal M drag
Efficiency Efficiency template losses calculation Data maps o Oil pumps, synchronizers,.. There are a number of machine elements where no literature exists Typical elements are oil pumps, clutches (several types), synchronizers,.. Data maps are used to interpolate the power loss value from pre-calculated or measured data The data map is multi dimensional, as i.e. temperature, speed difference, absolute speed,..
Efficiency template thermal rating Calculation model o Heat dissipation The ISO/TR 14179-2 considers the gearbox housing design very detailed: - housing, fins - ventilation conditions - input, output shafts and couplings - foundation o Thermal rating The thermal rating is performed regarding: - Calculate cooler capacity, or - Calculate temperature
Topics Motivation / general calculation Industrial bevel-helical gearbox Automotive 7-speed dual clutch transmission Drive cycle simulations Efficiency optimization Conclusion
Industrial bevel-helical gearbox Calculation model standardized gearboxes series and customized gearbox design Helical, bevel-helical and worm-helical gearboxes Ratio up to about 200:1 High efficiency
Thermal rating testing field Testing field o Testing of power trains Dynamic power measurement Reporting of temperature and efficiency Static functional testings as i.e. total stiffness of the power train o Single components Gear wheels Separate testing field for bearings and radial shaft seals
Thermal rating measurement of power trains Measurement reports o Testing of power trains for efficiency Measurement series with constant torque and/or constant speed Temperature profile for ambient air and oil are recorded Input speed, torque and output torque (controlled) are recorded Comparisons of temperature between calculations and measurements are ok, but modifications are necessary
Calculation model - experiences Calculation model o Experiences with our customers are: detailed and fast calculation procedure according to ISO/TR 14179-2 o Next steps are: more validation with individual test runs of machine elements Modification of temperature calculation to get closer match
Topics Motivation / general calculation Industrial bevel-helical gearbox Automotive 7-speed dual clutch transmission Drive cycle simulations Efficiency optimization Conclusion
7-speed dual clutch transmission (IAV 7-DC280) CAD design with considered power losses Synchronizer Drag losses Clutches Drag losses Sealings Rotary unions Sealings under pressure Gear speed dependent losses Injection Ventilation Bearings Load dependent Load independent Gear meshing Oil pump 3D map interpolation Consideration of all relevant power losses in the transmission
Calculation model Calculation model o Benefit of calculation model Calculation model considers all kinematic and kinetic interactions (7 speeds) For the power losses, own data maps based on measurement or calculations were imported
5500 4500 3500 2500 1500 500 5500 4500 3500 2500 1500 500 5500 4500 3500 2500 1500 500 Power loss [kw] Power loss [kw] Power loss [kw] Power loss maps instead of equations Exemplary power losses of gear 7 at 60 C oil temperature Power loss gear meshing 3.0 2.5 2.0 1.5 1.0 0.5 0.0 Power loss bearings 3.0 2.5 2.0 1.5 1.0 0.5 0.0 Power loss injection 0.4 0.3 0.3 0.2 0.2 0.1 0.1 0.0 Speed [rpm] Speed [rpm] Speed [rpm] Data maps calculated for gear, bearing and sealing losses according to literature Data maps calculated for other elements according to measurements or literature
5500 4500 3500 2500 1500 500 5500 4500 3500 2500 1500 500 Power loss [kw] Power loss maps Exemplary power losses of gear 7 at 60 C oil temperature Overall power loss 14 12 10 8 6 4 2 0 Overall efficiency 95% 90% 85% 80% Speed [rpm] Speed [rpm]
Topics Motivation / general calculation Industrial bevel-helical gearbox Automotive 7-speed dual clutch transmission Drive cycle simulations Efficiency optimization Conclusion
Torque [Nm] velocity Drive cycle simulations Operating points in engine map o Simulation target Volllastdrehmoment [Nm] 300 200 200 100 100 0-100 0 100 2000 4000 Speed [rpm] NEDC time 2 10 3 4 10 3 6 10 3 8 10 3 Drehzahl [1/min] 6000 Boundary conditions Drive cycle NEDC Vehicle medium-class Drive train front transverse Mass 1650 kg Combustion engine gasoline Power 140 kw Torque 265 Nm Evaluate the overall power loss distribution in the consumption relevant NEDC Identification of power loss drivers and evaluate improvement measures directly on the basis of CO 2 reduction predictions o NEDC simulation environment Mid size car with gasoline engine
Result of drive cycle simulation Energy losses over components Energy losses over speeds Rotary unions 6.4% Oil pump 35.7% Sealings 4.6% Bearings 19.0% Gear meshing 18.1% Clutches 1.3% Synchronizers 10.7% Injection 4.1% Gear 6 10% Gear 5 14% Gear 7 59% Gear 4 3% Gear 1 4% Gear 2 7% Gear 3 3% Highest optimization potential in hydraulic actuation, bearings, tooth system and synchronizers Evaluation of energy losses in 7 th gear corresponding to the high time share of 41.6% in the NEDC
Topics Motivation / general calculation Industrial bevel-helical gearbox Automotive 7-speed dual clutch transmission Drive cycle simulations Efficiency optimization Conclusion
Efficiency optimization Optimization measures regarding efficiency improvement o Tooth system Basic design exhibits a distribution between contact and overlap ratio of ε α = 2 and ε β = 1 New design of macro geometry with decrease of profile contact ratio ε α = 1.5 and increase of overlap contact ratio ε β = 1.5 o Bearings Substitution of tapered roller bearing at differential with fixed/free bearing solution
Efficiency optimization Efficiency optimization of gear micro geometry Specific sliding Slide speed Angle of rotation Slide speed Gear A Specific sliding Gear B Specific sliding Micro geometry (tip relief, crowning, ) gives further reduction of losses Exemplary efficiency increase of the final drive from 99.06% without modifications up to 99.6% by low load conditions Power loss No modification Optimized Normal force (line load) Angle of rotation Angle of rotation
Efficiency optimization Efficiency optimization using contact analysis Efficiency Transmission error 10 % load 100 % load Automatic variation of modifications and load inside to obtain best variant Assessment based on tooth contact analysis
Topics Motivation / general calculation Industrial bevel-helical gearbox Automotive 7-speed dual clutch transmission Drive cycle simulations Efficiency optimization Conclusion
How to get most realistic efficiency calculation: Energy losses over components The ISO/TR 14179 provides a good basis for calculation of power losses and thermal rating However, for the power losses, meanwhile newer and more detailed literature are available, and also needed (i.e. for churning losses, etc.) Instead of analytical approach, also contact analyses or data maps can be applied The thermal rating is quite detailed, but requires some adjustment work for the individual gearbox
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