Experimental and numerical analysis of automotive gearbox rattle noise Younes KADMIRI Emmanuel RIGAUD, Joël PERRET-LIAUDET Journées GDR Visible, 18-19 mai 2011, IFSTTAR, Bron
Introduction Improving acoustic confort External noise sources: - Aerodynamic -Pneumatic
Introduction Improving acoustic confort External noise sources: - Aerodynamic -Pneumatic Internal noise sources: -Engine -Gearbox (gear whine, rattle noise) Engine Gearbox
Introduction Kinematic scheme of TL4 gearbox Idle gears Driving gears and shafts Synchronizing system Differential Housing
Introduction 6 5 4 3 2 1 Differential Configuration : Neutral
Introduction 6 5 4 3 2 1 Differential Configuration : 3 rd gearratio engaged
Introduction 2600 Ve elocity 2500 Four-cylinder four stroke engine Time 2400
Operating conditions - Operating speed - Drag torque - Contact stifness/damping Housing vibration Vibration transfer (shaft, bearings) Rattle noise Idle gear dynamics Excitation source Design parameters - Idle gears inertia - Backlashes
Numericalmodel Velocity fluctuation Excitation source - Operating conditions - Design parameters - Idle gears dynamics - Impacts time history - Transmitted forces Impulse response Housing vibration Renault criterion Rattlenoise characterization
Non linear model y 2 (t) Angular displacement m x(t) y 1 (t) F Displacement along the action line Free fligth Permanent contact Impacts y 2 (t) y 2 (t) y 2 (t) m m x(t) y 1 (t) m x(t) y 1 (t) m x(t) y 1 (t) F && x = F F R 1( t) = F + my& ( t R ( t) = F + my& ( 0 < 1 0 > 2 2 t ) ) ( x & + y& + i F ) = r( x& 0 r 1 y& i )
Dimensionlessnon linear model 6 variables necessary to describe rattle noise (m, F, r, H, j, ω) Vaschy-Buckingham theorem 3 dimensionless numbers r j = j H Λ = mhω 2 F
Time responsesfor j = 8, r = 0.85 x, y x, y Λ = 1,1 Λ = 1,5 x, y x, y Λ = 2,5 Λ = 3,5 t t
Impulses diagram Active flank B: rebounds and contact intermittency C: chaotic response I Reverse flank D: 2T 2 impacts response Λ E: 1T 2 impacts response
Conclusion Restitution coefficient Λparameter(m, H, F, ω) Numerical model Gear backlash Spectral content of velocity fluctuation Measuring these parameters is necessary
Test bench(bacy) Experimentsperformed: Key parameters measurement(restitution coeff., drag torque, ) Idle gear dynamics measurement Housing vibration measurement Radiated noise measurement.
Gearboxinstrumentation Weak dimensions Small gear backlash = 0.1 mm Idle gear and supporting shaft are indepedant Severe operating conditions (high Ω, oil churning, high T,...) Optical encoder on driving gear Driving gear Idle gear Optical encoder on idle gear Configuration : 2 nd gear ratio Configuration : 2 nd, 3 rd and 4 th gear ratio
Idlegeardynamics T Experimental and simulated relative velocities (rpm m) (m/ /s) (m/ /s) Ω = 750 rpm et A = 50 rpm Neutral Experimental and simulated Poincaré maps T Φ i =t i [ T] Φ:phase(s) ti :Impacttime T :period I(kg.m/s) ) I(kg.m/s) Φ(s) Φ(s)
T Idlegeardynamics Experimental and simulated relative velocities (Rpm m) (m/ /s) (m/ /s) Ω = 750 rpm et A = 100 rpm Neutral Experimental and simulated Poincaré maps Φ i =t i [ T] Φ:phase(s) ti :Impacttime T :period I(kg.m/s) ) I(kg.m/s) Φ(s) Φ(s)
Idlegeardynamics Experimental and simulated relative velocities (rpm m) (m/ /s) (m/ /s) Ω = 750 rpm et A = 125 rpm 3 rd ratio engaged Experimental and simulated Poincaré maps Φ i =t i [ T] Φ:phase(s) ti :Impacttime T :period I(kg.m/s) ) I(kg.m/s) Φ(s) Φ(s)
Housingvibration Model outputs Time response Successive impulses Housing response Measured transfer fonction Housing response
Housingvibration Ω=750 rpm A=50 rpm A=75 rpm A=100 rpm Simulatio on Experimen nts (m/s²) (m/s²)
Renault Criterion«5 faces» Ω=500, 750, 1000 rpm Experiments/ Simulated Criterion«5 faces» (db) Criterion«5 faces» (db) A (rpm) A (rpm) A 50 rpm 75 rpm 100 rpm 125 rpm Experiments 16,4 db 18,6 db 19,5 db 20,9 db Simulation 14,9 db 17,6 db 18,6 db 20,6 db Error 1,5 db 1,0 db 0,9 db 0,3 db
Backlash(µm) Backlash(µm) Conclusion - Experiments performed with BACY allowed non linear numerical model. - Operational software. -Rattlenoisecanbepredictedfor: any gearbox, any gear ratio, any operating conditions. - Parametric studies allow gearbox design optimization. Ω=750 rpm, A=75 rpm Ω=750 rpm, A=125 rpm «5 faces» (db) «5 faces» (db)