This study analyses the effect of external damping of roller bearings on the acoustic behaviour of gearboxes in electric powertrains. The growing use of electric vehicles has increased the importance of reducing gearbox noise, as the lack of noise masking from internal combustion engines and the higher operating speeds of electric motors exacerbate the acoustic challenges. Gearbox noise, which is primarily caused by tooth mesh excitation and its transmission through shafts and bearings, requires strategies to minimise its impact on vehicle comfort and performance.
External damping is achieved through the integration of specific elements at the circumference of the outer bearing ring. These elements are utilised to modify the vibration transfer behaviour of the bearing assembly. This, in turn, can lead to a reduction in both structure-borne and airborne noise emissions at the gearbox housing. A test design was created to quantify the effects of different damping configurations. This approach allows the analysis of selected parameters including material properties, stiffness and oil pressure between the damping elements.
Physical experiments are conducted on a high-speed gear test rig, specifically designed to measure key variables such as noise emissions and vibration characteristics. The test rig ensures precise data acquisition, allowing a comprehensive analysis of the interactions between damping properties and noise reduction mechanisms. The experimental results are compared with reference measurements conducted under standard bearing conditions. This comparison enables the quantification of the damping effect and ensures that the observed noise reduction is attributable to the external damping elements.
The results provide valuable insights into the dynamic behaviour of the gearbox housing equipped with externally damped bearings. These findings contribute to the optimisation of gearbox designs for e-mobility applications.