Modern automotive powertrains are increasingly adopting engine downsizing and down speeding to meet stringent emission regulations and improving fuel efficiency However, these changes result in higher torsional vibrations excitation amplitudes and NVH (Noise, Vibration, and Harshness) refinement more challenging. With growing customer expectations for premium driving experiences conventional clutch is no longer sufficient. To meet the NVH performance targets of the vehicle Dual Mass Flywheels (DMFs) are used
In DMF due to lower stiffness and inertia separation there is a greater advantage on torsional filtration in normal drive and idle condition. But the torsional resonance frequency of the connected DMF is lower than the idle RPM. Engine startup is a key drawback with DMF equipped vehicles. The proper tuning of starter motor performance & DMF stiffness is required to cross the resonance zone faster otherwise it will lead to DMF to stay in the resonance zone for a longer time leading to structural failure over the period.
In this paper we focus on DMF resonance crossing during engine startup condition in the 3 Cylinder Gasoline application. Test measurement is done to capture the startability behavior of DMF. AMESIM 1D simulation model is developed to reproduce the DMF resonance behavior and relative displacement between Primary and secondary flywheel is simulated. Optimization of DMF Spring stiffness between stages are proposed based on correlated simulation model. With the new design of DMF, the startability of the vehicle has improved & also the DMF displacement is reduced within the design limit. This evaluation method gives quick assessment on startability improvement in DMF equipped vehicles.