Effect of Lash Sensitivity on Engine Brake Performance and Valvetrain Dynamics

<div class="section abstract"><div class="htmlview paragraph">Engine brakes (EB) are more effective in decelerating the heavy-duty (HD) vehicles and maintaining constant speed during downgrading. Therefore, commercial vehicle OEM’s along with regulations, demand the acclimating of engine brake system. To achieve this, it is equally important to adopt to variable valve actuation (VVA) dynamic valvetrain (VT) system. To help develop these systems, Model Based Product Development approach is used primarily at Eaton.</div><div class="htmlview paragraph">In current work, the effect of valve lash sensitivity on EB performance and VT dynamics is studied using multi physics GT-SUITE models. This helps to understand the impact of lash on valve lift opening, lift loss and overall VT system compliance. In addition to the above VT dynamics, its effect on EB power is also studied. This is done using a medium duty 6-cylinder GT-POWER engine model, which is developed from Fast Response Model (FRM) database. The model is validated using Frictional Mean Effective Pressure (FMEP) motoring engine test (empirical) data. A type 3 VT dynamic model is developed to replicate the mechanism and validated using valve lift proximity sensor data. The validated engine performance and mechanical dynamic models are then integrated in such a way that the engine model imposes the cylinder and port pressures on the valves within VT dynamic model; and the resultant valve lift from VT dynamic model is again fed into engine model. This integrated model captures the dynamic variation of the valve lift along with the lash sensitivity.</div><div class="htmlview paragraph">A study for EB performance loss due to the system lash, is important to develop the correct valve lifts. Also, lash sensitivity impacts the performance of VT dynamics. So, the effect of lash sensitivity on other dynamic phenomenon such as contact forces, valve closing velocity and contact stresses are analyzed in this work. Therefore, the study helped to optimize the valve lift with ramp for lash sensitivity to meet all VT design limits along with maximum brake power within the required peak cylinder pressure constraint.</div></div>