Engine brakes are much effective to retard the heavy-duty vehicle during deceleration compared to the traditional clutch-brake system. Therefore, the current upgrading vehicle industry and the evolving road infrastructure for better connectivity along with regulations, demands the acclimatizing engine brake (EB) system. To achieve this, it is equally important to have high speed variable valve actuation dynamic valvetrain system. To help develop this system, Model Based Product Development approach is used primarily at Eaton.
In the present work, the effect of valve lash sensitivity on valvetrain (VT) dynamics and engine brake performance is studied. This helps to understand the coupled effect of multi-physics on valve lift opening, on valve lift loss and on VT system compliance. In addition to this engine brake power becomes very sensitive under such situations. To study this a medium duty 6-cylinder engine model is developed from the GT-POWER engine Fast Response Model (FRM) database and validated using Frictional Mean Effective Pressure (FMEP) motoring engine test data. Also, the type 3 VT dynamic model is developed and validated using valve lift proxy data. These, validated performance, and mechanical models are integrated in such a way that the engine model imposes the cylinder and port pressures on the valve and VT dynamic model actuates the engine valves in an integrated manner to capture the dynamic variation of the valve lift along with the lash sensitivity.
A proactive study for performance loss due to the system lash, is important to develop the correct valve lift ramps. Also, lash sensitivity impacts performance of VT dynamics and its reliability. So, the effect of lash sensitivity on other dynamic phenomenon such as contact forces, valve closing velocity and contact stresses etc. are analyzed. 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 constrain.
Keywords- Engine Brake, Engine Motoring, Kinematic, Dynamic, Valvetrain, Cam Lift, Valve Lift, Lash, FRM, Optimization.