Search Results

Current modeling techniques of the powertrain noise, vibration and harshness (NVH) involve fully meshed structural components and rely, in general, on predefined excitation loads to evaluate linear transfer or structural attenuation functions. While effective for comparative assessment of various designs, these methods neglect the complex dynamic interactions between the powertrain structure and crankshaft, piston, valve train, timing drive, and accessory drive systems. This paper presents an overview of modeling methods of low and high frequency powertrain NVH with focus on dynamic interaction among structural components. A coupled and fully flexible multi-body dynamics model using AVL/Excite is presented. The model includes the cranktrain, crankcase, cylinder head, covers, oil pan, mounts, and transmission housing represented as finite element meshes.

In recent years, computer simulations gained an increased role in the design, development, optimization, and calibration of the valve train systems. With the development of non-conventional systems and actuation mechanisms, computer modeling became even more important. Part I of this article presents an overview of the current modeling and simulation methods of conventional valve trains at component and system level. First, the modeling of the valve train kinematics, including cam shape design and optimization, is summarized. Mathematical modeling of the valve spring, hydraulic lash adjuster, oil aeration, bulk modulus, contact stiffness and contact damping in multibody systems are discussed. The benefits and limitations of the different modeling approaches of the valve train dynamics are pointed out. Another important aspect is the valve train tribology.