TORSIONAL VIBRATIONS IN AUTOMOTIVE POWERTRAINS The automotive industry is currently facing major challenges with regard to the reduction of emissions and fuel consumption. Requirements on fuel-efficiency and strict emission regulations have led to the development of small combustion engines with low numbers of cylinders and low operational speeds. Downsizing and downspeeding are the most important development approaches to encounter the CO 2 reduction targets.Excitation of Torsional Vibrations Downsizing of engines is characterized by low engine displacements and frequently by low numbers of cylinders as well. Downspeeding is characterized by low engine speeds in combination with high mean torques by supercharging in order to provide sufficient driving performance. With downsizing and downspeeding there is an increase of the excitation of torsional vibrations by the combustion engine. High peak torques and dynamic torque fluctuation in combination with high mean torque can result in problems with NVH and component strength. Therefore, torsional vibration reduction systems are attached onto the engine crankshaft to reduce the dynamic torque fluctuation acting on the powertrain (Fig. 1).Innovative Torsional Vibration Reduction Devices - Vehicle-Related Design and Component Strength Analysis Georg Johann Meingaßner, Hermann Pflaum, and Karsten Stahl TU München - Gear Research Centre (FZG) ABSTRACT Downsizing and downspeeding are currently important development approaches of the automobile industry to improve fuel efficiency and to reduce emissions. Decreased operational speeds in combination with higher combustion pressures lead to an increase of the excitation of torsional vibrations by the combustion engine. Torsional vibrations in powertrains can cause strength and NVH problems as well as lower driving comfort and reliability of the vehicle. Currently, conventional systems for reduction of torsional vibrations are increasingly reaching their limits. In cooperation with several institutes of the Technische Universität München (TUM) innovative concepts for an improved reduction of torsional vibrations in automotive powertrains have been developed. Several of those concepts have been realized as prototype assemblies engineered by the Gear Research Centre (FZG). ([ 6], [7], [8], [12], [13], [14]) During the design process, different challenges with regard to mass, mass moment of inertia and space demands have to be considered to ensure system performance and to meet vehicle-related requirements. Demands of prototype assemblies regarding modularity and installation interfaces to the available testing environment have to be considered as well. The demanding, partially atypical and dynamic mechanical loads of the components require both analytical and FEA-based strength analysis attending to the design process of the prototype assembly. With regard to bearings and gears with oscillating load, several steps of design and strength analysis have to be performed. Selected systems are presented in concept with special regard to their prototype designs. Selected design steps and performed strength calculations for major components used in the developed torsional vibration reduction devices are introduced. CITATION: Meingaßner, G., Pflaum, H., and Stahl, K., "Innovative Torsional Vibration Reduction Devices - Vehicle-Related Design and Component Strength Analysis," SAE Int. J. Passeng. Cars - Mech. Syst. 7(4):2014, doi:10.4271/2014-01-2862.2014-01-2862 Published 10/13/2014 doi:10.4271/2014-01-2862 saepcmech.saejournals.org 1392Downloaded from SAE International by Tsinghua University, Friday, July 03, 2020Figure 1. Effects of downsizing and downspeeding on powertrain dynamics ([1]). Further downsizing and downspeeding is limited by the performance of torsional vibration reductions systems, especially at low engine speeds. Increasing customer demands for driving comfort can only be met with a high level of research and development.