Torsional Vibration Damping Concept in Hybrid Systems
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Torsional Vibration Damping Concept in Hybrid Systems
Hybridized drives significantly reduce CO2 emissions. While current mainstream developments currently focus on the expansion of conventional combustion engines to incorporate electrification, the next step will be to design systems with much smaller engines and with fewer cylinders, often com bined with cylinder deactivation. However, many of these approaches face the challenge of handling the NVH behavior of the downsized drives. With its DirectE concept, Tectos presents one solution for effectively damping torsional power train vibrations using the electric drive of a hybrid system.
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DOWNSIZING AND CYLINDER DEACTIVATION EX ACERBATE NVH REQUIREMENTS
In order to fight climate change and to preserve resources, the reduction of CO2 emissions will remain one of the top priorities when developing new drive solutions. Hybrid systems whose electric motor supports the combustion engine in driving the vehicle have established themselves successfully in the market, with plug-in hybrid systems advancing particularly well. Plug-in hybrid models link the benefits of fully electric operation in urban environments to using the combustion engine for longer drives and at higher speeds. Parallel configurations with direct
AU T H O R S
mechanical output in a so-called P2 hybrid configuration are considered a very promising option. Combustion engines still tend to aim for less displacement and fewer cylinders (downsizing), for cylinder deactivation and for lower service speeds (downspeeding). An issue shared by all of these concepts are pronounced torsional vibrations along the powertrain which, in turn, lead to more severe NVH (Noise, Vibration, Harshness) problems. Consequently, real-life driving will often fail to realize the full theoretical potential of CO2 reductions. In order to improve customer acceptance of these combustion engine concepts and to enhance their range of hybrid system applications, Tectos has MTZ worldwide 10|2020
Prof. Dr.-Ing. Günter Hohenberg is General Manager of IVD Prof. Hohenberg GmbH in Graz (Austria).
Dipl.-Ing. Stefan Maxl is Scientific Assistant to the Research & Development Depart ment of Tectos GmbH in Graz (Austria).
Prof. Dr. Christian Beidl is Head of the Combustion Engines and Vehicle Drives Department of Darmstadt Technical University (Germany).
joined forces with IVD Prof. Hohenberg and Darmstadt Technical University to develop the so-called DirectE concept of active torsional vibration damping [1]. Since hybridization already relies on an electric motor in the powertrain, this motor can be used to generate additional torque impulses that double the excitation frequency of the drivetrain. The resulting NVH response is equivalent to that of a conventional combustion engine with twice the number of cylinders, FIGURE 1. Where cylinders are deactivated, this approach will retain the NVH level of the entire engine even with non-fired cylinders. Deactivation will go unnoticed and not reduce pas senger comfort. In applications
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