Torsional vibration absorbers in heavy-duty truck powertrains

Abstract: The heavy-duty vehicle manufacturers face large challenges when it comes to reducing CO2 emissions from vehicles. The ongoing development of more efficient combustion engines leads to an increase in torsional vibrations. Experience within the industry indicates that the conventional single mass flywheel (SMF) and clutch will not be enough to protect the gearbox and rear driveline from engine induced vibrations in the future; more advanced technology will be needed. The work presented in this thesis focuses on simulation and analysis of torsional vibration absorbers for heavy-duty truck applications. Different multiple-mass flywheels are analysed, including dual mass flywheels (DMFs), power split vibration absorbers (PSVAs) and DMFs combined with tuned vibration absorbers (TVAs). DMFs have been used in smaller vehicles for many years, but the use in heavy-duty commercial applications is to date very limited. The other two vibration absorbers studied in this work have not yet been industrialised. The vibrations absorbers are analysed by means of simulations. Methodologies for efficient simulations in time- and frequency-domain have been developed and are presented in the thesis. The frequency-domain methods used include the harmonic response and a harmonic balance method, combined with an arc-length continuation scheme. For models with many gap-activated springs, a time-domain approach is proposed, where the dynamics problem is reformulated as a linear complementary problem (LCP).A detailed DMF model, including internal parts, friction and clearances, is presented for time-domain studies requiring high accuracy. The model is correlated based on test rig measurements. The torsional vibrations in typical heavy-duty truck powertrains with the different multiple-mass flywheels are simulated in a large engine load and speed range. The results are analysed and compared to corresponding conventional powertrains. It is evaluated how different design parameters affect the torsional vibrations and the feasibility of the concepts for heavy-duty use is studied. The simulations show that the torsional vibration amplitudes are generally significantly lower with a DMF than with an SMF, but under some conditions significant resonance excitation can occur. The PSVA and DMF equipped with a TVA can reduce vibrations further than a corresponding DMF within limited speed ranges, but lead to higher vibration amplitudes outside these ranges.