Torsional vibrations in truck powertrains with dual mass flywheel having piecewise linear stiffness

Abstract

The vehicle industry faces big challenges when it comes to reducing the emissions of heavy vehicles. In order to cope with the increasing demand for efficient, low emission vehicles, the trend within the industry is to down-size and down-speed the engines. These measures lead to higher torsional vibrations in the powertrain and therefore there is also an increasing need for efficient reduction of torsional vibrations. One way to reduce the vibration is to use a dual mass flywheel. A dual mass flywheel consists of two flywheels connected by a torsional spring package.\ua0 The spring package should have low stiffness but must also cope with very high torques. Therefore the dual mass flywheels are often designed so that they have a piecewise linear relationship between torque and wind-up angle. A full powertrain model has been used with realistic engine load in order to evaluate how the piecewise linear design affects the vibrations in the powertrain. Simulations have been performed in frequency domain and time domain and evaluation is done both with respect to mode shapes and frequencies and computed steady-state vibration amplitudes. In the linear region, there is a frequency shift for a problematic resonance mode that leads to significant decrease in vibration amplitude at low engine speeds. In non-linear regions, a resonance mode corresponding to half the main exciting frequency from the engine can be excited, leading to high vibration amplitudes. The frequency of this mode and the extent to which it is excited depends on the engine torque and highest amplitudes are not always obtained at the highest load