An investigation of a reduction method of the body vibration at a situation of engine start-stop -A construction of MBD process for reduction of the body vibration of hybrid powertrain- 2019-01-0785
In recent years, electrification of powertrain has been promoted to improve fuel efficiency and CO2 emission. Along with electrification, it is possible to reduce engine usage frequency, and improve the fuel efficiency in traveling the vehicle.
Especially, in a hybrid electric vehicle (HEV), the state changes from motor assist mode to engine firing mode. As a result, stay time in eigenvalue of a powertrain is shortened, and vibration of the vehicle body at the engine start situation is able to reduce as compared with conventional engine vehicle.
However, since the HEV is equipped with a high compression ratio engine for improving fuel economy, there is a concern that excitation force generated by the powertrain at the time of engine start increases. Also, because the operation frequency of engine decreases, the body vibration at engine start situations must be considered.
Therefore, the purpose of this study is to reduce the body vibration at the engine start situation of the HEV. In order to realize, the following model-based development (MBD) process was carried out.
-Construction of a multi-body-dynamics model combining powertrain and vehicle body
-Simulation of the impact on the body vibration by changing the compression ratio and valve timing at the engine start situation
It has been clarified that the increase in vehicle body vibration accompanying the increase in compression ratio can be reduced by the retardation of the intake valve closing timing. Finally, it is possible to quantitatively choice the intake valve closing timing that acceptable the body vibration for each compression ratio.