Browse Publications Technical Papers 2019-01-0785

An Investigation of a Reduction Method of the Body Vibration at a Situation of Engine Start-Stop 2019-01-0785

In recent years, electrification of powertrains has been promoted to improve fuel efficiency and CO2 emissions. Along with electrification, it is possible to reduce engine usage frequency and improve the fuel efficiency in traveling. 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 be reduced as compared with conventional engine-driven vehicle.
However, since the HEV is equipped with a high compression ratio engine for improving fuel economy, there is cause for concern that excitation force generated by the powertrain at the time of engine start increases. Also, the vehicle body vibration at engine start situations requires further consideration, because the operation frequency of engine decreases.
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 situation, 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 IVC which can tolerate body vibration for each compression ratio.


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