Idle Vibration Robustness Analysis of An I3 Engine Without Balance Shaft 2021-01-1023

I3 engine has its unique advantage in helping OEM meeting the ever-increasing government regulations in emission and fuel consumptions. Its small size, low friction, and light weight provide OEM the opportunity in lowering the costs, reducing fuel consumption, and emissions. ISH predicts that the I3 engine will count for 38% of IC engine volume in 2025 in Chinese Auto Market. One of biggest issues of the I3 engine is its higher vibration levels, especially in idle conditions. This is primarily due to two reasons. First is that I3 engine cylinder layout results in 1^st order inertia moments. Second is that I3 engine combustion produces higher combustion excitation torque with lower frequency (1.5^th engine order). To compensate the 1^st order inertia moments, a balance shaft is typically added to cancel these 1^st order inertia moments. While the balance shaft reduces the vibration levels, it adds significant cost and weight in the I3 engine applications. In this paper, a study is carried out on a 1.0L I3 engine without balance shaft thought the Powertrain mount optimizations, including the robustness analysis. The optimization process is divided into two steps. The first step is to optimize the right and left Powertrain mount rates with different I3 engine balancing rates. The goal of this optimization is to minimize the vehicle vibrations in the idle conditions and start-up shake. The second step is to perform additional optimization on the Powertrain rear mount rate. The goal of this additional optimization is to further improve the vehicle start-up shake. The optimization processes in the first and second steps determine the nominal mount rates. Based on suppliers manufacturing capability, there will typically be +/-10-15% mount rate variations in production. To ensure that the vehicle system is robust to these mount rate variations, a robustness study is carried out, both in CAE analysis and testing. During the mount optimizations, a solid CAE analysis and testing correlation is established for idle vibration and start-up shake. This ensures that the CAE analysis can be used in the future designs.