| Valve mechanism is an important part of an engine, and its performance has a direct impact on the reliability, dynamic property, economy and emission of the latter. On the one hand, the valve timing and valve lift in traditional engines are both immutable, thus unable to meet the requirements in economy, dynamic property and emission when the engine works at high or low speed; on the other hand, there are certain limitations in the existing variable valve mechanisms. Therefore, this thesis put forward a new variable valve system with adjustable hydraulic volume. In accordance with the structure of this system and the regulation principles, the author did some relevant research on the valve timing system dynamics.Firstly, the thesis analyzed how the variable valve timing improved the performance of an engine, how the new variable valve system worked, and the running of each part in theory.Secondly, a mathematic model of this system was built based on the mutual relationship between the oil in the pipeline of the new variable valve system with adjustable hydraulic volume. Meanwhile, a simulation model of AMESim system dynamics was also built according to the working principle of the system.Thirdly,With the latter, the author performed an analysis of, when the cam rotation speed changed, the phase adjustment, lift adjustment, the change of the oil pressure with adjusted phase and lift, as well as the dynamic property of the moving parts such as valve.Finally, according to the adjustment principle of the system, the author set up a testing platform of single valve and a testing apparatus with cylinder head. By comparing the valve test movement curve with the simulation results, the research showed that the overall trend of the valve test results is consistent with that of the simulation results, with certain differences in specific numerical values. On the basis of these differences, the author proposed some suggestions on the improvement of the valve mechanism design. |
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