| With the development of the engine towards to the direction of high speed, high load, low fuel consumption and low emission direction, the requirement of the performance of engine components is becoming stricter and stricter. As the key component of engine, the performance of piston rings affects engine power, fuel economy and emissions. Study on the dynamics of piston rings can provide theoretical guidance for optimizing engine structure.The piston component of a four-cylinder diesel engine was chosen as the research object. The piston dynamics had been done by means of AVL EXCITE Piston& Ring software. The research contents of this paper are as follows. Firstly, the model of piston group dynamics was established, and then the simulation results were compared to the experiment one, that provided the basis for the subsequent simulation. Secondly, the impacts of the structure of piston skirt, head taper, pin hole position and displacement of cylinder and piston on the piston secondary motion were researched, and then the impacts of piston secondary motion on the characteristics of piston ring motion were studied. Thirdly, it was researched that the variation laws of lubricating oil consumption and piston ring motion with different ring structures and performance. Finally, the impact laws of piston land structure and ring held clearance on blow-by were studied.The results indicate that:(1) Piston tilting angle reduced 18.18%, and rubricating oil consumption reduced 36.60% when the convex position of piston skirt rised from 16mm to 24mm. It does not contribute to reduce noise and lubricating oil consumption when the piston skirt upper increased. But it is conducive to reduce amplitude of piston secondary motion, and lessen lubricating oil consumption when the piston head taper decreased from 0.14mm to 0.1mm. The position of piston hole down to 39mm from original height, the displacement of piston tilting angle is decreased, and either the oil consumption, but blow-by has small change and changes in irregular. The displacements of piston tilting angle, blow-by and oil consumption are all increased as the displacement of cylinder and piston increased.(2) In top ring surface profile, the trapezoid angle and the width of upper end are the main factors to influence oil consumption. It has the minimum oil consumption when surface taper of second ring is 1°, and it has increasing oil consumption when the scraping edge width of second ring increased. The scraping edge width of oil ring has the greatest influence on oil consumption, and maximum increasement of oil consumption is 20.26%. When the tangential elasticity of the three rings take 24N, 18N,50N respectively, oil consumption decreases 2.58%. It has difference influence on piston ring movement by changing different ring structures. The biggest similarity is that, the radial movement of piston ring has significant variation when piston changed direction at top dead center or at bottom head center.(3) The chamfering of the first bottom ring groove has overwhelming effect on blow-by gas quantity. The quantity of blow-by gas has increased rapidly by growth of 63.62% with the chamfering increased from 0.1mm to 0.5mm. The top ring held clearance has the greatest impact on the blow-by gas quantity in the all ring held clearances. And the clearance increased from 0.4mm to 0.7mm, the quantity of blow-by gas is increased by 21.35%. And it has less effect on quantity of blow-by gas by changing second land clearance, third land clearance, and all three ring groove depths.
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