Abstract: In order to explore the effect of road excitation on the dynamic balancing characteristics of vehicle engine, and to deeply analyze the reasons for imbalance force and moment variation caused by road excitation, the formulas of engine dynamic balancing parameters with consideration of road excitation are deduced by combining the characteristics of engine working, vehicle traveling and road excitation. Four-post test rig whole vehicle model and engine model are built by using ADAMS/Car ride, ADAMS/Car and ADAMS/Engine. The engine mounting vibrations when the vehicle speeds are 60 km/h, 80 km/h and 100 km/h respectively on a road of certain level are taken as boundary conditions, the overturning moment and internal bending moment of crankshaft are calculated under fixed-base condition and under road excitation condition at crankshaft speed corresponding to vehicle speed gears, and calculation results under the two different conditions are compared and analyzed. The results indicate that the dynamic balancing of engine taking road excitation into account is inferior to that under fixed-base condition, and the degradation amplitude increases in proportional to the increase of vehicle speed. The maximum degradation amplitude can reach up to 9.78%. Moreover, at the same vehicle speed, the higher the gear is, the greater effect of road excitation on the dynamic balancing of engine will be.

Key words: Dynamic balancing, Internal bending moment, Overturning moment, Road excitation, Vehicle engine