Study on Reducing the Mower Vibration by Optimizing the Crank-rod Mechanism of 170F Engine
|Keywords||general purpose gasoline engine crank-rod mechanism vibration simulation|
In this paper, taking 170F general purpose gasoline engine for example, the motion analysis, dynamics calculation and computer simulation analysis of the crank-rod mechanism were analyzed; the inertia force and balance methods of the small single cylinder internal combustion engine without balance shaft was study. Crank-rod mechanism optimization design combining with practical vibration test of the handlebar of the mower, reduce the vibration of engine caused by the inertia force, and effectively control the vibration of the mower in a reasonable range.With UG, establish the three-dimensional geometric model of piston, connecting rod, crankshaft, etc., and assembly into the crank-rod mechanism, and then import the multi-body dynamics simulation software and optimization analyze. And calculate the natural frequency of the crankshaft and crankcase on its free state by CAE, which provide that frequencies of sympathetic vibration are avoided in the rotate speed range of engine. The new structure designs are used in the crank of the crankshaft, and then fatigue strength of crankshaft is verified by experiment, and functional reliability of the crankshaft is ensured.Without considering frictions of the moving parts, gas pressure in the cylinder and output of the crankshaft, calculate the inertia force of the crank-rod mechanism of 170F engine. By both dynamic calculation and the vibration feel to compare, and multi-body dynamics calculation to optimize, made two comparing crankshaft with different the mass-radius product. Install them into the engine, and compare the vibration of the handlebar of the mower. The results show that: when the unbalance rate is 55-60%, the vibration feel of the handlebar is good; when the unbalance rate is 58%, the vibration feel reach the vibration level of the target engine, and above 2000r/min rotating speed the feel is better than the target engine.