The Meshing Mechanism And Dynamic Analysis Of Composite Profile Silent Chain Sprocket

Silent chain drive is widely used in the timing mechanism of gasoline engine, such as motorcar and motorcycle engine. However the polygon movement and the meshing contact effect of silent chain drive damages the synchronization and uniformity of transmission. It is necessary to develop new kind of silent chain drive to improve the transmission performance of silent chain mechanism.First of all, the polygon movement and the meshing contact of silent chain drive are analyzed and the design of a new tooth profile sprocket is developed. The normal sprocket profile is modified refer to involute sprocket profile. A new sprocket profile is designed by integrating the involute and beeline. At the beginning of a meshing circle, the straight tooth form of the silent chain engages with the involute sprocket form. At the end of a meshing circle, the silent chain engages with the beeline sprocket form. So the meshing impact is reduced and the driving performance is improved.Secondly, the rigid dynamic models of three silent chains (including the normal , involute and composite profile sprockets) are built by means of the 3-D modeling and mechanical dynamic analysis technology. The dynamic simulation of drive wheel at speeds of 500r/min to 8000r/min is achieved. The analysis results show that the tight side fluctuation of the silent chain of composite profile silent chain mechanism reduces compared with that of conventional silent chain mechanism. The meshing contact and the driven wheel angle velocity nonuniformity coefficient decrease, too. The transmission performance of three kinds of silent chain mechanisms is compared by the experiments on the test-bed. The free frequency of the test-bed is measured and analyzed in order to avoid the resonance. The tight side fluctuation and noises of the three kinds of silent chain mechanisms are measured. The experimental results show that the tight chain fluctuation of composite profile silent chain mechanism reduces by 17% compared with that of involute sprocket silent chain drive. The driven wheel angle velocity nonuniformity coefficient and the noise value of composite profile silent chain mechanism are lowest in the three kinds of silent chain mechanisms. Therefore using the composite profile silent chain can reduce the vibration and the noise and improve the high-speed driving performance.This project is supported by National Natural Science Foundation of China (Grant number 50375085).