Analysis and Design of Sprocket Driven Transmission System

Roller chain drive is widely used in timing mechanism of gasoline engine. However, its polygonal action and meshing impact effect resulted from the non-conjugated meshing feature may damage the synchronization and uniformity of transmission. In this paper, new sprocket tooth profile is developed to reduce polygonal action under high speed. A new conjugated profile is derived by modifying involute profile to guarantee that the moving distance of chain is equal to the arc length of pitch circle that a sprocket rotates. Also the center line of chain at tight side is always tangent to the pitch circle. The fluctuation of the chain are analyzed under different rotational speeds. The results show that newly developed sprocket profile can efficiently reduce meshing impact and friction of chain and also the stability of chain transmission under high speed can be improved.