Application of the non-circular sprocket in the timing chain drive system

As a fundamental component of hybrid vehicles, the timing chain drive system significantly improves fuel economy while minimizing transmission error. A non-circular sprocket is used in a timing chain drive system to improve the dynamics characteristics of the system. In the scheme to reduce the crankshaft speed fluctuation, the relationship between the transmission ratio and the camshaft rotation angle is determined by analyzing simulation and experimental results. The mathematical relationship between the transmission ratio and the pitch curve of the non-circular sprocket is deduced. The pitch curve and phase angle of the non-circular sprocket are calculated. Combined with the self-constructed dynamics model of the hydraulic tensioner, a complete three-dimensional timing chain drive system simulation model is established based on the recursive algorithm and Hertz contact theory. The non-circular sprocket is installed into the system at the initial mounting angle. Dynamics simulations are carried out taking into account actual operating conditions. The simulation results prove that the use of a non-circular crankshaft sprocket can effectively reduce speed fluctuation of the camshaft sprocket, transmission error, and maximum chain tension when the crankshaft speed fluctuates regularly. This research proposes and validates a method to improve the dynamics characteristics of the system.