Dynamic behavior of roller chain drives at moderate and high speeds.

Abstract

Dynamic behavior of roller chain drives at moderate and high speeds was investigated by computational analysis. The discrete nature of a chain, dynamic engagement and disengagement of chain links, and series of elastic collisions (and rebounds) occurring in the engagement process were considered. Two sprockets and links in the tight chain span were modeled as rigid bodies connected by pin joints with viscous and Coulomb friction. Equations of motion were derived from Kane's dynamical equations. For precise modeling of the dynamic engagement and disengagement, an analysis of the contact phenomenon between the sprocket and rollers was first completed. The new contact model developed here made it possible to predict the load distribution without resorting to assumptions about the distribution of the contact points. The model indicated that the distribution of contact points on the sprocket is affected by the external loading condition, and this relationship was determined. Effects of friction and dimensional variations in the chain pitch and the sprocket pitch on the load distribution were also investigated. Link tension predicted by the simulation showed excellent agreement with experimental data reported by Naji and Marshek. The simulation of motion of the dynamic chain drive was completed for a range of conditions and the following observations were made. The influence of impact due to collision on the changes in angular velocities of chain links is limited to the first two links and the last two links in the chain span. Modeling of the engagement process through inelastic collision tends to underestimate the effect of impact. The phase between disengagement and engagement is affected not only by center distance, but also by the speed in the dynamic chain drive; the influence of the speed on the phase cannot be predicted by the kinematic model in which inertial effects are neglected. The transverse vibration of the chain span is strongly affected by the phase between disengagement and engagement.