Steady-state and start-up transient responses of a belt-driven starter generator system for micro-hybrid electric vehicles

For micro-hybrid electric vehicles, the belt-driven starter generator system is a typical idle stop–start system that is used to substitute the traditional engine front-end accessory drive system. The aim of this work is to present a method to investigate steady-state and start-up transient responses of a typical belt-driven starter generator system with twin tensioner arms for micro-hybrid electric vehicles. A dynamic model of the belt-driven starter generator system is established for this scheme, where a smoothing dynamic friction model considering the velocity-weakening effect is presented to model the tensioner dry friction. Unlike some traditional dynamic models of the belt-driven starter generator system that the engine dynamics and dynamics of the belt-driven starter generator system are decoupled, an engine dynamic model, which is embedded in the dynamic model of the belt-driven starter generator system, is also established to calculate engine resistance torques at the engine starting process stage. Influences of the tensioner dry friction and stiffness on steady-state responses of the belt-driven starter generator system especially the stick–slip oscillations of the twin tensioner arms are examined. Angular oscillations and rotation speed variations of the belt-driven starter generator pulley and C/S pulley as well as the belt tension variations during the engine starting process are calculated. Influences of the tensioner dry friction and stiffness on transient dynamic performances of the belt-driven starter generator system during the engine starting process and its starting efficiency are investigated.