An Investigation into Dynamics and Stability of a Powertrain with Half-Toroidal Type CVT

This paper presents a study on the dynamics and stability of a conventional powertrain with a Half Toroidal (HT) type Continuously Variable Unit (CVU). A mathematic system model of the powertrain is assembled from parametric finite elements that are formulated from lumped mass, torsional stiffness and damping and varying gear ratios. Simulations have been carried out to investigate the transient behaviour of the powertrain. The damping within the system has been varied to investigate its effect on the dynamic stability of the powertrain. The obtained results show that transient responses of input and output rollers of the HT-CVU exist when clutch changes during vehicle acceleration period starting from standstill condition. Severe or even unstable responses of HT-CVU take place if the damping is insufficient in HT-CVU and tyres not only in the initial acceleration period but also in later period after the clutch change. The response of the powertrain becomes stable again when a lock-up clutch is applied even if the damping in tyres remains insufficient.