Modelagem computacional do funcionamento de uma transmissão continuamente variável (CVT) aplicada em um protótipo do tipo BAJA SAE

Abstract

With the growth of the automotive market, environmental concerns and customers increasingly demanding about comfort, performance, and fuel economy, it becomes necessary to evaluate options to satisfy these requirements. The use of continuously variable transmissions (CVT) is becoming an alternative to satisfy these need. This type of transmission allows the engine to work at its maximum efficiency speed, varying its transmission ratio continuously, without abrupt changes in torque or exit speed, while vehicle speed increases. This work aims to present the development of a numerical simulation model that aims to evaluate the dynamic behavior of a Baja SAE vehicle of the Bombaja UFSM team, through the modification of constructive characteristics (mass of flyweights) of the CVT. Due to the complexity of the CVT behavior and the high experimental testing time with this component, this tool is intended to minimize the team's testing time and provide analysis and quick decisionmaking in choosing the best configuration of the component that will provide the best longitudinal performance of the vehicle. With the help of the Matlab® software, simulations were carried out considering the forces coming from the motor and driven pulley drives, in addition to the resistive forces to the vehicle's movement, which directly interfere in the longitudinal performance of the prototype. In order to compare the results obtained through the simulations carried out, an experimental procedure was carried out using flyweights with a mass of 100 grams and the prototype submitted to cover the same path of the acceleration and velocity test (A&V). During the path, the angular speed of the prototype's front and rear wheels, engine rotation, and displacement time on the course were measured. The comparison between the results obtained through the experimental tests with the simulation presented satisfactorily close values, however, the results obtained through the simulation presented more conservative values because the computational model does not consider the effects of V-belt slippage on the CVT pulleys, as well as, disregard the losses that occur between the tire-track pair.