CAR20111236 DYNAMIC MODEL FOR THE PULL-BELT CVT SIMULATION 1 Preda, Ion * , 1 Ciolan, Gheorghe, 2 Cristea, Dumitru, 2 Diaconescu, Eugen, 2 Lefter, Emilian 1 Transilvania University of Brasov, Romania, 2 University of Pitesti, Romania KEYWORDS – pull-belt CVT, actuation system, control, dynamic model, simulation ABSTRACT – The continuous variable transmissions (CVT’s) permit to obtain any value of the transmission ratio between two limits. The continuous variation of the transmission ratio can be used to permanently adapt the engine functioning to the actual vehicle’s movement conditions, promising important fuel efficiency increase and lower pollutant and CO 2 emissions. On the other hand, this type of transmission is not an automatic one by its working principle, which means a change of the vehicle’s road load will not automatically adapt the transmission ratio. Due to that inconvenient, extended researches are made today to improve the performances of the CVT’s hydraulic or electric actuation systems, controlled both by mechanical and electronic devices. The CVT’s model presented in this paper was designed to represent the base for the study of different controlling algorithms’ performances. The authors’ intention is to include the CVT’s control level in another higher control system of a hybrid propulsion system. Finally, some simulation results are also presented. MANUAL TRANSMISSION VS. CVT The continuous variable transmissions (CVT’s) are transmissions incorporating a so called mechanical variator. Having a working principle based on mechanical friction, this device is used to adapt the engine’s power parameters (angular speed and torque) to the instantaneous vehicle need. Fig. 1: Experimental data recorded in city traffic with a manual transmission car right – record fragment of vehicle speed vs. time, with the emphasizing of the engaged gear; left – relative probability density of the engaged gear vs. vehicle speed