Design of a new power-split infinitely variable transmission

In the last few decades, power-split infinitely variable transmission (PS-IVT) systems have attracted considerable attention as they ensure high driving comfort with high total efficiency, especially in off-highway vehicles and agricultural machines. In this study, a novel power-split-input-coupled IVT system was developed to gain an advantage in fuel consumption. Although the efficiency of the PS-IVT is known to be lower than that of a conventional transmission, it can reduce fuel consumption by allowing the control of the internal combustion engine in an optimum way by allowing the continuous transmission ratio. This study is intended to obtain lower fuel consumption values by employing PS-IVT as compared to conventional transmission. The effects of various dynamic parameters such as power flow and Willis transmission ratio on the mechanical efficiency of the system were investigated. Kinematic analysis of the new system was carried out and in addition, power flow equations were derived as functions of the power that flows through the infinitely variable unit (IVU). Results of the kinematic analysis indicate that the main parameters, which are strictly related to mechanical efficiency are the power and torque flows through the IVU. The developed transmission system was then compared with a conventional transmission in terms of fuel consumption on the virtual track by using the longitudinal vehicle dynamics model. In order to determine the fuel consumption values were obtained by two different types of transmission, GPS data of a real tractor at real time from the real user in real world conditions were collected. Driving resistances for the considered vehicle were determined with the longitudinal vehicle dynamics model. Dynamometer test and theoretical calculations based on the kinematic model developed in this study were carried out to determine the mechanical efficiencies of the conventional transmission and the PS-IVT respectively. Fuel consumption values obtained using different types of transmissions were compared in terms of mass by using a BSFC map of a four-cylinder common-rail turbo diesel engine. Fuel consumption simulations were performed in MATLAB environment, and two different power management strategies with eight different scenarios were evaluated. It is found that a reduction of 8.2% in fuel consumption compared with the conventional transmission can be achieved by the proper power management strategy for the PS-IVT.