Simulation and experimental study on the pump efficiency improvement of continuously variable transmission

To reduce the power loss of a pump in continuously variable transmission (CVT), a new hydraulic scheme is proposed. This new scheme adjusts the effective displacement of the pump by using lubrication pressure and controls the pressure of primary and secondary cylinders through the smart mode. The power matching model of the new hydraulic scheme is established. The models of hydraulic system, vehicle and transmission control unit are built. A closed loop is formed to place the software in loop simulation through Silver virtual integration platform. The simulation results show that the new hydraulic scheme can match the power demand well. In NEDC, the hydraulic efficiency of the new hydraulic scheme can increase by 24.7% and 23.6% compared with those in the quantitative and single pumps, respectively, the fuel consumption of the new hydraulic scheme can reduce 3% and 4.1% compared with those in the single and quantitative pumps. Finally, the new hydraulic scheme is verified through the bench test, which reveals that the variable pump of the new hydraulic scheme can considerably reduce the torque loss of the pump, the smart mode can improve the transmission efficiency of CVT by up to a maximum rate of 3.17%.