Work strategies of torque converter for vehicle with continuously variable transmission system

In order to improve the operating fuel economy of torque converter for vehicle with continuously variable transmission (CVT) system, the optimal lock-up and unlocking conditions were confirmed.To furtherly improve the work efficiency of torque converter in unlocking stage, PID controller was designed, so that engine and torque converter worked in optimal economy region by adjusting the speed ratio of CVT.To decrease the impact during the lock-up process of torque converter, the control strategies of lock-up clutch engagement were put forward according to the principles of stabilizing engine rotation and optimizing the performance of impact and sliding friction work, and the fuzzy controller with two inputs of impact degree and rotate speed difference was designed.The experimental result under two kinds of different lock-up states shows that the 1.92 s in quick acceleration is bigger than the 1.38 s in slow acceleration, the engagement time is prolonged, so the control measures can ensure the engaging smoothness of torque converter and stabilize engine rotate speed.