Design of Ball-Ramp dual clutch transmission to reduce uncertainties in clutch actuator and tie-up effect

Abstract

Dual-clutch transmissions (DCT) have high efficiency, low drop in tractive force during shifting, and fast shifting is possible. However, it is infeasible to measure clutch torque due to cost and durability problems, and difficult to control clutch torque due to change in friction coefficient. Also, the energy consumed by the actuator for maintaining engagement is large. To address these limitations, a Ball-Ramp DCT (BR-DCT) was developed based on the self-energizing principle. The BR-DCT can reduce energy consumption of the clutch actuator. In addition, it is possible to reduce the uncertainties in actuator by using only measurable values to calculate the actuator input; and, when a tie-up occurs in which two clutches are engaged at the same time, the magnitude of negative torque can be reduced. However, design constraints for implementing last two features were not addressed in previous studies. In this paper, we propose the two design constraints to reduce the uncertainties in actuator and reduce the tie-up effect. For verification, a BR-DCT prototype and powertrain test bench were manufactured with the design constraints. As a result of the shift experiment, it was verified that accuracy of the actuator model can be improved, and the tie-up effect can be reduced.