Clutch fill control of an automatic transmission for heavy-duty vehicle applications

In this paper an integrated clutch filling phase control for gearshifts on wet clutch transmissions is developed. In a clutch-to-clutch shift of an automatic transmission, in order to obtain smooth gearshift, it should synchronize the oncoming clutch and the off-going clutch timely as well as precise pressure control for the engagement of the oncoming clutch. However, before the oncoming clutch pressure starts to increase, the initial cavity of the clutch chamber has to be filled first. The filling time and stability of the fill phase are very important for the clutch control. In order to improve the shift quality of the automatic transmission which is equipped on heavy-duty vehicles, the electro-hydraulic clutch actuation system is analysed and modelled. A new fill phase control strategy is proposed based on the system analysis as well as the control parameters are optimized according to the variation of the oil temperature and engine speed. The designed strategy is validated by a simulation work. The results demonstrate that the proposed control strategy and parameters modified method can transit the shift process from the fill phase to the torque phase effectively.