Method of controlling a transmission with power shift clutches and a master clutch

摘要

A transmission, e.g. in a tractor, comprises a power shift gearbox 11 and a second auxiliary range shift gearbox 12. The power shift gearbox 11 has a power shift input shaft 15 which is connected to an engine via a master clutch 14 and power shift output shaft 20 that is coaxial with the input shaft 15. The input shaft 15 has input gearing 16 and the output shaft 20 has output gearing 21. Input and output gearing 16, 21 are connected to their respective shafts 15, 20 by six power shift clutches A-E and R. The method comprises disengaging the master clutch 14 and engaging at least two of a first plurality of power shift clutches A-E when the vehicle speed is below a threshold and disengaging at a second plurality of power shift clutches A-E. Power shift clutches A-E are operated so as to provide a selected gear and the master clutch 14 is engaged and a jerky start of the vehicle is avoided.