Method for shifting down with negative engine torque, for a dog gearbox

摘要

The method involves actuating a synchronizer sleeve (24) and adjusting a torque capacity of an input clutch (4). N-initial ratio is disengaged, and torque level is maintained by the clutch and an engine torque according to the desire of a driver, while the synchronizer torque is controlled to remain higher than clutch torque for increasing real speed of a main shaft (6). N-1 final ratio is engaged when the speed of the shaft comes closer to the speed of the final ratio. The sleeve is progressively deactivated, and the clutch is subsequently/simultaneously closed. An independent claim is also included for a dog gearbox of a motor vehicle comprising actuators.