Method for shifting a gear in a multi-stage gearbox of a motor vehicle as a function of the drive input shaft rotational speed

Abstract

Method for shifting, in particular engaging and/or disengaging, gears in an automatic multi-stage gearbox of a motor vehicle, wherein the gearbox comprises a drive input shaft () connectable to an engine drive output shaft () by means of a friction clutch () which acts as a separating clutch (), and a drive output shaft () couplable to a drive wheel or to drive wheels of the motor vehicle, wherein a shift process takes place, in particular only, as a function of rotational speeds (n) of the shafts, wherein each gear is assigned a synchronizing device (), which acts as a shift clutch, in order to connect the drive input shaft () to the drive output shaft (), comprising the following steps: setting the separating clutch () into a dragging position such that a low, preferably predefined, drag torque is transmitted from the engine drive output shaft () to the drive input shaft (), which drag torque is sufficient to bring a rotational speed (n) of the drive input shaft () when the shift clutch () is open to a rotational speed (n) of the engine drive output shaft (); adjusting the rotational speed of the engine drive output shaft () to a predetermined value (I) which differs sufficiently from a rotational speed of a source gear or from rotational speed of a target gear; setting the shift clutch () of the source gear towards an open position in order to separate the drive input shaft () and drive output shaft () from one another; detecting the rotational speed (n) of the drive input shaft for a predetermined time period which follows at least a time (t) when the shift clutch () of the source gear is in the open position; determining a change in the rotational speed (n) of the drive input shaft () during the predetermined time period; and determining whether the change which is determined in this way lies within predefined tolerances of an expected rotational speed change (FIG.).