Patent ID: 8788163

Claim:
A method of operating a vehicle drive-train ( 5 ) which comprises a drive machine ( 2 ) and a transmission device ( 3 ), and during a gearshift in the transmission device ( 3 ) at least one interlocking shifting element (F) is disengaged and at least one frictional shifting element (B) is engaged, the method comprising the steps of: initiating monitoring, at a time (T 1 ) of a shift command, of a shifting time and either a transmission input speed or a rotational speed equivalent to the transmission input speed; recognizing that the interlocking shifting element (F) is in a disengaged operating condition, if the monitored transmission input speed or the rotational speed equivalent thereto deviates from a synchronous speed equivalent to a gear ratio (“ 4 ”) to be disengaged in the transmission device ( 3 ); adjusting a current drive torque (m_mot) of the drive machine ( 2 ) if an engaged operating condition of the interlocking shifting element (F) to be disengaged is detected after a lapse of a pre-defined time interval (t 7 ) that begins at the time (T 1 ) of the shift command, by motor actuation (me) to a torque level that corresponds to a difference between either a current transmission input torque or a torque value equivalent thereto and a torque that is transmittable by the frictional shifting element (B) to be engaged, operating with slip, plus a torque offset value, and at which the interlocking shifting element to be disengaged changes, at least for a time, to an at least approximately load-free operating condition such that a transmission capacity of the frictional shifting element (B) to be engaged, during traction operation of the vehicle drive-train ( 5 ), is brought to a traction torque value level (m_mot(zug)) equivalent to the transmission input torque; adjusting the transmission capacity of the frictional shifting element (B) to be engaged, if a load change takes place in the vehicle drive-train ( 5 ) during the gearshift, to a thrust torque value level (m_mot(sub)) equivalent to the current transmission input torque; and operating the frictional shifting element (B) with slip at least while the interlocking shifting element (F) is engaged.