Method for operating a transmission device of a vehicle drivetrain

A method of operating a transmission device (10) of a vehicle drive-train (1) that comprises a plurality of frictional shifting elements (A, C to E) and at least one interlocking shifting element (B) for obtaining various gear ratios (“1” to “R”), wherein in a neutral operating condition (“N”) of the transmission device (10), in which a force flow is interrupted in an area of the transmission device (10), and in a case of an operating condition variation of the vehicle drive-train (1) in which, when required to establish the force flow in the transmission device (10), the at least one interlocking shifting element (B) has to be changed from a disengaged to an engaged operating condition, the method comprising the steps of:

• increasing transmission capacities of at least two frictional shifting elements (A, C), which have to be engaged to produce the force flow, to a level at which the frictional shifting elements (A, C) operate in a slip-free condition,
• determining a rotational speed difference (nd_B) in an area of the interlocking shifting element (B), and
• adjusting a drive torque (m_mot) of a drive machine (9) to a level that brings the rotational speed difference (nd_B) in the area of the interlocking shifting element (B) to within a predefined speed difference range (nd_Bo, nd_Bu) such that within the predefined speed difference range (nd_Bo, nd_Bu), the interlocking shifting element (B) is in an at least an approximately synchronized condition and can thus be engaged.