Zf Friedrichshafen Ag

Michael Miller

Jonas Knör

Thilo Schmidt

Anton Fritzer

Andreas Schmidt

Mario Hasel

Christoph Köhler

Valentine Vincent

Jakob Mayer

Philipp Kölbl

Christian Hunger

Fabian Schöniger

A method for operating a friction-locking shift element of a transmission of a motor vehicle includes actuating the friction-locking shift element for engagement according to a pressure versus torque characteristic curve. The pressure versus torque characteristic curve has a first characteristic point (a touch point) and a second characteristic point (a contact point), defines a first characteristic curve range between the touch point and the contact point having a first functional dependence, and defines a second characteristic curve range at or after the contact point having a second functional dependence. Once the touch point is reached, the friction-locking shift element begins to transmit torque mainly due to drag torques. Whereas, once the contact point is reached, the friction-locking shift element begins to transmit torque mainly due to friction between shift-element halves of the friction-locking shift element.

Method for operating a friction-locking shift element of a transmission, and control unit

A vehicle transmission includes a hydraulic circuit and a control unit. The control unit is configured to: obtain () a target pressure specification; convert () the target pressure specification into a target volume flow rate; determine () a valve volume flow rate as a function of the target volume flow rate and as a function of parameters that represent system properties of the hydraulic circuit; determine () a pressure drop at a valve due to flow forces as a function of the valve volume flow rate; determine () a compensated valve output pressure as a function of the valve volume flow rate and the pressure drop; determine () the electric control current as a function of the compensated valve output pressure; and activate a valve with the electric control current.

Method for the open-loop control of an electrically controllable valve in a vehicle transmission

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Leutkirch, Germany

Michael Miller