Zf Friedrichshafen Ag

Valentine Vincent

Thilo Schmidt

Klaus Steinhauser

Markus Herrmann

Anton Fritzer

Andreas Schmidt

Gerhard Hermann Martin

Mario Hasel

Rainer Grundler

Christoph Köhler

Jonas Knör

Dirk Winkler

Jakob Mayer

Michael Miller

Ahmed Mouhcine

Fabian Schöniger

Christian Hunger

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

A drag torque reduction device for an automatic transmission includes a hydraulic controller with a radiator. In one embodiment, the drag torque reduction device also includes a parallel connection of a pressure relief valve, a constant aperture and a temperature-dependent, switchable aperture positioned upstream of the radiator. In another embodiment, the drag torque reduction device includes an overflow cooling oil diversion with a temperature-dependent, switchable aperture and a pressure relief valve that is positioned upstream of the radiator.

Device reducing drag loss in an automatic transmission

In a method for operating an automatic transmission having multiple frictional-locking shifting elements and at least one positive-locking shifting element, for the representation of a transmission ratio stage, at least three shifting elements are closed. For a shifting process between two specified transmission ratio stages, at least two shifting elements are opened and at least two shifting elements, including at least one positive-locking shifting element and at least one frictional-locking shifting element, are closed. In the chronological sequence of the shifting process, the closing of the positive-locking shifting element takes place only after all frictional-locking shifting elements are closed.

Method for operating an automatic transmission

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Friedrichshafen, Germany

Valentine Vincent