Patent ID: 8155849

Claim:
A hydraulic actuating device for an automotive friction clutch comprising: a master cylinder having a master piston, which can be subjected to a master force (F G ) via an actuating mechanism and can be displaced by a master travel (s G ) as master variables, and a slave cylinder with a slave piston which is hydraulically connected in series to the master piston said slave piston being actually connected to a clutch-release member of the automotive friction clutch, an adjusting unit which has an adjusting piston which can be subjected to a force and displaced via a transmission that is driven by an electric motor, is arranged in series between the master piston and the slave piston so that the force acting on the slave portion of the liquid column can be increased in a defined manner by subjecting the adjusting piston to force via the transmission, and divides the liquid column between the master piston and the slave piston into a master portion between the master piston and the adjusting piston and a slave portion between the adjusting piston and the slave piston, a control unit that controls the electric motor, a first sensor device which is signal-connected to the control unit and by which a master pressure (p Gactual ) in the master portion of the liquid column or the master force (F Gactual ) can be detected as control variable, and a second sensor device which is signal-connected to the control unit and by which a slave travel (s Nactual ) of the slave piston, an adjusting travel (s sactual ) of the adjusting piston, the master travel (s Gactual ) of the master piston or a variable proportional thereto can be detected as guide variable, wherein the control unit as a memory element in which a desired curve (p Gnominal =f(s Sactual ); F Gnominal =f(s Gactual )) of the control variable (p G ; F G ) relative to the guide variable (s N ; s S ; s G ) is stored, from which an associated nominal value for the control variable (p Gnominal ; F Gnominal ) can be determined for each actual value of the guide variable (s Nactual ; s Sactual ; s Gactual ) detected by the second sensor device, so that a nominal value for the master pressure (P Gnominal ) or the master force (F Gnominal ) can be determined in the control unit as a function of the detected slave travel (S Nactual ), adjusting travel (s sactual ), master travel (s Gactual ) or the detected variable proportional thereto, and wherein the determined master pressure (p Gnominal ) or the determined master force (F Gnominal ) can be set via the electric motor of the adjusting unit which is controlled by the control unit.