Patent ID: 8578809

Claim:
A shifting device ( 11 , 40 ) with a servo-assistance mechanism ( 10 ) for a transmission ( 30 ) of a motor vehicle, the shifting device ( 11 , 40 ) comprising means for selecting and engaging a gear step of the transmission ( 30 ) and control rod ( 20 ) upon which a manual shifting force to be assisted acts such that a performance characteristic curve is produced with the servo-assistance mechanism ( 10 ) which, as a function of one of the manual shifting force and a shift phase, having ranges with different gradients or proportionalities to the manual shifting force, and the servo-assistance mechanism ( 10 ) comprising: a hollow piston rod ( 22 ) which co-operates with means for shifting the transmission ( 30 ) and a valve ( 98 ) comprising a valve piston ( 82 , 104 ) and a valve slide ( 80 , 102 ), the control rod ( 20 ) being partially hollow, the shifting device ( 11 , 40 ) comprising a shifting shaft ( 44 ) and a hollow shaft ( 52 ), and a trailing piston ( 88 , 106 ) that co-operates with the valve ( 98 ) in the servo-assistance mechanism to produce the characteristic curve, the valve ( 98 ) being contained within the hollow piston rod ( 22 ) and surrounding the control rod ( 20 ), a trailing piston spring ( 90 , 108 ) being present upon which a servo-pressure acts, a path limitation means in the control system of the servo-assistance mechanism ( 10 ) and at least one elastic element ( 84 , 110 ) are at least one of provided upstream of and in the servo-assistance mechanism ( 10 ) to limit a servo-assistance force in a path-dependent manner for each gate or each gear, the trailing piston ( 88 , 106 ) being arranged inside the piston rod ( 22 ), surrounding the control rod ( 20 ) and the valve piston ( 82 , 104 ), and resting against an abutment of the piston rod ( 22 ), and the trailing piston spring ( 90 , 108 ) resting, on one side, against an abutment of the piston rod ( 22 ) and, on another side, being connected to the trailing piston ( 88 , 106 ).