System for the assisted selection of the ratios of an automobile gearbox

A system for the assisted selection of the ratios of a gearbox of an automobile vehicle, said gearbox having an input element movable in rotation and in translation for effecting a selected ratio, said system comprising an electrohydraulic actuator in combination with said input element for driving said input element, and said actuator comprising in combination cylinders operatively connected to said input element, and a group of binary solenoid valves operatively connected to said cylinders for driving said input element in translation and in rotation as a function of instructions, wherein the gearbox operates by means of shifting forks, and said input element is a shaft comprising a rocker fixed thereto and having a plurality of lateral arms, rotation of said input element and said rocker being operative to select a fork corresponding to the selected ratio, and movement in translation of said input element being operative to engage the selected ratio by a displacement of the selected fork, said actuator comprising two opposed hydraulic cylinders operative for causing rotation of said rocker and disposed on each side of said shaft and each cooperative with an associated one of said lateral arms, each cylinder comprising a body, a piston movable in said body, a cup surrounding said piston and connected to said piston and movable in translation in said body between two end positions of abutment, an inner end of said cup located on a side remote from an end of said piston engaged with the respective lateral arm of said rocker being provided with a port opening onto a hydraulic chamber in said body, and a corresponding solenoid valve for supplying fluid under pressure to said hydraulic chamber.