Electrical power-steering system for a motor-vehicle

An electrical power-steering system for a motor-vehicle, comprising:

• a driving shaft connected or adapted to be connected to the steering column of the motor-vehicle;
• a first pinion driven by said driving shaft and meshing with a first portion of a rack member provided for controlling a steering angle of two wheels of the motor-vehicle;
• a first electric motor connected to said driving shaft, for applying thereto a steering-assist torque;
• electronic control means for controlling said first electric motor on the basis of an input signal indicating the torque and/or the angle of rotation of the steering column;
• a second pinion meshing with a second portion of the rack member;
• and
• a second electric motor that drives said second pinion and that is controlled by said electronic control means;
• said first portion and said second portion of the rack member that mesh with said first and second pinions respectively associated to said two wheels of the motor-vehicle and comprise two separate elements connected to each other by a connection member interposed therebetween, such that said first and second portions of the rack member behave like a single rigid element when they are driven with identical displacements in a steering maneuver of the vehicle, whereas said connection member allows for a relative movement in the longitudinal direction of said first and second portions of the rack member, with a resulting lengthening or shortening of said rack member, when said first and second portions of the rack member are driven with differentiated displacements in an operative mode for adjustment of the angle of convergence of said wheels;
• said electronic control means configured for driving said first and second pinions identically during a steering maneuver of the vehicle, in such a way as to cause identical longitudinal movements of said first and second portions of the rack member, whereby during the steering maneuver said portions of the rack member behave like a single rigid element;
• and
• said electronic control means configured for driving said first and second pinions in a differentiated way, with the vehicle stationary or in motion, in the operative mode for adjustment of the convergence angle of said wheels, so as to cause a mutual longitudinal displacement of said first and second portions of the rack member, with a resulting lengthening or shortening of said rack member, which causes a variation in the convergence angle of said wheels.