Pre-filling device for a braking system comprising a hydro-booster device and operating method thereof

A pre-filling device configured to operate in a braking system, the braking device including a hydro-booster device arranged to generate a hydro-boost pressure, and a master cylinder chamber having a hydraulic piston for brake control, the pre-filling device comprising:

• a pre-filling channel, a pre-filling pressure being provided inside the pre-filling channel when the braking system is in a rest and hydro-boost position;
• a mechanical valve configured to be mechanically opened following a transition from the rest and hydro-boost position to a working position of the braking system, and to connect the pre-filling channel to the master cylinder chamber;
• a hydraulic valve configured to cooperate with the mechanical valve for setting the pre-filling pressure inside the pre-filling channel, the hydraulic valve including, in a first area facing the mechanical valve, a hole communicating with the pre-filling channel, and in a second area, hydraulically isolated from said first area and opposite to said first area, a preloaded resilient element housed in a chamber held at atmospheric pressure, the hydraulic valve being configured to be connected, through the hole, to the hydro-booster device, or to be disconnected therefrom, by a reciprocating movement inside the pre-filling channel, so as to effect adjustment of said pre-filling pressure inside the pre-filling channel upon variation of the hydro-boost pressure, the adjustment depending on a difference between a pressure exerted by the preloaded resilient element and the atmospheric pressure.