Braking device using an integrated master-cylinder brake booster

A braking device, comprising a pneumatic servomotor (1) for an assisted braking and a master cylinder (2), the servomotor (1) comprising:

• a rigid casing (10);
• a moving partition wall (11), dividing the rigid casing (10) into a front chamber (101) and a rear chamber (102), selectively under one and the same first pressure (P1), or respectively under the first pressure (P1) and under a second pressure (P2), which is higher than the first one (P1);
• a pneumatic piston (12), travelling with the moving partition wall (11);
• a plunger (13) accommodated inside the pneumatic piston (12) and selectively driven by a control rod (14), which is movable relative to the pneumatic piston (12), under the action of a return force (Fr) and of an actuation counterforce (Fa), between a rest position and a maximum actuation position;
• a three-way valve (15), controlled by the position of the control rod (14) and controlling the pressure inside the rear chamber (102);
• and a reaction means (16) for applying, to the plunger (13), a reaction force dependent on the actuation force (Fa), and wherein the master cylinder (2) comprises:
• an elongate body (20) provided with a longitudinal bore (21) having an opening (210) and an end wall (211);
• primary and secondary coaxial pistons (221, 222), each of them being slidably fitted in the bore (21) in an airtight manner, between a rest position and a maximum actuation position, wherein the primary piston (221) is integral with an actuating rod (23) passing through the opening (210) of the bore;
• a primary pressure chamber (241), defined between the primary and secondary pistons (221, 222);
• and a secondary pressure chamber (242), defined between the secondary piston (222) and the end wall (211) of the bore, characterised in that the body (20) of the master cylinder (2) is integral with the pneumatic piston (12) and slidingly fitted inside the front chamber (101), in that the actuating rod (23) is hollow, integral with the rigid casing (10) and communicates with the primary pressure chamber (241), and in that the secondary piston (222) is traversed, in an airtight manner, by a passage (25) communicating with the secondary chamber (242), and extending through the primary chamber (241) and the actuating rod (23), while being stationary in relation to the rigid casing (10).