SERVO BRAKE BOOSTER WITH TWO DIFFERENTIATED FIXED AND VARIABLE JUMPS

摘要

The invention concerns a pneumatic servo brake booster (10) comprising a mobile piston (22) stressing an actuating rod (34) of a master cylinder (28) in response to the actuation of a plunger (56) whereof one front end, passing through the piston (22) and forming a first probe (62) can, in the extreme position of the plunger (56), penetrate a first reaction disc (44) interposed between the piston (22) and the actuating rod (34) to transmit to the plunger (56) the reaction force of the master cylinder (28). The invention is characterised in that it comprises a second probe (68) which can, when the control rod (46) is actuated at a speed higher that a predetermined speed be pushed by the plunger (56) and locked by a one-way clutch device (70) along a variable axial position relative to the piston (22), then driven by the piston to push the second probe (68) into the disc (44) so that the first probe (52) applies a braking force more rapidly.