BRAKE BOOSTER DEVICE, WITH IMPROVED OPERATING CONDITIONS, FOR MOTOR VEHICLE

摘要

The invention concerns a braking device comprising a master cylinder (2), a primary piston (3), a manual control member (4), a brake servo unit (6) coupled with the manual control member (4) and an emergency power valve (VA) comprising a reaction piston (17) traversed by a ratio control unit (T) having a head (26a) located in a chamber (35) between the reaction piston (17) and a bushing (36) arranged further forward in a bore (18) of the primary piston, said bushing (36) comprising a bore (37) wherein can slide a fast piston (38) whereof the rear end (45) forms with the head (26a) of the ratio control unit a valve (C) adapted to close the entrance of a passage (39) of the fast piston countering the action of a spring (41). The device comprises means (26, 27, 30) for preventing a sudden slip of the reaction piston (17) when the manual control member (4) is released after slow braking.