Patent ID: 7086321

Claim:
A boosted brake ( 10 ) for a motor vehicle, comprising a pneumatic brake booster ( 12 ) for actuating a master cylinder ( 14 ) having a rigid casing ( 16 ) inside which can move a transverse partition ( 18 ) sealably delimiting a front chamber ( 20 ) subjected to a first pressure (P 1 ) and a rear chamber ( 22 ) subjected to a second pressure (P 2 ), a moving piston ( 24 ) fixed to the moving partition ( 18 ) and comprising a front face ( 26 ) that acts on a primary piston ( 30 ) of the master cylinder ( 14 ) by way of a reaction disk ( 28 ) which is fixed to a rear end of the primary piston ( 30 ), a control rod ( 36 ) which moves in the piston ( 24 ) selectively as a function of an axial input force exerted forward against a return force exerted on the rod ( 36 ) by a return spring ( 38 ), said control rod ( 36 ) having a front end comprises at least one plunger ( 40 ) which is mounted slideably in the piston ( 24 ) and is connected to at least one annular seat of a valve ( 42 ) which is able to set up in the rear chamber ( 22 ) a second pressure (P 2 ) which is greater than the first pressure (P 1 ) prevailing in the front chamber ( 20 ) so as to cause the moving partition ( 18 ) to move a feeler ( 44 ), arranged at the front end of the plunger ( 40 ) and passing through a bore ( 46 ) leading from the piston ( 24 ), which, when the control rod ( 36 ) is in a rest position, is arranged at a defined jump distance from the reaction disk ( 28 ) and when the control rod ( 36 ) is actuated with an input force whose intensity is greater than a first defined intensity, to come into contact with the reaction disk ( 28 ) in such a way as to transmit to the plunger ( 40 ) and to the control rod ( 36 ) the reaction force of the master cylinder ( 14 ), characterized in that a front end ( 48 ) of the feeler ( 44 ) comprises at least one stud ( 50 ) which projects parallel to the axial direction and enables the feeler ( 44 ), in at least one part of a jump phase (PS) during which it covers the jump distance before coming fully into contact with the reaction disk ( 28 ), to provide proportionality between the force which is transmitted to the front end ( 48 ) by the plunger ( 40 ) and the force exerted on the primary piston ( 30 ) of the master cylinder ( 14 ).