Braking pressure generator for a hydraulic brake system for automotive vehicles

A braking pressure generator for a hydraulic brake system for automotive vehicles, with a master brake cylinder whose working chamber is in communication with an unpressurized compensating reservoir in the brake release position via a valve closable by the actuating stroke of the master cylinder piston, and with a hycraulic brake power booster connected upstream of the master brake cylinder and comprising a booster piston designed as a stepped piston, which latter penetrates the booster chamber and is composed of two pistons of differing effective surfaces movable in relation to one another and being applicable in opposed directions by the pressure in the booster chamber and comprising stops which limit their relative movement to an amount which at least corresponds approximately to the closure travel of the valve in the master brake cylinder, both pistons being movable by resilient means to abut on one another in the direction of brake release, and the piston of smaller effective surface being movable to abut on a housing stop, wherein the two pistons (10, 16) enclose a pressure chamber (23) which is enlargeable by their moving apart and which is connected to the booster chamber (8) through a valve passage (19), and in that the valve passage (19) is closable at least in the event of the brake power booster (1) being at its maximum output.