Brake booster with solenoid valves

A brake booster including a power piston slidably disposed within a shell, a valve mechanism received in a valve body which is disposed in an axial portion of the power piston, a constant pressure chamber and a variable pressure chamber defined forwardly and rearwardly, respectively, of the power piston, as viewed in the direction of operation thereof, a first passage formed in the valve body for providing a communication between the constant and the variable pressure chamber through the valve mechanism, a second passage formed in the valve body for providing a communication between a source of fluid pressure and the variable pressure chamber through the valve mechanism, an input shaft operating upon a valve plunger, which forms part of the valve mechanism, to change a flow path in order to supply fluid pressure to the variable pressure chamber to cause the power piston to move forwardly, a cylindrical, reentrant portion formed in an axial portion of the shell, and an output shaft having its one end mechanically coupled to the valve body and having its free end projecting externally through the reentrant portion;

• characterized by a solenoid valve disposed within the constant pressure chamber and mounted on the valve body for opening and closing the first passage.