Patent ID: 6446537
Filing Date: 2002-09-10
Classification: B60T

Abstract:
A vacuum brake booster for a vehicle comprising:a housing in which is disposed at least one pressure chamber; a movable wall disposed in the housing for movement in forward and rearward directions of the vehicle and dividing the pressure chamber into a front chamber to be connected to a vacuum pressure source and a rear chamber selectively connected to the front chamber and atmospheric pressure; a power piston connected to the movable wall; an input member disposed in the power piston for movement in the forward and rearward directions of the vehicle through operation of an operation member; a valve mechanism having a vacuum valve connecting the rear chamber with the front chamber in response to movement of the input member and an atmospheric pressure valve connecting the rear chamber to the atmospheric pressure in response to movement of the input member; an output member outputting a forward movement force of the power piston by moving forwardly with forward movement of the power piston in response to the forward movement of the movable wall; an auxiliary movable wall disposed in the front chamber and movable in the forward and rearward directions, the output member being adapted to be engaged by the auxiliary movable wall to move in response to movement of the auxiliary movable wall; a partition member disposed in the front chamber and defining together with the auxiliary movable wall an auxiliary chamber in the front chamber, the rear chamber and the auxiliary chamber being connectable with each other; a communication passage fluidly connecting the rear chamber and the auxiliary chamber; and first valve means for permitting and preventing fluid communication between the rear chamber and the auxiliary chamber via the communication passage, wherein the first valve means is actuated in response to a vehicle condition to establish communication between the auxiliary chamber and the rear chamber.