Patent ID: 6212993
Filing Date: 2001-04-10
Classification: B60T

Abstract:
A vacuum brake booster for a hydraulic vehicle braking system, having a two-part housing which comprises two outer housing walls opposite each other and at least one movable wall which divides an inner space of the housing into a vacuum chamber and a working chamber, and a control valve which is actuated by means of a bar-shaped input member, a control valve housing for the control valve is connected with the movable wall for a common relative movement with respect to the brake booster housing for the optional connection of the working chamber to at least atmospheric pressure, with a sensing piston being arranged in the control valve, which piston is axially displaceable along a main axis (A) by means of the input member and is received in a guide sleeve secured in the control valve housing and firmly connected with a stop bar which extends transversely to the main axis (A) and protrudes from the guide sleeve through a slot provided therein radially outwardly into a vent duct of the control valve housing, which connects the working chamber to at least atmospheric pressure when a first valve seat of the control valve, which is formed at the sensing piston, is open, characterised in that edges of the slot provided in the guide sleeve form stops for an axial displacement of the stop bar in such a manner that the axial extension of the slot defines the maximum possible stroke of the sensing piston and in that the vent duct has an axial extension in the entire area where the stop bar protrudes into said duct which is considerably larger than the axial extension of the slot so that the flow rate in the mentioned area is reduced.