Patent ID: 6516704
Filing Date: 2003-02-11
Classification: B60T

Abstract:
A brake booster including a valve body slidably disposed within a shell, a power piston mounted on the valve body, a constant pressure chamber defined forwardly of the power piston within the shell, a variable pressure chamber defined rearwardly of the power piston within the shell, and a valve mechanism for controlling a switching of supply/discharge of a fluid to and from the variable pressure chamber, the valve mechanism including a vacuum valve seat formed on the valve body, a tubular member disposed to be axially movable within the valve body and having an atmosphere valve seat formed toward the rear end thereof, a valve element having a first seat which is adapted to be seated upon the vacuum valve seat and a second seat adapted to be seated upon the atmosphere valve seat, and a valve plunger mechanically coupled to an input shaft and disposed to be axially movable relative to the valve body and adapted to be driven forward together with the tubular member as at least the input shaft is driven forward;the brake booster comprising engaging means for connecting the tubular member and the valve body together when the input shaft is driven forward through a given stroke relative to the valve body to maintain the second seat of the valve element removed from the atmosphere valve seat during the time the input shaft is being driven forward, the engaging means terminating the connection between the tubular member and the valve body as the input shaft retracts to its inoperative position.