Patent ID: 6119577
Filing Date: 2000-09-19
Classification: B60T

Abstract:
A brake booster including a substantially tubular valve body slidably disposed within a shell, a power piston mounted on the valve body, a constant and a variable pressure chamber defined across the power piston, a tubular member slidably mounted on the valve body, an annular vacuum valve seat formed on a rear end of the tubular member, a valve plunger disposed within the valve body in a movable manner and coupled to an input shaft for movement therewith, an annular atmosphere valve seat formed on the valve plunger, a valve element urged in the forward direction by a spring for movement into engagement with or disengagement from the vacuum valve seat and the atmosphere valve seat, a vacuum valve defined by a combination of the vacuum valve seat and a first seat area on the valve element which moves into engagement with or disengagement from the vacuum valve seat, an atmosphere valve defined by a combination of the atmosphere valve seat and a second seat area on the valve element which moves into engagement with or disengagement from the atmosphere valve seat, a constant pressure passage which provides a communication between a space located radially outward of the vacuum valve and the constant pressure chamber, a variable pressure passage which provides a communication between a space located between the vacuum valve and the atmosphere valve and the variable pressure chamber, an atmosphere passage which provides a communication between a space located radially inward of the atmosphere valve with an atmosphere, a drive mechanism for moving the tubular member between an inoperative position and an operative position which are located forwardly and rearwardly of the valve body, and a reaction disc for transmitting a reaction from an output which is produced as the valve body is driven forward to the valve plunger, the arrangement being such that the drive mechanism may move the tubular member in the rearward direction to cause the first seat area to be seated on the vacuum valve seat to close it while causing the second seat area to be removed from the atmosphere valve seat to open the atmosphere valve;characterized in that the operative and the inoperative position of the tubular member are chosen to permit an opening and a closing of the vacuum valve and the atmosphere valve as the valve plunger is driven back and forth in response to a movement of the input shaft.