Patent ID: 6843160
Filing Date: 2005-01-18
Classification: B60T

Abstract:
1. A negative pressure brake booster comprising a valve body slidably disposed within a shell, a power piston mounted on the valve body, a constant pressure chamber and a variable pressure chamber defined across the power piston within the shell, a valve mechanism operated by an input shaft for switching a communication between the constant pressure chamber, the variable pressure chamber and the atmosphere, the valve mechanism including a vacuum valve seat formed inside the valve body, a valve plunger slidably fitted into the valve body and connected to the input shaft, an atmosphere valve seat formed on the valve plunger and a valve element adapted to be engaged with or disengaged from the vacuum valve seat and the atmosphere valve seat, a reaction disc disposed between an output shaft and a forwardly facing end face of the valve body for transmitting a brake reaction which acts on the output shaft as the valve mechanism is operated by the input shaft through the valve plunger, a tubular member slidably fitted into the inner periphery of the valve body and having the vacuum valve seat formed thereon, urging means for normally urging the tubular member rearward and holding means for holding the tubular member, the valve plunger and the input shaft in their inoperative state at the commencement of operation of the valve mechanism until the valve body and the output shaft have been driven forward through a given stroke such that an operation stroke of the input shaft is smaller than an operation stroke of the output shaft, thereby creating a space between an end face of a rear portion of the reaction disc and the valve body which assists in allowing an elastic deformation of the reaction disc toward the valve plunger at the commencement of operation of the valve mechanism.