Valve mechanism for brake booster

摘要

A valve mechanism for a brake booster includes a valve element and a valve seat, either of which includes a first seat through which an orifice passage is formed and a second seat. Under an intermediate load condition when a forward movement of an input shaft ceases, the first seats become engaged with each other and the orifice passage is effective to maintain a communication therethrough. Subsequently when the valve element and the valve seat are more strongly abutting together, the second seats engage to interrupt the communication.