Negative pressure brake booster

摘要

A negative pressure brake booster includes a tubular member (18) slidably fitted into a valve body, and formed with a vacuum valve seat (21), the tubular member (18), a valve plunger (16) and the valve body (3) being maintained in their inoperative positions by abutment against a key member (13); a holder (14) is formed with a tapered surface (14a) to assist in allowing an elastic deformation of a reaction disc (15), whereby, immediately after the commencement of operation of a valve mechanism (7) as an input shaft (8) is driven forward, the input shaft (8) and the tubular member (18) are maintained in their inoperative positions until a rear end face of a variable pressure passage (28) abuts against the key member (13); the operating stroke of an input shaft (6) can be chosen to be less than the operating stroke of an output shaft (11) while preventing the jumping value from increasing to an excessively high value. <IMAGE>