Patent ID: 6192783
Filing Date: 2001-02-27
Classification: B60T

Abstract:
A brake booster including a valve body slidably disposed in a shell, a valve plunger slidably fitted into the valve body and mechanically coupled to an input shaft for movement therewith, a first plunger plate slidably fitted into a front tubular portion of the valve plunger, a first spring for urging the first plunger plate forward relative to the valve plunger, and a reaction disc interposed between one end of an output shaft and an end face of the valve body for transmitting a reaction which is acting upon an output shaft through the first plunger plate and the first spring to the valve plunger and the input shaft;characterized by an annular, second plunger plate slidably fitted around an outer periphery of the first plunger plate toward its front end, and a second spring having a greater spring constant than the first spring and disposed between the second plunger plate and the valve plunger,a front end face of the second plunger plate being disposed rearward of a front end face of the first plunger plate in an inoperative condition of the brake booster, the arrangement being such that as the brake booster is actuated, in a region of a reduced depression of a brake pedal, the reaction disc is brought into abutment against the front end face of the first plunger plate so that a reaction which is acting upon the output shaft is transmitted through the first plunger plate and the first spring to the valve plunger while in a region of a greater depression of the brake pedal, the reaction disc is brought into abutment against the front end faces of the both plunger plates so that a reaction which is acting upon the output shaft is transmitted through the first spring and the second spring to the valve plunger.