Patent ID: 6311606
Filing Date: 2001-11-06
Classification: B60T

Abstract:
A vacuum servo unit for vehicle brake systems comprising:a housing in which is defined at least one pressure space;a movable wall provided in the housing for movement in an axial direction, the movable wall dividing the pressure space into first and second chambers;a power piston coupled to the movable wall;an axially movable input member located in the power piston and connectable to a brake operation member to be moved upon application of an input force to the brake operation member, the input member including a front portion having an engaging portion and a rear portion positioned at a rear side of the front portion, the front portion being movable back and forth relative to the rear portion;a valve mechanism located in the power piston and connected to the input member to control pressure within one of said first and second chambers to cause said movable wall to move and thereby apply an advancing force to the power piston, the valve mechanism including an atmospheric pressure valve seat and an atmospheric pressure seal portion that are adapted to engage one another, the atmospheric pressure valve seat being operatively connected to the input member to operate the valve mechanism by the input member;an output member outputting the advancing force applied to the power piston outside the housing;a deformable reaction member transmitting the advancing force of the power piston and the input force applied to the input member to the output member, the reaction member providing a reaction force to retract the input member;an actuator connected to the valve mechanism to operate the valve mechanism upon operation of the actuator in a manner causing application of the advancing force to the power piston;a compressible member located between the front portion of the input member and the movable member of the actuator to be axially compressed during operation of the actuator; andthe engaging portion of the input member directly engaging the reaction member, an axial distance between the engaging portion of the input member and the atmospheric pressure valve seat during operation of the actuator continuously varying in response to continuous changing of a driving force applied to the movable member upon activating the actuator.