Patent ID: 6334383
Filing Date: 2002-01-01
Classification: B60T

Abstract:
A vacuum servo apparatus comprising:a housing having at least one pressure chamber formed therein; a movable wall disposed in said housing to be movable forward and backward with respect to said housing and partitioning said pressure chamber into a front chamber communicating with a negative pressure source and a rear chamber selectively communicated with said front chamber and the atmosphere; a power piston joined to said movable wall; an input member arranged in said power piston to be movable forward and backward with respect to said power piston, said input member including a front member and a rear member separated by a clearance and movable with respect to one another to cancel said clearance; an atmospheric valve seat arranged in said power piston to be movable forward and backward integrally with said rear member of said input member; a vacuum valve seat arranged in said power piston; a control valve including: an atmospheric seal portion adapted to move into and out of abutment against said atmospheric valve seat for cutting off communication of said rear chamber with the atmosphere when the atmospheric seal portion comes into abutment against said atmospheric valve seat and for establishing communication of said rear chamber with the atmosphere when the atmospheric seal portion moves out of abutment against said atmospheric valve seat; and a vacuum seal portion adapted to move into and out of abutment against said vacuum valve seat for cutting off communication between said front chamber and said rear chamber when the vacuum seal portion comes into abutment against said vacuum valve seat and for establishing communication of said rear chamber with said front chamber when the vacuum seal portion moves out of abutment against said vacuum valve seat; an output member for outputting to outside the apparatus a forward force of said power piston in accordance with a movement of said movable wall; and an actuator for moving said atmospheric valve seat and said atmospheric seal portion away from each other to establish communication between said rear chamber and the atmosphere, wherein a predetermined input force applied to said input member during inactivation of said actuator produces an output force from said output member that increases to a predetermined output force, and an output force generated during activation of said actuator is controlled to be smaller than said predetermined output force.