Patent ID: 6250200
Filing Date: 2001-06-26
Classification: B60T

Abstract:
A brake booster including a valve body slidably disposed within a shell, a power piston mounted on the valve body, a constant and a variable pressure chamber defined across the power piston, a valve mechanism mounted on the valve body for controlling a switching of a flow path, and a solenoid disposed in the valve body for operating the valve mechanism;wherein the valve mechanism comprises a vacuum valve seat formed on the valve body, a tubular member disposed to be movable in the valve body, an atmosphere valve seat formed on the tubular seat, a valve element adapted to be seated on the vacuum valve seat and the atmosphere valve seat, and a valve plunger disposed to be movable relative to the valve body and the tubular member and driven forward together with the tubular member as an input shaft is driven forward;and wherein the solenoid comprises a housing mounted on the inner periphery of the valve body, a spool contained in the housing and around which a coil is disposed, and a piston disposed to be moveable along the inner periphery of the housing for interlocked movement with the tubular member, the arrangement being such that as the solenoid is energized, the piston and its interlocked tubular member are caused to move forward relative to the valve body and the valve plunger to operate the valve mechanism;characterized in that a tubular guide is formed on a front portion of the piston while an annular guide is formed on a rear portion of the piston in a manner such that both the tubular guide and the annular guide are slidably fitted into the inner periphery of the housing for guiding a movement of the piston within the housing, while an outer periphery of the valve plunger toward its front end is slidably fitted into the inner periphery of the housing and an outer periphery of the valve plunger toward its axial center is slidably fitted into the inner periphery of the housing for guiding a back-and-forth movement of the valve plunger within the housing.