Patent ID: 6324958
Filing Date: 2001-12-04
Classification: B60T

Abstract:
In an automatic brake booster including a valve body slidably disposed within a shell, a power piston mounted on the valve body, constant and variable pressure chambers defined across the power piston and a valve mechanism disposed within the valve body for switchingly controlling a flow path therein; the valve mechanism comprising a first valve seat formed on the valve body and facing rearward, a sleeve slidably fitted into the valve body and urged rearward by a spring, a second valve seat formed on the sleeve and facing rearward, a valve element urged forward by a poppet return spring to be seated on the first and the second valve seats, drive means for displacing the sleeve forward to switch the flow path, a valve plunger slidably disposed in the sleeve and coupled to an input shaft for driving the sleeve forward as the input shaft is driven forward to switch the flow path, and a seal member interposed between the sleeve and the valve plunger to maintain a hermetic seal therebetween; the valve element comprising a rolling part located at a rear portion thereof and which is folded radially outward to be connected to the valve body, and first and second seat areas disposed forwardly of the rolling part and adapted to be seated on the first and the second valve seats, respectively;comprising the improvement wherein the effective diameter of the rolling part of the valve element and the effective diameter of the seal member are chosen to be equal to each other and the effective diameter of the second valve seat is chosen to be equal to or less than the effective diameter of the seal member.