Patent ID: 7472968
Filing Date: 2009-01-06
Classification: B60T

Abstract:
1. A vacuum type brake booster comprising: a housing for defining at least one pressure chamber therein; a movable wall disposed in the housing to divide the pressure chamber into a vacuum chamber and a variable pressure chamber; a valve body secured to the movable wall and having an axial hole; an input member disposed in the axial hole to be axially movable in relation to the valve body; a valve mechanism disposed in the axial hole and including a vacuum valve which provides a connection between the vacuum chamber and the variable pressure chamber and cut off the connection in response to axial movement of the input member in relation to the valve body, and an atmospheric valve which provides a connection between the variable pressure chamber and the atmosphere and cut off the connection in response to axial movement of the input member in relation to the valve body; a reaction member having a rear surface with which a front end portion of the input member can come into engagement at a first portion of the rear surface, the first portion being capable of deforming and bulging toward the rear; and an output member axially movable in relation to the valve body and engaged, at its rear end portion, with a front surface of the reaction member, wherein when the input member advances in relation to the valve body, the vacuum valve closes and cut off the connection between the vacuum chamber and the variable pressure chamber, and the atmospheric valve opens and provides the connection between the variable pressure chamber and the atmosphere, whereby an output corresponding to the differential pressure between the vacuum chamber and the variable pressure chamber is produced at the output member, and the reaction of the output is transmitted from the output member to the front surface of the reaction member, and then transmitted from the rear surface of the reaction member to the valve body and the input member, and wherein the valve mechanism includes an atmospheric valve seat which advances and retreats together with the input member, a vacuum valve seat assembled to the valve body to advance and retreat, and a valve member having an atmospheric valve portion which forms the atmospheric valve in cooperation with the atmospheric valve seat and a vacuum valve portion which forms the vacuum valve in cooperation with the vacuum valve seat; and the reaction member has a second portion on the rear surface, the second portion deforming and bulging rearward in the same manner as the first portion when an output is produced at the output member, and the rearward bulging deformation of the second portion is transmitted to the vacuum valve seat via a transmission member assembled to the valve body to be axially movable.