Patent ID: 6883415
Filing Date: 2005-04-26
Classification: B60T

Abstract:
1. A brake booster device comprising: a booster shell; a partition member dividing the interior of said booster shell into a variable pressure chamber and a constant pressure chamber; an output member passing through a front wall of said booster shell airtightly; a piston provided bodily with said partition member for transmitting the movement in a front-rear direction of said partition member responsive to the pressure difference between said variable pressure chamber and said constant pressure chamber, to said output member; a control valve body provided to face a rear surface of said piston and to be movable relative thereto through a predetermined amount in said front-rear direction for being restricted from further moving rearwardly upon abutment with a rear wall of said booster shell; a seal member interposed between said rear wall of said booster shell and said control valve body for maintaining said variable pressure chamber in airtight state; a valve hole formed in said piston and communicating with a front surface thereof exposed to said constant pressure chamber and a rear surface thereof facing said control valve body; a negative pressure valve portion provided at the rear surface of said piston to encircle said valve hole; a negative pressure valve operating portion provided on said control valve body for being brought into abutment with said negative pressure valve portion when said control valve body is advanced relative to said piston; an air valve member received in a cave formed at the rear end portion of said piston to be movable in said front-rear direction and having an air valve portion formed at a rear surface of said air valve member in the form of a closed loop; an air valve operating portion provided on said control valve body for selectively opening and closing said air valve portion; a resilient member for rearwardly urging said air valve member towards said air valve operating portion; a passage provided for admitting the atmospheric pressure into said variable pressure chamber when said air valve member is forwardly moved to separate said air valve portion from said air valve operating portion; an input rod coupled to a brake pedal and passing through said rear wall of said booster shell and a through hole formed in said control valve body to be also coupled to said air valve member; a cylindrical portion provided on said control valve body and rearwardly protruding through a through hole of the rear wall of said booster shell to surround said input rod; and wherein said seal member is composed of a cylindrical flexible member which is secured at one end thereof to a rear end of said cylindrical member and at the other end thereof to the rear wall of said booster shell while surrounding said through hole.