Negative-pressure type booster device

A negative-pressure type booster device comprising:

• a hollow housing;
• a movable partition wall formed of an annular plate and an annular diaphragm for partitioning the interior of the housing into a front negative-pressure chamber and a rear variable pressure chamber;
• a cylindrical valve body provided so as to be movable forward and rearward with respect to the housing and provided so as to be movable forward and rearward with respect to the movable partition wall in the housing;
• an air valve provided in a shaft hole formed in the valve body and movable forward and rearward in an axial direction of the shaft hole with respect to the valve body and integrally moves with an input member;
• and
• a valve mechanism provided with a negative-pressure valve for allowing the negative-pressure chamber to communicate with the variable pressure chamber and blocking the communication in accordance with the forward and rearward movement of the air valve with respect to the valve body and an atmospheric valve for allowing the variable pressure chamber to communicate with atmospheric air and blocking the communication,
• wherein the valve body is provided with a flange part extending in a radially outward direction from a front part of the valve body, and
• the annular plate is movable the movement of in an axially rearward direction relative to the valve body in the input member operation state, and is provided with a locking part which comes into contact with the flange part so as to restrict movement in an axially forward direction relative to the valve body in the input member operation state.