Patent ID: 9132818
Filing Date: 2015-09-15
Classification: B60T

Abstract:
1. A fluid pressure booster for a braking device, comprising: a control piston on which an input brake operation acts in an advancing direction, and a reaction force based on a fluid pressure generated by a booster fluid pressure generation chamber for actuating a master piston of a master cylinder acts in a retracting direction; a pressure increasing valve which includes a cylindrical valve seat member which is provided, at a front end thereof, with a valve seat facing a valve chamber communicating with a fluid pressure generation source, a valve body that is urged by a spring toward a side where the valve body is seated on the valve seat and is housed in the valve chamber, and a pressing rod that is coaxially inserted in the valve seat member and pushes the valve body with the front end so that the valve body is separated from the valve seat, and which opens according to the advance of the control piston, and is provided between the valve chamber and the booster fluid pressure generation chamber; and a pressure reducing valve provided between a release chamber communicating with a reservoir and the booster fluid pressure generation chamber, the pressure reducing valve closes when the control piston advances and opens when the control piston retracts, wherein a plurality of contraction portions are formed in series in a flow direction from the valve chamber to the booster fluid pressure generation chamber between an outer periphery of a front portion of the pressing rod and an inner periphery of a front portion of the valve seat member in a flow passage through which a working fluid flows such that a distance between the outer periphery and the inner periphery is reduced at each contraction portion.