Hydraulic brake device for vehicle

Abstract

A vehicle brake system includes a first fluid chamber whose volume changes corresponding to the amount of advancement and retraction of the input piston, a second fluid chamber into which hydraulic pressure from a hydraulic pressure source is introduced after adjustment in a pressure regulator, a third fluid chamber kept at the atmospheric pressure, a stroke simulator which generates a reaction force to the brake operation corresponding to a change in volume of the first fluid chamber, a master cylinder, a partition member partitioning each of the second and third fluid chambers from the first fluid chamber, first and second seal members disposed in respective fitting gaps, and an annular member having both ends abutting respective seal members. The annular member divides a space into first and second space portions whose volumes respectively increases and decreases by the same amount when the annular member moves in one axial direction.