Patent ID: 6739676
Filing Date: 2004-05-25
Classification: B60T

Abstract:
A braking system for braking a wheel of an automotive vehicle, comprising:a brake operating member; a master cylinder functioning as a first hydraulic pressure source for generating a hydraulic pressure based on an input force; a vacuum booster having a negative-pressure chamber connected to a negative pressure source, and a variable-pressure chamber selectively connected to said negative-pressure chamber and an atmosphere, said vacuum booster boosting an operating force of said brake operating member on the basis of a difference between pressures in said negative-pressure and variable-pressure chambers, and transmitting the boosted operating force to said master cylinder, said vacuum booster having a transition point at which a boosting ratio of said vacuum booster is reduced during an increase of said brake operating force before a boosting limit point at which said vacuum booster has become inoperable to perform its boosting function is reached, said transition point being kept unchanged irrespective of a change in the pressure in said negative-pressure chamber and being reached at a predetermined value of said brake operating force while said vacuum booster is operating in a normal state; a brake including a wheel brake cylinder which is connected to said master cylinder through a fluid passage and which is activated by a hydraulic pressure supplied thereto through said fluid passage, for braking said wheel; and a pressure increasing device including a second hydraulic pressure source connected to said fluid passage, said pressure increasing device performing a pressure increasing operation of increasing a hydraulic pressure in said wheel brake cylinder, by using said second hydraulic pressure source, such that the increased hydraulic pressure in said wheel brake cylinder is higher than that generated by said master cylinder, said pressure increasing device initiating said pressure increasing operation when said brake operating force has increased to said transition point.