Patent ID: 7309112

Claim:
A braking system comprising: a brake operating member manually operable by an operator of the braking system; a master cylinder operable upon an operation of said brake operating member and including a housing, and at least two pressurizing pistons which are fluid-tightly and slidably fitted in said housing and which cooperate with said housing to define at least two pressurizing chambers which are isolated from each other, and wherein a working fluid in each of said at least two pressurizing chambers is pressurized by an advancing movement of a corresponding one of said at least two pressurizing pistons; a hydraulically operable brake cylinder for activating a brake; and a valve device having a first state in which the pressurized fluid is delivered from two pressurizing chambers of said at least two pressurizing chambers to said brake cylinder, and a second state in which the pressurized fluid is delivered from only one of said two pressurizing chambers to said brake cylinder, wherein: the braking system is structured such that when the at least two pressurizing pistons move relative to the housing while the valve device is in the second state, the fluid is permitted to be discharged from the only one of said two pressurizing chambers and delivered to the brake cylinder, but none of the fluid permitted to be discharged from the other of the two pressurizing chambers is permitted to be delivered to said brake cylinder, the braking system is structured to have the first state and the second state in a normal braking operation in which the pressure of the pressurized fluid in the brake cylinder changes with an amount of operation of the brake operating member, and said valve device is placed in said first state while the pressure of the pressurized fluid in said other of said two pressurizing chambers is not higher than a first predetermined value, and is placed in said second state while the pressure of the pressurized fluid in said other pressurizing chamber is higher than said first predetermined value.