Master cylinder

A master cylinder including:

• a housing with a bore therein, said bore having a first outlet port connected to wheel brakes in a first brake circuit, a second outlet port connected to wheel brakes in a second brake circuit, and an inlet port connected to a source of operational hydraulic fluid;
• piston means located in said bore for defining a first chamber that is connected to said first outlet port and a second chamber that is connected to said second outlet port;
• first valve means carried by said piston means and connected to control communication of operational hydraulic fluid available at said inlet port;
• an input member connected to a pedal and to said first valve means, said input member being axially moved by an input force applied to said pedal to operate said first valve means and utilize said operational hydraulic fluid in the development of pressurized fluid that is communicated to said wheel brakes in said first brake circuit and said wheel brakes in said second circuit to effect a first brake application, said piston means being characterized by:
• a first surface area and a smaller second surface area that are combined to define a first effective area while said second surface area defines a second effective area that are located in said first chamber, said first valve means on being moved by said input member allowing operational pressurized fluid to be communicated to said first chamber, said pressurized fluid being directly communicated to said wheel brakes in said first brake circuit to initiate a brake application and acting on said first effective area to move said piston means toward said second chamber to pressurize fluid therein that is communicated to said wheel brakes in said second circuit to effect a first brake application and wherein in an absence of the presence of said operational hydraulic fluid in said first chamber a manual input force moves said second effective area into said second chamber to pressurize fluid therein to develop a second pressurize fluid that is communicated to said wheel brakes in said second brake circuit to effect a second brake application.