Vehicle braking system having devices for controlling fluid flows between pressurizing and assisting chambers of master cylinder and pressure source and reservoir

A braking system for a vehicle having a wheel, comprising:

• a master cylinder including a cylinder housing, and a pressurizing piston which is fluid-tightly and slidably received in said cylinder housing and which cooperates with said cylinder housing to define a pressurizing chamber in front of said pressurizing piston, a working fluid in said pressurizing chamber being pressurized by an advancing movement of said pressurizing piston;
• a brake for braking said wheel;
• a wheel brake cylinder connected to said pressurizing chamber of said master cylinder, and operable with the pressurized fluid supplied from said pressurizing chamber, for activating said brake;
• a brake operating device including a brake operating member manually operable with a brake operating force to apply a first pressurizing force based on said brake operating force to said pressurizing piston;
• an electrically operated hydraulic pressure source operable to pressurize the working fluid and control a pressure of the pressurized fluid;
• an assisting device operable to apply a second pressurizing force based on the pressurized fluid supplied from said electrically operated hydraulic pressure source, to said pressurizing piston;
• and
• a pressurized-fluid supplying device for supplying the fluid pressurized by said electrically operated hydraulic pressure source to at least one of said pressurizing chamber and said wheel brake cylinder.