Master cylinder and electronic brake system comprising same

An electronic brake system comprising:

• a master cylinder comprising a cylinder block having a bore of a multi-stage form in a longitudinal direction therein, a first master chamber and a second master chamber sequentially arranged in series in the bore, a first master piston provided to move in connection with an operation of a brake pedal and to pressurize the first master chamber, a second master piston provided to be displaceable by a displacement of the first master piston or a hydraulic pressure in the first master chamber and to pressurize the second master chamber, and a pedal simulator interposed between the first master piston and the second master piston to provide a reaction force to the brake pedal;
• a hydraulic control unit comprising a first hydraulic circuit provided to receive and control a hydraulic pressure to be transferred to two wheel cylinders and a second hydraulic circuit provided to control the hydraulic pressure to be transferred to the other two wheel cylinders;
• a first backup flow path provided to connect the first master chamber and the first hydraulic circuit;
• and
• a second backup flow path provided to connect the second master chamber and the second hydraulic circuit,
• wherein a cross-sectional area of the first master piston is provided to be relatively larger than a cross-sectional area of the second master piston.