Electric brake system

1. An electric brake system controlling a hydraulic pressure delivered to a wheel cylinder provided at each of wheels according to a pedal effort of a brake pedal, comprising:

a reservoir configured to store oil;

a master cylinder including first and second hydraulic ports, each of which is connected to two wheels, and configured to generate a hydraulic pressure by the pedal effort of the brake pedal;

a pedal simulator configured to provide a reaction force of the brake pedal by being connected to the master cylinder, and connected to the reservoir;

a simulation valve installed at an oil flow path connecting the pedal simulator to the reservoir, or at an oil flow path connecting the master cylinder to the pedal simulator;

a bypass flow path branching off from the oil flow path and connected to the reservoir;

a relief valve provided at the bypass flow path; and

a simulation check valve configured to enable the oil to flow from the reservoir to the pedal simulator, or from the reservoir to the master cylinder when the pedal effort of the brake pedal is released.

2. The electric brake system of claim 1 , wherein the relief valve is provided in parallel with the simulation valve.

3. The electric brake system of claim 1 , wherein the relief valve is open when a chamber pressure in the master cylinder is equal to or greater than a predetermined pressure.

4. The electric brake system of claim 1 , wherein the simulation check valve is provided at a connection flow path connecting the bypass flow path to the oil flow path.

5. The electric brake system of claim 1 , wherein the simulation valve is configured with a normally closed type solenoid valve that is usually closed and is open when an opening signal is received.

6. The electric brake system of claim 1 , further comprising:

a pedal displacement sensor configured to sense a displacement of the brake pedal;

a pressure source connected to the reservoir and configured to output an electrical signal through the pedal displacement sensor when the brake pedal is operated and generate a hydraulic pressure;

a hydraulic pressure control unit including first and second hydraulic pressure circuits, each of which is connected to the pressure source through a hydraulic flow path and is configured to receive a hydraulic pressure generated from the pressure source and control a flow of the hydraulic pressure that is delivered to each of the wheel cylinders; and

an electronic control unit configured to control the pressure source and valves on the basis of hydraulic pressure information and pedal displacement information.

7. The electric brake system of claim 6 , wherein the hydraulic pressure control unit is provided with a normally open (NO) type valve configured to control the flow of the hydraulic pressure delivered to each of the wheel cylinders, and a normally closed (NC) type valve configured to control a flow of a hydraulic pressure discharged from each of the wheel cylinders.

8. The electric brake system of claim 1 , further comprising:

a first backup flow path configured to connect the first hydraulic port to a first hydraulic pressure circuit, and a second backup flow path configured to connect the second hydraulic port to a second hydraulic pressure circuit so as to directly deliver the oil to each of the wheel cylinders when the electric brake system operates abnormally;

a first cut valve provided at the first backup flow path and configured to control a flow of the oil; and

a second cut valve provided at the second backup flow path and configured to control a flow of the oil.

9. The electric brake system of claim 8 , wherein the first and second cut valves are configured with normally open type solenoid valves that are usually open and are closed when a closing signal is received from an electronic control unit.

10. The electric brake system of claim 1 , wherein the relief valve is configured to enable oil to flow when the simulation valve operates abnormally.