Brake system for vehicle

A brake system for a vehicle, comprising:

• a hydraulic pressure generating device which outputs a hydraulic pressure corresponding to a braking operation by a vehicle driver;
• hydraulic pressure operated wheel brakes mounted on wheels so as to be operated based on the hydraulic pressure output from the hydraulic pressure generating device;
• electrically operated parking brake drive device which generates an operating force for operating one of
• said wheel brakes, and
• dedicated parking brakes mounted on wheels separately from the wheel brakes,
• in response to energization of the electrically operated parking brake drive device, and which can be maintained in an operated state even upon cancellation of the energization while in the operated state;
• a controller for controlling the energization of the electrically operated parking brake drive device;
• a braking force related amount detector for detecting a physical quantity related to a braking force exhibited by each of the hydraulic pressure operated wheel brakes;
• and
• normally-open solenoid valves interposed between the hydraulic pressure generating device and the hydraulic pressure operated wheel brakes;
• wherein
• the controller staffs the energization of the electrically operated parking brake drive device when the physical quantity detected by the braking force related amount detector exceeds a reference value in a stopped state of the vehicle;
• the controller closes the solenoid valves when the physical quantity detected by the braking force related amount detector has decreased by an amount which exceeds a predetermined value, the predetermined value comprising a value by which a brake-operating force can be determined to be cancelled within a time period extending from the staff of the operation of the electrically operated parking brake drive device until the operational amount of the electrically operated parking brake drive device reaches a target operational amount;
• and
• the controller determines that the electrically operated parking brake drive device has broken down when the operational amount of the electrically operated parking brake drive device does not reach the target operational amount although a predetermined time has elapsed after the staff of the operation of the electrically operated parking brake drive device, and when a breakdown has been determined, the controller carries out a process associated with the breakdown.