BRAKE SYSTEM

Improving a brake system. In case of failure of an electric system, a pressure increasing mechanism 100 is activated by hydraulic pressure of a master cylinder 62 whereby a servo pressure is supplied to brake cylinders 42FL, 52RR provided for a front left wheel 2 and a rear right wheel 48 while the hydraulic pressure of the master cylinder 62 is supplied to a brake cylinder 42FR provided for a front right wheel 4. Consequently, it is possible to restrain shortage of a braking force and to retrain a yaw moment. In case of presence of possibility of fluid leakage, hydraulic pressure of a power hydraulic pressure source 64 is controlled and supplied to the brake cylinders 52 provided for the rear left and right wheels 46, 48 while the hydraulic pressure of the master cylinder 62 is supplied to the brake cylinders 42 provided for the front left and right wheels 2, 4. Further, the brake cylinders 42FL, 42FR provided for the front left and right wheels 2, 4 are isolated from each other, and are isolated from the brake cylinders 52RL, 52RR provided for the rear left and right and left wheels 46, 48. Thus, three brake lines can be isolated from one another so that even if one of the three brake lines suffers from the fluid leakage, the other brake lines are not influenced by the fluid leakage taking place in the one of the three brake lines.