Patent ID: 8562080

Claim:
A brake system for a vehicle having mounted thereon an engine having a torque control unit that controls a variable valve lift mechanism capable of continuously changing a valve lift amount of an intake valve to generate a target torque, and a negative pressure control unit that controls an electronically controlled throttle to generate a target intake negative pressure, comprising: a booster unit configured to use intake negative pressure of the engine to produce a boosted brake operating force for the vehicle; a first pressure generator unit configured to generate a first brake fluid pressure according to the boosted brake operating force produced by the booster unit; a second pressure generator unit configured to generate a second brake fluid pressure by means of an electric brake fluid pump; a request detection unit configured to detect a degree of a driver-applied-braking-force; a switching unit configured to controllably switch supply of a brake fluid pressure to a wheel cylinder in a manner such that: the supply of the first brake fluid pressure to the wheel cylinder takes place when the degree of the driver-applied-braking-force is less than a driver-applied-braking-force threshold value, and the supply of the second brake fluid pressure switching from the first brake fluid pressure takes place when the degree of the driver-applied-braking-force is greater than or equal to the threshold value; a driver-applied-braking-force threshold value setting unit configured to vary a setting of the driver-applied-braking-force threshold value in real-time, relative to a real-time intake negative pressure of the engine; a first diagnosing unit configured to diagnose whether or not an abnormality occurs in the second brake fluid pressure; and a first fail safe unit configured to fix the valve lift amount of the intake valve in the variable valve lift mechanism to a predetermined value while controlling a torque by the electronically controlled throttle, and to inhibit the supply of the second brake fluid pressure to the wheel cylinder while allowing the supply of the first brake fluid pressure to the wheel cylinder, when the abnormality is diagnosed in the second brake fluid pressure.