Patent ID: 7201455

Claim:
A hydraulic brake system for a road vehicle, comprising: a master brake cylinder configured to generate a master cylinder pressure as a function of a braking intent of a driver of the road vehicle; a hydraulic unit connected between the master brake cylinder and at least one wheel brake cylinder of at least one wheel, the hydraulic unit having ,a system of actuatable valves, an accumulator chamber, and at least one hydraulic pump; and a differential pressure valve situated between the master brake cylinder and the hydraulic unit; wherein: in a first phase, as a function of the master cylinder pressure, a proportional pressure buildup takes place in at least one of the hydraulic unit and the at least one wheel brake cylinder until a switching pressure in the master brake cylinder is reached; in a second phase, upon reaching the switching pressure, the differential pressure valve is configured to close to keep constant a pressure in the at least one wheel brake cylinder while the master cylinder pressure increases; in a third phase, upon reaching a first predetermined pressure difference between the master cylinder pressure and the pressure in the at least one wheel brake cylinder, the differential pressure valve is configured to cause the pressure in the at least one wheel brake cylinder to increase, at least the first predetermined pressure difference remaining during the increase of the pressure in the at least one wheel brake cylinder in the third phase; in a fourth phase, in response to a further increase in the master cylinder pressure, a limited quantity of brake fluid is introduced from the master brake cylinder into the accumulator chamber as a function of one of reaching of a vehicle-specific slip, reaching of acceleration values of a wheel speed, and a start of a braking operation, the limited quantity of brake fluid being introduced prior to a fifth phase; in the fifth phase, the at least one hydraulic pump is controlled to use the limited quantity of brake fluid to produce a pressure increase in the at least one of the hydraulic unit and the at least one wheel brake cylinder; and in a sixth phase, upon reaching a predetermined second pressure difference between the master cylinder pressure and the pressure in the at least one wheel brake cylinder, the pressure in the at least one wheel brake cylinder is increased super-proportionally with respect to the master cylinder pressure.