Dual-circuit hydraulic anti-lock braking system

A dual-circuit hydraulic anti-lock braking system for an automotive vehicle having a first wheel group including at least one wheel and a second wheel group including at least one wheel different from the at least one wheel of the first wheel group, comprising:

• a dual-circuit hydraulic braking device including a first and a second brake circuit which are hydraulically independent of each other,
• said first brake circuit comprising (a) a first brake-cylinder group including at least one brake cylinder for applying brake to a corresponding wheel of said first wheel group, (b) a first pressure source for producing a first braking pressure, and (c) a first fluid-passage group including at least one fluid passage for transmitting said first braking pressure from said first pressure source to a corresponding brake cylinder of said first brake-cylinder group,
• said second brake circuit comprising (d) a second brake-cylinder group including at least one brake cylinder for applying brake to a corresponding wheel of said second wheel group, (e) a second pressure source for producing a second braking pressure which is hydraulically independent of said first braking pressure, and (f) a second fluid-passage group including at least one fluid passage for transmitting said second braking pressure from said second pressure source to a corresponding brake cylinder of said second brake-cylinder group;
• wheel rotating condition detecting means for detecting a rotating condition of at least one wheel of each of said first and second wheel groups;
• vehicle running condition detecting means for detecting a running condition of said automotive vehicle;
• braking pressure regulating means for regulating, when the detected rotating condition of said at least one wheel of each of said first and second wheel groups is brought into a predetermined relationship with the detected running condition of said automotive vehicle, each of said first and second braking pressures to apply the regulated pressure to one of said brake cylinders corresponding to the wheel whose detected rotating condition is brought into said predetermined relationship, said braking pressure regulating means conducting at least one of pressure-increasing and pressure-decreasing operations for a duration of time for regulating said each braking pressure;
• failure detecting means for detecting that each of said first and second hydraulic brake circuits has failed;
• and
• time setting means for determining said duration of time at a first duration value when the failure of any one of the first and second brake circuits is not detected by said failure detecting means, and determining said duration of time at a second duration value different from said first duration value when said failure is detected.