Anti-skid brake system with reset of thresholds due to changing road surface cofficient

An anti-skid brake system for an automotive vehicle, comprising:

• deceleration detecting means for detecting a magnitude of deceleration of a wheel;
• slip value detecting means for detecting a slip value indicating a tendency of locking the wheel;
• braking force controlling means for controlling a braking force by increasing, decreasing and retaining the braking force so as not to lock the wheel at the moment of braking, in response to output from the deceleration detecting means and the slip value detecting means;
• road surface friction coefficient .mu. assuming means for assuming a road surface friction coefficient .mu. on the basis of a predetermined condition;
• threshold value altering means for altering a controlling threshold value for controlling the braking force controlling means on the basis of the road surface friction coefficient .mu. assumed by the road surface friction coefficient .mu. assuming means;
• and
• road surface friction coefficient .mu. altering means for altering the road surface friction coefficient .mu. assumed by the road surface friction coefficient .mu. assuming means;
• wherein the braking force controlling means is arranged to shift from a state in which control for increasing the braking force is performed to a state in which control for retaining the braking force is performed when the magnitude of deceleration of the wheel reaches a value greater than the first predetermined threshold value;
• wherein the threshold value altering means is set to make the first predetermined threshold value smaller as the road surface friction coefficient .mu. becomes smaller;
• and
• wherein the road surface friction coefficient .mu. altering means is set to alter the road surface friction coefficient .mu. assumed by the road surface friction coefficient .mu. assuming means to a value having a higher road surface friction coefficient .mu. when a period of time required from the moment when the control for increasing the braking force starts to the moment when the control for retaining the braking force starts after the control for increasing the braking force is equal to or longer than a predetermined period of time.