Traction control system for motor vehicles

Claim 1

A traction control system for motor vehicles, wherein a slip of a driving wheel which tends to occur when the motor vehicle starts or accelerates, is detected; and a braking force imparted to said driving wheel is controlled on the basis of said detection, thereby restraining the slip of said driving wheel, said traction control system comprising: (a) Wheel speed detecting means for detecting left-hand and right-hand driving wheel speeds; (b) Threshold value setting-up means for setting up a plurality of predetermined threshold values in relation to the vehicle speed, said threshold value being higher than said vehicle speed and being determined by adding a predetermined value to the higher one of left-hand and right-hand non-driving wheel speeds; and a computed vehicle speed is determined from the higher one of the left-hand and right-hand non-driving wheels; and (c) means for effecting buildup or reduction of the brake fluid pressure on the basis of a comparison of the speed of said driving wheel as acceleration or deceleration and said plurality of predetermined threshold values, and for causing a holding mode in which the brake fluid pressure is held to occur at a time point when the driving wheel speed changes from increase to decrease; and (d) means for switching said holding mode to a buildup mode in which the brake fluid pressure is increased when the brake fluid pressure holding mode has continued for or longer than a predetermined time period while said driving wheel speed is higher than a specific one of said plurality of threshold values such that excessive reduction of brake fluid pressure is prevented thus preventing vibration from occurring in said vehicle during traction control.