PURPOSE: To provide a detector which detects rotation speed of each wheel, a wheel speed calculating means, an acceleration calculating means, and a means which judges that wheels grip the surface of road when acceleration is within a specified scope and continues for more than the predetermined period of time so as to obtain accurate car body speed.
CONSTITUTION: Rotation speed of each wheel, namely wheel speed VS, is calculated from each wheel speed detector, and acceleration a per corresponding wheel is obtained from time variation of each wheel speed VS. Next, it is compared that wheel acceleration a is between the maximum acceleration aMAX and the maximum deceleration aMIN to judge whether the wheels grip or slide. When it is judged that the wheels grip, 1 (one) which means the time of one cycle until the next car body speed calculation is added to a wheel timer T which examines the time when the wheel acceleration a exists within the maximum acceleration aMAX and the maximum deceleration aMIN. When the wheel timer T exceeds the specified time TMAX, for example, the value of B which is obtained by conversion of aMAX is added to the preceding car body speed Vn-1 to obtain the present car body speed Vn.
OKUMOTO NOBUAKI
TAKASU EIJI
Next Patent: BRAKE DEVICE WITH ANTILOCK MEANS