Patent ID: 6853901

Claim:
A method for control of a four-wheel drive having a control routine controlling the duty of a magnetic clutch according to a difference in the rotational speed of driving and driven axles, the method comprising: determining whether slip of the magnetic clutch is greater than a permissible slip in a case where the magnetic clutch is controlled at a maximum duty; determining whether a first cumulative time corresponding to a period of time that the magnetic clutch is controlled at the maximum duty and that the slip is greater than the permissible slip, is greater than a first reference time; controlling the magnetic clutch at a safety mode duty when the first cumulative time is greater than the first reference time; determining whether a second cumulative time corresponding to a period of time of continuously controlling the magnetic clutch at the safety mode duty, is greater than a second reference time; and controlling the magnetic clutch at a safety mode release duty and returning to the normal control routine when the second cumulative time is greater than the second reference time.