Method of controlling driving force

A driving force control device for a four-wheel drive vehicle, comprising:

• a wheel speed sensor configured to acquire a speed of a wheel;
• a lateral acceleration sensor configured to acquire a lateral acceleration of the vehicle;
• a road surface condition detector configured to acquire information on a road surface condition;
• and
• a control unit including a processor configured to acquire a driving force of an engine after passing through a transmission, a road surface friction coefficient calculated based on the speed of the wheel and the driving force, and a ground contact load of the wheel when the vehicle is traveling, the ground contact load calculated based on a ground contact load of the wheel when the vehicle is stopped and the lateral acceleration,
• wherein the control unit corrects the ground contact load of the wheel when the vehicle is traveling by applying thereto a load change rate set according to a roughness of a road surface estimated based on the information on the road surface condition, and
• wherein when a friction circle defined by a product of the corrected ground contact load and the road surface friction coefficient is compared to a total force of the driving force of the wheel and a lateral force caused by a lateral acceleration in cornering to find that the total force is close to the friction circle, the driving force of the wheel is reduced to prevent a slip from occurring.