Patent attributes
A driving force switching control apparatus in a vehicle which runs by two-wheel drive or four-wheel drive in accordance with the running state. The apparatus includes a device for determining whether the vehicle runs at a constant speed; and a device for determining a drive system of the vehicle running at a constant speed to be the two-wheel drive or the four-wheel drive according to road surface conditions computed using rolling resistance. A threshold value for switching between the two-wheel drive and the four-wheel drive is changed in a manner such that a determination area where the four-wheel drive is selected increases according to increase in the rolling resistance. Sufficient driving force transmitted to the wheels can be secured even when the road surface condition varies, and accordingly, sufficient driving force is secured also when the running condition is changed from constant speed running to acceleration or deceleration running.
