A driving force control system for a four-wheel drive vehicle[is disclosed]
which enables the vehicle to smoothly start on a low-.mu. road surface,
and is capable to distributing just required amounts or driving forces to
auxiliary drive wheels depending on an actual accelerating condition of
the vehicle, thereby improving the response and fuel economy of the
vehicle. The four-wheel drive vehicle includes front wheels as main drive
wheels, and rear wheels as auxiliary drive wheels. The driving force
control system controls engagement forces of electromagnetic clutches to
thereby control the driving forces (torques) distributed to the rear
wheels. The 2/4WD.multidot.ECU of the driving force control system
calculates a filtered vehicle acceleration XGF1F of the vehicle 2 based on
a drive torque TD, and then calculates a basic VATC torque value VATC
based on the calculated filtered vehicle acceleration XGF1F, for use in
calculation of the final desired VATC torque value TOBJM of torque to be
distributed to the rear wheels.