A torque distribution control device for a four-wheel drive vehicle is disclosed,
wherein a torque transmitted from an engine to prime drive wheels is distributed
by an electromagnetic clutch to sub-drive wheels on an on-demand basis. A pre-torque
is determined based on a vehicle speed and a throttle opening degree in a feed-forward
sense. A compensation torque is determined based on the rotational speed difference
between the prime drive wheels and the sub-drive wheels and the vehicle speed in
a feedback sense. The pre-torque and the compensation torque are added for a command
torque, depending on which the electromagnetic clutch is controlled to transmit
the torque from the engine to the sub-drive wheels. At this time, since the command
torque is limited to an upper limit value therefor or below in dependence on the
engine torque, an ECU can be prevented from applying an excess current to an electromagnetic
coil of the electromagnetic clutch and hence, from generating heat to raise its
temperature when the engine torque is small.
