Drive force distribution device and method for distributing drive force

A drive force distribution device of a vehicle including a main drive wheel, a sub drive wheel, and a drive force transmission system that transmits a drive force generated by a drive source to the drive wheels, the device comprising:

• a coupling arranged in the drive force transmission system, wherein the coupling changes a torque transmission rate of a torque transmitted from an input of the coupling to an output of the coupling, thereby varying a drive force distribution ratio of the main drive wheel to the sub drive wheel;
• a control section that controls operation of the coupling, the control section estimating the temperature of at least one of heat generating portions of the drive force transmission system by accumulating a heat generating energy accumulated in the heat generating portion in correspondence with the load acting on the heat generating portion, wherein, if the estimated temperature exceeds a predetermined temperature, the control section controls the operation of the coupling to reduce the load acting on the heat generating portion, thereby suppressing overheating of the heat generating portion;
• a memory portion that memorizes the estimated temperature as a memorized temperature before the drive source is stopped;
• and
• a timer portion that, upon re-start of the drive source after the drive source is stopped, measures the time since the stopping of the drive source,
• wherein the control section controls the operation of the coupling in correspondence with the measured time and the memorized temperature immediately after the drive source is re-started.