Patent ID: 8885304

Claim:
A drive force distribution control apparatus comprising: a battery that supplies power that is generated by a power generator rotated by a drive force generated by an engine; an ignition switch that selectively allows and interrupts a supply of the power from the battery; a relay that selectively allows the power supplied from the battery to be transmitted to a drive system and interrupts transmission of the power supplied from the battery to the drive system; relay-output-voltage detecting means for detecting a relay output voltage that is a voltage on an output side of the relay; and abnormality-determining means for determining whether there is an abnormality of the relay, based on the relay output voltage detected by the relay-output-voltage detecting means; and drive-mode-switching means for switching a drive mode between a four-wheel-drive mode and a two-wheel-drive mode, wherein when the relay output voltage detected by the relay-output-voltage detecting means is equal to or lower than a predetermined voltage threshold, the abnormality-determining means repeatedly and successively turns the relay on and off multiple times, and wherein the abnormality-determining means determines whether a speed of the engine is equal to or higher than a predetermined engine speed threshold and the ignition switch is on, and if the speed of the engine is equal to or higher than the predetermined engine speed threshold and the ignition switch is on and the relay output voltage detected by the relay-output-voltage detecting means is still equal to or lower than the predetermined voltage threshold, the abnormality-determining means determines that there is an abnormality that keeps the relay stuck open, and then switches, using the drive-mode-switching means, the drive mode from the four-wheel-drive mode to the two-wheel-drive mode.