Patent ID: 8305048

Claim:
A vehicle power generating device comprising: an alternator which has a voltage regulator that keeps the voltage of generated power constant, the alternator having an excitation winding that becomes excited when energized, the alternator generates power by rotation of the excited winding; and an electronic control unit that controls the voltage regulator, wherein the alternator has an abnormally high temperature determining portion that determines whether the temperature of the alternator is abnormally high, and an abnormal signal outputting portion which, when it has been determined by the abnormally high temperature determining portion that the temperature of the alternator is abnormally high, outputs a signal indicative of the determination that the temperature is abnormally high to the electronic control unit; and when the electronic control unit receives the signal indicative of the determination that the temperature is abnormally high, the electronic control unit calculates a target voltage to be generated by the alternator based on information relating to a state of the vehicle, the target voltage being a minimum voltage with which an on-board electrical load can be properly operated and the target voltage is lower than a normal voltage which is calculated when an abnormally high temperature is not determined; and wherein when the electronic control unit receives the signal indicative of the determination that the temperature is abnormally high, the electronic control unit controls the voltage regulator according to the target voltage such that the alternator generates the minimum voltage with which the on-board electrical load can be properly operated and the electronic control unit controls the voltage regulator to suppress a maximum value of the excitation current that is allowed to flow through the alternator to a value that is lower than a normal maximum value when the abnormally high temperature is not determined.