Voltage regulating system for vehicle including alternator

DETAILED DESCRIPTION The present invention has an object of maintaining good battery condition by detecting accumulated amount of values related to the battery charging ability in a suitable detecting period so as to change the reference voltage of the voltage regulating unit in a controlled rate.
In general, the engine speed change of a vehicle in a town driving because of traffic signal or on-off operation of the motor-driven radiator fan is repeated between some tens of seconds and 30 minutes, and the suitable detecting period (e.
g.
a period between 3 and 30 minutes) prevents frequent fluctuation of the reference voltage.
The present invention has another object of maintaining the battery voltage as high as possible within a level not to cause overcharging of the battery.
In the voltage regulating system for a vehicle alternator according to the present invention, the output voltage of the alternator is regulated by a voltage regulator unit which provides a changeable reference voltage.
The field current is controlled according to a comparison of the battery voltage with the changeable reference voltage.
The reference voltage is changed according to an accumulated amount of values indicating battery charging ability such as battery voltage or battery-charging current sampled in the suitable detecting period.
As a result, the reference voltage is not changed very frequently, so that the alternator-driving torque does not change frequently.
It is noted that frequent change in the battery voltage may be detrimental to vehicle electric loads.
The detecting period is preferably longer than a minimum operation period of a motor-driven radiator fan, so that the battery voltage fluctuation due to intermittent operation of the radiator fan is prevented.
According to the present invention, the reference voltage is lowered when the accumulated amount of values related to the battery charging ability becomes higher than a first level, and is raised when it becomes lower than a second level which is lower than the first level to stabilize the battery voltage