1. Field of the Invention
The present invention relates to a control method and apparatus for an electric generator provided for generating electric power from engine power in a vehicle. The present invention also relates to a vehicle equipped with an apparatus of the type described.
2. Description of the Background Art
Vehicles, such as saddle-type vehicles, including two-wheeled vehicles, are commonly provided with an electric generator, for generating electric power from engine power. The electric generator serves to supply electric power to operate accessories of the vehicle, including a battery, lights, etc. The generator normally generates electric power depending on the speed and rotary power output of the engine. Since the electric generator generates electric power by consuming the rotary power of the engine, if the generated electric power is large, then the ability of the engine to drive a wheel is correspondingly reduced. Specifically, when the throttle valve is fully opened to accelerate the vehicle at a maximum rate, if the electric generator generates a large amount of electric power, then engine power output and peak engine power are reduced correspondingly. The negative effect of the increase in the generated electric power on the engine power output is greater on vehicles carrying engines having smaller power output capabilities.
Heretofore, Japanese laid-Open Patent document No. 2000-253597 disclosed one proposed solution to the above problems, in which an electric generator control apparatus temporarily reduces a battery charging voltage produced by an electric generator upon quick acceleration of the vehicle, thereby lowering the load on the engine during such acceleration.
When the vehicle is driven normally, the proposed electric generator control apparatus of the reference charges the battery at a battery charging voltage of 14.5 V. When the throttle is detected, by various sensors, as being quickly and fully opened, the proposed electric generator control apparatus of the reference charges the battery at a battery charging voltage of 12.0 V, which is lower than when the vehicle is driven normally. Therefore, on the vehicle carrying the proposed electric generator control apparatus, when the throttle is fully open, the power consumption due to the charging of the battery is reduced, resulting in a corresponding increase in the accelerating capability of the engine.
According to the conventional electric generator control apparatus of the reference, however, since the battery charging voltage switches from 14.5 V to 12.0 V when the throttle opening reaches a nearly fully opened value, the vehicle acceleration capability cannot be increased unless the throttle opening is brought to the nearly fully opened value. Consequently, driving conditions capable of accomplishing the benefits of the increased vehicle acceleration capability are limited.
It is therefore an object of the present invention to provide an electric generator control apparatus for gradually reducing an engine load imposed on the engine due to electricity generation, while a throttle valve is in the process of becoming fully open, thereby increasing a vehicle acceleration capability, and also to provide a vehicle carrying such an electric generator control apparatus.