Vehicles generally have an alternator which is a generator driven by an engine to supply power for the electric loads of an engine controller and other electric loads, such as a fuel injection system, lamps, blinkers, blower, wiper, air conditioner and the like. The alternator also is driven by the engine to charge, for example, a 12 volt vehicle battery at the same time.
Among vehicles there are so-called hybrid vehicles provided with an internal combustion engine driven by combustion of fuel, the engine being provided with a motor generator (motor) driven by electric energy and having a power generating function. The hybrid vehicles include an engine and a motor generator (motor) directly connected to the output axle of the engine. The hybrid vehicles further include a motor control means and an engine control means having controllers to control operating states of the engine and the motor, and these control means detect respective operating states of the engine and the motor while the vehicle is driven, and are controlled in association with one another. Such a control system attains a high level of required performance (such as fuel efficiency, lower values of detrimental components in exhaust gases, and improved power performance). A battery supplies driving power to the motor and is charged by power generated by the motor. Since a certain amount of battery charge must be conserved to operate required driving power-generation/driving prevention for the motor, a power-generation controller is provided to control the battery and the generating states of the alternator and the motor.
Some vehicles are of a type having an automatic stop/startup system (idle stop system) wherein the engine is automatically stopped when a predetermined automatic stop condition is satisfied while the engine is at idle. Then the engine is automatically started up when a predetermined automatic startup condition is satisfied while the engine is stopped, so that fuel efficiency and reduction in effluent gas are improved by stopping an engine forcibly when the engine is stopped in an idling state.
Examples of power generating controllers for a vehicle are disclosed in published Japanese Patent Laid-Open No. 9-65504, Japanese Patent Laid-Open No. 9-25864, and Japanese Patent Laid-Open No. 9-84210. A controller is disclosed in Japanese Patent Laid-Open No. 9-65504 for a hybrid vehicle having a motor/generator disposed between an engine and transmission, and a capacitor (condenser battery) connected to the motor/generator. The improved controller, before regenerative braking during deceleration, calculates a voltage between terminals which needs to be fully charged when the vehicle is stopped, and pre-charges the battery to prevent a fully charged state on braking and a lacking charge state during stop. A controller in Japanese Patent Laid-Open No. 9-25864 discloses that when parking the vehicle, main charging means charges a capacitor before stopping of an engine and, after the stop of the engine is detected, charges the capacitor at a rated voltage for a certain time such that the capacitor is close to the fully charged state even if charging of the capacitor is inadequate when the stop operation of the engine is detected. A controller is disclosed in Japanese Patent Laid-Open No. 9-84210 for a hybrid vehicle having a motor/generator disposed between an engine and transmission, and a capacitor (condenser battery) connected to the motor/generator. The motor/generator is assisted by a lower engine load as the charge quantity of the capacitor increases to achieve a suitable charge and a suitable power assist.
However, in a conventional vehicle, the alternator which is a generator driven by the engine, is driven as a part of the engine load, which increases fuel consumption, which is disadvantageous from an economical view point. On the other hand, deceleration energy during deceleration in which fuel is not required, has not been positively utilized and improvement thereof has been desired.