Engine drive system

An engine drive system provided with:

• an engine having an ISC valve that bypasses a throttle valve;
• a magneto AC generator driven by the engine;
• a regulator provided between an output end of the generator and a pair of output terminals to which a load of the generator is connected, the regulator adjusting a voltage and rectifying an AC output of the generator;
• and an electrical control unit in which at least the engine is a control object;
• wherein
• the regulator comprises an open-type regulator configured such that when a voltage between the output terminals is equal to or less than a set value, the regulator rectifies the AC output of the generator and outputs the output through the output terminals, and when the voltage between the output terminals exceeds the set value, the regulator electrically disconnects the output terminals and the output end of the generator, thereby preventing a voltage that exceeds the set value from being applied to the output terminals;
• and wherein
• the electrical control unit includes:
• a valve operation means that operates the ISC valve so that an opening degree of the ISC valve is brought to a given target opening degree;
• a load fluctuation detection means that detects a load fluctuation of the generator occurring while the engine is idling;
• and
• a target opening degree setting means configured so as to give the target opening degree of the ISC valve to the valve operation means so that when the load fluctuation detection means has not detected a load fluctuation, an idle-control target opening degree is given as the target opening degree of the ISC valve to the valve operation means, the idle-control target opening degree being the target opening degree of the ISC valve during feedback control is performed so as to maintain an idle rotational speed at a target value, and when the load fluctuation detection means has detected a load fluctuation, a corrected target opening degree is given as the target opening degree of the ISC valve to the valve operation means for a limited amount of time, after which the target opening degree given to the valve operation means is returned to the idle-control target opening degree, the corrected target opening degree being an idle-control target opening degree that is corrected by a correction amount designated to minimize a fluctuation in the idle rotational speed occurring due to the load fluctuation.