Fuel injection quantity control device

A fuel injection quantity control device for controlling an actual revolution speed of an engine to a target revolution speed, comprising:

• difference computation means for subtracting the actual revolution speed from the target revolution speed and finding a difference therebetween;
• proportional term computation means for multiplying the difference by a prescribed proportionality constant and finding a proportional term output value;
• integral term computation means for finding an integral term output value which is obtained by integrating a product of the difference and a prescribed integration constant;
• differential term computation means for finding a differential term output value which is obtained by multiplying a value obtained by differentiating the difference by a prescribed differentiation constant;
• and
• injection quantity computation means for adding up the proportional term output value and integral term output value and determining the injection quantity, wherein the fuel injection quantity control device further comprises:
• correction means for limiting a lower limit of the integral term output value with the differential term output value when the difference is negative, thereby suppressing the excess reduction of the injection quantity, and limiting the upper limit of the integral term output value with the differential term output value when the difference is positive, thereby suppressing the excess increase of the injection quantity.