Fuel injection device for an internal combustion engine

Abstract

A fuel injector for a spark ignition internal combustion engine is disclosed, wherein the amount of injected fuel is increased by an extra amount when the engine is in a transient accelerating state. The air pressure within the air inlet passage to the engine is detected by an air pressure sensor, and the load condition is judged by comparing the detected pressure with a reference level. Further, the variation or increment of the detected pressure over each fuel injection period is calculated and compared with a high or a low threshold level selected in accordance with the load condition of the engine. Preferably, the high threshold level is selected when the high load condition continues over a predetermined length of time, the low threshold level being otherwise selected. The amount of transient extra increase is determined in accordance with the result of the comparison of the pressure variation with the selectd threshold level. On the other hand, the fundamental amount of injected fuel is calculated on the basis of an instantaneous current air pressure when the above amount of transient extra increase is not zero; otherwise, on the basis of an average of the pressure over the fuel injection period. The sum of the fundamental amount and the transient increase is injected in synchrony with every predetermined number pulse of the crank angle signal.