FUEL INJECTION CONTROL METHOD FOR AN INTERNAL COMBUSTION ENGINE AND ULTRA-LOW ENGINE SPEED DETECTING DEVICE

摘要

A fuel injection control method for an internal combustion engine constituted by a gear-like pulser (7) designed to rotate in synchronism with the rotation of a fuel injection pump (1) and an electromagnetic pick-up (35) and having a revolution detecting means for generating a pulse at every predetermined angle, whereby an electromagnetic spill valve (23) is closed at a time when a reference signal is outputted which is generated every time a missing tooth formed in the gear-like pulser (7) is detected or at a timing when a predetermined period of time lapses after the output of the signal, while the electromagnetic valve is opened based on a fuel injection amount calculated in accordance with the operating conditions of the internal combustion engine and a pulse detected by the revolution detecting means, the method comprising the steps of judging at a position in the vicinity of the top dead center (TDC) of a piston where the engine speed becomes ultra-low in every cycle of the internal combustion engine whether or not a current operating condition is in a non-detective area in which the pulse cannot be detected (steps 102 to 104), and when the engine speed is ultra-low, calculating a period of time when the electromagnetic spill valve is to be openend based on information given by a pulse detected in the vicinity of the non-detective area out of the detected pulses (steps 107, 108).