Apparatus for controlling fuel injection timing

Abstract

In a diesel engine controlling system having a fuel injection pump, a fuel injection timing adjusting device is controlled by a drive pulse signal whose duty cycle is controlled by a microcomputer. The duty cycle is determined such that a basic duty cycle obtained by using engine rotational speed and injection quantity, is modified or corrected by way of a correction factor and a forecast correction factor. The-first mentioned correction factor comprises an integration component and a proportional component both derived from the difference between a measured fuel injection or ignition timing and a desired or reference fuel injection or ignition timing, which is calculated by using the engine rotational speed and the injection quantity. The forecast correction factor corresponds to a differential value of the basic duty cycle or the desired fuel injection or ignition timing. In order to detect the fuel injection or ignition timing a timing detector is employed, where the state of an output signal from the detector is monitored to prohibit calculation of the difference or error, thereby correcting the basic duty cycle by only the forecast correction factor when the detector is in abnormal condition.