Control of fuel-injection timing in a four-stroke spark-ignition four-stroke direct injection i.c. engine with simultaneous ignition in two cylinders

摘要

A single ignition coil is provided per two cylinders whose phase difference is 360 degrees so that simultaneous ignition occurs in one cylinder (the firing cylinder) near the end of the compression stroke) and in the other (the off-firing cylinder) near the end of the exhaust stroke. To prevent preignition in the off-firing cylinder, the combustion control system judges whether or not the spark discharge period (SPT) overlaps with the fuel injection period (Ti). If it is judged not to overlap, the fuel injection starting timing determined based on the engine speed (Ne) and the fuel injection amount (GF) is allowed to be a final fuel injection starting timing. If it is judged to overlap, the spark discharge ending timing (SPE) is obtained from the ignition timing (ADVF) and the spark discharge period (SPT) and this spark discharge ending timing is allowed to be a final fuel injection starting timing. Alternatively, a "preignition period" is determined based on experimental results and the injection is delayed if it would occur during this period. The fuel injection starting timing is thus delayed to prevent the off-firing cylinder from being fired.