Patent ID: 8554448

Claim:
A fuel injection detecting device detecting a fuel injection condition, the fuel injection detecting device being applied to a fuel injection system in which a fuel injector injects a fuel accumulated in an accumulator and a multi-stage fuel injection is performed during one combustion cycle, the fuel injection detecting device comprising: a fuel pressure sensor provided in a fuel passage fluidly connecting the accumulator and a fuel injection port of the fuel injector, the fuel pressure sensor detecting a fuel pressure which varies due to a fuel injection from the fuel injection port; and a fuel-injection-end timing computing means for subtracting a fuel pressure waveform generated by former fuel injections until (n−1)-th (n≧2) fuel injection from the fuel pressure waveform detected by the fuel pressure sensor with respect to n-th (n≧2) fuel injection, and for computing an actual fuel-injection-end timing based on a rising waveform of the fuel pressure during a period in which the fuel pressure increases due to a fuel injection rate decrease; wherein: the fuel-injection-end timing computing means includes a modeling means for modeling the rising waveform by a mathematical formula, a reference pressure computing means for computing a reference pressure based on a fuel pressure right before a fuel pressure drop due to a fuel injection is generated, and the fuel-injection-end timing computing means computes the fuel-injection-end timing based on the mathematical formula modeled by the modeling means; the reference pressure computing means computes the reference pressure with respect to a first fuel injection, and the fuel-injection-end timing computing means subtracts a pressure drop amount depending a fuel injection amount of previous fuel injections from the reference pressure computed with respect to the first fuel injection, and defines the obtained pressure as a reference pressure for computing the fuel-injection-end timing of the second and successive fuel injection.