Patent ID: 8423263

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 configured to detect a fuel pressure which varies due to a fuel injection from the fuel injection port; and a processing system, comprising a computer processor, the processing system being configured to: subtract a pressure waveform generated by a first fuel injection from a pressure waveform generated by a second or successive fuel injection and compute an actual fuel-injection-start timing based on a falling waveform of the fuel pressure during a period in which the fuel pressure decreases due to a fuel injection rate increase; model the falling waveform by a mathematical formula and compute a reference pressure based on a fuel pressure right before a fuel pressure drop due to a fuel injection is generated; compute the-fuel-injection-start timing based on timing at which a fuel pressure derived from the mathematical formula is equal to the reference pressure; compute the reference pressure with respect to a first fuel injection; and subtract a pressure drop amount depending on a fuel infection amount of a previous fuel injection from the reference pressure computed with respect to the first fuel injection, the subtracted reference pressure being used as a new reference pressure for computing a fuel-injection-start timing of the second or successive fuel injection.