Patent ID: 8566005

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, 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 maximum fuel injection rate computing unit configured to compute a maximum fuel injection rate 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 and a rising waveform of the fuel pressure during a period in which the fuel pressure increases due to the fuel injection rate decrease; wherein the maximum fuel injection rate computing unit includes a falling-modeling unit configured to model the falling waveform by a falling-modeling function and a rising-modeling unit configured to model the rising waveform by a rising-modeling function, and the maximum fuel injection rate computing unit is configured to compute the maximum fuel injection rate based on the falling-modeling function and the rising-modeling function wherein the maximum fuel injection rate computing unit includes a reference pressure computing unit to compute a reference pressure based on a fuel pressure right before the falling waveform is generated, and an intersection pressure computing unit configured to compute an intersection pressure at an intersection point of a first line expressed by the failing-modeling function and a second line expressed by the rising-modeling function, and the maximum fuel injection rate computing unit configured to compute a maximum fuel injection rate based on a pressure difference between the reference pressure and the intersection pressure, wherein the maximum fuel injection rate computing unit is configured to compute the maximum fuel injection rate such that the maximum fuel injection rate is larger as the intersection pressure is smaller in a case that the pressure difference between the reference pressure and the intersection pressure is smaller than or equal to value, and the maximum fuel injection rate computing unit is configured to compute the maximum fuel injection rate based on the specified upper value without respect to the intersection pressure in a case that the pressure difference is greater than the specified value.