Patent ID: 8646323

Claim:
An apparatus of estimating fuel injection state of a fuel injection system having at least three injectors including a first, second and third injectors provided for a first, second and third cylinders of an internal combustion engine respectively, a first fuel pressure sensor which detects pressure of fuel supplied to the first injector, and a second fuel pressure sensor which detects pressure of fuel supplied to the second injector, the apparatus comprising: a first acquisition section which acquires an injected cylinder waveform, the injected cylinder waveform being shown by fuel pressure change detected by the first fuel pressure sensor when the first injector injects fuel; a second acquisition section which acquires a first non-injected cylinder waveform, the first non-injected cylinder waveform being shown by fuel pressure change detected by the second fuel pressure sensor when the first injector injects fuel; a correlation calculation section which calculates a correlation between the injected cylinder waveform and the first non-injected cylinder waveform; a third acquisition section which acquires a second non-injected cylinder waveform, the second non-injected cylinder waveform being shown by fuel pressure change detected by the first or second fuel pressure sensor when the third injector injects fuel; an injection state estimation section which estimates fuel injection state injected from the third injector based on the second non-injected cylinder waveform and the correlation; an injection delay calculation section which calculates a first injection delay time showing a response delay of injection state with respect to an injection start command signal to the first injector based on the injected cylinder waveform; a first drop delay calculation section which calculates a first drop delay time until the first non-injected cylinder waveform begins dropping from the injection start command signal to the first injector; and a second drop delay calculation section which calculates a second drop delay time until the second non-injected cylinder waveform begins dropping from the injection start command signal to the third injector, wherein the correlation calculation section calculates the correlation between the first injection delay time and the first drop delay time, and wherein the injection state estimation section estimates a second injection delay time as the fuel injection state based on the second drop delay time and the correlation, the second injection delay time showing a response delay of injection state of the third injector with respect to an injection start command signal to the third injector.