Patent ID: 8100112

Claim:
A fuel-supply quantity estimating apparatus applied to a fuel injection system including a multi-cylinder internal combustion engine, a fuel pump, a plurality of fuel injectors respectively provided to each cylinder, and a fuel pressure sensor detecting pressure of fuel supplied to the fuel injector, the fuel-supply quantity estimating apparatus comprising: a waveform obtaining unit for obtaining a variation waveform of the pressure detected by the fuel pressure sensor; and an estimating unit for estimating a quantity of fuel supplied to the fuel injector based on a waveform of the detected pressure that is greater than a reference value due to a fuel pumping, in the variation waveform obtained by the waveform obtaining unit, wherein the fuel pressure sensor is provided to each of the fuel injectors, and the estimating unit performs the estimation based on an output of the fuel pressure sensor provided to the cylinder in which no fuel injection is currently performed.