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A variation waveform of fuel pressure is obtained by use of a fuel pressure sensor which detects pressure of fuel supplied to an injector. A quantity of fuel supplied to the injector is estimated based on a waveform of the detected pressure that is greater than a reference value due to a fuel pumpin

A variation waveform of fuel pressure is obtained by use of a fuel pressure sensor which detects pressure of fuel supplied to an injector. A quantity of fuel supplied to the injector is estimated based on a waveform of the detected pressure that is greater than a reference value due to a fuel pumping, in the obtained variation waveform. Especially, in a case that the fuel pressure sensor is provided to each of a plurality of injectors, it is desirable to obtain the variation waveform based on the output of the fuel pressure sensor provided to a cylinder in which no fuel injection is currently performed.

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1. 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 injec

1. 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; andan 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, whereinthe 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. 2. A fuel-supply quantity estimating apparatus applied to a fuel injection system including a fuel pump, a fuel injector, 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;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 estimating unit estimates the quantity of the fuel based on the waveform which is obtained when no fuel is injected from the fuel injector; anda pressure increase detecting unit for detecting a first variation point where a first-order differential value of the detected pressure exceeds a first threshold as a pressure increasing start time of the detected pressure due to the fuel pumping, whereinthe waveform after the first variation point in the variation waveform is used for estimating the quantity of the fuel supplied to the fuel injector. 3. A fuel-supply quantity estimating apparatus according to claim 2, wherein the pressure increase detecting unit detects the variation point which appears immediately after a specified time period has elapsed in which a variation width of the detected pressure is less than or equal to a specified value as the pressure increasing start time. 4. A fuel-supply quantity estimating apparatus applied to a fuel injection system including a fuel pump, a fuel injector, 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;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 estimating unit estimates the quantity of the fuel based on the waveform which is obtained when no fuel is injected from the fuel injector; andan end detecting unit for detecting a second variation point where a first-order differential value of the detected pressure is less than a second threshold as an end time of the pressure increasing of the detected pressure due to the fuel pumping, whereinthe waveform before the second variation point in the variation waveform is used for estimating the quantity of the fuel supplied to the fuel injector. 5. A fuel-supply quantity estimating apparatus according to claim 4, wherein the end detecting unit detects the variation point which appears right before a specified time period continues in which a variation width of the detected pressure is less than or equal to a specified value as the pressure increasing end time. 6. A fuel-supply quantity estimating apparatus applied to a fuel injection system including a fuel pump, a fuel injector, 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; andan 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; whereinwhen no fuel is pumped from the fuel pump, the variation waveform is previously stored as a prototype waveform which is the reference value, anda waveform deviating from the prototype waveform in the variation waveform is used for estimating the quantity of the fuel supplied to the fuel injector. 7. A fuel-supply quantity estimating apparatus applied to a fuel injection system including a fuel pump, a fuel injector, 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; andan 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; whereinwhen no fuel is pumped from the fuel pump, the variation waveform is previously stored as a prototype waveform which is the reference value, andthe estimating unit computes an area which is obtained by subtracting the prototype waveform from the variation waveform, and estimates that the area corresponds to the quantity of fuel supplied to the fuel injector.