Patent ID: 7891337

Claim:
A fuel injection system for an internal combustion engine comprising: a fuel injector having a configuration to spray fuel into an internal combustion engine; and an injection controller having a configuration to execute an injection instruction function when a given learning condition is encountered, the injection instruction function being to instruct said fuel injector to perform learning injection events in sequence to inject fuel into the internal combustion engine for injection durations different from each other, said injection controller also executing an actual injection quantity determining function and a correction function, the actual injection quantity determining function being to monitor a change in operating condition of the internal combustion engine which arises from injection of fuel into the internal combustion engine to learn an actual injection quantity that is a quantity of the fuel expected to have been sprayed from said fuel injector in each of the learning injection events, the correction function being to determine an injection characteristic of the fuel injector based on the actual injection quantities, as determined by said actual injection quantity determining function, the correction function also being executed to determine a correction value based on the injection characteristic of said fuel injector which is required to correct an injection duration for which said fuel injector is to be opened to spray a target quantity of the fuel so as to bring a quantity of the fuel actually sprayed from said fuel injector close to the target quantity; wherein the injection instruction function determines the injection duration for use in a latter one of any consecutive two of the learning injection events so as to decrease a deviation of the actual injection quantity in a former one of the consecutive two of the learning injection events from a target quantity that is a quantity of the fuel said fuel injector has been instructed to spray in the former one of the consecutive two of the learning injection events, the injection instruction function also determining each of the injection durations for use in a third or subsequent one of the leaning injection events so as to change one of the injection duration and a target quantity of the fuel to be sprayed for use in a third one of any consecutive three of the learning injection events in a direction opposite a direction in which the one of the injection duration and the target quantity has been changed in a second one of the consecutive three of the learning injection events from that in a first one of the consecutive three of the leaning injection events.