Fuel supply system and fuel supply control method for internal combustion engine

A fuel supply system for an internal combustion engine, which is adapted to use any one of alcohol fuel, non-alcohol liquid fuel and a mixture of the alcohol fuel and the non-alcohol liquid fuel as its fuel, the fuel supply system comprising:

• an injector that is installed to the internal combustion engine and injects fuel into a combustion chamber of the internal combustion engine;
• a fuel supply line that supplies the fuel to the injector;
• an alcohol concentration sensor that is installed to the fuel supply line and outputs a measurement signal, which indicates an alcohol concentration of the fuel conducted through the fuel supply line;
• and
• a controller that computes and stores a fuel-specific value, which is one of the alcohol concentration of the fuel and a value derived from the alcohol concentration of the fuel, based on the measurement signal received from the alcohol concentration sensor every time the internal combustion engine consumes a predetermined quantity of fuel through injection of the fuel from the injector, so that a plurality of fuel-specific values is stored in the controller after execution of the computation of the fuel-specific value a plurality of times, wherein:
• when the controller determines that a difference between one of the plurality of fuel-specific values and a subsequently computed one of the plurality of fuel-specific values is equal to or larger than a preset value, the controller corrects the subsequently computed one of the plurality of fuel-specific values in a manner that reduces the difference between the one of the plurality of fuel-specific values and the subsequently computed one of the plurality of fuel-specific values;
• and
• the controller controls fuel injection of the injector based on the subsequently computed one of the plurality of fuel-specific values at time of injecting the fuel, which corresponds to the subsequently computed one of the plurality of fuel-specific values.

A fuel supply control method for controlling fuel supply at an internal combustion engine, which is adapted to use any one of alcohol fuel, non-alcohol liquid fuel and a mixture of the alcohol fuel and the non-alcohol liquid fuel as its fuel, the fuel supply control method comprising:

• computing and storing a fuel-specific value, which is one of an alcohol concentration of the fuel and a value derived from the alcohol concentration of the fuel, based on a measurement signal received from an alcohol concentration sensor installed to a fuel supply line connected to an injector every time the internal combustion engine consumes a predetermined quantity of fuel through injection of the fuel from the injector, so that a plurality of fuel-specific values is stored after execution of the computation of the fuel-specific value a plurality of times;
• computing a difference between one of the plurality of fuel-specific values and a subsequently computed one of the plurality of fuel-specific values;
• correcting the subsequently computed one of the plurality of fuel-specific values in a manner that reduces the difference between the one of the plurality of fuel-specific values and the subsequently computed one of the plurality of fuel-specific values when the difference between the one of the plurality of fuel-specific values and the subsequently computed one of the plurality of fuel-specific values is equal to or larger than a preset value;
• and
• controlling fuel injection of the injector based on the subsequently computed one of the plurality of fuel-specific values at time of injecting the fuel, which corresponds to the subsequently computed one of the plurality of fuel-specific values.