Fuel supply system for internal combustion engine

A fuel supply system for an internal combustion engine, which is adapted to use a mixture of a plurality types of combustible liquids as its fuel, the fuel supply system comprising:

• a fuel pump that pumps fuel from a fuel tank;
• an injector that is installed to the internal combustion engine and injects the fuel received from the fuel pump into a combustion chamber of the internal combustion engine;
• a fuel supply line that communicates between the fuel pump and the injector;
• a fuel property sensor that is installed to the fuel supply line and outputs a measurement signal indicating a property of the fuel that flows through the fuel supply line;
• a fuel consumption computing means for computing a consumed quantity of fuel, which is consumed by the internal combustion engine;
• a fuel property estimating means for computing a fuel property value of the fuel based on a measurement signal received from the fuel property sensor every time the consumed quantity of fuel reaches a value equal to a volume of each of a plurality of imaginary passage cells, which have equal volumes, respectively, and are arranged one after another in a flow direction of the fuel in a portion of the fuel supply line that extends from the fuel property sensor to the injector, wherein:
• the fuel property estimating means stores the computed fuel property value as a current fuel property value associated with a first one of the plurality of imaginary passage cells, which is closest to the fuel property sensor among the plurality of imaginary passage cells;
• the fuel property estimating means sequentially shifts each fuel property value stored in association with a corresponding one of the plurality of imaginary passage cells as a fuel property value associated with an adjacent downstream side one of the plurality of imaginary passage cells located on a downstream side thereof every time the consumed quantity of fuel reaches the value equal to the volume of each imaginary passage cell;
• and
• when the fuel property estimating means shifts the fuel property value associated with the first one of the plurality of imaginary passage cells as a fuel property value associated with a second one of the plurality of imaginary passage cells located on the downstream side of the first one of the plurality of imaginary passage cells, the fuel property estimating means corrects the fuel property value associated with the second one of the plurality of imaginary passage cells by computing a difference between the fuel property value associated with the first one of the plurality of imaginary passage cells and the fuel property value associated with the second one of the plurality of imaginary passage cells and multiplying the difference by a correction coefficient;
• and
• an injector driving means for driving the injector, wherein:
• the injector driving means computes a stoichiometric air/fuel ratio based on the fuel property value, which is associated with a last one of the plurality of imaginary passage cells that is closest to the injector among the plurality of imaginary passage cells, and then computes an injection quantity of fuel based on the computed stoichiometric air/fuel ratio;
• the injector driving means drives the injector based on the computed injection quantity of fuel;
• the fuel supply system further comprises an oxygen sensor, which senses an oxygen concentration of exhaust gas of the internal combustion engine, wherein:
• the fuel property estimating means computes an actual air/fuel ratio of the internal combustion engine based on the oxygen concentration, which is sensed with the oxygen sensor;
• the fuel property estimating means computes a fuel property value of the fuel conducted through the fuel supply line based on the actual air/fuel ratio;
• and
• the fuel property estimating means corrects the correction coefficient based on the fuel property value, which is computed based on the measurement signal of the fuel property sensor, and the fuel property value, which is computed based on the actual air fuel ratio.