Patent ID: 7523739

Claim:
A fuel injection system for an internal combustion engine, comprising: a fuel injection apparatus for pressurizing low-viscosity fuel by using a plunger of the fuel injection apparatus to feed pressurized fuel to a fuel injection nozzle; a fuel tank for holding the low-viscosity fuel; a fuel supply pump for supplying the low-viscosity fuel from said fuel tank to said fuel injection apparatus; a lubricity improver tank for holding a lubricity improver to be supplied to the low-viscosity fuel supplied to said fuel injection apparatus; a biofuel supply means for supplying biofuel to be mixed with the low-viscosity fuel supplied to said fuel injection apparatus; a controller for controlling said biofuel supply means so that the amount of biofuel that is mixed with the fuel supplied to said fuel injection apparatus decreases as engine rotation speed or engine load increases; and at least one of (a) a temperature sensor for detecting the temperature of the fuel after biofuel is added thereto and (b) a viscosity sensor for detecting the viscosity of the fuel after the biofuel is added; wherein said controller calculates and controls the amount of biofuel to be supplied by said biofuel supply means on the basis of (a) at least one of the temperature detected by said temperature sensor and the viscosity detected by said viscosity sensor and (b) engine speed or load.