Patent ID: 7021278

Claim:
A fuel injection system for an internal combustion engine, comprising: an injector including a control chamber to which a fuel supply pressure is applied through an inflow passage and from which the fuel supply pressure is exhausted through an exhaust passage and an electric valve which opens and closes said exhaust passage, and which drive-controls a needle through controlling the pressure of said control chamber; and a control device for determining a required injection amount in accordance with an operation state of the internal combustion engine, and which controls a fuel injection amount injected from said injector through controlling said electric valve based on the required injection amount, wherein said control device includes injection model evaluation means for: determining a geometric shape defined by a time axis and a lift-height change of said needle, said geometrical shape having an area directly or indirectly corresponding to said required injection amount which is employed for evaluating an injector driving period, said injector driving period from a driving signal generation timing of said injector to a driving signal termination timing of said injector or the driving signal termination timing after the driving signal generation, dividing said lift-height change of said needle during the period from when said needle starts moving up to when said needle starts moving down into a plurality of portions upon determining said geometrical shape, said plurality of portions defined by: the lift-height change of said needle during a first lift-up period that occurs just after when said needle starts moving up, the lift-height change of said needle during a second lift-up period that occurs from an end of said first lift-up period to when the pressure in said control chamber becomes almost constant, and the lift-height change of said needle during a third lift-up period that occurs from the end of the second lift-up period to when said needle starts moving down; and evaluating said lift-height change of said needle in each of said first, second, and third lift-up periods based on a physical equation.