Patent ID: 7784447

Claim:
A fuel injection system of an internal combustion engine, comprising: a variable-delivery high-pressure pump having at least one pumping element operating reciprocatingly to perform an intake stroke and a delivery stroke, said at least one pumping element having an intake valve communicating with an intake conduit, and a delivery valve communicating with a delivery conduit; a regulating device located along said intake conduit for regulating the delivery of said pump, said regulating device comprising an on-off solenoid valve for defining the quantity of fuel supplied to said at least one pumping element, and a pressure regulator for maintaining a predetermined constant fuel pressure upstream from the on-off solenoid valve; and a control unit for controlling said on-off solenoid valve as a function of the operating conditions of the engine, wherein said control unit controls said on-off solenoid valve asynchronously with respect to said intake stroke by at least frequency-modulated control signals (A), wherein a maximum instantaneous flow of said on-off solenoid valve is as much as 20% less than the maximum instantaneous flow drawn by said intake valve, and wherein an intake fuel storage volume is located between said on-off solenoid valve and said intake valve to supply each pumping element over variable portions of the relative intake stroke, said high-pressure storage volume being also provided with a solenoid drain valve, said control unit also controlling opening and closing of said solenoid drain valve, and wherein the mean flow of said on-off solenoid valve is greater than the mean flow drawn by said intake valve.