Fuel injection system

A fuel injection system comprising:

• a common rail which preserves a fuel pressurized;
• a booster unit which intensifies the fuel supplied from the common rail thereby to transfer the fuel to a needle valve mechanism of an injector;
• a needle valve drive unit which drives the needle valve of the needle valve mechanism to open or close;
• and
• a controller which controls the booster unit and the needle valve drive unit,
• wherein the booster unit has:
• a pressure chamber which admits the fuel transferred from the common rail;
• a booster piston provided in the pressure chamber;
• a backpressure chamber which is separated by the booster piston from the pressure chamber and which admits the fuel transferred from the common rail;
• a discharge valve which is able to discharge the fuel existing in the backpressure chamber;
• and
• a booster chamber which, when the fuel in the backpressure chamber is discharged, uses a portion moving integrally with the booster piston to thereby intensify the fuel and then transfers the fuel to the needle valve mechanism,
• the needle valve drive unit has:
• a pressurization chamber which admits the fuel transferred from the common rail;
• an open/close valve which is able to discharge the fuel existing in the pressurization chamber;
• and
• a pressure-receiving piston which is accommodated in the pressurization chamber and moves in the direction of opening the needle valve in conjunction with discharge of the fuel existing in the pressurization chamber, and
• the controller has:
• booster piston pseudo-operation means for opening the discharge valve at timing other than timing of injection operation of the injector in the event that necessity arises for reducing pressure in the common rail in correspondence to any one of an engine operation state and accelerator operation state.