Patent ID: 7040288
Filing Date: 2006-05-09
Classification: F02M

Abstract:
1. A fuel injection system comprising: a common rail which preserves a fuel pressurized; an injector having a booster unit which boosts the fuel supplied from the common rail thereby to transfer the fuel to a needle valve mechanism; and a needle valve drive unit to open or close a needle valve of the needle valve mechanism, wherein the booster unit comprises: a pressure chamber which introduces 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 into which the fuel transferred from the common rail is introduced; a discharge valve which can discharge the fuel in the backpressure chamber; and a booster chamber which, when the fuel in the backpressure chamber is discharged, uses a portion that moves integrally with the booster piston thereby to boost the fuel and then transfers the fuel to the needle valve mechanism; and the needle valve drive unit has: a pressurization chamber which introduces the fuel transferred from the common rail; an open/close valve which can discharge the fuel in the pressurization chamber; and a pressure-receiving piston which is accommodated in the pressurization chamber and moves in a direction of opening the needle valve when the fuel in the pressurization chamber is discharged; and the fuel injection system further comprises: a return passage which provides communication between a discharge side of the open/close valve of the needle valve drive unit and a fuel tank; a fuel discharge passage which has one end connected to a discharge side of the discharge valve and the other end connected to a confluence portion in combination with the return passage and which can return the fuel in the backpressure chamber to the fuel tank; and a check valve provided between the confluence portion of the return passage and the open/close valve, wherein the check valve permits the fuel discharged to the return passage from the pressurization chamber to be directed to the confluence portion, and prevents the fuel discharged to the fuel discharge passage from the backpressure chamber from being directed to the open/close valve.