Fuel injection device

In a fuel injection system for internal combustion engines, having a fuel injector that can be supplied from a high-pressure fuel source, wherein a pressure booster device having a movable pressure booster piston is connected between the fuel injector and the high-pressure fuel source, and the pressure booster piston separates a chamber that is connectable to the high-pressure fuel source from a high-pressure chamber communicating with the fuel injector, and by filling a return chamber of the pressure booster device with fuel and by evacuating the return chamber of fuel, the fuel pressure in the high-pressure chamber can be varied, and the fuel injector has a movable closing piston for opening and closing injection openings, the improvement wherein the movable closing piston (13;

• 113) protrudes into a closing pressure chamber (12;
• 112), whereby the closing piston can be subjected to fuel pressure to attain a force acting in the closing direction on the closing piston, and wherein the closing pressure chamber (12;
• 112) and the chamber (26;
• 126) are formed by a common work chamber with all the portions (12, 47, 26;
• 112, 130, 126) of the work chamber communicating (47;
• 130) permanently with one another for exchanging fuel.