Fuel-injection device for an internal combustion engine

A fuel injection apparatus for an internal combustion engine, comprising

• a high-pressure fuel pump (10) and a fuel injection valve (12) connected to it for each cylinder of the engine,
• the high-pressure fuel pump (10) having at least one pump piston (18) that is driven into a stroke motion by the engine and delimiting a pump working chamber (22), which is supplied with fuel from a fuel tank (24),
• the fuel injection valve (12) having a pressure chamber (40) connected to the pump working chamber (22) and at least one injection valve element (28) that controls at least one injection opening (32), the pressure prevailing in the pressure chamber (40) acting on the at least one injection valve element (28) in an opening direction (29) counter to a closing force in order to open the at least one injection opening (32),
• a control valve (68) that at least indirectly controls a connection (66) of the pump working chamber (22) to a relief chamber (24) and a pressure source (23) in order to fill the pump working chamber (22) during the intake stroke of the at least one pump piston (18),
• the high-pressure fuel pump (10) having two pump pistons (18, 118) including a first pump piston (18) inside of which a second pump piston (118) is guided so that it can slide in an approximately coaxial fashion, wherein the two pump pistons (18, 118) delimit the pump working chamber (22), in that the first pump piston (18) is driven in a stroke motion, and
• means optionally coupling the two pump pistons (18, 118) to each other to move together as a unit during the delivery stroke, or decoupling the two pump pistons (18, 118) whereby the second pump piston (118) can be fixed in a passive position so that only the first pump piston (18) executes the delivery stroke.