Fuel injection system for internal combustion engines

Claim 1

In a fuel injection system for an internal combustion engine having a pump-and-nozzle assembly per cylinder which assembly comprises a pump piston and a pump work space therefor; a servo piston having a larger diameter than said pump piston and driving the latter; a pressure source to which said assembly is connected; a servo pressure space, limited on one side thereof by a frontal face of said servo piston; a fuel feed valve; said pressure source being adapted for delivering fuel to said pump work space via said fuel feed valve as well as to said servo pressure space; a valve slide adapted for being driven by a portion of the fUel delivered by said pressure source; and a fuel return line and a control device for controlling said valve slide synchronously with the work cycle of the engine, wherein said valve slide controls in a first indexing position the flow of fuel to said servo pressure space, and in a second indexing position the flow of fuel from said servo pressure space to said fuel return line, thereby rendering possible the return stroke of said servo piston and simultaneously the intake stroke of said pump piston, the improvement of each pump-and-nozzle assembly in said system comprising a. a 3:2-path solenoid valve being disposed near said valve slide and being adapted, when energized, for establishing communication between said pressure source and said valve slide, whereby the latter is movable into said first indexing position initiating the injection of fuel; b. a pre-set throttle member being interposed between said pressure source and said fuel feed valve and being adapted for influencing the velocity of the intake stroke of said pump piston; and c. a 2:2-path solenoid valve interposed in said fuel return line and comprising adjusting means for varying the opening periods thereof, thereby determining, in a second indexing position of said valve slide, the duration and length of the intake stroke of said pump piston and together therewith the amount of fuel delivered in the interval between two fuel injections.