Pneumatic diaphragm control element for a fuel injection apparatus in internal combustion engines

A pneumatic diaphragm control element for a fuel injection apparatus having a control member in internal combustion engines, particularly supercharged Diesel engines, comprising a housing, a thrust rod arranged to act on said control member of said fuel injection apparatus, said thrust rod being connected to a diaphragm fastened in said housing and arranged to protrude into a pressure chamber defined on one side by said diaphragm and on the other side by housing cover, a restoring spring in said housing adapted to cooperate with said thrust rod and an adjustable abutment in said housing, said pressure chamber arranged to enclose first and second end stops for limiting the axial displacement of said thrust rod, said first end stop including a screw means adjustably supported in said housing cover in axial alignment with an end of said thrust rod and arranged to define a position of repose assumed by said thrust rod determined by a pressure-free condition in said pressure chamber, said second of said end stops disposed in said pressure chamber is adapted to define the operating position of said thrust rod assumed at a pre-specified pressure in said pressure chamber, said second end stop further arranged to cooperate with a counterpart stop that is adjustable relative to said thrust rod and is coupled therewith over at least a portion of the displacement travel thereof, said counterpart stop being further embodied as part of a prestressed spring assembly which contains at least one compression spring having at least two axially disposed stop positions, said spring assembly is disposed in the pressure chamber and embodied as a pre-assembled unit with infinitely adjustable spring pre-stressing force of the compression spring, said spring assembly includes two components that are coaxial with said thrust rod and said compression spring is disposed axially therebetween, said two components being displaceable relative to one another and operatively connected to said thrust rod so that a relative movement that compresses said compression spring does not begin until after the attainment of first stop position whereby a first displacement travel (S.sub.1) of said thrust rod upon attaining said first stop position and after the spring pre-stressing force of the compression spring is overcome, a further displacement travel (S.sub.2) of said thrust rod is available up to the attainment of said second stop position at said second end stop.