Diesel fuel injection pump with electromagnetic fuel spilling valve having pilot valve providing high responsiveness

Claim 1

A fuel injection system for a diesel engine having a plurality of cylinders coupled to a crankshaft, the fuel injection system comprising: a housing with a cylindrical bore formed therein; an input shaft mounted coaxially with said bore and rotatable in a predetermined phase relation with the crankshaft of the engine; a plunger slidably mounted in said bore, one end of the plunger defining with the bore a high pressure chamber, and another end of the plunger being rotationally engaged with said input shaft but being free to move axially with respect to the input shaft; means for axially reciprocating said plunger in the bore according to the rotational position of the plunger; means for communicating said high pressure chamber selectively with respective cylinders of the engine according to the rotational position of said plunger substantially only when the plunger is moving in a delivery stroke, axially in a direction to reduce the size of said high pressure chamber; a valve body having an internal chamber communicating with said high pressure chamber, with a vent passage leading from the internal chamber for venting said high pressure chamber; a valve element located in said internal chamber and having an orifice, one side of the orifice communicating with said high pressure chamber, said valve element controlling said vent passage so as to close said vent passage when said valve element is shifted to an end position of the valve element with no pressure difference existing through said orifice opening and to open said vent passage when said valve element is shifted away from said end position to be more remote from said high pressure chamber due to a pressure difference caused through said orifice opening; an electromagnetically operated pilot valve which is selectively electromagnetically driven when electrical energy is supplied thereto so as to close a normally open passage which vents a space on the other side of said orifice remote from said high pressure chamber; and control means for selectively actuating and deactuating said electromagnetic valve so as to provide injected fuel in appropriate amounts to the engine, wherein said control means comprises: means for calculating a first amount of fuel for a pilot fuel injection spirt and a second amount of fuel for a main fuel injection spirt for each combustion stroke of each cylinder of the engine based upon data with regard to operation of the engine, the results of calculation of said first and second amounts being reduced, during each delivery stroke of said plunger, to first and second time points when said pilot fuel injection spirt is started and ended, respectively, and third and fourth time points when said main fuel injection spirt is started and ended, respectively; and means for supplying electric current to said electromagnetically operated pilot valve in the period between said first and second time points and in the period between said third and fourth time points.