Fuel injection pump

Claim 1

In a fuel injection pump for an internal combustion engine, including: a housing, a barrel mounted within said housing; a plunger mounted within said barrel for axial and rotary motion therein; a pump working chamber defined by the housing, the barrel and the plunger; a suction chamber formed within said housing; and outlet pressure lines for connecting said pump working chamber with associated fuel injection nozzles; the improvement which comprises: a relief passage having one end thereof opening in said pump working chamber and the other end communicating with a zone under a lower pressure, said relief passage extending from said barrel through said housing; a valve means arranged for blocking said relief passage; and an actuating means for actuating said valve means in response to a fuel supply pressure varying as a function of engine rotational speed, said actuating means being arranged to actuate said valve means to permanently keep said relief passage closed except in a predetermined low engine speed range; said valve means comprising a bore formed within said pump housing and communicating on one side with said relief passage and on the other side with a zone under a lower pressure; a piston slidably received with said bore, said piston including an annular groove formed in an outer periphery thereof, and a restriction passage having one end thereof radially opening in said annular groove and the other end communicating with said lower pressure zone; and said actuating means comprising a passage means having one end thereof communicating with one end of said bore and the other end thereof with a fuel pump arranged for rotation at a speed which is a function of the rotational speed of the engine; said pressure means comprising a fuel supply line having two ends, one end of said fuel supply line communicating with said suction chamber formed within said pump housing, which is supplied with a fuel pressure which is a function of the engine speed from said fuel pump, and the other end of said fuel supply line being arranged for communication with said pump working chamber; a further annular groove formed around an outer periphery of said barrel and intersecting with said fuel supply line; and a communicating port formed within said housing and providing communication between said further annular groove and said bore.