Cummins Engine Company, Inc.

R Michael Harmon

George L Muntean

Gary L Gant

C Edward Morris, Jr

David E Shultz

The present invention is directed to open nozzle unit fuel injectors for injecting a metered quantity of fuel into the cylinder of an internal combustion engine, as synchronously controlled by a drive train, wherein the unit fuel injector comprises a body with an axial bore and a plunger assembly movable therein between a retracted position and an advanced position. The plunger includes a major diameter section, slidably movable in the axial bore to open and close a fuel supply orifice and a minor diameter section which extends in a bore of a cup portion of the injector body. The cup portion has an internal surface including plural diameter portions connected by an annular step. In accordance with the present invention, the fuel supply orifice is specifically located within the axial bore and the plunger minor diameter section is designed such that when the plunger is moved from its retracted to its advanced position, a portion of the minor diameter section becomes radially engaged, or almost engaged, with one of the plural cup surface sections before the major diameter plunger section closes the fuel supply orifice. The engagement being between the minor diameter portion and one of the plural cup internal surface sections that will be nearest to one another during the entire range of plunger movement from the retracted to advanced positions.

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Seymour, IN, United States of America

R Michael Harmon