Throttling pintle-type fuel injection nozzle having an improved initial injection characteristic

Claim 1

A throttling pintle-type fuel injection nozzle for use in a fuel injection valve having a nozzle holder and mounted in an internal combustion engine having at least one combustion chamber, said fuel injection nozzle comprising: a nozzle body fixed to said nozzle holder of said fuel injection valve, said nozzle having an axial hole, a valve seating portion and a nozzle hole formed therein and succesively arranged in the order mentioned along an axis thereof, said nozzle hole having a cylindrical configuration and having one end remote from said combustion chamber of said engine and another end opening into said combustion chamber, said nozzle hole having a substantially constant diameter along the whole length thereof; a nozzle needle mounted within said nozzle body, said nozzle needle having a guide portion slidably fitted in said axial hole of said nozzle body, a seating portion formed adjacent said guide portion and seatable on said valve seating portion of said nozzle body, a pressure-applying portion located between said guide portion and said seating portion, and a pintle formed adjacent said seating portion and disposed to be fitted through said nozzle hole of nozzle body; said axial hole of said nozzle body having a guide hole in which said guide portion of said nozzle needle is slidably fitted, and a pressure chamber formed adjacent one end of said guide hole closer to said combustion chamber and disposed to be supplied with pressurized fuel, said pressure chamber being swelled radially outwardly of said guide hole and accommodating at least part of said pressure-applying portion of said nozzle needle; said pintle of said nozzle needle having a conical portion having two ends, said conical portion being disposed such that one end of said conical portion is located slightly remoter from said combustion chamber than is said one end of said nozzle hole, and another end of said conical portion is substantially on a level with said another end of said nozzle hole opening into said combustion chamber when said seating portion of said nozzle is in a position seated on said valve seating portion of said nozzle body, said conical portion of said pintle having a diameter gradually decreasing from said one end thereof to said another end thereof; said conical portion of said pintle having an outer peripheral surface and said conical portion having a portion disposed to on a level with said one end of said nozzle hole when said seating portion is in said seated position, said portion of said conical portion having a diameter equal to the inner diameter of said one end of said nozzle hole; whereby when said seating portion of said nozzle needle is in said seated position, said pintle and said nozzle hole define therebetween an annular gap gradually expanding from said one end of nozzle hole to said another end thereof, with said one end of said nozzle hole being positiviely closed by said outer peripheral surface of said conical portion of said pintle.