Fuel injection nozzle

A fuel injection nozzle for an internal combustion engine, comprising:

• an elongated, generally tubular, one-piece monolithic nozzle body having a substantially flat end face at one end thereof and having means defining a spray hole at the other end thereof, a central bore extending through said nozzle body from said flat end face to said spray hole, said bore including a first bore portion adjacent said end face, a second bore portion adjacent the spray hole, and an undercut bore portion connecting said first and second bore portions, each of said bore portions being generally coaxial with and symmetrical about a longitudinal axis of said bore, said second bore portion being significantly longer than said first and undercut bore portions, said nozzle body including a large diameter portion, a small diameter portion, and an intermediate diameter portion connecting said large and small diameter portions, said first and undercut bore portions being provided in said large diameter portion, said second bore portion extending through said intermediate and small diameter portions, said first and second bore portions having approximately equal diameters, said undercut bore portion being larger in diameter than said first and second bore portions, said second bore portion having a tapered part adjacent said spray hole, said tapered part having a gradually increasing diameter as it extends away from said spray hole;
• said large diameter portion having a fuel supply passage provided therein and connecting said end face with said undercut bore portion, said fuel supply passage including a first passage portion which extends from said end face substantially parallel to the longitudinal axis of said central bore, said first passage portion extending alongside said first bore portion and being spaced radially outwardly therefrom, said fuel supply passage further including a second, elongated passage portion which extends between and intersects both said undercut bore portion and said first passage portion, the intersection of said first and second passage portions being closer to said end face than the intersection of said second passage portion and said undercut bore portion, said first passage portion and said first bore portion being approximately equal in length, said second passage portion being inclined relative to said first passage portion and extending from said undercut bore portion radially outwardly and axially towards said end face, said second passage portion having a diameter which is substantially smaller than the axial length of said undercut bore portion, said first passage portion having a diameter which is approximately equal to the diameter of said second passage portion;
• said nozzle body further including a web disposed radially between said central bore and said fuel supply passage, said web extending axially from said end face and terminating in a free end adjacent the intersection of said second passage portion and said undercut bore portion, said web having a generally uniform radial thickness as it extends from said end face to the intersection of said first and second passage portions, said web having a progressively and continuously decreasing radial thickness as it extends from the intersection of said first and second passage portions to said free end;
• and
• an elongate and generally cylindrical valve member slidably disposed in said central bore of said nozzle body, said valve member including a large diameter portion which is snugly but slidably fitted in said first bore portion, a reduced diameter portion adjoining said large diameter portion and disposed in said second bore portion, said reduced diameter portion being longer than said large diameter portion, said large diameter portion and said reduced diameter portion having respective outer peripheral surfaces which are radially offset from each other, said valve member including an annular face defined radially between said radially offset outer peripheral surfaces of said adjoining large and reduced diameter portions, said reduced diameter portion extending from said annular face and terminating in a valve tip, said valve tip including a pair of adjoining frusto-conical surfaces, the junction of said adjoining frusto-conical surfaces being adapted to seat on a seating surface defined by a part of said nozzle body surrounding said tapered part of said second bore portion.

A method of mixing a fuel injection nozzle body for an internal combustion engine, comprising the steps of:

• (a) providing a one-piece monolithic nozzle body having a nozzle body tip formed with at least one spray hole, and a bore extending from an end face of said body to said nozzle body tip, said bore having first and second portions connected by an undercut bore portion, each of said bore portions being generally coaxial with and symmetrical about a longitudinal axis of said bore, said first portion extending from said end face;
• (b) forming a first fuel passage portion of circular cross-section extending from said end face substantially parallel to the longitudinal axis of said bore, said first passage portion extending alongside said first bore portion and being spaced radially outwardly therefrom;
• and
• (c) forming from within said bore a second fuel passage portion of circular cross-section extending from said undercut bore portion;
• said first and second fuel passage portions being orientated to intersect to form a fuel supply passage, in which said second passage portion has a diameter which is substantially smaller than the axial length of said undercut bore portion, and the diameter of said first fuel passage portion is approximately equal to the diameter of said second passage portion.