Method of assembling a fuel nozzle assembly

A method for assembling a fuel injection nozzle having an elongated, generally cylindrical nozzle body having a generally cylindrical cavity at one end, a central bore extending from the cavity axially along the body, and a valve chamber having a larger diameter than the central bore, located at the other end of the body;

• a nozzle tip having a plurality of discharge orifices and a seat at one end, and a hollow central portion coaxial with said nozzle body bore, said tip being in interference engagement with said nozzle body cavity;
• an elongated valve member disposed axially within the nozzle body and nozzle tip, said valve member having a nose portion for engaging the tip seat, a stem portion extending from the tip to the valve chamber, a valve actuation portion, and a bearing surface extending upwardly from the valve actuation portion to a position above the upper end of the nozzle body;
• a substantially cylindrical valve guide member press fit into said valve chamber from the upper end thereof, and having a cylindrical guide surface portion surrounding said bearing surface:
• an inlet stud having an annular ring portion rigidly connected to the exterior of the valve body adjacent the valve member;
• a fuel inlet passage extending through the inlet stud and nozzle body to the valve chamber, for delivering fuel in measured pulses to the valve actuation surface, whereby the valve is lifted from the tip seat and the fuel is discharged through the valve chamber, nozzle body central bore, nozzle tip and discharge orifices;
• a generally cylindrical nozzle cap having a central bore and a domed upper end, said nozzle cap including means for rigidly securing the cap to the upper end of the nozzle body above the connection of the inlet stud to the nozzle body;
• a spring subassembly mounted within the nozzle cap along the nozzle body axis, including a lower spring seat in contact with the upper end of the valve, an upper spring seat in contact with the dome of the nozzle cap, a spring interposed and supported between the upper and lower spring seats, a rigid stem extending axially from one of said spring seats and a rigid pedestal extending axially from the other of said spring seats toward each other, each having a free end, thereby defining an axial gap therebetween, said spring acting through said lower spring seat to provide a downward bias on the valve against the tip seat, and said stem and pedestal providing a stop limit such that the valve can rise when actuated a distance no greater than the axial dimension of said gap;
• and
• means connected to the exterior of said nozzle cap, for withdrawing fuel that may leak into said nozzle cap through bearing clearance in the guide member;
• comprising the steps of:
• shrink fitting the annular ring portion of the inlet stud onto the nozzle body;
• drilling and burnishing a passage from the inlet stud through the nozzle body into the valve chamber;
• press fitting the nozzle tip into said cavity at one end of the nozzle body;
• press fitting the guide member into the valve chamber;
• selecting a valve member having a bearing portion with an outer diameter sized for close sliding engagement with the guide member and inserting the valve member through the nozzle body until the nose portion contacts the tip seat and the upper end of the valve member extends above the valve body and guide member;
• selecting a nozzle cap;
• determining the distance between the upper end of the valve and the dome of the nozzle cap when the nozzle cap will be fully engaged onto the nozzle body;
• measuring the desired compressed length of the spring for providing the desired downwared biasing force against the valve;
• grinding the upper surface of the upper valve seat or the lower surface of the lower valve seat such that the distance between the lower surface of the upper valve seat and the upper surface of the lower valve seat is equal to the desired length of the spring;
• grinding one of the stems or pedestals at its free end, to establish the desired gap therebetween when the spring is in the compressed condition for seating the valve;
• inserting the spring subassembly into the nozzle cap;
• and
• securing the nozzle cap into full engagement with the valve body.