Variable orifice fuel injection nozzle

A fuel injector nozzle (100) for a fuel injector (102) comprising:

• a nozzle body (24) constructed and arranged to be secured to an end portion of the fuel injector (102) for injecting liquid fuel into a diesel engine, the nozzle body including an orifice body (32) positioned along a longitudinal axis (38) of the nozzle body, the orifice body (32) including a plurality of nozzle orifices (50) arranged in a radial pattern around the outer perimeter of the orifice body (32) and extending inward to intersect an inner bore (60) of the orifice body (32) to provide a fluid connection therebetween;
• a pintle rod (216) is guided at least partially by the inner bore (60) of the orifice body (32), a forward end (58) of the pintle rod (216) is constructed as a cylinder to slip fit within the inner bore (60) of the orifice body (32), an undercut (64) is positioned behind the forward end (58) to provide for fuel flow between the outer diameter of the pintle rod (216) and the inner bore (60), the undercut (64) also provides a spool surface (66) for operation of the pintle rod (216) in response to fuel pressure;
• a plunger (26) is secured to a rear portion of the pintle rod (216);
• a spring (28) cooperates with the plunger (26) and the nozzle body (24) to provide a closing force to the pintle rod (216) to prevent fuel flow, the plunger (26) and spring (28) cooperate to allow the pintle rod (216) to move along the longitudinal axis (38) in response to fuel pressure being applied to the pintle rod (216), causing the pintle rod (216) to move linearly, exposing the undercut (64) to the nozzle orifices (50) allowing fuel to flow through the nozzle orifices (50), a reduction in fuel pressure allows the spring (28) to return the pintle rod (216) to position to stop the flow of fuel through the nozzle orifices (50).