Fuel injector nozzle assembly having anti-cavitation vent and method

A fuel injector for an internal combustion engine comprising:

• an injector housing including a longitudinal axis and having formed therein a plunger cavity, a nozzle supply passage, a nozzle cavity, a plurality of spray orifices, a spring cavity, and a stop cavity;
• a plunger movable within the plunger cavity to pressurize a fuel for injection;
• a tappet coupled to the plunger and structured to contact a cam lobe of a camshaft;
• an outlet check having a tip positioned within the nozzle cavity, a stop positioned within the stop cavity, and an opening hydraulic surface exposed to a fluid pressure of the nozzle cavity, and the outlet check being movable between a closed position where the tip contacts the injector housing to block the plurality of spray orifices, and an open position where the stop contacts the injector housing;
• a biasing spring positioned within the spring cavity and coupled to the outlet check to bias the outlet check toward the closed position;
• a clearance is formed between the outlet check and the injector housing and fluidly connects the spring cavity to the stop cavity;
• an anti-cavitation vent is formed in the injector housing and structured to limit fluid pressure changes in the spring cavity;
• the anti-cavitation vent fluidly connects the spring cavity to a low pressure space, such that fluid is displaced from the spring cavity through the anti-cavitation vent in response to positioning the outlet check at the open position, and fluid is returned through the anti-cavitation vent to the spring cavity in response to commencing moving the outlet check from the open position back to the closed position
• a leakage path extends between the nozzle end piece and the outlet check and fluidly connects the nozzle cavity to the stop cavity;
• and
• the outlet check includes a reduced diameter portion extending through the clearance, and an enlarged diameter portion forming the stop, and the enlarged diameter portion is positioned within the stop cavity at each of the open position and the closed position.

A method of operating a fuel injector for an internal combustion engine comprising:

• increasing a pressure of fuel in a nozzle cavity in the fuel injector;
• actuating an outlet check in the fuel injector to an open position in response to the increased pressure of fuel in the nozzle cavity;
• conveying fuel from the nozzle cavity through a leakage path, between an outlet check and a housing of the fuel injector, to a stop cavity, and from the stop cavity to a spring cavity, in response to the increased pressure of fuel in the nozzle cavity;
• displacing fuel in the spring cavity through an anti-cavitation vent to a low pressure space in response to positioning the outlet check at the open position;
• restricting a flow of the displaced fuel through the anti-cavitation vent so as to limit a decrease in a fluid pressure in the spring cavity;
• reducing a pressure of fuel in the nozzle cavity;
• commencing actuating the outlet check back to a closed position in response to the reduction in the pressure of fuel in the nozzle cavity using a biasing spring in the fuel injector;
• returning fuel to the spring cavity from the low pressure space in response to the commencing of the actuating of the outlet check back to the closed position;
• conveying the returning fuel to the spring cavity through an anti-cavitation vent in the fuel injector;
• and
• limiting production of cavitation bubbles in the spring cavity during actuating the outlet check back to the closed position based on the limiting of the decrease in a fluid pressure in the spring cavity.