Fuel injection nozzle for an internal combustion engine

A fuel injector nozzle assembly for use with a fuel injector pump in an internal combustion engine having an air/fuel mixture combustion chamber, the nozzle assembly comprising:

• a nozzle housing including a nozzle tip portion, at least one fuel spray nozzle orifice in the nozzle tip portion;
• a needle valve in the nozzle tip portion, a first end of the needle valve being engageable with the nozzle tip portion and closing the nozzle orifice when the needle valve assumes a first position and opening the nozzle orifice when the needle valve assumes a second position;
• a damper plate adjacent a second end of the needle valve, a fuel flow passage in the damper plate;
• a damper pin in the fuel flow passage, one end of the damper pin engaging the second end of the needle valve;
• a compression spring with a single, linear spring constant in a spring chamber acting on the damper pin and biasing the needle valve throughout a range of movement of the needle valve between the first and second needle valve positions whereby a pilot fuel injection pulse is established as the needle valve moves from the first position to the second position;
• the spring chamber being in the nozzle housing, a high pressure needle valve fuel feed passage communicating with the nozzle tip portion, a flow control orifice between the spring chamber and the high pressure needle valve fuel feed passage whereby a pressure buildup in the high pressure needle valve fuel feed passage is followed by a delayed pressure buildup in the spring chamber;
• a calibrated clearance between the damper pin and the fuel flow passage thereby defining a flow restriction;
• and
• an accumulator chamber between the second end of the needle valve and the damper plate, the damper pin extending into the accumulator chamber whereby the fluid displaced from the accumulator chamber by the needle valve, as the needle valve is shifted under pressure toward the damper plate, passes through the flow restriction, the pilot fuel injection pulse being followed by a main fuel injection pulse.