Fuel injector nozzle with pressurized needle valve assembly
AssigneeDiesel Technology Company
InventorGary L. Cowden
Life of this patent
Estimating the term…
Abstract
A nozzle assembly for a fuel injector having a needle valve for controlling an injector valve orifice, the needle valve being subjected to a spring force and a fluid pressure force. The needle valve registers with a fuel delivery orifice and is movable into and out of engagement with a valve seat surrounding the orifice. The needle valve is normally biased to a valve closing position by a spring located in a spring cage. The spring cage becomes pressurized upon movement of the needle valve toward the needle valve open position, whereby a positive pressure is maintained in the spring chamber throughout the fuel injection event. A calibrated bleed orifice allows the spring chamber pressure to decay to a low value between injection events.
Claims8
A fuel injector for an internal combustion engine comprising:
- a cylinder housing defining a cylinder opening;
- a pump plunger in the cylinder housing defining a high pressure fuel pumping chamber, an engine camshaft follower connected to the plunger;
- a plunger spring urging the plunger in a direction to increase the volume of the high pressure fuel pumping chamber, the camshaft follower driving the plunger against the force of the plunger spring to create an injection pressure in the fuel pumping chamber;
- a needle valve body having a needle valve opening;
- a fuel delivery orifice in the needle valve body, the needle valve closing the fuel delivery orifice when it is moved to a closed position;
- a needle valve spring urging the needle valve to the closed position;
- a spring cage enclosing the needle valve spring, the spring cage being in fluid communication with the needle valve opening when the needle valve is in a closed position;
- a sealing shoulder on the needle valve that is engageable with the spring cage to trap pressurized fuel in the spring cage during a fuel injection event;
- and
- a calibrated fuel vent in communication with the needle valve opening whereby pressurized fuel in the spring cage is discharged to a low pressure region of the injector when a fuel injection event is completed, the presence of pressurized fluid in the spring chamber reducing a tendency for cavitation to occur upon movement of the needle valve.
Dependencies are inferred from the claim text.