Patent ID: 6811092
Filing Date: 2004-11-02
Classification: F02M

Abstract:
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.