Fuel injector with directly controlled highly efficient nozzle assembly and fuel system using same

摘要

Reducing leakage within fuel injectors is one way in which the efficiency of the overall fuel injection system can be improved. In most fuel injectors that include a direct control needle valve, the needle valve member is still biased toward a closed position by a spring that is located in a spring chamber connected to a low pressure vent. In many instances, the needle valve member is guided in a tight clearance region adjacent the spring chamber. Since the internal plumbing of the fuel injector is connected to a high pressure rail during and between injection events, static leakage across the guide region of the needle valve member can reduce efficiency. Static leakage is reduced in the present invention by connecting the spring chamber (48) to the common rail (14) instead of to a low pressure vent. Such a fuel injector could find potential application in any directly controlled fuel injection system (12), but is particularly applicable in common rail systems in which the fuel injector (16) remains fully pressurized between injection events.