Patent ID: 7150410
Filing Date: 2006-12-19
Classification: F02D,F02M,Y02T

Abstract:
1. A method for controlling injection rate and injection pressure of a liquid fuel injector having a nozzle assembly and an injector plunger in an injector cylinder for developing nozzle assembly injection pressure, a pressure balanced control valve assembly including a valve body with a valve bore defining a valve seat, a movable valve element in the valve bore with a valve head on the movable valve element, the valve head and the valve seat defining a liquid fuel flow opening, the movable valve element communicating with a pressure regulated nozzle passage whereby the valve element is subject to injection pressure developed by the fuel injector plunger when it is stroked during an injection event, the valve seat and the valve head defining in part a fluid pressure spill passage communicating with the pressure regulated nozzle passage, the spill passage communicating with a fluid supply passage whereby the injector cylinder is supplied with liquid fuel when the fuel injection plunger is retracted, a solenoid actuator for the movable valve element, the valve seat and the valve head being normally open with the solenoid de-energized, and a spring acting on the valve element to oppose a solenoid actuator force; the method comprising the steps of: providing a first level of regulated current to the solenoid actuator to activate the movable valve element causing the valve head to move toward the valve seat to a first pressure regulating position defining a reduced liquid fuel flow opening whereby the spill flow passage has a first degree of fuel flow restriction thereby allowing regulated injection pressure in the nozzle assembly to rise and creating an initial liquid fuel injection pulse in an initial injection rate-controlled fuel injection period; providing a second reduced level of regulated current to the solenoid actuator for a preselected time following the initial liquid fuel injection pulse during an injection event to move the valve head away from the valve seat to a second pressure regulating position and to define an increased liquid fuel flow opening thereby creating a reduced initial injection pressure during the initial injection rate-controlled period; and providing a third level of regulated current at a value to cause the valve head to move toward the valve seat to a third pressure regulating position to define a decreased liquid fuel flow opening thereby creating a high third injection pressure regulating position that allows regulated injection pressure in the nozzle assembly to rise further during a main injector rate-controlled fuel injection period and to create a peak injection pressure pulse near the end of the injection event.