Direct fuel injectors with variable injection flow rate

A direct fuel injection system for connection with a common rail for supplying fuel at a determined delivery pressure, the fuel injection system comprising:

• a fuel injector including an injector needle slidably disposed within a housing, the injector needle and the housing together providing a control chamber wherein the control chamber is fluidly connected with both a first control orifice within a connection with pressurized fuel from the common rail and a second control orifice within a connection with a drain line so that fluid pressure can be regulated within the control chamber by way of control of fluid flow through the first and second control orifices, a delivery chamber including a port for connection with the pressurized fuel from the common rail and an injection orifice from which fuel can be injected upon movement of the injector needle, and a feedback chamber being in fluid communication with at least one internal feedback spool valve that can be actuated by increased pressure within the feedback chamber to close the first and second control orifices of the control chamber based upon movement of the injector needle;
• a control valve fluidly within the drain line from the control chamber capable of selectively opening and closing the drain line to regulate fluid pressure within the control chamber;
• a feedback valve provided within a fluid line connected with the feedback chamber capable of selectively opening and closing the fluid line from the feedback chamber and for selectively controlling activation of the at least one internal feedback spool valve;
• and
• a control module for selectively activating the control valve and the feedback valve during a fuel injection cycle, wherein the control valve and the feedback valve can be varied on a cycle-by-cycle basis.

A method of flow rate estimation and iterative learning control for timing of activation of a control valve and a feed back valve so that the feedback valve can be controlled and adjusted on a cycle by cycle basis in order to achieve a desired fuel flow rates from an injector of a direct fuel injection system, the injector comprising an injector needle slidably disposed within a housing, the injector needle and the housing together providing a control chamber wherein the control chamber is fluidly connected with both a first control orifice within a connection with pressurized fuel from the common rail and a second control orifice within a connection with a drain line so that fluid pressure can be regulated within the control chamber by way of control of fluid flow through the first and second control orifices, a delivery chamber including a port for connection with the pressurized fuel from the common rail and an injection orifice from which fuel can be injected upon movement of the injector needle, and a feedback chamber being in fluid communication with at least one internal feedback spool valve that can be actuated by increased pressure within the feedback chamber to close the first and second control orifices of the control chamber based upon movement of the injector needle, the method comprising the steps of:

• estimating the flow rate of the injector based on the measurement of the common rail pressure, the activation timing of the control valve and the activation timing of the feedback valve;
• and
• iteratively controlling the period between activation timing of the control valve and the feedback valve on an injection cycle by cycle basis by way of an iterative learning control of a control module that is electronically connected with the control valve and the feedback valve for controlled activation of the control valve and the feedback valve.