Method and apparatus for delivering multiple fuel injections to the cylinder of an internal combustion engine

Abstract

A fuel injection control system and method for delivering multiple fuel injections to a cylinder of an engine during a fuel injection event based upon engine operating conditions, the control system including an electronic controller coupled to an electrically controlled fuel injector, and a plurality of sensors coupled to the controller for inputting certain signals representative of certain engine operating conditions of the engine, the controller being operable to output a fuel injection signal to the fuel injector to deliver a first, a second, and a third fuel shot to the cylinder during a fuel injection event based upon the sensor signals. The controller also delivers each of the multiple fuel injection shots within defined cylinder piston displacement parameters during a particular piston stroke, within defined fuel apportionment limits, and within defined delay limits between each respective fuel shot so as to control exhaust emissions.

1. A method for delivering a first and second fuel shot to a cylinder of a compression ignition engine during a particular fuel injection event wherein the injection to the cylinder is provided by an electronically controlled fuel injector, the method comprising the steps of:
 providing an electronic controller coupling said controller to the fuel injector;  
 sensing an engine speed of the compression ignition engine;  
 determining a total fuel quantity to be delivered during injection as a function of at least the sensed engine speed and an engine load of the compression ignition engine;  
 determining the first fuel shot quantity to be delivered during injection;  
 determining the second fuel shot quantity to be delivered during injection; and  
 initiatingcompleting the delivery of the first fuel shot duringbefore an end of a compression stroke of the compression ignition engine;  
 mixing the first fuel shot with air into a mixture in the cylinder before combusting the first fuel shot; and  
   compression igniting the mixture during the compression stroke.    
 
     
     
       2. The method as set forth in  claim 1  including the step of determining a third fuel shot quantity to be delivered during injection. 
     
     
       3. The method as set forth in  claim 2  wherein initiation of the delivery of the first fuel shot occurs when the cylinder piston of the compression ignition engine is displaced between a range from approximately 75° to approximately 35° before top dead center during a compression stroke of e compression ignition engine. 
     
     
       4. The method as set forth in  claim 3  including the step of initiating the delivery of the second fuel shot when the cylinder piston of the compression ignition engine is displaced between a range from approximately 30° before top dead center to approximately 15° after top dead center during a compression stroke of the compression ignition engine. 
     
     
       5. The method as set forth in  claim 4  including the step of initiating the delivery of the third fuel shot when the cylinder piston of the compression ignition engine is displaced between a range from approximately 18° before top dead center to approximately 18° after top dead center during a compression stroke of the compression ignition engine. 
     
     
       6. The method as set forth in  claim 2  including the step of initiating the delivery of the first fuel shot approximately 3 to 8 millisecond in advance of the second fuel shot. 
     
     
       7. The method as set forth in  claim 2  including the step of initiating the delivery of the third fuel shot approximately 0.20 to 0.75 milliseconds after the second fuel shot. 
     
     
       8. The method as set forth in  claim 2  wherein the first fuel shot includes approximately 5% to 40% of the total fuel quantity to be delivered during injection, and wherein said second fuel shot includes approximately 3% to 0% of the total fuel quantity to be delivered during injection. 
     
     
       9. The method as set forth in  claim 8  including the step of sensing the ambient conditions under which the compression ignition engine is operating;
 said controller being operable to adjust the timing and/or fuel quantity associated with each of said first, second and third fuel shots and/or the delays there between based upon said ambient conditions.  
 
     
     
       10. The method as set forth in  claim 2  wherein said first, second, and third fuel shots are delivered at engine loads of approximately 30% or greater of rated engine load at all engine speeds. 
     
     
       11. The method as set forth in  claim 2  including the step of sensing a rail pressure associated with an injector actuating fluid and using e sensed rail pressure as an engine load indicator in determining the first, second, and third fuel shot quantities. 
     
     
       12. The method as set forth in  claim 2  including the step of using the total fuel quantity as an engine load indicator in determining the first, second, and third fuel shot quantities. 
     
     
       13. The method as set forth in  claim 2  wherein delivery of said second and third fuel shots are rate shaped. 
     
     
       14. The method as set forth in  claim 2  wherein said third fuel shot quantity is determined as a difference between the total fuel quantity to be delivered during a particular injection event and the sum of the first and second fuel shot quantities. 
     
     
       15. The method as set forth in  claim 2  wherein the first fuel shot quantity is sufficient for a compression ignition to occur before delivery of the second fuel shot. 
     
     
       16. The method as set forth in  claim 2  wherein the first fuel shot quantity is greater than the second fuel shot quantity but less than the third fuel shot quantity. 
     
     
       17. A method of operating an electronically controlled fuel injector, comprising the steps of:
 sequentially supplying first, second and third shot control signals to the electronically controlled fuel injector;  
 separating the second and third shot control signals with an anchor delay; and  
 setting the anchor delay such that fuel injected due to the second shot control signal is indistinct from fuel injected due to the third shot control signal in that an injection rate remains greater than zero from a beginning of fuel injection from the second control signal through to an end of fuel injection from the third shot control signal;  
 mixing the first fuel shot with air into a mixture in the cylinder before combusting the first fuel shot; and  
   compression igniting the mixture during a compression stroke.    
 
     
     
       18. The method of  claim 17  including the steps of:
 separating the first and second shot control signals with a main delay; and  
 setting the main delay such that fuel injected due to the first shot control signal is distinct from fuel injected due to the second and third shot control signals.  
 
     
     
       19. The method of  claim 17  wherein the first, second and third shot control signals include distinct electric current signals. 
     
     
       20. A method of operating an electronically controlled fuel injector, comprising the steps of:
 sequentially supplying first, second and third shot control signals to the electronically controlled fuel injector;  
 separating the second and third shot control signals with an anchor delay;  
 setting the anchor delay such that fuel injected due to the second shot control signal is indistinct from fuel injected due to the third shot control signal; and  
 wherein the fuel injector is positioned for direct injection into a cylinder of a compression ignition engine;  
 mixing the first fuel shot with air into a mixture in the cylinder before combusting the first fuel shot; and  
   compression igniting the mixture during a compression stroke.    
 
     
     
       21. The method of  claim 20  including the steps of:
 separating the first and second shot control signals with a main delay; and  
 setting the main delay such that fuel injected due to the first shot control signal is distinct from fuel injected due to the second and third shot control signals.  
 
     
     
       22. The method of  claim 21  wherein the first, second and third shot control signals include distinct electric current signals. 
     
     
       23. A method of operating an internal combustion engine, comprising the steps of:
   allocating a quantity of fuel among an early medium pilot quantity of fuel, a small main quantity of fuel and a large anchor quantity of fuel to be delivered directly to a cylinder, and the early medium pilot quantity being greater than the small main quantity but less than the large anchor quantity;        issuing a control waveform to a fuel injector, wherein the control waveform includes, in sequence, a pilot portion corresponding to the early medium pilot quantity, a main portion corresponding to the small main quantity of fuel and an anchor portion corresponding to the large anchor quantity of fuel;        mixing the early medium pilot quantity of fuel with air into a mixture in the cylinder before combusting the early medium pilot quantity of fuel; and        compression igniting the mixture during a compression stroke.     
     
     
       24. The method of  claim 23  wherein the early medium pilot quantity is from  5 %  to  40   % , the small main quantity is from  3   %  to  40   % , and the large anchor quantity is a remaining percentage.   
     
     
       25. The method of  claim 24  wherein the main portion of the control waveform is issued after combustion of the early medium pilot quantity of fuel. 
     
     
       26. The method of  claim 25  wherein the compression igniting step begins in a range from  20  degrees to  12  degrees before top dead center of the compression stroke. 
     
     
       27. The method of  claim 25  including a step of increasing injection pressure after issuing the pilot portion of the control waveform but before issuing the main portion of the control waveform. 
     
     
       28. The method of  claim 27  wherein the step of increasing injection pressure is accomplished by raising a rail pressure. 
     
     
       29. The method of  claim 25  wherein the allocating step includes the early medium pilot quantity being from  15 %  to  25   % , the small main quantity being from  5   %  to  10   % , and the large anchor quantity being from  60   %  to  80   % .   
     
     
       30. The method of  claim 23  including the steps of:
   injecting a pilot shot, which corresponds to the early medium pilot quantity, from the injector into the cylinder in response to issuing the pilot portion of the control waveform.     
     
     
       31. The method of  claim 23  including a step of separating the main portion of the control waveform from the anchor portion of the control waveform with an anchor delay that is insufficient to produce a distinct main shot and a distinct anchor shot from the fuel injector. 
     
     
       32. The method of  claim 23  wherein the pilot portion of the control waveform is issued during the compression stroke of the cylinder. 
     
     
       33. The method of  claim 23  including a step of separating the main portion of the control waveform from the anchor portion of the control waveform with an anchor delay;
   setting the anchor delay based upon engine speed and load.     
     
     
       34. The method of  claim 23  including a step of dynamically determining the control waveform based upon engine speed and load.