Electroinjector for controlling fuel injection in an internal-combustion engine

Abstract

An electroinjector is provided for controlling fuel injection in an internal-combustion engine. The electroinjector includes an electroactuator, an injection nozzle, and a pin, which is movable along an opening stroke and a closing stroke for opening/closing the nozzle under the control of the electroactuator and according to the supply pressure of the fuel into the electroinjector. A first electrical command and at least a second electrical command, which are sufficiently close to one another as to displace the pin with a profile of motion without any discontinuity in time, and such as to cause the pin to perform a first opening displacement and, respectively, a second opening displacement, are supplied to the electroactuator. Between one injection and the next, at least one among the following quantities is varied as a function of operating parameters of the engine: duration of at least one among the electrical commands; number of the electrical commands; and distance in time between the electrical commands.

The invention claimed is: 
     
       1. An electroinjector provided to control fuel injection in an internal combustion engine comprising:
 an electroactuator having a solenoid operable by electrical commands to control a metering valve, 
 an injection nozzle, and 
 a pin which is movable so as to open and close the nozzle under control of the metering valve, 
 wherein the solenoid is driven by a first electrical command with a first maximum command value and a second electrical command, supplied before the first electrical command reaches zero, with a second maximum command value, each of said first and second electric commands including an intermediate and constant command value below the first and second maximum command values, said electric commands having a duration as to displace the pin into first and second opening positions without any discontinuity in time, said opening positions defining corresponding degrees of opening of said injection nozzle, and 
 wherein said second command is supplied so as to start displacement of the pin into said second opening position when said pin is closing the injection nozzle. 
 
     
     
       2. The electroinjector according to  claim 1 , wherein said second degree of opening is greater than said first degree of opening. 
     
     
       3. The electroinjector according to  claim 1 , wherein the first electrical command also has an intermediate and constant command value below the first and second maximum command values. 
     
     
       4. The electroinjector according to  claim 3 , wherein said intermediate and constant command value of the first electrical command is disposed between the maximum command values of said first and second electrical commands. 
     
     
       5. The electroinjector according to  claim 1 , wherein, after a fuel injection, at least one of a duration of one of the electrical commands, a number of the electrical commands, and a time between the electrical commands is varied as a function of engine load prior to another fuel injection. 
     
     
       6. The electroinjector according to  claim 2 , wherein, after a fuel injection, at least one of a duration of one of the electrical commands, a number of the electrical commands, and a time between the electrical commands is varied as a function of engine load prior to another fuel injection. 
     
     
       7. The electroinjector according to  claim 3 , wherein, after a fuel injection, at least one of a duration of one of the electrical commands, a number of the electrical commands, and a time between the electrical commands is varied as a function of engine load prior to another fuel injection. 
     
     
       8. The electroinjector according to  claim 4 , wherein, after a fuel injection, at least one of a duration of one of the electrical commands, a number of the electrical commands, and a time between the electrical commands is varied as a function of engine load prior to another fuel injection. 
     
     
       9. An electroinjector provided to control fuel injection in an internal-combustion engine comprising:
 an electroactuator having a solenoid driven by electrical commands to control a metering valve; and 
 an atomizer, the atomizer comprising an injection nozzle and a pin, which is movable along an opening stroke and a closing stroke for opening/closing said nozzle under the control of said metering valve, the electroinjector performing dosage of the fuel by modulating in time opening of the pin of the atomizer according to the pressure of supply of the electroinjector itself; 
 wherein the solenoid is driven by at least one first electrical command with at least one first maximum command value and a second electrical command with a second maximum command value, each of said first and second electric commands including an intermediate and constant command value below the first and second maximum command values, said electric commands having a duration as to displace said pin with a profile of motion without any discontinuity in time, said commands providing opening positions defining corresponding degrees of opening of said injection nozzle; 
 wherein said pin performs a first opening displacement and a second opening displacement respectively based on the commands supplied; 
 wherein said pin performs a third opening displacement in succession to said first and second opening displacements; and 
 wherein said second electric command is supplied so as to start the second opening displacement of the pin when the pin is closing the injection nozzle. 
 
     
     
       10. The electroinjector according to  claim 9 , wherein electrical commands are supplied in such a way as to cause, at the end of said opening displacements, a first degree, a second degree, and a third degree of opening to be reached, and wherein said first and second degrees of opening are smaller than said third degree of opening. 
     
     
       11. The electroinjector according to  claim 10 , wherein said at least one first maximum command value includes plural values occurring consecutively with respect to one another and prior to said second maximum command value. 
     
     
       12. The electroinjector according to  claim 10 , wherein said electrical commands are supplied in such a way that said first and second degrees of opening are equal to one another. 
     
     
       13. An electroinjector provided to control fuel injection in an internal-combustion engine comprising:
 an electroactuator; 
 an atomizer having an injection nozzle supplied with fuel at high pressure; and 
 a pin displaceable axially for opening and closing the nozzle so that the instantaneous fuel flow rate is determined by the axial displacement of the pin; 
 wherein said pin is movable along opening strokes and relevant closing strokes under control of said electroactuator; 
 wherein electric commands are modulated in time for operating said electroactuator with a dosage according to the pressure of supplied fuel, each of the electric commands including a maximum holding stretch at a maximum value and intermediate holding stretch at an intermediate value; 
 wherein a first of the electric commands has a predetermined duration of said intermediate holding stretch to cause said pin to perform a first opening stroke reaching a first maximum value; 
 wherein at least a second of the electric commands has a corresponding duration of said intermediate stretch to cause said pin to perform a second opening stroke reaching a second maximum value greater than said first maximum value; and 
 wherein the second electric command is supplied at an instant so as to start the second opening stroke not later than the instant at which the pin terminates the first closing stroke. 
 
     
     
       14. The electroinjector according to  claim 13 , wherein said second electric command is supplied at an instant not later than when said first electrical command reaches zero to start said second opening stroke when said pin is displacing along the first closing stroke. 
     
     
       15. The electroinjector according to  claim 13 , wherein said modulation in time is determined as a function of operating parameters of said engine by varying at least one of a duration of at least one of the electric commands, and a distance in time between said first electric command and said second electric command. 
     
     
       16. The electroinjector according to  claim 13 , wherein at least a third electrical command sufficiently close to said first and second electrical commands is supplied to said electroactuator so as to displace said pin with a profile of motion so as to cause the pin to perform a third opening stroke in succession between said first opening stroke and said second opening stroke to start said second and third opening strokes when said pin is displacing respectively along the first and second closing strokes. 
     
     
       17. The electromagnet according to  claim 16 , wherein said third electrical command is supplied in such a way as to cause, at the end of the third opening stroke, a third maximum value of opening smaller than the maximum value of said second opening stroke. 
     
     
       18. The electroinjector according to  claim 17 , wherein said first electrical command and said third electrical command are supplied in such a way that said first maximum value of opening and said third maximum value of opening are equal to one another. 
     
     
       19. An electroinjector provided to control fuel injection in an internal-combustion engine comprising:
 an electroactuator; 
 an atomizer having an injection nozzle supplied with fuel at high pressure; and 
 a pin displaceable axially for opening and closing said nozzle so that the instantaneous fuel flow rate is determined by the axial displacement of said pin; 
 wherein said pin is movable along opening strokes and relevant closing strokes under control of said electroactuator; 
 wherein electric commands are modulated in time for operating said electroactuator with a dosage according to pressure of supplied fuel, each of said electric commands including a maximum holding stretch at a maximum value and an intermediate holding stretch at an intermediate value; 
 wherein a first of said electric commands has a predetermined duration of said intermediate holding stretch to cause said pin to perform a first opening stroke reaching a first maximum value; 
 wherein at least a second of said electric commands has a corresponding duration of said intermediate stretch to cause said pin to perform a second opening stroke reaching a second maximum value greater than said first maximum value; 
 wherein said second electric command is supplied at an instant before said first electrical command reaches zero so as to start said second opening stroke when said pin is displacing along the first closing stroke; and 
 wherein the time modulation is determined as a function of operating parameters of said engine by varying at least one of a duration of at least one of the electric commands and a distance in time between the first electric command and the second electric command. 
 
     
     
       20. The electroinjector according to  claim 19 , wherein at least a third electrical command sufficiently close to said first and second electrical commands is supplied to said electroactuator so as to displace said pin with a profile of motion so as to cause the pin to perform a third opening stroke in succession between said first opening stroke and said second opening stroke to start said second and third opening strokes when said pin is displacing respectively along the first and second closing strokes. 
     
     
       21. The electromagnet according to  claim 19 , wherein said third electrical command is supplied in such a way as to cause, at the end of the third opening stroke, a third maximum value of opening smaller than the maximum value of said second opening stroke. 
     
     
       22. The electroinjector according to  claim 21 , wherein said first electrical command and said third electrical command are supplied in such a way that said first maximum value of opening and said third maximum value of opening are equal to one another. 
     
     
       23. A fuel electroinjector for a fuel injection system for an internal combustion engine, the fuel electroinjector being operable by a first electrical command and a subsequent second electrical command to respectively cause the fuel electroinjector to perform a pilot fuel injection and a main fuel injection in an engine cylinder, wherein the first and second electrical commands are spaced apart in time by an electrical dwell time, and the main fuel injection starts without interruption with respect to the pilot fuel injection when the pilot fuel injection ends.  
     
     
       24. The fuel electroinjector according to claim 23, wherein the main fuel injection starts exactly when the pilot fuel injection ends.  
     
     
       25. The fuel electroinjector according to claim 23, wherein a main quantity of fuel injected during the main fuel injection differs from a pilot quantity of fuel injected during the pilot fuel injection.  
     
     
       26. The fuel electroinjector according to claim 25, wherein the main quantity of fuel is larger than the pilot quantity of fuel.  
     
     
       27. The fuel electroinjector according to claim 23, further comprising:
 a fuel atomizer having a fuel injection nozzle, and a pin movable along opening and closing strokes to open and close the fuel injection nozzle; and   an electrically-operable fuel metering servo valve operable to control the fuel atomizer by the first electrical command;   wherein the electroactuator is operable by the first electrical command to cause the fuel atomizer pin to perform a first opening displacement for the pilot fuel injection followed by a first closing displacement, ending when the fuel atomizer pin closes the fuel injection nozzle, so as to result in a first opening degree of the fuel injection nozzle, and by the second electrical command to cause the atomizer pin to perform a second opening displacement for the main fuel injection followed by a second closing displacement so as to result in a second opening degree of the fuel injection nozzle; and   wherein the second opening displacement starts at an end of the first closing displacement so as to result in a motion profile without interruption between the first closing displacement and the second opening displacement.    
     
     
       28. The fuel electroinjector according to claim 27, wherein the first opening degree differs from the second opening degree.  
     
     
       29. The fuel electroinjector according to claim 28, wherein the first opening degree is lower than the second opening degree.  
     
     
       30. The fuel electroinjector according to claim 23, wherein each of the electrical commands is an electrical current that changes with respect to time so as to define a curve having a trailing edge rising from a minimum value to a maximum value, a stretch holding at said maximum value, and a forward edge falling from the intermediate value toward said minimum value.  
     
     
       31. The fuel electroinjector according to claim 30, wherein said curve further has another forward edge falling from the maximum value to an intermediate value, and another holding stretch holding at said intermediate value.  
     
     
       32. The fuel electroinjector according to claim 23, wherein the fuel injection system is a common rail fuel injection system.  
     
     
       33. A fuel injection system for an internal combustion engine having a fuel electroinjector comprising:
 a fuel electroinjector, and   an electronic control unit to supply the fuel electroinjector with a first electrical command and a second electrical command to respectively cause the fuel electroinjector to perform a pilot fuel injection and a main fuel injection in an engine cylinder,   wherein the first and second electrical commands are spaced apart in time by an electrical dwell time, and the main fuel injection starts without interruption with respect to the pilot fuel injection when the pilot fuel injection ends.    
     
     
       34. The fuel injection system according to claim 33, wherein the main fuel injection starts exactly when the pilot fuel injection ends.  
     
     
       35. The fuel injection system according to claim 33, wherein a main quantity of fuel injected during the main fuel injection differs from a pilot quantity of fuel injected during the pilot fuel injection.  
     
     
       36. The fuel injection system according to claim 35, wherein the main quantity of fuel is larger than the pilot quantity of fuel.  
     
     
       37. The fuel injection system according to claim 33, further comprising:
 a fuel atomizer having a fuel injection nozzle, and a pin movable along opening and closing strokes to open and close the fuel injection nozzle; and   an electrically-operable fuel metering servo valve operable to control the fuel atomizer by the first electrical command;   wherein the electroactuator is operable by the first electrical command to cause the fuel atomizer pin to perform a first opening displacement for the pilot fuel injection followed by a first closing displacement, ending when the fuel atomizer pin closes the fuel injection nozzle, so as to result in a first opening degree of the fuel injection nozzle, and by the second electrical command to cause the atomizer pin to perform a second opening displacement for the main fuel injection followed by a second closing displacement so as to result in a second opening degree of the fuel injection nozzle; and   wherein the second opening displacement starts at an end of the first closing displacement so as to result in a motion profile without interruption between the first closing displacement and the second opening displacement.    
     
     
       38. The fuel injection system according to claim 37, wherein the first opening degree differs from the second opening degree.  
     
     
       39. The fuel injection system according to claim 38, wherein the first opening degree is lower than the second opening degree.  
     
     
       40. The fuel injection system according to claim 33, wherein each of the electrical commands is an electrical current that changes with respect to time so as to define a curve having a trailing edge rising from a minimum value to a maximum value, a stretch holding at said maximum value, and a forward edge falling from the intermediate value toward said minimum value.  
     
     
       41. The fuel injection system according to claim 33, wherein said curve further has another forward edge falling from the maximum value to an intermediate value, and another holding stretch holding at said intermediate value.  
     
     
       42. The fuel injection system according to claim 33, wherein the fuel injection system is a common rail fuel injection system.