Apparatus and method for diagnosing and controlling an ignition system of an internal combustion engine

• US 6,408,242 B1
• Filed: 06/22/2000
• Issued: 06/18/2002
• Est. Priority Date: 12/11/1997
• Status: Expired due to Term

• Current Assignee: Cummins Incorporated
• Original Assignee: Cummins Incorporated
• Inventors: Tozzi, Luigi P.
• Primary Examiner(s): Kwon, John
• Assistant Examiner(s): Vo, Hieu T.
• Application Number:
  US09/599,248
• Time in Patent Office: 726 Days
• Field of Search: 701/114, 701/102, 701/115, 123/406.14, 123/597, 123/630, 123/406.65, 123/653, 324/399, 324/378, 324/380
• US Class Current: 701/114
• CPC Class Codes: F02D 2200/1015 Engines misfires
• CPC Class Codes: F02D 35/021 using an ionic current sensor
• CPC Class Codes: F02D 35/027 using knock sensors
• CPC Class Codes: F02D 41/1498 measuring engine roughness
• CPC Class Codes: F02P 17/12 Testing characteristics of the spark, ignition voltage or current testing of sparking plugs H01T13/60
• CPC Class Codes: F02P 2017/121 by measuring spark voltage
• CPC Class Codes: F02P 2017/125 Measuring ionisation of combustion gas, e.g. by using ignition circuits

Abstract

An apparatus for diagnosing and controlling an ignition system of an Internal combustion engine includes an ignition coil controllable by an ignition control circuit, a spark voltage sensor electrically connected to the high tension side of the ignition coil secondary and an ion voltage sensor electrically connected to the low tension side of the ignition coil secondary. A computed processes the ion voltage signal to determine a combustion quality value and a roughness value. If the combustion quality value is outside a predefined range or if the roughness value exceeds a roughness threshold, the computer is operable to adjust the engine fueling, spark timing and/or spark energy.

Claims

1. A system for detecting ignition system failures, comprising:

an ignition coil having a primary coil coupled to a secondary coil;

means for energizing said primary coil to thereby induce a spark voltage in a high tension side and an ion voltage in a low tension side of said secondary coil;

an ion sensor associated with said low tension side of said secondary coil, said ion sensor sensing said ion voltage and producing an ion voltage signal corresponding thereto; and

a computer having an input receiving said ion voltage signal, said computer analyzing said ion voltage signal and determining therefrom a combustion quality value associated with said spark voltage.

2. The system of claim 1 wherein said ion sensor is integral with said low tension side of said secondary coil.

3. The system of claim 2 wherein said ion sensor includes:

a resistor having one end connected to said low tension side of said secondary coil and an opposite end; and

a capacitor having one end thereof connected to said opposite end of said resistor and an opposite end providing said ion voltage signal.

4. The system of claim 1 wherein said ignition coil forms part of an internal combustion engine.

5. The system of claim 1 wherein said ion sensor includes:

a resistor having one end connected to said low tension side of said secondary coil and an opposite end; and

a capacitor having one end thereof connected to said opposite end of said resistor and an opposite end providing said ion voltage signal.

6. The system of claim 1 further including a spark plug connected to said secondary coil, said spark plug producing an ignition spark in response to said spark voltage.

7. Apparatus for diagnosing ignition system failures, comprising:

an ignition coil having a primary coil coupled to a secondary coil;

means for energizing said primary coil to thereby induce a spark voltage in a high tension side of said secondary coil and an ion voltage in a low tension side of said secondary coil;

a fueling system responsive to a fueling command signal to fuel an internal combustion engine;

a first computer providing said fueling command signal to said fueling system; and

a second computer having an input coupled to said low tension side of said secondary coil for receiving said ion voltage and a first output connected to said first computer, said second computer processing said ion voltage and determining a combustion quality value therefrom, said second computer comparing said combustion quality value with a first threshold value and providing a first fueling command correction signal at said first output if said combustion quality value exceeds said first threshold value, said first computer responsive to said first fueling command correction signal to alter said fueling command signal to thereby decrease fuel supplied to said engine.

8. The apparatus of claim 7 wherein said second computer is operable to compare said combustion quality value with a second threshold value and provide a second fueling command correction signal at said first output if said combustion quality value is less than said second threshold value, said first computer responsive to said second fueling command correction signal to alter said fueling command signal to thereby increase fuel supplied to said engine.

9. The apparatus of claim 8 wherein said means for energizing said primary coil includes an ignition control circuit having a first input receiving a firing command signal;

and wherein said first computer is operable to provide said firing command signal to said first input of said ignition control circuit.

10. The apparatus of claim 9 wherein said second computer includes a trigger input receiving said firing command signal, said second computer responsive to said firing command signal to process said ion voltage;

and wherein said second computer is responsive to a first occurrence of said firing command signal to provide said first and second fueling command correction signals.

11. The apparatus of claim 10 further including a spark plug connected to said high and low tension sides of said secondary coil and defining a spark gap therebetween, said spark voltage inducing a spark in said spark gap;

and wherein said second computer is responsive to a second occurrence of said firing command signal to provide a first spark timing correct-on signal if said combustion quality value exceeds said first threshold value, said first computer responsive to said first spark timing correction signal to alter timing of said firing command to thereby advance a time of energization of said primary coil.

12. The apparatus of claim 11 wherein said second computer is further responsive to said second occurrence of said firing command to provide a second spark timing correction signal if said combustion quality value is less than said second threshold value, said first computer responsive to said second spark timing correction signal to alter timing of said firing command to thereby retard a time of energization of said primary coil.

13. The apparatus of claim 12 wherein said second computer is responsive to a third occurrence of said firing command signal to provide a first spark energy correction signal if said combustion quality value exceeds said first threshold value, said ignition control circuit responsive to said first spark energy correction signal to increase a spark energy of said spark induced in said spark gap.

14. The apparatus of claim 13 wherein said second computer is further responsive to said third occurrence of said firing command to provide a second spark energy correction signal if said combustion quality value is less than said second threshold value, said first computer responsive to said second spark energy correction signal to reduce the spark energy of said spark induced in said spark gap.

15. The apparatus of claim 14 further including an ion voltage sensor associated with said low tension side of said secondary coil, said ion voltage sensor sensing said ion voltage and producing an ion voltage signal as a function of time, said ion voltage sensor providing said ion voltage signal to said input of said second computer.

16. The apparatus of claim 15 wherein said second computer is operable to determine said combustion quality value as an area under said ion voltage signal between two predetermined time points.

17. The apparatus of claim 16 wherein said second computer includes means for integrating said ion voltage signal between said two predetermined time points.

18. The apparatus of claim 8 wherein said second computer is further operable to compare said combustion quality value with a third threshold value and produce a misfire signal if said combustion quality value is less than said third threshold value.

19. The apparatus of claim 18 wherein said second computer includes a first memory;

and wherein said second computer is responsive to said misfire signal to store a misfire error code in said first memory.

20. The apparatus of claim 19 wherein said second computer is operable to provide said misfire signal at a diagnostics output thereof, and wherein said first computer includes a diagnostics input connected to said diagnostics output of said second computer;

and wherein said first computer is an engine control computer operable to control said internal combustion engine;

and further including means for extracting said misfire error code from said first memory via said engine control computer.

21. The apparatus of claim 18 wherein said second computer is operable to provide said misfire signal at a diagnostics output thereof, and wherein said first computer includes a diagnostics input connected to said diagnostics output of said second computer and a second memory, said first computer responsive to said misfire signal to store a misfire error code in said second memory.

22. The apparatus of claim 21 wherein said first computer is an engine control computer operable to control operation of said internal combustion engine;

and further including means for extracting said misfire error code from said second memory of said engine control computer.

23. Apparatus for diagnosing ignition system failures, comprising:

an ignition coil having a primary coil coupled to a secondary coil;

means for energizing said primary coil to thereby induce a spark voltage in a high tension side of said secondary coil and an ion voltage in a low tension side of said secondary coil;

a fueling system responsive to a fueling command signal to fuel an internal combustion engine;

a first computer providing said fueling command signal to said fueling system; and

a second computer having an input coupled to said low tension side of said secondary coil for receiving said ion voltage and a first output connected to said first computer, said second computer processing said ion voltage and determining a roughness value therefrom, said second computer comparing said roughness value with a roughness threshold and providing a fueling command correction signal at said first output if said roughness value exceeds said roughness threshold, said first computer responsive to said fueling command correction signal to alter said fueling command signal. to thereby decrease fuel supplied to said engine.

24. The apparatus of claim 23 wherein said means for energizing said primary coil includes an ignition control circuit having a first input receiving a firing command signal;

and wherein said first computer is operable to provide said firing command signal to said first input of said ignition control circuit.

25. The apparatus of claim 24 wherein said second computer includes a trigger input receiving said firing command signal, said second computer responsive to said firing command signal to process said ion voltage;

and wherein said second computer is responsive to a first occurrence of said firing command signal to provide said fueling command correction signal.

26. The apparatus of claim 25 further including a spark plug connected to said high and low tension sides of said secondary coil and defining a spark gap therebetween, said spark voltage inducing a spark in said spark gap;

and wherein said second computer is responsive to a second occurrence of said firing command signal to provide a spark timing correction signal if said roughness value exceeds said roughness threshold, said first computer responsive to said spark timing correction signal to alter timing of said firing command to thereby advance a time of energization of said primary coil.

27. The apparatus of claim 26 wherein said second computer is responsive to a third occurrence of said firing command signal to provide a spark energy correction signal if said roughness value exceeds said roughness threshold, said first computer responsive to said spark energy correction signal to alter timing of said firing command to thereby increase a spark energy of said spark induced in said spark gap.

28. The apparatus of claim 27 further including an ion voltage sensor associated with said low tension side of said secondary coil, said ion voltage sensor sensing said ion voltage and producing an ion voltage signal as a function of time, said ion voltage sensor providing said ion voltage signal to said input of said second computer.

29. The apparatus of claim 28 wherein said second computer is operable to determine said roughness value by analyzing frequency components of said ion voltage signal over a time range thereof after an occurrence of peak cylinder pressure, said second computer determining that said roughness value exceeds said roughness threshold if peak values of a number of said frequency components exceed a peak threshold.