System and method for detecting engine cylinder misfire

• US 6,243,641 B1
• Filed: 10/19/1998
• Issued: 06/05/2001
• Est. Priority Date: 06/07/1995
• Status: Expired due to Term

• Current Assignee: Cummins Engine Company Incorporated (Cummins Incorporated)
• Original Assignee: Cummins Engine Company Incorporated (Cummins Incorporated)
• Inventors: Andrews, Eric B., Stepper, Mark R., zur Loye, Axel O.
• Primary Examiner(s): DOMBROSKE, GEORGE M
• Application Number:
  US09/174,548
• Time in Patent Office: 960 Days
• Field of Search: 701/101, 701/102, 701/110, 701/111, 731/15, 731/16, 731/173, 123/436
• US Class Current: 701/102
• CPC Class Codes: F02D 2200/021 Engine temperature
• CPC Class Codes: F02D 2200/0614 Actual fuel mass or fuel injection amount
• CPC Class Codes: F02D 2200/101 Engine speed
• CPC Class Codes: F02D 2200/1015 Engines misfires
• CPC Class Codes: F02D 41/1448 the characteristics being an exhaust gas pressure
• CPC Class Codes: F02D 41/30 Controlling fuel injection F02D41/182, F02D41/24 take precedence
• CPC Class Codes: G01M 15/08 by monitoring pressure in cylinders
• CPC Class Codes: G01M 15/09 by monitoring pressure in fluid ducts, e.g. in lubrication or cooling parts
• CPC Class Codes: G01M 15/106 using pressure sensors
• CPC Class Codes: G01M 15/11 by detecting misfire

Abstract

A system and method in which the exhaust manifold pressure is measured by a single gauge-type pressure sensor positioned in the exhaust manifold to detect misfires in all cylinders of an internal combustion engine. The pressure sensor detects the exhaust manifold pressure and feeds a signal to a microcomputer via an analog-to-digital converter. A data processing device monitors the pressure waveform created by the data from the sensor to determine if a full or partial misfire occurs. If a cylinder suffers from a partial or complete misfire, the strength of the pressure pulse for that cylinder will be reduced, thus, allowing the data processing device to identify the misfire. The data processing device may determine a misfire by computing an average peak pressure for each combustion cycle, a pressure threshold as a function of engine speed and fuel consumption rate, and a minimum pressure value based on the difference between the average peak pressure and the pressure threshold. The data processing device may alternatively determine a misfire by first computing a coefficient of variation between an observed pressure pulse and the average peak pressure and then comparing the coefficient of variation with a pressure threshold to determine if at least a partial misfire has occurred.

Claims

1. A system for detecting an engine cylinder misfire in an internal combustion engine comprising:

pressure sensing means mounted in an exhaust manifold of the internal combustion engine for sensing the peak pressure of the exhaust gas flowing through said exhaust manifold;

engine operation detecting means for detecting operating characteristics of the internal combustion engine, said operating characteristics including at least one of the rotational speed, fuel consumption rate and coolant temperature of the internal combustion engine; and

data processing means connected with said engine operation detecting means and said pressure sensing means for receiving the sensed pressure from said pressure sensing means for calculating a minimum pressure value based on the values of said operating characteristics measured by said engine operation detection means and for comparing said sensed pressure with said minimum pressure value to determine if an engine cylinder misfire has occurred.

2. The system of claim 1 wherein said engine operation detecting means includes a sensing means for monitoring and sensing said operating characteristics in real-time.

3. The system of claim 1 wherein said data processing means includes a memory means for storing data sensed from said pressure sensing means and said engine operating detecting means.

4. The system of claim 1 wherein said data processing means includes an average exhaust pressure calculating means for calculating the average exhaust pressure sensed by said pressure sensing means for each cylinder of said internal combustion engine during a complete combustion cycle.

5. The system of claim 4 wherein said data processing means includes a minimum pressure value calculating means for calculating a minimum pressure value by first calculating a pressure threshold using said detected operating characteristics of the internal combustion engine and subtracting said pressure threshold from said average exhaust pressure to yield said minimum pressure value.

6. The system of claim 4 wherein said data processing means includes a running average calculating means which averages an average exhaust pressure value determined by said average exhaust pressure calculating means and a current exhaust pressure value to yield a running average exhaust pressure value, said running average exhaust pressure value replacing said average exhaust pressure value after each cylinder firing.

7. The system of claim 1 wherein said pressure sensing means includes a peak pressure sensing means for sensing the highest pressure released from each cylinder of said internal combustion engine during each combustion cycle.

8. The system of claim 1 further comprising analog-to-digital converter means connected with said pressure sensing means and said data processing means for receiving an analog electrical signal representative of the pressure in said exhaust path from said pressure sensing means, for converting said analog electrical signal to a digital signal, and for providing said digital signal to said data processing means.

9. The system of claim 8 further comprising a peak detection means connected with said analog-to-digital converter means for receiving said digital signal and for determining the maximum sensed pressure based on said digital signal for each cylinder of the internal combustion engine during a normal combustion cycle.

10. The system of claim 1, wherein said pressure sensing means is a gauge-type pressure sensor.

11. The system of claim 10, wherein said gauge-type pressure sensor is a piezoelectric sensor.

12. The system of claim 10, wherein said gauge-type pressure sensor is a capacitive ceramic sensor.

13. The system of claim 1, wherein said pressure sensing means includes a single pressure sensor.

14. The system of claim 1, wherein said data processing means includes a cylinder number detecting means for detecting which cylinder has fired or misfired during a combustion cycle.

15. A method of detecting an engine cylinder misfire in an internal combustion engine comprising the steps of:

detecting the exhaust gas pressure generated by the internal combustion engine;

detecting operating characteristics of the internal combustion engine, said operating characteristics including at least one of the rotational speed, fuel consumption rate and coolant temperature of the internal combustion engine;

calculating a minimum pressure value corresponding to said operating characteristics;

comparing said minimum pressure value to the exhaust gas pressure; and

generating a signal indicating if said exhaust gas pressure is less than said minimum pressure value to declare the occurrence of an engine cylinder misfire.

16. The method of claim 15, wherein said step of calculating the minimum pressure value includes the step of calculating an average exhaust pressure for a complete combustion cycle and the step of calculating a pressure threshold using said operating characteristics of the internal combustion engine and subtracting the pressure threshold from said average exhaust gas pressure to yield said minimum pressure value.

17. The method of claim 15 further comprising the step of detecting an engine cylinder number for determining which cylinder has fired or misfired during a combustion cycle.

18. The method of claim 15 further comprising the step of detecting an air/fuel ratio for determining the air to fuel mixture entering each cylinder during a combustion cycle.

19. A method of detecting an engine cylinder misfire in an internal combustion engine to determine an optimal level of engine operation comprising the steps of:

decreasing the amount of fuel supplied to one or more cylinders of an internal combustion engine to cause an engine cylinder misfire;

detecting said engine cylinder misfire in said internal combustion engine caused by an insufficient supply of said fuel by calculating a minimum pressure value corresponding to at least one of the rotational speed, fuel consumption rate and coolant temperature of the internal combustion engine and comparing said minimum pressure value to a measured exhaust gas pressure;

generating a signal indicating if said exhaust gas pressure is less than said minimum pressure value to declare the occurrence of an engine cylinder misfire; and

increasing said amount of fuel supplied to said one or more cylinders in response to said detected misfire to a level sufficient to enable said internal combustion engine to operate without the occurrence of engine cylinder misfires at an optimal fuel efficiency.

20. A system for detecting an engine cylinder misfire in an internal combustion engine comprising:

a pressure sensor mounted in an exhaust manifold of the internal combustion engine;

engine operation sensors positioned on or within the internal combustion engine for detecting the operating characteristics of the internal combustion engine, said operating characteristics including at least one of the rotational speed, fuel consumption rate and coolant temperature of the internal combustion engine; and

a processor connected with said engine operation sensors and said pressure sensor for calculating a minimum pressure value to determine if an engine misfire has occurred, said processor comprising a comparison means for comparing the exhaust pressure sensed by said pressure sensor to said minimum pressure value to determine if an engine cylinder misfire has occurred.

21. The system of claim 20 wherein said pressure sensor is positioned in a passage which connects at least two of said exhaust paths of said internal combustion engine.

22. The system of claim 21 wherein said passage includes inlets at the ends of said passage, said inlets being smaller in diameter than the center area of said passage to restrict leakage of exhaust gases between said exhaust paths.

23. The system of claim 21 wherein said pressure sensor is offset from the center of said passage to prevent standing waves which may be generated within said passage.

24. The system of claim 20 further comprising an analog-to-digital converter connected with said pressure sensor and said processor for receiving an analog electrical signal representative of the pressure in said exhaust path from said pressure sensor, for converting said analog electrical signal to a digital signal, and for providing said digital signal to said processor.

25. The system of claim 20, wherein said pressure sensor is a gauge-type pressure sensor.

26. The system of claim 25, wherein said gauge-type pressure sensor is a piezoelectric sensor.

27. The system of claim 25, wherein said gauge-type pressure sensor is a capacitive ceramic sensor.

28. A system for detecting a partial or complete engine cylinder misfire in an internal combustion engine comprising:

pressure sensing means mounted in an exhaust manifold of the internal combustion engine for sensing the peak pressure of the exhaust gas flowing through said exhaust manifold;

engine operation detecting means for detecting operating characteristics of the internal combustion engine, said operating characteristics including at least one of the rotational speed, fuel consumption rate and coolant temperature of the internal combustion engine;

data processing means connected with said engine operation detecting means and said pressure sensing means for receiving the sensed pressure from said pressure sensing means, for converting said sensed pressure into a cylinder exhaust value, for calculating an optimum threshold based on the values of said operating characteristics measured by said engine operation detection means and for comparing said cylinder exhaust value with said optimum threshold to determine if a partial or complete engine cylinder misfire has occurred.

29. The system of claim 28 further comprising analog-to-digital converter means connected with said pressure sensing means and said data processing means for receiving an analog electrical signal representative of the pressure in said exhaust path from said pressure sensing means, for converting said analog electrical signal to a digital signal, and for providing said digital signal to said data processing means.

30. The system of claim 28 wherein said engine operation detecting means includes a sensing means for monitoring and sensing said operating characteristics in real-time.

31. The system of claim 28 wherein said data processing means includes a memory means for storing data sensed from said pressure sensing means and said engine operating detecting means.

32. The system of claim 29 wherein said data processing means includes an average exhaust pressure calculating means for calculating the average exhaust pressure sensed by said pressure sensing means for each cylinder of said internal combustion engine during a complete combustion cycle.

33. The system of claim 32 wherein said data processing means includes an optimum threshold calculating means for calculating an optimum threshold by:

calculating an optimum threshold value based on the values of said operating characteristics measured by said engine operation detecting means; and

subtracting said average exhaust pressure from said optimum threshold to yield said optimum threshold.

34. The system of claim 33 wherein said data processing means includes a sensed pressure conversion means for converting said sensed pressure into a cylinder exhaust value by receiving said digital signal and for determining the maximum sensed pressure based on said digital signal for each cylinder of the internal combustion engine during a normal combustion cycle to yield a cylinder exhaust value.

35. The system of claim 32 wherein said data processing means includes an optimum threshold calculating means for calculating an optimum threshold by:

calculating an optimum average pressure and an optimum peak pressure value using said detected operating characteristics of the internal combustion engine; and

calculating an optimum threshold for each cylinder by subtracting said optimum peak pressure from said optimum average exhaust pressure.

36. The system of claim 32 wherein said data processing means includes a sensed pressure conversion means for converting a sensed pressure by:

receiving said digital signal and for determining the maximum sensed pressure based on said digital signal for each cylinder of the internal combustion engine during a normal combustion cycle to yield a maximum sensed pressure; and

subtracting said maximum sensed pressure from said average exhaust pressure to yield said cylinder exhaust value.

37. The system of claim 32 wherein said data processing means includes a standard deviation calculation means that computes a standard deviation between a peak pressure and an average exhaust pressure.

38. The system of claim 37 wherein said data processing means includes an optimum threshold calculating means for calculating an optimum threshold by:

calculating an optimum standard deviation and an optimum average pressure using said detected operating characteristics of the internal combustion engine; and

calculating an optimum threshold by dividing said optimum standard deviation by said optimum mean to yield said optimum threshold.

39. The system of claim 38 wherein said data processing means includes a sensed pressure computing means for computing said sensed pressure by:

receiving said digital signal and for determining the maximum sensed pressure based on said digital signal for each cylinder of the internal combustion engine during a normal combustion cycle to yield a maximum sensed pressure; and

calculating a standard deviation between said maximum sensed pressure and said average exhaust pressure;

calculating a cylinder exhaust value by dividing said standard deviation by said average exhaust pressure to yield said cylinder exhaust value.

40. The system of claim 32 wherein said data processing means includes a running average calculating means which averages an average exhaust pressure value determined by said average exhaust pressure calculating means and a current exhaust pressure value to yield a running average exhaust pressure value, said running average exhaust pressure value replacing said average exhaust pressure value after each cylinder firing.

41. The system of claim 28 wherein said pressure sensing means includes a peak pressure sensing means for sensing the highest pressure released from each cylinder of said internal combustion engine during each combustion cycle.

42. The system of claim 28, wherein said pressure sensing means is a gauge-type pressure sensor.

43. The system of claim 42, wherein said gauge-type pressure sensor is a piezoelectric sensor.

44. The system of claim 42, wherein said gauge-type pressure sensor is a capacitive ceramic sensor.

45. The system of claim 28, wherein said pressure sensing means includes a single pressure sensor.

46. The system of claim 28, wherein said data processing means includes a cylinder number detecting means for detecting which cylinder has completely fired, partially or completely misfired during a combustion cycle.

47. A method in an internal combustion engine for detecting a full or partial engine cylinder misfire, the internal combustion engine comprised of a pressure sensing means mounted in an exhaust manifold and connected to an engine operation detecting means that is further connected to a data processing means, the method comprising the steps of:

sensing the peak pressure of exhaust gas generated by the internal combustion engine;

converting the sensed pressure into a cylinder exhaust value;

detecting operating characteristics of the internal combustion engine, said operating characteristics including at least one of the rotational speed, fuel consumption rate and coolant temperature of the internal combustion engine;

calculating an optimum threshold corresponding to said operating characteristics; and

comparing said cylinder exhaust value with said optimum threshold to determine if a partial or complete engine cylinder misfire occurred.

48. The method of claim 47 wherein said step of converting said sensed pressure into a cylinder exhaust value comprises the step of receiving said digital signal and for determining the maximum sensed pressure based on said digital signal for each cylinder of the internal combustion engine during a normal combustion cycle to yield a cylinder exhaust value.

49. The method of claim 47 wherein said step of calculating an optimum threshold comprises the steps of:

calculating an optimum threshold value based on the values of said operating characteristics measured by said engine operation detecting means; and

subtracting said average exhaust pressure from said optimum threshold to yield said optimum threshold.

50. The method of claim 49 wherein said step of calculating an optimum threshold comprises the steps of:

calculating an optimum average pressure and an optimum peak pressure value using said detected operating characteristics of the internal combustion engine; and

calculating an optimum threshold for each cylinder by subtracting said optimum peak pressure from said optimum average exhaust pressure.

51. The method of claim 50 wherein said step of converting the sensed pressure into a cylinder exhaust value comprising the steps of:

receiving said digital signal and for determining the maximum sensed pressure based on said digital signal for each cylinder of the internal combustion engine during a normal combustion cycle to yield a maximum sensed pressure value; and

subtracting said maximum sensed pressure value from said average exhaust pressure to yield a cylinder exhaust value.

52. The method of claim 47 wherein said step of calculating an optimum threshold comprises the steps of:

calculating an optimum standard deviation and an optimum average pressure using said detected operating characteristics of the internal combustion engine; and

calculating an optimum threshold by dividing said optimum standard deviation by said optimum mean to yield said optimum threshold.

53. The method of claim 52 wherein said step of comparing said peak pressure with said optimum threshold comprises the steps of:

calculating a standard deviation between said peak pressure and said average exhaust pressure;

calculating a coefficient of variation by dividing said standard deviation by said average exhaust pressure to yield said coefficient of variation; and

comparing said coefficient of variation to said optimum threshold and declaring at least a partial misfire if said coefficient of variation is greater than said optimum threshold and said average exhaust pressure is greater than said peak pressure.

54. The method of claim 47 further comprising the step of detecting an engine cylinder number for determining which cylinder has fired or misfired during a combustion cycle.

55. The method of claim 47 further comprising the step of detecting an air/fuel ratio for determining the air to fuel mixture entering each cylinder during a combustion cycle.