Apparatus and methods for determining start of combustion for an internal combustion engine

• US 6,598,468 B2
• Filed: 07/11/2001
• Issued: 07/29/2003
• Est. Priority Date: 07/11/2001
• Status: Active Grant

• Current Assignee: Cummins Incorporated
• Original Assignee: Cummins Incorporated
• Inventors: Zur Loye, Axel O, Zigan, James A, Brackney, Larry J
• Primary Examiner(s): McCall, Eric S.
• Assistant Examiner(s): STEVENS, MAURICE E
• Application Number:
  US09/901,689
• Publication Number:
  US 20030010101A1
• Time in Patent Office: 748 Days
• Field of Search: 731/16, 731/15, 731/173, 701/101-102, 123/435, 123/425
• US Class Current: 73/114.06
• CPC Class Codes: F02B 1/12 with compression ignition with fuel-air charge ignited by compression ignition of an additional fuel F02B7/00
• CPC Class Codes: F02D 2041/389 for injecting directly into the cylinder
• CPC Class Codes: F02D 35/023 by determining the cylinder pressure
• CPC Class Codes: F02D 35/028 by determining the combustion timing or phasing
• CPC Class Codes: F02D 41/14 Introducing closed-loop corrections
• CPC Class Codes: F02D 41/3035 a mode being the premixed charge compression-ignition mode
• CPC Class Codes: F02D 41/401 Controlling injection timing F02D41/402 takes precedence
• CPC Class Codes: G01M 15/08 by monitoring pressure in cylinders
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

An apparatus and methods for effectively determining the start of combustion in a cylinder of an internal combustion engine where the start of combustion is calculated by obtaining cylinder pressure data (P), processing the cylinder pressure data (P) into a processed pressure value indicative of the occurrence of SOC, comparing the processed pressure value to a predetermined threshold value, if the processed pressure value crosses the predetermined threshold value, determining that SOC has occurred, and calculating a crank shaft location at which the predetermined threshold value was crossed by the processed pressure value thereby identifying the crank shaft location at which SOC occurred. In alternative embodiments, optional steps may be provided including a verification step, a windowing step, a filtering step, determining occurrence of misfire, and determining occurrence of retarded timing.

Claims

1. A method of determining occurrence of a start of combustion (SOC) in a cylinder of an internal combustion engine having a crankshaft comprising steps of:

obtaining cylinder pressure data (P);

processing said cylinder pressure data (P) into a processed pressure value indicative of the occurrence of SOC;

comparing said processed pressure value to a predetermined threshold value;

if said processed pressure value crosses said predetermined threshold value, determining that SOC has occurred; and

calculating a crank shaft location at which said predetermined threshold value was crossed by said processed pressure value thereby identifying the crank shaft location at which SOC occurred.

2. The method of claim 1, further including a verification step to ensure integrity of said cylinder pressure data (P) so that said cylinder pressure data (P) is able to b processed into said processed pressure value indicative of the occurrence of SOC.

3. The method of claim 2, wherein said verification step includes monitoring continuity of said cylinder pressure data (P) across a bottom dead center boundary of a reciprocally mounted piston in said cylinder.

4. The method of claim 3, further including the step of providing a fault signal if said cylinder pressure data across said bottom dead center boundary is not continuous.

5. The method of claim 2, wherein said verification step includes comparing P measured when a reciprocally mounted piston in said cylinder is at a top dead center position with P measured when said piston is at a bottom dead center position.

6. The method of claim 5, further including the step of providing a fault signal if said P measured at said top dead center is not substantially greater than said P measured at bottom dead center position.

7. The method of claim 1, wherein said cylinder pressure data (P) is synchronized to an angle of a crank shaft, and further including the step of windowing said cylinder pressure data (P) within a predetermined crank shaft angle window which is inclusive of said start of combustion (SOC).

8. The method of claim 7, wherein said predetermined crank shaft angle window is between −

180 and +180 crank shaft degrees from top dead center of a piston in said cylinder.

9. The method of claim 8, wherein said predetermined crank shaft angle window is between −

50 and +50 crank shaft degrees from top dead center of a piston in said cylinder.

10. The method of claim 9, wherein said predetermined crank shaft angle window is between −

10 and +30 crank shaft degrees from top dead center of a piston in said cylinder.

11. The method of claim 1, further including the step of filtering at least one of said cylinder pressure data (P) and said processed pressure value.

12. The method of claim 11, wherein said processed pressure value is filtered cylinder pressure data (P).

13. The method of claim 11 wherein said step of filtering is attained by at least one of an analog filter and a digital filter.

14. The method of claim 13, wherein said at least one of an analog filter and a digital filter has a cutoff frequency inversely proportional to at least one of bore size of said cylinder of said engine and a bowl size of a piston received within said cylinder of said engine.

15. The method of claim 13, wherein said at least one of an analog filter and a digital filter has a cutoff frequency of approximately 11,000 Hz/(diameter of said cylinder).

16. The method of claim 1, further including the step of determining occurrence of misfire.

17. The method of claim 16, wherein misfire is determined to have occurred when said processed pressure value does not cross said predetermined threshold within a predetermined crank shaft angle window.

18. The method of claim 17, further including the step of providing a misfire fault signal upon determining occurrence of misfire.

19. The method of claim 17, further including the step of defining said SOC crank shaft location to be a predetermined angle upon providing said misfire fault signal.

20. The method of claim 19, wherein said predetermined angle is 50 degrees after top dead center position of a piston reciprocally mounted in said cylinder.

21. The method of claim 16, wherein said cylinder pressure data (P) is synchronized to an angle of a crank shaft, and occurrence of misfire is determined by calculation of a pressure ratio (PR) defined as:

22. The method of claim 1, wherein said cylinder pressure data (P) is synchronized to an angle of a crank shaft, further including the step of determining existence of retarded timing by comparing a pressure ratio (PR) to a predetermined expected PR value, said pressure ratio being defined as:

23. The method of claim 1, wherein at least one of said steps are performed by a processor.

24. The method of claim 23, wherein said processor includes an electronic control unit (ECU).

25. The method of claim 24, wherein said step of obtaining cylinder pressure data (P) is attained by a pressure sensing means that generates a pressure data signal indicative of pressure in said cylinder to said processor.

26. The method of claim 25, wherein said pressure sensing means includes at least one of a pressure sensor, accelerometer, ion probe, optical diagnostic, strain gage, load washer fast thermocouple, torque sensor, RPM sensor and emissions sensor.

27. The method of claim 26, wherein said pressure sensing means is a pressure sensor.

28. The method of claim 1, wherein said engine is one of a diesel engine, a spark ignited engine, a flexible fuel engine, and a premixed charge compression ignition (PCCI) engine.

29. The method of claim 28, wherein said engine is a premixed charge compression ignition (PCCI) engine.

30. The method of claim 1, wherein said processed pressure value is a cylinder pressure and said predetermined threshold value is an isentropic compression pressure value.

31. The method of claim 1, wherein said cylinder pressure data (P) is synchronized to an angle of a crank shaft, and said step of processing said cylinder pressure data (P) into a processed pressure value includes the step of calculating a pressure change rate.

32. The method of claim 31, wherein said pressure change rate is dP/dθ

value indicative of rate of change in pressure in said cylinder with respect to an angle of said crank shaft.

33. The method of claim 31, wherein said pressure change rate is dP/dt value indicative of rate of change in pressure in said cylinder with respect to time.

34. The method of claim 31, wherein said step of processing said cylinder pressure data (P) further includes the step of determining a peak pressure change rate (PPCR).

35. The method of claim 34, wherein said peak pressure change rate (PPCR) is said processed pressure value which is compared to said predetermined threshold value.

36. The method of claim 34, further including the step of comparing said peak pressure change rate (PPCR) with a minimum pressure change rate, and determining that a misfire has occurred if said PPCR is substantially similar to said minimum pressure change rate.

37. The method of claim 34, further including the step of comparing said peak pressure change rate (PPCR) with a minimum pressure change rate, and determining that advanced combustion exists if said PPCR is substantially greater than said minimum pressure change rate.

38. The method of claim 1, wherein said cylinder pressure data (P) is synchronized to an angle of a crank shaft, and said step of processing said cylinder pressure data (P) into a processed pressure value includes the step of calculating a pressure change acceleration rate.

39. The method of claim 38, wherein said pressure change acceleration rate is (d²P/dθ

²) indicative of acceleration of pressure in said cylinder with respect to angle of said crank shaft.

40. The method of claim 38, wherein said pressure change acceleration rate is (d²P/d²) value indicative of acceleration of pressure in said cylinder with respect to time.

41. The method of claim 38, wherein said pressure change acceleration rate is obtained by processing said cylinder pressure data (P) utilizing a software program executed by a processor.

42. The method of claim 38, wherein said pressure change acceleration rate is obtained by processing said cylinder pressure data (P) utilizing at least one differentiator circuit having an operational amplifier.

43. The method of claim 42, wherein said pressure change acceleration rate is obtained by processing said cylinder pressure data (P) utilizing two differentiator circuits in series.

44. The method of claim 38, wherein said pressure change acceleration rate is further processed using at least one of a filter, a level shifter, and a comparator.

45. The method of claim 44, wherein said step of comparing said processed pressure value to said predetermined threshold value is attained utilizing a comparator circuit.

46. The method of claim 1, wherein said cylinder pressure data (P) is synchronized to an angle of a crank shaft, and said step of processing said cylinder pressure data (P) into a processed pressure value includes the step of calculating an apparent heat release rate (AHRR_(i)) value in said cylinder based on said cylinder pressure data P, said AHRR_(i) value indicative of the rate of heat released in said cylinder with respect to angle of said crank shaft.

47. The method of claim 46, further including the step of calculating a pressure change rate (dP/dθ

_(i)) value indicative of rate of change in pressure in said cylinder with respect to angle of said crank shaft.

48. The method of claim 47, wherein said apparent heat release rate (AHRR_(i)) value is calculated based on said dP/dθ

_(i) value.

49. The method of claim 48, further including the step of calculating a cumulative heat release (CHR_(i)) value in said cylinder based on said AHRR_(i) value, said CHR_(i) value indicative of cumulative heat released in said cylinder with respect to angle of said crank shaft.

50. The method of claim 49, further including the step of comparing said CHR_(i) value to said predetermined threshold value and if said calculated CHR_(i) value crosses said predetermined threshold value, determining that said SOC has occurred and calculating angle of said crank shaft at which said predetermined threshold value is crossed.

51. An apparatus for determining occurrence of a start of combustion (SOC) in a cylinder of an engine having a crankshaft comprising:

a pressure sensing means for sensing pressure in said cylinder and providing a pressure signal indicative of said pressure in said cylinder;

a processor that receives said pressure signal from said pressure sensing means, processes said pressure signal into a processed pressure signal, compares said processed pressure signal to a predetermined threshold value, determines that SOC has occurred if said processed pressure signal crosses said predetermined threshold value; and

a sensor adapted to monitor location of said crank shaft to allow said processor to calculate crank shaft location at which SOC occurred.

52. The apparatus of claim 51, wherein said processor is further adapted to perform a verification test to ensure integrity of said cylinder pressure signal so that said cylinder pressure signal is able to be processed into said processed pressure signal indicative of the occurrence of SOC.

53. The apparatus of claim 52, wherein said verification test monitors continuity of said cylinder pressure signal across a bottom dead center boundary of a reciprocally mounted piston in said cylinder between cycles, and said processor provides a fault signal if said cylinder pressure data across said bottom dead center boundary is not continuous.

54. The apparatus of claim 52, wherein said verification test compares cylinder pressure signal measured when a reciprocally mounted piston in said cylinder is at a top dead center position with cylinder pressure signal measured when said piston is at a bottom dead center position, and said processor provides a fault signal if said pressure signal measured at said top dead center is not substantially greater than said cylinder pressure signal measured at bottom dead center position.

55. The apparatus of claim 51, wherein said cylinder pressure signal is synchronized to an angle of a crank shaft, and said processor is further adapted to window said pressure signal within a predetermined crank shaft angle window which is inclusive of said start of combustion (SOC).

56. The apparatus of claim 55, wherein said predetermined crank shaft angle window is between −

180 and +180 crank shaft degrees from top dead center of a piston in said cylinder.

57. The apparatus of claim 56, wherein said predetermined crank shaft angle window is between −

50 and +50 crank shaft degrees from top dead center of a piston in said cylinder.

58. The apparatus of claim 57, wherein said predetermined crank shaft angle window is between −

10 and +30 crank shaft degrees from top dead center of a piston in said cylinder.

59. The apparatus of claim 51, further comprising a filter to filter at least one of said pressure signal and said processed pressure signal to thereby facilitate said determination of occurrence of SOC.

60. The apparatus of claim 59, wherein said filter is at least one of an analog filter and a digital filter.

61. The apparatus of claim 60, wherein said at least one of an analog filter and a digital filter has a cutoff frequency inversely proportional to at least one of bore size of said cylinder of said engine and a bowl size of a piston received within said cylinder of said engine.

62. The apparatus of claim 60, wherein said at least one of an analog filter and a digital filter has a cutoff frequency of approximately 11,000 Hz/(diameter of said cylinder).

63. The apparatus of claim 51, wherein said processor is further adapted to determine occurrence of misfire.

64. The apparatus of claim 63, wherein said processor provides a misfire fault signal upon determining occurrence of misfire, said misfire being determined to have occurred when said processed pressure signal does not cross said predetermined threshold within a predetermined crank shaft angle window.

65. The apparatus of claim 64, wherein said processor defines said SOC crank shaft location to be a predetermined angle upon providing said misfire fault signal.

66. The apparatus of claim 65, wherein said predetermined angle is 50 degrees after top dead center position of a piston reciprocally mounted in said cylinder.

67. The apparatus of claim 63, wherein said pressure signal is synchronized to an angle of a crank shaft, and said processor determines occurrence of misfire by calculating a pressure ratio (PR) defined as:

68. The apparatus of claim 51, wherein said cylinder pressure signal is synchronized to an angle of a crank shaft, and said processor determines existence of retarded timing by comparing a pressure ratio (PR) to a predetermined expected PR value, said pressure ratio being defined as:

69. The apparatus of claim 51, wherein said processor includes an electronic control unit (ECU).

70. The apparatus of claim 51, wherein said pressure sensing means includes at least one of a pressure sensor, accelerometer, ion probe, optical diagnostic, strain gage, load washer, fast thermocouple, torque sensor, RPM sensor and emissions sensor.

71. The apparatus of claim 70, wherein said pressure sensing means is a pressure sensor.

72. The apparatus of claim 51, wherein said engine is one of a diesel engine, a spark ignited engine, a flexible fuel engine, and a premixed charge compression ignition (PCCI) engine.

73. The apparatus of claim 72, wherein said engine is a premixed charge compression ignition (PCCI) engine.

74. The apparatus of claim 73, wherein said engine includes a combustion history control system, and said processor variably controls said combustion history control system based on said calculated SOC.

75. The apparatus of claim 51, wherein said processed pressure signal is indicative of a cylinder pressure.

76. The apparatus of claim 51, wherein said cylinder pressure signal is synchronized to an angle of a crank shaft and is processed into a pressure change rate.

77. The apparatus of claim 76, wherein said pressure change rate is (dP/dθ

) indicative of rate of change in pressure in said cylinder with respect to an angle of said crank shaft.

78. The apparatus of claim 76, wherein said pressure change rate is (dP/dt) indicative of rate of change in pressure in said cylinder with respect to time.

79. The apparatus of claim 76, wherein said processed pressure value is a cylinder pressure and said predetermined threshold value is an isentropic compression pressure value.

80. The apparatus of claim 79, wherein said predetermined threshold is a minimum pressure change rate and said PPCR is compared to said minimum pressure change rate.

81. The apparatus of claim 80, wherein if said peak pressure change rate (PPCR) is substantially similar to an absolute value of said minimum pressure change rate, determining that a misfire has occurred.

82. The apparatus of claim 80, wherein if said peak pressure change rate is substantially greater than said minimum pressure change rate, determining that an extremely advanced combustion has occurred.

83. The apparatus of claim 51, wherein said cylinder pressure data (P) is synchronized to an angle of a crank shaft, and said processing means is adapted to calculate a pressure change acceleration rate from said pressure signal.

84. The apparatus of claim 83, wherein said pressure change acceleration rate is (d²P/dθ

²) which is indicative of acceleration of pressure in said cylinder with respect to angle of said crank shaft.

85. The apparatus of claim 83, wherein said pressure change acceleration rate is (d²P/dt²) value indicative of acceleration of pressure in said cylinder with respect to time.

86. The apparatus of claim 83, further including a software program executed by said processor that processes said cylinder pressure signal to provide said pressure change acceleration rate.

87. The apparatus of claim 83, further including at least one differentiator circuit having an operational amplifier that processes said cylinder pressure signal to provide said pressure change acceleration rate.

88. The apparatus of claim 87, wherein said at least one differentiator circuit is two differentiator circuits in series.

89. The apparatus of claim 83, further including at least one of a filter, a level shifter, and a comparator that further processes said pressure change acceleration rate.

90. The apparatus of claim 83, further including a comparator circuit adapted to compare said processed pressure signal to said predetermined threshold value.

91. The apparatus of claim 51, wherein said cylinder pressure signal is synchronized to an angle of a crank shaft and is processed into an apparent heat release rate (AHRR(₁)) indicative of the rate of heat released in said cylinder with respect to angle of said crank shaft.

92. The apparatus of claim 91, wherein said cylinder pressure signal is further processed into a pressure change rate (dP/dθ

_(i)) indicative of rate of change in pressure in said cylinder with respect to angle of said crank shaft.

93. The apparatus of claim 92, wherein said apparent heat release rate (AHRR_(i)) is calculated based on said pressure change rate (dP/dθ

_(i)).

94. The apparatus of claim 93, wherein said processor calculates a cumulative heat release (CHR_(i)) in said cylinder based on said apparent heat release rate (AHRR_(i)), said CHR_(i) being indicative of cumulative heat released in said cylinder with respect to angle of said crank shaft.

95. The apparatus of claim 94, wherein said CHR_(i) is said processed pressure signal which is compared to said predetermined threshold value by said processor.

96. The apparatus of claim 95, wherein said processor is further adapted to perform a verification test to ensure integrity of said cylinder pressure signal by monitoring continuity of said cylinder pressure signal across a bottom dead center boundary of a reciprocally mounted piston in said cylinder between cycles, and said processor provides a fault signal if said cylinder pressure data across said bottom dead center boundary is not continuous.

97. The apparatus of claim 51, wherein said processor determines an initial cylinder pressure (P₍₀₎), determines an initial cumulative heat release (CHR₍₀₎) value, calculates a pressure change rate (dP/dθ

_(i)) value in said cylinder indicative of rate of change in pressure with respect to an angle of said crank shaft, calculates an apparent heat release rate (AHRR_(i)) value of said cylinder utilizing said pressure change rate (dP/dθ

_(i)) value, calculates a cumulative heat release (CHR₁)) value of said cylinder by adding said AHRR_(i) value to a CHR<sub>(i−

1)</sub> value, compares said CHR_(i) value to said predetermined threshold value, repeats said calculation until said calculated CHR_(i) value crosses said predetermined threshold value, and calculates a SOC crank shaft location in which said predetermined threshold value is crossed.

98. The apparatus of claim 97, wherein said pressure sensing means includes at least one of a pressure sensor, accelerometer, ion probe, optical diagnostic, strain gage, load washer, fast thermocouple, torque sensor, RPM sensor and emissions sensor.

99. The apparatus of claim 98, wherein said pressure sensing means is a pressure sensor.

100. The apparatus of claim 97, wherein said engine is one of a diesel engine, a spark ignited engine, a flexible fuel engine, and a premixed charge compression ignition (PCCI) engine.

101. The apparatus of claim 100, wherein said engine is a premixed charge compression ignition (PCCI) engine.