On-line oil condition sensor system for rotating and reciprocating machinery

• US 20030222656A1
• Filed: 12/19/2002
• Published: 12/04/2003
• Est. Priority Date: 12/20/2001
• Status: Active Grant

• Current Assignee: Phillips Intellectual Properties LLC
• Original Assignee: Alan D. Phillips, Dean Pappas, Robert S. Rodgers, William J. Eggers
• Inventors: Rodgers, Robert S., Eggers, William J., Phillips, Alan D., Pappas, Dean
• Granted Patent: US 7,043,402 B2
• Time in Patent Office: Days
• US Class Current: 324/605
• CPC Class Codes: G01N 27/02 by investigating impedance
• CPC Class Codes: G01N 33/2888 Lubricating oil characteristics, e.g. deterioration lubricating properties G01N33/30

Abstract

This invention is directed to a sensing system and method for detecting in real-time oil degradation, water contamination, and fuel dilution in operational engine oils for internal combustion engines. The method of the invention uses an electrochemical impedance analysis technique. The sensing system has a multi-electrode sensor element that can be immersed in the engine oil being monitored. The electrode element has at least two electrodes configured so that it can be directly mounted within the oil reservoir of an internal combustion engine. The sensor configuration with a dielectric lubricant contained between the electrodes defines an electrochemical sensor output-impedance-circuit that produces an indication of the operational oil'"'"'s quality or deterioration. A sinusoidal voltage waveform is applied across the electrodes of the sensor to produce a frequency dependent current through the oil and electrode system. A low frequency signal is used so that information on the resistance and capacitance of the degraded oil can be utilized to assess the specific condition of the oil being monitored.

Claims

1. A method for optimizing the electrochemical measurement parameters of an impedance analysis technique for analyzing lubricants for thermal-oxidative breakdown, water contamination, or fuel dilution, or combinations thereof, comprising the steps of:

bringing electrodes into contact with a sample of oil;

applying a direct current (DC) voltage bias to one of said electrodes;

applying an electrical potential to the sample to produce an electrical current therethrough;

applying a sinusoidal excitation frequency of a first value to the sample to produce a frequency dependent response therethrough;

varying said excitation frequency to the sample from the first value to a second value and continuing said frequency variation to a third and successive additional values to produce a frequency-dependent response therethrough;

measuring and recording the frequency-dependent current during said frequency variation steps;

recording from said voltage (E) and current (I) responses the ratio of the real component (E) versus the real component (I) of the complex impedance |Z| over frequency (f);

recording from said voltage (E) and current (I) responses the ratio of the imaginary component (E) versus the imaginary component (I) of the complex impedance |Z| over frequency (f);

recording the phase angle (θ

) between the AC potential and current versus the logarithm of frequency (f);

recording the sum of the square of said ratio of real component (E) versus real component (I) and said ratio of imaginary component (E) and imaginary component (I) all to the one-half power;

recording the logarithm of said magnitude of the impedance |Z| versus the logarithm of frequency (f);

recording from said logarithm of the magnitude of the impedance |Z| versus the logarithm of frequency (f) the point of transition from said frequency-dependent impedance response to said frequency-independent impedance response;

selecting an excitation frequency that is at least one order of magnitude less than said transition frequency of the logarithm of the magnitude of the impedance |Z| versus the logarithm of frequency (f); and

verifying from said plot of the phase angle (θ

) between the AC potential and current versus the logarithm of frequency (f) that the phase angle is close to 0° and

the shape of said magnitude impedance |Z| plot at said chosen distinct frequency is of a horizontal nature.

2. The method of claim 1 wherein said electrodes include a counter electrode and a working electrode.

3. The method of claim 1 wherein said electrodes include a counter electrode, a reference electrode, and a working electrode.

4. The method of claim 1 wherein the DC voltage bias is within the range of 0.0 V and 3.0 V.

5. The method of claim 4 wherein the DC voltage bias is 0.2 V.

6. The method of claim 1 wherein the electrical potential is within the range of 0.0 and 5.0 V.

7. The method of claim 6 wherein the electrical potential is 1.0 V.

8. The method of claim 1 wherein the first, second, third, and successive additional frequency values are within the range of 10 μ

Hz and 1 MHZ.

9. The method of claim 8 wherein the first, second, third, and successive additional frequency values are within the range of 0.1 and 100 Hz.

10. The method of claim 9 wherein the sinusoidal excitation frequency is 1 Hz or less.

11. The method of claim 1 wherein said impedance measurement at a frequency of less than 100 Hz produces order-of-magnitude-level changes for characterizing the thermal-oxidative condition of new and end-of-useful-life engine oils.

12. The method of claim 1 wherein said impedance measurement at a frequency of less than 100 Hz produces order-of-magnitude-level changes for characterizing the water condition of new and end-of-useful-life engine oils.

13. The method of claim 1 wherein said impedance measurement at a frequency of less than 100 Hz produces order-of-magnitude-level changes for characterizing the fuel contamination condition of new and end-of-useful-life engine oils.

14. The method of claim 1 wherein said impedance measurement at a frequency of less than 100 Hz enables the determination of the attendant first-order reactionary pathway of the primary functional additive chemistry of said sample.

15. A method for analyzing lubricants for thermal-oxidative breakdown, water contamination, or fuel dilution, or combinations thereof, comprising the steps of:

bringing electrodes into contact with a sample of oil;

applying a direct current (DC) voltage bias to one of said electrodes;

applying an electrical potential to the sample to produce an electrical current therethrough;

applying a sinusoidal excitation frequency to the sample to produce a frequency dependent response therethrough;

measuring and recording the frequency-dependent current during said frequency application;

recording from said voltage (E) and current (I) responses the ratio of the real component (E) versus the real component (I) of the complex impedance |Z| over frequency (f);

recording from said voltage (E) and current (I) responses the ratio of the imaginary component (E) versus the imaginary component (I) of the complex impedance |Z| over frequency (f);

recording the phase angle (θ

) between the AC potential and current versus the logarithm of frequency (f);

recording the sum of the square of said ratio of real component (E) versus real component (I) and said ratio of imaginary component (E) and imaginary component (I) all to the one-half power;

recording the logarithm of said magnitude of the impedance |Z| versus the logarithm of frequency (f);

recording the imaginary impedance component versus the real impedance component at said frequency (f);

16. The method of claim 15 wherein said electrodes include a counter electrode and a working electrode.

17. The method of claim 15 wherein said electrodes include a counter electrode, reference electrode, and a working electrode.

18. The method of claim 15 wherein two or more of thermal-oxidative breakdown, water contamination, or fuel dilution are simultaneously monitored.

19. The method of claim 15 wherein the DC voltage bias is within the range of 0.0 V and 3.0 V.

20. The method of claim 19 wherein the DC voltage bias is 0.2 V.

21. The method of claim 15 wherein the electrical potential is within the range of 0.0 and 5.0 V.

22. The method of claim 21 wherein the electrical potential is 1.0 V.

23. The method of claim 15 wherein the sinusoidal excitation frequency is within the range of 0.1 and 100 Hz.

24. The method of claim 23 wherein the sinusoidal excitation frequency is 1 Hz or less.

25. The method of claim 15 wherein the step of bringing the electrodes into contact with the sample includes attaching the electrodes on-line.

26. The method of claim 25 wherein the step of measuring and recording the voltage and current is done continuously.

27. The method of claim 25 wherein the step of measuring and recording the voltage and current is done intermittently.

28. The method of claim 15 wherein the step of bringing the electrodes into contact with the sample includes placing the electrodes in an on-line sample reservoir.

29. The method of claim 15 wherein the step of bringing the electrodes into contact with the sample includes placing the electrodes in an on-line sample reservoir, and then removing the electrodes from the sample reservoir for replacement of said electrodes.

30. The method of claim 15 wherein the step of bringing the electrodes into contact with the sample further includes bringing a temperature sensitive resistor into contact with the sample such that, from the determined oil temperature, said measurement of the magnitude of the impedance |Z| is corrected to compensate for the effects of engine oil temperature changes.

31. The method of claim 15 wherein said impedance measurement at a frequency of less than 100 Hz produces order-of-magnitude-level changes for characterizing the thermal-oxidative condition of new and end-of-useful-life engine oils.

32. The method of claim 15 wherein said impedance measurement at a frequency of less than 100 Hz enables the determination of the attendant first-order reactionary pathway of the primary functional additive chemistry of the sample.

33. The method of claim 15 wherein said impedance measurement at a frequency of less than 100 Hz is provides an indication of water contamination in new and used engine oils.

34. The method of claim 15 wherein said impedance measurement at a frequency of less than 100 Hz provides an indication fuel dilution in new and used engine oils.

35. An on-line method for analyzing lubricants for thermal-oxidative breakdown, water contamination, or fuel dilution, or combinations thereof, comprising the steps of:

placing electrodes and a temperature sensitive resistor in an on-line lubricant sample reservoir;

applying a direct current (DC) voltage bias to one of said electrodes;

applying an electrical potential to the sample to produce an electrical current therethrough;

applying a sinusoidal excitation frequency to the sample to produce a frequency-dependent response therethrough;

measuring and recording the frequency-dependent current during said frequency application step;

recording from said voltage (E) and current (I) responses the ratio of the real component (E) versus the real component (I) of the complex impedance |Z| at frequency (f);

recording from said voltage (E) and current (I) responses the ratio of the imaginary component (E) versus the imaginary component (I) of the complex impedance |Z| at frequency (f);

recording the phase angle (θ

) between the AC potential and current at frequency (f);

recording the sum of the square of said ratio of real component (E) versus real component (I) and said ratio of imaginary component (E) and imaginary component (I) all to the one-half power;

recording the logarithm of said magnitude of the impedance |Z| versus the logarithm of frequency (f);

recording the phase angle (θ

) between the AC potential and current versus the logarithm of frequency (f);

recording the imaginary impedance component versus the real impedance component at said frequency (f); and

observing said recordings to determine the condition of said sample with respect to its thermal-oxidative breakdown, water contamination, fuel dilution, or combinations thereof.

36. The method of claim 35 wherein said electrodes include a counter electrode and a working electrode.

37. The method of claim 35 wherein said electrodes include a counter electrode, reference electrode, and a working electrode.

38. The method of claim 35 wherein two or more of thermal-oxidative breakdown, water contamination, or fuel dilution are simultaneously monitored.

39. The method of claim 35 wherein the DC voltage bias is within the range of 0.0 V and 3.0 V.

40. The method of claim 35 wherein the DC voltage bias is 0.2 V.

41. The method of claim 35 wherein the electrical potential is within the range of 0.0 V and 5.0 V.

42. The method of claim 39 wherein the electrical potential is 1.0 V.

43. The method of claim 35 wherein the sinusoidal excitation frequency is within the range of 0.1 and 100 Hz.

44. The method of claim 41 wherein the sinusoidal excitation frequency is 1 Hz or less.

45. The method of claim 35 wherein the step of measuring and recording the magnitude of the impedance |Z| is done continuously.

46. The method of claim 35 wherein the step of measuring and recording the magnitude of the impedance |Z| is done intermittently.

47. The method of claim 35 wherein the said temperature sensitive resistor in contact with the sample is employed to correct said measurement of the magnitude of the impedance |Z| to compensate for the effects of engine oil temperature changes.

48. The method of claim 35 wherein the step of measuring and recording the phase angle (θ

) is done continuously.

49. The method of claim 35 wherein the step of measuring and recording the phase angle (θ

) is done continuously intermittently.

50. The method of claim 35 wherein the step of measuring and recording the magnitude of the impedance |Z| is executed automatically upon the detection of fresh oil in contact with said electrodes.

51. The method of claim 35 wherein the step of measuring and recording said real and imaginary components of the magnitude impedance |Z| is employed to determine and subsequently indicate common sensor failure modes.

52. The method of claim 49 wherein the step of measuring and recording said real and imaginary components of the magnitude impedance |Z| is employed to determine and subsequently indicate a cable failure via the cessation of current through said electrodes.

53. The method of claim 49 wherein the step of measuring and recording said real and imaginary components of the magnitude impedance |Z| is employed to determine and subsequently indicate a problematic on-line condition via a noticeably low value for said magnitude impedance |Z| due to said electrodes becoming shorted by metallic wear particles in said oil medium.

54. The method of claim 49 wherein the step of measuring and recording said real and imaginary components of the magnitude impedance |Z| is employed to determine and subsequently indicate said electrodes are no longer immersed in said oil via the recorded impedance |Z| that is no longer dominantly resistive.

55. The method of claim 35 wherein said electrodes and said temperature sensitive resistor are attached to a source of a sample of oil.

56. The method of claim 35 wherein said electrodes and said temperature sensitive resistor are installed in a chamber attached to a use container for said oil.

57. The method of claim 35 wherein said electrodes and said temperature sensitive resistor are installed in a chamber attached to a return line for said oil.

58. The method of claim 35 wherein said electrodes and said temperature sensitive resistor are, at the occurrence of a required oil change, removed from said on-line sample reservoir and subsequently replaced.

59. The method of claim 35 wherein said impedance measurement at a frequency of less than 100 Hz produces order-of-magnitude-level changes for characterizing the thermal-oxidative condition of new and end-of-useful-life engine oils.

60. The method of claim 35 wherein said impedance measurement at a frequency of less than 100 Hz enables the determination of the attendant first-order reactionary pathway of the primary functional additive chemistry of the sample.

61. The method of claim 35 wherein said impedance measurement at a frequency of less than 100 Hz provides an indication of water contamination in new and used engine oils.

62. The method of claim 35 wherein said impedance measurement at a frequency of less than 100 Hz provides an indication of fuel dilution in new and used engine oils.

63. The method of claim 35 wherein said impedance measurement at a frequency of less than 100 Hz provides an indication of oil degredation in new and used engine oils.

64. An in-situ, on-line system for monitoring lubricants for thermal-oxidative breakdown, water contamination, and fuel dilution, or combinations thereof, in a lubricating oil reservoir, comprising:

a. means for generating an excitation stimulus comprised of a DC bias, an applied voltage, and an alternating current signal;

b. sensor means adapted to be installed in an existing access port or drain port of the lubricating oil reservoir for applying the excitation stimulus to the lubricant contained therein, said sensor means having

(i) two closely parallel, electrically conductive electrodes extending into the lubricating oil reservoir, the two electrodes immersed in the lubricant therein and having the excitation stimulus applied thereto,

(ii) a mechanical housing structurally surrounding said two electrodes for connecting and removing the sensor means to and from said means for generating the excitation stimulus;

(iii) a temperature sensitive resistor (surface mount thermistor) in thermal contact with said oil in the lubricating oil reservoir and electrically isolated from said electrodes, the resistor providing a voltage output for determining the temperature of the oil;

(iv) a silicone O-ring within the inner cavity of said mechanical housing, the silicone O-ring providing a leak-proof seal to prevent the lubricating oil from contacting either the electrodes or resistor within said inner cavity;

c. threaded housing means for adapting said sensor means to be installed in the existing access port or drain port of the lubricating oil reservoir, said housing having

(i) an electrical interconnect component comprising a plurality of contacts for electrically connecting said sensor means with said excitation stimulus means, the interconnect component enabling multiple cycles of engagement and disengagement by way of gold-over-nickel plating material;

(ii) a silicone O-ring corresponding with the exposed end perimeter of the mechanical housing structurally surrounding said two electrodes, the silicone O-ring providing an additional leak-proof seal to prevent the lubricating oil from entering either of said mechanical housings;

(iii) a threaded jam nut to securely tighten the mechanical housing structurally surrounding said two electrodes to said threaded adapter housing, the threaded jam nut affording an even further leak-proof design by forcing said O-rings into a state of compression;

d. potentiostat electronics means placed immediately proximate to the existing access port or drain port of the lubricating oil reservoir to electronically buffer instantaneously the excitation stimulus between said electrically conductive electrodes, collectively comprised of the DC bias, the applied voltage, and the alternating current signal, said potentiostat means also having a second buffer monitoring said voltage portion and providing return signals to the first buffer, the attendant current portion of the stimulus further transformed into an additional voltage by a third buffer of said potentiostat means;

e. temperature compensation electronics means resident to said potentiostat means and electrically connected to the temperature sensitive resistor in thermal contact with the oil, the temperature compensation electronics providing an automatic correction of the output indication |Z| due to changes in the temperature of said lubricating oil, said temperature compensation means also having a buffer to current-bias the produced voltage from said resistor; and

f. instrument electronics means connected between the 12 V-24 V vehicle power bus and the potentiostat electronics means.

65. The system of claim 64, further comprising means for evaluating the magnitude impedance |Z| between the alternating current signal generating means and said potentiostat device, thereby determining the degree of either the conductive or non-conductive condition of the resistive oil lubricant path.

66. The system of claim 64, further comprising means for comparing the path impedance to a predetermined path impedance set point resulting in a compared path impedance signal.

67. The system of claim 64, further comprising means for indicating normal thermal-oxidative levels of the oil medium when the path impedance is either greater than or less than the predetermined path impedance.

68. The system of claim 64, further comprising means for indicating abnormal contamination levels of the oil medium when the path impedance is either greater than or less than the predetermined path impedance set point.

69. The system of claim 64, further comprising cable means interposed between the alternating current signal generating means and the sensor means for conducting the alternating current signal to the sensor means and for conducting an impedance signal therefrom back to the potentiostat device whereby the sensor means may be remotely mounted.

70. The system of claim 64, wherein said sensor means includes a working electrode and a reference electrode.

71. The system of claim 64, wherein the alternating current signal is sinusoidal.

72. The system of claim 64, wherein thermal-oxidative breakdown and water contamination are simultaneously monitored.

73. The system of claim 64, wherein the DC voltage bias is within the range of 0.0 V and 3.0 V.

74. The system of claim 73 wherein the DC voltage bias is 0.2 V.

75. The system of claim 64 wherein the electrical potential is within the range of 0.0 V and 5.0 V.

76. The system of claim 75 wherein the electrical potential is 1.0 V.

77. The system of claim 64 wherein the sinusoidal excitation frequency is within the range of 0.1 and 100 Hz.

78. The system of claim 77 wherein the sinusoidal excitation frequency is 1 Hz or less.

79. The system of claim 64 wherein the comparing means for comparing the path impedance to the predetermined path impedance set point is a potentiostat.

80. The system of claim 64 further comprising latch means for maintaining in an energized state one of the indicating means upon the occurrence of the condition initiating indication.

81. The system of claim 64 wherein fuel dilution is continuously monitored.

82. The system of claim 64 wherein the sinusoidal excitation frequency is within the range of 0.1 and 500 KHz.

83. The system of claim 64 wherein the comparing means for comparing the path impedance to the predetermined path impedance set point is a potentiostat.

84. The system of claim 64 further comprising latch means for maintaining in an energized state one of the indicating means upon the occurrence of the condition initiating indication.

85. The system of claim 64 wherein said electrodes are fabricated on the primary substrate comprises a silicon material.

86. The system of claim 64 wherein said electrodes include a gold overlay.

87. A method for sensing impedance characteristics of engine oil while said oil is in use in an operating combustion engine to determine the relative condition of said oil, comprising the steps of:

(a) placing at least two electrodes into contact with said oil;

(b) applying an electric potential across said electrodes in order to generate an electric current through said oil;

(c) applying a sinusoidal excitation frequency of a first value to said electrodes to produce a frequency dependent response through said oil;

(d) varying said excitation frequency; and

(e) measuring and recording the frequency-dependent current during said frequency variation step to determine the impedance characteristics of said oil and thereby assess its relative condition.

88. A method for analyzing lubricants for thermal-oxidative breakdown or water contamination, or fuel dilution, or combinations thereof, comprising the steps of:

bringing electrodes into contact with a sample of oil;

applying an electrical potential to said electrodes to produce an electrical current through said oil sample;

applying a sinusoidal excitation frequency to the sample to produce a frequency dependent response through said oil;

measuring said current during said frequency application;

measuring the complex impedance |Z| for each frequency applied based on measured current and applied voltage;

measuring the phase angle (θ

) between the AC potential and current; and

comparing said impedance and said phase angle to predetermined values to assess thermal-oxidative breakdown or water contamination, or fuel dilution, or combinations thereof of said oil sample.

89. The method of claim 88 further comprising determining the imaginary and real impedance components for applied frequencies.

90. The method of claim 89 further comprising applying a direct current voltage bias to one of said electrodes.

91. The method of claim 90 wherein the DC voltage bias is within the range of 0.0 V and 3.0 V.

92. The method of claim 90 wherein the electrical potential is within the range of 0.0 and 5.0 V.

93. The method of claim 88 wherein the sinusoidal excitation frequency is within the range of 0.1 and 100 Hz.

94. The method of claim 88 wherein the sinusoidal excitation frequency is 1 Hz or less.

95. The method of claim 93 wherein said impedance measurement at a frequency of less than 100 Hz enables the determination of the attendant first-order reactionary pathway of the primary functional additive chemistry of the sample.