Electricity: measuring and testing – Electrolyte properties – Using a conductivity determining device
Reexamination Certificate
1998-12-23
2001-08-21
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Electrolyte properties
Using a conductivity determining device
C324S668000
Reexamination Certificate
active
06278281
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
The present invention relates to devices or systems for monitoring the condition of a working fluid in a system, as for example, lubricating oil in an engine or power transmission device where the oil is subject to contamination by introduction of foreign substances such as engine coolant or deterioration due to chemical activity from products of combustion or aging.
In the operation of motor vehicles, it has long been desired to have the capability to monitor the fluid in the power transmission components such as the engine and power transmissions on a real time or running basis during operation of the vehicle and to have the capability to provide a warning or indication to the vehicle operator that the lubricating fluid has reached a state of contamination or deterioration so as to be considered unsuitable for continued operation. Heretofore, attempts have been made to utilize alternating current impedance spectroscopy to detect the change in impedance of a low level current flowing through a capacitor immersed in the fluid. Examples of such known systems employing AC electro-impedance spectroscopy are those described in U.S. Pat. No. 4,733,556 issued to Meitzler, et al., U.S. Pat. No. 5,274,335 issued to Wang, et al., and U.S. Pat. No. 4,646,070 issued to Yasuhara, et al. These systems describe the application of electro-impedance spectroscopy techniques for determining the condition of internal combustion engine lubricating oil due to contamination with engine coolant and to deterioration due to the chemical effect of the products of combustion and aging on the engine lubricating oil. The aforesaid known systems employ the technique of applying an AC signal current relatively high frequency to the plates of a capacitor and determining the change in the impedance measured thereon. Typically such frequencies are in the multi-hertzian range of generally between 10 hertz and 500 kilohertz.
One known report of earlier work is that described in the publication “The Applications Of AC Impedance Technique For Detecting Glycol Contamination In Engine Oil” by S. S. Wang, et al. published Jan. 4, 1997 by Elselvier Science S.A. This later work describes scanning the immersed capacitor with a sinusoidal voltage of 2.5 volts peak over a range of frequencies from one milli-hertz to one kilohertz. However this later work utilized only the bulk resistance of the fluid as determined by utilizing frequencies in the range between 100 hertz and 1 kilohertz and is not suitable for on-board continuous fluid monitoring.
However, none of the aforesaid prior art systems have provided a low cost and useable technique for on-board vehicle monitoring of the condition of the lubricating fluids and, thus it has been desired to provide a way or means of providing a simple low cost system for indicating contamination or deterioration of lubricating fluids, particularly those in motor vehicle engine and power transmission applications.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a useful and novel technique of employing AC electro-impedance spectroscopy to monitor the condition of working fluids such as lubricant, and which is suitable for on-board motor vehicle use to enable real time monitoring of the condition of the lubricating oil in the engine or transmission.
The present invention employs a low level oscillating voltage signal across the plates or spaced electrodes of a capacitor immersed in the fluid to be monitored and measures the current of the signal applied at a first or high frequency associated with the bulk impedance of the fluid and at a second low frequency associated with the electrochemical properties of the surface of the electrode and determines the difference of the first and second measured currents. The current measured for the higher frequency is compared with measurements at the same frequency for acceptable fluid to determine if the current reading for the higher frequency associated with bulk impedance measurements is within predetermined limits. The difference in currents is compared with a predetermined threshold and if both aforesaid conditions are met, the fluid is considered to be suitable for continued operation; however, if either condition is not met, the monitor provides an electrical indication that the fluid is not suitable for continued operation.
In the preferred embodiment, current is measured and converted to a voltage for purposes of the comparison.
In a second embodiment the electrodes of the capacitance are positioned adjacent separate plate-type electrodes which have the first high frequency signal voltage applied also thereto for fluid level detection purposes; and, the circuitry for monitoring the fluid condition detecting capacitance is disabled if the level detector indicates a low-level condition.
The present invention thus provides a simple, low cost technique for real time onboard monitoring of lubricating fluid employed in engines and power transmissions of motor vehicles and other working fluid system applications.
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W. Fichtner, H. Kaden & W. Schindler: “On-line-Messugn der Eigenschaften von Schmierolen fur Verbrennungsmotoren mit einem elektrischen Sensor”. Technisches Messen 65 (1998) 2.
“The Applications of AC Impedance Technique For Detecting Glycol Contamination in Engine Oil” by S. S. Wang, et al., published Jan. 4, 1997 by Elselvier Science S.A.
“Novel Sensors for Portable Oil Analyzers” Case Western Reserve University, Cleveland, Ohio Dept. of Physics NTIS 19980624 080.
“AC Impedance Measurements of the Resistance and Capacitance of Lubricants” by S. S. Wang, et al, published Jun. 13, 1986 ASLE Transactions vol. 30, 4, 436-443.
The Development of in situ Electrochemical Oil-Condition Sensors by S. S. Wang, et al., Published 1974 by Elselvier Sequoia.
“On-board Monitoring of Properties of Lubricating Oils for Combustion Engines Using an Electric Sensor” by Fichtner, Wolfgang; Kaden, Heiner; Schindler, WolfgangTechnisches Messen 65(1998) 2:53-57 ©R. Oldenburg Verlag (Publisher) Missing Month.
Bauer Robert A.
Hansen James E.
Hirthe Richard W.
Polczynski Mark H.
Seitz Martin A.
Eaton Corporation
Johnsto n Roger A.
Kerveros J
Metjahic Safet
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