Measuring and testing – Simulating operating condition – Marine
Reexamination Certificate
2000-10-12
2002-10-15
McCall, Eric S. (Department: 2855)
Measuring and testing
Simulating operating condition
Marine
Reexamination Certificate
active
06463796
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the art of oil and/or lubricant diagnostics. It finds particular application in conjunction with diesel engines such as those employed in off-highway vehicles, e.g., railroad locomotives, mining vehicles and machinery, etc. It will be described with particular reference thereto. However, it is to be appreciated that the present invention is also amenable to other internal combustion engines and the like which employ lubrication systems for various applications, be it off-highway applications, on-highway applications, or otherwise.
Maintenance of engine lubricant quality is essential to the proper operation and long service life of an internal combustion engine. A responsibility of the engine operator or maintenance personnel is to periodically check the lubricant and, if needed, add an appropriate amount of fresh lubricant or change the lubricant entirely to maintain the lubricant in the engine at a desired quality level. As used herein, the term “fresh lubricant” includes a base lubricant (e.g., a natural oil, a synthetic oil, or the like) containing desired quantities and types of lubricant additives or adjuncts.
In general, the quality of the lubricant in an engine degrades with engine use. Lubricant degradation occurs due to depletion of lubricant additives that perform specific functions such as control viscosity, reduce wear, increase lubricity, minimize deposits, prevent oxidation, and other desirable features. Lubricant degradation can also occur by the ingestion of foreign materials into the lubricant such as dirt from the surrounding environment, wear materials from the engines that occur as part of the natural operating process, and blow-by from the combustion process. Lubricant degradation can also occur due to a break-down of the base stock of the lubricant. In the extreme case fuel or water/coolant contamination of the lubricant can cause lubricant degradation.
Two ways of improving the quality of the engine lubricant is to periodically remove some or all of the engine lubricant and replace it with fresh lubricant. Also, in most cases filters are used to remove foreign materials above a certain size from the engine lubricant.
Various systems have been proposed for periodically removing a given quantity of lubricant from the engine and either storing the lubricant until it can properly be disposed of, or in the case of a diesel engine, optionally periodically injecting the lubricant into the fuel tank where the lubricant is mixed with the fuel and then burned in the engine along with the fuel. Also, it is generally known to provide such systems with automatic lubricant level sensing devices which maintain the proper level of lubricant in the engine.
In some systems, a given quantity of the engine lubricant is removed at preset time intervals based on engine usage factors. In others, small increments of engine lubricant are periodically removed and substantially simultaneously replaced with correspondingly small increments of fresh lubricant. In still others, a given amount of engine lubricant is periodically removed based on sensors that measure different operating variables of the engine such as the level, temperature and/or pressure of the lubricant within the engine, the number of engine starts or crank shaft revolutions, the length of time the engine has been in motion and at rest, engine temperature, fuel consumption, etc. See, e.g., U.S. Pat. No. 5,749,339 to Graham, et al.
However, many previously developed lubrication systems are characterized by certain limitations and/or drawbacks. For example, systems that employ a set periodic maintenance schedule can have less than optimized engine operation time due to unnecessary maintenance down time. Likewise, systems that employ a maintenance schedule based on engine operation and/or operating conditions can also experience the same problem insomuch as these factors, while perhaps indicative, do not directly reflect the lubricant quality. Therefore, estimates of the lubricant's amount of degradation are imprecise and maintenance or lubricant exchanges may be prematurely scheduled. In addition to unnecessary down time, prematurely scheduled maintenance or lubricant exchanges result in unnecessary lubricant consumption. On the other hand, late maintenance or lubrication exchange is even less desirable insomuch as it can result in unnecessary engine wear, reducing engine life, and possible engine failure consequently, the previously developed lubrication systems tended to error on the side of premature maintenance and/or premature lubrication exchange.
Moreover, the previously developed systems did not account for or detect conditions which may prompt lubricant failure, such as, e.g., incipient failure detection (IFD) denoted by significant water/coolant contamination and/or fuel contamination of the lubricant. Preset maintenance schedules and maintenance schedules based on engine operation and/or operating conditions do not anticipate lubricant failure due to unexpected contamination.
Accordingly, there is a need for a system that more effectively determines the condition and thus the quality of the engine lubricant, such that when the quality of the engine lubricant degrades a predetermined amount or incipient failure is detected, appropriate corrective or otherwise responsive actions may be taken.
The present invention contemplates a new continuous on-board diagnostic lubricant monitoring system and method which at least partially overcomes the above-referenced problems and others.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a method of monitoring a lubricant is provided. The method includes the steps of measuring the lubricant's temperature, and measuring the lubricant's permittivity. After temperature dependance in the permittivity has been compensated for, it is determined if the lubricant has been contaminated by water or other coolant.
In accordance with a more limited aspect of the present invention, the method also includes determining a rate of change of the lubricant's permittivity for a first period of time, and determining a rate of change of the lubricant's temperature for a second period of time. The lubricant is then determined to be contaminated by a coolant if the rate of change of the lubricant's permittivity for the first period of time is greater than a first threshold, and an absolute value of the rate of change of the lubricant's temperature for the second period of time is less than a second threshold.
In accordance with a more limited aspect of the present invention, the first and second periods of time are the same.
In accordance with a more limited aspect of the present invention, the method also includes determining a rate of change of the lubricant's temperature for a third period of time, where the third period of time is greater than the first and second periods of time. In this case, for a determination to be made that the lubricant is contaminated by a coolant, it has to also be found that the rate of change of the lubricant's temperature for the third period of time is less than a third threshold.
In accordance with a more limited aspect of the present invention, the method also includes selecting a minimum temperature from those used to determine the rate of change of the lubricant's temperature for the second time period. In this case, for a determination to be made that the lubricant is contaminated by a coolant, it has to also be found that the minimum temperature is greater than a threshold temperature.
In accordance with another aspect of the present invention, a method of monitoring a lubricant includes obtaining, over time, permittivity data from measured permittivity values of the lubricant. Based on changes in the permittivity data over time, a rate of degradation of the lubricant's quality is determined, and an amount of time until the lubricant reaches a set degraded quality level is further determined.
In accordance w
Dayal Bhupinder Singh
Melnyk Michael Charles
Van Mullekom Jennifer H.
Esposito Michael F.
Gilbert Teresan W.
McCall Eric S.
The Lubrizol Corporation
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