# Patent

## Title
Automatic engine oil life determination with a factor for degradation based on an initial volume of oil

## Abstract

A method is provided for determining remaining oil life prior to an oil change in an internal combustion engine that has a sump and uses a body of oil. The method includes transferring the body of oil to the engine and determining a volume of the transferred body of oil. The method also includes determining degradation of the determined volume of oil in response to oxidation and/or decomposition. The method additionally includes determining the remaining oil life based on the determined volume and degradation of the transferred body of oil. Furthermore, the method includes activating an oil change indicator when the remaining oil life reaches a predetermined level. A system for determining a number of engine revolutions permitted on a volume of oil is also disclosed.

## Background
TECHNICAL FIELD
The present invention relates to a system for automatic engine oil life determination with a factor for degradation based on an initial volume of oil.
BACKGROUND
In internal combustion engines, oil is typically used for lubrication, cleaning, inhibiting corrosion, to improve sealing, and to cool the engine by carrying heat away from the moving parts. Engine oils are generally derived from petroleum-based and non-petroleum synthesized chemical compounds. Modern engine oils are mainly blended by using base oil composed of hydrocarbons and other chemical additives for a variety of specific applications. Over the course of oil's service life, engine oil frequently becomes contaminated with foreign particles and soluble contaminants, and its chemical properties become degraded due to oxidation and nitration. A common effect of such contamination and degradation is that the oil may lose its capability to fully protect the engine, thus necessitating the used oil to be changed or replaced with clean, new oil.
Engine oil is generally changed based on time in service, or based on a distance the engine's host vehicle has traveled. Actual operating conditions of the vehicle and hours of engine operation are some of the more commonly used factors in deciding when to change the engine oil. Time-based intervals account for shorter trips where fewer miles are driven, while building up more contaminants. During such shorter trips, the oil may often not achieve full operating temperature long enough to burn off condensation, excess fuel, and other contamination that may lead to “sludge”, “varnish”, or other harmful deposits.
To aid with timely oil changes, modern engines often include oil life monitoring systems to estimate the oil's condition based on factors which typically cause degradation, such as engine speed and oil or coolant temperature. When an engine employing an oil life monitoring system is used in a vehicle, such a vehicle's total distance traveled since the last oil change may be an additional factor in deciding on the appropriate time for an oil change.
SUMMARY
A method is disclosed herein for determining remaining oil life prior to an oil change in an internal combustion engine that has a sump and uses a body of oil. The method includes transferring the body of oil to the engine and determining a volume of the transferred body of oil. The method also includes determining degradation of the determined volume of oil in response to contaminants, oxidation, and nitration. The method additionally includes determining the remaining oil life based on the determined volume and degradation of the transferred body of oil. Furthermore, the method includes activating an oil change indicator when the remaining oil life reaches a predetermined level.
The method may additionally include resetting the oil change indicator to represent 100% of oil life remaining following the oil change. At least one of the acts of determining a volume of the transferred body of oil, determining a degradation of the determined volume of oil, determining the remaining oil life, and activating and resetting the oil change indicator may be accomplished via a controller arranged relative to the engine.
The act of determining a volume of the transferred body of oil may include determining a level of oil in the sump. Such determining a level of oil in the sump may be accomplished via a sensor arranged on the engine.
The act of determining the remaining oil life may include determining a number of revolutions for each combustion event of the engine. Such determining the remaining oil life may further include determining a number of combustion events permitted using the determined volume of the transferred body of oil.
A system for determining the remaining oil life permitted on a volume of oil is also disclosed.
The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic illustration of an engine oil life monitoring system; and
FIG. 2 is a flow chart illustrating a method for determining a number of engine revolutions permitted on a volume of oil in an internal combustion engine.



DETAILED DESCRIPTION
Referring to the drawings wherein like reference numbers correspond to like or similar components throughout the several figures, FIG. 1 illustrates an automatic oil life system 5. Oil life system 5 is configured for determining remaining effective or useful life of oil utilized in an internal combustion engine prior to an oil change. The determining of the remaining oil life by oil life system 5 includes determining a number of permitted engine revolutions on a specific volume of oil.
Automatic oil life system 5 includes an internal combustion engine which is represented schematically and denoted by numeral 10. Engine 10 includes an engine block 12. Block 12 houses engine internal components such as a crankshaft 14, reciprocating pistons 16, and connecting rods 18. Pistons 16 are attached to crankshaft 14 via rods 18 to transfer the force of combustion to the crankshaft and thereby rotate the engine 10. Rotation of engine 10, which is typically measured in terms of revolutions per minute (RPM), is denoted by an arrow 19. Each connection between the respective pistons 16 and rods 18, and between the rods and crankshaft 14, includes an appropriate bearing (not shown) for smooth and reliable rotation.
Engine 10 also includes an oil pan or sump 20. Sump 20 is arranged on engine 10 and is attached to block 12 for holding a body of oil 22. Body of oil 22 is employed within engine 10 for lubricating the engine's moving parts, such as bearings (not shown), pistons 16 and rods 18, and for other functions such as cooling the engine by carrying heat generated by friction and combustion away from the moving parts. Body of oil 22 additionally functions to remove contaminants from engine 10. Engine 10 additionally includes an oil filter 26 specifically configured to trap various foreign particles that the oil may collect while in service. In order to not restrict oil flow, filter 26 is generally capable of trapping particles down to only a certain size, and may thus fail to capture smaller contaminants. The body of oil 22 may also absorb soluble contaminants that are not removed by filter 26. Therefore, over time, body of oil 22 becomes chemically degraded due to oxidation and nitration, as well as contaminated with foreign materials, thus becoming less effective in its protection of engine 10, and necessitating the oil to be changed. Sump 20 includes a removable plug 24, which may be configured as a threadable fastener, for permitting body of oil 22 to be drained from the sump during an oil change.
Automatic oil life system 5 also includes a controller 28, and may include a sensor 30 (as shown) that is configured to sense a level or height of the body of oil 22. Controller 28 may be a central processor configured to regulate operation of engine 10 or a dedicated unit programmed to solely operate the automatic oil life system. Controller 28 is in communication with sensor 30, which is arranged on the engine 10 relative to the sump 20. Sensor 30 is at least partially immersed in body of oil 22 and is configured to selectively sense a level of the oil present in sump 20. Sensor 30 may be configured to sense the level of body of oil 22 either while engine 10 is shut-off, or dynamically, i.e., while the engine is running, and communicate such data to controller 28. When engine 10 is shut-off, sensor 30 may facilitate the determination of the entire volume of the oil present in the engine. On the other hand, when engine 10 is running, and a portion of the oil is in circulation throughout the engine, sensor 30 may facilitate determination of solely the volume of oil remaining in sump 20. Controller 28 receives data from sensor 30, and determines an appropriate time or instance for body of oil 22 to be changed, i.e., replaced with fresh oil.
The appropriate allowed number of engine revolutions before changing body of oil 22 is determined according to a mathematical relationship or algorithm R(Rev)=ε×K(Oil)×K(Eng)×V×e−kV, which is denoted by numeral 33. Mathematical relationship 33 is programmed into controller 28. R(Rev) represents a total number of engine revolutions permitted on a specific volume and quality of the body of oil 22. R(Rev) may also be representative of a predetermined level of effective or useful life remaining in the body of oil 22 prior to necessitating an oil change. K(Oil) represents a total number of allowed combustion events of engine 10 per liter of the body of oil 22. Total number of allowed combustion events per liter of the body of oil 22, K(Oil), is an input variable in relationship 33. Factor “ε” is an empirically derived or predetermined efficiency constant which modifies K(Oil) to account for effects of oxidation and/or decomposition on the body of oil 22.
K(Eng) represents a number of revolutions of engine 10 for each combustion event of the engine, and V represents a volume in liters of the body of oil 22 present in sump 20. Factor “e−kV” is an empirically derived or predetermined exponential function which accounts for an effectively reducing, i.e., dropping, value of V due to the oxidation and degradation of body of oil 22 that results from the oil being exposed to elevated temperature inside engine 10. In the superscript “−kV”, factor “−k” represents an empirically derived constant that corresponds to reaction of body of oil 22 to oxidation and/or decomposition effects in sump 20. Accordingly, such negative change in V is accounted for, and thereby affects a proportional negative change in R(Rev).
K(Eng) is a mathematical constant, the value of which depends on the actual engine configuration, with a specific number of cylinders. For example, in a six-cylinder, four-stroke engine, two complete engine revolutions are required for each cylinder to experience a single combustion event, i.e., K(Eng) is equal to 2 divided by 6 in the same example, and is therefore equal to a value of 1⁄3. V is a volume in liters of the body of oil 22 determined by the rated oil capacity of engine 10, which is typically indicated at the “full” mark on an oil level indicator or dipstick (not shown), or based on the oil level in sump 20 sensed by sensor 30 after the oil change.
Subsequent to the determination of R(Rev) based on relationship 33, controller 28 executes a control action, such as activating or triggering an oil change indicator 34. Oil change indicator 34 is configured to signal to an operator of the engine or of the host vehicle when the number of engine revolutions permitted on the determined quality and volume of the body of oil 22, R(Rev), has been reached. The oil life indicator 34 may also display the percentage of oil life remaining. In order to assure that the operator is reliably notified when the time for oil change has arrived, oil change indicator 34 may be positioned on an instrument panel, inside the vehicle's passenger compartment. Oil change indicator 34 may be triggered immediately upon the determination that R(Rev) has been reached, or solely after R(Rev) has been reached when the engine is started and/or shut off. Following the oil change, oil change indicator 34 is reset to represent 100% oil life remaining, and the determination of R(Rev) on a fresh body of oil may commence.
A method 40 for determining remaining oil life prior to an oil change is shown in FIG. 2, and described below with reference to the structure shown in FIG. 1. Method 40 commences in frame 42 with transferring body of oil 22 to sump 20. Following frame 42, the method proceeds to frame 44, where it includes determining volume of oil V of the transferred body of oil 22, as described above with respect to FIG. 1. After frame 44, the method advances to frame 46, where it includes determining the degradation of the volume V of the body of oil 22 in response to oxidation and/or decomposition.
The degradation of the volume V of the body of oil 22 may be determined via the controller 28 in part by employing the predetermined efficiency constant “ε” to modify factor K(Oil). The degradation of the volume V may be further assessed by the controller 28 employing the predetermined constant “−k” to calculate the factor “e−kV”, to thereby account for the body of oil 22 being exposed to varying temperature inside engine 10. Following frame 46, the method proceeds to frame 48.
In frame 48, the method includes determining when the remaining oil life reaches a predetermined level. The predetermined level of remaining oil life may be established according to the number of engine revolutions R(Rev), wherein R(Rev) is based on the predetermined efficiency constant “ε” and the derived function “e−kV” being employed in the relationship 33. Following frame 48, the method advances to frame 50, where it includes executing a control action, such as activating the oil change indicator 34, to signal to an operator of engine 10 or of the vehicle where the engine resides when the remaining oil life reaches the predetermined level. A continuous reading of the percentage of remaining useful oil life may also be provided.
While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.

## Claims

1. A method for determining remaining oil life prior to an oil change in an internal combustion engine that uses a body of oil, the method comprising:
transferring the body of oil to a sump of the engine;
determining a volume of the body of oil transferred to the sump;
determining a degradation of the determined volume of the body of oil in response to at least one of oxidation and decomposition, wherein the determined degradation is used to determine a mathematical exponential function;
determining the remaining oil life based on the determined volume and degradation of the body of oil, wherein the remaining oil life is determined via a mathematical relationship employing the exponential function to proportionally reduce the determined remaining oil life; and
activating an oil change indicator when the remaining oil life reaches a predetermined level.

2. The method of claim 1, further comprising resetting the oil change indicator to represent 100% of oil life remaining following the oil change.

3. The method of claim 2, wherein at least one of said determining a volume of the body of oil transferred to the sump, said determining a degradation of the determined volume of oil, said determining the remaining oil life, and said activating and said resetting the oil change indicator is accomplished via a controller arranged relative to the engine.

4. The method of claim 1, wherein said determining a volume of the body of oil transferred to the sump includes determining a level of oil in the sump.

5. The method of claim 4, wherein said determining a level of oil in the sump is accomplished via a sensor arranged on the engine.

6. The method of claim 1, wherein said determining the remaining oil life includes determining a number of revolutions for each combustion event of the engine, and further includes determining a number of combustion events permitted using the determined volume of the body of oil transferred to the sump and the determined volume of a body of oil remaining in the sump from the transferred body of oil when the engine is running.

7. A system for determining remaining oil life prior to an oil change in an internal combustion engine that uses a body of oil, the system comprising:
an oil sump arranged on the engine to accept the body of oil;
a sensor arranged on the engine and configured to generate a signal indicative of a volume of the body of oil in the sump; and
a controller in communication with the sensor and programmed to determine the remaining oil life based on the generated signal and a determined degradation of the body of oil in the sump;
wherein:
the degradation of the determined volume of the body of oil is determined in response to at least one of oxidation and decomposition of the body of oil in the sump;
the determined degradation is used to determine a mathematical exponential function; and

the remaining oil life is determined via a mathematical relationship employing the exponential function to proportionally reduce the determined remaining oil life.

8. The system of claim 7, further comprising an oil change indicator, wherein the controller is configured to activate the oil change indicator when the remaining oil life reaches a predetermined level.

9. The system of claim 8, wherein the oil change indicator is reset to represent 100% of oil life remaining following the oil change.

10. The system of claim 7, wherein the controller is programmed with a number of revolutions for each combustion event of the engine, and the controller additionally determines the remaining oil life based on the number of revolutions for each combustion event of the engine.

11. The system of claim 7, wherein the signal indicative of a volume of the body of oil in the sump is indicative of a level of the body of oil in the sump, and the controller determines the volume based on the level.

12. The system of claim 7, wherein the controller is programmed with a number of combustion events permitted per the volume of the body of oil in the sump, and the controller additionally determines the remaining oil life based on the number of combustion events.

13. A method for determining a number of engine revolutions permitted prior to an oil change in an internal combustion engine using a body of oil and having an oil sump, the method comprising:
transferring the body of oil to the sump;
determining a volume of the body of oil transferred to the sump;
determining a degradation of the determined volume of the body of oil in response to at least one of oxidation and decomposition, wherein the determined degradation is used to determine a mathematical exponential function;
determining the number of engine revolutions based on the determined volume and degradation of the body of oil, wherein the number of engine revolutions is determined via a mathematical relationship employing the exponential function to proportionally reduce the determined number of engine revolutions; and
activating an oil change indicator when the number of engine revolutions reaches a predetermined level.

14. The method of claim 13, further comprising resetting the oil change indicator to represent 100% of oil life remaining following the oil change.

15. The method of claim 14, wherein at least one of said determining a volume of the body of oil transferred to the sump, determining a degradation of the determined volume of oil in response to oxidation, said determining a number of engine revolutions, and said activating and said resetting the oil change indicator is accomplished via a controller arranged relative to the engine.

16. The method of claim 13, wherein said determining a volume of the transferred body of oil includes determining a level of oil in the sump.

17. The method of claim 16, wherein said determining a level of oil in the sump is accomplished via a sensor arranged on the engine.

18. The method of claim 13, wherein said determining a number of engine revolutions includes determining a number of revolutions for each combustion event of the engine, and further includes determining a number of combustion events permitted using the determined volume of the body of oil.