Method of monitoring engine lubricant condition

• US 6,513,367 B2
• Filed: 02/22/2001
• Issued: 02/04/2003
• Est. Priority Date: 02/22/2001
• Status: Expired due to Fees

• Current Assignee: Jeffrey P. Calfa
• Original Assignee: International Truck Intellectual Property Co. LLC (Volkswagen AG)
• Inventors: Larson, Gerald L., Calstrom, Kevin R., Bondarowicz, Frank
• Primary Examiner(s): Willliams, Hezron
• Assistant Examiner(s): P, J L
• Application Number:
  US09/791,434
• Publication Number:
  US 20020112529A1
• Time in Patent Office: 712 Days
• Field of Search: 73/530.5, 73/617.6, 73/32.R, 123/376, 123/463, 123/452, 324/672, 324/663, 508/545, 508/294
• US Class Current: 73/53.05
• CPC Class Codes: F01M 2011/14 for indicating the necessity to change the oil
• CPC Class Codes: G01N 33/2888 Lubricating oil characteristics, e.g. deterioration lubricating properties G01N33/30

Abstract

A method for generating indicators relating to the condition of lubricating oil in an internal combustion engine. A set of variables relating to operation of the internal combustion engine serve as proxy variables for brake mean effective pressure developed by the internal combustion engine. Operation of an engine is monitored to develop values for the proxy variables. Soot being added to the lubricating oil from the developed values and accumulated to provide an estimate of total soot in the lubricating oil. Lubricating oil temperature is periodically monitored and a history of the lubricating oil temperature measurements is kept to allow generation therefrom of an estimate of shear of the lubricating oil. Accumulated estimate of soot is kept as a distance remaining until the lubricating oil becomes unsuitable for continued use in the internal combustion engine. Similarly, estimated shear is expressed as a distance until the lubricating oil is to be replaced. Additional factors may be monitored and similarly used to determine the distance until an oil change is required, including the dielectric coefficient of the lubricating oil, temperature history of the oil and total cylinder firing events.

Claims

1. A method of determining change intervals for lubricating oil in an internal combustion engine having at least a first cylinder, comprising the steps of:

monitoring fuel flow, engine speed, engine temperature, and piston timing relative to top dead center in each cylinder;

determining engine load from fuel flow and engine speed;

developing adjustment coefficients based on engine load, temperature and piston timing;

estimating soot being added to the lubricating oil from each cylinder event by multiplying a fuel injection quantity for the cylinder event by the adjustment coefficients;

accumulating an estimate of total soot in the lubricating oil by summing the estimated soot figures for each cylinder event; and

relating the estimate of total soot to a soot oil change interval.

2. A method as claimed in claim 1, comprising the further steps of:

periodically measuring lubricating oil temperature;

keeping a history of the lubricating oil temperature measurements generating from the history an estimate of oxidation of the lubricating oil; and

relating the history of oil temperature measurements as a proxy for oxidation of the oil to an oxidation oil change interval.

3. A method as claimed in claim 2, further comprising:

comparing the soot oil change interval, the oxidation oil change interval and the shear oil change interval to determine the shortest; and

indicating the shortest oil change interval to a vehicle operator.

4. A method as claimed in claim 3, further comprising:

providing a dielectric sensor within an engine lubrication system where the dielectric sensor comes into contact with the lubricating oil allowing measurements of dielectric coefficient lubricating oil;

periodically taking concurrent measurements of dielectric coefficient and temperature of the lubricating oil;

adjusting the measurement of the dielectric coefficient with the measurement of lubricating oil temperature;

maintaining an average for recent, temperature adjusted measurements of dielectric coefficient of the lubricating oil; and

comparing each new measurement of the dielectric coefficient, adjusted for lubricating oil temperature, with the average for recent measurements.

5. A method as claimed in claim 4, wherein the step of comparing the new measurement of dielectric coefficient with the average of recent measurements includes determining if the new measurement falls outside a band of expected values around the average of recent measurements.

6. A method as claimed in claim 5, wherein responsive to the new measurement exceeding the expected band, indicating that the lubricating oil requires replacement.

7. A method as claimed in claim 5, wherein responsive to the new measurement falling below the expected band, resetting initial variables and, during a minimum cycle period, updating the average of measurements of dielectric coefficient of the lubricating oil.

8. A method as claimed in claim 7, wherein the new lubricating oil routine comprises the steps of:

resetting initial variables and, during a minimum cycle period, updating the weigthed record of dielectric coefficients.

9. A method for generating indicators relating to the condition of engine lubricating oil in an internal combustion engine, the method comprising the steps of:

monitoring cylinder events as proxy variable for shear of the engine lubricating oil;

generating an estimate of soot added to engine oil from a fuel injection amount, fuel flow, coolant temperature and fuel injection timing relative to piston position;

accumulating the estimates of soot introduced to the engine lubricating oil;

periodically measuring lubricating oil temperature; and

keeping a history of the lubricating oil temperature measurements as a proxy for oxidation of the engine lubricating oil.

10. A method as claimed in claim 9, further comprising:

relating the accumulated soot to a distance interval until the lubricating oil becomes unsuitable for continued use in the internal combustion engine on account of the soot; and

relating the accumulated number of cylinder events to a distance interval until the lubricating oil becomes unsuitable for continued use in the internal combustion engine on account of shear; and

relating the history of lubricating oil temperature to distance remaining until the lubricating oil becomes unsuitable for continued use on account of oxidation.

11. A method as claimed in claim 10, further comprising:

periodically measuring the dielectric coefficient of the lubricating oil;

correlating the measurements of the dielectric coefficient with measurements of the lubricating oil temperature to develop a set of expected values based on recent measurements of dielectric coefficient as a function of lubricating oil temperature; and

periodically comparing a new measurement of the dielectric coefficient, adjusted for lubricating oil temperature, with the set of expected values.

12. A method as claimed in claim 11, wherein the step of comparing the new measurement of dielectric coefficient with the set of expected values comprises determining if the new measurement is within a band around the set of expected values.

13. A method as claimed in claim 12, further comprising indicating that the lubricating oil requires replacement responsive to a new measurement exceeding an upper limit of the expected band.

14. A method as claimed in claim 12, wherein responsive to a new measurement falling below the expected band, executing a new lubricating oil routine.