Method of evaluating the wear of engine oil taking into account the addition of fresh oil

• US 6,776,024 B2
• Filed: 12/06/2002
• Issued: 08/17/2004
• Est. Priority Date: 03/07/2000
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Jakoby, Bernhard
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): CYGAN, MICHAEL T
• Application Number:
  US10/221,091
• Publication Number:
  US 20030172722A1
• Time in Patent Office: 620 Days
• Field of Search: 73/10, 73/530.5, 73/540.1, 73/540.2, 702/50
• US Class Current: 73/10
• CPC Class Codes: F01M 2011/14 for indicating the necessity to change the oil
• CPC Class Codes: G01N 11/00 Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
• CPC Class Codes: G01N 33/2888 Lubricating oil characteristics, e.g. deterioration lubricating properties G01N33/30

Abstract

A method of evaluating engine oil wear on the basis of viscosity measurement, accounting for the addition of fresh oil. Using an oil viscosity sensor, an amount of fresh oil added is detected, then the oil viscosity sensor determines a viscosity of the oil mixture of the engine oil and fresh oil. A quantity of fresh oil added is determined in the electronic analyzer from a difference between the old oil level, i.e., the oil volume, and the new oil level. The viscosity of the fresh oil is determined from the viscosity of the old engine oil immediately before the point in time of the addition of fresh oil and from the viscosity after the addition. A hypothetical initial viscosity is calculated as a new corrected reference value from the known value of the viscosity of the old engine oil in the new condition, the quantity of the engine oil still present at the point in time of the addition, the calculated viscosity of the fresh oil and the calculated quantity of the fresh oil.

Claims

1. A method of evaluating wear in engine oil based on viscosity measurements, accounting for an addition of fresh oil to aged engine oil using an oil viscosity sensor, an oil level sensor and a connected electronic analyzer having a display device, and determining an aging of the aged engine oil and determining an oil change interval recommendation resulting therefrom as a reference value by evaluating a change in a prevailing oil viscosity at at least one temperature, in comparison with a viscosity of the fresh oil added at a last oil change, the method comprising:

detecting a quantity of oil used in the addition of the fresh oil using the oil level sensor;

determining a viscosity of an oil mixture of the aged engine oil and the fresh oil together with a temperature using the oil viscosity sensor at at least one temperature;

determining the quantity of the fresh oil added, using the electronic analyzer, from a difference between one of an old oil level and oil volume, and one of a new oil level and oil volume;

determining a viscosity of the fresh oil from a viscosity of the aged engine oil immediately before and immediately after the addition of the fresh oil; and

calculating a hypothetical initial viscosity as a new corrected reference value from an initial viscosity of the aged engine oil when new, the oil volume still present at a point in time of the addition, a determined viscosity of the fresh oil, and a determined quantity of fresh oil.

2. The method of claim 1, further comprising:

determining a viscosity limit value from the viscosity of the aged engine oil when new by multiplying the initial viscosity by a factor of an admissible increase in viscosity, so that a display of an end of an oil change interval by the display device is triggered when the viscosity limit value is exceeded by the viscosity of the oil mixture measured at a given time at a corresponding temperature value; and

obtaining a new limit value from the hypothetical initial viscosity, when adding fresh oil, by multiplying the initial viscosity by the factor.

3. The method of claim 2, wherein the factor has a value greater than 1.

4. The method of claim 2, wherein a mixing rule is used to determine at least one of the calculated viscosity of the fresh oil and the hypothetical initial viscosity of the oil mixture when new as the new corrected reference value.

5. The method of claim 2, wherein at least one indirect influencing factor on the aging of the engine oil is accounted for in the determining the oil change interval.

6. The method of claim 5, wherein the at least one indirect influencing factor includes an oil heating temperature gradient.

7. The method of claim 5, wherein the at least one indirect influencing factor includes at least one of the number of kilometers driven and the number of hours of operation since the last oil change.

8. The method of claim 5, wherein the at least one indirect influencing factor includes at least one of a rotational speed of the engine and an oil temperature characteristic.

9. The method of claim 5, wherein the at least one indirect influencing factor includes a dielectric constant of the engine oil.

10. The method of claim 5, wherein the at least one indirect influencing factor includes a conductivity of the engine oil.

11. The method of in claim 5, wherein the at least one indirect influencing factor includes one of a frequency of cold starts and a load on the vehicle.

12. The method of claim 1, wherein the new corrected reference value is formed by accounting for an additional measured relationship as a reference characteristic.

13. The method of claim 12, wherein the reference characteristic includes a viscosity/temperature characteristic, wherein unmeasured ranges are supplemented by at least one of interpolation and extrapolation.